A large aperture projection lens

Abstract

This invention relates to a large-aperture projection lens, comprising a first lens, a second lens, a third lens, a fourth lens, an aperture stop, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially along the optical axis. The first, fourth, fifth, seventh, and eighth lenses have positive optical power, while the second, third, and sixth lenses have negative optical power. The sixth and seventh lenses are cemented doublet lenses and also have positive optical power. By rationally setting the focal length and entrance pupil diameter of the lens, the lens achieves a large aperture, small size, and low cost. It also remains in focus even under conditions of significant temperature differences, exhibits stable performance, high projection quality, and a wide range of applications.

Description

Technical Field

[0001] This invention belongs to the field of optical lens technology, and specifically relates to a large aperture projection lens. Background Technology

[0002] With the rapid development of new energy vehicles, the comfort of in-vehicle space has been significantly improved, leading to a gradual increase in in-vehicle entertainment options. Among the many entertainment options, in-vehicle TVs once dominated, but due to limited interior space and safety considerations, the screen size of in-vehicle TVs is generally small, which undoubtedly limits the passenger's viewing experience and fails to meet the modern consumer's demand for diversified and immersive entertainment interaction. Against this backdrop, projection equipment, as a solution that can project a large image in a small space, has gradually attracted market attention.

[0003] However, traditional projectors are often large in size, making them difficult to install in the limited space of a vehicle. Furthermore, the in-vehicle environment places more stringent demands on projection equipment, requiring it to withstand extreme temperature changes and vibrations during vehicle movement. Traditional automotive projector lenses also have relatively small apertures, resulting in limitations in practical applications, primarily in brightness, focusing range, and image resolution. These factors restrict the use of projection equipment in in-vehicle spaces. For example, the smaller aperture reduces the amount of light entering the camera, leading to lower brightness in the projected image, especially noticeable in low-light environments. Therefore, the shortcomings of traditional projectors in terms of brightness, stability, and environmental adaptability present numerous challenges in practical applications, hindering their use in in-vehicle spaces. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned problems by proposing a large aperture projection lens. This lens features a large aperture, small size, and low cost. It also maintains focus even under environmental conditions with a large temperature difference of -40℃ to 85℃, exhibits stable performance, high projection quality, and a wide range of applications.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] The present invention proposes a large-aperture projection lens, comprising a first lens, a second lens, a third lens, a fourth lens, an aperture stop, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially along the optical axis, wherein:

[0007] The first, fourth, fifth, seventh, and eighth lenses have positive optical power, the second, third, and sixth lenses have negative optical power, and the sixth and seventh lenses are cemented doublet lenses with positive optical power.

[0008] Large aperture projection lenses also meet the following conditions:

[0009]

[0010] Where f is the focal length of the large aperture projection lens, in mm; and D is the entrance pupil diameter, in mm.

[0011] Preferably, the large aperture projection lens also meets the following conditions:

[0012]

[0013] Where f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, and f3 is the effective focal length of the third lens, in mm.

[0014] Preferably, the large aperture projection lens also meets the following conditions:

[0015]

[0016] Wherein, SD1 is the edge ray height of the object side of the first lens, and SD8 is the edge ray height of the image side of the eighth lens.

[0017] Preferably, the first lens is a biconvex lens or a convex-plano lens, the second lens is a convex-concave lens or a biconcave lens, the third lens is a biconcave lens, the fourth lens is a biconvex lens or a convex-plano lens, the fifth lens is a plano-convex lens or a concave-convex lens, the sixth lens is a plano-concave lens or a biconcave lens, the seventh lens is a biconvex lens, and the eighth lens is a convex-plano lens or a biconvex lens. Furthermore, the second, third, fourth, fifth, sixth, and seventh lenses are all spherical glass lenses, and the first and eighth lenses are both spherical glass lenses or aspherical glass lenses. The large-aperture projection lens also satisfies the following conditions:

[0018] <![CDATA[21.8<f1<39.5]]> <![CDATA[13.06<R 11 <33.94]]> <![CDATA[-∞<R 12 <-98.27]]> <![CDATA[-35.9<f2<-12.05]]> <![CDATA[-58.02<R 21 <150.18]]> <![CDATA[6.02<R 22 <12.11]]> <![CDATA[-14.7<f3-10.2]]> <![CDATA[-35.51<R 31 <-9.97]]> <![CDATA[15.02<R 32 <26.16]]> <![CDATA[15.8<f4<27.3]]> <![CDATA[20.15<R 41 <1371.2]]> <![CDATA[-28.78<R 42 <+∞]]> <![CDATA[28.88<f5<46.1]]> <![CDATA[-∞<R 51 <-12.17]]> <![CDATA[-28.91<R 52 <-8.56]]> <![CDATA[-33.1<f6<-6.4]]> <![CDATA[-12.25<R 61 <+∞]]> <![CDATA[10.57<R 62 <59.67]]> <![CDATA[13.6<f7<28.7]]> <![CDATA[10.57<R 71 <59.67]]> <![CDATA[-56.86<R 72 <-7.12]]> <![CDATA[14.8<f8<49.4]]> <![CDATA[16.95<R 81 <33.32]]> <![CDATA[-∞<R 82 <-12.6]]>

[0019] Where f1 to f8 are the focal lengths of the first to eighth lenses, respectively; R 11 R 21 R 31 R 41 R 51 R 61 R 71 R 81 The radii of curvature of the object-side surfaces of the first to eighth lenses are, in order; R 12 R 22 R 32 R 42 R 52 R 62 R 72 R 82The radii of curvature of the image-side surfaces of the first to eighth lenses are listed in mm; "-" indicates a negative direction.

