Fixed focus optical system and DLP projector

Abstract

The invention discloses a fixed-focus optical system and a DLP projector, and relates to the technical field of optics, and the fixed-focus optical system is provided with an image side and an object side which are oppositely arranged in the direction of an optical axis. The system is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a diaphragm, a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, an equivalent prism and a micromirror array which are sequentially arranged from the image side to the object side. The fixed-focus optical system has the advantages of large visual angle, short focal length, high definition, low distortion and better imaging effect.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to a fixed-focus optical system and a DLP projector. Background Art

[0002] In recent years, with the development of projection technology, projectors have been widely used in home, education, office and other fields. Among them, DLP projectors are widely used due to their long life, high light efficiency, high reliability, wide color gamut and small size. The optical machine of the DLP projector can be divided into the lighting part and the imaging part. Generally, the prism is used as the boundary. The light path in front of the prism is the lighting part, and the prism and lens are the imaging part. The function of the lens is to project the image generated by the DMD onto the screen, which determines the quality of the projected image. High-resolution DMD needs to be used with a lens with clear resolution, and the projection lens needs to ensure a high MTF value at this line pair frequency.

[0003] Traditional LCD projectors have low light efficiency and brightness, and are limited by the size of the LCD screen, so the projector size cannot be made too small. The projection ratio of the projection lens = projection distance / screen length. A smaller projection ratio means that a larger screen can be projected at a shorter distance, which requires the lens to have a smaller focal length and a larger field of view to increase the magnification of the object image. A large field of view will produce greater distortion, and the image quality at the edge of the field of view will also decrease. Summary of the invention

[0004] The main purpose of the present invention is to provide a fixed-focus optical system, aiming to make the optical system have a large viewing angle, a short focal length and low distortion, and a better imaging effect.

[0005] To achieve the above-mentioned object, the present invention provides a fixed-focus optical system, wherein the fixed-focus optical system has an image side and an object side that are arranged opposite to each other along the optical axis direction, and the fixed-focus optical system is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, an aperture, a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, an equivalent prism, and a micromirror array that are sequentially arranged from the image side to the object side;

[0006] Wherein, the optical power of the first lens is negative;

[0007] The second lens has a negative optical power;

[0008] The third lens has a positive optical power;

[0009] The fourth lens has a positive optical power;

[0010] The fifth lens has a negative optical power;

[0011] The sixth lens has a positive optical power;

[0012] The seventh lens has a positive optical power;

[0013] The eighth lens has a negative optical power;

[0014] The ninth lens has a positive optical power;

[0015] The tenth lens has a positive optical power;

[0016] The eleventh lens has a positive optical power;

[0017] The twelfth lens has negative optical power.

[0018] In one embodiment, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, the focal length of the eighth lens is f8, the focal length of the ninth lens is f9, the focal length of the tenth lens is f10, the focal length of the eleventh lens is f11, and the focal length of the twelfth lens is f12, and the fixed-focus optical system satisfies the following relationship: mm< |f1| m< |f7|

[0019] In one embodiment, the refractive index of the first lens is n1, the refractive index of the second lens is n2, the refractive index of the third lens is n3, the refractive index of the fourth lens is n4, the refractive index of the fifth lens is n5, the refractive index of the sixth lens is n6, the refractive index of the seventh lens is n7, the refractive index of the eighth lens is n8, the refractive index of the ninth lens is n9, the refractive index of the tenth lens is n10, the refractive index of the eleventh lens is n11, and the refractive index of the twelfth lens is n12. n12, the fixed-focus optical system satisfies the following relationship: 1.72<n1<1.73, 1.67<n2<1.68, 1.55<n3<1.56, 1.78<n4<1.79, 1.84<n5<1.85, 1.62<n6<1.63, 1.62<n7<1.63, 1.84<n8<1.85, 1.49<n9<1.50, 1.62<n10<1.63, 1.78<n11<1.79, 1.78<n12<1.79.

