USRE38084E1 - Projector - Google Patents

Abstract

An output light from an light source lamp unit8in a projection-type display apparatus illuminates liquid-crystal light valves925R,925G and925B for three colors via an integrator optical system923.A superimposing lens930that is a component of the integrator optical system923as a uniform illumination optical system is arranged such that the mounting position of the superimposing lens930is fine-adjustable in a direction orthogonal to an optical axis1a. By fine-adjusting the mounting position of the superimposing lens930,the position of an illumination area B is adjusted such that the illumination area includes the image forming area A of the liquid-crystal light valve. It is not necessary to assure a wide margin around the image forming area A to cover the offset of the position of the illumination area B. As a result, the utilization of illumination light is heightened and a bright projected image results.

Description

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a projection-type display apparatus that modulates an output light beam from a light source in response to a video signal using a modulating device such as a liquid-crystal light valve or the like and enlarges and projects the modulated light beam through a projection lens onto a screen. More particularly, the present invention relates to a projection-type display apparatus that illuminates an image forming area of the modulating device such as a liquid-crystal light valve.

2. Description of Related Art

Japanese Unexamined Patent Publication 3-111806 discloses a projection-type display apparatus that forms a modulated light beam in response to a video signal using a liquid-crystal light valve and enlarges and projects the modulated light beam onto a screen. As shown in FIG. 13, the projection-type display apparatus includes an integratoroptical system923 having twolens plates921 and922, for uniformly illuminating the image forming area of a liquid-crystal valve925, as a modulating device, with light from a light source.

The single light beam emitted from a lightsource lamp unit8 is split into a plurality of intermediate light beams bylenses921a constituting thefirst lens plate921, and is superimposed on the liquid-crystal light valve925 throughlenses922a constituting thesecond lens plate922.

In this projection-type display apparatus, the brightness of an image projected onto the screen will drop or the projected image suffers an outlining shadow if the image forming area of the liquid-crystal light valve925 is not accurately illuminated. To cope with this problem, as shown in FIG. 14, a certain margin M is assured around the image forming area A of the liquid-crystal light valve925 in view of the positioning accuracies of the liquid-crystal light valve925 and thelens plates921,922 constituting the integratoroptical system923, the positional errors in the focal points of thelenses921a,922a of the lens plates and the positioning accuracies of the remaining optical systems disposed along the optical axis.

More particularly, the image forming area A is sized to be distinctly smaller than an illumination area B by the output light from the light source. Even if the illumination area B is offset vertically upward or downward, or horizontally leftward or rightward depending on the overall positioning accuracy of the above components, the image forming area A is designed to be kept within the illumination area B. This avoids the outlining shadow around the projected image and drop in brightness of the projected image. To cope with a large quantity of positional error of the components, the margin M is simply widened.

To increase the brightness of a projected image, the efficiency in the utilization of the light that illuminates the liquid-crystal light valve925 needs to be increased. If the margin M is enlarged to accommodate errors of the components, the efficiency in the utilization of light drops, thereby dimming the projected image. Thus, the width of the margin formed around the image forming area of the liquid-crystal light valve is preferably narrow. A narrow margin in turn offsets the illumination area from the image forming area of the liquid-crystal light valve, possibly presenting a shadow outlining the projected image.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a projection-type display apparatus that offers an increased image brightness without any shadow around a projected image while presenting a narrow margin around the image forming area of a liquid-crystal light valve.

A first projection-type display apparatus of the present invention may include a light source, a modulating device for modulating a light beam emitted by the light source and a projection device for enlarging and projecting the modulated light beam from the modulating device onto a projection area. An optical element may be disposed in an optical path between the light source. The modulating device may split the light beam emitted from the light source into a plurality of intermediate light beams. A superimposing device may also be provided for superimposing each of the slit intermediate light beams from the optical element on an image forming area of the modulating device. The mounting position of the superimposing device may be adjustable.

This may increase the efficiency in the utilization of illumination light that illuminates the modulating device, thereby brightening a projected image. Even when the margin around the image forming area of the modulating device is narrowed, the illumination area relative to the modulating device is fine-adjusted so that the image forming area is kept within the illumination area and the projected image is free from the outlining shadow attributed to any offset between the image forming area and the illumination area.

After components of the optical systems are mounted, the image forming area of the modulating device is illuminated by the optical element and the superimposing device. When the illumination area is offset from the image forming area of the modulating device, the superimposing device is fine-adjusted so that the image forming area of the modulating device is fully included within the illumination area. Taking into consideration the offset between the illumination area and the image forming area, attributed to the positioning error of the optical components, the margin formed around the outline of the image forming area of the modulating device is narrowed.

Since the mounting position of the superimposing device, which is an optical component chiefly determining the illumination area of the modulating device, may be fine-adjusted, the position of the illumination area of the modulating device is easily and efficiently adjusted. The adjustment of the position of the illumination area is thus performed taking into consideration the overall mounting error of optical components (optical elements) in front of the superimposing device (upstream of the superimposing device in the optical path).

Since the plurality of split intermediate light beams are finally superimposed on a single illumination area through the superimposing device and are then delivered, a constant-brightness polarized light beam with no illuminance variations is obtained as an illumination light even when an incident light beam has a large light intensity distribution in its cross section. A constant-brightness polarized light beam with no illuminance variations may be obtained as an illumination light when the incident light beam has a uniform light intensity, when the intermediate light beam cannot be separated into a p-polarized light and an s-polarized light beam because of spectral characteristics, or when the light intensity and spectral characteristics change in the course of aligning the polarization directions of both polarized light beams.

The projection-type display apparatus may present a particularly bright projected image that is uniform and bright on an entire display area or projection area.

A reflection device for bending an optical path may be disposed in the optical path extending from the light source to the modulating device. If an error is introduced in the mounting angle of the reflection device, the illumination area may be offset from the image forming area of the modulating device. The mounting angle of the reflection device is such that it is preferably adjustable relative to its incident optical axis.

The projection-type display apparatus may be applied to a projection-type display apparatus for projecting a color image. More particularly, it may be applied to a projection-type display apparatus including a color separating optical system for separating an output light from the superimposing device into color light beams, a plurality of modulating devices for modulating the color light beams separated by the color separating optical system, and a color synthesizing optical system for synthesizing the color light beams respectively modulated by the plurality of modulating device. The synthesized modulated light beam from the color synthesizing optical system may be enlarged and projected through the projection device to the projection area.

In the projection-type display apparatus for projecting a color image, a reflection device may be disposed in an optical path between the color separating optical system and at least one of the plurality of modulating devices. The illumination area may be offset depending on the mounting angle of the reflection device. The reflection device may be preferably adjustable in its mounting angle with respect to the incident optical axis.

The reflection device disposed closest to the modulating device remaining adjustable in its mounting angle is advantageous from the standpoint of assembling the apparatus and position adjusting the illumination area relative to the modulating device.

If the modulating device is a reflection type modulating device and the color separating optical system and the color synthesizing optical system are integrated into the same optical system, the optical path length is shortened to result in a compact-design projection-type display apparatus.

A second projection-type display apparatus of the present invention may include a light source, a first optical element for splitting a light beam from the light source into a plurality of intermediate light beams and a second optical element comprising a polarization conversion unit and a superimposing device for superimposing light beams output from the polarization conversion unit. The polarization conversion unit may be arranged in the vicinity of a position where the intermediate light beams are converged to separate each of the split intermediate light beams from the first optical element into a p-polarized light beam and an s-polarized light beam. The polarization conversion unit may further align the polarization direction of one of the p-polarized light beam and the s-polarized light beam with the polarization direction of the other of the p-polarized light beam and the s-polarized light beam and output the resulting light beams. A modulating device may modulate the light beams emitted from the second optical element and a projection device may enlarge and project the modulated light beams from the modulating device to a projection area. The mounting position of the superimposing device may be adjustable.

The polarization conversion unit may be additionally provided besides the arrangement according to the first aspect, and thus, the second projection-type display apparatus presents the advantage offered by the use of the polarization conversion unit in addition to the advantage presented by the first projection-type display apparatus. More particularly, with the polarization conversion unit, polarizing light beams are efficiently used without wasting both light beams to thereby result in a bright projected image.

A reflection device for bending an optical path may be disposed in the optical path extending from the light source to the modulating device. The second projection-type display apparatus may be used in a projection-type display apparatus for projecting a color image. The mounting angle of the reflection device disposed closest to the modulating device may be adjustable and the modulating device may be a reflection type modulating device. Thus, the same advantages offered by the first projection-type display apparatus are achieved.

To make the mounting position of the superimposing device adjustable in the first projection-type display apparatus, an adjusting mechanism may be provided. More particularly, a first adjusting mechanism may be provided for adjusting the mounting position of the superimposing device in a first direction that is orthogonal to an optical axis. A second adjusting mechanism may be provided for adjusting the mounting position of the superimposing device in a second direction that is orthogonal to both the optical axis and the first direction.

A base adjusting plate may be provided to realize such an adjusting mechanism. Further, a first adjusting plate slidably movable in the first direction relative to the base adjusting plate and a second adjusting plate slidably movable in the second direction relative to the first adjusting plate may also be provided. With this mechanism, the mounting position of the superimposing device may be independently adjusted in individual directions (i.e., in the first and second directions).

The mounting position of the superimposing device may be difficult to adjust if the first adjusting plate is offset in the second direction when the second adjusting plate is slid in the second direction or if the second adjusting plate is offset in the first direction when the first adjusting plate is slid in the first direction. For this reason, the adjusting mechanism preferably includes a first slip prevention mechanism for preventing the first adjusting plate from slipping in the second direction and a second slip preventing mechanism for preventing the second adjusting plate from slipping in the first direction. This solves some of the above problems and the mounting position of the superimposing device is easily and accurately adjusted. When the adjusting mechanism including the first and second adjusting plates is employed, the superimposing device may be fixed to the second adjusting plate.

In the second projection-type display apparatus an adjusting mechanism may be provided to make the mounting position of the superimposing device adjustable.

