US20040004775A1

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Publication number: US20040004775A1
Application number: US10/335,738
Authority: US
Inventors: Arthur Turner; Andrew Dewa; Mark Heaton
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-07-08
Filing date: 2003-01-02
Publication date: 2004-01-08
Also published as: US20050146765A1; US7009748B2

Abstract

A system and method for providing a resonant beam sweep about a first axis. A mirror or reflective surface supported by a first pair of torsional hinges is driven into resonant oscillations about the first axis by inertially coupling energy through the first pair of torsional hinges. A light source reflects a beam of light from the mirror such that the oscillating mirror produces a beam sweep across a target area. The resonant beam sweep is moved orthogonally on the target area by a gimbals portion of the mirror pivoting about a second axis according to one embodiment. A second independent mirror provides the orthogonal movement according to a second embodiment.

Description

This application claims the benefit of U.S. Provisional Application No. 60/394,321, filed on Jul. 8, 2002, entitled Scanning Mirror, which application is hereby incorporated herein by reference.[0001]

TECHNICAL FIELD

The present invention relates generally to projection displays and laser copiers. More specifically, the invention relates to the use of MEMS (micro-electric mechanical systems) type mirrors (such as torsional hinge mirrors) to provide resonant scanning of a light beam on a display screen or on a photosensitive medium. The resonant scan may be generated by using a single dual axis mirror or two single axis mirrors. A first set of torsional hinges is used for providing the resonant scan by oscillating the mirror about the torsional hinges at the mirror's resonant frequency if a dual axis mirror is used. Alternately, a first one of two single axis mirrors may be driven to resonance about its torsional hinges to provide the bi-directional scan. The second pair of torsional hinges of the dual axis mirror or the second single axis mirror provides movement about a second axis to control movement of the resonant beam sweep or scan in a direction orthogonal to the resonant scanning to maintain closely spaced parallel image lines on the projection display or photosensitive medium.[0002]

BACKGROUND

Although rotating polygon scanning mirrors are typically used in laser printers to provide a beam sweep or scan of the image of a modulated light source across a moving photosensitive medium, such as a rotating drum, there have also been prior art efforts to use a much less expensive flat mirror with a single reflective surface, such as a mirror oscillating in resonance, to provide the scanning beam. Unfortunately, these prior art efforts of using a scanning or oscillating mirror have required a compromise in performance in that only one direction of the resonant beam sweep could be used to print an image line at a right angle on a page. For example, to generate image lines that are at a right angle to a moving photosensitive medium, the scanning mirror generating the beam sweep is typically mounted at a slight angle to compensate for the movement of the photosensitive medium. It will be appreciated that the photosensitive medium typically moves at a right angle with respect to the beam sweep (such as a rotating drum). Unfortunately, if the mirror is mounted at a slight angle to compensate for medium movement during the forward beam sweep, the return beam sweeps will traverse a trajectory on the moving photosensitive drum which will be at an angle which is unacceptable with the first printed image line since the effect of the moving medium and the angle mounting of the mirror will now be additive rather than subtractive. Consequently, unlike the present invention, when such a single reflecting surface resonant mirror was used with these prior art efforts, it was necessary to interrupt the modulation of the reflected light beam and wait for the mirror to complete the return sweep or cycle and then again start scanning in the original direction. This requirement of only using one of the sweep directions of the mirror of course reduces the print speed and requires expensive and sophisticated synchronization between the mirror and the rotating drum.[0003]

The assignee of the present invention has recently developed a dual axis mirror with a single reflection surface described in U.S. patent application Ser. No. ______ and entitled “Laser Printer Apparatus Using a Pivoting Scanning Mirror”. This dual axis mirror uses a first set of torsional hinges for providing oscillating beam sweep such as a resonant beam sweep and a second set of torsional hinges that selectively moves the oscillating beam sweep in a direction orthogonal to the oscillating or resonant beam sweep. By dynamically controlling the orthogonal position of the beam sweep to compensate for movement of the photosensitive medium, both directions of the resonant beam sweep may be used to print parallel image lines. Alternately, two single axis mirrors can be arranged such that one mirror provides the resonant beam sweep and the other mirror controls the orthogonal position of the beam sweep to allow both directions of the resonant beam sweep to be used for printing.[0004]

It will also be appreciated by those skilled in the art that in addition to laser printing, control of the orthogonal (vertical) position of the oscillating or resonant scan allows a single surface or flat oscillating mirror to be used to provide a full frame of raster scans suitable for use on projection displays including micro projection displays such as cell phones, Personal Digital Assistants (PDA's), notebook computers and heads-up displays. However, if such displays are to be commercially acceptable, they must be small, low cost, robust enough to withstand greater than 1000 G's of shock, and stable over the operating temperature normally experienced by hand-held products.[0005]

Consequently, it will be appreciated that the high frequency scanning mirror is a key component to the success of such products. Further, since many of the applications for such mirror projection displays are battery powered, all of the components (including the scanning mirror) must be energy efficient.[0006]

Texas Instruments presently manufactures a two axis analog mirror MEMS device fabricated out of a single piece of material (such as silicon, for example) typically having a thickness of about 100-115 microns using semiconductor manufacturing processes. The layout consists of a mirror having dimensions on the order of a few millimeters supported on a gimbals frame by two silicon torsional hinges. The gimbals frame is supported by another set of torsional hinges, which extend from the gimbals frame to a support frame or alternately the hinges may extend from the gimbals frame to a pair of hinge anchors. This Texas Instruments manufactured mirror with two orthogonal axes is particularly suitable for use with laser printers and/or projection displays. The reflective surface of the mirror may have any suitable perimeter shape such as oval, rectangular, square or other.[0007]

One presently used technique to oscillate the mirror about a first axis is to provide electromagnetic coil on each side of the mirror and then driving the coils with an alternating signal at the desired sweep frequency. The same technique is also used to move the sweep of the beam orthogonal to maintain a parallel raster scan. The present invention, however, discloses improved techniques for generating a resonant beam sweep.[0009]

SUMMARY OF THE INVENTION

The issues mentioned above are addressed by the present invention which, according to one embodiment, provides a mirror apparatus suitable for use as the means of generating a sweeping or scanning beam of light across the width of a target medium such as the projection screen of a display device or a photosensitive medium of a copier. According to one embodiment, the apparatus comprises a mirror device including a reflective surface portion positioned to intercept a beam of light from a light source. The reflective surface of the mirror device is supported by a first torsional hinge arrangement for pivoting around a first axis and is also supported on a gimbals frame by a second hinge arrangement for pivoting about a second axis substantially orthogonal to the first axis. Thus, pivoting of the mirror device about the first axis results in a beam of light reflected from the reflective surface scanning along the first dimension of the display screen or photosensitive medium and pivoting of the device about the second axis results in the reflective light beam moving in a direction which is substantially orthogonal to the first direction. The mirror apparatus also includes an inertially coupled first driver circuitry for causing resonant pivoting about the first axis to provide the repetitive beam sweep or scanning. Suitable inertially coupled drive circuits include electrostatic driver circuits and piezoelectric drive circuits. There is also included a second drive for pivoting the mirror about the second axis, such as for example an electromagnetic drive circuit, such that sequential images or traces are spaced from each other. According to an alternate embodiment, a first single axis mirror is driven by an inertially coupled driver circuit to generate a resonant beam sweep and a second single axis mirror uses typical electromagnetic drive coils for controlling the orthogonal position of the resonant beam sweep.[0010]

