A catadioptric hybrid thermally stable ultra-short throw projection lens

Abstract

The application discloses a catadioptric thermal stable ultra-short focus projection lens, and relates to the technical field of projection lenses, which comprises a coated mirror, a front group of refractive lenses, an aperture, a rear group of refractive lenses and an equivalent back focus group arranged in sequence from an object side to an image side, and the coated mirror, the front group of refractive lenses, the aperture, the rear group of refractive lenses and the equivalent back focus group jointly form a lens, wherein the front group of refractive lenses comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens and a ninth lens arranged in sequence, and the application introduces a reflecting mirror to fold an optical path, effectively controls the total optical length while realizing a 0.45 ultra-short projection ratio, is compact in structure, adopts a glass-plastic hybrid scheme, uses a glass material lens at a key aberration correction position, and uses a plastic material aspherical surface lens at a non-key surface to control the cost and weight.

Description

Technical Field

[0001] This invention relates to the field of projection lens technology, and specifically to a catadioptric hybrid thermally stable ultra-short-throw projection lens. Background Technology

[0002] The projection lens is the core optical component of a projector. Based on the projection distance, it is divided into short-throw, medium-throw, long-throw, and special types such as reflective and fisheye lenses. Ultra-short-throw projection lenses are one type. Ultra-short-throw projection technology can project large-size images within a limited distance.

[0003] The optical system design for ultra-short-throw projection technology faces multiple challenges, including aberration correction, structural length, and thermal stability. In particular, traditional fully refractive designs, designed to correct aberrations in extremely large fields of view, often result in a large number of lenses, a lengthy system, and sensitivity to operating temperature, making them prone to thermal image quality degradation and focus drift. Especially in compact optical engines using small-sized, high-power DMD chips, the axial temperature gradient of the lens assembly caused by the heat generated by the chip and light source further exacerbates performance fluctuations. Summary of the Invention

[0004] The purpose of this invention is to provide a thermo-stable ultra-short-throw projection lens with a folding-reflection hybrid design, which solves the technical problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution:

[0006] A catadioptric hybrid thermally stable ultra-short-throw projection lens includes a coated mirror, a front refractive lens, an aperture, a rear refractive lens, and an equivalent back focal group arranged sequentially from the object side to the image side. The coated mirror, the front refractive lens, the aperture, the rear refractive lens, and the equivalent back focal group together form a lens. The front refractive lens includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens arranged sequentially. The rear refractive lens includes a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, a fourteenth lens, a fifteenth lens, and a sixteenth lens arranged sequentially. The equivalent back focal group includes a plane glass, an equivalent prism, a protective glass surface, and an image plane arranged sequentially.

[0007] The effective focal length EFFL of the projection lens is 3mm≤EFFL≤4mm. The coated reflector is an aspherical lens with positive optical power and its concave surface faces the image side. The tenth, eleventh, and twelfth lenses form a cemented triplet lens with positive optical power, and the thirteenth and fourteenth lenses form a cemented doublet lens with negative optical power. The aperture stop is located between the cemented triplet lens and the ninth lens.

[0008] The first lens is an aspherical lens with negative optical power; the second lens is a spherical lens with negative optical power; the third lens is an aspherical lens with negative optical power; the fourth lens is a spherical lens with positive optical power; the fifth lens is an aspherical lens with positive optical power; the sixth lens is a spherical lens with positive optical power; the seventh lens is a spherical lens with negative optical power; the eighth lens is a spherical lens with negative optical power; the ninth lens is a spherical lens with positive optical power; the tenth lens is a spherical lens with positive optical power; the eleventh lens is a spherical lens with negative optical power; the twelfth lens is a spherical lens with positive optical power; the thirteenth lens is a spherical lens with negative optical power; the fourteenth lens is a spherical lens with positive optical power; the fifteenth lens is an aspherical lens with positive optical power; and the sixteenth lens is a spherical lens with positive optical power.

[0009] As a preferred embodiment of the present invention, the projection lens composed of the coated reflector, the front refractive lens, the aperture, the rear refractive lens and the equivalent back focal group has a projection ratio of 0.45 and an F number of 2.4, and the aperture D of the coated reflector is ≤84mm.

[0010] In a preferred embodiment of the present invention, the center thickness T1 of the first lens and the total optical length TTL of the projection lens satisfy the following: 0.006≤T1 / TTL≤0.008; the center thickness T1 of the third lens and the total optical length TTL of the projection lens satisfy the following: 0.006≤T1 / TTL≤0.007; the center thickness T1 of the fifth lens and the total optical length TTL of the projection lens satisfy the following: 0.010≤T1 / TTL≤0.014; and the center thickness T1 of the fifteenth lens and the total optical length TTL of the projection lens satisfy the following: 0.022≤T1 / TTL≤0.026.