[0020] Preferably, the large aperture projection lens also meets the following conditions:

[0021] 2≤th4+th6≤5

[0022] Where th4 is the median thickness of the fourth lens and th6 is the median thickness of the sixth lens, in mm.

[0023] Preferably, the large aperture projection lens also meets the following conditions:

[0024] 100≤abv²+abv⁷≤168

[0025] Where abv2 is the Abbe number of the second lens and abv7 is the Abbe number of the seventh lens.

[0026] Preferably, the large aperture projection lens also meets the following conditions:

[0027] 34.5≤OAL≤62

[0028] Where OAL is the axial distance from the object side of the first lens to the image side of the eighth lens, in mm.

[0029] Preferably, the large aperture projection lens further includes an optical engine located on the image side of the eighth lens, the optical engine including a galvanometer, a prism and a DMD chip arranged sequentially along the optical axis.

[0030] Preferably, the large aperture projection lens also meets the following conditions:

[0031] CRA≤2°, 20≤BFL≤30

[0032] Where CRA is the maximum ray angle of the large aperture projection lens on the imaging surface of the DMD chip, and BFL is the on-axis distance from the image side of the eighth lens to the imaging surface of the DMD chip, in mm.

[0033] Preferably, the large aperture projection lens also meets the following conditions:

[0034]

[0035] Wherein, FOV is the full field of view of the maximum field of view, DIST is the maximum optical distortion from the center to the edge of the field of view, and RI is the relative illumination of the large aperture projection lens on the imaging surface of the DMD chip.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] This lens employs eight lenses, and through the rational allocation of optical power, it achieves a compact structure and small size, with a total lens length within 62mm. This helps reduce costs while ensuring image quality. The rational lens allocation corrects various aberrations and improves edge image quality, thus enhancing overall image quality. The maximum aperture of F1.6 allows for greater light output, enabling more light to pass through and providing higher brightness output while maintaining device miniaturization. This ensures users can enjoy a clear and bright projected image even in daylight or brightly lit environments. Furthermore, the large aperture projection lens excels in fast focusing and reduced exposure time, effectively minimizing image blur caused by vehicle vibrations and ensuring image stability. The rational use of complementary materials ensures the lens remains in focus in environments ranging from -40℃ to +85℃, enabling stable operation in the high and low temperature environments of a vehicle and meeting stringent usage requirements. It is compatible with various DMD chips, such as the 0.33” DMD chip, providing sufficient projection brightness and size, resulting in a clear, sharp, high-contrast, accurate color reproduction, high pixel count, and excellent image quality. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of the large aperture projection lens in Embodiment 1 of the present invention;

[0039] Figure 2 The longitudinal spherical aberration diagram, astigmatism diagram, and distortion diagram of the large aperture projection lens in Embodiment 1 of the present invention are shown below.

[0040] Figure 3 This is the MTF diagram of the large aperture projection lens in Embodiment 1 of the present invention;

[0041] Figure 4 This is a schematic diagram of the structure of the large aperture projection lens in Embodiment 2 of the present invention;

[0042] Figure 5 The longitudinal spherical aberration diagram, astigmatism diagram, and distortion diagram of the large aperture projection lens in Embodiment 2 of the present invention are shown below.

[0043] Figure 6 This is the MTF diagram of the large aperture projection lens in Embodiment 2 of the present invention;

[0044] Figure 7 This is a schematic diagram of the structure of the large aperture projection lens in Embodiment 3 of the present invention;

[0045] Figure 8 The longitudinal spherical aberration diagram, astigmatism diagram, and distortion diagram of the large aperture projection lens in Embodiment 3 of the present invention are shown below.

[0046] Figure 9 This is the MTF diagram of the large aperture projection lens in Embodiment 3 of the present invention;

[0047] Figure 10 This is a schematic diagram of the structure of the large aperture projection lens in Embodiment 4 of the present invention;

[0048] Figure 11 The longitudinal spherical aberration diagram, astigmatism diagram, and distortion diagram of the large aperture projection lens in Embodiment 4 of the present invention are shown below.

[0049] Figure 12 This is the MTF diagram of the large aperture projection lens in Embodiment 4 of the present invention.

[0050] Explanation of reference numerals in the attached diagram: L1, first lens; L2, second lens; L3, third lens; L4, fourth lens; L5, fifth lens; L6, sixth lens; L7, seventh lens; L8, eighth lens; L9, galvanometer; L10, prism; ST, aperture stop; CG, protective glass; Sensor, DMD chip. Detailed Implementation

[0051] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0052] It should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application.

[0053] This application's lens features a large aperture of Fno1.6, which not only reduces the size of the projection device but also significantly improves the projection effect. The large aperture lens allows more light to pass through, thus providing higher brightness output while maintaining the device's miniaturization. This means that even in daylight or brightly lit environments, users can enjoy a clear and bright projected image. Furthermore, the large aperture lens excels in fast focusing and reduced exposure time, effectively minimizing image blur caused by vehicle vibrations and ensuring the stability of the projected image. Simultaneously, the lens can operate stably in the high and low temperature environments of an in-vehicle environment, meeting stringent usage requirements. Therefore, the large aperture lens brings new possibilities to in-vehicle entertainment systems, providing not only an immersive viewing experience but also meeting passengers' demands for high-quality entertainment content without compromising vehicle safety and comfort. Thus, this large aperture projection lens contributes to the development of in-vehicle entertainment technology and brings more diversified entertainment experiences to the new energy vehicle market.