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.[0011]

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:[0012]

FIG. 1 illustrates an example of a single axis resonant mirror having a support frame for generating a beam sweep, and FIG. 1A is a simplified cross-sectional view taken along lines AA of FIG. 1;[0013]

FIG. 2A is a top view of an alternate embodiment of a single axis torsional hinge mirror supported by a pair of hinge anchors rather than a support frame;[0014]

FIG. 2B is an illustration of an actual device of a single axis flat oval shaped mirror suitable for use with the present invention;[0015]

FIG. 3 is a perspective illustration of the use of two synchronized single axis mirrors such as shown in FIGS. 1, 2A and[0016]2B to generate the bi-directional resonant beam sweep across a display screen or a moving photosensitive medium according to the teachings of an embodiment of the present invention;

FIG. 3A illustrates one complete resonant beam sweep projected onto a moving photosensitive medium of a laser copier;[0017]

FIG. 3B illustrates a beam sweep path of a frame of image lines projected onto a display screen;[0018]

FIGS. 4A and 4B,[0019]5A and5B,6A and6B illustrate different arrangements for using inertially coupled electrostatic drive circuitry to generate the resonant scanning or pivoting about the torsional axis of a single axis mirror;

FIG. 7 illustrates the electrical connection between the electrostatic plates and the mirror assemblies of FIGS. 4A and 4B,[0020]5A and5B and6A and6B;

FIGS. 8A and 8B,[0021]9A and9B and10A and10B illustrate different arrangements for using piezoelectric drive circuit to generate the inertially coupled resonant scanning or pivoting about the first or resonant axis of a mirror;

FIG. 11 illustrates the electrical connection between the piezoelectric drive material and the mirror assemblies of FIGS. 8A and 8B,[0022]9A and9B, and10A and10B;

FIGS. 12 and 12A are perspective views of two embodiments of a two-axis torsional hinge mirror having a support frame for generating the bi-directional beam sweep according to the teachings of one embodiment of the present invention;[0023]

FIG. 13 is a top view of an alternate embodiment of a two-axis torsional hinge mirror supported by “hinge anchors” rather than a support frame;[0024]

FIGS.[0025]14A-14D are cross-sectional views of the mirror of FIG. 12 illustrating rotation or pivoting of the two sets of torsional hinges;

FIGS. 15A, 15B and[0026]15C illustrate the use of a two-axis resonant mirror such as shown in FIGS. 11 and 12 to generate a bi-directional beam sweep across a display screen or a moving photosensitive medium according to teachings of the present invention;

FIG. 16 is a perspective view illustrating the pattern of the bi-directional beam sweep and the resulting parallel beam images as may appear on a moving photosensitive medium or display screen;[0027]

FIGS. 17A and 17B are top and side views, respectively, illustrating electrostatic drive circuitry to generate the resonant scanning or pivoting about a first pair of torsional axis and the location of the electromagnetic drive circuitry for providing orthogonal positioning of the resonant beam sweep for a single dual axis mirror with a support frame;[0028]

FIGS. 18A and 18B are top and side views, respectively, illustrating piezoelectric drive circuitry to generate the resonant scanning or pivoting about a first pair of torsional axis and the location of the electromagnetic drive circuitry for providing orthogonal positioning of the resonant beam sweep for a single dual axis mirror using hinge anchors; and[0029]

FIG. 19 illustrates the electromagnetic drive circuit for moving the scanning light beam orthogonal to the raster scan for both the electrostatic resonant scan embodiment and the piezoelectric resonant scan embodiment.[0030]

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.[0031]

Like reference numbers in the figures are used herein to designate like elements throughout the various views of the present invention. The figures are not intended to be drawn to scale and in some instances, for illustrative purposes, the drawings may intentionally not be to scale. One of ordinary skill in the art will appreciate the many possible applications and variations of the present invention based on the following examples of possible embodiments of the present invention. The present invention relates to mirror apparatus with a moveable reflecting surface that has torsional hinges and is particularly suitable for use to provide the repetitive scans of a laser printer or the raster scan of a projection display device. The mirror apparatus of this invention includes a single two-axis resonant mirror according to one embodiment. A second embodiment uses one single axis resonant mirror in combination with a second single axis mirror for providing spaced and parallel scan lines. The second single axis mirror continuously adjusts the “vertical” movement of the beam with respect to the raster scan movement.[0032]

Referring now to FIG. 1, there is shown a top view of a mirror apparatus having a single pair of torsional hinges for pivoting around a[0033]

first axis

30. As shown, the mirror apparatus of FIG. 1 includes asupport member32 suitable for mounting to asupport structure34 as shown in FIG. 1A. FIG. 1A is a simplified cross-sectional view taken along line A-A of FIG. 1. A reflective surface ormirror portion36 is attached to supportmember32 by a pair of torsional hinges38A and38B

As will be discussed in more detail hereinafter, the mirror or[0034]

reflective surface portion

36 may be made to pivot or oscillate aboutaxis30 in response to various types of drive circuits. For example, the mirror apparatus may be driven to resonance for providing a repetitive beam sweep by electrostatic or piezoelectric drive circuits, or may by controlled much more directly to provide a slower orthogonal or vertical control to index each beam sweep to maintain spacing between successive lines on a projection display while at the same time maintaining all of the beam sweeps parallel to each other. Electromagnetic drive circuitry is particularly suitable for the vertical or orthogonal drive. When a mirror apparatus is to be used to control the orthogonal or vertical position of the beam sweep and is driven by an electromagnetic circuit, small magnets are typically included as indicated by dashed

line areas

40A and40B located on

tabs

42A and42B. The placement and use of the small magnets will be discussed in more detail with respect to FIGS. 14A through 14D. The magnets are mounted on the

tabs

42A and42B to avoid degrading thereflective surface36.

Although the mirror apparatus of FIG. 1 includes a support member or[0035]

frame

32, reflective surface ormirror portion36 may be manufactured by eliminating thesupport member32 and extending the torsional hinges38A and38B frommirror portion36 to a pair of hinge anchors44A and44B as shown in FIG. 2A. The hinge anchors are then attached or bonded to thesupport structure34 as shown in FIG. 1A. FIG. 2A also illustrates that the mirror orreflective surface portion36 may have any suitable shape or perimeter such as the hexagon shape indicated by dottedline46. Other suitable shapes may include oval, square or octagonal. For example, FIG. 2B illustrates an actual mirror found to be suitable for use in providing the resonant beam sweep. As can be seen, themirror portion36A is a very flat oval shape having a long dimension of about 5.5 millimeters and a short dimension of about 1.2 millimeters.

