Projection lens

Abstract

The invention relates to the technical field of projection optical devices, in particular to a projection lens which adopts a framework with two lens groups and six lenses. The projection lens is simple and compact in structure, small in number of lenses, small in occupied space, light in weight, capable of effectively improving chromatic aberration of a system and inhibiting system distortion, capable of achieving long back focus, large aperture number, large image plane and telecentric image space and suitable for improving the brightness of an LCD projector.

Description

Technical Field

[0001] The present invention relates to the technical field of projection optical devices, and in particular to a projection lens. Background Art

[0002] The projection lens is an important core component of the projector, and it affects the quality of the projected image. LCD projection display technology is a mainstream development direction. The LCD panel traditionally used in LCD projection display technology is a small-sized display chip, and the projection lens that matches it is small in size and cannot be applied to large-sized LCD panels. Large-sized LCD panels usually require a Fresnel lens as a field lens to correct light deflection, but this results in poor projection image quality, low brightness, large color difference, and large distortion, which affects the viewing experience. Summary of the invention

[0003] The technical problem to be solved and the technical task proposed by the present invention are to improve the existing technology and provide a projection lens to solve the problem that the projection lens frame structure adapted to large-size LCD panels in the current technology is poor, resulting in poor projection image quality, low brightness, large color difference and large distortion.

[0004] In order to solve the above technical problems, the technical solution of the present invention is:

[0005] A projection lens comprises a front lens group, a diaphragm and a rear lens group arranged from the magnification side to the reduction side, the front lens group comprises a lens 1 and a lens 2 arranged from the magnification side to the reduction side, the lens 1 is a meniscus lens, the refractive power of the lens 2 is positive, and the rear lens group comprises a lens 3 with a negative refractive power, a lens 4 with a positive refractive power, a lens 5 with a positive refractive power and a lens 6 with a positive refractive power arranged from the magnification side to the reduction side. The projection lens of the present invention has a simple and compact structure, a small number of lenses, adopts a two-lens group, six-lens structure, occupies a small space, is light in weight, can effectively improve the chromatic aberration of the system and suppress the occurrence of system distortion, achieve high brightness, low chromatic aberration, low distortion, improve the quality of the projection picture, and has low implementation cost.

[0006] Further, the lens 1 is a meniscus lens convex toward the reduction side, and the refractive power of the lens 1 is positive or negative;

[0007] Alternatively, the refractive power of the lens 1 is negative, and the surface of the lens 1 near the magnification side is a curved surface with the middle part concave toward the reduction side and the edge curved toward the reduction side. The front lens group formed by the combination of the lens 1 and the lens 2 is a focusing group to meet the projection imaging requirements.

[0008] Furthermore, the lens three and the lens four are connected to form a double cemented lens, the refractive index of the lens three is greater than the refractive index of the lens four, and the Abbe number of the lens three is smaller than the Abbe number of the lens four, which effectively corrects the system chromatic aberration and ensures that the entire optical system has a smaller chromatic aberration.

[0009] Furthermore, the lens three is a biconcave lens, and the lens four is a biconvex lens, which has a simple structure and is easy to implement.

[0010] Furthermore, there is at least one aspherical lens in the front lens group, and at least one aspherical lens with positive diopter in the rear lens group. The aspherical surface is used to correct distortion, astigmatism and sine difference, and the multi-aspherical structure is used to simplify the number of lens lenses, simplify the lens structure, and improve the optical performance parameters. When the aspherical lens in the front lens group and the aspherical lens in the rear lens group are matched with positive and negative diopter, the performance impact of the lens due to temperature rise can be reduced.

[0011] Furthermore, lens one and lens two are aspherical lenses. By reasonably optimizing the aspherical coefficient, lens one effectively corrects the system distortion and off-axis aberration, lens two effectively corrects the system astigmatism and coma, lens five and lens six are aspherical lenses, lens six is ​​closest to the reduction side and has positive refractive power, and lens six replaces the traditional Fresnel lens to achieve light deflection correction and improve optical performance.

