Large-aperture projection lens

Abstract

The invention relates to a large-aperture projection lens, which comprises a first lens, a second lens, a third lens, a fourth lens, a diaphragm, a fifth lens, a sixth lens, a seventh lens and an eighth lens which are sequentially arranged along the direction of an optical axis, and is characterized in that the first lens, the fourth lens, the fifth lens, the seventh lens and the eighth lens have positive focal power; the second lens, the third lens and the sixth lens have negative focal power, and the sixth lens and the seventh lens are doublet lenses and have positive focal power; by reasonably setting the focal length and the entrance pupil diameter of the lens, the lens has the characteristics of large aperture, small size and low cost, does not defocus under the environmental condition of large temperature difference, and is stable in working performance, high in projection quality and wide in application range.

Description

Technical Field

[0001] The invention belongs to the technical field of optical lenses, and in particular relates to a large aperture projection lens. Background Art

[0002] With the rapid development of new energy vehicles, the comfort of in-vehicle space has been significantly improved, and with it comes the gradual increase in in-vehicle entertainment programs. Among the many entertainment options, in-vehicle TVs once dominated, but due to limited space in the car and safety considerations, the screen size of in-vehicle TVs is generally small, which undoubtedly limits the viewing experience of passengers and is difficult to meet the needs of modern consumers for diversified and immersive entertainment interactions. In this context, projection equipment, as a solution that can project huge images in a small space, has gradually attracted market attention.

[0003] However, traditional projectors are often large in size and are not easy to install in the limited space of a vehicle. In addition, the in-vehicle environment places more stringent requirements on projection equipment, such as the need to adapt to high and low temperature changes and vibrations during vehicle driving. The aperture of traditional in-vehicle projection lenses is not large, and there are certain shortcomings in practical applications, mainly manifested in its limited brightness, limited focus range, and reduced image resolution. These factors limit the application of projection equipment in the in-vehicle space. For example, due to the smaller aperture, the amount of light entering is reduced, making the brightness of the projected image lower, especially in a dark environment. This phenomenon is more obvious. Therefore, given that traditional projectors have certain shortcomings in brightness, stability, and environmental adaptability, they face many challenges in practical applications, hindering the application of projection equipment in the in-vehicle space. Summary of the invention

[0004] The purpose of the present invention is to address the above problems and propose a large aperture projection lens, which has the characteristics of large aperture, small size and low cost. At the same time, it does not defocus under environmental conditions with a large temperature difference of -40℃ to 85℃, has stable working performance, high projection quality and a wide range of applications.

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

[0006] A large aperture projection lens provided by the present invention comprises a first lens, a second lens, a third lens, a fourth lens, an aperture, a fifth lens, a sixth lens, a seventh lens and an eighth lens which are sequentially arranged along the optical axis direction, wherein:

[0007] The first lens, the fourth lens, the fifth lens, the seventh lens and the eighth lens have positive power, the second lens, the third lens and the sixth lens have negative power, and the sixth lens and the seventh lens are doublet lenses and have positive power;

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

[0009]

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

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

[0012]

[0013] Wherein, 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, and the unit is mm.

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

[0015]

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

[0017] Preferably, the first lens is a biconvex lens or a convex-planar 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-planar 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, the eighth lens is a convex-planar lens or a biconvex lens, and the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens are all glass spherical lenses, the first lens and the eighth lens are all glass spherical lenses or glass aspherical lenses, and the large aperture projection lens also meets 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] Wherein, f1~f8 are the focal lengths of the first lens to the eighth lens respectively; R 11 , R 21 , R 31 , R 41 , R 51 , R 61 , R 71 , R 81 are the curvature radii of the object side surfaces of the first to eighth lenses, respectively; R 12 , R 22 , R 32 , R 42 , R 52 , R 62 , R 72 , R 82They are the curvature radii of the image side surfaces of the first to eighth lenses, respectively, and the unit is mm; “-” indicates that the direction is the negative direction.