Referring to FIG. 3 there is a perspective illustration of an embodiment of the present invention using two mirrors, each of which pivot about a single axis, such as the single axis mirrors shown in FIGS. 1, 2A and[0036]2B. In addition, although FIGS. 1, 2A and2B illustrate a single axis mirror, two dual axis mirrors of the type shown in FIG. 12 and discussed hereinafter, can be used to obtain the same results as achieved by using two single axis mirrors. For example, two of the two-axis mirror arrangements shown in FIG. 12 may be used by not providing (or not activating) the drive mechanism for one of the axes. However, if two mirrors are to be used, it is believed to be advantageous to use two of the more rugged single axis mirrors such as shown in FIGS. 1, 2A and2B as discussed above.

Therefore, referring to FIG. 3, a first single axis analog torsional hinged mirror may be used in combination with a second similar single axis torsional mirror to solve the problems of a resonant scanning mirror type projection display or laser printer. As shown, there is a[0037]

first mirror apparatus

48 such as discussed above with respect to FIGS. 1, 2A and2B that includes asupport member32 supporting a mirror orreflective surface36 by the single pair of torsional hinges38A and38B. Thus, it will be appreciated that if themirror portion36 can be maintained in a resonant state by a drive source, the mirror can be used to cause a resonant oscillating light beam across a photosensitive medium. However, as will also be appreciated, there also needs to be a method of moving the light beam in a direction orthogonal to the oscillation if line images are to be maintained parallel. Therefore, as will be discussed with respect to FIG. 3, a second singleaxis mirror apparatus50, such as illustrated in FIGS. 1 and 2, may also used to provide the vertical movement of the light beam.

The system of the embodiment of FIG. 3 uses the first single[0038]

axis mirror apparatus

48 to provide the right to left, left to right resonant sweep as represented by

dotted lines

52A,52B,52N-l and52N. However, the up and down control of the beam trajectory is achieved by locating the second singleaxis mirror apparatus50 such that the reflective surface ormirror portion36A intercepts thelight beam54 emitted fromlight source56 and then reflects the intercepted light to themirror apparatus48 which is providing the resonant sweep motion.Line58 shown onmirror surface36 ofresonant mirror48 illustrates howmirror36A rotates around axis60 to move thelight beam54A up and down onreflective surface36 ofmirror apparatus48 during the left to right and right to left beam sweep so as to provide

parallel lines

52A,52B through52N-1 and52N on a projection display screen or a movingmedium62. Double headedarrow64 illustrates the vertical or orthogonal movement of the beam sweep projected frommirror surface36 ofmirror apparatus48.

Referring now to FIGS. 3A and 3B, there is shown an exaggerated schematic of the light beam trajectory responsive to movement about two axes during a complete resonant cycle of[0039]

mirror apparatus

48. As discussed above, the movement about two axes may be provided by two single axis mirrors as illustrated in FIG. 3 or a single dual axis mirror to be discussed later. The beam trajectory illustrated in FIG. 3A is shown with a photosensitive medium66 moving as indicated byarrow68 to illustrate how the beam trajectory generates parallel image lines for a laser copier during successive scan lines of a single resonant cycle. In the example shown in FIG. 3A, a right to left movement portion of the beam trajectory is identified by thereference number70. It should be understood that the term “beam trajectory” as used herein does not necessarily mean that the laser light is on or actually providing light. The term is used herein to illustrate the path that would be traced if the light was actually on at all times. As will be appreciated by those skilled in the art, the light source is typically turned on and off continuously due to modulation and is also typically switched off at the two ends (left and right) of a scan or sweep. However, the modulation pattern can vary from being on for the complete scan or sweep to being off for the complete scan. Modulation of the scanning beam, and switching off at the end portion of a scan is also, of course, true for all types of laser printers including laser printers which use a rotating polygon mirror. Therefore, in the embodiment shown in FIG. 3A, the laser beam is capable of providing modulated light at aboutpoint72 which is next to edge74 ofmedium66. However, as will be recognized, a printed page usually includes left and right margins. Therefore, although a printed image line could begin atpoint72 on a right to left scan of the beam trajectory as shown bytrajectory portion70, the modulated light beam does not actually start to produce an image untilpoint76 atmargin78 of the right to left portion of the trajectory and stops printing at theleft margin80. This is also indicated at therightmost dot82 on the printedimage line84. It is important to again point out that for a laser printer application thephotosensitive medium66 is moving in a direction as indicated byarrow68. Therefore, to generate the top printedimage line84 between

margins

78 and80 as a horizontal line, the right to left beam trajectory is orthogonally controlled bymirror assembly50 pivoting on torsional hinges86A and86B aboutaxis30A an appropriate amount so that the resulting line between the beginningright end point72 and theleft ending point82 is horizontal. That is, the beam trajectory is moved up during a beam sweep by substantially the same amount or distance as the constantly moving photosensitive medium66 moves up during the right to left beam sweep. After the right to left portion of the beam trajectory is complete at theleft edge88 of medium66 (i.e., half of the resonant cycle), the mirror is pivoted about torsional hinges86A and86B in the opposite direction as theresonant mirror36 changes the direction of its sweep as indicated byportion90 of the beam trajectory. Then, when the left toright portion92 of the trajectory beam sweep (resulting from pivoting aboutaxis30 on torsional hinges38A and38B or mirror apparatus48) again reaches theleft edge80 ofmedium66, the mirror is again pivoted about torsional hinges86A and86B to move the left toright portion92 of the beam trajectory upward as it traverses medium66 in a manner similar to the right to left portion of the trajectory. Thus, the line ofimage94 starting atbeginning point96 and generated during the left to right scan is maintained parallel to the previous generatedimage line84. Then as the beam trajectory passes theright edge74 of the medium66, the resonantscan mirror apparatus48 again begins to reverse its direction by pivoting in the opposite direction about torsional hinges38A and38B so as to return to thestarting point72. The cycle is then of course repeated for another complete resonant sweep such that two more image lines are produced.

FIG. 3B illustrates a similar beam pattern projected onto a display screen having an orthogonal dimension rather than onto the moving medium of a laser printer. As shown in FIG. 3B, the movement of the beam is the same as discussed with respect to FIG. 3A with respect to[0040]

portions

70 through92 of the beam sweep. However, after the beam trajectory passes theright edge78 of the display screen66A and begins to reverse its direction by pivoting in the opposite direction about hinges38A and38B, instead of returning to point72 an orthogonal incremental increase is added to index the trajectory, as indicated at98, the equivalent of one scan line so that the beginning point is now at72A rather than72. The resonant cycle then continues as before, except it is orthogonally incremented at the end of every cycle to a new starting point as indicated at

points

72B72C, etc. Once the trajectory has been incremented an amount equal to the full vertical display (i.e., completed a full display frame), the starting point is again repositioned at72 as indicated byreturn line100 and the full raster scan of a new frame begins.