[0012] Furthermore, both side surfaces of the lens 1 and both side surfaces of the lens 2 are even-order aspheric surfaces, and the astigmatism and coma of the system can be effectively corrected by reasonably optimizing the aspheric coefficients.

[0013] Furthermore, at least one of the surface of lens five on the magnification side, the surface of lens five on the reduction side, the surface of lens six on the magnification side and the surface of lens six on the reduction side is an even-order aspheric surface, and the system astigmatism and coma are effectively corrected by reasonably optimizing the aspheric coefficient.

[0014] Furthermore, the lens five is a biconvex lens;

[0015] The lens six is ​​a meniscus lens convex toward the magnifying side; or, the middle parts of the two side surfaces of the lens six are convex toward the magnifying side, and the edges of the two side surfaces of the lens six are curved toward the magnifying side.

[0016] Furthermore, the effective focal length is 60mm≤EFL≤80mm, the relative aperture number is 1.7≤FNO≤3.0, the projection ratio is 1.1≤TR≤1.3, the ratio of the lens back focal length to the effective focal length is 0.838≤BFL / EFL, the telecentric angle is TA≤3.0°, the total lens length TTL≤200mm, the field of view angle is ≥56.1°, and the ratio of the imaging circle diameter to the total lens length is 0.2≤D / TTL≤0.5. The projection lens of the present invention realizes clear imaging over a large range. When the focal length of the lens remains unchanged, the larger the aperture diameter, the larger the light aperture, and the more light can be received, thereby greatly improving the projection brightness.

[0017] Furthermore, the entire projection lens or part of the lenses in the projection lens can be tilted and adjusted relative to the optical axis. In a side projection scene, the entire projection lens or part of the lenses in the projection lens can be tilted and adjusted, which effectively improves the out-of-focus condition during side projection and allows the projection image to achieve a better resolution effect.

[0018] Compared with the prior art, the present invention has the advantages of:

[0019] The projection lens of the present invention has a simple and compact structure, a small number of lenses, a small space occupation, and a light weight. It can effectively improve the chromatic aberration of the system and suppress the occurrence of system distortion, achieve a long back focus, a large aperture number, a large image surface, and image telecentricity, and is suitable for improving the brightness of LCD projectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of a projection lens of the present invention;

[0021] Figure 2 is a schematic structural diagram of a projection lens according to a second embodiment of the present invention;

[0022] Figure 3 It is a structural schematic diagram of a projection lens according to a third embodiment of the present invention;.

[0023] In the figure:

[0024] Lens one 1, lens two 2, lens three 3, lens four 4, lens five 5, lens six 6, aperture 10, galvanometer 11, prism 12, protective glass 13, light valve 14. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] A projection lens disclosed in an embodiment of the present invention has high brightness, low chromatic aberration, low distortion, and a large aperture, which effectively improves the imaging quality, has a simple structure, a small number of lenses, and low cost.

[0027] Embodiment 1

[0028] like Figure 1 As shown, a projection lens mainly includes a front lens group, an aperture 10 and a rear lens group arranged from the magnification side to the reduction side, wherein the front lens group includes a lens 1 and a lens 2 2 arranged from the magnification side to the reduction side, the lens 1 1 is a meniscus lens, the refractive power of the lens 2 2 is positive, and the rear lens group includes a lens 3 3 with a negative refractive power, a lens 4 4 with a positive refractive power, a lens 5 5 with a positive refractive power and a lens 6 6 with a positive refractive power arranged from the magnification side to the reduction side.