Other objects, advantages and salient features of the invention will become apparent from the following detailed description taken in conjunction with the annexed drawings, which disclose preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the following drawings in which like reference numerals refer to like elements and wherein:

FIG. 1 is an external view of the projection-type display apparatus of the present invention;

FIG.2(A) is a general plan view showing the internal structure of the projection-type display apparatus, and FIG.2(B) is a sectional view of the apparatus;

FIG. 3 is a plan view showing an optical unit and a projection lens unit;

FIG. 4 is a general view of the optical system to be assembled in the optical unit;

FIGS.5(A)-(D) show the relationship between an illumination area and a liquid-crystal light valve in an integrator optical system;

FIGS.6(A)-(C) show a lens mounting position adjusting mechanism;

FIGS.7(A) and (7B) are explanatory views showing the illumination areas of the integrator optical system by the reflection surface of the reflection device;

FIGS.8(A)-8(C) show the mechanism for fine-adjusting the mounting angle of the reflection mirror, FIG.8(A) is an explanatory view of a holder plate, FIG.8(B) is a plan view of the fine-adjustment mechanism, and FIG.8(C) is a cross-sectional view of the fine-adjustment mechanism;

FIG. 9 is a general plan view showing the optical system of another example of the projection-type display apparatus of the present invention;

FIG.10(A) is a perspective view showing a polarization separation unit array of FIG. 7, and FIG.10(B) is an explanatory view showing the separation process of a polarization light beam by the polarization separation unit array;

FIG. 11 is a general plan view showing the optical system of another example of the projection-type display apparatus of the present invention;

FIG. 12 is an explanatory view showing the operation of the reflection-type liquid-crystal device of FIG. 9;

FIG. 13 is a general view of the optical system of a typical projection-type display apparatus equipped with an integrator optical system; and

FIG. 14 is an explanatory view showing the relationship between an illumination area and an image forming area in a liquid-crystal light valve.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows an external view of the projection-type display apparatus of one embodiment of the present invention. The projection-type display apparatus1000 picks up red, blue and green color light beams from a light emitted from a light source and passes the light beams through an integrator optical system and a color separating optical system. The apparatus further guides each color light beam to a liquid-crystal light valve arranged correspondingly to a respective color, modulates it according to a color video signal, synthesizes the modulated light beams for the three colors through a color synthesizing optical system, and then enlarges and projects the synthesized color image onto a projection screen.

As shown in FIG. 1, the projection-type display apparatus1000 has a rectangular parallelopipedouter casing2. Theouter casing2 may include anupper case3, alower case4 and afront case5 that forms the front of the apparatus. Aprojection lens unit6 projects out of the center of thefront case5.

FIGS.2(A)-2(B) show the positional relationship of components inside theouter casing2 of the projection-type display apparatus1000. Apower supply unit7 is housed in the rear portion inside theouter casing2. A lightsource lamp unit8 is arranged in front of thepower supply unit7. Anoptical unit9 is also arranged in front. Theprojection lens unit6 is mounted with its base end portion positioned at the center front of theoptical unit9.

Aninterface board11 is disposed on one side of theoptical unit9 having an input/output interface circuit that extends from front to back in the casing. Avideo board12 having a video signal processing circuit extends in parallel with theinterface board11. Acontrol board13 for driving and controlling the apparatus is mounted above the lightsource lamp unit8 andoptical unit9.Loudspeakers14R,14L are respectively installed on the left-front and right-front corners in the apparatus.

Asuction fan15A for cooling is installed on the center of the top surface of theoptical unit9 and a circulatingfan15B for circulating cooling air is attached on the center of the underside of theoptical unit9. Furthermore, anexhaust fan16 is attached to the rear side of the lightsource lamp unit8 facing one side of the apparatus. Anauxiliary cooling fan17 is disposed on one side of thepower supply unit7 close to the rear ends of theboards11,12 for sucking cooling air from thesuction fan15A into thepower supply unit7.

A floppy disk drive unit (FDD)18 is disposed on top of thepower supply unit7 on the left-hand side of the apparatus.

FIG. 3 shows theoptical unit9 and theprojection lens unit6 dismounted from the casing. Theoptical unit9 has optical elements (except aprism unit910 constituting a color synthesizing device) interposed between upper and lower light guides901,902. The upperlight guide901 and lowerlight guide902 are, respectively, secured to theupper case3 andlower case4 using fixing screws. The upper and lower light guides901,902 are also secured to sides of theprism unit910 using fixing screws. Theprism unit910 is secured to the inside of adiecast head plate903 using fixing screws. The base section of theprojection lens unit6 is bolted to the front side of thehead plate903.

FIG. 4 shows an optical system assembled into theoptical unit9. The optical system of this embodiment includes adischarge lamp81, an element constituting the lightsource lamp unit8 and an integratoroptical system923 including afirst lens plate921 and asecond lens plate922 as uniform illumination optical elements. The optical system further includes a color separatingoptical system924 for separating a white light beam W emitted from the integratoroptical system923 into red, green and blue color light beams R, G, and B and three liquid-crystal light valves925R,925G, and925B for respectively modulating the color light beams. Theprism unit910 synthesizes modulated color light beams and theprojection lens unit6 enlarges and projects the synthesized light beam to the surface of ascreen100. Alight guide system927 guides the blue color light beam B out of the color light beams separated by the color separatingoptical system924 to a liquid-crystal light valve925B.

A halogen lamp, a metal halide lamp or a xenon lamp may be used as thedischarge lamp81. The uniform illuminationoptical system923 may be provided with areflection mirror931 that bends at a right angle the centraloptical axis1a of the output light from the integratoroptical system923 toward the front of the apparatus. The first andsecond lens plates921,922 are perpendicular to a superimposinglens930 with themirror931 located in between.

The output light from thedischarge lamp81 is reflected in the form of parallel light beams by thereflection surface821 of areflector82 and is directed to thefirst lens plate921. Then the light beams as a secondary light source image are directed to the incidence surface of each lens constituting thesecond lens plate922 and the secondary light source images are superimposed through the superimposinglens930 on objects to be illuminated. More particularly, the image forming areas of the liquid-crystal light valves925R,925G and925B are illuminated.

The color separatingoptical system924 may include a blue/green-reflectingdichroic mirror941, a green-reflectingdichroic mirror942, and a reflectingmirror943. The blue light beam B and the green light beam G contained in the white light beam W are first reflected at a right angle from the blue/green-reflectingdichroic mirror941 toward the green-reflectingmirror942.

The red light beam R passes through the blue/green-reflectingdichroic mirror941 and is reflected at a right angle from the reflectingmirror943 downstream thereof and is delivered toward theprism unit910 through thedelivery section944 for the red light beam. The green light beam G is reflected from themirror941 and is reflected at a right angle from the green-reflectingmirror942 and is delivered toward theprism unit910 through thedelivery section945 for the green light beam. The blue light beam B passing through themirror942 is delivered toward thelight guide system927 through thedelivery section946 for the blue light beam. In this embodiment, the distances from the delivery section of the white light beam of the integratoroptical system923 respectively to thedelivery sections944,945, and946 in the color separatingoptical system924 are set to be equal.

Converginglenses951,952 are respectively arranged on the exit sides of thedelivery sections944,945 for red and green light beams in the color separatingoptical system924. These color light beams from the respective delivery sections are therefore made parallel through the converginglenses951,952.

The red and green light beams R, G in their parallel form are respectively introduced into the liquid-crystal light valves925R,925G to be modulated. Image information is imparted to each color light beam. More particularly, these light valves are switching-controlled by the image information by a driving device (not shown) and the color light beams passing therethrough are thus modulated. Any known device may be used as the driving device. The blue light beam B on the other hand is guided to the liquid-crystal light valve925B through thelight guide system927, where it is equally modulated according to image information. The light valves in this embodiment may be the one that employs a polysilicon TFT as a switching element.

Thelight guide system927 may include a converginglens953, aninput reflecting mirror971, anoutput reflecting mirror972, anintermediate lens973 disposed between theinput reflecting mirror971 and theoutput reflecting mirror972 and a converginglens954 disposed in front of the liquid-crystal panel925B. Among the lengths of the optical paths of the color light beams from the delivery section for the white light beam in the integrator optical system to the respective liquid-crystal light valves925R,925G and925B, the length of the optical path of the blue light beam B is the longest and thus the blue light beam suffers a maximum loss. However, by arranging thelight guide system927 the light loss that the blue light beam suffers is restricted.

The color light beams modulated through the respective liquid-crystal light valves925R,925G, and925B are introduced into theprism unit910 to be synthesized. In this embodiment, a dichroic prism is used as the color synthesizing optical system. A color image is enlarged and projected through theprojection lens unit6 to thescreen100 at a predetermined position.

In this projection-type display apparatus1, the illumination area of the liquid-crystal light valve925 determined by the integratoroptical system923 is fine-adjusted vertically up or down and horizontally to the left or right relative to the image forming area of the liquid-crystal light valve shown in FIG.5.

FIG.5(A) illustrates the relationship between the illumination area of the liquid-crystal light valve925 determined by the integratoroptical system923 and the image forming area A of the liquid-crystal light valve925. In FIG.5(A), the projection area of thescreen100 is typically rectangular and the image forming area A of the liquid-crystal light valve925 is accordingly rectangular. The illumination area B (represented by phantom lines) determined by the integratoroptical system923 is likewise rectangular.

The image forming area A of the liquid-crystal light valve925 is sized to be distinctly smaller than the illumination area B. In other words, the display area A has a margin of a predetermined width. With the margin the image forming area A is continuously included within the illumination area B even if the illumination area B is offset in position because of the position errors of the first andsecond lens plates921,922 of the integratoroptical system923 and the superimposinglens930.

The superimposinglens930 may be fine-adjusted vertically and horizontally in a plane orthogonal to theoptical axis1a as shown by arrows using position adjusting mechanisms. For example, plate springs attached to the upper and lower light guides901,902 and position adjusting screws may be used as position adjusting mechanisms.