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

[0021] 2≤th4+th6≤5

[0022] Wherein, th4 is the middle thickness of the fourth lens, and th6 is the middle thickness of the sixth lens, and the unit is mm.

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

[0024] 100≤abv2+abv7≤168

[0025] Wherein, 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] Wherein, OAL is the axial distance from the object side surface of the first lens to the image side surface of the eighth lens, in mm.

[0029] Preferably, the large aperture projection lens system further comprises an optical machine located at the image side of the eighth lens, and the optical machine comprises a galvanometer, a prism and a DMD chip which are sequentially arranged along the optical axis.

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

[0031] CRA≤2°,20≤BFL≤30

[0032] 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 axial distance from the image side surface 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] Among them, FOV is the full field of view angle 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 present invention has the following beneficial effects:

[0037] The lens uses eight lenses, and through the reasonable distribution of optical focal length, the lens structure is compact and small in size. The total length of the lens is within 62mm, which helps to reduce costs while ensuring image quality. The reasonable distribution of lenses corrects various aberrations and improves edge image quality, thereby improving image quality. The maximum aperture can reach F1.6, which enables the lens to have a higher light output capacity and allow more light to pass through, thereby providing higher brightness output while keeping the device small, so that users can enjoy clear and bright projection images even in daytime or in environments with strong light. In addition, the large aperture projection lens performs well in fast focusing and reducing exposure time, effectively reducing image blur caused by vehicle vibration and ensuring the stability of the projection image. At the same time, the reasonable setting of complementary materials ensures that the lens does not defocus under environmental conditions of -40℃~+85℃, and can work stably in high and low temperature environments on board, meeting strict use requirements. It can be adapted to a variety of DMD chips, such as 0.33”DMD chip, to provide sufficient projection brightness and size, and the projection image is clear and sharp, with high contrast, accurate color reproduction, high pixels and good imaging quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic structural diagram of a large aperture projection lens according to 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 according to Example 1 of the present invention are shown;

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

[0041] Figure 4 This is a schematic structural diagram of a large aperture projection lens according to 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 according to Example 2 of the present invention are shown;

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

[0044] Figure 7 This is a schematic structural diagram of a large aperture projection lens according to 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 according to Example 3 of the present invention are shown;

[0046] Fig. 9 This is the MTF diagram of the large aperture projection lens of Example 3 of the present invention;

[0047] Fig.10 This is a schematic structural diagram of a large aperture projection lens according to Embodiment 4 of the present invention;

[0048] Fig.11 The longitudinal spherical aberration diagram, astigmatism diagram and distortion diagram of the large aperture projection lens according to Example 4 of the present invention are shown;

[0049] Fig.12 This is the MTF diagram of the large aperture projection lens according to Example 4 of the present invention.

[0050] Explanation of the accompanying drawings: 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; CG, protective glass; Sensor, DMD chip. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work 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 those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0053] The lens of this application has a large aperture of Fno1.6. The design not only reduces the size of the projection equipment, but also significantly improves the projection effect. The large aperture projection lens allows more light to pass through, thereby providing higher brightness output while keeping the device small. This means that even in daytime or in a bright light environment, users can enjoy clear and bright projection images. In addition, the large aperture projection lens performs well in fast focusing and reducing exposure time, effectively reducing image blur caused by vehicle vibration and ensuring the stability of the projection image. At the same time, the lens can work stably in high and low temperature environments in the vehicle, meeting the stringent use requirements. Therefore, the large aperture projection lens brings new possibilities to the in-vehicle entertainment system. It can not only provide an immersive viewing experience, but also meet the passengers' demand for high-quality entertainment content without affecting the safety and comfort of the vehicle. Therefore, the large aperture projection lens of this application helps to promote the development of in-vehicle entertainment technology and bring a more diversified entertainment experience to the new energy vehicle market.