[0054] A large-aperture projection lens includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, an aperture stop ST, a fifth lens L5, a sixth lens L6, a seventh lens L7, and an eighth lens L8 arranged sequentially along the optical axis, wherein:

[0055] The first lens L1, the fourth lens L4, the fifth lens L5, the seventh lens L7, and the eighth lens L8 have positive optical power; the second lens L2, the third lens L3, and the sixth lens L6 have negative optical power; and the sixth lens L6 and the seventh lens L7 are cemented doublet lenses and have positive optical power.

[0056] Large aperture projection lenses also meet the following conditions:

[0057]

[0058] Where f is the focal length of the large aperture projection lens, in mm; and D is the entrance pupil diameter, in mm.

[0059] The first lens L1 provides sufficient light height for the edge field of view, which helps reduce optical distortion at the edges and provides a solution for small-diameter front-end lenses. The second lens L2 can quickly compress the light height, working with the first lens L1 to reduce the head size. The third lens L3 shares the optical power of the second lens L2, provides a deflection angle for edge rays, smooths the light, and reduces field aberrations. The fourth lens L4 has a near-plane curvature on its object side and a convex surface on its image side. The higher light height on the convex surface provides some field curvature compensation for the system, resulting in a high MTF concentration of the optical system. It also connects the front and rear lens groups, making the light path near the aperture stop ST smooth, which helps reduce lens sensitivity and improve product yield and reliability. The aperture stop ST is located between the fourth lens L4 and the fifth lens L5, meaning the aperture stop ST is located in the middle of the lens. The fifth lens, L5, helps balance the upper and lower light rays at the edge of the field of view, ensuring edge brightness while reducing the principal ray angle of the lens, allowing the lens to better match the projection light system. The sixth lens, L6, can be set to have a higher Abbe number, which can reduce the chromatic aberration introduced into the system. The sixth lens, L6, can be set to have a lower Abbe number, which, together with the seventh lens, L7, forms a positive and negative power combination to reduce the chromatic aberration of the entire system. The seventh lens, L7, is also made of a high Abbe number material, reducing the introduction of chromatic aberration and forming a complementary relationship between chromatic aberration and spherical aberration with the negative lens. The sixth lens, L6, and the seventh lens, L7, form a cemented doublet, which can greatly reduce the overall chromatic aberration of the system, ensuring low levels of axial and transverse chromatic aberration, and achieving clarity for both monochromatic and mixed-color light. The eighth lens, L8, has a high Abbe number and a flat surface, which helps reduce spherical aberration and correct the principal ray incident angle.

[0060] Furthermore, f / D can be 1.64, 1.6, or 1.65. Meeting these conditions allows the lens to have a large aperture, suitable for both low-cost, low-light projection devices and high-light projection devices, giving the lens a wide range of applications and meeting the needs of most projection scenarios on the market. Additionally, f can be 20.95, 21.2, or 20.45 mm. Meeting these conditions, when matched with a 0.33” DMD chip, allows the lens to have a wide-angle feature, providing a broad viewing angle and projecting the required image size even at short distances. Beyond the upper limit of the range, the lens angle decreases, resulting in a smaller image size; below the lower limit, the lens angle increases, requiring a more complex lens design, which fails to meet the miniaturization and low-cost requirements.

[0061] In one embodiment, the large-aperture projection lens also satisfies the following condition:

[0062]

[0063] Where f1 is the effective focal length of the first lens L1, f2 is the effective focal length of the second lens L2, and f3 is the effective focal length of the third lens L3, in mm.

[0064] Specifically, f1 / (f2+f3) can be: -1.05, -1.09, -0.86, -1.18, -0.97. Satisfying the above conditions, the first lens L1, the second lens L2, and the third lens L3 form a positive-negative-negative combination, limiting the effective focal length to a reasonable range. This allows for the use of positive-negative lens combinations to achieve a small aperture, low distortion, reduce aberrations, and improve overall sharpness. Exceeding this range results in uneven optical power distribution, making it difficult to achieve a small-head solution.

[0065] In one embodiment, the large-aperture projection lens also satisfies the following condition:

[0066]

[0067] Wherein, SD1 is the edge ray height of the object side of the first lens L1, and SD8 is the edge ray height of the image side of the eighth lens L8.

[0068] Specifically, SD1 / SD8 can be 1.3, 1.41, 1.45, 1.33, or 1.36. Meeting the above conditions ensures that the diameter of the first lens L1 and the eighth lens L8 are very close, allowing the head and tail diameters to be essentially the same. This facilitates miniaturization of the overall projection design, reduces the exposed projection area, improves integration, minimizes discomfort from exposure, and enhances the aesthetics of the projection device within the vehicle. Exceeding the upper limit results in an excessively large head size, reducing the aesthetics of the application; falling below the lower limit results in an excessively small head size, increasing design complexity and requiring more lenses to compensate for optical distortion caused by the small head, which is detrimental to cost reduction.

