Fixed focus optical system and DLP projector

Abstract

The utility model 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 along 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 utility model relates to the technical field of optics, in particular to a fixed-focus optical system and a DLP projector. Background Art

[0002] With the recent advancement of projection technology, projectors have become widely used in homes, education, and offices. DLP projectors, in particular, are gaining widespread adoption due to their longevity, high light efficiency, high reliability, wide color gamut, and compact size. The optical engine of a DLP projector can be divided into an illumination section and an imaging section, generally separated by a prism. The light path in front of the prism is the illumination section, while the prism and lens are the imaging section. The lens projects the image generated by the DMD onto the screen and determines the quality of the projected image. High-resolution DMDs require lenses with high resolution, and the projection lens must 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, which prevents them from being too small. The throw ratio of a projection lens equals throw distance divided by screen length. A smaller throw ratio allows for a larger image to be projected from a shorter distance, which requires a lens with a smaller focal length and a wider field of view to increase image magnification. However, a wider field of view results in greater distortion and reduced image quality at the edges of the field of view. Utility Model Content

[0004] The main purpose of the utility model 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 arranged opposite to each other along the optical axis, 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, which are arranged in sequence 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 refractive power of the twelfth lens is negative.

[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|<31mm,49mm<|f2|<50mm,61mm<|f3|<62mm,39mm<|f4|<40mm,66mm<|f5|<67mm,343mm<|f6|<344mm,35m m<|f7|<36mm, 11mm<|f8|<12mm, 25mm<|f9|<26mm, 63mm<|f10|<64mm, 33mm<|f11|<34mm, 3636mm<|f12|<3637mm.

[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 Abbe coefficient of the first lens is v1, the Abbe coefficient of the second lens is v2, the Abbe coefficient of the third lens is v3, the Abbe coefficient of the fourth lens is v4, the Abbe coefficient of the fifth lens is v5, the Abbe coefficient of the sixth lens is v6, the Abbe coefficient of the seventh lens is v7, the Abbe coefficient of the eighth lens is v8, the Abbe coefficient of the ninth lens is v9, the Abbe coefficient of the tenth lens is v10, the Abbe coefficient of the eleventh lens is v11, and the Abbe coefficient of the twelfth lens is v13. 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, and the interval between the ninth lens and the tenth lens is L9. A distance between the tenth lens and the eleventh lens is L10, a distance 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, which is disposed between the equivalent prism and the micromirror array and 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 arranged opposite to each other along an optical axis, and the fixed-focus optical system comprises 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, which are arranged in sequence 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 refractive power of the twelfth lens is negative.

[0039] The technical solution of the present invention is conducive to increasing the main ray angle of the marginal 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 trend of light, while introducing more light, making the structure more compact and realizing miniaturization; 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 following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 any creative work.

[0041] Figure 1 This is a structural schematic diagram of an embodiment of a fixed-focus optical system provided by the present utility model;

[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 polychromatic light diffraction of an embodiment of a medium fixed-focus optical system;

[0045] Figure 5 for Figure 1 Schematic diagram of the 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 stop; 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 embodiments described 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 making creative efforts shall fall 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 indications 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 for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of such features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which A and B are satisfied at the same time. 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 mutually contradictory or cannot be implemented, it should be deemed that such a 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, it's important to understand that focal power is equal to the difference between the image-side and object-side beam convergences, and it characterizes an optical system's ability to deflect light. The larger the absolute value of the focal power, the greater the light-bending ability; the smaller the absolute value, the weaker the light-bending ability. When the focal power is a positive number, the light is refracted in a convergent manner; when the focal power is a negative number, the light is refracted in a divergent manner. Focal power can be applied to characterize a specific refractive surface of a lens, a single lens, or a system composed of multiple lenses.

[0054] See also Figure 1 In one embodiment of the present utility model, the fixed-focus optical system 100 has an image side and an object side arranged opposite to each other along the optical axis, and 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, and the twelfth lens 12 has a convex image-side surface and a concave object-side surface. 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 set 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, it is possible to precisely control the incident light and thus display an image.