FIGS.6(A)-6(C) show an example of a mechanism for fine-adjusting the mounting position of the superimposinglens930 vertically and horizontally. FIG.6(A) shows the mechanism for fine-adjusting the mounting position of the superimposinglens930, viewed from the upstream side along the optical path. FIG.6(B) shows the mechanism viewed from the side of the upperlight guide901 and FIG.6(C) shows the mechanism viewed from its one side. A lens mountingposition adjusting mechanism700 is provided with alower base plate710, which in turn is bolted to the lowerlight guide902. A lens adjusting base plate (base adjusting plate)720 is secured to thelower base plate710 such that the lens adjustingbase plate720 is orthogonal to the optical path. The lensadjusting base plate720 has avertical wall721 and ahorizontal flange722 that horizontally extends from the center of the top edge of thevertical wall721 toward the upstream side along the optical path (+Z direction). Thevertical wall721 supports a lens vertical adjusting plate (first adjusting plate)730 in parallel therewith. The lensvertical adjusting plate730 hasbottom flanges731a,731b extending from its bottom edge toward an upstream side along the optical path and atop flange732 extending from its top edge toward the upstream side along the optical path. Thebottom flanges731a,731b of the lensvertical adjusting plate730 are supported by analignment spring735 at thelower base plate710 and thetop flange732 is pressed downward by an adjustingscrew736 attached to thetop flange722 of the lens adjustingbase plate720. By adjusting the screwed depth of the adjustingscrew736, the lensvertical adjusting plate730 is shifted vertically upward or downward (±Y directions) relative to the lens adjustingbase plate720.

The lensvertical adjusting plate730 has a pair ofslots734 in the Y direction and the lens adjustingbase plate720 has a pair ofprojections724 that are respectively received in theslots734 as a slip prevention mechanism that prevents the lensvertical adjusting plate730 from shifting leftward and rightward (in ±X directions) when the mounting position of the superimposinglens930 is adjusted vertically upward or downward (±Y directions) by using the adjustingscrew736.

The lensvertical adjusting plate730 supports a lens horizontal adjusting plate (second adjusting plate)740 in parallel therewith. The lensvertical adjusting plate730 has a pair of left-hand side and right-hand side flanges733a,733b extending toward the upstream side along the optical path while the lenshorizontal adjusting plate740 hasside flanges743a,743b respectively extending in parallel with theside flanges733a,733b. Theside flanges743a of the lenshorizontal adjusting plate740 is urged by analignment spring745 supported by theside flange733a toward theside flange743b while theside flange743b is pressed by an adjustingscrew746 attached to theside flange733b toward theside flange743a. By adjusting the screwed depth of the adjustingscrew746, the lenshorizontal adjusting plate740 is shifted horizontally to the left or to the right (in ±X directions) relative to the lensvertical adjusting plate730.

The lenshorizontal adjusting plate740 has a pair ofslots747 in the X direction and the lensvertical adjusting plate730 has a pair ofprojections737 that are respectively received in theslots747 as a slip prevention mechanism that prevents the lenshorizontal adjusting plate740 from shifting vertically upward and downward (in ±Y directions) when the mounting position of the superimposinglens930 is adjusted to the left or to the right (in ±X directions) by using the adjustingscrew746.

The superimposinglens930 is attached to the lenshorizontal adjusting plate740 such that it occupies the generally central portion of the lenshorizontal adjusting plate740. In this embodiment, the superimposinglens930 is supported at part of its top portion by a bracket and at its bottom portion at two points by plate springs752 fixed byscrews751. Each of the three plates, which are components constituting the lens mountingposition adjusting mechanism700, namely, the lens adjustingbase plate720, lensvertical adjusting plate730 and lenshorizontal adjusting plate740 is provided with an opening for guiding the light from the superimposinglens930 to the color separating optical system.

In the lens mountingposition adjusting mechanism700, the three plates (i.e., the lens adjustingbase plate720, lensvertical adjusting plate730 and lens horizontal adjusting plate740) are supported at four points, two on their top portion and two on their bottom portion, by U-shaped adjusting plate fixing springs755. For this reason, the mounting position of the superimposinglens930 is adjusted vertically upward or downward, and horizontally to the left or to the right with the lens mountingposition adjusting mechanism700 remaining fixed to the lowerlight guide902. The lensadjusting base plate720 and lenshorizontal adjusting plate740 are respectively provided withadhesive wells728,748 on their top portions. After the adjustment of the mounting position of the superimposinglens930 is complete, an adhesive is introduced into these wells through adhesive applyingports904a,904b (FIG. 3) formed in the upperlight guide901 to bond the three plates and thus prevent the superimposinglens930 from offsetting from its mounting position.

The mounting position of the superimposinglens930 is thus enabled to be fine-adjusted vertically upward or downward and horizontally to the left or to the right and when the illumination area B is horizontally offset from the image forming area A of the liquid-crystal light valve925 causing the image forming area A to be left partly unilluminated as shown in FIG.5(B), the superimposinglens930 is fine-adjusted in its position by tightening or loosening the adjusting screw764 to horizontally move the position of the illumination area until the image forming area A is correctly put in the illumination area B as shown in FIG.5(C). When the illumination area B is offset from the image forming area of the liquid-crystal light valve925 with the image forming area A left partly unilluminated, the superimposinglens930 is fine-adjusted in its mounting position vertically upward or downward by tightening or loosening the adjustingscrew736 to put the image forming area A correctly into the illumination area B in the same manner.

The fine-adjustment of the superimposinglens930 in the horizontal direction (±X direction) may be automatically or manually performed by measuring luminance in the periphery portion around the projected image formed by the liquid-crystal light valve925G and projected onto the screen. More particularly, in the condition shown in FIG.5(B), the illumination area B is offset leftward, the illuminance drops in the rightmost portion of the image forming area of the liquid-crystal light valve925G. To correct the offset of the illumination area B, the superimposinglens930 may be shifted in its mounting position horizontally to the left or to the right (±X direction) until illuminances P1 and P2 on the left-hand side and right-hand side of the image forming area A become constant. Since this method sets a predetermined constant value beforehand, a difficulty is presented when the light source is changed to the one with small light intensity.

If the superimposinglens930 is designed to shift horizontally in its mounting position to the left or to the right until luminances P1 and P2 on the left-hand side and right-hand side of the image forming area A become equal, the setting of the predetermined constant value is not required. Thus, this method works even when the light source is changed to one with small light intensity. Furthermore, if the superimposinglens930 is designed to horizontally shift in its mounting position to the left or to the right until the sum of luminances P1 and P2 on the left-hand side and right-hand side of the image forming area A is maximized, the predetermined setting of the constant value is not required either. Thus, this method also works even when the light source is changed to one with small light intensity.

Instead of the method of measuring illuminance in the periphery portion of the image forming area A on the liquid-crystal light valve925G, fine-adjustment of the superimposinglens930 in the horizontal direction (±X direction) may be automatically or manually performed by measuring luminance in the periphery portion around the projected image on thescreen100 with the liquid-crystal light valve925G set to allow the illumination light to transmit therethrough to form the image on thescreen100.

When thescreen100 is illuminated as shown in FIG.5(B), a projected image B′ fails to appear on the leftmost portion of the area A′ where the image would otherwise be projected as shown in FIG.5(D). Accordingly, illuminance drops in the leftmost portion. By measuring illuminances Q1 and Q2 on the left-hand side and right-hand side of the area A′ where the image is supposed to be projected, the superimposinglens930 is fine-adjusted in the same manner that fine-adjustment is performed by measuring illuminance on the liquid-crystal light valve925G. More particularly, thefirst lens plate921 is horizontally shifted in its mounting position to the left or to the right until illuminances Q1 and Q2 become a constant value, or thefirst lens plate921 is horizontally shifted in its mounting position to the left or to the right until illuminances Q1 and Q2 become equal, or thefirst lens plate921 is shifted in its mounting position horizontally to the left or to the right until the sum of illuminances Q1 and Q2 is maximized. As already described, thefirst lens plate921 is horizontally shifted in its mounting position to the left or to the right until illuminances Q1 and Q2 become equal or until the sum of illuminances Q1 and Q2 is maximized. Thus, fine-adjustment is carried out without any difficulty even when the light source is changed to one with small light intensity.

Fine-adjustment of the superimposinglens930 in the vertical direction (±Y direction) may be automatically or manually performed by measuring illuminances above and below the image forming area or the projected image. Like the horizontal fine-adjustment, vertical fine-adjustment is performed by vertically shifting thesecond lens plate922 in its mounting position upward or downward until illuminances at two points become a constant value. Alternatively, thesecond lens plate922 is vertically shifted in its mounting position upward or downward until the illuminances at two points become equal to each other or until the sum of the illuminances at two points is maximized. These methods work even when the light source is changed to one with small light intensity.

Fine-adjustment of the mounting position of the superimposinglens930 may be performed using one of the remaining liquid-crystal light valves925R and925B as a reference instead of the liquid-crystal light valve925G.

With the superimposinglens930 enabled to be fine-adjusted in its mounting position in this way, the necessity is eliminated for setting a wide margin around the image forming area A of the liquid-crystal light valves to cover the offset of the illumination area. Since a narrow margin around the image forming area A works, the efficiency in the utilization of the illumination light is heightened and the brightness of the projected image is increased.

Even with a narrow margin, fine-adjusting the mounting position of the superimposinglens930 prevents the image forming area A from being left partly unilluminated as shown in FIG.5(B). The outline of the projected image is thus free from shadowing.

In the projection-type display apparatus1000, the superimposinglens930 arranged at the exit side of the integratoroptical system923 is the optical element that controls the illumination area of the liquid-crystal devices. Since the superimposinglens930 is fine-adjusted in this embodiment, the position of the illumination area of the liquid-crystal light valve is easily and efficiently adjusted. More particularly, the optical components (the first andsecond lens plates921,922) arranged upstream of the superimposinglens930 in the optical path are fixed and by adjusting only the mounting position of the superimposinglens930, the position of the illumination area B is adjusted taking into consideration the position errors of the optical components in the optical path upstream of the superimposinglens930 to easily and efficiently perform the adjustment.

