Projection lens and imaging device

Abstract

The invention relates to the technical field of projection, in particular to a projection lens and an imaging device. The projection lens provided by the invention is sequentially and coaxially provided with a first lens, a second lens, a diaphragm, a third lens, a fourth lens and a fifth lens along the light emitting direction of an LCD (Liquid Crystal Display); wherein the first lens is a biconvex lens, the second lens is a biconcave lens, and a light emergent surface of the first lens is attached to a light incident surface of the second lens through photosynthetic glue to form a front lens group; the third lens is an aspheric positive focal length convex lens, the fourth lens and the fifth lens are both meniscus negative focal length lenses, and the end of the third lens on the light emergent face is attached to the end of the light incident face of the fourth lens. The center of the light emergent face of the fourth lens is attached to the center of the light incident face of the fifth lens, and the third lens, the fourth lens and the fifth lens form a rear lens set.

Description

Technical Field

[0001] The present invention relates to the field of projection technology, and in particular to a projection lens and an imaging device. Background Art

[0002] LCD projection lenses are key optical components in modern projection display systems. They illuminate liquid crystal display panels with a high-brightness light source and utilize precision-engineered lenses to project high-quality images onto the screen, achieving realistic and detailed imaging. Current projection lenses for 5-inch LCD display panels, such as the panoramic high-definition projection lens disclosed in patent publication number CN221707798U, are used for projecting images with a 1920*1080 pixel resolution. However, their optical design only achieves an FNO of 2.9, making it difficult to further reduce this to meet requirements for higher brightness or lower noise. Summary of the Invention

[0003] In a first aspect, the present invention provides a projection lens for LCD projection, characterized in that a first lens, a second lens, an aperture, a third lens, a fourth lens, and a fifth lens are coaxially arranged in sequence along the light emitting direction of the LCD; wherein the first lens is a biconvex lens, the second lens is a biconcave lens, and the light emitting surface of the first lens and the light incident surface of the second lens are bonded together by photosynthetic glue to form a front lens group; the third lens is an aspherical positive focal length convex lens, the fourth lens and the fifth lens are both meniscus negative focal length lenses, the end of the light emitting surface of the third lens is bonded to the end of the light incident surface of the fourth lens, and the center of the light emitting surface of the fourth lens is bonded to the center of the light incident surface of the fifth lens, and the third lens, the fourth lens, and the fifth lens form a rear lens group.

[0004] In some embodiments, the air gap between the front lens group and the rear lens group ranges from 7.2 mm to 7.5 mm.

[0005] In some embodiments, the radius of curvature of the light incident surface of the first lens is +56.461mm to +56.661mm; the radius of curvature of the light exit surface of the first lens is -70.867mm to -71.067mm, the center thickness of the first lens is 17.07mm to 17.17mm, the edge thickness of the first lens is 1.294mm to 1.314mm, and the refractive index range of the first lens is 1.687-1.747; the radius of curvature of the light incident surface of the second lens is -70.867mm to -71.067mm m; the radius of curvature of the light exit surface of the second lens is +56.461mm to +56.661mm, the center thickness of the second lens is 1.75mm to 1.85mm, the edge thickness of the second lens is 14.503mm to 14.513mm, and the refractive index range of the second lens is 1.6901-1.6501; the vertex curvature radius of the light incident surface of the third lens is +51.235mm to +51.335mm; the vertex curvature radius of the light exit surface of the third lens is +41.083mm to +141.283m m, the center thickness of the third lens is 2.5mm to 2.9mm, the edge thickness of the third lens is 4.459mm to 4.479mm, and the refractive index range of the third lens is 1.5525-1.6125; the vertex curvature radius of the light incident surface of the fourth lens is -43.022mm to -43.222mm; the curvature radius of the light exit surface of the fourth lens is -114.469mm to -114.669mm, the center thickness of the fourth lens is 1.75mm to 1.85mm, and the edge thickness of the fourth lens is 6. The diameter of the optical fiber is 398mm-6.418mm, the refractive index of the fourth lens is in the range of 1.5734-1.6334; the vertex curvature radius of the light incident surface of the fifth lens is in the range of -272.823mm to -273.023mm; the curvature radius of the light exit surface of the fifth lens is in the range of -46.098mm to -46.298mm, the center thickness of the fifth lens is in the range of 11.62mm to 11.72mm, the edge thickness of the fifth lens is in the range of 1.527mm to 1.547mm, and the refractive index of the fifth lens is in the range of 1.687-1.747.

