Fixed focus projection optical system

Abstract

The utility model discloses a kind of fixed focus projection optical systems, it is related to optical technology field, wherein, the fixed focus projection optical system has opposite arrangement along optical axis direction object side and image side, the fixed focus projection optical system includes by the object side to the image side sequentially arranged micro mirror array, equivalent prism, galvanometer, first lens group, second lens group, plane mirror, curved mirror;Wherein, the plane mirror and the curved mirror are respectively arranged in the optical axis both sides, the plane mirror is arranged with the optical axis and is included angle, and one end intersects with the optical axis;The first lens group power is positive, the second lens group power is positive, and the second lens group can move along the optical axis, to make the fixed focus projection optical system zoom, by the twice reflection of the utility model using plane mirror and curved mirror, greatly reduce the length of projection direction, reduce system volume.

Description

Technical Field

[0001] This utility model relates to the field of optical technology, and in particular to a fixed-focus projection optical system. Background Technology

[0002] In recent years, with the development of projection technology, ultra-short-throw projectors have been widely used in home applications. Because they can project large images from a short distance, they are gradually replacing traditional televisions.

[0003] Currently, ultra-short throw projection lenses on the market mainly adopt a structure of refractive lens group plus single reflective mirror group, which is often quite long. Utility Model Content

[0004] The main objective of this invention is to propose a fixed-focus projection optical system, aiming to provide a small-volume fixed-focus projection optical system.

[0005] To achieve the above objectives, this utility model proposes a fixed-focus projection optical system, which has an object side and an image side arranged opposite to each other along the optical axis. The fixed-focus projection optical system includes a micromirror array, an equivalent prism, a galvanometer, a first lens group, a second lens group, a plane mirror, and a curved mirror arranged sequentially from the object side to the image side.

[0006] The planar reflector and the curved reflector are respectively disposed on both sides of the optical axis. The planar reflector is set at an angle to the optical axis, and one end of it intersects the optical axis.

[0007] The first lens group has a positive optical power, the second lens group has a negative optical power, and the second lens group can move along the optical axis to enable the fixed-focus projection optical system to focus when the projection distance changes.

[0008] In one embodiment, the first lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an aperture stop, and an eighth lens arranged sequentially from the object side to the image side, wherein the first lens has positive optical power, the second lens has positive optical power, the third lens has positive optical power, the fourth lens has negative optical power, the fifth lens has positive optical power, the sixth lens has negative optical power, the seventh lens has positive optical power, and the eighth lens has positive optical power; and / or,

[0009] The second lens group includes a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a thirteenth lens arranged sequentially from the object side to the image side, wherein the optical power of the ninth lens is positive, the optical power of the tenth lens is positive, the optical power of the eleventh lens is negative, the optical power of the twelfth lens is negative, and the optical power of the thirteenth lens is negative.

[0010] In one embodiment, the optical power of the first lens group is φ 100 The optical power of the second lens group is φ 200 The optical power of the curved reflector is φ 400 The optical power satisfies:

[0011] 0.04≤|φ 100 |≤0.06, 0.003≤|φ 200 |≤0.01, 0.04≤|φ 400 |≤0.08.

[0012] In one embodiment, the optical power of the first lens group is φ 100 The optical power of the second lens group is φ 200 The ratio of the optical power of the first lens group to the optical power of the second lens group satisfies:

[0013] 7≤|φ 100 / φ 200 |≤11.

[0014] In one embodiment, the first lens has an optical power of φ1, the second lens has an optical power of φ2, and the sum of the optical powers of the third, fourth, and fifth lenses is φ. 345 The sum of the optical power of the sixth lens and the seventh lens is φ. 67 The eighth lens has an optical power of φ8; the ninth lens has an optical power of φ9; the sum of the optical powers of the tenth and eleventh lenses is φ. 1011 The optical power of the twelfth lens is φ. 12 The optical power of the thirteenth lens is φ. 13 The optical power of each lens satisfies:

[0015] 0.01≤|φ1|≤0.03, 0.04≤|φ2|≤0.07, 0.002≤|φ 345 |≤0.05, 0.01≤|φ 67 |≤0.04, 0.02≤|φ8|≤0.05, 0.01≤|φ9|≤0.04, 0.01≤|φ 1011 |≤0.04, 0.01≤|φ 12 |≤0.04, 0.02≤|φ 13 |≤0.06.

