A projection lens
By optimizing the lens combination and optical parameters of the projection lens, and using aspherical lenses and cemented triplet lenses, the problems of complex structure and high cost of existing projection lenses have been solved, achieving low cost, easy mass production and high-quality projection effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YIBIN XGIMI OPTOELECTRONIC CO LTD
- Filing Date
- 2022-06-24
- Publication Date
- 2026-06-23
AI Technical Summary
Existing projection lenses have complex structures, a large number of lenses, are difficult to manufacture, and have high costs, making mass production difficult.
Design a projection lens that uses a small number of lens combinations, including a first lens group and a second lens group. The lens groups are composed of specific types of lenses. Optimize the lens structure and optical parameters, use aspherical lenses and cemented triplet lenses to correct aberrations and chromatic aberrations, and simplify the manufacturing process.
It achieves a small number of lenses, low cost, easy mass production, good projection effect, low distortion, and excellent MTF performance, meeting the requirements of miniaturization.
Smart Images
Figure CN117331270B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of optical lens technology, and more particularly to a projection lens. Background Technology
[0002] Projectors are increasingly being used in various fields. The core component of a projector is the projection lens. In order to achieve higher resolution, better image quality and larger screen size, current projection lenses have complex structural designs, a large number of lenses, relatively complex manufacturing processes, are not easy to mass-produce, and are expensive. Summary of the Invention
[0003] The technical problem to be solved and the technical task proposed by this invention is to improve the existing technology and provide a projection lens that solves the problems of complex structure, large number of lenses, difficult manufacturing and high cost of projection lenses in the current technology.
[0004] To solve the above technical problems, the technical solution of the present invention is as follows:
[0005] A projection lens includes a first lens group, an aperture, and a second lens group arranged sequentially from the magnification side to the reduction side. The first lens group includes a first lens with negative refractive power, a second lens with negative refractive power, and a third lens with positive refractive power, arranged sequentially from the magnification side to the reduction side. The second lens group includes a fourth lens with positive refractive power, a fifth lens with negative refractive power, a sixth lens with positive refractive power, a seventh lens with negative refractive power, an eighth lens with positive refractive power, and a ninth lens with positive refractive power, arranged sequentially from the magnification side to the reduction side. The projection lens of the present invention optimizes the lens structure, resulting in a simple structure, fewer lenses, reduced volume, lighter weight, lower cost, better mass productionability, better MTF performance, lower distortion, and better projection effect.
[0006] Furthermore, the focal length of the first lens group is -300mm≤f1≤-100mm, and the focal length of the second lens group is 10mm≤f2≤50mm.
[0007] Furthermore, the distance between the third lens and the aperture is greater than or equal to 7mm, and the distance between the fourth lens of the aperture is greater than or equal to 7mm.
[0008] Furthermore, the first lens is a meniscus aspherical lens convex towards the magnification side, and the fourth lens is a biconvex aspherical lens. The first lens helps to improve the field of view of the system and correct off-axis aberrations and system distortion, effectively ensuring the long back working distance requirement of the optical system. The fourth lens is positioned close to the aperture, which helps to reduce the outer diameter of the fourth lens, thereby reducing costs, ensuring the processing accuracy of the fourth lens, and effectively correcting full-field aberrations and improving MTF performance. In addition, the fourth lens adopts a glass aspherical design, which can improve the molding processability and component accuracy of aspherical components, resulting in good mass production performance.
[0009] Furthermore, the magnifying side surface of the third lens has the same radius of curvature as the reducing side surface of the third lens, and the magnifying side surface of the eighth lens has the same radius of curvature as the reducing side surface of the eighth lens, which helps to reduce costs and simplify the production and assembly process.
[0010] Furthermore, the second lens is a biconcave lens, and the third lens is a biconvex lens. The radius of curvature of the surface of the second lens and the radius of curvature of the surface of the third lens are matched to form mutually canceling positive and negative spherical aberrations, thereby reducing the overall spherical aberration of the optical system.
[0011] Furthermore, the fifth lens is a plano-concave lens with a flat magnifying side surface, and the fifth lens generates negative spherical aberration and sine aberration to balance the overall aberration of the lens optical system.