[0020] In one embodiment, the dispersion coefficient of the first lens is v1, the dispersion coefficient of the second lens is v2, the dispersion coefficient of the third lens is v3, the dispersion coefficient of the fourth lens is v4, the dispersion coefficient of the fifth lens is v5, the dispersion coefficient of the sixth lens is v6, the dispersion coefficient of the seventh lens is v7, the dispersion coefficient of the eighth lens is v8, the dispersion coefficient of the ninth lens is v9, the dispersion coefficient of the tenth lens is v10, the dispersion coefficient of the eleventh lens is v11, and the dispersion coefficient of the twelfth lens is v12. The dispersion coefficient is v12, and the fixed-focus optical system satisfies the following relationship: 27.0<v1<29.0, 55.0<v2<56.0, 63.0<v3<64.0, 25.0<v4<26.0, 23.0<v5<24.0, 60.0<v6<61.0, 60.0<v7<61.0, 23.0<v8<24.0, 81.0<v9<82.0, 60.0<v10<61.0, 25.0<v11<26.0, 25.0<v12<26.0.

[0021] In one embodiment, the thickness of the first lens is h1, the thickness of the second lens is h2, the thickness of the third lens is h3, the thickness of the fourth lens is h4, the thickness of the fifth lens is h5, the thickness of the sixth lens is h6, the thickness of the seventh lens is h7, the thickness of the eighth lens is h8, the thickness of the ninth lens is h9, the thickness of the tenth lens is h10, the thickness of the eleventh lens is h11, and the thickness of the twelfth lens is h12. The fixed-focus optical system satisfies the following relationship: 14mm

[0022] ​In one embodiment, the interval between the first lens and the second lens is L1, the interval between the second lens and the third lens is L2, the interval between the third lens and the fourth lens is L3, the interval between the fourth lens and the fifth lens is L4, the interval between the fifth lens and the sixth lens is L5, the interval between the sixth lens and the aperture is L60, the interval between the aperture and the seventh lens is L07, the interval between the seventh lens and the eighth lens is L7, the interval between the eighth lens and the ninth lens is L8, the interval between the ninth lens and the tenth lens is L9, and the The interval between the tenth lens and the eleventh lens is L10, the interval between the eleventh lens and the twelfth lens is L11, and the fixed-focus optical system satisfies the following relationship: 4mm<L1<5mm, 11mm<L2<12mm, 5mm<L3<6mm, 3mm<L4<4mm, 9mm<L5<10mm, 1mm<L60<2mm, 0≤L07<0.5mm, 0≤L7<0.2mm, 0≤L8<0.05mm, 0.5mm<L9<1mm, 0.5mm<L10<1.5mm, 0.5mm<L11<1mm.

[0023] In one embodiment, the second lens and the twelfth lens are glass aspherical lenses, and the first lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens and the eleventh lens are glass spherical lenses.

[0024] In one embodiment, the fixed-focus optical system further includes a protective glass, and the protective glass is disposed between the equivalent prism and the micromirror array and is disposed close to the micromirror array.

[0025] In one embodiment, the aperture value of the fixed-focus optical system is F, where F=2.0.

[0026] The present invention further provides a DLP projector, comprising a fixed-focus projection optical system, wherein the fixed-focus optical system has an image side and an object side that are arranged opposite to each other along an optical axis direction, and the fixed-focus optical system is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a stop, a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, an equivalent prism, and a micromirror array that are sequentially arranged from the image side to the object side;

[0027] Wherein, the optical power of the first lens is negative;

[0028] The second lens has a negative optical power;

[0029] The third lens has a positive optical power;

[0030] The fourth lens has a positive optical power;

[0031] The fifth lens has a negative optical power;

[0032] The sixth lens has a positive optical power;

[0033] The seventh lens has a positive optical power;

[0034] The eighth lens has a negative optical power;

[0035] The ninth lens has a positive optical power;

[0036] The tenth lens has a positive optical power;

[0037] The eleventh lens has a positive optical power;

[0038] The twelfth lens has negative optical power.

[0039] The technical solution of the present invention is conducive to increasing the main ray angle of the edge field of view by setting the first lens with negative optical focal length, which can effectively increase the field of view range; the second lens with negative optical focal length is set at a position with a larger light beam aperture, and an aperture is provided between the sixth lens and the seventh lens, so that the aperture is located in the middle position of the system, which is used to adjust the light flux according to actual conditions, reduce distortion, and improve imaging quality; by comprehensively setting the optical focal length of each lens, the lens can well control the light trend, while introducing more light, making the structure more compact, and miniaturization can be achieved; by combining different lenses with each other and reasonably allocating optical focal length, it has a large viewing angle, a short focal length and low distortion, and a better imaging effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0041] Figure 1 A schematic structural diagram of an embodiment of a fixed-focus optical system provided by the present invention;

[0042] Figure 2 for Figure 1 A schematic diagram of a vertical axis chromatic aberration curve of an embodiment of a medium fixed focus optical system;

[0043] Figure 3 for Figure 1 A schematic diagram of field distortion of an embodiment of a medium fixed-focus optical system;

[0044] Figure 4 for Figure 1 A schematic diagram of the MTF of diffraction of complex light of an embodiment of a medium fixed focus optical system;

[0045] Figure 5 for Figure 1 Schematic diagram of MTF and field of view of an embodiment of a medium fixed focus optical system.