[0029] There is at least one aspherical lens in the front lens group, and at least one aspherical lens with positive refractive power in the rear lens group. Aspherical surfaces are used to correct distortion, astigmatism and sine difference, and a multi-aspherical structure is used to simplify the number of lens elements, simplify the lens structure, and improve optical performance parameters. In this embodiment, the front lens group is a focusing group, and both lens 1 and lens 2 in the front lens group are aspherical lenses. Specifically, lens 1 is a meniscus lens convex to the reduction side, and the refractive power of lens 1 is negative. The surface of lens 1 on the magnification side and the surface of lens 1 on the reduction side are both even-order aspherical surfaces. By reasonably optimizing the aspherical coefficient, the system astigmatism and coma are effectively corrected. The radius of curvature of the surface of lens 1 on the magnification side is -150mm~-40mm, and the radius of curvature of the surface of lens 1 on the reduction side is -150mm~-40mm; lens 22 is a meniscus lens convex to the magnification side, and the surface of lens 22 on the magnification side and the surface of lens 22 on the reduction side are both even-order aspherical surfaces. By reasonably optimizing the aspherical coefficient, the system astigmatism and coma are effectively corrected. The radius of curvature of the surface of lens 22 on the magnification side is 10mm~50mm, and the radius of curvature of the surface of lens 22 on the reduction side is 10mm~50mm;

[0030] Furthermore, the lens five 5 and the lens six 6 in the rear lens group of the present embodiment are both aspherical lenses, which utilize the aspherical surface to correct distortion, astigmatism and sine difference, and adopt a multi-aspherical architecture to simplify the number of lens elements, simplify the lens structure, and improve the optical performance parameters. Specifically, the lens three 3 in the rear lens group is a double concave lens, and the radius of curvature of the surface of the lens three 3 on the magnification side is -50mm~-10mm, and the radius of curvature of the surface of the lens three 3 on the reduction side is 50mm~600mm; the lens four 4 is a double convex lens, and the radius of curvature of the surface of the lens four 4 on the magnification side is 50mm~600mm, and the radius of curvature of the surface of the lens four 4 on the reduction side is -80mm~-20mm. The lens three 3 and the lens four 4 are connected to form a double cemented lens, the refractive index of the lens three 3 is greater than the refractive index of the lens four 4, and the Abbe number of the lens three 3 is less than the Abbe number of the lens four 4, forming a cemented structure composed of a combination of high and low refractive indices, which effectively corrects the system chromatic aberration and ensures that the entire optical system has a small chromatic aberration. The lens five 5 is a double convex lens, the curvature radius of the surface of the lens five 5 on the magnification side is 50mm~150mm, and the curvature radius of the surface of the lens five 5 on the reduction side is -300mm~-50mm; the lens six 6 is an aspheric lens with positive refractive power, the middle of the two side surfaces of the lens six 6 convex to the magnification side, the edges of the two side surfaces of the lens six 6 are curved toward the magnification side, the curvature radius of the surface of the lens six 6 on the magnification side is 20mm~70mm, and the curvature radius of the surface of the lens six 6 on the reduction side is less than 500mm. At least one of the surface of lens 55 on the magnification side, the surface of lens 55 on the reduction side, the surface of lens 66 on the magnification side and the surface of lens 66 on the reduction side is an even-order aspheric surface, and the astigmatism and coma of the system are effectively corrected by reasonably optimizing the aspheric coefficient. Lens 1 is an aspheric lens with negative refractive power, and lens 55 and lens 66 are aspheric lenses with positive refractive power. When positive and negative refractive powers are matched, the performance impact of the lens due to temperature rise can be reduced.

[0031] In the projection lens described in this embodiment, the aperture 10 is arranged near the focal position of the rear lens group, the effective focal length is 60mm≤EFL≤80mm, the relative aperture number is 1.7≤FNO≤3.0, the ratio of the lens projection distance to the screen width is 1.1≤TR≤1.3, the total length focal length ratio of the lens is 2.86≤TTL / EFL, the ratio of the lens back focal length to the effective focal length is 0.838≤BFL / EFL, the telecentric angle is TA≤3.0°, the total length of the lens is TTL≤200mm, the field of view angle is ≥56.1°, and the ratio of the imaging circle diameter to the total length of the lens is 0.2≤D / TTL≤0.5. The above-mentioned projection lens can effectively improve the chromatic aberration of the system and suppress the occurrence of system distortion, the number of optical lenses used is small, the structure is simplified, the field of view angle is large, the aperture diameter is large, the distortion is low, the cost is low, and the high performance MTF value can be ensured at high temperature.