Referring now to FIGS. 4A and 4B,[0041]5A and5B and6A and6B, there are shown top views and side views, respectively, for driving a single axis torsional hinge mirror, such asmirror36 of FIG. 3, into resonance. As shown, according to these embodiments, themirror apparatus102 includes asupport frame104 having two

long sides

106A and106B and two

short sides

108A and108B. The two

long sides

106A and106B are mounted or bonded to asupport structure110 by an adhesive or epoxy by means of stand-

offs

112A and112B. Also as shown in the side view of FIG. 4B,support structure110 defines acavity114. A mirror orreflective surface portion116 is attached to the two

short sides

108A and108B by a pair of torsional hinges118A and118B such that the mirror orreflective surface portion116 is located above thecavity114. As is clearly shown, the perimeter ofcavity114 is larger than the perimeter of reflective surface ormirror portion116 such thatmirror116 can freely rotate around torsional hinges118A and118B without hitting the bottom ofcavity114.

As mentioned above, electromagnetic drives have been successfully used to rotate torsional hinged supported[0042]

mirror

116 about theaxis120 through

hinges

118A and118B. Such electromagnetic drives may be used to set up resonance oscillation of themirror116 about its axis in a manner as will be discussed below, but are more useful for controlling the position of a second mirror such asmirror36A for orthogonally positioning the resonant beam sweep in response to varying signals provided by computational circuitry to be discussed later. Furthermore, such electromagnetic drives require the mounting of electromagnetic coils below the mirror thereby adding cost and taking up space. According to one embodiment of the present invention,mirror116 is caused to resonant about theaxis120 by electrostatic forces. Therefore, referring again to the embodiment of FIGS. 4A and 4B, there is included a pair of

electrostatic drive plates

122A and122B located below the

short sides

108A and108B ofsupport frame104. Also as shown in the side view of FIG. 4B, stand-off mounting

members

112A and112B are selected such that a

gap

124A and124B exists between the bottom surface of

short sides

108A and108B and the top surface of

electrostatic drive plates

122A and122B. It has been determined that selecting the thickness of the stand-off mounting112A and112B such that

gaps

124A and124B are between about 0.2 μm and 0.05 μm is particularly effective. An alternating voltage is then connected between themirror support structure104 and the

electrostatic plates

122A and122B.

As an example, and assuming the mirror is designed to have a resonant frequency about its torsional hinges that is no less than about 40 KHz when used as the scanning mirror of a display device, and between about 1 KHz and 4 KHz when used as the scanning mirror for a printer, if an alternating voltage also having a frequency substantially equivalent to the resonant frequency is connected across the electrostatic plates and the[0043]

support frame

104, the mirror will begin to oscillate at substantially the frequency of the applied voltage. The actual resonant frequency of a mirror can be determined by maintaining the voltage level constant and varying the frequency of the applied voltage between the two voltage limits. A frequency in which the mirror rotation is maximum, will be the resonant frequency. The oscillations of the mirror results from the vibrational forces generated by the “on/off” electrostatic forces between themirror support frame104 and the

electrostatic plates

122A and122B being inertially coupled to themirror116 through the torsional hinges118A and118B. The resonant frequency of the mirror varies not only according to the size of the mirror itself, but also according to the length, width and thickness of the two

torsional hinges

118A and118B. It should be noted that in the embodiment of FIG. 4A, the torsional hinges118A and118B are not attached to the midpoint of sides ofmirror portion116. That is, theaxis120 lying through the torsional hinges118A and118B does not divide themirror portion116 into two equal parts. As shown, the “bottom” portion of the illustration ofmirror116 is larger than the “top” portion. It will be appreciated, of course, that use of the terms “bottom” portion and “top” portion is for convenience in describing the device and has nothing to do with the actual positioning of the device. Although attaching the hinges “off center” may help initiate resonance in the structure by creating an imbalance, it has been determined that resonance of the mirror may be achieved almost as quickly if the mirror is not off center. Furthermore, stresses may well be reduced and the required energy to maintain resonance may be somewhat less with a balanced arrangement.

Referring now to FIGS. 5A and 5B, there is a top view and a side view, respectively, of an alternate embodiment for resonating[0044]

reflective portion

116 of themirror apparatus102. The components of the mirror structure of FIGS. 5A and 5B are substantially the same as those for FIGS. 4A and 4B discussed above. However, rather than mounting thesupport frame104 to thesupport structure110 at the center point of both

long side

118A and118B, one of the two short ends such as, for example,short end108A is mounted to supportstructure110 by a single large stand-off112C. A singleelectrostatic plate122B is then located at a very small spaced distance below the othershort end108B in the same manner as discussed above with respect to FIGS. 4A and 4B. An alternating voltage source is then connected between the mirror structure and the electrostatic plate in the same manner as discussed above. Themirror support frame104 will again vibrate in response to the on/off electrostatic attraction and the energy in turn is inertially coupled to thereflective portion116 which begins oscillating about torsional hinges118A and118B in the same manner as discussed above.

Still another embodiment is illustrated in top and side views FIG. 6A and FIG. 6B respectively. According to this embodiment, torsional hinges[0045]118A and118B do not extend from thereflective surface portion116 to a support frame, but instead extend to

enlarged anchor members

126A and126B.

End portions

128A and128B of the

anchors

126A and126B are located or mounted to thesupport structure110 by stand-

offs

112D and112E such that the

opposite end portions

130A and130B of each anchor are suspended or spaced above

electrostatic plates

132A and132B by a small gap. Thus, in the same manner as discussed above, an alternating voltage having a frequency substantially the same as the resonant frequency of themirror116 about is axis can be connected between the support anchors126A and126B and the

electrostatic plates

132A and132B to cause themirror116 to resonant and oscillate around the torsional hinges.

FIG. 7 is applicable to FIGS. 4A and 4B,[0046]5A and5B and6A and6B and illustrates the

electrical connections

133A and133B for applying an alternating voltage between the mirror structure and the electrostatic plates.

FIGS. 8A and 8B, FIGS. 9A and 9B, and FIGS. 10A and 10B illustrate resonant mirror arrangements mounted to the support structure in the same manner as discussed above with respect to FIGS. 4A and 4B, FIGS. 5A and 5B and FIGS. 6A and 6B respectively. However, rather than using electrostatic plates and electrostatic forces to generate resonant motion of the mirror around its torsional axis, these three embodiments employ slices of[0047]

piezoelectric material

134A,134B,134C and/or134D bonded to thesupport frame104 and/or anchors130A and130B. Thepiezoelectric material134A-134D is sliced such that it bends or curves when a voltage is applied across the length of the strip or slice of material. As will be understood by those skilled in the art, the response time for piezoelectric material will be very fast such that an alternating voltage will cause a strip of the material to bend and curve at the same frequency as the applied voltage. Therefore, since the material is bonded to thesupport frame104 or support anchors,130A and/or130B, the application of an alternating voltage having a frequency substantially equal to the resonance frequency of the mirror, will cause the vibration motion to be inertially coupled to thereflective portion116 and to thereby initiate and maintain the resonant oscillation as discussed above.

FIG. 11 illustrates the electrical connections for providing an alternating voltage to the mirror structure and the two ends of piezoelectric materials.[0048]

Therefore, it will be appreciated that the single axis mirror structure discussed above with respect to FIGS. 4A through 10B may be used as the[0049]

mirror structure

48 of FIG. 3 to provide the resonant sweep of the two single axis mirror arrangement discussed heretofore with respect to FIG. 3. Movement of thesecond mirror50 in the arrangement of FIG. 3 may be directly controlled to provide the necessary orthogonal movement by electromagnetic coils as also discussed above.