[0046] Description of Figure Numbers:

[0047] 100. Fixed-focus optical system; 1. first lens; 2. second lens; 3. third lens; 4. fourth lens; 5. fifth lens; 6. sixth lens; 7. seventh lens; 8. eighth lens; 9. ninth lens; 10. tenth lens; 11. eleventh lens; 12. twelfth lens; 13. aperture; 14. equivalent prism; 15. protective glass; 16. micromirror array.

[0048] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0051] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0052] The present invention provides a fixed-focus optical system 100 .

[0053] First of all, it is important to understand that the focal power is equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam, and it characterizes the ability of the optical system to deflect light. The larger the absolute value of the focal power, the stronger the ability to bend light, and the smaller the absolute value of the focal power, the weaker the ability to bend light. When the focal power is a positive number, the refraction of light is convergent; when the focal power is a negative number, the refraction of light is divergent. The focal power can be used to characterize a certain refractive surface of a lens, a certain lens, or a system formed by multiple lenses.

[0054] See also Figure 1 In one embodiment of the present invention, the fixed-focus optical system 100 has an image side and an object side which are arranged opposite to each other along the optical axis direction. The fixed-focus optical system 100 is composed of a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, an aperture 13, a seventh lens 7, an eighth lens 8, a ninth lens 9, a tenth lens 10, an eleventh lens 11, a twelfth lens 12, an equivalent prism 14 and a micromirror array 16 which are arranged in sequence from the image side to the object side, wherein the first lens 1 has a negative focal power, the second lens 2 has a negative focal power, the third lens 3 has a positive focal power, the fourth lens 4 has a positive focal power, the fifth lens 5 has a negative focal power, the sixth lens 6 has a positive focal power, the seventh lens 7 has a positive focal power, the eighth lens 8 has a negative focal power, the ninth lens 9 has a positive focal power, the tenth lens 10 has a positive focal power, the eleventh lens 11 has a positive focal power, and the twelfth lens 12 has a negative focal power.

[0055] Specifically, the first lens 1 has a convex image side surface and a concave object side surface, the second lens 2 has a convex image side surface and a concave object side surface, the third lens 3 has a concave image side surface and a convex object side surface, the fourth lens 4 has a convex image side surface and a concave object side surface, the fifth lens 5 has a convex image side surface and a concave object side surface, the sixth lens 6 has a concave image side surface and a convex object side surface, the seventh lens 7 has a concave image side surface and a convex object side surface, the eighth lens 8 has a concave image side surface and a concave object side surface, the ninth lens 9 has a convex image side surface and a convex object side surface, and the tenth lens 10 has a convex image side surface and a concave object side surface. The eleventh lens 11 has a convex image side surface and a convex object side surface, the twelfth lens 12 has a convex image side surface and a concave object side surface, and by such an arrangement, the first lens 1 has a negative optical power, the second lens 2 has a negative optical power, the third lens 3 has a positive optical power, the fourth lens 4 has a negative optical power, the fifth lens 5 has a positive optical power, the sixth lens 6 has a negative optical power, the seventh lens 7 has a positive optical power, the eighth lens 8 has a positive optical power, the ninth lens 9 has a positive optical power, the tenth lens 10 has a positive optical power, the eleventh lens 11 has a positive optical power, and the twelfth lens 12 has a negative optical power.

[0056] In addition, it should be noted that in this embodiment, the equivalent prism 14 is configured as a right-angle prism, so that the fixed-focus optical system 100 can better receive the light from the optical machine lighting module, increase the brightness of the fixed-focus optical system 100, and deflect the optical axis by 90° to facilitate adjustment of the optical path.

[0057] The micromirror array 16 is an optical element composed of a large number of micromirrors. By controlling the tilt angle of each micromirror, the incident light can be precisely controlled, thereby realizing image display.