[0016] In one embodiment, the first lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an aperture stop, and an eighth lens arranged sequentially from the object side to the image side; the second lens group includes a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a thirteenth lens arranged sequentially from the object side to the image side.

[0017] The distance between the center of the thirteenth lens and the center of the plane mirror is T1, the distance between the center of the plane mirror and the center of the curved mirror is T2, and the distance T13 between the center of the first lens and the center of the thirteenth lens 13 satisfies:

[0018] 0.5≤T13 / (T1+T2)≤0.9.

[0019] In one embodiment, the first lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an aperture stop, and an eighth lens arranged sequentially from the object side to the image side;

[0020] The distance from the first lens to the intersection of the plane mirror and the optical axis along the optical axis is T00, and the distance from the micromirror array to the first lens is T11. The ratio of T00 to T11 satisfies:

[0021] T00 / T11≤4.5.

[0022] In one embodiment, the first lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an aperture stop, and an eighth lens arranged sequentially from the object side to the image side; the second lens group includes a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a thirteenth lens arranged sequentially from the object side to the image side.

[0023] The second, eighth, and ninth lenses are glass aspherical lenses, while the twelfth, thirteenth lenses, and curved reflector are plastic aspherical lenses.

[0024] In one embodiment, the first lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an aperture stop, and an eighth lens arranged sequentially from the object side to the image side; the second lens group includes a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a thirteenth lens arranged sequentially from the object side to the image side.

[0025] The third lens, the fourth lens, and the fifth lens are cemented together; the sixth lens is cemented together with the seventh lens; and the tenth lens is cemented together with the eleventh lens.

[0026] In one embodiment, the optical axis angle between the plane mirror and the refracting mirror group is 45°.

[0027] In this invention, the image beam originates from a micromirror array and passes sequentially through a protective glass, an equivalent prism, a galvanometer, a first lens group, and a second lens group. When the beam reaches the plane mirror, it is reflected by the plane mirror to the curved mirror, and then reflected again by the curved mirror to the projection screen, thereby changing the direction of the light path and shortening the length of the projection direction. The plane mirror and the curved mirror form a first image, which is then reflected back to the projection screen to form a second image. When the size / projection ratio of the projected image needs to be changed, the second lens group moves along the optical axis to focus the fixed-focus projection optical system. Through the rational arrangement of the structure and position of the first lens group (with positive optical power), the second lens group (with negative and positive optical power), the plane mirror, and the curved mirror, the plane mirror and the curved mirror reflect the beam twice, greatly reducing the length of the projection direction and enabling the fixed-focus projection optical system to have a small size. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0029] Figure 1 A schematic diagram of a structure of an embodiment of the fixed-focus projection optical system provided by this utility model;

[0030] Figure 2 for Figure 1 Optical path diagram of a fixed-focus projection optical system;

[0031] Figure 3 for Figure 1 MTF performance of a fixed-focus projection optical system with a projection size of 68 feet;

[0032] Figure 4 for Figure 1 A schematic diagram of distortion when the projection size of a fixed-focus projection optical system is 68 feet.

[0033] Figure 5 for Figure 1 MTF diagram of a fixed-focus projection optical system at a projection size of 150 feet;

[0034] Figure 6 for Figure 2 A schematic diagram of the MTF of a fixed-focus projection optical system when the projection size is 40 feet.

[0035] Explanation of icon numbers:

[0036] 1000, Fixed-focus projection optical system; 100, First lens group; 200, Second lens group; 300, Plane mirror; 400, Curved mirror; 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; Thirteenth lens; a, Micromirror array; b, Protective glass; c, Equivalent prism; d, Galvanometer; e, Aperture stop.

[0037] The realization of the purpose, functional features and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0038] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present utility model.

[0039] It should be noted that if the embodiments of this utility model involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0040] Furthermore, if the embodiments of this utility model involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0041] To solve the above problems, this utility model proposes a fixed-focus projection optical system 1000.

[0042] First, it's understandable that optical power equals the difference between the convergence of the image-side beam and the convergence of the object-side beam; it characterizes the ability of an optical system to deflect light. The larger the absolute value of the optical power, the stronger its ability to bend light; the smaller the absolute value, the weaker its ability to bend light. When the optical power is positive, the refraction of light is converging; when the optical power is negative, the refraction of light is diverging. Optical power can be used to characterize a single refractive surface of a lens (i.e., one surface of the lens), a single lens, or a system of multiple lenses (i.e., a lens group).

