Projection lens

Abstract

The invention relates to the technical field of projection devices, in particular to a projection lens, which comprises a front lens group, an aperture and a rear lens group which are arranged from an amplification side to a reduction side, and aspheric lenses are respectively arranged in the front lens group and the rear lens group. The projection lens is simple and compact in structure, small in number of lenses, small in occupied size, light in weight, large in clear imaging range, capable of supporting tilt shift, high in adaptability to use scenes and capable of guaranteeing clear full-frame imaging and uniform picture illumination and improving the imaging quality.

Description

Technical Field

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

[0002] Projectors are increasingly used, and projection lenses are the core components of projectors, and the requirements for projection lenses are also getting higher and higher. Existing projectors usually use a fixed direction for projection, that is, the projected image is fixed and cannot be adjusted horizontally and vertically relative to the projector, that is, the lens of a traditional projector cannot be shifted, which imposes certain restrictions on the application scenarios of projectors. Projection lenses that support shifting can move and adjust the projected image within a larger range to flexibly meet user needs. Projection lenses that support shifting usually require large apertures and support large field of view imaging to ensure clear full-frame imaging and uniform image illumination. This results in a relatively complex structure of existing projection lenses, a large number of lenses, a large structure volume, a large weight, and a high cost. 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 problems of complex structure, large number of lenses, large structure volume, heavy weight and high cost in the current technology.

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

[0005] A projection lens includes a front lens group, an aperture, and a rear lens group arranged from the magnification side to the reduction side, wherein the front lens group includes a front lens 1 with negative diopter, a front sub-group with negative diopter, a front lens 2 with positive diopter, and a front lens 3 with positive diopter, and the rear lens group includes a rear lens 1 with negative diopter, a rear lens 2 with positive diopter, a rear lens 3 with negative diopter, a rear lens 4 with positive diopter, a rear lens 5 with positive diopter, and a rear lens 6 with positive diopter. The projection lens of the present invention has a simple and compact structure, a small number of lenses, a small occupied volume, a light weight, a large clear imaging range, supports shifting, has strong adaptability to usage scenarios, ensures clear full-frame imaging, uniform picture illumination, and improves imaging quality.

[0006] Furthermore, the front sub-group is composed of a single sub-lens or a combination of two sub-lenses. The structure is simple and compact, occupies a small space, is conducive to the design of lens structure, is easy to implement, and has low cost.

[0007] Furthermore, when the front sub-group is only a single sub-lens, the sub-lens is a double concave negative lens, which has a simple structure, a small number of lenses, is easy to implement, and has a low cost;

[0008] Alternatively, the front sub-group includes sub-lens one and sub-lens two arranged from the magnification side to the reduction side, sub-lens one is a double concave negative lens, and sub-lens two is a meniscus negative lens convex toward the magnification side. The two sub-lenses are combined to form the front sub-group, which can flexibly meet the needs and facilitate the assembly of the lens.

[0009] Furthermore, at least one aspheric lens is provided in the front lens group, and at least one aspheric lens is provided in the rear lens group, and the aspheric lens in the front lens group and the aspheric lens in the rear lens group satisfy the relationship -2≤f_asp1 / f_asp2≤1.0, wherein f_asp1 is the focal length of the aspheric lens in the front lens group, and f_asp2 is the focal length of the aspheric lens in the rear lens group. By reasonably optimizing the aspheric coefficient, the aspheric lens in the front lens group can be used to improve the field of view of the system, and the off-axis aberration and system distortion can be well corrected. The aspheric lens in the rear lens group can be used to correct the spherical aberration and field curvature of the system to improve the optical MTF performance of the lens.

[0010] Furthermore, the front lens 1 is a meniscus aspheric lens convex to the magnification side, and the rear lens 5 is a double convex aspheric lens. Both sides of the front lens 1 are even-order aspheric surfaces. By reasonably optimizing the aspheric coefficient, the system distortion and off-axis aberration are effectively corrected. The double convex aspheric lens used in the rear lens 5 is made of glass material, which improves the molding processability and component accuracy of the aspheric element, and is more mass-producible and reduces costs. The rear lens 5 is located at the position of the principle aperture, and the outer diameter of the rear lens 5 can be reduced and controlled, reducing the sensitivity to the aspheric element itself, and the processing specifications for the aspheric surface can be appropriately relaxed to reduce costs.