[0012] Furthermore, the sixth, seventh, and eighth lenses are connected to form a cemented triplet lens. The refractive indices of the sixth and eighth lenses are lower than that of the seventh lens. The sixth and eighth lenses are made of materials with a negative Dn / Dt ratio, where Dn / Dt represents the refractive index as a function of temperature. When using a laser light source, blue wavelengths are shorter and red wavelengths are longer, increasing the spectral bandwidth and causing chromatic aberration. The cemented triplet lens, with its combination of high and low refractive indices, effectively corrects system chromatic aberration. Additionally, the refractive indices of the sixth and eighth lenses decrease with increasing temperature for thermal compensation.
[0013] Furthermore, the radius of curvature of the magnifying side surface of the first lens is 10mm to 30mm, and the radius of curvature of the reducing side surface of the first lens is 5mm to 15mm; the radius of curvature of the magnifying side surface of the second lens is -70mm to -50mm, and the radius of curvature of the reducing side surface of the second lens is 15mm to 30mm; the radius of curvature of the magnifying side surface of the third lens is 50mm to 70mm, and the radius of curvature of the reducing side surface of the third lens is -70mm to -50mm; the radius of curvature of the magnifying side surface of the fourth lens is 20mm to 40mm, and the radius of curvature of the reducing side surface of the fourth lens is -50mm to -30mm; the magnifying side surface of the fifth lens is flat, and the reducing side surface of the fifth lens... The surface curvature radius of the first lens is 10mm to 30mm; the curvature radius of the magnifying side surface of the sixth lens is 100mm to 300mm, and the curvature radius of the reducing side surface of the sixth lens is -20mm to -10mm; the curvature radius of the magnifying side surface of the seventh lens is -20mm to -10mm, and the curvature radius of the reducing side surface of the seventh lens is 20mm to 40mm; the curvature radius of the magnifying side surface of the eighth lens is 20mm to 40mm, and the curvature radius of the reducing side surface of the eighth lens is -40mm to -20mm; the curvature radius of the magnifying side surface of the ninth lens is 50mm to 100mm, and the curvature radius of the reducing side surface of the ninth lens is -60mm to -30mm. The matching surface shapes of each lens meet the requirements of large aperture, simple and miniaturized structure, and low cost, effectively improving system aberrations and suppressing system distortion, thus enhancing projection quality.
[0014] Furthermore, the aperture diameter is adjustable to meet the needs of different applications. When high brightness is required, the aperture can be adjusted to the maximum. When using in a darker environment and wanting less brightness, the aperture can be appropriately reduced.
[0015] Furthermore, the effective focal length is 10mm≤EFL≤15mm, the total lens length (TTL) is ≤120mm, the total lens length-to-focal-length ratio (TTL / EFL) is ≤9.53, the ratio of the lens back focal length to the effective focal length (BFL / EFL) is ≥1.89, the relative aperture number (FNO) is ≤1.7, the telecentric angle (TA) is ≤1.492°, the system field of view is ≥63.7°, and the ratio of the lens projection distance to the screen width is 1.0≤TR≤1.2.
[0016] Compared with the prior art, the advantages of this invention are:
[0017] The projection lens described in this invention optimizes the number of lenses, the surface shape of each lens, and the optical parameters of the lens. It has a simple structure, fewer lenses, and reduced volume, meeting the needs of miniaturization development. It effectively improves the aberrations of the system and suppresses the occurrence of system distortion, thereby improving MTF performance. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the projection lens of the present invention.
[0019] In the picture:
[0020] First lens group G1, aperture 10, second lens group G2, first lens L1, second lens L2, third lens L3, fourth lens L4, fifth lens L5, sixth lens L6, seventh lens L7, eighth lens L8, ninth lens L9, galvanometer 11, DMD chip 12. Detailed Implementation
[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0022] The projection lens disclosed in this invention has a simple structure, a small number of lenses, low cost, good mass production capability, and excellent MTF performance, with low distortion, high brightness, and low color difference, thereby improving the projection effect.