Referring now to FIG. 12, there is shown a perspective view of a single two-axis[0050]

bi-directional mirror assembly

140 which can be used to provide resonant scanning or beam sweeps across a projection display screen or moving photosensitive medium as well as adjusting the beam sweep in a direction orthogonal to the resonant oscillations of the reflective surface ormirror portion142 to maintain spaced parallel image lines produced by the resonant raster beam sweep. As shown,mirror assembly140 is illustrated as being mounted on asupport structure144. Themirror assembly140 may be formed from a single piece of substantially planar material and the functional or moving parts may be etched in the planar sheet of material (such as silicon) by techniques similar to those used in semiconductor art. As discussed below, the functional or moving components include, for example, theframe portion146, anintermediate gimbals portion148 and theinner mirror portion142. It will be appreciated that theintermediate gimbals portion148 is hinged to theframe portion146 at two ends by a first pair of torsional hinges150A and150B spaced apart and aligned along afirst axis152. Except for the first pair of

hinges

150A and150B, theintermediate gimbals portion148 is separated from theframe portion146.

The inner, centrally disposed[0051]

mirror portion

142 having a reflective surface centrally located thereon is attached togimbals portion148 at

hinges

154A and154B along asecond axis156 that is orthogonal to or rotated 90° from the first axis. The reflective surface onmirror portion142 is on the order of about 100-115 microns in thickness and is suitably polished on its upper surface to provide a specular or mirror surface. In order to provide necessary flatness, the mirror is formed with a radius of curvature greater than approximately 2 meters with increasing optical path lengths requiring increasing radius of curvature. The radius of curvature can be controlled by known stress control techniques such as by polishing on both opposite faces and deposition techniques for stress controlled thin films. If desired, a coating of suitable material can be placed on the mirror portion to enhance its reflectivity for specific radiation wavelengths.

FIG. 12A is an alternate embodiment of a dual axis mirror apparatus having an elongated[0052]

oval mirror portion

142A. Since the remaining elements of the mirror apparatus shown in FIG. 12A operate or function in the same manner as equivalent elements of FIG. 12, the two figures use common reference numbers.

Referring now to FIG. 13, there is shown another alternate embodiment of a dual axis mirror. In this embodiment, the outside support frame has been eliminated such that the torsional hinges[0053]150A and150B extend from the gimbals frame orportion148 to hinge

anchors

158A and158B. Hinge anchors158A and158B are of course used to mount or attach the mirror to a support structure such as discussed with respect to FIG. 12. It should also be appreciated that the operation of the dual torsional hinged mirror of FIG. 13 operates the same as the dual torsional hinged mirror discussed with respect to FIGS. 12 and 12A.

Referring to FIGS. 14, 14B,[0054]14C and14D along with any one of the mirrors illustrated in FIGS. 12, 12A and13, the motion of the dual axis mirror will be explained.Mirror assembly140 will be discussed with respect to inertially coupled driver circuits similar to those discussed above to generate the resonant scanning or beam sweep movement of themirror142 aboutaxis156 illustrated in FIGS. 14A and 14B. The use of such inertially coupled resonance with a single dual axis mirror will be discussed in detail hereinafter. FIGS. 14A and 14B represent a cross-section of the dual axis mirror of FIG. 12 taken along lines12A-12A (on axis152), and FIGS. 14C and 14D are cross-sections of FIG. 12 taken along lines12B-12B (on axis156).

Whereas the oscillating motion of the[0055]

reflective surface

142 is provided by resonant drive circuits, motion of thegimbals portion148 aboutaxis152 on the other hand, is provided by another type of driver circuits such as, for example, serially connected

electromagnetic coils

160A and160B, which are connected to computational or control circuitry for providing a control signal to provide a pair of electromagnetic forces for attracting and repelling thegimbals portion148. Thegimbals portion148 may also include a first pair of

permanent magnets

162A and162B mounted ongimbals portion148 along theaxis156 to enhance the operation of the electromagnetic coils. In order to symmetrically distribute mass about the two axes of rotation to thereby minimize oscillation under shock and vibration, each

permanent magnet

160A and160B preferably comprises an upper magnet set mounted on the top surface of thegimbals portion148 using conventional attachment techniques such as indium bonding and an aligned lower magnet similarly attached to the lower surface of thegimbals portion148 as shown in FIGS. 14A through 14D. The magnets of each set are arranged serially such as the north/south pole arrangement indicated in FIG. 14C. There are several possible arrangements of the four sets of magnets which may be used, such as all like poles up; or two sets of like poles up, two sets of like poles down; or three sets of like poles up, one set of like poles down, depending upon magnetic characteristics desired.

As will be discussed, pivoting about[0056]

axis

152 as shown in FIGS. 14C and 14D will provide the orthogonal scanning (or vertical) motion necessary to generate a series of spaced image lines parallel to each other. Thus, by mounting reflective surface ormirror portion142 onto togimbals portion148 via

hinges

154A and154B, resonant motion of the mirror portion relative to the gimbals portion occurs aboutaxis156 and the orthogonal sweep or motion occurs aboutaxis152.

The middle or neutral position of[0057]

mirror portion

142 is shown in FIG. 14A which is a section taken through the assembly along line12A-12A (or axis152) of FIG. 12. Rotation ofmirror portion142 aboutaxis156 independent ofgimbals portion148 and/orframe portion146 is shown in FIG. 14B as indicated byarrow162. FIG. 14C shows the middle position of themirror assembly140, similar to that shown in FIG. 14A, but taken along line12C-12C (or axis156) of FIG. 12. Rotation of the gimbals portion148 (which supports mirror portion142) aboutaxis152 independent offrame portion146 is shown in FIG. 14D as indicated by arrow164. The above arrangement allows independent rotation ofmirror portion142 about the two axes which in turn provides the ability to direct the scanning or raster movement of the light beam aboutaxis156 and the orthogonal sweep or movement aboutaxis152.

FIGS. 15A, 15B and[0058]15C illustrate the use of a dual orthogonal scanning resonant mirror according to one embodiment of the present invention for providing parallel image lines on a moving photosensitive medium such as adrum166 rotating aroundaxis168. The uppermost portions of FIGS. 15A, 15B and15C are simplified top views of a dual axis mirror for providing a beam sweep on medium orrotating drum166. The lowermost portion of the figure is a view looking at the medium166 in a direction as indicated byarrow170. As can be seen from FIGS. 15A and 15B, the operation of dual orthogonalscanning mirror assembly140 as it scans from right to left in the figures is substantially the same as a single axis mirror in that it is not necessary to provide orthogonal motion if the mirror is mounted at a slight angle. For example,point76 on FIG. 15A illustrates the starting point for producing an image line orrotating drum166 and FIG. 15B illustrates the path of the beam illustrated byline70 to produce animage line84 which is at a right angle to the movement ofdrum166. However, unlike a single axis resonant mirror and as shown in FIG. 15C, it is not necessary to turn off the laser (light beam) on the return scan, since a return or left toright scan92 in FIGS. 15A, 15B and15C can be continuously modulated so as to produce a printedimage line94 on the movingphotosensitive medium166. The second printed line ofimages94, according to the present invention, will be parallel to the previously produced line ofimages84 generated by the right to leftscan70 of the light beam. This is, of course, accomplished by slight pivoting of the mirror around thesecondary axis152 of the dual axis mirror as was discussed above.