[0011] Furthermore, the front lens 2 is an aspherical lens, and both side surfaces of the front lens 2 are even-order aspherical surfaces. By optimizing the aspherical coefficient, the system distortion and off-axis aberration can be better corrected.

[0012] Furthermore, the rear lens 1 is a biconcave lens or a meniscus lens convex toward the magnification side. When the rear lens 1 is a meniscus lens convex toward the magnification side, the back focus size of the lens is small.

[0013] Further, the rear lens 2, the rear lens 3 and the rear lens 4 are connected to form a triplet lens, the refractive index of the rear lens 2 and the rear lens 4 is lower than the refractive index of the rear lens 3, the rear lens 2 and the rear lens 4 are made of a material with a negative Dn / Dt, and the Dn / Dt is the trend of the refractive index changing with temperature. The triplet lens adopts a structure of a combination of high and low refractive indices to effectively correct system chromatic aberration, and the triplet lens is a structure with positive, negative and positive diopters, the rear lens 2 and the rear lens 4 adopt a low refractive index, and the refractive index of the rear lens 2 and the rear lens 4 decreases with the increase of temperature to perform thermal compensation.

[0014] Furthermore, the focal length of the front lens group satisfies 10 mm ≤ f1 ≤ 50 mm, the focal length of the front sub-group satisfies -50 mm ≤ f1a ≤ -10 mm, and the focal length of the rear lens group satisfies 10 mm ≤ f2 ≤ 100 mm. This enables the lens to have a short effective focal length, a small projection ratio for short-distance projection, and achieve a compact lens with low cost and small volume.

[0015] Furthermore, the effective focal length satisfies 2.5 mm ≤ EFL ≤ 5.5 mm, the relative aperture F-number satisfies 1.5 ≤ FNO ≤ 3.0, the projection ratio satisfies 0.6 ≤ TR ≤ 0.7, and the imaging image circle diameter satisfies 0 ≤ φ ≤ 15.605 mm.

[0016] Furthermore, the ratio of the total lens length to the focal length satisfies 20 ≤ TTL / EFL ≤ 30, the ratio of the back focal length to the effective focal length satisfies 3.5 ≤ BFL / EFL ≤ 4.5, the telecentric angle satisfies TA ≤ 1.14°, the total lens length TTL ≤ 118.4 mm, the system field of view FOV ≥ 100.7°, the aperture is set at the focal point position of the rear lens group, the front air spacing of the aperture satisfies 5 mm < T1 < 28 mm, and the lens is adapted to the spectral range of 450 - 650 nm.

[0017] Compared with the prior art, the advantages of the present invention are as follows:

[0018] The projection lens of the present invention has a simple and compact structure, few lens elements, small occupied volume, light weight, is easy to implement and mass-produce, has low cost, small system distortion, small aberration, high resolution, has a large clear imaging range, supports shift, for a 0.23-inch DMD, the longitudinal shift range supported is -200% to +200%, the focusing distance range is 0.5 - 3.5 m, has strong adaptability to the use scenario, ensures clear imaging of the full frame, uniform picture illumination, and improves the imaging quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of a projection lens according to Embodiment 1 of the present invention;

[0020] Figure 2 It is a schematic structural diagram of a projection lens according to Embodiment 2 of the present invention;

[0021] Figure 3 It is a schematic structural diagram of a projection lens according to Embodiment 3 of the present invention;

[0022] Figure 4 It is a schematic structural diagram of a projection lens according to Embodiment 4 of the present invention.

[0023] In the figure:

[0024] Front lens group G1, aperture 10, rear lens group G2, front lens one 11, front sub-group G11, sub-lens one 111, sub-lens two 112, front lens two 12, front lens three 13, rear lens one 21, rear lens two 22, rear lens three 23, rear lens four 24, rear lens five 25, rear lens six 26, galvanometer 2, prism 3, DMD chip 4. 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 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 a small number of lenses, a compact structure, a small occupied volume, a light weight, and a low cost, while ensuring a good imaging effect, having a large clear imaging range, supporting a large range of shift, and having strong adaptability to usage scenarios.