[0043] Please see Figure 1 In one embodiment of this utility model, the fixed-focus projection optical system 1000 has an object side and an image side arranged opposite to each other along the optical axis. The fixed-focus projection optical system 1000 includes a micromirror array a, an equivalent prism c, a galvanometer d, a first lens group 100, a second lens group 200, a plane mirror 300, and a curved mirror 400 arranged sequentially from the object side to the image side. The plane mirror 300 and the curved mirror 400 are respectively disposed on both sides of the optical axis. The plane mirror 300 is arranged at an angle to the optical axis, and one end intersects the optical axis. The first lens group 100 has a positive optical power, the second lens group 200 has a positive optical power, and the second lens group 200 can move along the optical axis to enable the fixed-focus projection optical system to focus when the projection distance changes.

[0044] It should be noted that the micromirror array a is an optical element composed of a large number of micro mirrors. By controlling the tilt angle of each micro mirror, precise control of the incident light can be achieved, thereby enabling image display.

[0045] Furthermore, in one embodiment of this utility model, the fixed-focus optical system further includes a protective glass b, which is disposed between the equivalent prism c and the micromirror array a, and is located close to the micromirror array a, thereby providing effective protection for the micromirror array a.

[0046] In the technical solution of this utility model, the image beam is emitted from the micromirror array a, and passes sequentially through the protective glass b, the equivalent prism c, the galvanometer d, the first lens group 100, and the second lens group 200. When the beam reaches the plane mirror 300, the plane mirror 300 reflects the beam to the curved mirror 400, and then the curved mirror 400 reflects the beam to the projection screen, thereby changing the direction of the light path and shortening the length of the projection direction. The plane mirror 300 and the curved mirror 400 perform a first image formation, and the plane mirror 300 and the curved mirror 400 reflect the first image to the projection screen. The projection screen forms a second image; when it is necessary to change the size / projection ratio of the projected image, the second lens group 200 moves along the optical axis toward the image side, so that the fixed-focus projection optical system 100 is focused; through the reasonable arrangement of the structure and position of the first lens group 100 with positive optical power, the second lens group 200 with negative positive optical power, the plane mirror 300 and the curved mirror 400, the plane mirror 300 and the curved mirror 400 reflect the light beam twice, which greatly reduces the length of the projection direction, so that the fixed-focus projection optical system 1000 has a small volume.

[0047] Specifically, in one embodiment of this utility model, the first lens group 100 includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7, an aperture stop e, and an eighth lens 8 arranged sequentially from the object side to the image side. The first lens 1 has a positive optical power, the second lens 2 has a positive 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, and the eighth lens 8 has a positive optical power. By setting the positive optical power... The first lens 1, with a convex side, is beneficial for increasing the principal ray angle at the edge of the field of view, effectively expanding the field of view range. An aperture stop e is provided between the seventh lens 7 and the eighth lens 8, positioning the aperture stop e in the middle of the system. This allows for adjustment of the luminous flux according to actual conditions, reducing distortion and improving image quality. By comprehensively setting the optical power of each lens, this fixed-focus projection optical system 1000 can effectively control the light path, introducing more light while making the structure more compact and miniaturized. Through the combination of different lenses and the reasonable allocation of optical power, it features a wide viewing angle, short focal length, and low distortion, resulting in better imaging effects.

[0048] Furthermore, in one embodiment of this utility model, the second lens group 200 includes a ninth lens 9, a tenth lens 10, an eleventh lens 11, a twelfth lens 12, and a thirteenth lens 13 arranged sequentially from the object side to the image side. The optical power of the ninth lens 9 is positive, the optical power of the tenth lens 10 is positive, the optical power of the eleventh lens 11 is negative, the optical power of the twelfth lens 12 is negative, and the optical power of the thirteenth lens 13 is negative. By comprehensively setting the optical power of each lens, the fixed-focus projection optical system 1000 can effectively control the light path, introduce more light while making the structure more compact, and achieve miniaturization. Through the combination of different lenses and the reasonable allocation of optical power, it has a large viewing angle, short focal length, and low distortion, resulting in better imaging effect.