The operation of the dual axis mirror with respect to a projection display screen[0059]164 may be better understood by referring to FIG. 16. As shown, alaser light source56 provides a coherent beam of light54 to the reflective surface ofmirror portion142 of dualaxis mirror apparatus140 which in turn reflects the beam of light onto adisplay screen62.Reflective surface142 is oscillating back and forth at a resonant frequency about torsional hinges154A and154B alongaxis156 and thereby sweeps the beam acrossdisplay screen62 alongimage line84 from location orpoint72 toend point82 as indicated byarrow172 in the light beam labeled54A-2. Theoscillating mirror142 then changes direction and at the same time the beam is moved or incremented orthogonally as indicated atpath174 to point176 and starts the return sweep as indicated byarrow178 to produceimage line94 between

points

176 and180. After passingpoint180, the beam again begins reversing direction and is again incremented to anew start point182 to begin another back and forth sweep. This process is repeated until thelast image line94N of a display frame ending atpoint184 is produced ondisplay screen62. The beam is then orthogonally moved fromend point184 to startpoint72 as indicated by dashedline186 to start a new display frame. As mentioned above,mirror portion142 is made to resonate to produce the repetitive beam sweep.

Referring now to FIGS. 17A and 17B, there is a simplified top view and side view of the mirror apparatus for generating both the resonant frequency sweeping movement and the orthogonal movement for beam positioning. In a manner discussed above with respect to FIGS. 4A through 6A, a[0060]

support frame

146 is mounted on asupport structure144 above acavity188 such that bothmirror portion142 andgimbals portion148 can rotate about their

respective axes

156 and152.Support frame146 is mounted at its

long sides

190A and190B on mounts or

spacing members

192A and192B such that the short ends194A and194B are spaced above

electrostatic drive plates

196A and196B by a small gap on the order of between about 0.2 μm and 0.05 μm. An alternating drive voltage having a frequency which is approximately the resonant frequency of themirror portion142 about its hinges, is then applied between the electrostatic drive plates and themirror supporting frame146 to generate vibrations in the mirror apparatus as was discussed above with respect to a single axis mirror and as was illustrated in FIG. 7. The energy of the vibration is inertially coupled through torsional hinges150A and150B togimbals portion148 and then through mirror hinges154A and154B to themirror portion142. This energy vibration at approximately the resonant frequency of the mirror causes themirror portion142 to begin resonant oscillations about

hinges

154A and154B alongaxis156 and can be used to provide the resonant beam sweep as discussed above. The orthogonal motion is controlled by

electromagnetic coils

198A and198B as shown in FIG. 17B and FIG. 19. As discussed above, permanent magnet sets200A and200B may be bonded to thegimbals portion148 to provide better stability and performance of the orthogonal drive. It should also be understood that although the energy inertially coupled tomirror portion142 sets the mirror oscillating at a full sweep and at a resonant frequency, the motion of the gimbals frame due to energy from the electrostatic plate is very slight such that the orthogonal movement can still be precisely controlled.

support frame

146 is mounted to supportstructure144 by

mounts

192A and192B as discussed above with respect to FIGS. 17A and 17B. However, instead of electrostatic plates, slices of

piezoelectric material

202A,202B,202C and202D are bonded to thesupport frame146. An alternating voltage having a frequency approximately the resonant frequency ofmirror portion142 about

torsional axis

154A and154B is applied between both ends of the slices of piezoelectric material as discussed above with respect to FIG. 11. In the same manner as discussed with respect to FIGS. 17A and 17B, vibrating energy of the mirror resonant frequency is inertially coupled from the frame to themirror portion142 so as to put the mirror into resonant oscillation. The resonant oscillation can then be used to provide the resonant beam sweep for a projection display or laser copier and an electromagnetic drive circuitry can be used to provide the necessary orthogonal motion.

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed as many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.[0062]

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.[0063]

Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.[0064]

Claims

What is claimed is:

1. Apparatus for providing a resonant beam sweep about a first axis, said apparatus comprising:

a mirror device integrally formed from a single piece of material comprising a reflective surface portion positioned to intercept a beam of light from a light source, and a first pair of torsional hinges attached to said reflective surface portion and extending to a support portion for pivoting said reflective surface portion about said first axis; and

a driver circuit for generating vibrational energy in said support portion and wherein said vibrational energy is inertially coupled from said support portion through said first pair of torsional hinges to said reflective surface portion such that said reflective surface portion oscillates about said first pair of torsional hinges between a selected lower limit below a resonant frequency and a selected upper limit above said resonant frequency.

2. The apparatus ofclaim 1 further comprising a support structure and wherein said support portion of said mirror device is a frame member having a first portion thereof attached to said support structure.

3. The apparatus ofclaim 1 wherein said support portion comprises first and second support anchors attached to a support structure.

4. The mirror device ofclaim 1 wherein said driver circuit comprises at least one electrostatic plate spaced a selected distance from said support portion and an alternating voltage source connected between said at least one electrostatic plate and said support portion and wherein the frequency of said alternating voltage source is between said selected lower limit and said selected upper limit.

5. The apparatus ofclaim 1 wherein said driver circuit comprises at least one portion of piezoelectric material having a first end and a second end, said portion of piezoelectric material bonded to said support portion and an alternating voltage source connected between said first end and said second end of said portion of piezoelectric material, and wherein the frequency of said alternating voltage source is between said selected lower limit and said selected upper limit.

6. The apparatus ofclaim 1 wherein said driver circuit comprises a pair of electromagnetic coils, one each of said pair located on each side of said first axis and spaced from said reflective surface portion, and an alternating voltage source connected across said pair of coils, and wherein the frequency of said alternating voltage source is between said selected lower limit and said selected upper limit.

7. The apparatus ofclaim 1 wherein said support portion of said mirror device comprises a support frame and a gimbals portion supported by a second pair of torsional hinges located at substantially a right angle with said first pair of hinges and extending to said support frame, said gimbals portion pivoting about a second axis orthogonal to said first axis.

8. The apparatus ofclaim 7 wherein said driver circuit comprises at least one electrostatic plate spaced a selected distance from said support frame and an alternating voltage source connected between said at least one electrostatic plate and said support frame and wherein the frequency of said alternating voltage source is between said selected lower limit and said selected upper limit.

9. The apparatus ofclaim 7 wherein said driver circuit comprises at least one portion of piezoelectric material having a first end and a second end, said portion of piezoelectric material bonded to said support frame and an alternating voltage source connected between said first end and said second end of said portion of piezoelectric material, and wherein the frequency of said alternating voltage source is between said selected lower limit and said selected upper limit.

10. The apparatus ofclaim 7 wherein said driver circuit comprises a pair of electromagnetic coils, one each of said pair located on each side of said first axis and spaced from said reflective surface portion, and an alternating voltage source connected across said pair of coils, said frequency of said alternating voltage source selected to be between said selected lower limit and said selected upper limit.