[0027] Embodiment 1

[0028] like Figure 1 As shown, a projection lens mainly includes a front lens group G1, an aperture 10 and a rear lens group G2 which are arranged in sequence from the magnification side to the reduction side, the front lens group G1 includes a front lens 1 11 with negative refractive power, a front sub-group G11 with negative refractive power, a front lens 2 12 with positive refractive power and a front lens 3 13 with positive refractive power which are arranged in sequence from the magnification side to the reduction side, and the rear lens group G2 includes a rear lens 1 21 with negative refractive power, a rear lens 2 22 with positive refractive power, a rear lens 3 23 with negative refractive power, a rear lens 4 24 with positive refractive power, a rear lens 5 25 with positive refractive power and a rear lens 6 26 with positive refractive power which are arranged in sequence from the magnification side to the reduction side.

[0029] In this embodiment, at least one aspheric lens is provided in the front lens group G1, and at least one aspheric lens is provided in the rear lens group G2. The focal length range of the aspheric lens in the front lens group G1 is -50mm≤f_asp1≤-10mm, and the focal length range of the aspheric lens in the rear lens group G2 is -100mm≤f_asp2≤100mm. In addition, the aspheric lens in the front lens group G1 and the aspheric lens in the rear lens group G2 satisfy the relationship -2≤f_asp1 / f_asp2≤1.0. Furthermore, the focal length of the front lens group G1 is 10mm≤f1≤50mm, the focal length of the front sub-group G11 is -50mm≤f1a≤-10mm, and the focal length of the rear lens group G2 is 10mm≤f2≤100mm, thereby realizing short-distance wide-angle projection, low chromatic aberration, low distortion, large aperture 10, low cost, and high imaging quality of the projection lens.

[0030] Specifically, the front lens 11 is a meniscus aspheric negative lens convex to the magnifying side, and is made of resin lens. The radius of curvature of the magnifying side surface of the front lens 11 is 50mm~150mm, and the radius of curvature of the reducing side surface is 7mm~15mm. Both the magnifying side surface and the reducing side surface are even-order aspheric surfaces. The aspheric lens in the front lens group G1 can be used to improve the field of view of the system, and the system distortion and off-axis aberration can be effectively corrected by reasonably optimizing the aspheric coefficient.

[0031] In this embodiment, the front sub-group G11 is composed of two sub-lenses, which specifically include a sub-lens 1 111 and a sub-lens 112 arranged from the magnification side to the reduction side. The sub-lens 1 111 is a double concave negative lens, and the sub-lens 112 is a meniscus negative lens convex to the magnification side. It has a simple structure, a small number of lenses, is easy to implement, has low cost, and is conducive to the assembly of lenses. The curvature radius of the magnification side surface of the sub-lens 111 is -80mm to -30mm, the curvature radius of the reduction side surface of the sub-lens 111 is 15mm to 40mm, the curvature radius of the magnification side surface of the sub-lens 112 is 40mm to 100mm, and the curvature radius of the reduction side surface is 15mm to 50mm.

[0032] The front lens 12 is a plano-convex positive lens, the magnifying side surface is a plane, and the curvature radius of the reducing side surface is -50mm to -20mm.

[0033] The front lens 3 13 is a convex-concave positive lens, the curvature radius of the magnifying side surface is 20mm-50mm, and the curvature radius of the reducing side surface is 200mm-400mm. The front lens 2 12 and the front lens 3 13 play the role of gathering light and reducing the aperture.

[0034] The aperture 10 is adjustable in size, and the aperture 10 is continuously adjustable to meet the application requirements of different scenes. When high brightness is required, the aperture 10 can be adjusted to the maximum to achieve it. When used in a darker environment and the brightness is desired to be darker, the aperture 10 can be appropriately reduced. The aperture 10 is set at the focal position of the rear lens group G2, and the air spacing in front of the aperture 10 meets 5mm. <T1<28mm。

[0035] The rear lens 1 21 is a negative meniscus lens convex to the magnifying side, the curvature radius of the magnifying side surface is 50mm-200mm, and the curvature radius of the L6 reducing side surface is 8mm-30mm;