In this embodiment, the mounting position of the superimposinglens930 is adjustable in only the directions (the ±X direction and ±Y direction) orthogonal to theoptical axis1a. If the mounting position of the superimposinglens930 in the direction of theoptical axis1a (±Z direction) is allowed to be adjustable, the illumination area formed on the liquid-crystal light valve925 can be fine-adjusted as well. More particularly, if fine-adjustment is performed along theoptical axis1a after the mounting position of the superimposinglens930 is adjusted in the directions orthogonal to theoptical axis1a, the illumination area can be reduced to the smallest possible size. With an extremely narrow margin, the efficiency in the utilization of light is even more enhanced.

The mounting position of the superimposinglens930 may be adjustable in any arbitrary direction orthogonal to theoptical axis1a. With the mounting position of the superimposinglens930 adjustable in any arbitrary direction orthogonal to theoptical axis1a, the distortion of the illumination area B shown in FIG. 7 may be corrected to enhance the illumination uniformity.

An error in the mounting angle of the reflection surface of the reflecting mirror in the optical path for each color beam is also a factor contributing to offsetting the illumination area B of the output light from the superimposinglens930 off the image forming area A of the liquid-crystal light valve925. The mounting angle of each reflecting mirror is angled at 45° with respect to the optical axis and if this angle suffers variations the illumination area B will be distorted as shown in FIGS.7(A) and7(B). Thus, the image forming area A is partly offset from the illumination area B as shown in FIG.5(B). If the illuminances on the left-hand side and on the right-hand side of the illumination area B become less uniform, even the advantage presented by the use of the integratoroptical system923 may be lost. For this reason, in the projection-type display apparatus1000, besides the fine-adjustment of the superimposinglens930 already described, the angles of the reflection surfaces of the reflectingmirror943 for reflecting the red light beam R toward the liquid-crystal light valve925R and the reflectingmirror972 for reflecting the blue light beam B toward the liquid-crystal light valve925B shown in FIG. 4 are fine-adjusted about respective axes perpendicular to the planes in which the incident light axis and reflection light axis lie (in the directions shown by the arrows) with respect to the incident light axes. Plate springs and angle adjusting screws similar to those of the position adjusting mechanism for the superimposinglens930 may be used as the mounting angle adjusting mechanism for the reflecting mirrors.

FIGS.8(A)-8(C) show an example of the mechanism for fine-adjusting the mounting angle of the reflectingmirror972. FIG.8(A) shows aholder plate770 for holding the reflectingmirror972, FIG.8(B) shows the mounting angle adjusting mechanism for the reflectingmirror972 viewed from the side of upperlight guide901. FIG.8(C) shows the mounting angle adjusting mechanism for the reflectingmirror972 taken along a cross-section A—A in FIG.8(A). The mountingangle adjusting mechanism760 includes theholder plate770 with itsholder sections772a,772b supporting the reflectingmirror972 from the side opposite its reflection surface. The reflectingmirror972 is also supported at its top edge by aclip773 on theholder plate770. Theholder plate770 has ashaft771 on its center extending vertically. Theshaft771 is rotatably supported by the lowerlight guide902. The reflectingmirror972 is thus permitted to rotate about theaxis1b of theshaft771 of theholder plate770 by a predetermined angle of travel.

Theholder plate770 is provided with aholder spring774 on its one side portion and afirst support point775a of analignment spring775 is inserted through theholder spring774. Thearms775d,775e of thealignment spring775 respectively abutspring pads777a,777b formed on theholder plate770. Second and third support points775b,775c of thealignment spring775 abut asupport section778 provided on the lowerlight guide902. Theholder plate770 is thus fixed to the lowerlight guide902 through thealignment spring775.

Theholder plate770 is pressed in the direction of the arrow B by an adjustingscrew776 supported by the lowerlight guide902. An instrument is inserted through ascrew driving port779 formed in the lowerlight guide902 to screw the adjustingscrew776 and increase its screwed depth. The one side portion of theholder plate770 is pressed in the direction of +B by the adjustingscrew776, and theholder plate770 is turned about theaxis1b of theshaft771 in the direction of an arrow R1 as shown in FIG. 8 (B). The angle of the reflection surface of the reflectingmirror972 is changed to increase the angle of incidence of the light incident on the reflectingmirror972. When the adjustingscrew776 is loosened to decrease its screwed depth on the other hand, one side of theholder plate770 is drawn in the direction of −B by thealignment spring775 and theholder plate770 is turned about theaxis1b of theshaft771 in the direction of an arrow R2 as shown in FIG.8(B). The angle of the reflection surface of the reflectingmirror972 is thus changed to decrease the angle of incidence of the light incident on the reflectingmirror972. By changing the screwed depth of the adjustingscrew776, the angle of the reflection surface of the reflectingmirror972 is adjusted about theaxis1b perpendicular to the plane in which the incident light axis and reflected light axis lie and the mounting angle of the reflection surface with respect to the incident light axis is thus adjusted.

The same mechanism as described above may be used as a mechanism for adjusting the angle of the reflection surface of the reflectingmirror943.

After the mounting angles of the reflectingmirrors943,972 are fine-adjusted, an adhesive is applied through adhesive applyingports906a,906b,907a and907b (FIG. 3) formed in the upperlight guide901 to bond them. Although bonding these mirrors is not necessary, bondedmirrors943 and972 are effectively prevented from being offset under external shock.

The above described fine-adjustment may be automatically or manually performed by measuring illuminance in the periphery portion of the image forming area on the liquid-crystal light valve925R or925B. When the illumination area B is distorted as shown in FIGS.7(A) and7(B), the illuminances on the left-hand side and right-hand side of the illumination area B become less uniform and illuminance unbalance takes place. In the condition shown in FIG.7(A), the illuminance P1 on the leftmost side is greater than the illuminance P2 on the rightmost side of the image forming area A and in the condition shown in FIG.7(B), the illuminance P2 on the rightmost side is greater than the illuminance P1 on the leftmost side of the image forming area A. The mounting angles of the reflectingmirrors943,972 are adjusted until the illuminances P1, P2 on the left-hand side and right-hand side of the image forming area A become a constant value in the same way the lens plates are fine-adjusted as already described. To comply with the case where the light source is changed to one with small light intensity, the mounting angle of each of the reflectingmirrors943,972 is adjusted until the illuminances P1, P2 on the left-hand side and right-hand side of the image forming area A are equalized or until the sum of the illuminances P1, P2 on the left-hand side and right-hand side of the image forming area A is maximized.

Instead of the method of measuring illuminance in the periphery portion of the image forming area A on the liquid-crystal light valve925R or925B and in the same way the superimposinglens930 is fine-adjusted, fine-adjustment of each of themirrors943,972 may be automatically or manually performed by measuring luminance in the periphery portion around the projected image on thescreen100 with the liquid-crystal light valve925R or925B set to allow the illumination light to transmit therethrough to form the image on thescreen100. More particularly, when thescreen100 is illuminated in the condition shown in FIG.7(A) or7(B), illuminances on the left-hand side and right-hand side of the projected image are unbalanced. By measuring the illuminances on the left-hand side and on the right-hand side of the projected image in the same way the image forming area A is measured in illuminance, the mounting angle of each of the reflectingmirrors943,972 is adjusted until illuminances on the left-hand side and on the right-hand side become a constant value, or until illuminances on the left-hand side and on the right-hand side are equalized, or until the sum of the illuminances on the left-hand side and on the right-hand side is maximized.

Both the reflectingmirrors943 and972 may be concurrently moved for fine-adjustment. However, fine-adjustments may be sequentially performed by moving the reflectingmirror943 for angle adjustment using the projected image or the image forming area through the liquid-crystal light valve925R as a reference and then moving the reflectingmirror972 for angle adjustment using the projected image or the image forming area through the liquid-crystal light valve925B as a reference.

Although in this embodiment, the reflectingmirrors943,972 respectively closest to the liquid-crystal light valves925R,925B are adjustable in their mounting angles, other optical elements, in combination with thelight valves925R,925B, such as the blue/green-reflectingdichroic mirror941, green-reflectingmirror942 and converginglens971 are all or partly fine-adjusted in mounting angle. Alternatively, instead of the reflectingmirrors943,972, these optical elements are all or partly fine-adjusted in mounting angle. The fine-adjustment of the reflectingmirrors943,972 respectively closest to the liquid-crystal light valve925R,925B in their mounting angle is the most effective in view of the construction of the apparatus and position adjustment accuracy.

Instead of the reflectingmirror972, theintermediate lens973 may be adjustable and such an arrangement presents the same advantage as the reflectingmirror972 fine-adjusted.

With the reflectingmirrors943,972 enabled to be fine-adjusted in their mounting angle, the necessity for setting a wide margin around the image forming area A of the liquid-crystal light valve to cover the offset of the illumination area is eliminated. Since a narrow margin around the image forming area A works, the efficiency in the utilization of the illumination light is heightened and the brightness of the projected image is increased.

Even with a narrow margin, fine-adjusting the mounting angles of the reflectingmirrors943,972 prevents the image forming area A from being partly offset from the illumination area B as shown in FIGS.7(A) and7(B). The outline of the projected image is thus free from shadowing.

Since the distortion of the illumination area B is removed with the reflectingmirrors943,972 fine-adjusted, the uniform illumination featured by the integratoroptical system923 is fully exploited and a projected image is presented in an extremely uniform brightness.

The above-described angle adjusting mechanism for the optical elements such as the reflecting mirrors works effectively in a projection-type display apparatus without the integratoroptical system923.

Another modification of the projection-type display apparatus will now be discussed. FIG. 9 shows the optical system of the projection-type display apparatus2000 including a polarization illumination unit with an integrator optical system and a polarization beam splitter with a special configuration. Components equivalent to those described in connection with the projection-type display apparatus1000 in FIGS. 1 to8 are designated with the same reference numerals, and the description of them is omitted.