[0011] In a preferred embodiment of the present invention, the second, seventh, eighth, eleventh, and thirteenth lenses have concave surfaces facing the object side and concave surfaces facing the image side; the fourth, sixth, ninth, tenth, twelfth, and fourteenth lenses have convex surfaces facing the object side and convex surfaces facing the image side; and the sixteenth lens has a concave surface facing the object side and a convex surface facing the image side.

[0012] In a preferred embodiment of the present invention, the coated reflector is a plastic aspherical reflector, the first lens and the third lens are both plastic aspherical lenses, and the fifth lens and the fifteenth lens are both glass aspherical lenses.

[0013] As a preferred embodiment of the present invention, the projection lens satisfies the condition: 0.12≤BFL / TTL≤0.16;

[0014] Wherein, TTL is the total optical length of the projection lens; BFL is the optical back focal length of the projection lens.

[0015] In a preferred embodiment of the present invention, in the cemented triplet lens, the refractive indices of the tenth and twelfth lenses are both lower than that of the eleventh lens, and the cemented triplet lens satisfies the following condition:

[0016] 2mm≤T10≤4mm;

[0017] 0.5mm≤T11≤1.5mm;

[0018] 3mm≤T12≤4mm;

[0019] |R12|+|R13|≥25.5;

[0020] Wherein, T10 is the center thickness of the tenth lens, T11 is the center thickness of the eleventh lens, T12 is the center thickness of the twelfth lens, R12 is the curvature of the object side surface in the eleventh lens, and R13 is the curvature of the image side surface in the eleventh lens.

[0021] The refractive index of the fourteenth lens is less than that of the thirteenth lens, and the cemented doublet lens satisfies the following condition:

[0022] 0.5mm≤T13≤1.5mm;

[0023] 3.5mm≤T14≤5.0mm;

[0024] Where T13 is the center thickness of the thirteenth lens and T14 is the center thickness of the fourteenth lens;

[0025] The center thickness T16 of the sixteenth lens is ≥3.5mm;

[0026] In the projection lens, the maximum center thickness of all lenses is T, and T≤4.5mm.

[0027] As a preferred embodiment of the present invention, the air gap between the aperture stop and the ninth lens is L1, and the air gap between the aperture stop and the cemented triplet lens is L2, wherein 0.04mm≤L1 and 2.8mm≤L2.

[0028] As a preferred embodiment of the present invention, the effective focal length of the coated mirror is F1, 15mm≤F1≤25mm;

[0029] The effective focal length of the first lens is F2, -130mm≤F2≤-100mm;

[0030] The effective focal length of the second lens is F3, -70mm≤F3≤-40mm;

[0031] The effective focal length of the third lens is F4, -60mm≤F4≤-40mm;

[0032] The effective focal length of the fourth lens is F5, 25mm≤F5≤45mm;

[0033] The effective focal length of the fifth lens is F6, 140mm≤F6≤150mm;

[0034] The effective focal length of the sixth lens is F7, 20mm≤F7≤30mm

[0035] The effective focal length of the seventh lens is F8, -35mm≤F8≤-15mm

[0036] The effective focal length of the eighth lens is F9, -35mm≤F9≤-15mm

[0037] The effective focal length of the ninth lens is F10, 8mm≤F10≤18mm

[0038] The effective focal length of the tenth lens is F11, 62mm≤F11≤82mm

[0039] The effective focal length of the eleventh lens is F12, -16mm≤F12≤-6mm

[0040] The effective focal length of the twelfth lens is F13, 45mm≤F13≤65mm.

[0041] The effective focal length of the thirteenth lens is F14, -15mm≤F14≤-5mm

[0042] The effective focal length of the fourteenth lens is F15, 52mm≤F15≤72mm

[0043] The effective focal length of the fifteenth lens is F16, 20mm≤F16≤40mm

[0044] The effective focal length of the sixteenth lens is F17, 20mm≤F17≤40mm.

[0045] As a preferred embodiment of the present invention, the media constituting the back focal length of the projection lens, measured from the image side, are air, Eagle XG glass, air, H-K9L prism, air, D263 protective glass, and air, respectively, with axial thicknesses of 0.307mm, 0.7mm, 1.0mm, 12.0mm, 7.76mm, 1.1mm, and 1.338mm.