[0069] In one embodiment, the first lens L1 is a biconvex lens or a convex-plano lens, the second lens L2 is a convex-concave lens or a biconcave lens, the third lens L3 is a biconcave lens, the fourth lens L4 is a biconvex lens or a convex-plano lens, the fifth lens L5 is a plano-convex lens or a concave-convex lens, the sixth lens L6 is a plano-concave lens or a biconcave lens, the seventh lens L7 is a biconvex lens, and the eighth lens L8 is a convex-plano lens or a biconvex lens. Furthermore, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, and the seventh lens L7 are all spherical glass lenses, and the first lens L1 and the eighth lens L8 are both spherical glass lenses or aspherical glass lenses. The large-aperture projection lens also satisfies the following conditions:

[0070] <![CDATA[21.8<f1<39.5]]> <![CDATA[13.06<R 11 <33.94]]> <![CDATA[-∞<R 12 <-98.27]]> <![CDATA[-35.9<f2<-12.05]]> <![CDATA[-58.02<R 21 <150.18]]> <![CDATA[6.02<R 22 <12.11]]> <![CDATA[-14.7<f3-10.2]]> <![CDATA[-35.51<R 31 <-9.97]]> <![CDATA[15.02<R 32 <26.16]]> <![CDATA[15.8<f4<27.3]]> <![CDATA[20.15<R 41 <1371.2]]> <![CDATA[-28.78<R 42 <+∞]]> <![CDATA[28.88<f5<46.1]]> <![CDATA[-∞<R 51 <-12.17]]> <![CDATA[-28.91<R 52 <-8.56]]> <![CDATA[-33.1<f6<-6.4]]> <![CDATA[-12.25<R 61 <+∞]]> <![CDATA[10.57<R 62 <59.67]]> <![CDATA[13.6<f7<28.7]]> <![CDATA[10.57<R 71 <59.67]]> <![CDATA[-56.86<R 72 <-7.12]]> <![CDATA[14.8<f8<49.4]]> <![CDATA[16.95<R 81 <33.32]]> <![CDATA[-∞<R 82 <-12.6]]>

[0071] Where f1 to f8 are the focal lengths of the first lens L1 to the eighth lens L8, respectively; R 11 R 21 R 31 R 41 R 51 R 61 R 71 R 81 The radii of curvature of the object-side surfaces of lenses L1 through L8 are, in order; R 12 R 22 R 32 R 42 R 52 R 62 R 72 R 82 The radii of curvature of the image-side surfaces of lenses L1 through L8 are in mm; "-" indicates a negative direction.

[0072] In one embodiment, the large-aperture projection lens also satisfies the following condition:

[0073] 2≤th4+th6≤5

[0074] Where th4 is the median thickness of the fourth lens L4 and th6 is the median thickness of the sixth lens L6, in mm.

[0075] Specifically, th4 + th6 can be 3.12, 4.75, 2.99, 3.51, and 4.96 mm. Due to the distribution of optical power, the fourth lens L4 and the sixth lens L6 are often made of materials with high refractive index. Due to their inherent characteristics, materials with high refractive index have low short-wavelength transmittance. To enhance the short-wavelength transmittance of the lens, the thickness of the high-refractive-index material must be strictly controlled. If the above conditions are met, the overall thickness of the high-refractive-index material can be controlled within a reasonable range, ensuring that the difference between the short-wavelength and long-wavelength transmittance of the lens is small and avoiding color temperature deviation problems. If the upper limit is exceeded, the fourth lens L4 and the sixth lens L6 will be too thick, which will easily cause the short-wavelength transmittance to be too low, affecting the color temperature and brightness of the projected image. If the lower limit is exceeded, the lens thickness will be too thin, which is not conducive to processing.

[0076] In one embodiment, the large-aperture projection lens also satisfies the following condition:

[0077] 100≤abv²+abv⁷≤168

[0078] Where abv2 is the Abbe number of the second lens L2, and abv7 is the Abbe number of the seventh lens L7.

[0079] Specifically, abv6+abv8 can be: 112.35, 133.78, 149.94, 120.48, 150.62, 165.3. The sixth lens L6 and the eighth lens L8 are made of low-refractive-index, high-Abbe-number materials, and their material range is close to that of negative dn / dt (refractive-index temperature coefficient) materials, satisfying the above conditions. The sixth lens L6 and the eighth lens L8 are selected with suitable negative dn / dt materials to compensate for the excessive expansion and contraction of the back focal length at high and low temperatures, enabling the lens to achieve an optically athermal design. This allows it to meet the temperature range of -40℃ to 85℃ in automotive applications, and without plastic lenses, it can cover high temperatures up to 105℃. Beyond these limits, the material selection cannot meet the high and low temperature compensation requirements.

[0080] In one embodiment, the large-aperture projection lens also satisfies the following condition:

[0081] 34.5≤OAL≤62

[0082] Where OAL is the axial distance from the object side of the first lens L1 to the image side of the eighth lens L8, in mm.

[0083] Specifically, OAL can take any value within this range, such as 34.7, 50.5, 56.95, 57, and 62, in mm. Meeting the above conditions results in a small, compact lens that meets miniaturization requirements; exceeding the upper limit fails to meet miniaturization requirements; falling below the lower limit compresses the lens space, hindering sharpness improvement, increasing material costs, and potentially leading to excessively high costs.

[0084] In one embodiment, the large aperture projection lens further includes an optical engine located on the image side of the eighth lens L8, the optical engine including a galvanometer L9, a prism L10 and a DMD chip sensor arranged sequentially along the optical axis.

[0085] Specifically, the galvanometer L9 is used to vibrate at high frequency in different directions, which expands the pixel range of the image on the original pixels for a short time. It uses the persistence of vision effect to increase the number of pixels that the human eye can recognize, thereby improving the projection resolution. The prism L10 is an equivalent flat plate used to converge light from different light sources, such as providing appropriate reflection and refraction angles for each light ray. These are technologies well known to those skilled in the art and will not be described in detail here.

[0086] In one embodiment, the large-aperture projection lens also satisfies the following condition:

[0087] CRA≤2°, 20≤BFL≤30

[0088] Wherein, CRA is the maximum ray angle of the large aperture projection lens on the imaging surface of the DMD chip sensor, and BFL is the on-axis distance from the image side of the eighth lens L8 to the imaging surface of the DMD chip sensor, in mm.