[0054] A large aperture projection lens comprises 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 and an eighth lens L8 which are sequentially arranged along an optical axis direction, 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 refractive power, the second lens L2, the third lens L3 and the sixth lens L6 have negative refractive power, and the sixth lens L6 and the seventh lens L7 are doublet lenses and have positive refractive power;

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

[0057]

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

[0059] Among them, the first lens L1 provides sufficient light height for the edge field of view, which is beneficial to reduce the optical distortion at the edge and provide a solution for small front-end aperture; the second lens L2 can quickly compress the light height and cooperate 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 the edge light, smoothes the light, and reduces the field of view aberration; the object side of the fourth lens L4 is a nearly flat surface with a curvature, and the image side is a convex surface. The light height is higher on the convex surface, providing a certain field curvature compensation for the system, making the optical system MTF highly concentrated, and connecting the front and rear lens groups, so that the light near the aperture ST has a smooth trend, which helps to reduce the sensitivity of the lens and improve the product yield and reliability; an aperture ST is provided between the fourth lens L4 and the fifth lens L5, that is, the aperture ST is located in the middle of the lens. It helps to balance the upper and lower light at the edge of the field of view, ensure the edge brightness while reducing the main light angle of the lens, so that the lens can better match the projection light system; the fifth lens L5 can be set to have a larger Abbe number, which can reduce the chromatic aberration introduced into the system; the sixth lens L6 can be set to have a smaller Abbe number, and the combination of positive and negative optical power with the seventh lens L7 can reduce the chromatic aberration of the entire system; the seventh lens L7 is also made of high Abbe number material to reduce the introduction of chromatic aberration, and form a chromatic aberration complementary and spherical aberration complementary relationship with the negative lens; the sixth lens L6 and the seventh lens L7 form a double cemented lens, which can greatly reduce the overall chromatic aberration of the system, ensure the low level of axial chromatic aberration and vertical axis chromatic aberration, and achieve simultaneous clarity of monochromatic light and mixed color light; the eighth lens L8 has a higher Abbe number and a flat surface, which helps to reduce spherical aberration and correct the incident angle of the main light.

[0060] Furthermore, f / D can be: 1.64, 1.6, 1.65. If the above conditions are met, the lens has a larger aperture, which can meet the needs of low-cost and low-light projection equipment, as well as high-light projection equipment, so that the lens has a wide range of uses and meets the needs of most projection scenes on the market; in addition, f can be: 20.95, 21.2, 20.45, in mm. If the above conditions are met and matched with a 0.33" DMD chip, the lens can have wide-angle characteristics and a wide viewing angle, and can project the required frame at a short distance; if the upper limit of the range is exceeded, the lens angle is reduced and the frame is reduced; if the lower limit of the range is exceeded, the lens angle increases, and the lens needs to be designed more complexly, and the requirements for miniaturization and low cost are not met.

[0061] In one embodiment, the large aperture projection lens further satisfies the following conditions:

[0062]

[0063] Wherein, 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, and the unit is mm.

[0064] Specifically, f1 / (f2+f3) can be: -1.05, -1.09, -0.86, -1.18, -0.97. If the above conditional formula is met, the first lens L1, the second lens L2, and the third lens L3 are a positive-negative-negative combination, and the effective focal length is limited to a reasonable range. The positive and negative combination lenses can be used to achieve a small aperture and low distortion effect, reduce the introduction of aberrations, and improve overall clarity. If the range is exceeded, the optical power is unevenly matched, and it is not easy to achieve a small head solution.

[0065] In one embodiment, the large aperture projection lens further satisfies the following conditions:

[0066]

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

[0068] Specifically, SD1 / SD8 can be: 1.3, 1.41, 1.45, 1.33, 1.36. When the above conditional formula is met, the aperture of the first lens L1 and the aperture of the eighth lens L8 are very close, so that the diameter of the head and tail of the structure can be basically the same, which is conducive to the overall miniaturization design of the projection, and also helps to reduce the exposed area of ​​the projection, improve the integration, reduce the discomfort of exposure, and improve the aesthetics of the projection equipment in the car space. If it exceeds the upper limit, the head size is too large, which reduces the aesthetics of the application; if it is below the lower limit, the head size is too small, the design is difficult, and more lenses are needed to compensate for the optical distortion caused by the small head, which is not conducive to cost reduction.