[0046] Compared with the prior art, the present invention has the following advantages:

[0047] This invention achieves an ultra-short projection ratio of 0.45 by introducing a mirror to fold the optical path, while effectively controlling the total optical length and resulting in a compact structure. It adopts a glass-plastic hybrid scheme, using glass lenses at key aberration correction positions and plastic aspherical lenses at non-critical surfaces to control cost and weight. Attached Figure Description

[0048] To more clearly illustrate the embodiments of the present invention or the technical solutions in 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 merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0049] Figure 1 This invention provides a layout schematic diagram of a folding-reflection hybrid thermally stable ultra-short-throw projection lens;

[0050] Figure 2 This invention provides a global optical path diagram of a catadioptric hybrid thermally stabilized ultra-short-throw projection lens;

[0051] Figure 3 This invention provides a comparison chart of MTF values ​​at an ambient temperature of 25 degrees Celsius.

[0052] Figure 4 This invention provides a comparison chart of MTF values ​​at an ambient temperature of 0 degrees Celsius.

[0053] Figure 5 This invention provides a comparison chart of MTF values ​​at an ambient temperature of 50 degrees Celsius.

[0054] Figure 6 This invention provides a system field curvature and distortion diagram at 0 degrees Celsius;

[0055] Figure 7 This invention provides a system field curvature and distortion diagram at 25 degrees Celsius;

[0056] Figure 8 This invention provides a system field curvature and distortion diagram at 50 degrees Celsius;

[0057] Figure 9 This invention provides a vertical color difference distribution diagram at 0 degrees Celsius;

[0058] Figure 10 This invention provides a vertical color difference distribution diagram at 25 degrees Celsius;

[0059] Figure 11 This invention provides a vertical color difference distribution diagram at 50 degrees Celsius;

[0060] Figure 12 This invention provides a dot plot at 0 degrees Celsius;

[0061] Figure 13 This invention provides a dot plot at 25 degrees Celsius;

[0062] Figure 14 This invention provides a dot plot at 50 degrees Celsius;

[0063] Figure 15 This invention provides a relative illuminance curve at 0 degrees Celsius;

[0064] Figure 16 This invention provides a relative illuminance curve at 25 degrees Celsius;

[0065] Figure 17 The present invention provides a relative illuminance curve at 50 degrees Celsius.

[0066] Figure 18 This invention provides a partial layout schematic diagram of a folding-reflection hybrid thermally stabilized ultra-short-throw projection lens.

[0067] The labels in the diagram represent the following:

[0068] 1. Coated mirror; 2. First lens; 3. Second lens; 4. Third lens; 5. Fourth lens; 6. Fifth lens; 7. Sixth lens; 8. Seventh lens; 9. Eighth lens; 10. Ninth lens; 11. Tenth lens; 12. Eleventh lens; 13. Twelfth lens; 14. Thirteenth lens; 15. Fourteenth lens; 16. Fifteenth lens; 17. Sixteenth lens; 18. Plane glass; 19. Equivalent prism; 20. Protective glass surface; 21. Image plane; 22. Aperture. Detailed Implementation

[0069] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0070] like Figures 1 to 18As shown, the present invention provides a catadioptric hybrid thermally stable ultra-short-throw projection lens, comprising a coated reflector 1, a front refractive lens, an aperture 22, a rear refractive lens, and an equivalent back focal group arranged sequentially from the object side to the image side. The coated reflector 1, the front refractive lens, the aperture 22, the rear refractive lens, and the equivalent back focal group together form a lens. The front refractive lens includes a first lens 2, a second lens 3, a third lens 4, a fourth lens 5, a fifth lens 6, a sixth lens 7, a seventh lens 8, an eighth lens 9, and a ninth lens 10 arranged sequentially. The rear refractive lens includes a tenth lens 11, an eleventh lens 12, a twelfth lens 13, a thirteenth lens 14, a fourteenth lens 15, a fifteenth lens 16, and a sixteenth lens 17 arranged sequentially. The equivalent back focal group includes a plane glass 18, an equivalent prism 19, a protective glass surface 20, and an image plane 21 arranged sequentially.

[0071] The effective focal length EFFL of the projection lens is 3mm≤EFFL≤4mm. The coated reflector 1 is an aspherical lens with positive optical power and its concave surface faces the image side. The tenth lens 11, the eleventh lens 12 and the twelfth lens 13 form a cemented triplet lens with positive optical power. The thirteenth lens 14 and the fourteenth lens 15 form a cemented doublet lens with negative optical power. The aperture stop 22 is located between the cemented triplet lens and the ninth lens 10.