[0089] Specifically, CRA can take any value within this range, such as 0.95, 1.6, 1.35, 0.8, or 0.5, in degrees. Meeting these conditions ensures the lens's telecentricity is within a small range, guaranteeing alignment between the lens and the light output direction, improving light output efficiency from the center to the edge of the image, and avoiding uneven brightness. Exceeding this range results in excessive telecentricity, easily leading to low light output efficiency and affecting image brightness and uniformity. Additionally, FFL can be 20.5, 22, 25.6, 27.7, or 28.6 mm. BFL also includes the thickness of the galvanometer L9 and prism L10 of a large-aperture projection lens. Meeting these conditions allows the lens to be matched with a larger back focal length, sufficient prism space, and light output / heat dissipation space, accommodating more projection engines. Exceeding the upper limit results in an excessively large back focal length, increasing lens design difficulty and cost; below the lower limit, the back focal length is too small, hindering illumination path arrangement and engine heat dissipation, affecting the user experience.

[0090] In one embodiment, the large-aperture projection lens also satisfies the following condition:

[0091]

[0092] Wherein, FOV is the full field of view of the maximum field of view, DIST is the maximum optical distortion from the center to the edge of the field of view, and RI is the relative illumination of the large aperture projection lens on the imaging surface of the DMD chip sensor.

[0093] Specifically, FOV / DIST can be: -59.12, -69.78, -47.6, -73.1, -76.64, in ° / %. Meeting these conditions ensures that, under wide-angle FOV conditions, the maximum optical distortion can be controlled within a reasonable range, and is suitable for all-glass distortion compensation, keeping the lens within a reasonable range for both FOV and DIST, guaranteeing low distortion in the projected size and image area. Additionally, DIST can be: -0.32%, -0.47%, -0.37%, -0.44%, -0.4%. Meeting these conditions ensures that the lens optical distortion is within a reasonable range. At this point, the projected TV distortion is less than 0.5%, and the human eye can hardly perceive the image distortion, contributing to improved viewing comfort. Exceeding this range results in excessive optical distortion, causing significant image distortion and potentially causing viewing discomfort. RI can take any value within this range, such as: 65%, 68%, 72%, 75%, 78%. Meeting the above conditions ensures good illumination uniformity within the imaging range and prevents vignetting caused by low edge illumination. Low relative illumination makes vignetting more likely, affecting viewing comfort.

[0094] For ease of understanding, the following detailed embodiments are provided. The reference wavelength for the effective focal length, Abbe number, and refractive index in each embodiment is 550 nm.

[0095] Example 1:

[0096] like Figure 1 As shown, in this embodiment, the large-aperture projection lens includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, an aperture stop ST, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, a galvanometer L9, a prism L10, a protective glass CG, and a DMD chip, arranged sequentially along the optical axis. The sixth lens L6 and the seventh lens L7 form a cemented doublet. The focal length of this optical system is f = 20.93 mm, the aperture number Fno = 1.64, and the axial distance OAL from the object-side surface of the first lens L1 to the image-side surface of the eighth lens L8 is 57 mm. Therefore, this optical system can achieve a large aperture, miniaturization, and a small head design.

[0097] Specifically, the values ​​of the lens parameters in this embodiment are shown in Table 1 below:

[0098] Table 1

[0099] Face number Surface type Radius of curvature (mm) Thickness (mm) Refractive index Abbe number S0 spherical unlimited 3100.000 S1 spherical 21.818 5.695 1.593 68.342 S2 spherical -118.210 0.161 S3 spherical 140.188 7.213 1.438 94.523 S4 spherical 9.119 4.109 S5 spherical -11.976 1.300 1.648 33.888 S6 spherical 20.450 0.801 S7 spherical 80.400 3.377 1.954 32.319 S8 spherical -20.684 4.866 ST(S9) spherical unlimited 8.813 S10 spherical unlimited 5.289 1.593 68.342 S11 spherical -18.915 1.289 S12 spherical unlimited 1.387 1.750 34.989 S13 spherical 16.704 6.549 1.569 71.304 S14 spherical -42.032 0.150 S15 spherical 25.601 5.999 1.593 68.342 S16 spherical unlimited 3.92 S17 spherical unlimited 2.000 1.523 58.571 S18 spherical unlimited 2.000 S19 spherical unlimited 15.000 1.713 53.833 S20 spherical unlimited 1.000 S21 spherical unlimited 1.100 1.510 62.911 S22 spherical unlimited 0.303 S23 spherical unlimited 0.000

[0100] like Figure 1 As shown, surface number S0 represents the object surface, and surface numbers S1, S3, S5, S7, S10, S12, S13, S15, S17, S19 to S21 represent the object surface of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, the galvanometer L9, the prism L10, and the protective glass CG, respectively. Surface numbers S2, S4, S6, S8... S11, S13, S14, S16, S18, S20 to S22 represent the image-side surfaces of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, the galvanometer L9, the prism L10, and the protective glass CG, respectively. The cemented surface of the cemented lens assembly is considered as one surface. ST represents the aperture stop, i.e., surface number S9. Surface number S23 represents the imaging surface of the DMD chip. The DMD chip is a digital micromirror device (DMD).

