Disclosure of Invention
Based on the problems, the invention provides the long-focus projection lens and the system which have the advantages of small volume, small projection ratio, low cost, good thermal stability, small distortion, short back adhesive distance and low assembly difficulty.
The invention provides a long-focus projection lens, which comprises a refraction system and a light valve, wherein the refraction system comprises 9 lenses and 1 aperture diaphragm, and the refraction system is sequentially arranged from the light valve to the refraction system: a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens and a ninth lens; the third lens, the fourth lens and the fifth lens are combined to form a three-cemented lens, the aperture diaphragm is arranged between the fifth lens and the sixth lens, and the aperture diaphragm is positioned in the middle of the whole refraction system.
Furthermore, the first lens and the second lens are both meniscus-shaped glass spherical lenses, and the first lens and the second lens are the same optical axis and are attached to one side with large curvature.
Further, the three-cemented lens is used for correcting chromatic aberration, wherein the third lens and the fifth lens are distributed with negative focal power, the fourth lens is distributed with positive focal power, and abbe numbers of the third lens and the fifth lens are in a range of 20-50.
Further, the sixth lens and the seventh lens are glass spherical lenses, the eighth lens and the ninth lens are plastic aspherical lenses, the eighth lens is a biconcave lens, and the ninth lens is a meniscus lens bent towards the light source.
Further, the powers of the first lens to the ninth lens are sequentially configured to: negative, positive, negative, and negative, the entire system being positive optical power.
Further, the distance from the light valve to the first lens is L1, and the total length of the refraction system is L2, which meets the following condition: 0.05< L1/L2<1.
The long-focus projection system adopts the long-focus projection lens, and an image offset mirror and an illumination prism are further arranged between the long-focus projection lens and the light valve.
Further, the distance from the image offset mirror to the first lens is the rear working distance of the lens, denoted as BFL, which meets the following conditional expression: 9< L1/BFL <30.
Further, the illumination prism adopts a TIR total reflection prism.
Compared with the prior art, the application has the following beneficial effects:
the part of the long-focus projection lens, which is close to the optical machine, uses the glass sphere, so that the sensitivity of the whole system is low, and the sensitivity of the plastic aspherical surface is reduced by controlling the opposite shape, so that the sensitivity of the whole system is low and the assembly difficulty is low;
because the temperature of the optical machine is higher, the lenses close to the optical machine system are all glass lenses, and the thermal expansion coefficients of the lenses at each position are matched, so that the sensitivity of the whole system to the temperature is reduced, the temperature drift is reduced, and the thermal stability is improved;
the technical scheme of the invention has simple integral structure, and realizes simple assembly, smaller volume and high-resolution imaging quality through the aperture diaphragm, the spherical lens, the cemented lens and reasonable material collocation.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. It should be apparent that the described embodiments are only some embodiments of the present invention and not all embodiments of the present invention, and it should be understood that the present invention is not limited by the example embodiments described herein. Based on the embodiments of the invention described in the present application, all other embodiments that a person skilled in the art would have without inventive effort shall fall within the scope of the invention.
Example 1
The invention provides the long-focus projection lens which has the advantages of small volume, small projection ratio, low cost, good thermal stability, small distortion, short back glue distance and low assembly difficulty.
Referring to fig. 1, the invention provides a tele projection lens, which comprises a refraction system 1 and a light valve 2, wherein the refraction system 1 comprises 9 lenses and 1 aperture diaphragm 3, and the refraction system 1 is sequentially arranged from the light valve 2 to the refraction system 1: a first lens 11, a second lens 12, a third lens 13, a fourth lens 14, a fifth lens 15, a sixth lens 16, a seventh lens 17, an eighth lens 18, and a ninth lens 19; wherein the third, fourth and fifth lenses are combined to form a three-cemented lens, the aperture stop 3 is arranged between the fifth lens 15 and the sixth lens 16, and the aperture stop 3 is positioned in the middle of the whole refraction system 1.
Further, the refraction system 1 comprises 7 glass spherical lenses and 2 plastic aspherical lenses, the aperture diaphragm 3 is positioned in the middle of the whole refraction system 1, the lens arrangement in the refraction system 1 presents an approximately symmetrical structure relative to the aperture diaphragm 3, the structure is very beneficial to aberration correction, and the three-cemented lens plays a key role in system axial chromatic aberration and vertical chromatic aberration correction.