[0058] The technical solution of the present invention is conducive to increasing the main ray angle of the edge field of view by setting the first lens 1 with negative optical focal length, which can effectively increase the field of view range; the second lens 2 with negative optical focal length is set at a position with a larger light beam aperture, and an aperture 13 is provided between the sixth lens 6 and the seventh lens 7, so that the aperture 13 is located in the middle position of the system, which is used to adjust the light flux according to actual conditions, reduce distortion, and improve imaging quality; by comprehensively setting the optical focal length of each lens, the lens can control the light trend well, introduce more light and make the structure more compact, and can achieve miniaturization; by combining different lenses with each other and reasonably allocating the optical focal length, it has a large viewing angle, a short focal length and low distortion, and a better imaging effect.

[0059] In one embodiment of the present invention, it should be understood that the focal length refers to the distance from the rear surface of the lens to the image plane in the optical system. The focal length determines the magnification and viewing angle of the image. The optical power is the reciprocal of the focal length. The focal length of the first lens 1 is f1, the focal length of the second lens 2 is f2, the focal length of the third lens 3 is f3, the focal length of the fourth lens 4 is f4, the focal length of the fifth lens 5 is f5, the focal length of the sixth lens 6 is f6, the focal length of the seventh lens 7 is f7, the focal length of the eighth lens 8 is f8, the focal length of the ninth lens 9 is f9, the focal length of the tenth lens 10 is f10, the focal length of the eleventh lens 11 is f11, and the focal length of the twelfth lens 12 is f12. The fixed-focus optical system The system 100 satisfies the following requirements: 30mm<|f1|<31mm, 49mm<|f2|<50mm, 61mm<|f3|<62mm, 39mm<|f4|<40mm, 66mm<|f5|<67mm, 343mm<|f6|<344mm, 35mm<|f7|<36mm, 11mm<|f8|<12mm, 25mm<|f9|<26mm, 63mm<|f10|<64mm, 33mm<|f11|<34mm, 3636mm<|f12|<3637mm; through the mutual combination of different lenses and the reasonable allocation of the focal length range, the optical system has a large viewing angle and the resolution of the fixed-focus optical system 100 is improved.

[0060] In one embodiment of the present invention, the refractive index of the first lens 1 is n1, the refractive index of the second lens 2 is n2, the refractive index of the third lens 3 is n3, the refractive index of the fourth lens 4 is n4, the refractive index of the fifth lens 5 is n5, the refractive index of the sixth lens 6 is n6, the refractive index of the seventh lens 7 is n7, the refractive index of the eighth lens 8 is n8, the refractive index of the ninth lens 9 is n9, the refractive index of the tenth lens 10 is n10, the refractive index of the eleventh lens 11 is n11, and the refractive index of the twelfth lens 12 is n13. The refractive index of lens 12 is n12, and the fixed-focus optical system 100 satisfies: 1.72<n1<1.73, 1.67<n2<1.68, 1.55<n3<1.56, 1.78<n4<1.79, 1.84<n5<1.85, 1.62<n6<1.63, 1.62<n7<1.63, 1.84<n8<1.85, 1.49<n9<1.50, 1.62<n10<1.63, 1.78<n11<1.79, 1.78<n12<1.79. By limiting the refractive index of each lens of the fixed-focus optical system 100, the refraction angle and path of the light can be more finely controlled, thereby ensuring that the light converges to the correct position to form a clear, low-distortion image. This helps to improve the sharpness and color accuracy of the picture.

[0061] In one embodiment of the present invention, the dispersion coefficient of the first lens 1 is v1, the dispersion coefficient of the second lens 2 is v2, the dispersion coefficient of the third lens 3 is v3, the dispersion coefficient of the fourth lens 4 is v4, the dispersion coefficient of the fifth lens 5 is v5, the dispersion coefficient of the sixth lens 6 is v6, the dispersion coefficient of the seventh lens 7 is v7, the dispersion coefficient of the eighth lens 8 is v8, the dispersion coefficient of the ninth lens 9 is v9, the dispersion coefficient of the tenth lens 10 is v10, the dispersion coefficient of the eleventh lens 11 is v11, and the dispersion coefficient of the twelfth lens 12 is v12, and the fixed-focus optical system 100 satisfies: 2 7.0<v1<29.0,55.0<v2<56.0,63.0<v3<64.0,25.0<v4<26.0,23.0<v5<24.0,60.0<v6<61.0,60.0<v7<61.0,23.0<v8<24.0,81.0<v9<82.0,60.0<v10<61.0,25.0<v11<26.0,25.0<v12<26.0;It can be understood that different colors of light will be refracted to different degrees when passing through the lens due to their different wavelengths, resulting in different focusing positions, forming chromatic aberration, and affecting the clarity and color accuracy of the image. By limiting the dispersion coefficient of each lens of the fixed-focus optical system 100, the refractive index differences of light of various wavelengths can be effectively balanced, chromatic aberration can be reduced, and the image edge can be clearer and the color transition can be natural. Please refer to Figure 2 In one embodiment of the present invention, the vertical axis chromatic aberration corresponding to the maximum field of view can be less than 2.5 μm, which has a good imaging effect.