[0036] The rear lens 2 22, the rear lens 3 23 and the rear lens 4 24 are connected to form a triple cemented lens. The refractive index of the rear lens 2 22 and the rear lens 4 24 is lower than that of the rear lens 3 23. The rear lens 2 22 and the rear lens 4 24 are made of a material with a negative Dn / Dt, and the Dn / Dt is the trend of the refractive index changing with temperature. The rear lens 2 22 is a double convex positive lens, and the curvature radius of its magnifying side surface is 10mm to 30mm, and the curvature radius of its reducing side surface is -30mm to -5mm. The rear lens 3 23 is a double concave negative lens, and the curvature radius of its magnifying side surface is -30mm to -5mm, and the curvature radius of its reducing side surface is 10mm to 30mm. The rear lens 4 24 is a double convex positive lens, and the curvature radius of its magnifying side surface is 10mm to 30mm, and the curvature radius of its reducing side surface is -200mm to -50mm m, the rear lens 22 and the rear lens 4 24 in the triplet lens are composed of a low refractive index, high Abbe number, and negative dn / dt material and a double concave, high refractive index, and low Abbe number material of the rear lens 3 23, and can be designed to be achromatic, ensuring that the entire optical system has a smaller chromatic aberration while compensating for the thermal compensation of the entire optical system. This system can be adapted to the 450-660nm illumination band, and its design wavelength is shorter for blue waves and longer for red waves. The triplet lens is used to effectively correct the chromatic aberration caused by the increase in spectral bandwidth.

[0037] The rear lens five 25 is a biconvex positive aspherical lens. The radius of curvature of its magnifying side surface is 25 mm to 150 mm, and the radius of curvature of the side surface of L10 close to the reducing side of the DMD is -30 mm to -10 mm. Both its magnifying side surface and reducing side surface are even aspheres. The biconvex aspherical lens adopted by the rear lens five 25 uses a glass material. The selected glass material of the rear lens five 25 has a refractive index in the range of 1.50 to 1.60 and an Abbe number in the range of 55 to 75. By designing appropriate curvatures, intervals, and aspherical parameters, the spherical aberration and field curvature of the system can be effectively corrected to improve the optical MTF performance of the lens. Moreover, the aspherical lens designed into a biconvex positive lens structure can improve the molding processability and element accuracy of the aspherical element, is more suitable for mass production, reduces costs. The rear lens five 25 is located at a position far from the aperture 10. The outer diameter of the rear lens five 25 can be controlled to be reduced, reducing the sensitivity to the aspherical element itself, and the processing specifications of the aspherical can be appropriately relaxed, reducing costs.

[0038] The rear lens six 26 is a biconvex lens with a positive diopter. The radius of curvature of its magnifying side surface is 50 mm to 150 mm, and the radius of curvature of the side surface of L11 close to the reducing side of the DMD is -80 mm to -20 mm.

[0039] The projection lens described in this embodiment adopts the above lens structure, which can effectively improve the chromatic aberration of the system and suppress the occurrence of system distortion. Under the design of the image circle target surface of 10.17 mm, the number of entire optical lenses used is small, the structure is simplified, the focal length is small, the field of view angle is large, the projection ratio is small, the aperture 10 diameter is large, the distortion is low, the cost is low, and high-performance MTF values can be ensured at high temperatures.

[0040] This embodiment provides a shiftable-axis projection lens with a short focal length, a small projection ratio, a large field of view, and a large aperture, realizing short-distance wide-angle projection, low chromatic aberration, low distortion, a large-aperture aperture 10, low cost, and high imaging quality of the projection lens. Specifically, the effective focal length of the projection lens is 2.5 mm ≤ EFL ≤ 5.5 mm, the relative aperture number of the aperture 10 is 1.5 ≤ FNO ≤ 3.0, Fno = effective focal length of the lens / diameter of the aperture 10. When the focal length of the lens remains unchanged, the larger the diameter of the aperture 10, the larger the light passing port, and the more light rays can be received, so the higher the brightness. The projection ratio is 0.6 ≤ TR ≤ 0.7, and the imaging image circle diameter is 0 ≤ φ ≤ 15.605 mm; the ratio of the total lens length to the focal length is 20 ≤ TTL / EFL ≤ 30, the ratio of the back focal length of the lens to the effective focal length is 3.5 ≤ BFL / EFL ≤ 4.5, the telecentric angle is TA ≤ 1.14°, the total lens length TTL ≤ 118.4 mm, the system field of view angle FOV ≥ 100.7°. The aperture is set at the focal position of the rear lens group. The front air spacing of the aperture 10 is 5 mm < T1 < 28 mm. The lens is adapted to a spectrum of 450 to 650 nm, the spectrum is relatively wider, the blue wave of the wavelength is shorter, and the red wave is longer.