[0023] like Figure 1 As shown, a projection lens includes a first lens group G1, an aperture 10, and a second lens group G2 arranged sequentially from the magnification side to the reduction side. The first lens group G1 includes a first lens L1 with negative refractive power, a second lens L2 with negative refractive power, and a third lens L3 with positive refractive power arranged sequentially from the magnification side to the reduction side. The second lens group G2 includes a fourth lens L4 with positive refractive power, a fifth lens L5 with negative refractive power, a sixth lens L6 with positive refractive power, a seventh lens L7 with negative refractive power, an eighth lens L8 with positive refractive power, and a ninth lens L9 with positive refractive power arranged sequentially from the magnification side to the reduction side. The sixth lens L6, the seventh lens L7, and the eighth lens L8 are connected to form a cemented triplet lens.
[0024] Specifically, in the first lens group G1, the first lens L1 is a meniscus aspherical resin lens convex towards the magnification side, and both the magnification and reduction surfaces of the first lens L1 are even-order aspherical surfaces. This optimizes the aspherical coefficient, effectively improving the system's field of view, correcting off-axis aberrations and system distortion, and effectively ensuring the long back working distance requirement of the optical system. The second lens L2 is a biconcave lens, and the third lens L3 is a biconvex lens. The radii of curvature of the surface of the second lens L2 and the surface of the third lens L3 are matched to form mutually canceling positive and negative spherical aberrations, reducing the overall spherical aberration of the entire projection optical system.
[0025] The aperture 10 is continuously adjustable. The aperture 10 is driven by a motor to adjust the aperture size to achieve different applications. When high brightness is required, the aperture 10 is adjusted to the maximum aperture. When the brightness is desired in a darker environment, the aperture 10 can be reduced.
[0026] The fourth lens L4 in the second lens group G2 is a biconvex aspherical glass lens. Both the magnifying and reducing surfaces of the fourth lens L4 are even-order aspherical. The refractive index of the material used for the fourth lens L4 is between 1.60 and 1.70, and the Abbe number is between 55 and 60. Using a biconvex aspherical glass improves the molding processability of the aspherical element, making it more suitable for mass production. The fourth lens L4 is positioned close to the reducing side of the aperture 10. By designing the surface curvature, aspherical parameters, and the distance between the fourth lens L4 and the aperture 10, the spherical aberration and field curvature of the system can be effectively corrected, improving the MTF performance of the projection lens. The fifth lens L5 is a plano-concave lens with a flat magnifying surface. By optimizing the curvature of the reducing surface of the fifth lens L5, it forms negative spherical aberration and sinusoidal aberration to balance the overall aberrations of the optical system. The light sources used in the projection system include laser light sources and LED light sources. In the laser light source, blue waves are shorter and red waves are longer. To correct the light... To address chromatic aberration caused by increased spectral bandwidth, a cemented triplet lens is designed. The refractive indices of the sixth and eighth lenses (L6 and L8) are lower than that of the seventh lens (L7). This combination of highly refractive indices helps eliminate chromatic aberration. Furthermore, the sixth and eighth lenses (L6 and L8) are made of materials with a negative Dn / Dt ratio, where Dn / Dt represents the refractive index variation with temperature. Dn represents the refractive index variation factor, and Dt represents the temperature variation factor. The function n = f(t) expresses the refractive index n as a function of temperature t. Differentiating this function yields Dn / Dt (the rate of change of refractive index with temperature). This means that the refractive indices of the sixth and eighth lenses (L6 and L8) decrease with increasing temperature, providing thermal compensation for the entire optical system. Additionally, the magnifying and reducing radii of curvature of the third lens (L3) and the eighth lens (L8) are the same, effectively reducing costs and simplifying the manufacturing and assembly process.
[0027] The projection system using the above-mentioned projection lens also includes a galvanometer 11, a prism, a protective glass, and a DMD chip 12 arranged sequentially on the reduced side of the ninth lens L9. During projection, light enters the projection lens after passing through the prism and the galvanometer 11 from the DMD chip 12, and finally exits from the projection lens onto the projection surface to achieve projection imaging. By setting the galvanometer 11, the projection system can simultaneously obtain the inherent resolution of the DMD chip 12 when the galvanometer 11 is stationary and the high resolution when the galvanometer 11 is working and shaking. With the 0.47-inch DMD chip 12, a 228.6cm (90-inch) image can be projected at a working distance of 2390mm. The lens has good MTF performance at the spatial limiting frequency of 93lp / mm and in the visible light range of 450nm to 655nm, with low distortion, simple structure, and good image quality. The projection lens described in this embodiment is a fixed-focus lens. When the projection distance changes, the entire projection lens moves along the optical axis to adjust the focus. Specifically, when the projection distance, i.e. the distance to the object surface projection side, changes to obtain different image sizes, the focus is adjusted by adjusting the interval between the entire projection lens and the galvanometer 11.