[0062] In one embodiment of the present invention, the thickness of the first lens 1 is h1, the thickness of the second lens 2 is h2, the thickness of the third lens 3 is h3, the thickness of the fourth lens 4 is h4, the thickness of the fifth lens 5 is h5, the thickness of the sixth lens 6 is h6, the thickness of the seventh lens 7 is h7, the thickness of the eighth lens 8 is h8, the thickness of the ninth lens 9 is h9, the thickness of the tenth lens 10 is h10, the thickness of the eleventh lens 11 is h11, and the thickness of the twelfth lens 12 is h12. The fixed-focus optical system 100 satisfies: 14mm

[0063] In one embodiment of the present invention, the interval between the first lens 1 and the second lens 2 is L1, the interval between the second lens 2 and the third lens 3 is L2, the interval between the third lens 3 and the fourth lens 4 is L3, the interval between the fourth lens 4 and the fifth lens 5 is L4, the interval between the fifth lens 5 and the sixth lens 6 is L5, the interval between the sixth lens 6 and the aperture 13 is L60, the interval between the aperture 13 and the seventh lens 7 is L07, the interval between the seventh lens 7 and the eighth lens 8 is L7, the interval between the eighth lens 8 and the ninth lens 9 is L8, the interval between the ninth lens 9 and the tenth lens 10 is L9, and the interval between the tenth lens 10 and the eleventh lens 11 is L10. L10, the interval between the eleventh lens 11 and the twelfth lens 12 is L11, and the fixed-focus optical system 100 satisfies: 4mm<L1<5mm, 11mm<L2<12mm, 5mm<L3<6mm, 3mm<L4<4mm, 9mm<L5<10mm, 1mm<L60<2mm, 0≤L07<0.5mm, 0≤L7<0.2mm, 0≤L8<0.05mm, 0.5mm<L9<1mm, 0.5mm<L10<1.5mm, 0.5mm<L11<1mm. By controlling the intervals between the lenses, it is possible to avoid too large an interval that is not conducive to the thinning of the fixed-focus optical system 100 and too small an interval that affects assembly or increases the difficulty in manufacturing.

[0064] ​In one embodiment of the present invention, the second lens 2 and the twelfth lens 12 are glass aspherical lenses, and the first lens 1, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, the eighth lens 8, the ninth lens 9 and the eleventh lens 11 are glass spherical lenses;

[0065] It can be understood that the characteristics of aspherical lenses are: the curvature changes continuously from the center of the lens to the periphery of the lens. Unlike spherical lenses with constant curvature from the center of the lens to the periphery of the lens, aspherical lenses have better curvature radius characteristics and have the advantages of improving distortion aberration and improving astigmatism aberration. After using aspherical lenses, the aberrations that occur during imaging can be eliminated as much as possible, thereby improving the imaging quality of the lens.

[0066] Specifically, in one embodiment of the present invention, the surface shape of the aspheric lens in the projection optical system should satisfy the following equation:

[0067]

[0068] Among them, c is the curvature corresponding to the radius, r is the radial coordinate (its unit is the same as the lens length unit), k is the conic quadratic curve coefficient, a1, a2, a3, and a4 represent the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients respectively.

[0069] More specifically, in one embodiment of the present invention, the curvature radius and even-order coefficient of each aspheric surface are shown in Table 1 below.

[0070] Table 1

[0071]

[0072] The shape and size of the aspheric surface of the lens can be accurately set through the above parameters, and the aspheric second lens 2 is far away from the aperture 13. Setting it at a position with a larger beam aperture angle can calibrate distortion. At the same time, the aspheric lens twelve can also reduce spherical aberration and further improve the imaging quality of the system.