[0006] In some embodiments, the light incident surface of the third lens is a first aspheric surface, and the cone constant, fourth-order aspheric coefficient, sixth-order aspheric coefficient, eighth-order aspheric coefficient, tenth-order aspheric coefficient, twelfth-order aspheric coefficient, and fourteenth-order aspheric coefficient of the first aspheric surface are 0.3672, 1.32711e-05, 7.871e-09, 6.238e-12, -1.46e-14, 3.33461e-17, and -2.121e-09, respectively. 20; The light emitting surface of the third lens is a second aspheric surface, and the cone constant, fourth-order aspheric coefficient, sixth-order aspheric coefficient, eighth-order aspheric coefficient, tenth-order aspheric coefficient, twelfth-order aspheric coefficient and fourteenth-order aspheric coefficient of the second aspheric surface are 0, 1.16271e-05, 8.403359e-09, -1.6654e-11, -1.6654e-15, 7.57263e-18 and -7.4958e-21 respectively.

[0007] In some embodiments, the first lens is made of H-LAF2, the second lens is made of H-F4, and the third lens is made of AD5. 5 03. The fourth lens is made of H-F1, and the fifth lens is made of H-LAF2.

[0008] In a second aspect, the present invention further provides an imaging device based on the projection lens proposed in the first aspect, which includes the above-mentioned projection lens and an imaging element, wherein the imaging element is arranged on the light-emitting side of the projection lens and is used to receive the optical image projected by the projection lens.

[0009] In some embodiments, the distance between the imaging element and the light emitting surface of the fifth lens in the optical axis direction ranges from 1000 mm to 4200 mm.

[0010] In a second aspect, the present invention, based on the projection lens proposed in the first aspect, further provides an LCD imaging system, which includes an LCD panel, the above-mentioned projection lens, and an imaging element; the projection lens is arranged on the light-emitting side of the LCD panel, and is used to project the optical image output by the LCD panel onto the imaging element; the imaging element is arranged on the light-emitting side of the projection lens, and is used to receive the optical image projected by the projection lens.

[0011] In some embodiments, a Fresnel lens is further disposed between the projection lens and the LCD panel.

[0012] In some embodiments, the distance between the Fresnel lens and the projection lens in the optical axis direction ranges from 102.4 mm to 112.4 mm, and the distance between the Fresnel lens and the LCD panel in the optical axis direction ranges from 10 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic diagram of a projection lens provided by an embodiment of the present invention; Figure 2 A schematic diagram of an imaging device provided by an embodiment of the present invention; Figure 3 A schematic diagram of an LCD imaging system provided by an embodiment of the present invention; Figure 4 This is an MTF curve diagram of the projection lens provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0014] In the following description, for the purpose of illustration rather than limitation, specific details such as specific system structures and technologies are provided to facilitate a thorough understanding of the embodiments of the present application. In the description of this application, the terms "first" and "second" are used only to distinguish descriptions and should not be understood as indicating or implying relative importance.

[0015] To achieve LCD high-definition projection, please refer to Figure 1 , Figure 1 Schematic diagram of a projection lens provided by an embodiment of the present invention; Figure 1 As shown, the projection lens provided by the embodiment of the present invention is coaxially provided with a first lens 1, a second lens 2, an aperture L0, a third lens 3, a fourth lens 4, and a fifth lens 5.

[0016] In this embodiment, the first lens 1 is a biconvex lens, and the second lens 2 is a biconcave lens. Specifically, the first lens 1 is used to receive the highly divergent light beam from the LCD panel and initially converge it along the optical axis. The second lens 2 is used to appropriately diverge the light beam converged by the first lens 1, so that the light beam has a moderate angle when it passes through the aperture L0, neither over-focusing nor over-diverging. Furthermore, the positive and negative combination of the first lens 1 and the second lens 2 can pre-correct low-order aberrations.