[0069] In one embodiment, the first lens L1 is a biconvex lens or a convex-planar 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-planar lens, the fifth lens L5 is a plano-convex lens or a meniscus lens, the sixth lens L6 is a plano-concave lens or a biconcave lens, the seventh lens L7 is a biconvex lens, the eighth lens L8 is a convex-planar lens or a biconvex lens, and 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 glass spherical lenses, the first lens L1 and the eighth lens L8 are all glass spherical lenses or glass aspherical lenses, and the large aperture projection lens further 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] Wherein, 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 R 12 , R 22 , R 32 , R 42 , R 52 , R 62 , R 72 , R 82 They are the curvature radii of the image-side surfaces of the first lens L1 to the eighth lens L8, all in mm; “-” indicates that the direction is the negative direction.

[0072] In one embodiment, the large aperture projection lens further satisfies the following conditions:

[0073] 2≤th4+th6≤5

[0074] Wherein, th4 is the middle thickness of the fourth lens L4, and th6 is the middle thickness of the sixth lens L6, and the unit is mm.

[0075] Specifically, th4+th6 can be: 3.12, 4.75, 2.99, 3.51, 4.96, in mm. Due to the distribution of optical power, the fourth lens L4 and the sixth lens L6 are often made of materials with a higher refractive index. Due to their own characteristics, the material with a high refractive index has a low short-wave transmittance. In order to enhance the short-wave transmittance of the lens, the thickness of the high refractive index material must be strictly controlled. When the above conditional formula is met, the overall thickness of the high refractive index material can be controlled within a reasonable range to ensure that the difference between the short-wave transmittance and the long-wave transmittance of the lens is small, avoiding the problem of color temperature deviation; if the upper limit is exceeded, the fourth lens L4 and the sixth lens L6 are too thick, which may cause the short-wave transmittance to be low, affecting the color temperature and brightness of the projected image; if the lower limit is exceeded, the lens thickness is too thin, which is not conducive to processing.

[0076] In one embodiment, the large aperture projection lens further satisfies the following conditions:

[0077] 100≤abv2+abv7≤168

[0078] Wherein, 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 and high Abbe number materials, and the material range is close to the negative dn / dt (refractive index temperature coefficient) material, which meets the above conditional formula. The sixth lens L6 and the eighth lens L8 select appropriate negative dn / dt materials to compensate for the expansion and contraction of the excessive back focus at high and low temperatures, so that the lens completes the optical athermal design, which can meet the vehicle-mounted temperature range of -40℃ to 85℃, and there is no plastic lens, and the high temperature can cover up to 105℃. Beyond the limited range, the material selection cannot meet the high and low temperature compensation requirements.

[0080] In one embodiment, the large aperture projection lens further satisfies the following conditions:

[0081] 34.5≤OAL≤62

[0082] Wherein, OAL is the axial distance from the object-side surface of the first lens L1 to the image-side surface of the eighth lens L8, and the unit is mm.

[0083] Specifically, OAL can be any value within this range, such as: 34.7, 50.5, 56.95, 57, 62, in mm. If the above condition is met, the lens has a small volume and compact space, which meets the miniaturization requirements; if it exceeds the upper limit, the miniaturization requirements are not met; if it is below the lower limit, the lens space is compressed, which is not conducive to improving clarity, and the material is more expensive, which easily leads to excessive costs.

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

[0085] Specifically, the galvanometer L9 is used to vibrate at high frequencies in different directions, so that the image expands the pixel range on the original pixel for a short time, and increases the pixels recognized by the human eye by using the visual persistence effect, thereby improving the projection resolution; the prism L10 is an equivalent flat plate, which is used to complete light aggregation for different light source combinations, such as providing appropriate reflection angles and refraction angles for each light. It is a well-known technology for those in the field and will not be described in detail here.