[0028] The aforementioned projection lens also meets the following conditions: effective focal length 10mm≤EFL≤15mm, total lens length TTL≤120mm, the total lens length can be defined as the distance from the vertex of the magnification side surface of the first lens L1 to the image plane of the DMD chip 12, the total lens length-to-focal length ratio TTL / EFL≤9.53, the ratio of the lens back focal length to the effective focal length BFL / EFL≥1.89, the relative aperture number FNO≤1.7, the telecentric angle TA≤1.492°, the system field of view ≥63.7°, and the ratio of lens projection distance to screen width 1.0≤TR≤1.2. This embodiment provides a fixed-focus projection lens with an aperture number of F1.7 and distortion of less than 0.5%, which effectively improves the chromatic aberration of the system and suppresses the occurrence of system distortion. It also has a simple and compact structure, fewer lenses, and a small volume, meeting the needs of miniaturization development. It has a large aperture, low distortion, low cost, and can ensure a high performance MTF value at high temperatures.
[0029] In this embodiment, the focal length of the first lens group G1 of the projection lens is -300mm≤f1≤-100mm, and the focal length of the second lens group G2 is 10mm≤f2≤50mm. Specifically, the radius of curvature of the magnifying side surface of the first lens L1 is 10mm~30mm, and the radius of curvature of the reducing side surface of the first lens L1 is 5mm~15mm; the radius of curvature of the magnifying side surface of the second lens L2 is -70mm~-50mm, and the radius of curvature of the reducing side surface of the second lens L2 is 15mm~30mm; the radius of curvature of the magnifying side surface of the third lens L3 is 50mm~70mm, and the radius of curvature of the reducing side surface of the third lens L3 is -70mm~-50mm; the distance between the third lens L3 and the aperture 10 is greater than or equal to 7mm, and the distance between the aperture 10 and the fourth lens L4 is greater than or equal to 7mm, ensuring that the aperture 10 has sufficient space for aperture size adjustment; the radius of curvature of the magnifying side surface of the fourth lens L4 is... The radius of curvature of the surface of the fourth lens L4 is 20mm to 40mm, and the radius of curvature of the reducing side surface is -50mm to -30mm; the radius of curvature of the surface of the fifth lens L5 is flat on the magnifying side, and the radius of curvature of the surface of the reducing side surface is 10mm to 30mm; the radius of curvature of the surface of the sixth lens L6 is 100mm to 300mm, and the radius of curvature of the surface of the reducing side surface is -20mm to -10mm; the radius of curvature of the surface of the seventh lens L7 is -20mm to -10mm, and the radius of curvature of the surface of the reducing side surface is 20mm to 40mm; the radius of curvature of the surface of the eighth lens L8 is 20mm to 40mm, and the radius of curvature of the surface of the reducing side surface is -40mm to -20mm; the radius of curvature of the surface of the ninth lens L9 is 50mm to 100mm, and the radius of curvature of the surface of the reducing side surface is -60mm to -30mm.
[0030] The specific technical parameters of a projection system are shown in Table 1.
[0031] Table 1
[0032]
[0033]
[0034] Among them, the first lens L1 and the fourth lens L4 are aspherical lenses, and the remaining lenses are spherical lenses. The aspherical polynomial formula is:
[0035]
[0036] In the formula, z represents the distance sag of the aspherical surface from the fixed point of the aspherical surface at a height r along the optical axis, c is the curvature corresponding to the radius, r is the radial height of the lens, k is the conic conic coefficient, and α1 to α8 are the aspherical coefficients corresponding to the second to sixteenth orders, as shown in Table 2.