[0032] The projection system using the above-mentioned projection lens also includes a galvanometer 11, a prism 12, a protective glass 13 and a light valve 14 which are sequentially arranged on the reduction side of the lens 66 along the direction from the magnification side to the reduction side. The light valve 14 is specifically an LCD panel. During projection, light enters the projection lens from the reduction end side from the light valve 14 through the prism 12, and finally leaves the projection lens and is emitted to the projection surface to achieve projection imaging. The physical resolution of the LCD panel is 17lp / mm. By setting a shaking galvanometer 11, the projection lens can simultaneously obtain the resolution inherent in the size of the LCD panel when the galvanometer 11 is stationary and the 4K resolution when the galvanometer 11 is working and shaking. Under the condition of achieving efficient light transmission, the distance of the back focus telecentricity is increased, and the brightness of the system is improved by increasing the light source by combining light through the prism 12. The prism 12 can meet the light combination of two or more LCD panels, solving the problem of low brightness of LCD projection display. With a 2.6-inch LCD panel, a 228.6cm (90-inch) screen can be projected at a working distance of 2390mm. The projection lens has excellent MTF performance at the spatial limit frequency of 17lp / mm and in the visible light range of 450nm~630nm, with small distortion, simple structure, good imaging quality, and a large imaging clarity range. It ensures that the output image is biased upward during projection, so that the output light beam is higher than the projection lens position, and the projection image will not be blocked by the projection lens. The projection system also includes a drive motor 1 for adjusting the position of the projection lens to meet the needs of different image sizes. The projection system also includes a drive motor 2, which is connected to the galvanometer 11 to drive the galvanometer 11 to work in a dithering manner. It supports a unidirectional longitudinal offset of -50% to offset+50% adjustment of a 2.6-inch LCD panel. When the optical axis of the projection lens is translated, the projected image will move in the same direction. During the movement of the projection lens, the overall image remains clear and stable except for the movement of the image.

[0033] In this embodiment, lens six 6 is used to replace the Fresnel lens to correct the deflection of light, so that the main light incident on the LCD panel is close to parallel light. On the basis of this embodiment, the Fresnel lens can also be used to correct the deflection of large-angle light. A Fresnel lens is set on the reduction side of lens six 6. The Fresnel lens is located between lens six 6 and the LCD panel to achieve nearly parallel light incident on the LCD panel, with a maximum TA<3°. When the Fresnel lens is used, the spatial distance from the Fresnel lens to the LCD panel is 0.1mm≤T≤25mm, and the tooth surface of the Fresnel lens is close to the LCD panel.

[0034] Specific parameters of a projection system are shown in Table 1.

[0035] Table 1

[0036]

[0037] Among them, lens 1, lens 2, lens 5, and lens 6 are aspherical lenses, and the remaining lenses are spherical lenses. The aspherical polynomial formula is:

[0038]

[0039] In the formula, z represents the distance vector height of the aspheric surface from the fixed point of the aspheric surface when the aspheric surface is at a height r along the optical axis, the parameter c is the curvature corresponding to the radius, r is the radial height of the lens, k is the conic constant coefficient (ConicConstant), and α1~α8 are the aspheric coefficients corresponding to the 20th to 16th orders, as shown in Table 2.

[0040] When the k coefficient is less than -1, the surface curve of the lens is a hyperbola;

[0041] When the k coefficient is equal to -1, the surface curve of the lens is a parabola;

[0042] When the k coefficient is between -1 and 0, the surface curve of the lens is an ellipse;

[0043] When the k coefficient is equal to 0, the surface curve of the lens is circular;

[0044] When the k coefficient is greater than 0, the surface curve of the lens is an oblate circle.