[0086] In one embodiment, the large aperture projection lens further satisfies the following conditions:

[0087] CRA≤2°,20≤BFL≤30

[0088] Among them, 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 axial distance from the image side surface 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, 0.5, in degrees. If the above conditional formula is met, the telecentricity of the lens is controlled within a small range to ensure that the lens is aligned with the light output direction, improve the light output efficiency from the center to the edge of the picture, and avoid uneven brightness; if it exceeds this range, the telecentricity is too large, which can easily cause low light output efficiency and affect the brightness and uniformity of the picture. In addition, FFL can be: 20.5, 22, 25.6, 27.7, 28.6, in mm. For example, BFL also includes the thickness of the galvanometer L9 and prism L10 of the large aperture projection lens. If the above conditional formula is met, the lens can match a larger back focus, sufficient prism space and light output heat dissipation space, and match more projection optical machines; if it exceeds the upper limit, the back focus is too large, which increases the difficulty and cost of lens design; if it is lower than the lower limit, the back focus is too small, which is not conducive to the arrangement of the lighting optical path and the heat dissipation of the optical machine, affecting the user experience.

[0090] In one embodiment, the large aperture projection lens further satisfies the following conditions:

[0091]

[0092] Among them, FOV is the full field of view angle 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 units of ° / %. When the above conditional formula is met, in the case of wide-angle FOV, the maximum optical distortion can be controlled within a reasonable range, and it is more appropriate for full-glass compensation distortion, so that the lens is within a reasonable range of FOV and DIST, ensuring low deformation of projection size and frame. In addition, DIST can be: -0.32%, -0.47%, -0.37%, -0.44%, -0.4%. When the above conditional formula is met, the optical distortion of the lens is within a reasonable range, at which time the projection TV distortion is less than 0.5%, and the human eye can hardly perceive the deformation of the picture, which helps to improve comfort; beyond this range, the optical distortion is too large, the deformation of the projection picture becomes larger, and it may cause discomfort in observation. RI can take any value within this range, such as: 65%, 68%, 72%, 75%, 78%. Meeting the above conditions can ensure good illumination uniformity within the imaging range and avoid dark corners due to low illumination at the edges. If the relative illumination is too low, dark corners are more likely to occur, affecting the viewing comfort.

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

[0095] Embodiment 1:

[0096] like Figure 1 As shown, in this embodiment, the large aperture projection lens comprises 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 in sequence along the optical axis, wherein the sixth lens L6 and the seventh lens L7 form a double cemented lens. The focal length of this optical system is f=20.93mm, the aperture number Fno=1.64, and the axial distance OAL from the object side of the first lens L1 to the image side of the eighth lens L8=57mm; it can be seen that this optical system can achieve a large aperture, miniaturization and a small head design.

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

[0098] Table 1

[0099] Surface number Surface type Curvature radius (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, the surface number S0 represents the object surface, the surface numbers S1, S3, S5, S7, S10, S12, S13, S15, S17, S19 to S21 represent the object 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, and the surface numbers S2, S4, S6, S8, S11, S13, S14, S16, S18, S20 to S22 represent the image side 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 bonding surface of the bonding lens group is regarded as one surface. ST represents the aperture, i.e., the surface number S9. The 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 indicates the deviation of the convergence focus of light of different wavelengths after passing through the lens. The ordinate of the longitudinal spherical aberration diagram indicates the normalized pupil coordinate (Normalized Pupil Coordinator) from the center of the pupil to the edge of the pupil, and the abscissa indicates the distance (in mm) from the imaging surface of the DMD chip to the intersection of the light and the optical axis. It can be seen from the longitudinal spherical aberration diagram that the degree of deviation of the convergence focus of light of each wavelength in this embodiment tends to be consistent, the diffuse spots or color halos in the imaging picture are effectively suppressed, and the difference between single wavelength and complex wavelength is small. Figure 2 It also includes the field curvature diagram of the optical system (ASTIGMATIC FIELD CURVES), where the S curve represents the sagittal field curvature at a wavelength of 550nm, and the T curve represents the meridian field curvature at a wavelength of 550nm. 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 a distortion diagram (DISTORTION) of the optical system. It can be seen from the diagram that 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 relationship between MTF and frequency under different fields of view is shown in the figure. The center and edge of the field of view have clear images at different frequencies, and the MTF of all fields of view is greater than 0.66 at the limit frequency of 90lp / mm. In summary, the longitudinal spherical aberration, field curvature and distortion of the optical system are well controlled, and have good imaging quality.