[0041] Furthermore, the projection system using the above-mentioned projection lens further comprises a galvanometer 2, a prism 3, a protective glass and a DMD chip 4 which are sequentially arranged on the reduction side of the rear lens 6 26 along the direction from the magnification side to the reduction side. The physical resolution of the DMD chip 4 is 93lp / mm. The light passes through the prism 3 and the galvanometer 2 from the DMD chip 4 and enters the projection lens, and finally is emitted from the projection lens to the projection surface to realize projection imaging. The aperture 10 is driven by the driving mechanism to adjust the aperture size of the aperture 10 to meet the needs of different scenes. The galvanometer 2 is driven by the driving device to shake. The galvanometer 2 is used to enable the projection system to simultaneously obtain the fixed size of the DMD chip 4 itself when the galvanometer 2 is stationary. The galvanometer 2 has a high resolution and a high resolution when the galvanometer 2 is working and shaking. With the 0.23-inch DMD chip 4, a 228.6cm (80-inch) screen can be projected at a working distance of 1417mm. The 0.23-inch DMD supports a longitudinal shift range of -200% to +200%, and a focusing distance range of 0.5 to 3.5m. When the optical axis of the projection lens is translated, the projected image will move in the same direction. During the movement of the lens, the overall image remains clear and stable except for the movement of the image. The projection lens has good MTF performance at a spatial frequency of 93lp / mm and in the visible light range of 450nm to 655nm, with small distortion, simple structure and good imaging quality.

[0042] Specific parameters of a projection system are shown in Table 1.

[0043] Table 1

[0044]

[0045]

[0046] Among them, the front lens 11 and the rear lens 5 25 are aspherical lenses, and the remaining lenses are spherical lenses. The aspherical polynomial formula is:

[0047]

[0048] 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.

[0049] When the k coefficient is less than -1, the surface curve of the lens is a hyperbola;

[0050] When the k coefficient is equal to -1, the surface curve of the lens is a parabola;

[0051] When the k coefficient is between -1 and 0, the surface curve of the lens is an ellipse;

[0052] When the k coefficient is equal to 0, the surface curve of the lens is circular;

[0053] When the k coefficient is greater than 0, the surface curve of the lens is an oblate circle.

[0054] Table 2

[0055] k <![CDATA[α2]]> <![CDATA[α3]]> <![CDATA[α4]]> <![CDATA[α5]]> <![CDATA[α6]]> <![CDATA[α7]]> <![CDATA[α8]]> S1 -15.0 3.1E-05 -7.4E-08 4.9E-10 -2.7E-12 8.1E-15 -1.2E-17 6.9E-21 S2 -0.3 -6.2E-06 2.7E-07 -8.5E-09 1.5E-10 -1.4E-12 5.7E-15 -9.2E-18 S20 1.3 8.4E-05 3.0E-07 1.3E-07 6.7E-09 1.8E-10 2.4E-12 1.3E-14 S21 -7.4 -1.5E-04 1.1E-06 9.6E-09 -3.0E-10 3.1E-12

[0056] This embodiment provides a projection lens with an aperture of 10, F1.7, a distortion of less than 0.4%, a focal length of 4.21 mm, and a ratio of back focal length to effective focal length of 3_5≤BFL / EFL≤4.5. The lens has a precise structure, and is low cost, small size, small aberration, high resolution, simple structure, support for shift, and a large imaging clarity range. Support for a wide range of shift allows users to have more setting options and is more adaptable to usage scenarios.