FIG. 9 is a general view of the major portion of the projection-type display apparatus2000 taken in the XZ plane. The projection-type display apparatus2000 includes apolarization illumination unit1, a color separation device for separating a white light beam into three color components, three transmission-type liquid-crystal devices for respectively modulating three color lights according to image information and presenting a display image, a color synthesizing device for synthesizing three color lights to form a color image, and a projection optical system for projecting the color image for presentation.

Thepolarization illumination unit1 includes alight source block10 for outputting randomly polarized light beams in one direction. The randomly polarized light beams from thelight source block10 are converted into almost single type of polarized light beam through apolarization conversion block20.

Thelight source block10 includes alight source lamp101 and aparaboloidal reflector102. The light emitted from thelight source lamp101 is reflected by theparaboloidal reflector102 in one direction and is directed in parallel beams to the polarization conversion block. Thelight source block10 is arranged such that the light source optical axis R of thelight source block10 is offset in parallel in the X direction by a distance D from the optical axis L of the system.

Thepolarization conversion block20 includes a firstoptical element200 and a secondoptical element300.

The firstoptical element200 corresponds to thefirst lens plate921 in the projection-type display apparatus1000 and includes a matrix oflight splitting lenses201 each having a rectangular shape in cross section in the XZ plane. The light source optical axis R is aligned with the center of the firstoptical element200. The light incident on the firstoptical element200 is split into a plurality of intermediatelight beams202 that are spatially separated from each other. With the converging effect by thelight splitting lenses201, images of the same number as thelight splitting lenses201 are formed where the intermediatelight beams202 are converged in a plane orthogonal to the system optical axis L (the XZ plane in FIG.9). The cross-sectional configuration of thelight splitting lens201 in the XY plane is similar to that of the image forming area of a liquid-crystal light valve. In this embodiment, the illumination area has a longer side along the X direction in the XY plane, and the cross-sectional configuration of thelight splitting lenses201 in the XY plane is also rectangular.

The secondoptical element300 includes a converginglens array310, a polarizationseparation unit array320, aselective phase plate380 and a superimposing lens390 (a superimposing device). The secondoptical element300 is disposed in a plane orthogonal to the system optical axis L (the XY plane in FIG. 9) near the position where the images are converged by the firstoptical element200. When the light beams incident on the firstoptical element200 exhibit excellent parallelism, the second optical element may dispense with the converginglens array310. The converginglens array310 as one component of the secondoptical element300 and the firstoptical element200 correspond to the integrator optical system in the projection-type display apparatus1000. The secondoptical element300 separates spatially each of the intermediatelight beams202 into a p-polarized light beam and an s-polarized light beam, and aligns the direction of one of the light beams with the direction of the other light beam, guides light beams with their polarization direction aligned to a single illumination area.

The converginglens array310 is substantially identical in construction to the firstoptical element200. More particularly, the converginglens array310 has a matrix of converginglenses311 having the same number as the light splitting lenses201 (constituting the first optical element200) and converges and guides eachintermediate light beam202 at a particular position of the polarizationseparation unit array320. Each converging lens is preferably optimized taking into consideration the characteristics of the intermediatelight beams202 formed by the firstoptical element200 and an ideal setup that the incident light on the polarizationseparation unit array320 has its principal light beam in parallel with the system optical axis L. With a view to a low-cost design of the optical system and ease of design, the one identical to the firstoptical element200 may be used as the converginglens array310, or a converging lens array of converging lenses each having a cross-sectional shape in the XY plane similar to that of thelight splitting lens201 may be used and the one identical to the firstoptical element200 is used as the converginglens array310. The converginglens array310 may be spaced from the polarization separation unit array320 (closer to the first optical element200).

In FIGS.10(A) and10(B), the polarizationseparation unit array320 has a matrix ofpolarization separation units330. The firstoptical element200 is a matrix of the concentriclight splitting lenses201 with the light splitting lens characteristics and the polarizationseparation unit array320 is constructed by arranging identicalpolarization separation units330 in the same direction in a matrix. If the polarization separation units in the same column in the Y direction are identical, they are preferably arranged with their longer sides aligned with the Y direction and shorter sides aligned with the X direction to constitute the polarizationseparation unit array320 because light loss on the borders between polarization separation units are reduced while the manufacturing cost of the polarization separation unit array is also reduced.

Thepolarization separation unit330 is a rectangular prism structure having apolarization separation face331 and areflection face332 inside and spatially separates each of the intermediate light beams into a p-polarized light and an s-polarized light beam. The cross-sectional shape of thepolarization separation unit330 in the XY plane is similar to that of thelight splitting lens201 in the XY plane (i.e., a rectangular shape with its longer sides horizontal). Thepolarization separation face331 and reflection face332 are placed side by side in the horizontal direction (the X direction). As for thepolarization separation face331 andreflection face332, thepolarization separation face331 is angled at about 45° with respect to the system optical axis L. Thereflection face332 is in parallel with thepolarization separation face331 and both thepolarization separation face331 and reflection face332 are arranged such that the area on the XY plane to which thepolarization separation face331 is projected (equal to the area ofa p exit surface333 to be described later) and is equal to the area on the XY plane to which thereflection face332 is projected (equal to the area of an sexit surface334 to be described later). In this embodiment, the width Wp in the XY plane within a region where thepolarization separation face331 is present is set to be equal to the width Wm in the XY plane within a region where thereflection face332 is present. Thepolarization separation face331 is typically manufactured of dielectric multilayers and thereflection face332 is typically manufactured of dielectric multilayers or an aluminum film.

The light incident on thepolarization separation units330 is separated through thepolarization separation face331 into a p-polarizedlight beam335 passing through thepolarization separation face331 and an s-polarizedlight beam336 that is reflected off thepolarization separation face331 and changes its direction of travel toward thereflection face332. The p-polarizedlight beam335 is directly output past thep exit surface333 from thepolarization separation unit330 while the s-polarizedlight beam336 changes its direction of travel at thereflection face332 travels in parallel with the p-polarizedlight beam335 and is output past ans exit surface334 from thepolarization separation unit330. In this way, the randomly polarized light beams incident on thepolarization separation units330 are separated into two types of polarized light beams mutually different in polarization direction (i.e., the p-polarizedlight beam335 and the s-polarized light beam336) both of which are output from two different places (thep exit surface333 and the s exit surface334) but in almost the same direction. Since thepolarization separation unit330 works in this way, eachintermediate light beam202 needs to be guided to the region where thepolarization separation face331 of eachpolarization separation unit330 is present. For this reason, the positional relationship between thepolarization separation units330 and the respective converginglenses311 and the lens characteristics of each converginglens311 are determined so that theintermediate light beam202 is directed to the center of thepolarization separation face331 of eachpolarization separation unit330. In order to align the center axis of each converginglens311 with the center of the respectivepolarization separation face331 in the respectivepolarization separation unit330, the converginglens array310 is shifted by a quarter of the horizontal width W of thepolarization separation unit330 in the X direction relative to the polarizationseparation unit array320.

The projection-type display apparatus2000 of FIG. 9 will now be further discussed.

Theselective phase plate380 constructed of regularly arranged ½ phase plates is disposed at the exit surface side of the polarizationseparation unit array320. More particularly, a ½ phase plate is placed at thep exit surface333 of eachpolarization separation unit330 constituting the polarizationseparation unit array320 and no ½ phase plate is arranged at each sexit surface334. With such an arrangement of the ½ phase plates, the p-polarized light beams output from thepolarization separation units330 are subjected to rotation of polarization direction while they pass through the ½ phase plates and are converted to s-polarized light beams. On the other hand, the s-polarized light beams output from the s exit surfaces334 pass no ½ phase plate, are subjected to no change in polarization direction, and pass through theselective phase plate380 as they are. The intermediatelight beams202 random in polarization direction are thus converted to one type of polarized light beams (the s-polarized light beams in this case) by the polarizationseparation unit array320 and theselective phase plate380. The superimposinglens390, which is disposed at the side of the exit surface of the selective phase plate380 (i.e., the exit surface of the second optical element300) guides the light beams, now s-polarized through theselective phase plate380, to the illumination area of each liquid-crystal device and then superimposes the light beams on the illumination area. The superimposinglens390 is not necessarily a single lens body, and may be a composite body of a plurality of lenses such as the firstoptical element200 or thesecond lens plate922 in the aforementioned projection-type display apparatus1000.

In summary, one of the functions of the secondoptical element300 is to superimpose the intermediatelight beams202 split by the first optical element200 (i.e., an image segmented by the light splitting lenses201) on the illumination area. Through its polarizationseparation unit array320, the secondoptical element300 spatially separates the intermediatelight beams202, which are the randomly polarized light beams, into the two types of polarized light beams mutually different in polarization direction and converts them into a single type of polarized light beams through theselective phase plate380. The image forming area of the liquid-crystal light valve is thus substantially uniformly illuminated with an almost single type of polarized light beams.

Thepolarization illumination unit1 converts the randomly polarized light beams emitted from thelight source block10 into an almost single type of polarized light beams through thepolarization conversion block20 constructed of the firstoptical element200 and secondoptical element300 and illuminates the image forming area of the liquid-crystal light valve with the well aligned polarized light beams. Since the process of generating polarized light beams is associated with no substantial light loss, almost all of the light emitted from thelight source block10 is guided to the image forming area of the liquid-crystal light valve and the efficiency in the utilization of the light is very high.

Since the converginglens array310, polarizationseparation unit array320 andselective phase plate380, all constituting the secondoptical element300 are optically integrated in this embodiment, the light loss taking place in borders or interfaces are reduced and the efficiency in the utilization of the light is further enhanced.