[0045] Table 2

[0046]

[0047] This embodiment provides a fixed-focus projection lens with an aperture number of F2.0, a distortion of less than 2.0%, and a ratio of back focal length to effective focal length of 0.838≤BFL / EFL. This lens has a precise structure and is low-cost. The projection lens forms a 90-inch diagonal screen at a position of 2390mm. Based on the principle of optical imaging, the curvature radius, material, thickness, air spacing, etc. of each lens of the projection lens are designed, and multiple aspherical lenses are set, with small aberration, high resolution, simple structure, and easy mass production.

[0048] Furthermore, the side projection angle supported by LCD projectors is significantly smaller than that of DLP projectors. This is mainly because the LCD panel used in LCD projectors is more than 10 times larger than the DMD chip used in DLP projectors. When the projection screen size is the same, the magnification of the LCD projector in the vertical axis is approximately one-tenth of the magnification of the DLP projector in the vertical axis, and the angular magnification is the reciprocal of the vertical axis magnification. When the NA at the LCD panel end and the DMD chip end are the same, the NA angle at the projection screen end is about ten times different, that is, the NA angle of the LCD projector is larger and the depth of field is smaller, which severely limits the side projection angle. Defocus problems are prone to occur during side projection, and the resolution is reduced, affecting the quality of the projected image.

[0049] In order to solve the above problems, the entire projection lens or part of the lens in the projection lens can be tilted and adjusted relative to the optical axis. When side projection is performed, the entire projection lens or part of the lens in the projection lens is tilted to optimize the projection effect. Based on Sham's law, when the extended surfaces of the three planes, the subject plane, the image plane, and the lens plane, intersect in a straight line, a comprehensive and clear image can be obtained, and a great depth of field can be obtained. For the projection system, the LCD panel corresponds to the image plane, the screen corresponds to the subject plane, and the projection lens corresponds to the lens plane, that is, when the extended surfaces of the image plane of the LCD panel, the screen and the projection lens plane intersect in a straight line, a clear projection picture can be obtained. Therefore, when side projection is performed, the projection lens or part of the lens in the projection lens is tilted and adjusted according to the inclination angle between the projection lens plane and the screen to meet the conditions of Sham's law, thereby solving the problem of reduced resolution due to defocus when the side projection angle is large, and effectively improving the quality of the projection picture.

[0050] Specifically, the rotation point position of the entire projection lens when tilting and adjusting is on the optical axis. The rotation point position can be set at any reasonable position, for example, it can be set at the vertex where the magnifying side surface of the lens 1 intersects with the optical axis, the center where the aperture intersects with the optical axis, the vertex where the reducing side surface of the lens 6 intersects with the optical axis, etc. As long as the conditions of Sham's law can be met, the out-of-focus problem can be solved during side projection, the resolution of the projected picture can be improved, the image quality loss can be avoided, the projection picture effect can be improved, and the viewing experience can be guaranteed.

[0051] Part of the lenses in the projection lens are tiltable relative to the optical axis, which specifically means that a single lens or a single lens group in the projection lens is tiltable relative to the optical axis, and the plane of the entire projection lens can also be adjusted to meet Scham's law. Specifically, lens one can be tiltable, lens six can be tiltable, or the rear lens group can be tiltable as a whole. When part of the lenses in the projection lens are tiltable relative to the optical axis, the rotation point is also on the optical axis.

[0052] Embodiment 2

[0053] like Figure 2 As shown, the projection lens also adopts a two-lens group, six-lens structure, the front lens group includes a lens 1 with positive refractive power and a lens 2 with positive refractive power arranged from the magnification side to the reduction side, and the rear lens group includes a lens 3 with negative refractive power 3, a lens 4 with positive refractive power 4, a lens 5 with positive refractive power and a lens 6 with positive refractive power arranged from the magnification side to the reduction side.