[0072] Among them, the first lens 2 is an aspherical lens with negative optical power, the second lens 3 is a spherical lens with negative optical power, the third lens 4 is an aspherical lens with negative optical power, the fourth lens 5 is a spherical lens with positive optical power, the fifth lens 6 is an aspherical lens with positive optical power, the sixth lens 7 is a spherical lens with positive optical power, the seventh lens 8 is a spherical lens with negative optical power, the eighth lens 9 is a spherical lens with negative optical power, the ninth lens 10 is a spherical lens with positive optical power, the tenth lens 11 is a spherical lens with positive optical power, the eleventh lens 12 is a spherical lens with negative optical power, the twelfth lens 13 is a spherical lens with positive optical power, the thirteenth lens 14 is a spherical lens with negative optical power, the fourteenth lens 15 is a spherical lens with positive optical power, the fifteenth lens 16 is an aspherical lens with positive optical power, and the sixteenth lens 17 is a spherical lens with positive optical power.

[0073] The projection lens consisting of the coated reflector 1, the front refractive lens, the aperture, the rear refractive lens, and the equivalent back focal group has a projection ratio of 0.45 and an F-number of 2.4. The aperture D of the coated reflector 1 is ≤84mm.

[0074] The center thickness T1 of the first lens 2 and the total optical length TTL of the projection lens satisfy the following condition: 0.006 ≤ T1 / TTL ≤ 0.008; the center thickness T1 of the third lens 4 and the total optical length TTL of the projection lens satisfy the following condition: 0.006 ≤ T1 / TTL ≤ 0.007; the center thickness T1 of the fifth lens 6 and the total optical length TTL of the projection lens satisfy the following condition: 0.010 ≤ T1 / TTL ≤ 0.014; and the center thickness T1 of the fifteenth lens 16 and the total optical length TTL of the projection lens satisfy the following condition: 0.022 ≤ T1 / TTL ≤ 0.026.

[0075] The second lens 3, the seventh lens 8, the eighth lens 9, the eleventh lens 12 and the thirteenth lens 14 all have concave surfaces facing the object side and concave surfaces facing the image side. The fourth lens 5, the sixth lens 7, the ninth lens 10, the tenth lens 11, the twelfth lens 13 and the fourteenth lens 15 have convex surfaces facing the object side and convex surfaces facing the image side. The sixteenth lens 17 has a concave surface facing the object side and a convex surface facing the image side.

[0076] The coated reflector 1 is a plastic aspherical reflector, the first lens 2 and the third lens 4 are both plastic aspherical lenses, and the fifth lens 6 and the fifteenth lens 16 are both glass aspherical lenses.

[0077] The projection lens satisfies the condition: 0.12≤BFL / TTL≤0.16;

[0078] Wherein, TTL is the total optical length of the projection lens; BFL is the optical back focal length of the projection lens.

[0079] In the cemented triplet lens, the refractive indices of the tenth lens 11 and the twelfth lens 13 are both lower than the refractive index of the eleventh lens 12, and the cemented triplet lens satisfies the following condition:

[0080] 2mm≤T10≤4mm;

[0081] 0.5mm≤T11≤1.5mm;

[0082] 3mm≤T12≤4mm;

[0083] |R12|+|R13|≥25.5;

[0084] Wherein, T10 is the center thickness of the tenth lens 11, T11 is the center thickness of the eleventh lens 12, T12 is the center thickness of the twelfth lens 13, R12 is the curvature of the object side surface in the eleventh lens 12, and R13 is the curvature of the image side surface in the eleventh lens 12.

[0085] The refractive index of the fourteenth lens 15 is less than that of the thirteenth lens 14, and the cemented doublet lens satisfies the following condition:

[0086] 0.5mm≤T13≤1.5mm;

[0087] 3.5mm≤T14≤5.0mm;

[0088] Wherein, T13 is the center thickness of the thirteenth lens 14, and T14 is the center thickness of the fourteenth lens 15;

[0089] The center thickness T16 of the sixteenth lens 17 is ≥3.5mm;

[0090] In the projection lens, the maximum center thickness of all lenses is T, and T≤4.5mm.

[0091] The air gap between the aperture stop 22 and the ninth lens 10 is L1, and the air gap between the aperture stop 22 and the cemented triplet lens is L2, wherein 0.04mm≤L1 and 2.8mm≤L2.