To be compatible with the rectangular shape of the image forming area with its horizontal sides longer, eachlight splitting lens201, constituting the firstoptical element200, is also made rectangular with its horizontal sides longer, and the two types of polarized light beams output from the polarizationseparation unit array320 are arranged in the horizontal direction (the X direction). Because of this, even the image forming area having a rectangular shape with its horizontal sides longer is illuminated, no light quantity is wasted, and the illumination efficiency (an utilization of light) of the liquid-crystal light valve is enhanced.

If light beams random in polarization direction are simply separated into a p-polarized light beam and an s-polarized light beam, the entire width of each beam after separation is doubled, and the optical system is accordingly enlarged. In thepolarization illumination unit1 of this embodiment, the firstoptical element200 forms a plurality of small converging images, a space, generated in the course of the forming process of the images and having no light within, is skillfully exploited in a manner such that thereflection face332 of thepolarization separation unit330 is arranged in that space, the horizontal expansion of each light beam arising from the separation of the beam into two beams is accommodated and the entire width of the light beam is free from expansion thus permitting a compact optical system design.

The projection-type display apparatus2000 having thepolarization illumination unit1 employs a liquid-crystal device that modulates a single type of polarized light beams. If a conventional illumination device is used to guide randomly polarized light beams to the liquid-crystal device, polarizers (not shown) will absorb and convert almost half the randomly polarized light beams into heat, thereby not only degrading utilization of light but also requiring a noisy and large cooling device to control heat emitted from the polarizers. The projection-type display apparatus2000 substantially eases this problem.

In itspolarization illumination unit1, the projection-type display apparatus2000 rotates the polarization direction of one type of polarized light beams only (e.g., p-polarized light beams only) through the ½ phase plates to align them with the other type of polarized light beams (e.g., s-polarized light beams in polarization direction). For this reason, an almost single type of polarized light beams with their polarization directions aligned is guided to three liquid-crystal light valves925R,925G, and925B, absorption by the polarizers is extremely small, utilization of the light is enhanced to result in a bright projected image.

Thepolarization illumination unit1 spatially separates two types of polarized light beams in the horizontal direction (the X direction) in the secondoptical element300. Thepolarization illumination unit1 therefore wastes no light quantity and is best suited to illuminate a rectangular liquid-crystal device with its horizontal sides longer.

Thepolarization illumination unit1 restricts the expansion of the light beam output from the incorporated polarizationseparation unit array320 regardless of the incorporated polarization conversion optical elements. This means that when a liquid-crystal device is illuminated, practically no lights are incident on the liquid-crystal device with a large angle with respect thereto. A highly bright projected image is therefor formed without using a small f-number, large aperture projection lens. As a result, a compact projection-type display apparatus is provided.

Like the projection-type display apparatus1000 already described, in the projection-type display apparatus2000 the mounting position of the superimposinglens390 disposed at the side of the exit surface of thepolarization illumination unit1 may be adjustable in the direction orthogonal to the optical axis L so that the illumination areas of the liquid-crystal light valves925R,925G and925B by thepolarization illumination unit1 are fine-adjusted horizontally forward or backward and horizontally to the left or to the right and the image forming area of each liquid-crystal device is continuously kept within the illumination area.

The lens mounting position adjusting mechanism described in FIG. 6 is available as a mechanism for adjusting the mounting position of the superimposinglens390. The fine-adjustment procedure and advantages achieved by the position adjustment of the illumination area remain unchanged from those already described in connection with the projection-type display apparatus1000.

In the projection-type display apparatus2000, fine-adjusting the mounting position of the superimposinglens390 eliminates the need for setting a wide margin around the image forming area of the liquid-crystal device to cover the offset of the illumination area as in the conventional art. Since a narrow margin around the image forming area works, the utilization of the illumination light is increased and the projected image is brightened.

Even with a narrow margin, fine-adjusting the mounting position of each optical element prevents the image forming area of the liquid-crystal device from being partly offset from the illumination area of the polarization separation unit array. The outline of the projected image is thus free from shadowing.

In thepolarization illumination unit1, the superimposinglens390 for superimposing the intermediate light beams on the illumination area is the optical element that controls the illumination area of the liquid-crystal device. With the superimposinglens390 enabled to be fine-adjusted in this embodiment, the mounting position of the superimposinglens390 only is adjusted with the optical components upstream of the superimposinglens390 in the optical path fixed and the position of the illumination area B is thus adjusted taking into consideration the position errors of the optical components such as the firstoptical element200 upstream of the superimposinglens390 in the optical path. The position of the illumination area of the liquid-crystal light valve is efficiently adjusted and adjusting procedure itself is not time consuming.

An error in the mounting angle of the reflection surface of the reflecting mirror in the optical path for each color beam is also a factor contributing to offsetting the illumination area of the liquid-crystal device by thepolarization illumination unit1 from the image forming area of the liquid-crystal device. The mounting angle of reach reflecting mirror is angled at 45° with respect to the optical axis. If this angle suffers variations, the illumination area will be distorted (FIGS.7(A) and7(B)) and the illumination area is partly projected out of the image forming area of the liquid-crystal device. When the illumination area is distorted in this way, the illuminances on the left-hand side and on the right-hand side of the illumination area become unbalanced, and even the advantage presented by the use of thepolarization illumination unit1 may be lost.

In the projection-type display apparatus2000, the angles of the reflection surfaces of the reflectingmirrors943,972 in the respective color beam optical paths may be fine-adjusted with respect to the incident light axes about the axes perpendicular to the planes in which the incident light axis and the reflection light axis line (in the direction of the arrow in FIG.9). The mounting position of theintermediate lens973 arranged between the reflectingmirrors943,972 may be adjusted vertically upward or downward and horizontally to the left or to the right. The angle adjusting mechanism described in reference to FIG. 8 may be the mechanism for adjusting the mounting angle of each reflecting mirror. The lens mounting position adjusting mechanism described with reference to FIG. 6 may be the mechanism for adjusting the mounting position of theintermediate lens973.

In the two preceding embodiments, the liquid-crystal light valves925R,925G and925B are of a transmission type light valve. The present invention may be equally applied to a projection-type display apparatus employing a reflection-type liquid-crystal device. An example of the projection-type display apparatus employing a reflection-type light valve instead of a transmission-type light valve will now be described. In a projection-type display apparatus3000 of this embodiment, components identical to those described with reference to FIGS. 9 and 10 are designated with the same reference numerals and the description of them is not repeated.

FIG. 11 shows the major portion of the projection-type display apparatus3000 of this embodiment. FIG. 11 is a cross-sectional view of the secondoptical element300 taken along the XZ plane.

Apolarization beam splitter400 includes aprism401 that has an s-polarized lightbeam reflecting face401 that reflects an s-polarized light beam at 45° with respect to the XZ plane in FIG.11 and permits a p-polarized light beam to transmit therethrough. Since the light beams output from the secondoptical element300 are the ones having an almost single polarization direction, almost all light beams are reflected or transmitted through thepolarization beam splitter400. In this embodiment, the light beams output from the secondoptical element300 are s-polarized light beams and the s-polarized light beams are bent at a right angle by an s-polarized lightbeam reflecting face401 and are introduced to aprism unit500 to which a dichroic film is glued in a cross configuration, and are separated into three color components R, G and B. Separated color component lights are respectively directed to reflection-type liquid-crystal devices600R,600G and600B arranged along three sides of thedichroic prism500. The light beams introduced into the reflection-type liquid-crystal devices600R,600G and600B are modulated there.

FIG. 12 shows an example of the reflection-type liquid-crystal devices600R,600G, and600B. The reflection-type liquid-crystal devices600R,600G, and600B are an active matrix liquid-crystal device in which pixels are arranged in a matrix with a TFT switching element connected to each pixel and a liquid-crystal layer620 interposed between a pair ofsubstrates610,630. Thesubstrate610 is manufactured of silicon and has asource611 and adrain616. Also formed on thesubstrate610 are asource electrode612 and adrain electrode617, both made of aluminum layers, a channel ofsilicon dioxide613, a gate electrode of asilicon layer614 and atantalum layer615, aninterlayer insulating layer618, and areflection pixel electrode619 of an aluminum layer, and thedrain electrode617 and thereflection pixel electrode619 are electrically connected through a contact hole H. Since thereflection pixel electrode619 is opaque, theinterlayer insulating layer618 is laminated over the gate electrode, thesource electrode612 and thedrain electrode617. Since the spacing betweenadjacent pixel electrodes619 is made fairly small, a large aperture ratio of the device is permitted and a projected image is brightened. A holding capacitance may also be formed by thedrain616, asilicon dioxide layer613′, asilicon layer614′ and antantalum layer615′.

Theopposed substrate630 has an opposedelectrode631 of ITO on its side facing the liquid-crystal layer620 and ananti-reflection layer632 on the other side. A super-homeotropic type in which liquid-crystal molecules621 orient vertically with no voltage applied (OFF) and twist by 90° with a voltage applied (ON) may be employed as the liquid-crystal layer620 in this embodiment. As shown in FIG. 4, with no voltage applied (OFF), the s-polarized light beams are introduced from thepolarization beam splitter400 to the reflection-type liquid-crystal devices600R,600G and600B are returned to thepolarization beam splitter400 without changing the polarization direction from the reflection-type liquid-crystal devices600R,600G and600B, and are reflected by the s-polarized lightbeam reflecting face401 without reaching theprojection lens unit6. With the voltage applied (ON), the s-polarized light beams introduced from thepolarization beam splitter400 to the reflection-type liquid-crystal devices600R,600G and600B are converted to p-polarized light beams with their polarization direction changed by the twist of the liquid-crystal molecules621, pass through the s-polarized lightbeam reflecting face401, and are then projected to thescreen100 via theprojection lens unit6.

The operation of the projection-type display apparatus3000 will now be discussed with reference to FIG.11. The light beams modulated through the reflection-type liquid-crystal devices600R,600G and600B are synthesized by theprism unit500 and are then projected to thescreen100 through thepolarization beam splitter400 andprojection lens unit6.