[0017] Furthermore, the light exit surface of the first lens 1 and the light incident surface of the second lens 2 are bonded together using photosynthetic adhesive to form the front lens group. Specifically, the use of photosynthetic adhesive to bond the first lens 1 and the second lens 2 replaces the air layer, which not only helps to reduce Fresnel reflections at the bonding interface, but also enables high-precision coaxial positioning to improve the mechanical stability of the system. While eliminating the need for gap spacers or brackets between the two, it helps to simplify the structure and reduce the overall size of the lens barrel.

[0018] In this embodiment, the third lens 3 is an aspherical positive focal length convex lens, the fourth lens 4 is a meniscus negative focal length lens, and the fifth lens 5 is a meniscus positive focal length lens.

[0019] Specifically, the third aspheric positive focal length convex lens performs secondary convergence on the light beam intercepted by the aperture L0, and accurately positions the beam waist in the optimal correction area of ​​the subsequent negative lens. At the same time, the cone constant and high-order aspheric coefficients of the aspheric surface are used to further correct residual low-order spherical aberration, coma and other aberrations.

[0020] Furthermore, the fourth meniscus negative focal length lens introduces a moderate negative focal length divergence, so that the light beam can obtain the necessary beam expansion after converging through the aspheric lens to match the acceptance angle of the imaging element. At the same time, with the help of its meniscus curvature distribution, the coma and astigmatism of the off-axis light are locally compensated.

[0021] Furthermore, the fourth meniscus lens with negative focal length works together with the fifth meniscus lens with positive focal length to flatten the image field, suppress field curvature, ensure uniform imaging at each point on the projection surface, and further compensate for the overall distortion, so that the geometric distortion of the image is controlled within the designed range.

[0022] Furthermore, the end of the light exit surface of the third lens 3 is bonded to the end of the light incident surface of the fourth lens 4, and the center of the light exit surface of the fourth lens 4 is bonded to the center of the light incident surface of the fifth lens 5. The third lens 3, the fourth lens 4, and the fifth lens 5 constitute a rear lens group. In this embodiment, the bonding between the third lens 3, the fourth lens 4, and the fifth lens 5 shortens the axial length of the rear lens group, facilitating the design of an ultra-thin and compact projection lens.

[0023] In another embodiment, to achieve high-definition projection of a 4.0 to 5.5-inch LCD panel, based on the above-mentioned projection lens, the following key parameters are set as shown in the following table:

[0024] It should be noted that "(+)" indicates that the center of curvature of the curvature radius pair is on the light incident side of the corresponding lens, and "(-)" indicates that the center of curvature of the curvature radius is on the light exit side of the corresponding lens; the third lens is an aspherical lens, and the curvature radii of its light incident surface and light exit surface are both its vertex curvature radius.

[0025] Based on the above projection lens, this embodiment further provides an imaging device; see Figure 2 , Figure 2 Schematic diagram of an imaging device provided by an embodiment of the present invention; Figure 2 As shown, the imaging device includes the above-mentioned projection lens S and an imaging element C. The imaging element C is arranged on the light-emitting side of the projection lens S and is used to receive the optical image projected by the projection lens S.

[0026] In this embodiment, an air gap exists between the front lens group consisting of the first lens and the second lens and the rear lens group consisting of the third lens, the fourth lens, and the fifth lens.

[0027] Furthermore, in order to take into account both the compact design of the lens and the projection effect, the air gap ranges from 7.2 mm to 7.5 mm. At the same time, the distance between the light emitting surface of the fifth lens and the imaging element in the optical axis direction ranges from 1000 mm to 4200 mm.

[0028] Furthermore, based on the above imaging device and projection requirements, this embodiment provides an LCD imaging system; see Figure 3 , Figure 3 The LCD imaging system provided by the embodiment of the present invention is as follows: Figure 3 As shown, the imaging system includes an LCD panel L and the above-mentioned imaging device, that is, includes an LCD panel L, the above-mentioned projection lens S and an imaging element C.

[0029] like Figure 3 As shown, the projection lens S is arranged on the light-emitting side of the LCD panel L, and is used to project the optical image output by the LCD panel L to the imaging element C; the imaging element C is arranged on the light-emitting side of the projection lens S, and is used to receive the optical image projected by the projection lens S.