[0092] The effective focal length of the coated reflector 1 is F1, 15mm≤F1≤25mm;

[0093] The effective focal length of the first lens 2 is F2, -130mm≤F2≤-100mm;

[0094] The effective focal length of the second lens 3 is F3, -70mm≤F3≤-40mm;

[0095] The effective focal length of the third lens 4 is F4, -60mm≤F4≤-40mm;

[0096] The effective focal length of the fourth lens 5 is F5, 25mm≤F5≤45mm;

[0097] The effective focal length of the fifth lens 6 is F6, 140mm≤F6≤150mm;

[0098] The effective focal length of the sixth lens 7 is F7, 20mm≤F7≤30mm

[0099] The effective focal length of the seventh lens 8 is F8, -35mm≤F8≤-15mm

[0100] The effective focal length of the eighth lens 9 is F9, -35mm≤F9≤-15mm

[0101] The effective focal length of the ninth lens 10 is F10, 8mm≤F10≤18mm

[0102] The effective focal length of the tenth lens 11 is F11, 62mm≤F11≤82mm

[0103] The effective focal length of the eleventh lens 12 is F12, -16mm≤F12≤-6mm

[0104] The effective focal length of the twelfth lens 13 is F13, 45mm≤F13≤65mm.

[0105] The effective focal length of the thirteenth lens 14 is F14, -15mm≤F14≤-5mm

[0106] The effective focal length of the fourteenth lens 15 is F15, 52mm≤F15≤72mm

[0107] The effective focal length of the fifteenth lens 16 is F16, 20mm≤F16≤40mm

[0108] The effective focal length of the sixteenth lens 17 is F17, 20mm≤F17≤40mm.

[0109] Starting from the image side, the media constituting the back focal length of the projection lens are, in order, air, Eagle XG glass, air, H-K9L prism, air, D263 protective glass, and air, with axial thicknesses of 0.307mm, 0.7mm, 1.0mm, 12.0mm, 7.76mm, 1.1mm, and 1.338mm, respectively.

[0110] The projection lens of this application has a folding hybrid structure. Along the actual optical path, from the image side to the object side of the projection lens, a coated reflector 1, a front refractive lens, an aperture stop 22, a rear refractive lens, and an equivalent back focal group are arranged in sequence. The coated reflector 1 is used to deflect the optical path to fold the optical path, thereby effectively shortening the total physical length of the entire lens and achieving an ultra-short projection ratio of 0.45. In this embodiment, the total length TTL of the projection lens is no more than 165mm.

[0111] In this embodiment, the lens can be modularly assembled, and the front group (coated mirror 1 and front refractive lens group) and the rear group (rear refractive lens group) can be adjusted and assembled separately.

[0112] In this embodiment, the F-number reflects the ability of the projection lens to collect light. Here, it refers to the working F-number ≈ 1 / (2 × sinθ), where θ is the angle between the edge ray on the image side and the optical axis.

[0113] The lens barrel structure design of the projection lens needs to take into account the thermal expansion coefficient of each lens material, and reserve fine-tuning links at key locations to adapt to mass production tolerances. The optical processing and coating need to meet the surface accuracy and spectral characteristics required by the design.

[0114] Figures 3 to 5 These represent the MTF (Mean Transformation Factor) of the projection lens at ambient temperatures of 25°C, 0°C, and 50°C, respectively. Figures 3 to 5 It can be seen that the MTF of the entire field of view remains at 112lp > 0.64 under different ambient temperatures; this indicates that the projection lens module maintains excellent contrast transmission capability and resolution at high spatial frequencies throughout the entire effective image plane 21 area, effectively avoiding image blurring caused by insufficient lens resolution.

[0115] Depend on Figures 3-5 As can be seen, under the above three sets of ambient temperatures, the MTF of the projection lens of this application changes very little, which demonstrates that the projection lens module has excellent thermal stability performance that is not affected by ambient temperature, thus ensuring the excellent quality of the projected image.

[0116] Figure 6 The figure shows the system field curvature and distortion at 0 degrees Celsius. As can be seen from the figure, the maximum distortion of the projection lens module across the entire field of view is 0.2735% at an ambient temperature of 0 degrees Celsius. This value ensures that the projected image will not be distorted, providing a good display foundation for engineering design and professional presentations. At the same time, it greatly reduces the need for software distortion correction functions, ensures the integrity and resolution of the image, significantly simplifies the calibration process for multi-projection image splicing and blending, and improves the visual comfort and professional reliability of the overall solution.