[0057] Embodiment 2

[0058] like Figure 2 As shown, the main difference compared with the first embodiment is that the front sub-group G11 is composed of a single sub-lens, and the sub-lens is a double concave negative lens, with a small number of lenses, a more compact structure, a small occupied space, and a low implementation cost;

[0059] Specifically, the front lens 11 of the front lens group G1 is set as an aspheric lens with a negative refractive power, and the lens material is resin. The front lens 11 includes a magnifying side surface and a reducing side surface. The magnifying side surface and the reducing side surface are both even-order aspheric surfaces. By reasonably optimizing the aspheric coefficient, the system distortion and off-axis aberration are effectively corrected; the front lens 2 12 is a plano-convex lens with a positive refractive power, and the front lens 3 13 is a convex-plano lens with a positive refractive power;

[0060] The rear lens 1 21 of the rear lens group G2 is a meniscus negative lens convex toward the magnification side, the rear lens 2 22, the rear lens 3 23 and the rear lens 4 24 are connected to form a three-cemented lens, the refractive powers of the rear lens 2 22, the rear lens 3 23 and the rear lens 4 24 are positive, negative and positive respectively, the Abbe numbers of the rear lens 2 22 and the rear lens 4 24 are both greater than 81, the rear lens 5 25 is a double convex positive aspheric lens, and the rear lens 6 26 is a double convex lens with positive refractive power.

[0061] Specific parameters of the projection system using the above projection lens are shown in Table 3.

[0062] Table 3

[0063]

[0064]

[0065] And the aspheric coefficients corresponding to the second to sixteenth orders such as α1 to α8 in the aspheric polynomial formula are shown in Figure 4.

[0066] Table 4

[0067] k <![CDATA[α2]]> <![CDATA[α3]]> <![CDATA[α4]]> <![CDATA[α5]]> <![CDATA[α6]]> <![CDATA[α7]]> <![CDATA[α8]]> <![CDATA[α9]]> <![CDATA[α 10 ]]> S1 3.2 2.5E-05 3.9E-07 -5.1E-09 3.1E-11 -1.0E-13 2.1E-16 -2.4E-19 1.2E-22 0.00 S2 -1.0 6.2E-05 -9.0E-07 7.2E-08 -1.7E-09 2.3E-11 -1.8E-13 8.4E-16 -2.2E-18 2.6E-21 S18 -0.7 -2.7E-05 2.8E-06 -2.8E-07 2.0E-08 -8.2E-10 1.9E-11 -2.4E-13 1.3E-15 0.00 S19 -23.9 -1.1E+00 2.2E-05 2.2E-08 1.6E-08 -2.1E-10 2.2E-12 0.00 0.00 0.00

[0068] This embodiment provides a projection lens with an aperture of F1.7, an effective focal length EFL of 4.2 mm, a lens back focal length BFL of 15_2, and a system field of view FOV of 100.95.

[0069] Embodiment 3

[0070] like Figure 3 As shown, the main difference compared with the first embodiment is that the rear lens 1 21 in the rear lens group G2 is a biconcave lens, and the back focal size of the lens is small;

[0071] Specifically, the front lens 11 of the front lens group G1 is set as an aspheric lens with a negative refractive power, and the lens material is resin. The front lens 11 includes a magnifying side surface and a reducing side surface, and the magnifying side surface and the reducing side surface are both even-order aspheric surfaces. By reasonably optimizing the aspheric coefficient, the system distortion and off-axis aberration are effectively corrected;

[0072] The front subgroup G11 is composed of two sub-lenses, which specifically include a sub-lens 111 and a sub-lens 112 arranged from the magnification side to the reduction side, wherein the sub-lens 111 is a double concave negative lens, and the sub-lens 112 is a meniscus negative lens convex toward the magnification side;

[0073] The front lens 2 12 is a plano-convex lens with positive refractive power, and the front lens 3 13 is a convex-plano lens with positive refractive power;

[0074] The rear lens 2 22, the rear lens 3 23 and the rear lens 4 24 of the rear lens group G2 are connected to form a three-cemented lens, and the refractive powers of the rear lens 2 22, the rear lens 3 23 and the rear lens 4 24 are positive, negative and positive respectively. The Abbe numbers of the rear lens 2 22 and the rear lens 4 24 are both greater than 81, the rear lens 5 25 is a double convex positive aspheric lens, and the rear lens 6 26 is a double convex lens with positive refractive power.