[0054] Specifically, the lens 1 is a positive meniscus lens convex to the reduction side, the lens 2 is a positive meniscus lens convex to the magnification side, the lens 1 and the lens 2 are both aspheric lenses, the surface of the lens 1 on the magnification side and the surface on the reduction side are both even-order aspheric surfaces, and the system astigmatism and coma are effectively corrected by reasonably optimizing the aspheric coefficient. The lens 3 and the lens 4 are independent single lenses, specifically, the lens 3 is a negative lens with both surfaces convex to the reduction side, the lens 4 is a positive meniscus lens convex to the reduction side, the lens 5 is a double convex lens, the lens 6 is a positive meniscus lens convex to the magnification side, the lens 5 and the lens 6 are aspheric lenses, and at least one of the surface of the lens 5 on the magnification side, the surface of the lens 5 on the reduction side, the surface of the lens 6 on the magnification side, and the surface of the lens 6 on the reduction side is an even-order aspheric surface.

[0055] Specific parameters of a projection system are shown in Table 3.

[0056] Table 3

[0057]

[0058] Among them, lens 1, lens 2, lens 5, and lens 6 are aspherical lenses, and the remaining lenses are spherical lenses. The aspherical polynomial formula is:

[0059]

[0060] In the formula, z represents the distance vector height of the aspheric surface from the fixed point of the aspheric surface when the aspheric surface is at a height r along the optical axis, the parameter c is the curvature corresponding to the radius, r is the radial height of the lens, k is the conic constant coefficient (ConicConstant), and α1~α8 are the aspheric coefficients corresponding to the 20th to 16th orders, as shown in Table 4.

[0061] When the k coefficient is less than -1, the surface curve of the lens is a hyperbola;

[0062] When the k coefficient is equal to -1, the surface curve of the lens is a parabola;

[0063] When the k coefficient is between -1 and 0, the surface curve of the lens is an ellipse;

[0064] When the k coefficient is equal to 0, the surface curve of the lens is circular;

[0065] When the k coefficient is greater than 0, the surface curve of the lens is an oblate circle.

[0066] Table 4

[0067] k <![CDATA[α2]]> <![CDATA[α3]]> <![CDATA[α4]]> <![CDATA[α5]]> <![CDATA[α6]]> <![CDATA[α7]]> <![CDATA[α8]]> S1 0.0E+00 2.6E-05 -5.3E-08 9.6E-11 -1.2E-13 1.0E-16 -4.7E-20 9.7E-24 S2 0.0E+00 2.0E-05 -4.0E-08 7.8E-11 -1.0E-13 9.3E-17 -4.8E-20 1.1E-23 S3 0.0E+00 -1.1E-05 -1.6E-09 3.3E-11 -1.3E-13 2.2E-16 -1.7E-19 0.0E+00 S4 0.0E+00 -2.1E-05 4.9E-08 -1.6E-10 3.4E-13 -1.8E-16 0.0E+00 0.0E+00 S10 0.0E+00 -7.5E-07 2.4E-09 -6.2E-12 9.4E-15 -7.5E-18 3.1E-21 -5.3E-25 S11 0.0E+00 -1.5E-06 3.8E-09 -5.2E-12 4.9E-15 -2.1E-18 2.9E-22 3.8E-26 S12 0.0E+00 -4.2E-06 2.8E-09 -3.1E-12 1.6E-15 9.7E-20 -3.6E-22 8.4E-26 S13 0.0E+00 -3.0E-06 1.9E-09 -2.0E-12 4.5E-16 1.1E-18 -8.2E-22 1.7E-25

[0068] This embodiment provides a projection lens with an aperture number of F1.999, an effective focal length EFL of 70 mm, a lens back focal length BFL of 58.7, and a system field of view FOV of 56.56.