[0101] Figure 2 The longitudinal spherical aberration diagram (LONGITUD INAL SPHERICAL ABER.) of the optical system represents the deviation of the convergence focal point of light rays of different wavelengths after passing through the lens. The vertical axis of the LONGITUD INAL SPHERICAL ABER. represents the normalized pupil coordinates from the pupil center to the pupil edge, while the horizontal axis represents the distance (in mm) from the imaging surface of the DMD chip to the intersection of the light ray and the optical axis. As shown in the LONGITUD INAL SPHERICAL ABER., in this embodiment, the deviation of the convergence focal point of light rays of different wavelengths tends to be consistent, effectively suppressing blur or halo in the image, and minimizing the difference between single-wavelength and polychromatic wavelengths. Figure 2 It also includes the field curvature diagrams of the optical system, where the S-curve represents the sagittal field curvature at a wavelength of 550 nm, and the T-curve represents the meridional field curvature at a wavelength of 550 nm. As can be seen from the figure, the field curvature of the optical system is small, and the field curvature and astigmatism of each field of view are well corrected. Figure 2 It also includes the optical system distortion diagram. As can be seen from the diagram, the maximum optical distortion is within 1%, the image deformation caused by the main beam is small, and the imaging quality of the system is excellent. Figure 3 The graph shows the relationship between MTF and frequency under different fields of view. The center and edges of the field of view exhibit clear imaging at various frequencies, and the MTF for all fields of view is greater than 0.66 at the limiting frequency of 90 lp / mm. In summary, the longitudinal spherical aberration, field curvature, and distortion of this optical system are well controlled, resulting in excellent imaging quality.

[0102] Example 2:

[0103] like Figure 4 As shown, in this embodiment, the large-aperture projection lens includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, an aperture stop ST, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, a galvanometer L9, a prism L10, a protective glass CG, and a DMD chip, arranged sequentially along the light emission direction. The sixth lens L6 and the seventh lens L7 form a cemented doublet. The focal length of this optical system is f = 20.94 mm, the aperture number Fno = 1.65, and the axial distance OAL from the object-side surface of the first lens L1 to the image-side surface of the eighth lens L8 is 60 mm. This optical system achieves a large aperture, miniaturization, and a small head design.

[0104] Specifically, the values ​​of the lens parameters in this embodiment are shown in Table 2 below:

[0105] Table 2

[0106]

[0107]

[0108] like Figure 4 As shown, surface number S0 represents the object surface, and surface numbers S1, S3, S5, S7, S10, S12, S13, S15, S17, S19 to S21 represent the object surface of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, the galvanometer L9, the prism L10, and the protective glass CG, respectively. Surface numbers S2, S4, S6, S8... S11, S13, S14, S16, S18, S20 to S22 represent the image-side surfaces of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, the galvanometer L9, the prism L10, and the protective glass CG, respectively. The cemented surface of the cemented lens assembly is considered as one surface. ST represents the aperture stop, i.e., surface number S9. Surface number S23 represents the imaging surface of the DMD chip. The DMD chip is a digital micromirror device (DMD).

[0109] Figure 5The longitudinal spherical aberration diagram (LONGITUD INAL SPHERICAL ABER.) of the optical system represents the deviation of the convergence focal point of light rays of different wavelengths after passing through the lens. The vertical axis of the LONGITUD INAL SPHERICAL ABER. represents the normalized pupil coordinates from the pupil center to the pupil edge, while the horizontal axis represents the distance (in mm) from the imaging surface of the DMD chip to the intersection of the light ray and the optical axis. As shown in the LONGITUD INAL SPHERICAL ABER., in this embodiment, the deviation of the convergence focal point of light rays of different wavelengths tends to be consistent, effectively suppressing blur or halo in the image, and minimizing the difference between single-wavelength and polychromatic wavelengths. Figure 5 It also includes the field curvature diagrams of the optical system, where the S-curve represents the sagittal field curvature at a wavelength of 550 nm, and the T-curve represents the meridional field curvature at a wavelength of 550 nm. As can be seen from the figure, the field curvature of the optical system is small, and the field curvature and astigmatism of each field of view are well corrected. Figure 5 It also includes the optical system distortion diagram. As can be seen from the diagram, the maximum optical distortion is within 1%, the image deformation caused by the main beam is small, and the imaging quality of the system is excellent. Figure 6 The graph shows the relationship between MTF and frequency under different fields of view. The center and edges of the field of view exhibit clear imaging at various frequencies, and the MTF for all fields of view is greater than 0.64 at the limiting frequency of 90 lp / mm. In summary, the longitudinal spherical aberration, field curvature, and distortion of this optical system are well controlled, resulting in excellent imaging quality.

[0110] Example 3:

[0111] like Figure 7 As shown, in this embodiment, the large-aperture projection lens includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, an aperture ST, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, a galvanometer L9, a prism L10, a protective glass CG, and a DMD chip, arranged sequentially along the light emission direction. The sixth lens L6 and the seventh lens L7 form a cemented doublet. The effective focal length of this optical system is f = 20.905 mm, the aperture number Fno = 1.64, and the axial distance OAL from the object-side surface of the first lens L1 to the image-side surface of the eighth lens L8 is 36.6 mm. Therefore, this optical system can achieve a large aperture, miniaturization, and a small head design.