Further, the three cemented lens is a core element, and the aberration correction is performed by reasonably selecting glass materials and optical power distribution to effectively balance aberration and workability, the three cemented lens is mainly used for correcting chromatic aberration, and preferably a material with a larger abbe number difference is selected for matching, wherein the abbe number or the abbe number Vd of the third lens 13 is selected to be as close as possible to the abbe number of the fifth lens, about 20-50, the value in practical application is 29.5, the third lens and the fifth lens distribute negative optical power, the fourth lens 14 distributes positive optical power, and the fourth lens 14 can select a material with a smaller refractive index. By matching the refractive index nd, abbe number or dispersion coefficient vd, thermal expansion coefficient cte and curvature R value of the third, fourth and fifth lenses, aberration in the whole system can be reduced, and imaging quality can be improved.
The distance from the light valve 2 to the first lens 11 is called as a back glue distance, in a common projection system, the back glue distance is about 10-20mm, and the problem of poor light uniformity exists. On one hand, the back adhesive distance of the lens system is L1, the total length of the refraction system 1 is L2, and the lens system meets the requirement of 0.05< L1/L2<1; on the other hand, the invention reasonably selects the shape, parameters and positions of the lenses, and has good correcting effect on the aberration entering the lens, the lens shapes of the first lens 11 and the second lens 12 are meniscus glass spherical lenses, the lens shapes are the same optical axis, and the two sides with large curvatures of the two lenses are attached, so that the matching can have good light receiving effect on a large angle, and meanwhile, the first lens 11 and the second lens 12 are matched by selecting two materials with larger differences of refractive index and Abbe number, so that the aberration entering the lens has good correcting effect. The two measures can obtain the projection lens with long back glue distance and correct aberration better.
Further, the sixth lens and the seventh lens are glass spherical lenses, and are used for receiving light rays passing through the aperture diaphragm 3, balancing aberration of the whole system and completing large-size imaging by matching with a subsequent lens.
Further, the eighth lens and the ninth lens are plastic aspheric lenses, the eighth lens and the ninth lens are far away from the optical machine and have weak temperature relative sensitivity, so that the plastic aspheric lenses are generally adopted, the eighth lens 18 is a biconcave lens, the ninth lens 19 is a meniscus lens bent towards the light source, and the two lenses are used for diffusing the light rays with small angles at the front, so that large-size projection is shown on a screen, and because the lens is far away from the aperture diaphragm 3, the field of view is large, the distortion aberration of the system is reduced by adopting the aspheric surface, and the imaging quality is improved.
Further, the focal power of the lens in the optical system can directly influence astigmatism, field curvature, distortion, axial chromatic aberration and vertical chromatic aberration, so that different positive and negative focal power collocations can play a certain role in aberration correction; the focal power of the lens is sequentially distributed as follows: negative, positive, negative; in the present invention, the whole system is of positive power (positive diopter is a basic condition for enabling imaging).
Further, the structural parameters of the tele projection lens meet the following conditions: effective Focal Length (EFL) = 13.857mm, resolution 93lp/mm, projection screen 58-120 inches, transmittance 1.2.
Example 2
The invention also provides a long-focus projection system, which adopts the long-focus projection lens as in any one of the embodiment 1, an image offset lens 4 and an illumination prism 5 are arranged between the long-focus projection lens and the light valve 2, the illumination prism 5 adopts a TIR total reflection prism, wherein the long-focus projection lens mainly comprises a refraction system 1, the refraction system 1 comprises 9 lenses and 1 aperture diaphragm 3, and the directions from the light valve 2 to the refraction system 1 are sequentially: a first lens 11, a second lens 12, a third lens 13, a fourth lens 14, a fifth lens 15, a sixth lens 16, a seventh lens 17, an eighth lens 18, and a ninth lens 19; wherein the third, fourth and fifth lenses are combined to form a three-cemented lens, the aperture stop 3 is arranged between the fifth lens 15 and the sixth lens 16, and the aperture stop 3 is positioned in the middle of the whole refraction system 1.