[0058] The technical solution of the present invention is conducive to increasing the angle of the chief ray of the marginal field of view by providing the first lens 1 with a negative optical focal length, which can effectively increase the field of view range; the second lens 2 with a negative optical focal length is arranged 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, so as 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 direction of light, introduce more light, and make the structure more compact, which can achieve miniaturization; by combining different lenses with each other and reasonably allocating the optical focal length, the lens has a wide 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 an 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 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. By combining different lenses and reasonably allocating their focal length ranges, the optical system has a wide viewing angle while improving the resolution of the fixed-focus optical system 100.

[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 tenth lens 12 is n13. The refractive index of the second lens 12 is n12, and the fixed-focus optical system 100 satisfies the following conditions: 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, and 1.78 < n12 < 1.79. By limiting the refractive index of each lens in the fixed-focus optical system 100, the refraction angle and path of light can be more precisely controlled, thereby ensuring that the light converges to the correct position and forms a clear, low-distortion image. This helps to improve the sharpness and color accuracy of the image.

[0061] In one embodiment of the present invention, the Abbe coefficient of the first lens 1 is v1, the Abbe coefficient of the second lens 2 is v2, the Abbe coefficient of the third lens 3 is v3, the Abbe coefficient of the fourth lens 4 is v4, the Abbe coefficient of the fifth lens 5 is v5, the Abbe coefficient of the sixth lens 6 is v6, the Abbe coefficient of the seventh lens 7 is v7, the Abbe coefficient of the eighth lens 8 is v8, the Abbe coefficient of the ninth lens 9 is v9, the Abbe coefficient of the tenth lens 10 is v10, the Abbe coefficient of the eleventh lens 11 is v11, and the Abbe coefficient of the twelfth lens 12 is v12. The fixed-focus optical system 100 satisfies the following conditions: 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;It is understandable that different colors of light will undergo different degrees of refraction when passing through the lens due to their different wavelengths, resulting in different focus positions, forming chromatic aberration, and affecting the clarity and color accuracy of the image. By limiting the chromatic aberration 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 edges can be clearer and the color transitions 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. The fixed-focus optical system 100 satisfies the following conditions: L10, the interval between the eleventh lens 11 and the twelfth lens 12 is L11, and the fixed-focus optical system 100 satisfies the following conditions: 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, and 0.5mm<L11<1mm. By controlling the intervals between the lenses, it is possible to avoid excessive intervals that are not conducive to the thinning of the fixed-focus optical system 100, and to avoid excessive intervals that affect assembly or increase the difficulty of 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 a 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 and astigmatism. 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 above parameters can be used to accurately set the shape and size of the lens aspheric surface, 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 12 can also reduce spherical aberration, further improving 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 system chromatic aberration, thereby improving imaging effects. Glass is less sensitive to temperature changes, and its shape and optical properties remain stable under temperature changes and are not easily deformed. Therefore, glass lenses can effectively resist the problem of lens deformation due to heat, maintain high lens precision for a long time, and thus improve 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 facilitated 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 transmits the maximum light, and has the best effect of improving projection brightness and contrast.

[0076] Specifically, in one embodiment of the present invention, the lens focal length is 12 mm, the field of view angle is 52°, and the throw ratio is 1.15:1. A smaller throw ratio can project a larger 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 diagram of this 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 0.05mm, 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 of this embodiment. Figure 5 The figure shows the MTF and field of view of this embodiment. When the fixed-focus optical system 100 is at a line pair frequency of 93lp / mm (i.e., a micromirror pitch of 5.4μm), the full-field MTF value 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 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 passes through the protective glass to the first lens and finally converges onto the projection screen to complete the projection.

[0084] The present invention also 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 embodiment. Since the DLP projector adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0085] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect application 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 oppositely arranged along the optical axis, 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, which are arranged in sequence 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. 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, and 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 v13. 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, and the fixed focus The optical system satisfies the following relationships: 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 L1. 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 further includes a protective glass, which is disposed 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, where F=2.

0.

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

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