[0112] Specifically, the values ​​of the lens parameters in this embodiment are shown in Tables 3 and 4 below:

[0113] Table 3

[0114] Face number Surface type Radius of curvature (mm) Thickness (mm) Refractive index Abbe number S0 spherical unlimited 3000 S1 aspherical 17.006 4.699 1.593 68.34 S2 aspherical unlimited 0.100 S3 spherical 16.068 4.582 1.497 81.61 S4 spherical 7.049 2.668 S5 spherical -18.990 1.350 1.740 27.6 S6 spherical 20.000 0.150 S7 spherical 22.153 1.381 2.00 25.43 S8 spherical 5344.083 0.102 ST(S9) spherical unlimited 4.719 S10 spherical -17.277 1.573 1.593 68.34 S11 spherical -10.576 0.893 S12 spherical -7.259 1.350 1.75 34.5 S13 spherical 54.698 5.411 1.593 68.34 S14 spherical -10.770 0.100 S15 aspherical 21.659 5.598 1.593 68.34 S16 aspherical -16.865 4.100 S17 spherical unlimited 2.000 1.523 58.571 S18 spherical unlimited 2.000 S19 spherical unlimited 15.000 1.713 53.833 S20 spherical unlimited 1.000 S21 spherical unlimited 1.100 1.510 62.911 S22 spherical unlimited 0.303 S23 spherical unlimited 0

[0115] In this embodiment, the surfaces of the first lens L1 and the eighth lens L8 are both aspherical and satisfy the following aspherical equation:

[0116]

[0117] In the formula, z is the sag, c is the curvature, y is the radial coordinate, k is the coefficient of the conic quadratic curve, and A i These are the coefficients of higher-order terms.

[0118] Table 4

[0119]

[0120]

[0121] like Figure 7 As shown, surface number S0 represents the object surface, and surface numbers S1, S3, S5, S7, S10, S12, S13, S15, S17, S19 to S21 represent the object surface of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, the galvanometer L9, the prism L10, and the protective glass CG, respectively. Surface numbers S2, S4, S6, S8... S11, S13, S14, S16, S18, S20 to S22 represent the image-side surfaces of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, the galvanometer L9, the prism L10, and the protective glass CG, respectively. The cemented surface of the cemented lens assembly is considered as one surface. ST represents the aperture stop, i.e., surface number S9. Surface number S23 represents the imaging surface of the DMD chip. The DMD chip is a digital micromirror device (DMD).

[0122] Figure 8 The longitudinal spherical aberration diagram (LONGITUD INAL SPHERICAL ABER.) of the optical system represents the deviation of the convergence focal point of light rays of different wavelengths after passing through the lens. The vertical axis of the LONGITUD INAL SPHERICAL ABER. represents the normalized pupil coordinates from the pupil center to the pupil edge, while the horizontal axis represents the distance (in mm) from the imaging surface of the DMD chip to the intersection of the light ray and the optical axis. As shown in the LONGITUD INAL SPHERICAL ABER., in this embodiment, the deviation of the convergence focal point of light rays of different wavelengths tends to be consistent, effectively suppressing blur or halo in the image, and minimizing the difference between single-wavelength and polychromatic wavelengths. Figure 8It also includes the field curvature diagrams of the optical system, where the S-curve represents the sagittal field curvature at a wavelength of 550 nm, and the T-curve represents the meridional field curvature at a wavelength of 550 nm. As can be seen from the figure, the field curvature of the optical system is small, and the field curvature and astigmatism of each field of view are well corrected. Figure 8 It also includes the optical system distortion diagram. As can be seen from the diagram, the maximum optical distortion is within 1%, the image deformation caused by the main beam is small, and the imaging quality of the system is excellent. Figure 9 The graph shows the relationship between MTF and frequency under different fields of view. The center and edges of the field of view exhibit clear imaging at various frequencies, and the MTF for all fields of view is greater than 0.62 at the limiting frequency of 90 lp / mm. In summary, the longitudinal spherical aberration, field curvature, and distortion of this optical system are well controlled, resulting in excellent imaging quality.

[0123] Example 4:

[0124] like Figure 10 As shown in the embodiment, the large-aperture projection lens includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, an aperture ST, a fifth lens L5, a sixth lens L6, a seventh lens L7, an eighth lens L8, a galvanometer L9, a prism L10, a protective glass CG, and a DMD chip, arranged sequentially along the light emission direction. The sixth lens L6 and the seventh lens L7 form a cemented doublet lens. The effective focal length of this optical system is f = 20.93 mm, the aperture number Fno = 1.64, and the axial distance OAL from the object-side surface of the first lens L1 to the image-side surface of the eighth lens L8 is 56.5 mm. Therefore, this optical system can achieve a large aperture, miniaturization, and a small head design.

[0125] Specifically, the values ​​of the lens parameters in this embodiment are shown in Table 5 below:

[0126] Table 5

[0127]

[0128]

[0129] like Figure 10As shown, surface number S0 represents the object surface, and surface numbers S1, S3, S5, S7, S10, S12, S13, S15, S17, S19 to S21 represent the object surface of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, the galvanometer L9, the prism L10, and the protective glass CG, respectively. Surface numbers S2, S4, S6, S8... S11, S13, S14, S16, S18, S20 to S22 represent the image-side surfaces of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, the galvanometer L9, the prism L10, and the protective glass CG, respectively. The cemented surface of the cemented lens assembly is considered as one surface. ST represents the aperture stop, i.e., surface number S9. Surface number S23 represents the imaging surface of the DMD chip. The DMD chip is a digital micromirror device (DMD).