[0117] Figure 7 The figure shows the system field curvature and distortion at 25 degrees Celsius. As can be seen from the figure, the maximum distortion of the projection lens module across the entire field of view is 0.2740% at an ambient temperature of 25 degrees Celsius. This value ensures that the projected image will not be distorted, providing a good display foundation for engineering design and professional presentations. At the same time, it greatly reduces the need for software distortion correction functions, ensures the integrity and resolution of the image, significantly simplifies the calibration process for multi-projection image splicing and blending, and improves the visual comfort and professional reliability of the overall solution.

[0118] Figure 8 The figure shows the system field curvature and distortion at 50 degrees Celsius. As can be seen from the figure, at an ambient temperature of 50 degrees Celsius, the maximum distortion of the projection lens module across the entire field of view is 0.2744%. This value ensures that the projected image will not be distorted, providing a good display foundation for engineering design and professional presentations. At the same time, it greatly reduces the need for software distortion correction functions, ensures the integrity and resolution of the image, significantly simplifies the calibration process for multi-projection image splicing and blending, and improves the visual comfort and professional reliability of the overall solution.

[0119] Figures 6-8It is clearly shown that the maximum distortion value of the projection lens of this application fluctuates very little under the above three sets of ambient temperatures, which reflects the excellent thermal stability of the projection lens and ensures the excellent quality of the image.

[0120] Figures 9-11 The images show the chromatic aberration distribution of the projection lens in this application at 0 degrees Celsius, 25 degrees Celsius, and 50 degrees Celsius, respectively. Figures 9-11 It is known that the vertical chromatic difference of the projection lens in this application is less than 1um, or 0.23 pixels, in the entire field of view at ambient temperatures of 0 degrees Celsius, 25 degrees Celsius, and 50 degrees Celsius. This means that the vertical chromatic difference of the projection lens hardly changes at these three ambient temperatures, making the image projected by the projection lens more natural and ensuring that the image will not be affected by the red-green-blue difference caused by temperature changes, thus guaranteeing the excellent quality of the image.

[0121] Figures 12-14 The images show dot plots of the projection lens of this application at ambient temperatures of 0 degrees Celsius, 25 degrees Celsius, and 50 degrees Celsius, respectively. Figures 12-14 As can be seen, the maximum RMS radius of the projection lens in this application is less than 2.25um, which is 0.5 pixels in size. This greatly ensures the image reproduction capability of the projection lens optical system and guarantees the clarity of the projected image. Through the above three sets of data, it can be seen that the projection lens of this application is minimally affected by ambient temperature, which reflects the excellent thermal stability of the projection lens optical system and ensures the excellent quality of the image.

[0122] Figures 15-17 The figures show the relative illumination curves of the projection lens of this application at ambient temperatures of 0 degrees Celsius, 25 degrees Celsius, and 50 degrees Celsius, respectively. Figures 15-17 As can be seen, the relative illumination of the projection lens in this application is greater than 70% across the entire screen. This indicator ensures that the projection lens can effectively utilize the light flux provided by the projection optical engine and guarantee the brightness of the projected image.

[0123] The above three sets of data are minimally affected by changes in ambient temperature, demonstrating the excellent thermal stability of the projection lens.

[0124] Experimental example:

[0125] Thermal stability verification method: Based on the Zemax multi-structure, axial stepped temperature field simulation optimization was carried out to simulate the relevant optical indicators of different lens groups at ambient temperatures of 0°C, 25°C, and 50°C, and at temperatures of 40°C, 50°C, 60°C, and 70°C from the object plane to the image plane.

[0126] 1. Under ambient temperature of 0 degrees Celsius

[0127] The temperature of the coated reflector 1 was set to 40 degrees, the temperature of the front refractive lens was set to 50 degrees, the temperature of the rear refractive lens was set to 60 degrees, and the temperature of the equivalent rear focal group was set to 70 degrees. Zemax was used for simulation optimization to ensure that the final optimized indexes met the specifications and that the numerical changes were less affected by temperature.

[0128] 2. Under an ambient temperature of 25 degrees Celsius

[0129] The temperature of the coated mirror 1 was set to 40 degrees, the temperature of the front refractive lens was set to 50 degrees, the temperature of the rear refractive lens was set to 60 degrees, and the temperature of the equivalent rear focal group was set to 70 degrees. Zemax was used for simulation optimization to ensure that the final optimized indexes met the specifications and that the numerical changes were less affected by temperature.

[0130] 3. Under an ambient temperature of 50 degrees Celsius

[0131] The temperature of the coated reflector 11 was set to 40 degrees, the temperature of the front refractive lens was set to 50 degrees, the temperature of the rear refractive lens was set to 60 degrees, and the temperature of the equivalent rear focal group was set to 70 degrees. Zemax was used for simulation optimization to ensure that the final optimized indexes met the specifications and that the numerical changes were less affected by temperature.