[0102] Embodiment 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 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, which are sequentially arranged along the light emission direction, wherein the sixth lens L6 and the seventh lens L7 form a double cemented lens. The focal length of this optical system is f=20.94mm, the aperture number Fno=1.65, and the axial distance OAL from the object side of the first lens L1 to the image side of the eighth lens L8=60mm. It can be seen that this optical system can achieve a large aperture, miniaturization and a small head design.

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

[0105] Table 2

[0106]

[0107]

[0108] like Figure 4 As shown, the surface number S0 represents the object surface, the surface numbers S1, S3, S5, S7, S10, S12, S13, S15, S17, S19 to S21 represent the object 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, and the surface numbers S2, S4, S6, S8, S11, S13, S14, S16, S18, S20 to S22 represent the image side 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 bonding surface of the bonding lens group is regarded as one surface. ST represents the aperture, i.e., the surface number S9. The 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 indicates the deviation of the convergence focus of light of different wavelengths after passing through the lens. The ordinate of the longitudinal spherical aberration diagram indicates the normalized pupil coordinate (Normalized Pupil Coordinator) from the center of the pupil to the edge of the pupil, and the abscissa indicates the distance (in mm) from the imaging surface of the DMD chip to the intersection of the light and the optical axis. It can be seen from the longitudinal spherical aberration diagram that the degree of deviation of the convergence focus of light of each wavelength in this embodiment tends to be consistent, the diffuse spots or color halos in the imaging picture are effectively suppressed, and the difference between single wavelength and complex wavelength is small. Figure 5 It also includes the field curvature diagram of the optical system (ASTIGMATIC FIELD CURVES), where the S curve represents the sagittal field curvature at a wavelength of 550nm, and the T curve represents the meridian field curvature at a wavelength of 550nm. 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 a distortion diagram (DISTORTION) of the optical system. It can be seen from the diagram that 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 relationship between MTF and frequency under different fields of view is shown in the figure. The center and edge of the field of view have clear images at different frequencies, and the MTF of all fields of view is greater than 0.64 at the limit frequency of 90lp / mm. In summary, the longitudinal spherical aberration, field curvature and distortion of the optical system are well controlled, and have good imaging quality.

[0110] Embodiment 3:

[0111] like Figure 7 As shown, in this embodiment, the large aperture projection lens comprises 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, which are arranged in sequence along the light emission direction, wherein the sixth lens L6 and the seventh lens L7 form a double cemented lens. The effective focal length of this optical system is f=20.905mm, the aperture number Fno=1.64, and the axial distance OAL from the object side of the first lens L1 to the image side of the eighth lens L8=36.6mm; it can be seen that this optical system can achieve a large aperture, miniaturization and a small head design.