Further, the light valve 2 is a DMD chip or an LCos chip, the light valve 2 is a light modulation element, and the TIR total reflection prism is used for improving brightness and contrast of light entering the lens from the light valve 2; the distance from the image offset mirror 4 to the first lens 11, i.e. the rear working distance of the lens, is denoted BFL, which corresponds to the following conditional expression: 9< L1/BFL <30 to satisfy the ultra-short focal characteristics of the lens.
Referring to fig. 2-6, which show the imaging quality of three wavelengths of light (0.45 um, 0.55um, 0.62 um), wherein the abscissa represents the logarithm of the line, and the ordinate represents the resolution, wherein the higher the value of the ordinate is, the stronger the resolution is, the higher the image quality reduction degree is, and as can be seen from fig. 2-6, the mtf (Modulation Transfer Function) is greater than 0.5, and the imaging quality is very clear.
Fig. 7 is a schematic view showing TV distortion of an image formed by the projection system of this embodiment, and from the schematic data, it can be seen that the maximum TV distortion is 0.10% and less than the normal required value of 0.5% when the projection image is 70 inches.
Fig. 8 is a schematic diagram of spot point on the screen under different view field conditions on the imaging frame of the embodiment, wherein the schematic diagram is that three kinds of light rays (0.45 um, 0.55um, 0.62 um) with different wavelengths are respectively imaged on the spot on the screen under a certain view field condition on the premise of different normalized view field conditions, and parameters RMS and GEO respectively represent root mean square and geometric radius of the spot, and as can be seen from the figure, the two are less than 3 times of relation, the overall tolerance capability is better, meanwhile, the values of the two are very small, and the performance of the system is good.
Fig. 9 is a schematic diagram of vertical axis chromatic aberration in this embodiment, where Line1, line2, and Line3 represent three different wavelengths of light, the wavelength relationship is that Line1< Line2< Line3, fig. 9 represents the cheap amounts of Line1 and Line3 relative to the center wavelength (Line 2) under different view field conditions, which generally requires less than 0.5 pixel, and the vertical axis chromatic aberration in the figure is within the diffraction limit, beyond the capability of human eyes to distinguish, and the chromatic aberration of the whole system is small.
Compared with the prior art, the long-focus projection lens and the system provided by the invention have the following characteristics:
1) The volume is small, the total lens length is only 89mm, and the maximum caliber of the lens is 30mm;
2) The cost is low, and the lens framework uses 7 spherical lenses and 2 plastic aspheric surfaces;
3) The projection ratio is small, and the projection ratio is 1.2;
4) The heat stability is good, the heat deficiency and the focus phenomenon is not obvious under the higher temperature of the whole group of lenses, and especially when the temperature deviation of the whole group is not more than 5 ℃, the heat stability is good;
5) The distortion is small, and the distortion of TV is less than 0.1%;
6) The back glue distance is long and can reach 26mm.
The technical scheme of the invention has simple integral structure, and realizes the imaging quality with simple assembly, smaller volume and high resolution through the aperture diaphragm 3, the spherical lens, the cemented lens and reasonable material collocation.
Although the illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the above illustrative embodiments are merely illustrative and are not intended to limit the scope of the present invention thereto. Various changes and modifications may be made therein by one of ordinary skill in the art without departing from the scope and spirit of the invention. All such changes and modifications are intended to be included within the scope of the present invention as set forth in the appended claims.
In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
Similarly, it should be appreciated that in order to streamline the invention and aid in understanding one or more of the various inventive aspects, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof in the description of exemplary embodiments of the invention. However, the method of the present invention should not be construed as reflecting the following intent: i.e., the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention. It will be understood by those skilled in the art that all of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and all of the processes or units of any method or apparatus so disclosed, may be combined in any combination, except combinations where the features are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.
Furthermore, those skilled in the art will appreciate that while some embodiments described herein include some features but not others included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments may be used in any combination.
It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The use of the words first, second, third, etc. do not denote any order. These words may be interpreted as names.
The foregoing description is merely illustrative of specific embodiments of the present invention and the scope of the present invention is not limited thereto, and any person skilled in the art can easily think about variations or substitutions within the scope of the present invention. The protection scope of the invention is subject to the protection scope of the claims.