[0073] The first lens 1, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7, the eighth lens 8, the ninth lens 9, the tenth lens 10 and the eleventh lens 11 are glass spherical lenses with very high surface finish, thereby reducing light scattering and reflection, reducing various optical aberrations, and effectively suppressing the chromatic aberration of the system to improve the imaging effect. Glass is less sensitive to temperature changes, and its shape and optical properties remain stable under temperature changes and are not easily deformed. Therefore, the glass lens can well resist the problem of lens deformation due to heat and maintain the high precision of the lens for a long time, thereby improving the stability of the fixed-focus optical system 100.

[0074] In addition, since only two aspherical lenses are used and the rest are spherical lenses, processing is easy and costs are reduced.

[0075] In one embodiment of the present invention, the aperture value of the fixed-focus optical system 100 is F, wherein F=2.0; the lens has the largest light transmission and the best effect of improving projection brightness and contrast.

[0076] Specifically, in one embodiment of the present invention, the focal length of the lens is 12 mm, the field of view angle is 52°, and the projection ratio is 1.15:1. A smaller projection ratio can project a larger size image at a short distance. The parameters of the fixed-focus optical system 100 are shown in Table 2 below.

[0077] Table 2

[0078]

[0079]

[0080] Figure 3 The figure shows the field distortion schematic diagram of the present embodiment, wherein the maximum field optical distortion is about 0.6%, which is converted into a maximum TV distortion of only 0.2%, the field curvature is less than 0.05 mm, and the image clarity is relatively uniform.

[0081] See also Figure 4-5 In one embodiment of the present invention, Figure 4 The figure shows the MTF diagram of the complex light diffraction in this embodiment. Figure 5 The MTF and field of view of this embodiment are shown in FIG. 1 . When the fixed-focus optical system 100 is at a line pair frequency of 93 lp / mm (i.e., a micromirror spacing of 5.4 μm), the MTF value of the entire field of view is greater than 65%. Figure 2-5 It can be seen that the fixed-focus optical system 100 provided in this embodiment has good imaging capability.

[0082] In one embodiment of the present invention, the fixed-focus optical system 100 further includes a protective glass 15 , which is disposed between the equivalent prism 14 and the micromirror array 16 and is disposed close to the micromirror array 16 , thereby providing effective protection for the micromirror array 16 .

[0083] It can be understood that the light carrying the image information is emitted from the micromirror array, sequentially from the protective glass to the first lens and finally converges onto the projection screen to complete the projection.

[0084] The present invention further proposes a DLP projector, which includes a fixed-focus optical system 100. The specific structure of the fixed-focus optical system 100 refers to the above-mentioned embodiment. Since the DLP projector adopts all the technical solutions of all the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

[0085] The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A fixed-focus optical system, characterized in that: The fixed-focus optical system has an image side and an object side that are arranged opposite to each other along the optical axis direction, and the fixed-focus optical system is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, an aperture, a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, an equivalent prism, and a micromirror array that are sequentially arranged from the image side to the object side; Wherein, the optical power of the first lens is negative; The second lens has a negative optical power; The third lens has a positive optical power; The fourth lens has a positive optical power; The fifth lens has a negative optical power; The sixth lens has a positive optical power; The seventh lens has a positive optical power; The eighth lens has a negative optical power; The ninth lens has a positive optical power; The tenth lens has a positive optical power; The eleventh lens has a positive optical power; The twelfth lens has negative optical power.

2. The fixed-focus optical system according to claim 1, wherein: The focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, the focal length of the fifth lens is f5, the focal length of the sixth lens is f6, the focal length of the seventh lens is f7, the focal length of the eighth lens is f8, the focal length of the ninth lens is f9, the focal length of the tenth lens is f10, the focal length of the eleventh lens is f11, and the focal length of the twelfth lens is f12, and the fixed-focus optical system satisfies the following relationship: 30mm<| f1| |f7|<36mm, 11mm<|f8|<12mm, 25mm<|f9|<26mm, 63mm<|f10|<64mm, 33mm<|f11|<34mm, 3636mm<|f12|<3637mm.