[0075] The specific parameters of the projection system using the above projection lens are shown in Table 5.

[0076] Table 5

[0077]

[0078]

[0079] And the aspheric coefficients corresponding to the second to sixteenth orders such as α1 to α8 in the aspheric polynomial formula are shown in Figure 6.

[0080] Table 6

[0081] k <![CDATA[α2]]> <![CDATA[α3]]> <![CDATA[α4]]> <![CDATA[α5]]> <![CDATA[α6]]> <![CDATA[α7]]> <![CDATA[α8]]> S1 -13.9 5.4E-05 -3.0E-07 1.8E-09 -7.5E-12 1.9E-14 -2.5E-17 1.4E-20 S2 -1.0 6.5E-05 3.6E-07 -1.4E-08 2.4E-10 -1.9E-12 7.4E-15 -1.1E-17 S20 -12.3 5.3E-05 -7.2E-07 7.2E-08 -3.2E-09 8.8E-11 -1.2E-12 7.0E-15 S21 -20.4 -7.5E-05 1.6E-06 -1.3E-08 1.5E-10 1.2E-13

[0082] This embodiment provides a projection lens with an aperture of F1.7001, an effective focal length EFL of 4.21 mm, a lens back focal length BFL of 15.2, and a system field of view FOV of 100.76.

[0083] Embodiment 4

[0084] like Figure 4 As shown, the main difference compared with the first embodiment is that the front sub-group G11 is composed of a single sub-lens, the sub-lens is a double concave negative lens, the number of lenses is small, the structure is more compact, the space occupied is small, and the implementation cost is low. The front lens 12 is an aspherical lens, and the front lens 12 is a meniscus positive lens convex to the reduction side. The magnification side surface and the reduction side surface of the front lens 12 are both even-order aspherical surfaces. By reasonably optimizing the aspheric coefficient, the system distortion and off-axis aberration are effectively corrected. The front lens 13 is a double convex lens with positive refractive power;

[0085] More specifically, the front lens 11 of the front lens group G1 is set to be an aspheric lens with a negative refractive power, and the lens material is resin. The front lens 11 includes a magnifying side surface and a reducing side surface, and the magnifying side surface and the reducing side surface are both even-order aspheric surfaces. By reasonably optimizing the aspheric coefficient, the system distortion and off-axis aberration are effectively corrected;

[0086] The rear lens 1 21 of the rear lens group G2 is a meniscus negative lens convex toward the magnification side, the rear lens 2 22, the rear lens 3 23 and the rear lens 4 24 are connected to form a three-cemented lens, the refractive powers of the rear lens 2 22, the rear lens 3 23 and the rear lens 4 24 are positive, negative and positive respectively, the Abbe numbers of the rear lens 2 22 and the rear lens 4 24 are both greater than 81, the rear lens 5 25 is a double convex positive aspheric lens, and the rear lens 6 26 is a double convex lens with positive refractive power.

[0087] The specific parameters of the projection system using the above projection lens are shown in Table 7.

[0088] Table 7

[0089]

[0090]

[0091] And the aspheric coefficients corresponding to the 2nd to 16th orders such as α1 to α8 in the aspheric polynomial formula are shown in Figure 8.

[0092] Table 8

[0093] k <![CDATA[α2]]> <![CDATA[α3]]> <![CDATA[α4]]> <![CDATA[α5]]> <![CDATA[α6]]> <![CDATA[α7]]> <![CDATA[α8]]> <![CDATA[α9]]> <![CDATA[α 10 ]]> S1 2.8 -1.1E-05 7.2E-07 -6.3E-09 2.8E-11 -6.3E-14 2.6E-17 1.9E-19 -4.0E-22 2.6E-25 S2 -1.0 -6.7E-06 -3.5E-07 4.7E-08 -9.2E-10 8.7E-12 -4.5E-14 1.3E-16 -2.0E-19 1.3E-22 S5 0.0 -2.9E-05 -2.4E-07 6.6E-09 -7.4E-11 4.5E-13 -1.6E-15 2.9E-18 0.0 0.0 S6 0.1 -1.6E-05 -1.7E-07 4.6E-09 -5.5E-11 3.7E-13 -1.4E-15 2.5E-18 0.0 0.0 S18 0.0 -1.2E-04 7.1E-06 -7.2E-07 4.4E-08 -1.7E-09 4.0E-11 -5.9E-13 4.7E-15 -1.6E-17 S19 0.0 -6.2E-05 3.7E-07 -1.7E-08 2.6E-10 -5.9E-13 -8.7E-15 3.7E-17 0.0 0.0

[0094] This embodiment provides a projection lens with an aperture of F1.7, an effective focal length EFL of 4.22 mm, a lens back focal length BFL of 17_2, and a system field of view FOV of 100.67.