[0132] Verification results: such as Figures 3 to 17 As shown in the Zemax screenshot, the optical parameters indicate that all core optical image quality parameters (MTF, distortion, chromatic aberration, dot plot, and relative illumination) meet the requirements within the entire temperature range of 0°C to 50°C and 40°C to 70°C for the components.

[0133] Improvement results:

[0134] While achieving the effect of ultra-short throw projection, this projection lens adopts a catadioptric design and uses fewer lenses. The shorter overall system length meets many high image quality requirements while reducing the problems of image quality degradation and focus drift caused by the axial temperature gradient of the system due to drastic changes in ambient temperature and the heat generated by the projection optical engine light source.

[0135] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A thermostatically stabilized ultra-short-throw projection lens with a catadioptric design, characterized in that, The lens comprises a coated mirror (1), a front refractive lens, an aperture stop (22), a rear refractive lens, and an equivalent back focal group arranged sequentially from the object side to the image side. The coated mirror (1), the front refractive lens, the aperture stop (22), the rear refractive lens, and the equivalent back focal group together form a lens. The front refractive lens comprises a first lens (2), a second lens (3), a third lens (4), a fourth lens (5), a fifth lens (6), a sixth lens (7), a seventh lens (8), an eighth lens (9), and a ninth lens (10) arranged sequentially. The rear refractive lens comprises a tenth lens (11), an eleventh lens (12), a twelfth lens (13), a thirteenth lens (14), a fourteenth lens (15), a fifteenth lens (16), and a sixteenth lens (17) arranged sequentially. The equivalent back focal group comprises a plane glass (18), an equivalent prism (19), a protective glass surface (20), and an image plane (21) arranged sequentially. The effective focal length EFFL of the projection lens is 3mm≤EFFL≤4mm. The coated reflector (1) is an aspherical lens with positive optical power and the concave surface faces the image side. The tenth lens (11), the eleventh lens (12) and the twelfth lens (13) form a cemented triplet lens with positive optical power. The thirteenth lens (14) and the fourteenth lens (15) form a cemented doublet lens with negative optical power. The aperture stop (22) is located between the cemented triplet lens and the ninth lens (10). Among them, the first lens (2) is an aspherical lens with negative optical power, the second lens (3) is a spherical lens with negative optical power, the third lens (4) is an aspherical lens with negative optical power, the fourth lens (5) is a spherical lens with positive optical power, the fifth lens (6) is an aspherical lens with positive optical power, the sixth lens (7) is a spherical lens with positive optical power, the seventh lens (8) is a spherical lens with negative optical power, the eighth lens (9) is a spherical lens with negative optical power, and the ninth lens (1) is a spherical lens with negative optical power. 0) is a spherical lens with positive optical power, the tenth lens (11) is a spherical lens with positive optical power, the eleventh lens (12) is a spherical lens with negative optical power, the twelfth lens (13) is a spherical lens with positive optical power, the thirteenth lens (14) is a spherical lens with negative optical power, the fourteenth lens (15) is a spherical lens with positive optical power, the fifteenth lens (16) is an aspherical lens with positive optical power, and the sixteenth lens (17) is a spherical lens with positive optical power.

2. The catadioptric hybrid thermally stable ultra-short-throw projection lens according to claim 1, characterized in that, The projection lens consisting of the coated reflector (1), the front refractive lens, the aperture, the rear refractive lens and the equivalent back focal group has a projection ratio of 0.45 and an F number of 2.

4. The aperture D of the coated reflector (1) is ≤84mm.

3. The catadioptric hybrid thermally stable ultra-short-throw projection lens according to claim 1, characterized in that, The center thickness T1 of the first lens (2) and the total optical length TTL of the projection lens satisfy the following: 0.006≤T1 / TTL≤0.008; the center thickness T1 of the third lens (4) and the total optical length TTL of the projection lens satisfy the following: 0.006≤T1 / TTL≤0.007; the center thickness T1 of the fifth lens (6) and the total optical length TTL of the projection lens satisfy the following: 0.010≤T1 / TTL≤0.014; and the center thickness T1 of the fifteenth lens (16) and the total optical length TTL of the projection lens satisfy the following: 0.022≤T1 / TTL≤0.

026.