[0030] Specifically, the parameters of the projection lens S in this LCD imaging system are shown in the following table:

[0031] Among them, the two aspheric surfaces based on the third lens are: the light incident surface is the first aspheric surface, the cone constant, fourth-order aspheric coefficient, sixth-order aspheric coefficient, eighth-order aspheric coefficient, tenth-order aspheric coefficient, twelfth-order aspheric coefficient, and fourteenth-order aspheric coefficient of the first aspheric surface are 0.3672, 1.32711e-05, 7.871e-09, 6.238e-12, -1.46e-14, 3.33461e-17, and -2.121e-09, respectively. -20; the light exit surface of the third lens is a second aspheric surface, and the cone constant, fourth-order aspheric coefficient, sixth-order aspheric coefficient, eighth-order aspheric coefficient, tenth-order aspheric coefficient, twelfth-order aspheric coefficient and fourteenth-order aspheric coefficient of the second aspheric surface are 0, 1.16271e-05, 8.403359e-09, -1.6654e-11, -1.6654e-15, 7.57263e-18 and -7.4958e-21 respectively.

[0032] Furthermore, the air gap between the front lens group consisting of the first lens and the second lens and the rear lens group consisting of the third lens, the fourth lens, and the fifth lens is 7.4 mm. Under the above parameter settings, the MTF (Modulation Transfer Function) curve of the projection lens S is as follows: Figure 4 shown.

[0033] In this embodiment, in order to better transmit the light emitted by the LCD panel L to the projection lens S, a Fresnel lens F is further provided between the projection lens S and the LCD panel L; further, the Fresnel lens F focuses and collimates the light emitted by the LCD panel L.

[0034] Specifically, the distance between the Fresnel lens F provided in this embodiment and the projection lens S in the optical axis direction has a numerical range of 102.4 mm to 112.4 mm, the distance between the Fresnel lens F and the LCD panel L in the optical axis direction is 10 mm, and the size of the Fresnel lens F is 118 mm x 67 mm x 1.8 mm.

[0035] It should be noted that, in other embodiments, the size of the Fresnel lens F can be adjusted according to the size of the LCD panel L to ensure that the projection area of ​​the Fresnel lens F in the optical axis direction can cover the projection area of ​​the LCD panel L in the optical axis direction.

[0036] In this embodiment, a projection lens with a total optical system length of 53.9 mm, an effective focal length of 135.45 mm, and an FNO of 2.3 is provided for a 4.0 to 5.5-inch LCD panel. The projection lens can achieve a 40-inch to 160-inch projection screen for a 4.0 to 5.5-inch LCD panel, with the four corners being neither blurry nor weak, and achieving panoramic high-definition imaging with equivalent image quality at the edges and in the center.

[0037] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0038] It should be noted that the above embodiments can be freely combined as needed. The above are only preferred embodiments of the present invention; it should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of the present invention, and such improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A projection lens for LCD projection, characterized in that: Along the direction of light emission from the LCD, a first lens, a second lens, an aperture, a third lens, a fourth lens, and a fifth lens are coaxially arranged in sequence; The first lens is a biconvex lens, the second lens is a biconcave lens, and the light emitting surface of the first lens and the light incident surface of the second lens are bonded together by photosynthetic adhesive to form a front lens group; The third lens is an aspheric positive focal length convex lens, the fourth lens is a meniscus negative focal length lens, and the fifth lens is a meniscus positive focal length lens. The end of the light exit surface of the third lens is bonded to the end of the light incident surface of the fourth lens, and the center of the light exit surface of the fourth lens is bonded to the center of the light incident surface of the fifth lens. The third lens, the fourth lens and the fifth lens constitute a rear lens group.

2. The projection lens according to claim 1, wherein: The air gap between the front lens group and the rear lens group ranges from 7.2 mm to 7.5 mm.