[0069] Embodiment 3

[0070] like Figure 3 As shown, the projection lens also adopts a two-lens group, six-lens structure, the front lens group includes a negative refractive power lens 1 and a positive refractive power lens 2 arranged from the magnification side to the reduction side, and the rear lens group includes a negative refractive power lens 3, a positive refractive power lens 4, a positive refractive power lens 5 and a positive refractive power lens 6 arranged from the magnification side to the reduction side.

[0071] Further, the refractive power of the lens 1 is negative, the surface of the lens 1 on the magnification side is a curved surface with the middle part concave toward the reduction side and the edge curved toward the reduction side, which can also be expressed as: the cross section of the surface of the lens 1 on the magnification side is wavy, the surface of the lens 1 on the magnification side has an inflection point change from the middle to the edge convex toward the magnification side, the surface of the lens 1 on the reduction side is a curved surface convex toward the magnification side, and the diameter of the lens 1 is less than 63mm. The lens 22 is a positive meniscus lens convex toward the magnification side, the lens 1 and the lens 22 are both aspherical lenses, and the two side surfaces of the lens 1 and the two side surfaces of the lens 22 are even-order aspherical surfaces.

[0072] The lens three 3 is a double concave lens, the lens four 4 is a double convex lens, the lens three 3 and the lens four 4 are connected to form a double cemented lens, the lens three 3 is made of a material with a high refractive index and a low Abbe number, and the lens four 4 is made of a material with a low refractive index and a high Abbe number, which can effectively achromatize. The lens five 5 is a double convex lens, the lens six 6 is a meniscus lens convex to the magnification side with a positive refractive power, the lens five 5 and the lens six 6 are still aspherical lenses, and at least one of the surface of the lens five 5 on the magnification side, the surface of the lens five 5 on the reduction side, the surface of the lens six 6 on the magnification side, and the surface of the lens six 6 on the reduction side is an even aspherical surface.

[0073] Specific parameters of a projection system are shown in Table 5.

[0074] Table 5

[0075]

[0076]

[0077] Among them, lens 1, lens 2, lens 5, and lens 6 are aspherical lenses, and the remaining lenses are spherical lenses. The aspherical polynomial formula is:

[0078]

[0079] In the formula, z represents the distance vector height of the aspheric surface from the fixed point of the aspheric surface when the aspheric surface is at a height r along the optical axis, the parameter c is the curvature corresponding to the radius, r is the radial height of the lens, k is the conic constant coefficient (ConicConstant), and α1~α8 are the aspheric coefficients corresponding to the 20th to 16th orders, as shown in Table 6.

[0080] When the k coefficient is less than -1, the surface curve of the lens is a hyperbola;

[0081] When the k coefficient is equal to -1, the surface curve of the lens is a parabola;

[0082] When the k coefficient is between -1 and 0, the surface curve of the lens is an ellipse;

[0083] When the k coefficient is equal to 0, the surface curve of the lens is circular;

[0084] When the k coefficient is greater than 0, the surface curve of the lens is an oblate circle.

[0085] Table 6

[0086] k <![CDATA[α2]]> <![CDATA[α3]]> <![CDATA[α4]]> <![CDATA[α5]]> <![CDATA[α6]]> <![CDATA[α7]]> <![CDATA[α8 <!-- 9 -->]]> S1 -7.2E+01 1.6E-05 -2.3E-08 3.3E-11 -3.0E-14 1.7E-17 -4.7E-21 3.6E-25 S2 -9.9E+01 1.5E-05 -2.1E-08 3.3E-11 -2.9E-14 1.8E-17 -5.7E-21 8.1E-25 S3 -1.6E+00 3.2E-06 -5.0E-09 1.6E-10 -8.7E-13 2.6E-15 -3.8E-18 2.4E-21 S4 -2.0E-01 -4.9E-06 -3.4E-08 6.6E-10 -5.5E-12 2.5E-14 -5.7E-17 5.4E-20 S10 0.0E+00 -3.4E-06 5.2E-09 -8.3E-12 9.9E-15 -7.5E-18 3.6E-21 -7.5E-25 S11 0.0E+00 -1.0E-05 1.4E-08 -1.8E-11 1.9E-14 -1.4E-17 5.6E-21 -7.9E-25 S12 -7.4E-01 -7.9E-06 5.1E-09 -5.8E-12 5.0E-15 -2.6E-18 7.5E-22 -8.9E-26 S13 -9.9E+01 3.9E-07 -3.2E-09 2.5E-12 -1.3E-15 7.1E-19 -3.0E-22 6.4E-26