4. The catadioptric hybrid thermally stable ultra-short-throw projection lens according to claim 1, characterized in that, The second lens (3), the seventh lens (8), the eighth lens (9), the eleventh lens (12) and the thirteenth lens (14) all have concave surfaces facing the object side and concave surfaces facing the image side. The fourth lens (5), the sixth lens (7), the ninth lens (10), the tenth lens (11), the twelfth lens (13) and the fourteenth lens (15) all have convex surfaces facing the object side and convex surfaces facing the image side. The sixteenth lens (17) has a concave surface facing the object side and a convex surface facing the image side.

5. A catadioptric hybrid thermally stable ultra-short-throw projection lens according to claim 1, characterized in that, The coated mirror (1) is a plastic aspherical mirror, the first lens (2) and the third lens (4) are both plastic aspherical lenses, and the fifth lens (6) and the fifteenth lens (16) are both glass aspherical lenses.

6. A catadioptric hybrid thermally stable ultra-short-throw projection lens according to claim 1, characterized in that, The projection lens satisfies the condition: 0.12≤BFL / TTL≤0.16; Wherein, TTL is the total optical length of the projection lens; BFL is the optical back focal length of the projection lens.

7. A catadioptric hybrid thermally stable ultra-short-throw projection lens according to claim 1, characterized in that, In the cemented triplet lens, the refractive indices of the tenth lens (11) and the twelfth lens (13) are both lower than the refractive index of the eleventh lens (12), and the cemented triplet lens satisfies the following condition: 2mm≤T10≤4mm; 0.5mm≤T11≤1.5mm; 3mm≤T12≤4mm; |R12|+|R13|≥25.5; Wherein, T10 is the center thickness of the tenth lens 11, T11 is the center thickness of the eleventh lens (12), T12 is the center thickness of the twelfth lens (13), R12 is the curvature of the object side surface in the eleventh lens (12), and R13 is the curvature of the image side surface in the eleventh lens (12). The refractive index of the fourteenth lens (15) is less than that of the thirteenth lens (14), and the cemented doublet lens satisfies the following condition: 0.5mm≤T13≤1.5mm; 3.5mm≤T14≤5.0mm; Wherein, T13 is the center thickness of the thirteenth lens (14), and T14 is the center thickness of the fourteenth lens (15); The center thickness T16 of the sixteenth lens (17) is ≥3.5mm; In the projection lens, the maximum center thickness of all lenses is T, and T≤4.5mm.

8. A catadioptric hybrid thermally stable ultra-short-throw projection lens according to claim 1, characterized in that, The air gap between the aperture stop (22) and the ninth lens (10) is L1, and the air gap between the aperture stop (22) and the cemented triplet lens is L2, wherein 0.04mm≤L1 and 2.8mm≤L2.

9. A catadioptric hybrid thermally stable ultra-short-throw projection lens according to claim 1, characterized in that, The effective focal length of the coated mirror (1) is F1, 15mm≤F1≤25mm; The effective focal length of the first lens (2) is F2, -130mm≤F2≤-100mm; The effective focal length of the second lens (3) is F3, -70mm≤F3≤-40mm; The effective focal length of the third lens (4) is F4, -60mm≤F4≤-40mm; The effective focal length of the fourth lens (5) is F5, 25mm≤F5≤45mm; The effective focal length of the fifth lens (6) is F6, 140mm≤F6≤150mm; The effective focal length of the sixth lens (7) is F7, 20mm≤F7≤30mm The effective focal length of the seventh lens (8) is F8, -35mm≤F8≤-15mm The effective focal length of the eighth lens (9) is F9, -35mm≤F9≤-15mm The effective focal length of the ninth lens (10) is F10, 8mm ≤ F10 ≤ 18mm. The effective focal length of the tenth lens (11) is F11, 62mm≤F11≤82mm The effective focal length of the eleventh lens (12) is F12, -16mm≤F12≤-6mm The effective focal length of the twelfth lens (13) is F13, 45mm≤F13≤65mm. The effective focal length of the thirteenth lens (14) is F14, -15mm≤F14≤-5mm The effective focal length of the fourteenth lens (15) is F15, 52mm≤F15≤72mm The effective focal length of the fifteenth lens (16) is F16, 20mm≤F16≤40mm The effective focal length of the sixteenth lens (17) is F17,20mm≤F17≤40mm.

10. A catadioptric hybrid thermally stabilized ultra-short-throw projection lens according to claim 1, characterized in that, Starting from the image side, the media constituting the back focal length of the projection lens are, in order, air, Eagle XG glass, air, H-K9L prism, air, D263 protective glass, and air, with axial thicknesses of 0.307mm, 0.7mm, 1.0mm, 12.0mm, 7.76mm, 1.1mm, and 1.338mm, respectively.

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