11. The apparatus ofclaim 8, and further comprising a pair of electromagnetic coils, one each of said pair located on each side of said second axis and spaced from said gimbals portion, and a voltage source connected across said pair of coils for selectively positioning said resonant beam sweep in a direction orthogonal to said beam sweep.

12. The apparatus ofclaim 9, and further comprising a pair of electromagnetic coils, one each of said pair located on each side of said second axis and spaced from said gimbals portion, and a voltage source connected across said pair of coils for selectively positioning said resonant beam sweep in a direction orthogonal to said beam sweep.

13. The apparatus ofclaim 10, and further comprising a second pair of electromagnetic coils, one each of said second pair located on each side of said second axis and spaced from said gimbals portion, and voltage source connected across said second pair of coils for selectively positioning said resonant beam sweep in a direction orthogonal to said beam sweep.

14. The apparatus ofclaim 1 wherein said support portion of said mirror device comprises a gimbals portion supported by a second pair of torsional hinges located at substantially right angles with said first pair of hinges and said second pair of torsional hinges extending one each to one of a pair of support anchors, said second pair of torsional hinges for pivoting about a second axis orthogonal to said first axis.

15. The apparatus ofclaim 14 wherein said driver circuit comprises at least one electrostatic plate spaced a selected distance from at least one of said pair of support anchors and an alternating voltage source connected between said at least one electrostatic plate and at least one of said pair of support anchors and wherein the frequency of said alternating voltage source is between said selected lower limit and said selected upper limit.

16. The apparatus ofclaim 14 wherein said driver circuit comprises at least one portion of piezoelectric material having a first end and a second end, said portion of piezoelectric material bonded to at least one of said pair of support anchors and an alternating voltage source connected between said first end and said second end of said portion of piezoelectric material, and wherein the frequency of said alternating voltage source is between said selected lower limit and said selected upper limit.

17. The apparatus ofclaim 14 wherein said driver circuit comprises a pair of electromagnetic coils, one end of said pair located on each side of said first axis and spaced from said reflective surface portion, and an alternating voltage source connected across said pair of coils and wherein the frequency of said alternating voltage source is between said selected lower limit and said selected upper limit.

18. The apparatus ofclaim 15, and further comprising a pair of electromagnetic coils, one each of said pair located on each side of said second axis and spaced from said gimbals portion, and a voltage source connected across said pair of coils for selectively positioning said resonant beam sweep in an orthogonal direction with respect to said beam sweep.

19. The apparatus ofclaim 16, and further comprising a pair of electromagnetic coils, one each of said pair located on each side of said second axis and spaced from said gimbals portion, and voltage source connected across said pair of coils for selectively positioning said resonant beam sweep in an orthogonal direction with respect to said beam sweep.

20. The apparatus ofclaim 17, and further comprising a second pair of electromagnetic coils, one each of said second pair located on each side of said second axis and spaced from said gimbals portion, and voltage source connected across said second pair of coils for selectively positioning said resonant beam sweep in an orthogonal direction with respect to said beam sweep.

21. Apparatus for providing a repetitive beam sweep, comprising:

a light source for providing a beam of light;

an integrally formed mirror device comprising a reflective surface portion positioned to intercept a beam of light, a first pair of torsional hinges and a gimbals portion pivotally attached to said reflective surface portion by said first pair of torsional hinges, a support member and a second pair of torsional hinges, said second pair of torsional hinges extending between said support member and said gimbals portion such that pivoting of said device about said first pair of torsional hinges results in said light beam reflected from said reflective surface defining a first plane and pivoting of said device about said second pair of torsional hinges results in said reflective light moving in a direction substantially orthogonal to said first path;

a first driver for generating vibrational energy in said support member of said mirror device and wherein said vibrational energy is inertially coupled through said second pair of torsional hinges to said gimbals portion and from said gimbals portion through said first pair of torsional hinges to said reflective surface portion for causing resonant pivoting in one direction about said first pair of said torsional hinges and then the opposite direction such that said reflected light beam sweeps or traces across a target area having a first dimension and a second dimension that is orthogonal to said first dimension, said reflected light beam sweeping along said first dimension of said target area as said mirror device pivots about said first pair of torsional hinges; and

a second driver for pivoting said mirror device about said second pair of torsional hinges such that consecutive beam sweeps across said target are repositioned substantially orthogonal with respect to said beam sweep.

22. The mirror device ofclaim 21 wherein said target area is a rotating cylindrical shaped photosensitive medium.

23. The mirror device ofclaim 21 wherein said target area is a display screen.

24. A printer comprising:

a light source providing a beam of light;

a first integrally formed device comprising a reflective surface portion positioned to intercept said beam of light, a support portion, and a first pair of torsional hinges attached to said reflective surface portion and extending to said support portion for resonant pivoting about a first axis such that light reflected from said reflective surface defines a first path;

a first drive circuit for generating vibrational energy in said support portion, said vibrational energy inertially coupled through said first pair of torsional hinges to said reflective surface portion to cause resonant pivoting of said first device about said first axis to provide a resonant beam sweep;

a second device for rotating about a second axis such that light from said reflective surface moves in a second direction substantially orthogonal to said first path;

a moving photosensitive medium having a first dimension and a second dimension orthogonal to said first dimension, and located to receive an image of said reflected light beam as said beam sweeps across said medium along said first dimension, said photosensitive medium moving in a direction along said second dimension such that subsequent traces are spaced apart; and

a second drive circuit for rotating said second device about said second axis such that traces are received on said moving photosensitive medium along a line substantially orthogonal to the movement of said photosensitive medium.

25. The printer ofclaim 24 wherein said first and second devices together comprise an integrally formed single dual axis mirror and wherein said support portion is a gimbals support pivotally attached to a support member by a second pair of torsional hinges and wherein said mirror of said first device is attached to said gimbals support by said first pair of torsional hinges.

26. The printer ofclaim 24 wherein said first device comprises a first single axis torsional hinged mirror and said second device comprises a second single axis torsional hinged mirror, said second device positioned to intercept said beam of light from said light source and reflect said light beam to said reflective surface of said first device.

27. The printer ofclaim 24 wherein said moving photosensitive medium is cylindrical shaped and rotates about an axis through the center of said cylinder.

28. A printer comprising:

a light source providing a beam of light;

an integrally formed mirror device comprising a reflective surface portion positioned to intercept said beam of light from said light source, a first hinge arrangement for supporting said reflective surface and for pivoting about a first axis, a gimbals portion and a second hinge arrangement, said gimbals portion attached to said first hinge arrangement and supported by said second hinge arrangement for pivoting about a second axis substantially orthogonal to said first axis such that pivoting of said device about said first axis results in light reflected from said reflective surface defining a first path, and pivoting of said device about said second axis results in said reflective light moving in a second direction substantially orthogonal to said first path;

a first driver for generating vibrational energy inertially coupled through said second hinge arrangement, said gimbals portion and through said first hinge arrangement to said reflective surface portion to cause resonant pivoting of said reflective surface in one direction about said first axis and then the opposite direction;

a moving photosensitive medium having a first dimension and a second dimension orthogonal to said first dimension, and located to receive an image of said reflected light beam as it sweeps or traces across said medium along said first dimension as said mirror device is resonantly pivoting about said first axis, said photosensitive medium moving in a direction along said second dimension such that an image of a subsequent trace of light is spaced from a previous trace; and

a second driver for pivoting about said second axis such that traces are received on said moving photosensitive medium along a line substantially orthogonal to the movement of said photosensitive medium.