[0095] 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: It includes a front lens group, an aperture, and a rear lens group arranged in the direction from the magnifying side to the reducing side. The front lens group includes a first front lens with a negative diopter, a front sub-group with a negative diopter, a second front lens with a positive diopter, and a third front lens with a positive diopter, which are arranged in the direction from the magnifying side to the reducing side. The rear lens group includes a first rear lens with a negative diopter, a second rear lens with a positive diopter, a third rear lens with a negative diopter, a fourth rear lens with a positive diopter, a fifth rear lens with a positive diopter, and a sixth rear lens with a positive diopter, which are arranged in the direction from the magnifying side to the reducing side.

2. The projection lens according to claim 1, characterized in that: The front sub-group is composed of a single sub-lens or a combination of two sub-lenses.

3. The projection lens according to claim 2, characterized in that: When the front sub-group is only a single sub-lens, the sub-lens is a biconcave negative lens; Or, the front sub-group includes a first sub-lens and a second sub-lens arranged in the direction from the magnifying side to the reducing side. The first sub-lens is a biconcave negative lens, and the second sub-lens is a meniscus negative lens convex to the magnifying side.

4. The projection lens according to claim 1, characterized in that: At least one aspherical lens is provided in the front lens group, and at least one aspherical lens is provided in the rear lens group. The aspherical lens in the front lens group and the aspherical lens in the rear lens group satisfy the relationship -2 ≤ f_asp1 / f_asp2 ≤ 1.0, where f_asp1 is the focal length of the aspherical lens in the front lens group, and f_asp2 is the focal length of the aspherical lens in the rear lens group.

5. The projection lens according to claim 1, wherein: The first front lens is a meniscus aspherical lens convex to the magnifying side, and the fifth rear lens is a biconvex aspherical lens.

6. The projection lens according to claim 5, characterized in that: The second front lens is an aspherical lens.

7. The projection lens according to claim 1, wherein: The first rear lens is a biconcave lens or a meniscus lens convex to the magnifying side.

8. The projection lens according to claim 1, wherein: The second rear lens, the third rear lens, and the fourth rear lens are connected as a triple cemented lens. The refractive indices of the second rear lens and the fourth rear lens are lower than that of the third rear lens. The second rear lens and the fourth rear lens are made of a material with a negative Dn / Dt, where Dn / Dt is the trend of the refractive index changing with temperature.

9. The projection lens according to claim 1, wherein: The focal length of the front lens group is 10mm ≤ f1 ≤ 50mm, the focal length of the front sub-group is -50mm ≤ f1a ≤ -10mm, and the focal length of the rear lens group is 10mm ≤ f2 ≤ 100mm.

10. The projection lens according to claim 1, wherein: The effective focal length is 2.5mm ≤ EFL ≤ 5.5mm, the relative aperture F-number is 1.5 ≤ FNO ≤ 3.0, the projection ratio is 0.6 ≤ TR ≤ 0.7, and the imaging image circle diameter is 0 ≤ φ ≤ 15.605mm.

11. The projection lens according to claim 1, wherein: The ratio of the total length of the lens to the focal length is 20 ≤ TTL / EFL ≤ 30, the ratio of the back focal length of the lens to the effective focal length is 3.5 ≤ BFL / EFL ≤ 4.5, the telecentric angle is TA ≤ 1.14°, the total length of the lens TTL ≤ 118.4mm, the system field of view FOV ≥ 100.7°, the aperture is set at the focal point position of the rear lens group, the front air spacing of the aperture is 5mm < T1 < 28mm, and the lens is adapted to the spectral range of 450 - 650nm.

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