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

[0113] Table 3

[0114] Surface number Surface type Curvature radius (mm) Thickness(mm) Refractive Index Abbe number S0 Spherical unlimited 3000 S1 Aspheric 17.006 4.699 1.593 68.34 S2 Aspheric 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 Aspheric 21.659 5.598 1.593 68.34 S16 Aspheric -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 surfaces, and satisfy the following aspherical surface equation:

[0116]

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

[0118] Table 4

[0119]

[0120]

[0121] like Figure 7 As shown, the surface number S0 represents the object surface, the surface numbers S1, S3, S5, S7, S10, S12, S13, S15, S17, S19 to S21 represent the object 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, and the surface numbers S2, S4, S6, S8, S11, S13, S14, S16, S18, S20 to S22 represent the image side 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 bonding surface of the bonding lens group is regarded as one surface. ST represents the aperture, i.e., the surface number S9. The 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 indicates the deviation of the convergence focus of light of different wavelengths after passing through the lens. The ordinate of the longitudinal spherical aberration diagram indicates the normalized pupil coordinate (Normalized Pupil Coordinator) from the center of the pupil to the edge of the pupil, and the abscissa indicates the distance (in mm) from the imaging surface of the DMD chip to the intersection of the light and the optical axis. It can be seen from the longitudinal spherical aberration diagram that the degree of deviation of the convergence focus of light of each wavelength in this embodiment tends to be consistent, the diffuse spots or color halos in the imaging picture are effectively suppressed, and the difference between single wavelength and complex wavelength is small. Figure 8It also includes the field curvature diagram of the optical system (ASTIGMATIC FIELD CURVES), where the S curve represents the sagittal field curvature at a wavelength of 550nm, and the T curve represents the meridian field curvature at a wavelength of 550nm. 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 a distortion diagram (DISTORTION) of the optical system. It can be seen from the diagram that 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. Fig. 9 The relationship between MTF and frequency under different fields of view is shown in the figure. The center and edge of the field of view have clear images at different frequencies, and the MTF of all fields of view is greater than 0.62 at the limit frequency of 90lp / mm. In summary, the longitudinal spherical aberration, field curvature and distortion of the optical system are well controlled, and have good imaging quality.

[0123] Embodiment 4:

[0124] like Fig.10 As shown, in the embodiment, the large aperture projection lens comprises 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, which are arranged in sequence along the light emission direction, wherein the sixth lens L6 and the seventh lens L7 form a double cemented lens. The effective focal length of this optical system is f=20.93mm, the aperture number Fno=1.64, and the axial distance OAL from the object side of the first lens L1 to the image side of the eighth lens L8=56.5mm; it can be seen that this optical system can achieve a large aperture, miniaturization and a small head design.

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

[0126] Table 5

[0127]

[0128]

[0129] like Fig.10As shown, the surface number S0 represents the object surface, the surface numbers S1, S3, S5, S7, S10, S12, S13, S15, S17, S19 to S21 represent the object 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, and the surface numbers S2, S4, S6, S8, S11, S13, S14, S16, S18, S20 to S22 represent the image side 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 bonding surface of the bonding lens group is regarded as one surface. ST represents the aperture, i.e., the surface number S9. The surface number S23 represents the imaging surface of the DMD chip. The DMD chip is a digital micromirror device (DMD).

[0130] Fig.11 The longitudinal spherical aberration diagram (LONGITUD INAL SPHERICAL ABER.) of the optical system indicates the deviation of the convergence focus of light of different wavelengths after passing through the lens. The ordinate of the longitudinal spherical aberration diagram indicates the normalized pupil coordinate (Normalized Pupil Coordinator) from the center of the pupil to the edge of the pupil, and the abscissa indicates the distance (in mm) from the imaging surface of the DMD chip to the intersection of the light and the optical axis. It can be seen from the longitudinal spherical aberration diagram that the degree of deviation of the convergence focus of light of each wavelength in this embodiment tends to be consistent, the diffuse spots or color halos in the imaging picture are effectively suppressed, and the difference between single wavelength and complex wavelength is small. Fig.11 It also includes the field curvature diagram of the optical system (ASTIGMATIC FIELD CURVES), where the S curve represents the sagittal field curvature at a wavelength of 550nm, and the T curve represents the meridian field curvature at a wavelength of 550nm. 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. Fig.11 It also includes a distortion diagram (DISTORTION) of the optical system. It can be seen from the diagram that 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. Fig.12 The relationship between MTF and frequency under different fields of view is shown in the figure. The center and edge of the field of view have clear images at different frequencies, and the MTF of all fields of view is greater than 0.6 at the limit frequency of 90lp / mm. In summary, the longitudinal spherical aberration, field curvature and distortion of the optical system are well controlled, and have good imaging quality.