[0087] This embodiment provides a projection lens with an aperture number of F1.988, an effective focal length EFL of 70.05 mm, a lens back focal length BFL of 73.5, and a system field of view FOV of 57.12.

[0088] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, 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 regarded as the protection scope of the present invention.

Claims

1. A projection lens, characterized in that: The invention comprises a front lens group, an aperture and a rear lens group arranged from the magnification side to the reduction side, the front lens group comprises a lens 1 and a lens 2 arranged from the magnification side to the reduction side, the lens 1 is a meniscus lens, the refractive power of the lens 2 is positive, and the rear lens group comprises a lens 3 with a negative refractive power, a lens 4 with a positive refractive power, a lens 5 with a positive refractive power and a lens 6 with a positive refractive power arranged from the magnification side to the reduction side.

2. The projection lens according to claim 1, characterized in that: The first lens is a meniscus lens convex toward the reduction side, and the refractive power of the first lens is positive or negative; Alternatively, the refractive power of the lens 1 is negative, and the surface of the lens 1 on the magnification side is a curved surface with the middle portion being concave toward the reduction side and the edge being curved toward the reduction side.

3. The projection lens according to claim 1, characterized in that: The lens three and the lens four are connected to form a double cemented lens, the refractive index of the lens three is greater than the refractive index of the lens four, and the Abbe number of the lens three is less than the Abbe number of the lens four.

4. The projection lens according to claim 3, characterized in that: The lens three is a biconcave lens, and the lens four is a biconvex lens.

5. The projection lens according to claim 1, wherein: There is at least one aspherical lens in the front lens group, and at least one aspherical lens with positive refractive power in the rear lens group.

6. The projection lens according to claim 5, characterized in that: Lens 1 and lens 2 are aspherical lenses, and lens 5 and lens 6 are aspherical lenses.

7. The projection lens according to claim 6, characterized in that: Both side surfaces of the lens 1 and both side surfaces of the lens 2 are even-order aspherical surfaces.

8. The projection lens according to claim 6, wherein: At least one of the surface of lens 5 on the magnification side, the surface of lens 5 on the reduction side, the surface of lens 6 on the magnification side and the surface of lens 6 on the reduction side is an even-order aspherical surface.

9. The projection lens according to claim 6, characterized in that: The lens five is a biconvex lens; The lens six is ​​a meniscus lens convex toward the magnifying side; or, the middle parts of the two side surfaces of the lens six are convex toward the magnifying side, and the edges of the two side surfaces of the lens six are curved toward the magnifying side.

10. The projection lens according to claim 1, wherein: The effective focal length is 60mm≤EFL≤80mm, the relative aperture f-number is 1.7≤FNO≤3.0, the projection ratio is 1.1≤TR≤1.3, the ratio of the lens back focal length to the effective focal length is 0.838≤BFL / EFL, the telecentric angle is TA≤3.0°, the total lens length TTL≤200mm, the field of view angle ≥56.1°, and the ratio of the imaging circle diameter to the total lens length is 0.2≤D / TTL≤0.

5.

11. The projection lens according to claim 1, wherein: The entire projection lens or a part of the lenses in the projection lens can be tilted and adjusted relative to the optical axis.

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