[0049] In one embodiment of this utility model, the optical power of the first lens group 100 is φ100, the optical power of the second lens group 200 is φ200, and the optical power of the curved reflector is φ400. The optical power satisfies the following conditions: 0.04 ≤ |φ100| ≤ 0.06, 0.003 ≤ |φ200| ≤ 0.01, and 0.04 ≤ |φ400| ≤ 0.08. Based on this optical power distribution, a throw ratio below 0.25 can be achieved. It can be understood that the throw ratio is the ratio between the projector's projection distance and the width of the projected image. The smaller the throw ratio, the wider the projected image at the same projection distance. Conversely, the larger the ratio, the smaller the projected image. Since a smaller throw ratio means a shorter projection distance for projecting the same image size, lenses with smaller throw ratios are more likely to meet the spatial requirements of different scenarios.

[0050] To improve clarity at different projection distances, in one embodiment of this invention, the optical power of the first lens group 100 is φ100, and the optical power of the second lens group 200 is φ200. The ratio of the optical power of the first lens group 100 to the optical power of the second lens group 200 satisfies: 7≤|φ100 / φ200|≤11. Thus, when the projection distance is changed, the second lens group 200 moves back and forth to achieve zoom, which can improve clarity at different projection distances and reduce distortion.

[0051] In one embodiment of this utility model, the optical power of the first lens 1 is φ1, the optical power of the second lens 2 is φ2, the sum of the optical powers of the third lens 3, the fourth lens 4, and the fifth lens 5 is φ345; the sum of the optical powers of the sixth lens 6 and the seventh lens 7 is φ67; the optical power of the eighth lens 8 is φ8; the optical power of the ninth lens 9 is φ9; the sum of the optical powers of the tenth lens 10 and the eleventh lens 11 is φ1011; the optical power of the twelfth lens 12 is φ12; and the optical power of the thirteenth lens 13 is φ13. The optical power of each lens satisfies the following conditions: 0.01≤|φ1|≤0.03, 0.04≤|φ2|≤0.07, 0.002≤|φ345|≤0.05, 0.01≤|φ67|≤0.04, 0.02≤|φ8|≤0.05, 0.01≤|φ9|≤0.04, 0.01≤|φ1011|≤0.04, 0.01≤|φ12|≤0.04, 0.02≤|φ13|≤0.06. By limiting the optical power of each lens, the clarity of the fixed-focus projection optical system 1000 is improved.

[0052] In one embodiment of this utility model, the first lens group 100 includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7, an aperture e, and an eighth lens 8 arranged sequentially from the object side to the image side. The second lens group 200 includes a ninth lens 9, a tenth lens 10, an eleventh lens 11, a twelfth lens 12, and a thirteenth lens 13 arranged sequentially from the object side to the image side. The distance between the center of the thirteenth lens 13 and the center of the plane mirror 300 is T1, and the distance between the center of the plane mirror 300 and the center of the curved mirror is T2. The distance T13 between the center of the first lens 1 and the center of the thirteenth lens 13 satisfies: 0.5≤T13 / (T1+T2)≤0.9. In this way, while ensuring that the reflected light can be incident on the curved mirror, the light path emitted from the curved mirror does not interfere with the first lens group 100 and the second lens group 200, thereby increasing the projection effect.

[0053] In one embodiment of this utility model, the first lens group 100 includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7, an aperture e, and an eighth lens 8 arranged sequentially from the object side to the image side; the distance from the first lens 1 to the intersection of the plane mirror 300 and the optical axis along the optical axis is T00, and the distance from the micromirror array a to the first lens 1 is T11. The ratio of T00 and T11 satisfies: T00 / T11≤4.5; thus, the volume is further reduced.

[0054] In one embodiment of the present invention, the first lens group 100 includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7, an aperture e, and an eighth lens 8 arranged sequentially from the object side to the image side; the second lens group 200 includes a ninth lens 9, a tenth lens 10, an eleventh lens 11, a twelfth lens 12, and a thirteenth lens 13 arranged sequentially from the object side to the image side.

[0055] The second lens 2, the eighth lens 8 and the ninth lens 9 are glass aspherical lenses, while the twelfth lens 12, the thirteenth lens 13 and the curved reflector 400 are plastic aspherical lenses.

[0056] Understandably, aspherical lenses are characterized by a continuous change in curvature from the center to the periphery. Unlike spherical lenses, which have a constant curvature from the center to the periphery, aspherical lenses have better curvature radius characteristics. They have the advantage of improving distortion aberrations and astigmatism. By using aspherical lenses, aberrations that occur during imaging can be eliminated as much as possible, thereby improving the image quality of the lens.