[0037] Table 2
[0038]
[0039]
[0040] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A projection lens, characterized in that, The system comprises a first lens group, an aperture, and a second lens group arranged sequentially from the magnifying side to the reducing side. The first lens group consists of a first lens with negative diopter, a second lens with negative diopter, and a third lens with positive diopter arranged sequentially from the magnifying side to the reducing side. The second lens group consists of a fourth lens with positive diopter, a fifth lens with negative diopter, a sixth lens with positive diopter, a seventh lens with negative diopter, an eighth lens with positive diopter, and a ninth lens with positive diopter arranged sequentially from the magnifying side to the reducing side. Effective focal length 10mm≤EFL≤15mm, total lens telephoto ratio TTL / EFL≤9.
53.
2. The projection lens according to claim 1, characterized in that, The focal length of the first lens group is -300mm≤f1≤-100mm, and the focal length of the second lens group is 10mm≤f2≤50mm.
3. The projection lens according to claim 1, characterized in that, The distance between the third lens and the aperture is greater than or equal to 7mm, and the distance between the fourth lens and the aperture is greater than or equal to 7mm.
4. The projection lens according to claim 1, characterized in that, The first lens is a meniscus aspherical lens convex towards the magnification side, and the fourth lens is a biconvex aspherical lens.
5. The projection lens according to claim 1, characterized in that, The magnifying side surface of the third lens has the same radius of curvature as the reducing side surface of the third lens, and the magnifying side surface of the eighth lens has the same radius of curvature as the reducing side surface of the eighth lens.
6. The projection lens according to claim 1, characterized in that, The second lens is a biconcave lens, and the third lens is a biconvex lens. The radius of curvature of the surface of the second lens and the radius of curvature of the surface of the third lens are matched to form mutually canceling positive and negative spherical aberrations.
7. The projection lens according to claim 1, characterized in that, The fifth lens is a plano-concave lens with a flat magnifying side surface. The fifth lens generates negative spherical aberration and sine aberration to balance the overall aberration.
8. The projection lens according to claim 1, characterized in that, The sixth, seventh, and eighth lenses are connected to form a cemented triplet lens. The refractive indices of the sixth and eighth lenses are lower than those of the seventh lens. The sixth and eighth lenses are made of a material with a negative Dn / Dt ratio, where Dn / Dt represents the trend of refractive index change with temperature.
9. The projection lens according to any one of claims 1 to 8, characterized in that, The radius of curvature of the magnifying side surface of the first lens is 10mm~30mm, and the radius of curvature of the reducing side surface of the first lens is 5mm~15mm; the radius of curvature of the magnifying side surface of the second lens is -70mm~-50mm, and the radius of curvature of the reducing side surface of the second lens is 15mm~30mm; the radius of curvature of the magnifying side surface of the third lens is 50mm~70mm, and the radius of curvature of the reducing side surface of the third lens is -70mm~-50mm; the radius of curvature of the magnifying side surface of the fourth lens is 20mm~40mm, and the radius of curvature of the reducing side surface of the fourth lens is -50mm~-30mm. The magnifying side surface of the fifth lens is flat, and the radius of curvature of the reducing side surface of the fifth lens is 10mm~30mm; the radius of curvature of the magnifying side surface of the sixth lens is 100mm~300mm, and the radius of curvature of the reducing side surface of the sixth lens is -20mm~-10mm; the radius of curvature of the magnifying side surface of the seventh lens is -20mm~-10mm, and the radius of curvature of the reducing side surface of the seventh lens is 20mm~40mm; the radius of curvature of the magnifying side surface of the eighth lens is 20mm~40mm, and the radius of curvature of the reducing side surface of the eighth lens is -40mm~-20mm. The radius of curvature of the surface on the magnifying side of the ninth lens is 50mm~100mm, and the radius of curvature of the surface on the reducing side of the ninth lens is -60mm~-30mm.
10. The projection lens according to any one of claims 1 to 8, characterized in that, The aperture diameter is adjustable.
11. The projection lens according to any one of claims 1 to 8, characterized in that, The total lens length (TTL) is ≤120mm, the ratio of lens back focal length to effective focal length (BFL / EFL) is ≥1.89, the relative aperture number (FNO) is ≤1.7, the telecentric angle (TA) is ≤1.492°, the system field of view is ≥63.7°, and the ratio of lens projection distance to screen width is 1.0 ≤ TR ≤1.2.