[0131] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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 above-described embodiments only express the more specific and detailed embodiments described in this application, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of this application, which all belong to the protection scope of this application. Therefore, the protection scope of the patent in this application shall be based on the attached claims.

Claims

1. A large aperture projection lens, characterized in that: The large aperture projection lens comprises a first lens (L1), a second lens (L2), a third lens (L3), a fourth lens (L4), a stop (ST), a fifth lens (L5), a sixth lens (L6), a seventh lens (L7) and an eighth lens (L8) which are sequentially arranged along the optical axis direction, wherein: The first lens (L1), the fourth lens (L4), the fifth lens (L5), the seventh lens (L7), and the eighth lens (L8) have positive refractive power, the second lens (L2), the third lens (L3), and the sixth lens (L6) have negative refractive power, and the sixth lens (L6) and the seventh lens (L7) are doublet lenses and have positive refractive power; The large aperture projection lens also meets the following conditions: 20.2≤f≤21.5 Wherein, f is the focal length of the large aperture projection lens, in mm; D is the entrance pupil diameter, in mm.

2. The large aperture projection lens according to claim 1, characterized in that: The large aperture projection lens also meets the following conditions: Wherein, 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), and the unit is mm.

3. The large aperture projection lens according to claim 1, wherein: The large aperture projection lens also meets the following conditions: Wherein, SD1 is the marginal ray height on the object side of the first lens (L1), and SD8 is the marginal ray height on the image side of the eighth lens (L8).

4. The large aperture projection lens according to claim 1, wherein: The first lens (L1) is a biconvex lens or a convex-planar 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-planar 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, the eighth lens (L8) is a convex-planar lens or a biconvex lens, and 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 glass spherical lenses, the first lens (L1) and the eighth lens (L8) are all glass spherical lenses or glass aspherical lenses, and the large aperture projection lens further satisfies the following conditions: Wherein, 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 are the curvature radii of the object side surfaces of the first lens (L1) to the eighth lens (L8) in sequence; R 12 , R 22 , R 32 , R 42 , R 52 , R 62 , R 72 , R 82 They are the curvature radii of the image side surfaces of the first lens (L1) to the eighth lens (L8), all in mm; "-" indicates that the direction is the negative direction.

5. The large aperture projection lens according to claim 1, wherein: The large aperture projection lens also meets the following conditions: 2≤th4+th6≤5 Wherein, th4 is the middle thickness of the fourth lens (L4), and th6 is the middle thickness of the sixth lens (L6), and the unit is mm.

6. The large aperture projection lens according to claim 1, wherein: The large aperture projection lens also meets the following conditions: 100≤abv2+abv7≤168 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 according to claim 1, wherein: The large aperture projection lens also meets the following conditions: 34.5≤OAL≤62 Wherein, OAL is the axial distance from the object side surface of the first lens (L1) to the image side surface of the eighth lens (L8), and the unit is mm.

8. The large aperture projection lens according to claim 1, wherein: The large aperture projection lens also includes an optical machine located on the image side of the eighth lens (L8), and the optical machine includes a galvanometer (L9), a prism (L10) and a DMD chip (Sensor) which are sequentially arranged along the optical axis direction.

9. The large aperture projection lens according to claim 8, characterized in that: The large aperture projection lens also meets the following conditions: CRA≤2°,20≤BFL≤30 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 axial distance from the image side surface of the eighth lens (L8) to the imaging surface of the DMD chip (Sensor), in mm.

10. The large aperture projection lens according to claim 8, wherein: The large aperture projection lens also meets the following conditions: RI≥60% Among them, FOV is the full field of view angle 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).

Images