3. The fixed-focus optical system according to claim 1, wherein: The refractive index of the first lens is n1, the refractive index of the second lens is n2, the refractive index of the third lens is n3, the refractive index of the fourth lens is n4, the refractive index of the fifth lens is n5, the refractive index of the sixth lens is n6, the refractive index of the seventh lens is n7, the refractive index of the eighth lens is n8, the refractive index of the ninth lens is n9, the refractive index of the tenth lens is n10, the refractive index of the eleventh lens is n11, and the refractive index of the twelfth lens is n12. The fixed-focus optical system satisfies the following relationship: 1.72<n1<1.73, 1.67<n2<1.68, 1.55<n3<1.56, 1.78<n4<1.79, 1.84<n5<1.85, 1.62<n6<1.63, 1.62<n7<1.63, 1.84<n8<1.85, 1.49<n9<1.50, 1.62<n10<1.63, 1.78<n11<1.79, 1.78<n12<1.

79.

4. The fixed-focus optical system according to claim 1, wherein: The dispersion coefficient of the first lens is v1, the dispersion coefficient of the second lens is v2, the dispersion coefficient of the third lens is v3, the dispersion coefficient of the fourth lens is v4, the dispersion coefficient of the fifth lens is v5, the dispersion coefficient of the sixth lens is v6, the dispersion coefficient of the seventh lens is v7, the dispersion coefficient of the eighth lens is v8, the dispersion coefficient of the ninth lens is v9, the dispersion coefficient of the tenth lens is v10, the dispersion coefficient of the eleventh lens is v11, and the dispersion coefficient of the twelfth lens is v12. The number is v12, and the fixed-focus optical system satisfies the following relationship: 27.0<v1<29.0, 55.0<v2<56.0, 63.0<v3<64.0, 25.0<v4<26.0, 23.0<v5<24.0, 60.0<v6<61.0, 60.0<v7<61.0, 23.0<v8<24.0, 81.0<v9<82.0, 60.0<v10<61.0, 25.0<v11<26.0, 25.0<v12<26.

0.

5. The fixed-focus optical system according to claim 1, wherein: The thickness of the first lens is h1, the thickness of the second lens is h2, the thickness of the third lens is h3, the thickness of the fourth lens is h4, the thickness of the fifth lens is h5, the thickness of the sixth lens is h6, the thickness of the seventh lens is h7, the thickness of the eighth lens is h8, the thickness of the ninth lens is h9, the thickness of the tenth lens is h10, the thickness of the eleventh lens is h11, the thickness of the twelfth lens is h12, the fixed focus The optical system satisfies the following relationship: 14mm<h1<15mm, 6mm<h2<7mm, 10mm<h3<11mm, 5mm<h4<5.5mm, 4mm<h5<4.5mm, 5mm<h6<6mm, 1mm<h7<1.5mm, 5mm<h8<5.5mm, 2.5mm<h9<3mm, 2.5mm<h10<3mm, 5mm<h11<5.5mm, 3.5mm<h12<4mm.

6. The fixed-focus optical system according to claim 1, wherein: The interval between the first lens and the second lens is L1, the interval between the second lens and the third lens is L2, the interval between the third lens and the fourth lens is L3, the interval between the fourth lens and the fifth lens is L4, the interval between the fifth lens and the sixth lens is L5, the interval between the sixth lens and the aperture is L60, the interval between the aperture and the seventh lens is L07, the interval between the seventh lens and the eighth lens is L7, the interval between the eighth lens and the ninth lens is L8, the interval between the ninth lens and the tenth lens is L9, and the tenth lens is L10. The interval between the eleventh lens and the twelfth lens is L10, the interval between the eleventh lens and the twelfth lens is L11, and the fixed-focus optical system satisfies the following relationship: 4mm<L1<5mm, 11mm<L2<12mm, 5mm<L3<6mm, 3mm<L4<4mm, 9mm<L5<10mm, 1mm<L60<2mm, 0≤L07<0.5mm, 0≤L7<0.2mm, 0≤L8<0.05mm, 0.5mm<L9<1mm, 0.5mm<L10<1.5mm, 0.5mm<L11<1mm.

7. The fixed-focus optical system according to claim 1, wherein: The second lens and the twelfth lens are glass aspherical lenses, and the first lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens and the eleventh lens are glass spherical lenses.

8. The fixed-focus optical system according to claim 1, wherein: The fixed-focus optical system also includes a protective glass, which is arranged between the equivalent prism and the micromirror array and close to the micromirror array.

9. The fixed-focus optical system according to claim 1, wherein: The aperture value of the fixed-focus optical system is F, wherein F=2.

0.

10. A DLP projector, characterized in that: Comprising the fixed-focus optical system as described in claims 1-9.

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