[0057] The second lens 2 is a glass aspherical surface, which can correct coma and distortion caused by a large field of view. The eighth lens 8 is an aspherical surface, the ninth lens 9 is an aspherical surface, and the twelfth lens 12, the thirteenth lens 13 and the curved reflector 400 are plastic aspherical surfaces. The aspherical surfaces further reduce field curvature and distortion at different projection distances, thereby achieving a projection range of 40-150 feet.

[0058] Furthermore, this invention achieves non-defocusing output and high manufacturing yield by rationally combining plastic lenses with positive and negative optical power.

[0059] Specifically, in one embodiment of this utility model, the surface shape of the aspherical lens in the fixed-focus projection optical system 1000 should satisfy the following equation:

[0060]

[0061] Where c is the curvature corresponding to the radius; y is the radial coordinate (its unit is the same as the lens length unit); k is the conic quadratic coefficient, and A, B, C, D, E, F, G... represent the fourth, sixth, eighth, tenth, twelfth, fourteenth, sixteenth... aspherical coefficients, respectively.

[0062] More specifically, in one embodiment of this utility model, the coefficients of even-order terms for each aspherical surface are shown in Table 1 below.

[0063] Table 1

[0064]

[0065]

[0066] Furthermore, in one embodiment of this utility model, the third lens 3, the fourth lens 4, and the fifth lens 5 are cemented together; the sixth lens 6 and the seventh lens 7 are cemented together; and the tenth lens 10 and the eleventh lens 11 are cemented together. By cementing the third lens 3, the fourth lens 4, and the fifth lens 5, chromatic aberration in a large field of view is corrected. The sixth lens 6 and the seventh lens 7 are cemented doublet lenses, which further correct the magnification chromatic aberration of the correction system, so that the system obtains a smaller chromatic aberration while increasing the light height of the off-axis field of view, giving the system a larger target surface.

[0067] Furthermore, in one embodiment of this invention, 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 tenth lens 10, and the eleventh lens 11 are glass spherical lenses. To improve the image quality of the lens at various magnifications, this invention combines high-refractive-index glass with ultra-low dispersion glass materials. This reduces various optical aberrations while effectively suppressing chromatic aberration. Simultaneously, because glass lenses are less susceptible to focus shift due to thermal expansion and contraction, they effectively resist lens thermal deformation, maintaining high lens precision over extended periods. Furthermore, this approach minimizes aberrations that occur during imaging, thereby improving image quality and reducing the impact of temperature on lens optical performance.

[0068] Specifically, in one embodiment of this utility model, when the projection ratio is 0.25, the micromirror array a is 0.47 inches, the chip pixel size is 5.4 micrometers, and T00 / T11≤4.5, the parameters of the zoom lens are shown in Table 2 below.

[0069] Table 2

[0070]

[0071]

[0072]

[0073] Furthermore, the movement distance of the second lens group is as follows for images with different projection sizes:

[0074]

[0075] Figure 3 The figure shown is the MTF performance diagram when the projection size is 68 feet in this embodiment. Figure 4The diagram shown illustrates the distortion when the projection size is 68 feet in this embodiment. Figure 5 The diagram shown is a schematic of the MTF (Mean Transmission Flow) when the projection size is 150 feet in this embodiment. Figure 6 The diagram shown is an MTF diagram when the projection size is 40 feet in this embodiment. Figure 2-6 It can be seen that the fixed-focus optical system provided in this embodiment has good imaging capability within a projection range of 40-150 feet.

[0076] Furthermore, in order to better change the direction of the light path, in one embodiment of this utility model, the angle between the optical axis of the plane mirror 300 and the refraction mirror group is 45°, which changes the direction of the light path and greatly shortens the length of the system along the projection direction, thereby further improving the miniaturization of the fixed-focus projection optical system 1000.

[0077] The above description is merely an exemplary embodiment of the present utility model and does not limit the patent scope of the present utility model. Any equivalent structural transformations made based on the technical concept of the present utility model and the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present utility model.

Claims

1. A fixed-focus projection optical system, characterized in that, The fixed-focus projection optical system has an object side and an image side arranged opposite to each other along the optical axis. The fixed-focus projection optical system includes a micromirror array, an equivalent prism, a galvanometer, a first lens group, a second lens group, a plane mirror, and a curved mirror arranged sequentially from the object side to the image side. The planar reflector and the curved reflector are respectively disposed on both sides of the optical axis. The planar reflector is set at an angle to the optical axis, and one end of it intersects the optical axis. The first lens group has a positive optical power, the second lens group has a negative optical power, and the second lens group can move along the optical axis to enable the fixed-focus projection optical system to focus when the projection distance changes.