In the projection-type display apparatus3000, the illumination area of the liquid-crystal device by thepolarization illumination unit1 is adjusted to its appropriate position and shape by enabling to be adjustable vertical upward or downward and horizontally to the left or to the right the mounting position of the superimposinglens390 disposed at the side of the exit surface of the secondoptical element300 constituting thepolarization conversion block20 in thepolarization illumination unit1. The position adjusting mechanism, procedure and advantage remain unchanged from those already described in connection with the projection-type display apparatus2000.

Besides the advantage attributed to the adjustment of the illumination area, the projection-type display apparatus3000 presents the same advantages as those of the above-described projection-type display apparatuses and further offers the following advantage. Since the color separation device and the color synthesizing device are integrated into the same prism unit, the optical path length is substantially shortened. The large aperture ratio of the liquid-crystal device minimizes light loss. A bright projected image is thus obtained without using a large aperture lens. With the first optical element and the second optical element, uniform polarized light beams with no illuminance variations are obtained, making the display area and the entire projection screen area uniform quality to result in an extremely bright projected image.

Although the reflection-type liquid-crystal devices600R,600G and600B are used as the reflection-type modulating device in this embodiment, reflection-type modulating devices of non-liquid-crystal type may be used because its construction, materials of each element, and mode of operation of the liquid-crystal layer620 are not limited to those already described above.

If a prism403 constituting thepolarization beam splitter400 and aprism501 constituting theprism unit500 is integrated into a single prism, light loss taking place at the border therebetween will be eliminated and the utilization of light will be enhanced.

Although the above examples have been discussed in connection with the fine-adjustment mechanisms of the optical elements in the projection-type display apparatuses for projecting a color image, these fine-adjustment mechanisms are equally applied to a projection-type display apparatus for projecting a monochrome image.

The present invention is not limited to the layout of the optical systems, and modifications in the layout still fall within the scope of the present invention.

Besides the projection-type discussed above in which an image is projected to the screen from the viewing side of the screen, a rear-projection-type for projecting an image from the side opposite the viewing side of the screen is available. The present invention is applied to this rear-projection-type display apparatus.

As described above, the projection-type display apparatus of the present invention permits the mounting position of the superimposing device to be adjustable for superimposing a plurality of intermediate light beams on the image forming area of the modulating device. When the reflection device is arranged in the optical path between the light source and the modulating device, the mounting angle of the reflection device is made adjustable. Since the position of the illumination area by the illumination light that illuminates the modulating means is fine-adjusted, the illumination area is positioned such that it always includes the image forming device of the modulating device within.

The above arrangement makes it unnecessary to set a large margin around the image forming area to cover the offset of the illumination area from the image forming area of the modulating device. The utilization of the illumination light is thus enhanced and the brightness of the projected image is heightened. Since the illumination area by the illumination light is positioned such that is includes the image forming area, no shadow is generated around the projected image.

Since the mounting position is fine-adjusted of the super-imposing device, which is an optical component chiefly determining the illumination area of the modulating device, the adjustment of the position of the illumination area is thus performed taking into consideration the mounting errors of optical components (optical elements) in front of the superimposing device (upstream of the superimposing means). The position of the illumination area of the modulating device is easily and efficiently adjusted.

While the invention has been described in relation to preferred embodiments, many modifications and variations are intended to be within the scope of the present invention as defined in the append claims.

Claims (46)

What is claimed is:

1. A projection-type display apparatus projector comprising:

a light source for emitting a light beam;

modulating means for modulating the light beam emitted by the light source;

projecting means for projecting the modulated light beam from the modulating means onto a projection screen;

an optical element, disposed in an optical path between the light source and the modulating means, for splitting the light beam into a plurality of intermediate light beams; and

superimposing means for superimposing each of the intermediate light beams onto an image forming area of the modulating means, wherein a mounting position of the superimposing means is adjustable.

2. The projection-type display apparatus projector ofclaim 1, further comprising reflection means in the optical path between the light source and the modulating means, wherein a mounting angle of the reflection means is adjustable with respect to an incident optical axis.

3. The projection-type display apparatus projector ofclaim 1, further comprising:

a color separating optical system for separating an output light from the superimposing means into color light beams;

a plurality of modulating means for modulating the color light beams separated by the color separating optical system;

a color synthesizing optical system for synthesizing the color light beams modulated by the plurality of modulating means, wherein the synthesized modulated light beam from the color synthesizing optical system is enlarged and projected to the projection screen by the projection means; and

reflection means disposed in an optical path between the color separating optical system and at least one of the plurality of modulating means, wherein a mounting angle of the reflection means is adjustable with respect to an incident optical axis.

4. The projection-type display apparatus projector ofclaim 3, wherein a mounting angle of the reflection means located closest to the modulating means is adjustable.

5. The projection-type display apparatus projector ofclaim 3, wherein the modulating means is a reflection type modulating means and the color separating optical system and the color synthesizing optical system are integrated into the same optical system.

6. A projection-type display apparatus projector comprising:

a light source for outputting a light beam;

a first optical element for splitting the light beam output from the light source into a plurality of intermediate light beams;

a second optical element including a polarization conversion unit and superimposing means for superimposing light beams output from the polarization conversion unit, wherein the second optical element is arranged in a vicinity of a position where the intermediate light beams are converged, the second optical element separates each of the intermediate light beams from the first optical element into a p-polarized light beam and a s-polarized light beam, the second optical element further aligns a polarization direction of one of the p-polarized light beam and the s-polarized light beam with the polarization direction of the other of the p-polarized light beam and the s-polarized light beam, and the second optical element outputs the resulting light beams;

modulating means for modulating the light beams emitted from the second optical element; and

projection means for enlarging and projecting the modulated light beams from the modulating means to a projection screen, wherein a mounting position of the superimposing means is adjustable.

7. The projection-type display apparatus projector ofclaim 6, further comprising reflection means in an optical path between the light source and the modulating means, wherein a mounting angle of the reflection means is adjustable with respect to an incident optical axis.

8. The projection-type display apparatus projector ofclaim 6, further comprising:

a color separating optical system for separating an output light from the superimposing means into color light beams;

a plurality of modulating means for modulating the color light beams separated by the color separating optical system;

a color synthesizing optical system for synthesizing the color light beams modulated by the plurality of modulating means, wherein the synthesized modulated light beam from the color synthesizing optical system is enlarged and projected to the projection means to the projection screen; and

reflection means located in an optical path between the color separating optical system and at least one of the plurality of modulating means, wherein a mounting angle of the reflection means is adjustable with respect to an incident optical axis.

9. The projection-type display apparatus projector ofclaim 8, wherein a mounting angle of the reflection means located closest to the modulating means is adjustable.

10. The projection-type display apparatus projector ofclaim 8, wherein the modulating means is a reflection type modulating means and the color separating optical system and the color synthesizing optical system are integrated into the same optical system.

11. A projection-type display apparatus projector comprising:

a light source that emits a light beam;

modulating means for modulating the light beam emitted by the light source;

projection means for enlarging and projecting the modulated light beam from the modulating means onto a projection screen;

an optical element, located in an optical path between the light source and the modulating means, that splits the light beam emitted from the light source into a plurality of intermediate light beams;

superimposing means for superimposing each of the intermediate light beams from the optical element onto an image forming area of the modulating means; and

an adjusting mechanism that adjusts a mounting position of the superimposing means.

12. The projection-type display apparatus projector ofclaim 11, further comprising:

a first adjusting mechanism that adjusts the mounting position of the superimposing means in a first direction that is orthogonal to an optical axis; and

a second adjusting mechanism that adjusts the mounting position of the superimposing means in a second direction that is orthogonal to the optical axis and the first direction.

13. The projection-type display apparatus projector ofclaim 12, wherein the adjusting mechanism comprises:

a base adjusting plate;

a first adjusting plate slidably movable in the first direction relative to the base adjusting plate; and

a second adjusting plate slidably movable in the second direction relative to the first adjusting plate.

14. The projection-type display apparatus projector ofclaim 13, wherein the adjusting mechanism comprises a first slip prevention mechanism that prevents the first adjusting plate from slipping in the second direction and a second slip prevention mechanism for preventing the second adjusting plate from slipping in the first direction.

15. The projection-type display apparatus projector ofclaim 13, wherein the superimposing means is fixed to the second adjusting plate.

16. A projection-type display apparatus projector comprising:

a light source that outputs a light beam;

a first optical element that splits a light beam from the light source into a plurality of intermediate light beams;

a second optical element including a polarization conversion unit and superimposing means for superimposing light beams output from the polarization conversion unit, wherein the second optical element is arranged in a vicinity of a position where the intermediate light beams are converged, the second optical element separates the intermediate light beams from the first optical element into a p-polarized light beam and a s-polarized light beam, the second optical element aligns a polarization direction of one of a p-polarized light beam and a s-polarized light beam with the polarization direction of the other of the p-polarized light beam and the s-polarized light beam, and the second optical element outputs the resulting light beams;

modulating means for modulating the light beams emitted from the second optical element;

projection means for enlarging and projecting the modulated light beams from the modulating means onto a projection screen; and

an adjusting mechanism for adjusting a mounting position of the superimposing means.

17. The projection-type display apparatus projector ofclaim 16, further comprising:

a first adjusting mechanism that adjusts the mounting position of the superimposing means in a first direction that is orthogonal to an optical axis; and

a second adjusting mechanism for adjusting the mounting position of the superimposing means in a second direction that is orthogonal to the optical axis and the first direction.

18. The projection-type display apparatus projector ofclaim 17, wherein the adjusting mechanism comprises:

a base adjusting plate;

a first adjusting plate slidably movable in the first direction relative to the base adjusting plate; and

a second adjusting plate slidably movable in the second direction relative to the first adjusting plate.

19. The projection-type display apparatus projector ofclaim 18, wherein the adjusting mechanism comprises a first slip prevention mechanism that prevents the first adjusting plate from slipping in the second direction and a second slip prevention mechanism that prevents the second adjusting plate from slipping in the first direction.