3. The projection lens according to any one of claims 1-2, wherein: The radius of curvature of the light incident surface of the first lens is +56.461 mm to +56.661 mm; the radius of curvature of the light exit surface of the first lens is -70.867 mm to -71.067 mm; the center thickness of the first lens is 17.07 mm to 17.17 mm; the edge thickness of the first lens is 1.294 mm to 1.314 mm; and the refractive index range of the first lens is 1.687-1.747; The radius of curvature of the light incident surface of the second lens is -70.867 mm to -71.067 mm; the radius of curvature of the light exit surface of the second lens is +56.461 mm to +56.661 mm, the center thickness of the second lens is 1.75 mm to 1.85 mm, the edge thickness of the second lens is 14.503 mm to 14.513 mm, and the refractive index range of the second lens is 1.6901-1.6501; The vertex curvature radius of the light incident surface of the third lens is +51.235mm to +51.335mm; the vertex curvature radius of the light exit surface of the third lens is +41.083mm to +141.283mm; the center thickness of the third lens is 2.5mm to 2.9mm; the edge thickness of the third lens is 4.459mm to 4.479mm; and the refractive index range of the third lens is 1.5525-1.6125; The vertex curvature radius of the light incident surface of the fourth lens is -43.022mm to -43.222mm; the curvature radius of the light exit surface of the fourth lens is -114.469mm to -114.669mm; the center thickness of the fourth lens is 1.75mm to 1.85mm; the edge thickness of the fourth lens is 6.398mm to 6.418mm; and the refractive index range of the fourth lens is 1.5734-1.6334; The vertex curvature radius of the light incident surface of the fifth lens is -272.823 mm to -273.023 mm; the curvature radius of the light exit surface of the fifth lens is -46.098 mm to -46.298 mm, the center thickness of the fifth lens is 11.62 mm to 11.72 mm, the edge thickness of the fifth lens is 1.527 mm to 1.547 mm, and the refractive index range of the fifth lens is 1.687-1.

747.

4. The projection lens according to claim 3, characterized in that : The light incident surface of the third lens is a first aspheric surface, and the cone constant, fourth-order aspheric coefficient, sixth-order aspheric coefficient, eighth-order aspheric coefficient, tenth-order aspheric coefficient, twelfth-order aspheric coefficient, and fourteenth-order aspheric coefficient of the first aspheric surface are 0.3672, 1.32711e-05, 7.871e-09, 6.238e-12, -1.46e-14, 3.33461e-17, and -2.121e-20, respectively; The light exit surface of the third lens is a second aspheric surface, and the cone constant, fourth-order aspheric coefficient, sixth-order aspheric coefficient, eighth-order aspheric coefficient, tenth-order aspheric coefficient, twelfth-order aspheric coefficient and fourteenth-order aspheric coefficient of the second aspheric surface are 0, 1.16271e-05, 8.403359e-09, -1.6654e-11, -1.6654e-15, 7.57263e-18 and -7.4958e-21 respectively.

5. The projection lens according to claim 4, wherein: The first lens is made of H-LAF2, the second lens is made of H-F4, and the third lens is made of AD5. 5 03. The fourth lens is made of H-F1, and the fifth lens is made of H-LAF2.

6. An imaging device, characterized in that: The invention comprises the projection lens according to any one of claims 1 to 5, and an imaging element, wherein the imaging element is arranged on the light-emitting side of the projection lens and is used to receive the optical image projected by the projection lens.

7. The imaging device according to claim 6, wherein The distance between the imaging element and the light emitting surface of the fifth lens in the optical axis direction ranges from 1000 mm to 4200 mm.

8. An LCD imaging system, characterized in that: comprising an LCD panel, the projection lens according to any one of claims 1 to 5, and an imaging element; The projection lens is arranged on the light-emitting side of the LCD panel, and is used to project the optical image output by the LCD panel to the imaging element; the imaging element is arranged on the light-emitting side of the projection lens, and is used to receive the optical image projected by the projection lens.

9. The LCD imaging system according to claim 8, wherein: A Fresnel lens is further arranged between the projection lens and the LCD panel.

10. The LCD imaging system according to claim 8, wherein: The distance between the Fresnel lens and the projection lens in the optical axis direction ranges from 102.4 mm to 112.4 mm, and the distance between the Fresnel lens and the LCD panel in the optical axis direction ranges from 10 mm.

Images