2. The fixed-focus projection optical system as described in claim 1, characterized in that, The first lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an aperture stop, and an eighth lens arranged sequentially from the object side to the image side. The first lens has positive optical power, the second lens has positive optical power, the third lens has positive optical power, the fourth lens has negative optical power, the fifth lens has positive optical power, the sixth lens has negative optical power, the seventh lens has positive optical power, and the eighth lens has positive optical power; and / or, The second lens group includes a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a thirteenth lens arranged sequentially from the object side to the image side, wherein the optical power of the ninth lens is positive, the optical power of the tenth lens is positive, the optical power of the eleventh lens is negative, the optical power of the twelfth lens is negative, and the optical power of the thirteenth lens is negative.

3. The fixed-focus projection optical system as described in claim 1, characterized in that, The optical power of the first lens group is φ 100 The optical power of the second lens group is φ 200 The optical power of the curved reflector is φ 400 The optical power satisfies: 0.04≤|φ 100 |≤0.06,0.003≤|φ 200 |≤0.01,0.04≤|φ 400 |≤0.08。 4. The fixed-focus projection optical system as described in claim 1, characterized in that, The optical power of the first lens group is φ 100 The optical power of the second lens group is φ 200 The ratio of the optical power of the first lens group to the optical power of the second lens group satisfies: 7≤|φ 100 / f 200 |≤11。 5. The fixed-focus projection optical system as described in claim 1, characterized in that, The first lens has an optical power of φ1, the second lens has an optical power of φ2, and the sum of the optical powers of the third, fourth, and fifth lenses is φ. 345 The sum of the optical power of the sixth lens and the seventh lens is φ. 67 The eighth lens has an optical power of φ8; the ninth lens has an optical power of φ9; the sum of the optical powers of the tenth and eleventh lenses is φ. 1011 The optical power of the twelfth lens is φ. 12 The optical power of the thirteenth lens is φ. 13 The optical power of each lens satisfies: 0.01≤|φ1|≤0.03,0.04≤|φ2|≤0.07,0.002≤|φ 345 |≤0.05,0.01≤|φ 67 |≤0.04,0.02≤|φ8|≤0.05,0.01≤|φ9|≤0.04,0.01≤|φ 1011 |≤0.04,0.01≤|φ 12 |≤0.04,0.02≤|φ 13 |≤0.06。 6. The fixed-focus projection optical system as described in claim 1, characterized in that, The first lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an aperture stop, and an eighth lens arranged sequentially from the object side to the image side; the second lens group includes a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a thirteenth lens arranged sequentially from the object side to the image side. The distance between the center of the thirteenth lens and the center of the plane mirror is T1, and the distance between the center of the plane mirror and the center of the curved mirror is T2. The distance T13 between the center of the first lens and the center of the thirteenth lens (13) satisfies: 0.5≤T13 / (T1+T2)≤0.

9.

7. The fixed-focus projection optical system as described in claim 1, characterized in that, The first lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an aperture stop, and an eighth lens arranged sequentially from the object side to the image side; The distance from the first lens to the intersection of the plane mirror and the optical axis along the optical axis is T00, and the distance from the micromirror array to the first lens is T11. The ratio of T00 to T11 satisfies: T00 / T11≤4.

5.

8. The fixed-focus projection optical system as described in claim 1, characterized in that, The first lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an aperture stop, and an eighth lens arranged sequentially from the object side to the image side; the second lens group includes a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a thirteenth lens arranged sequentially from the object side to the image side. The second lens, the eighth lens, and the ninth lens are glass aspherical lenses, while the twelfth lens, the thirteenth lens, and the curved reflector are plastic aspherical lenses.

9. The fixed-focus projection optical system as described in claim 1, characterized in that, The first lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an aperture stop, and an eighth lens arranged sequentially from the object side to the image side; the second lens group includes a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, and a thirteenth lens arranged sequentially from the object side to the image side. The third lens, the fourth lens, and the fifth lens are cemented together; the sixth lens is cemented together with the seventh lens; and the tenth lens is cemented together with the eleventh lens.

10. The fixed-focus projection optical system as described in claim 1, characterized in that, The optical axis angle between the plane mirror and the refracting mirror group is 45°.

Images