[0130] Figure 11 The longitudinal spherical aberration diagram (LONGITUD INAL SPHERICAL ABER.) of the optical system represents the deviation of the convergence focal point of light rays of different wavelengths after passing through the lens. The vertical axis of the LONGITUD INAL SPHERICAL ABER. represents the normalized pupil coordinates from the pupil center to the pupil edge, while the horizontal axis represents the distance (in mm) from the imaging surface of the DMD chip to the intersection of the light ray and the optical axis. As shown in the LONGITUD INAL SPHERICAL ABER., in this embodiment, the deviation of the convergence focal point of light rays of different wavelengths tends to be consistent, effectively suppressing blur or halo in the image, and minimizing the difference between single-wavelength and polychromatic wavelengths. Figure 11 It also includes the field curvature diagrams of the optical system, where the S-curve represents the sagittal field curvature at a wavelength of 550 nm, and the T-curve represents the meridional field curvature at a wavelength of 550 nm. As can be seen from the figure, the field curvature of the optical system is small, and the field curvature and astigmatism of each field of view are well corrected. Figure 11 It also includes the optical system distortion diagram. As can be seen from the diagram, the maximum optical distortion is within 1%, the image deformation caused by the main beam is small, and the imaging quality of the system is excellent. Figure 12 The graph shows the relationship between MTF and frequency under different fields of view. The center and edges of the field of view exhibit clear imaging at various frequencies, and the MTF of all fields of view is greater than 0.6 at the limiting frequency of 90 lp / mm. In summary, the longitudinal spherical aberration, field curvature, and distortion of this optical system are well controlled, resulting in excellent imaging quality.

[0131] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0132] The embodiments described above are merely specific and detailed examples of the embodiments described in this application, and should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A large aperture projection lens, characterized in that: The large aperture projection lens comprises eight lenses arranged sequentially along the optical axis: a first lens (L1), a second lens (L2), a third lens (L3), a fourth lens (L4), an aperture stop (ST), a fifth lens (L5), a sixth lens (L6), a seventh lens (L7), and an eighth lens (L8), for a total of eight lenses. The first lens (L1), the fourth lens (L4), the fifth lens (L5), the seventh lens (L7), and the eighth lens (L8) have positive optical power, the second lens (L2), the third lens (L3), and the sixth lens (L6) have negative optical power, and the sixth lens (L6) and the seventh lens (L7) are cemented doublet lenses and have positive optical power; The large-aperture projection lens also meets the following conditions: ； Where f is the focal length of the large aperture projection lens, in mm; and D is the entrance pupil diameter, in mm.

2. The large aperture projection lens as described in claim 1, characterized in that: The large-aperture projection lens also meets the following conditions: ； Where f1 is the effective focal length of the first lens (L1), f2 is the effective focal length of the second lens (L2), and f3 is the effective focal length of the third lens (L3), in mm.

3. The large aperture projection lens as described in claim 1, characterized in that: The large-aperture projection lens also meets the following conditions: ； Wherein, SD1 is the edge ray height of the object side of the first lens (L1), and SD8 is the edge ray height of the image side of the eighth lens (L8).

4. The large aperture projection lens as described in claim 1, characterized in that: The first lens (L1) is a biconvex lens or a convex-plano lens; the second lens (L2) is a convex-concave lens or a biconcave lens; the third lens (L3) is a biconcave lens; the fourth lens (L4) is a biconvex lens or a convex-plano lens; the fifth lens (L5) is a plano-convex lens or a concave-convex lens; the sixth lens (L6) is a plano-concave lens or a biconcave lens; the seventh lens (L7) is a biconvex lens; and the eighth lens (L8) is a convex-plano lens or a biconvex lens. Furthermore, the second lens (L2), third lens (L3), fourth lens (L4), fifth lens (L5), sixth lens (L6), and seventh lens (L7) are all spherical glass lenses; the first lens (L1) and the eighth lens (L8) are both spherical glass lenses or aspherical glass lenses. The large-aperture projection lens also satisfies the following conditions: ； Where f1 to f8 are the focal lengths of the first lens (L1) to the eighth lens (L8), respectively; R 11 R 21 R 31 R 41 R 51 R 61 R 71 R 81 The radii of curvature of the object-side surfaces of the first lens (L1) to the eighth lens (L8) are, in order; R 12 R 22 R 32 R 42 R 52 R 62 R 72 R 82 The radii of curvature of the image-side surfaces of the first lens (L1) to the eighth lens (L8) are in mm, respectively; "-" indicates the negative direction.

5. The large aperture projection lens as described in claim 1, characterized in that: The large-aperture projection lens also meets the following conditions: ； Wherein, th4 is the median thickness of the fourth lens (L4), and th6 is the median thickness of the sixth lens (L6), in mm.

6. The large aperture projection lens as described in claim 1, characterized in that: The large-aperture projection lens also meets the following conditions: ； Wherein, abv2 is the Abbe number of the second lens (L2), and abv7 is the Abbe number of the seventh lens (L7).

7. The large aperture projection lens as described in claim 1, characterized in that: The large-aperture projection lens also meets the following conditions: ； Wherein, OAL is the axial distance from the object side of the first lens (L1) to the image side of the eighth lens (L8), in mm.

8. The large aperture projection lens as described in claim 1, characterized in that: The large aperture projection lens also includes an optical engine located on the image side of the eighth lens (L8), which includes a galvanometer (L9), a prism (L10), and a DMD chip arranged sequentially along the optical axis.

9. The large aperture projection lens as described in claim 8, characterized in that: The large-aperture projection lens also meets the following conditions: ； Wherein, CRA is the maximum ray angle of the large aperture projection lens on the imaging surface of the DMD chip, and BFL is the on-axis distance from the image side of the eighth lens (L8) to the imaging surface of the DMD chip, in mm.

10. The large aperture projection lens as described in claim 8, characterized in that: The large-aperture projection lens also meets the following conditions: ； Wherein, FOV is the full field of view of the maximum field of view, DIST is the maximum optical distortion from the center to the edge of the field of view, and RI is the relative illumination of the large aperture projection lens on the imaging surface of the DMD chip.

Images