20. The projector ofclaim 3, further comprising:

a light guiding system disposed in a longest optical path between the color separating optical system and each of the plurality of modulating means, the light guiding system including two lenses and an intermediate lens disposed between the two lenses, a position of the intermediate lens being adjustable.

21. The projector ofclaim 8, further comprising:

a light guiding system disposed in a longest optical path between the color separating optical system and each of the plurality of modulating means, the light guiding system including two lenses and an intermediate lens disposed between the two lenses, a position of the intermediate lens being adjustable.

22. The projector ofclaim 11, further comprising:

a color separating optical system that separates the light emitted from the superimposing means into a plurality of color lights;

a plurality of the modulating means that each modulates the color light separated by the color separating optical system;

a light guiding system disposed in a longest optical path between the color separating optical system and each of the plurality of modulating means, the light guiding system including two lenses and an intermediate lens disposed between the two lenses; and

a further adjusting mechanism that adjusts a position of the intermediate lens.

23. The projector ofclaim 16, further comprising:

a color separating optical system that separates the light emitted from the superimposing means into a plurality of color lights;

a plurality of the modulating means that each modulates the color light separated by the color separating optical system;

a light guiding system disposed in a longest optical path between the color separating optical system and each of the plurality of modulating means, the light guiding system including two lenses and an intermediate lens disposed between the two lenses; and

a further adjusting mechanism that adjusts a position of the intermediate lens.

24. A projector comprising:

a light source for emitting a light beam;

modulating means for modulating the light beam emitted by the light source;

projecting means for projecting the modulated light beam from the modulating means onto a projection screen;

an optical element, disposed in an optical path between the light source and the modulating means, for splitting the light beam into a plurality of intermediate light beams;

superimposing means for superimposing each of the intermediate light beams onto an image forming area of the modulating means;

a power supply;

an input/output interface circuit;

a video signal processing circuit;

a control circuit for driving and controlling the projector; and

an outer casing for housing the light source, the modulating means, the optical element, the superimposing means, the power supply, the input-output interface circuit, the video signal processing circuit, and the control circuit, wherein, a mounting position of the superimposing means is adjustable.

25. The projector ofclaim 24, further comprising reflection means in the optical path between the light source and the modulating means, wherein a mounting angle of the reflection means is adjustable with respect to an incident optical axis.

26. The projector ofclaim 25, further comprising:

a color separating optical system for separating an output light from the superimposing means into color light beams;

a plurality of modulating means for modulating the color light beams separated by the color separating optical system;

a color synthesizing optical system for synthesizing the color light beams modulated by the plurality of modulating means, wherein the synthesized modulated light beam from the color synthesizing optical system is enlarged and projected to the projection screen by the projection means; and

reflection means disposed in an optical path between the color separating optical system and at least one of the plurality of modulating means, wherein a mounting angle of the reflection means is adjustable with respect to an incident optical axis.

27. The projector ofclaim 26, wherein a mounting angle of the reflection means located closest to the modulating means is adjustable.

28. The projector ofclaim 26, wherein the modulating means is a reflection type modulating means and the color separating optical system and the color synthesizing optical system are integrated into the same optical system.

29. The projector ofclaim 26, further comprising:

a light guiding system disposed in a longest optical path between the color separating optical system and each of the plurality of modulating means, the light guiding system including two lenses and an intermediate lens disposed between the two lenses, a position of the intermediate lens being adjustable.

30. A projector comprising:

a light source for emitting a light beam;

a first optical element for splitting the light beam output from the light source into a plurality of intermediate light beams;

a second optical element including a polarization conversion unit and superimposing means for superimposing light beams output from the polarization conversion unit, wherein the second optical element is arranged in a vicinity of a position where the intermediate light beams are converged, the second optical element separates each of the intermediate light beams from the first optical element into a p-polarized light beam and an s-polarized light beam, the second optical element further aligns a polarization direction of one of the p-polarized light beam and the s-polarized light beam, and the second optical element outputs the resulting light beams;

modulating means for modulating the light beam emitted from the second optical element;

projecting means for enlarging and projecting the modulated light beams from the modulating means onto a projection screen;

a power supply;

an input/output interface circuit;

a video signal processing circuit;

a control circuit for driving and controlling the projector; and

an outer casing for housing the light source, the first and second optical elements, the modulating means, the power supply, the input-output interface circuit, the video signal processing circuit, and the control circuit, wherein, a mounting position of the superimposing means is adjustable.

31. The projector ofclaim 30, further comprising reflection means in the optical path between the light source and the modulating means, wherein a mounting angle of the reflection means is adjustable with respect to an incident optical axis.

32. The projector ofclaim 30, further comprising:

a color separating optical system for separating an output light from the superimposing means into color light beams;

a plurality of modulating means for modulating the color light beams separated by the color separating optical system;

a color synthesizing optical system for synthesizing the color light beams modulated by the plurality of modulating means, wherein the synthesized modulated light beam from the color synthesizing optical system is enlarged and projected to the projection means to the projection screen; and

reflection means located in an optical path between the color separating optical system and at least one of the plurality of modulating means, wherein a mounting angle of the reflection means is adjustable with respect to an incident optical axis.

33. The projector ofclaim 27, wherein a mounting angle of the reflection means located closest to the modulating means is adjustable.

34. The projector ofclaim 27, wherein the modulating means is a reflection type modulating means and the color separating optical system and the color synthesizing optical system are integrated into the same optical system.

35. The projector ofclaim 32, further comprising:

a light guiding system disposed in a longest optical path between the color separating optical system and each of the plurality of modulating means, the light guiding system including two lenses and an intermediate lens disposed between the two lenses, a position of the intermediate lens being adjustable.

36. A projector comprising:

a light source for emitting a light beam;

modulating means for modulating the light beam emitted by the light source;

projecting means for projecting the modulated light beam from the modulating means onto a projection screen;

an optical element, located in an optical path between the light source and the modulating means, that splits the light beam emitted from the light source into a plurality of intermediate light beams;

superimposing means for superimposing each of the intermediate light beams onto an image forming area of the modulating means;

an adjusting mechanism that adjusts a mounting position of the superimposing means;

a power supply;

an input/output interface circuit;

a video signal processing circuit;

a control circuit for driving and controlling the projector; and

an outer casing for housing the light source, the modulating means, the optical element, the superimposing means, the adjusting mechanism, the power supply, the input-output interface circuit, the video signal processing circuit, and the control circuit.

37. The projector ofclaim 36, further comprising:

a color separating optical system that separates the light emitted from the superimposing means into a plurality of color lights;

a plurality of the modulating means that each modulates the color light separated by the color separating optical system;

a light guiding system disposed in a longest optical path between the color separating optical system and each of the plurality of modulating means, the light guiding system including two lenses and an intermediate lens disposed between the two lenses; and

a further adjusting mechanism that adjusts a position of the intermediate lens.

38. The projector ofclaim 36, further comprising:

a first adjusting mechanism that adjusts the mounting position of the superimposing means in a first direction that is orthogonal to an optical axis; and

a second adjusting mechanism that adjusts the mounting position of the superimposing means in a second direction that is orthogonal to the optical axis and the first direction.

39. The projector ofclaim 38, wherein the adjusting mechanism comprises:

a base adjusting plate;

a first adjusting plate slidably movable in the first direction relative to the base adjusting plate; and

a second adjusting plate slidably movable in the second direction relative to the first adjusting plate.

40. The projector ofclaim 39, wherein the adjusting mechanism comprises a first slip prevention mechanism that prevents the first adjusting plate from slipping in the second direction and a second slip prevention mechanism for preventing the second adjusting plate from slipping in the first direction.

41. The projector ofclaim 39, wherein the superimposing means is fixed to the second adjusting plate.

42. A projector comprising:

a light source for emitting a light beam;

a first optical element for splitting the light beam output from the light source into a plurality of intermediate light beams;

a second optical element including a polarization conversion unit and superimposing means for superimposing light beams output from the polarization conversion unit, wherein the second optical element is arranged in a vicinity of a position where the intermediate light beams are converged, the second optical element separates each of the intermediate light beams from the first optical element into a p-polarized light beam and an s-polarized light beam, the second optical element further aligns a polarization direction of one of the p-polarized light beam and the s-polarized light beam, and the second optical element outputs the resulting light beams;

modulating means for modulating the light beam emitted from the second optical element;

projecting means for enlarging and projecting the modulated light beam from the modulating means onto a projection screen;

an adjusting mechanism for adjusting a mounting position of the superimposing means;

a power supply;

an input/output interface circuit;

a video signal processing circuit;

a control circuit for driving and controlling the projector; and

an outer casing for housing the light source, the first and second optical elements, the modulating means, the adjusting mechanism, the power supply, the input-output interface circuit, the video signal processing circuit, and the control circuit.

43. The projector ofclaim 42, further comprising:

a color separating optical system that separates the light emitted from the superimposing means into a plurality of color lights;

a plurality of the modulating means that each modulates the color light separated by the color separating optical system;

a light guiding system disposed in a longest optical path between the color separating optical system and each of the plurality of modulating means, the light guiding system including two lenses and an intermediate lens disposed between the two lenses; and

a further adjusting mechanism that adjusts a position of the intermediate lens.

44. The projector ofclaim 43, further comprising:

a first adjusting mechanism that adjusts the mounting position of the superimposing means in a first direction that is orthogonal to an optical axis; and

a second adjusting mechanism that adjusts the mounting position of the superimposing means in a second direction that is orthogonal to the optical axis and the first direction.

45. The projector ofclaim 44, wherein the adjusting mechanism comprises:

a base adjusting plate;

a first adjusting plate slidably movable in the first direction relative to the base adjusting plate; and

a second adjusting plate slidably movable in the second direction relative to the first adjusting plate.

46. The projector ofclaim 45, wherein the adjusting mechanism comprises a first slip prevention mechanism that prevents the first adjusting plate from slipping in the second direction and a second slip prevention mechanism that prevents the second adjusting plate from slipping in the first direction.

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