29. The printer ofclaim 28 wherein said photosensitive medium is cylindrical shaped and rotates about an axis through the center of said cylinder.

30. The printer ofclaim 28 wherein said light bean traces on said medium are modulated in both directions such that said printer is a bi-directional printer.

31. A display device comprising:

a light source providing a beam of light;

a display screen having a first dimension and a second dimension orthogonal to said first dimension, and located to receive a multiplicity of modulated image lines of said reflected light beam as said beam sweeps across said display screen along said first dimension, each image line of said multiplicity being equally spaced from the preceding image line in a direction along said second dimension to generate an image frame; and

a second drive circuit for rotating said second device about said second axis such that said multiplicity of image lines are spaced across said display screen along a line substantially orthogonal to said resonant beam sweep.

32. The display device ofclaim 31 wherein said first and second devices together comprise an integrally formed single dual axis mirror and wherein said support portion of said first device and said support portion is a gimbals support pivotally attached to a support member by a second pair of torsional hinges and wherein said mirror of said first device is attached to said gimbals support by said first pair of torsional hinges.

33. The display device ofclaim 31 wherein said first device comprises a first single axis torsional hinged mirror and said second device comprises a second single axis torsional hinged mirror, said second device positioned to intercept said beam of light from said light source and reflect said light beam to said reflective surface of said first device.

34. A display device comprising:

a light source providing a beam of light;

an integrally formed mirror device comprising a reflective surface portion positioned to intercept said beam of light from said light source, a first hinge arrangement for supporting said reflective surface and for pivoting about a first axis, a gimbals portion and a second hinge arrangement, said gimbals portion attached to said first hinge arrangement and supported by a second hinge arrangement for pivoting about a second axis substantially orthogonal to said first axis such that pivoting of said device about said first axis results in light reflected from said reflective surface defining a first path, and pivoting of said device about said second axis results in said reflective light moving in a second direction substantially orthogonal to said first path;

a first driver for generating vibrational energy inertially coupled through said second hinge arrangement and through said first hinge arrangement to said reflective surface portion to cause resonant pivoting of said reflective surface in one direction about said first axis and then the opposite direction;

a display screen having a first dimension and a second dimension orthogonal to said first dimension, and located to receive a multiplicity of modulated image lines of said reflected light beam as it sweeps or traces across said display screen along said first dimension as said mirror device is resonantly pivoting about said first axis, each image line of said multiplicity being equally spaced from the preceding image line in a direction along said second dimension to generate an image frame; and

a second driver for pivoting about said second axis such that said multiplicity of image lines are spaced across said display screen along a line substantially orthogonal to said resonant beam sweep.

35. A method of providing an oscillating beam sweep across a target comprising the steps of:

providing a reflective surface pivotally attached to and integrally formed with a support portion by a first hinge arrangement, said reflective surface having a resonant frequency at which said surface pivotally resonates about said hinge arrangement;

reflecting a beam of light from said reflective surface;

locating said target to intercept said reflected beam of light; and

inertially coupling vibrational energy to said reflective surface to cause said reflective surface to pivotally resonate about said first hinge arrangement such that said reflected beam of light continuously sweeps back and forth across said target.

36. The method ofclaim 35 wherein said step of providing comprises the step of providing a reflective surface integrally formed with and pivotally attached to a support frame wherein a first portion of said support frame is also integrally formed with and attached to a support structure and said step of providing further comprising locating at least one electrostatic plate a selected distance form a second portion of said support frame and wherein said step of inertially coupling further comprises the step of connecting an alternating voltage between said electrostatic plate and said support frame to generate vibration in said support frame.

37. The method ofclaim 35 wherein said step of providing comprises the step of providing a reflective surface integrally formed with and pivotally attached to a pair of support anchors and attaching a first portion of each of said pair of support anchors to a support structure, and said step of providing further comprising locating at least one electrostatic plate a selected distance from a second portion of at least one of said pair of support anchors and wherein said step of inertially coupling further comprises the step of connecting an alternating voltage to said electrostatic plate and at least one of said support anchors. step of inertially coupling further comprises the step of connecting an alternating voltage to said electrostatic plate and at least one of said support anchors.

38. The method ofclaim 35 wherein said step of providing further comprises the steps of providing a reflective surface integrally formed with and pivotally attached to a support frame and wherein a first portion of said support frame is attached to a support structure, bonding a portion of piezoelectric material having a first end and a second end to a second portion of said support frame, wherein said step of inertially coupling further comprises connecting an alternating voltage to said first and said second end of said portion of piezoelectric material to generate vibrations in said support frame.

39. The method ofclaim 35 wherein said step of providing comprises the step of providing a reflective surface integrally formed with and pivotally attached to a pair of support anchors and attaching a first portion of each of said pair of support anchors to a support structure, and said step of providing further comprising bonding a portion of piezoelectric material having a first end and a second end to a second portion of at least one of said support anchors and wherein said step of inertially coupling further comprises connecting an alternating voltage to said first end and said second end of said portion of piezoelectric material to generate vibration in said support frame.

40. The method ofclaim 35 wherein said step of providing further comprises the step of locating a pair of electromagnetic coils on each side of said first axis and spaced from said reflective surface and wherein said step of inertially coupling further comprises connecting an alternating voltage across said pair of coils to generate vibration in said support frame.

41. The method ofclaim 35 wherein said step of providing comprises the steps of providing a reflective surface integrally formed with and pivotally attached to a gimbals portion by a first hinge arrangement for pivoting about a first axis, and further comprising pivotally attaching said gimbals portion to an integrally formed support member by a second hinge arrangement for pivoting about a second axis orthogonal to said first axis, and said method further comprising the step of pivoting said reflective surface about said second axis to orthogonally position said reflected bean of light as said reflected beam of light sweeps back and forth across said target.

42. The method ofclaim 35 wherein said step of providing further comprises the steps of locating at least one electrostatic plate a selected distance from a portion of said support member and connecting an alternating voltage to said electrostatic plate and said support member to generate vibration in said support member, and wherein said step of inertially coupling comprises the step of inertially coupling vibrational energy through said second hinge arrangement to said gimbals portion and from said gimbals portion through said first hinge arrangement to said reflective surface.

43. The method ofclaim 35 wherein said step of providing further comprises the steps of bonding a portion of piezoelectric material having a first end and a second end to said support member and connecting an alternating voltage to said first end and said second end of said portion of piezoelectric material to generate vibration in said support member, and wherein said step of inertially coupling comprises the step of inertially coupling vibrational energy through said second hinge arrangement to said gimbals portion and from said gimbals portion through said first hinge arrangement to said reflective surface.