Projection lens and projection equipment

Abstract

The embodiment of the utility model discloses a projection lens and a projection device, the projection lens comprises a first lens, a second lens, a third lens, a Fresnel lens and a screen assembly, and the centers of the first lens, the second lens, the third lens, the Fresnel lens and the screen assembly are located on the same straight line. The second lens is located between the first lens and the third lens, the Fresnel lens is located on the side, away from the second lens, of the first lens, the screen assembly is arranged on the side, away from the first lens, of the Fresnel lens, and light emitted by the screen assembly sequentially passes through the Fresnel lens, the first lens, the second lens and the third lens to be emitted to a preset position; wherein the first lens and the third lens are positive lenses, the second lens is a negative lens, and the second lens is an aspheric lens. Through the above mode, the projection lens provided by the embodiment of the utility model can have relatively high resolution and relatively low optical distortion, thereby improving the display effect of a picture formed by the projection lens.

Description

Technical Field

[0001] The embodiments of the present utility model relate to the technical field of optical projection, and particularly to a projection lens and a projection device. Background Art

[0002] The existing projection lens includes multiple lenses, which converge, diverge, and correct the light emitted by the image source, so as to magnify the image source and form a display screen for the user to observe the formed screen.

[0003] During the implementation of the embodiments of the present utility model, the inventor found that: most of the lenses used in the existing projection lenses are spherical lenses, and the display effect of the formed display screen is poor. Summary of the Utility Model

[0004] The main technical problem to be solved by the embodiments of the present utility model is to provide a projection lens and a projection device, which can enable the projection lens to have high resolution and low optical distortion, so that the formed display screen of the projection lens has a good display effect.

[0005] To solve the above technical problem, a technical solution adopted by the embodiments of the present utility model is: to provide a projection lens, including a first lens, a second lens, a third lens, a Fresnel lens, and a screen assembly. The centers of the first lens, the second lens, the third lens, the Fresnel lens, and the screen assembly are located on the same straight line. The second lens is located between the first lens and the third lens. The Fresnel lens is located on the side of the first lens away from the second lens. The screen assembly is arranged on the side of the Fresnel lens away from the first lens. The light emitted by the screen assembly sequentially passes through the Fresnel lens, the first lens, the second lens, and the third lens and exits to a preset position. Among them, both the first lens and the third lens are positive lenses, the second lens is a negative lens, and the second lens is an aspherical lens. In this embodiment, by arranging a Fresnel lens between the screen assembly and the first lens, the light emitted by the screen assembly can be converged, and the brightness and uniformity of the light can be improved, and the quality of the display screen can be enhanced. By setting the second lens as an aspherical lens, compared with a spherical lens, more degrees of freedom can be provided for the projection lens to optimize the design, so as to improve the resolution of the projection lens and reduce the optical distortion of the projection lens, thereby further improving the quality of the display screen formed by the lens.

[0006] In some embodiments, the second lens is made of polycarbonate. In this embodiment, the second lens is made of polycarbonate. During the manufacturing process, mold injection molding can be used, which can improve production efficiency and the shape quality of the formed aspherical surface.

[0007] In some embodiments, the surface of the second lens facing the first lens is the first surface, the conic coefficient of the first surface is K1, the surface of the second lens facing the third lens is the second surface, the conic coefficient of the second surface is K2, and at least one of the conditions (a) and (b) is satisfied:

[0008] (a) 0.14 ≤ K1 ≤ 0.16;

[0009] (b) -0.046 ≤ K2 ≤ -0.042.

[0010] In some embodiments, the refractive index of the second lens is 1.5 to 1.65, and the Abbe number of the second lens is 25 to 35.

[0011] In some embodiments, the surface of the first lens facing the Fresnel lens is the third surface, the radius of curvature of the third surface is R1, the surface of the first lens facing the second lens is the fourth surface, the radius of curvature of the fourth surface is R2, and at least one of the conditions (c) and (d) is satisfied:

[0012] (c) -80 mm ≤ R1 ≤ -50 mm;

[0013] (d) 100 mm ≤ R2 ≤ 200 mm.

[0014] In some embodiments, the refractive index of the first lens is 1.65 to 1.70, and the Abbe number of the first lens is 50 to 60.

[0015] In some embodiments, the surface of the third lens facing the second lens is the fifth surface, the radius of curvature of the fifth surface is R3, the surface of the third lens facing away from the second lens is the sixth surface, the radius of curvature of the sixth surface is R4, and at least one of the conditions (e) and (f) is satisfied:

[0016] (e) 200 mm ≤ R3 ≤ 500 mm;

[0017] (f) 30 mm ≤ R4 ≤ 60 mm.

[0018] In some embodiments, the refractive index of the third lens is 1.60 to 1.67, and the Abbe number of the third lens is 45 to 55.

[0019] In some embodiments, the central thickness of the first lens is T1, the central thickness of the second lens is T2, the central thickness of the third lens is T3, and at least one of the conditions (g), (h), and (i):

[0020] (g) 6.0 mm ≤ T1 ≤ 10.0 mm;

[0021] (h) 2.0 mm ≤ T2 ≤ 5.0 mm;

[0022] (i) 6.0 mm ≤ T3 ≤ 9.0 mm.

[0023] To solve the above technical problems, another technical solution adopted in the embodiments of the present utility model is: to provide a projection device, including the above projection lens.

[0024] The beneficial effects of the embodiments of the present utility model are: different from the prior art, in the embodiments of the present utility model, by arranging the second lens between the first lens and the third lens, arranging the Fresnel lens on the side of the first lens away from the second lens, and arranging the screen assembly on the side of the Fresnel lens away from the first lens, both the first lens and the third lens are positive lenses, the second lens is a negative lens, and the second lens is an aspherical lens. Compared with the prior art in which the lens is arranged in a spherical manner, the resolution of the projection lens is improved and the optical distortion of the lens is reduced, thereby improving the display effect of the image formed by the projection lens. Description of the Drawings

[0025] To more clearly illustrate the technical solutions in the specific embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. In all the drawings, similar elements or parts are generally denoted by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to actual scale.

[0026] Figure 1 It is a light ray trajectory diagram of the projection lens provided in the embodiments of the present utility model;

[0027] Figure 2 It is a structural schematic diagram of the projection lens provided in the embodiments of the present utility model;

[0028] Figure 3 It is a modulation transfer function curve diagram of the projection lens provided in the embodiments of the present utility model;

[0029] Figure 4 It is a distortion function curve diagram of the projection lens provided in the embodiments of the present utility model.

[0030] Reference Numerals in the Drawings

[0031] 100, projection lens;

[0032] 1, first lens;

[0033] 11, third surface;

[0034] 12, fourth surface;

[0035] 2, second lens;

[0036] 21, first surface;

[0037] 22. Second surface;

[0038] 3. Third lens;

[0039] 31. Fifth surface;

[0040] 32. Sixth surface;

[0041] 4. Fresnel lens;

[0042] 5. Screen assembly; Detailed implementation mode

[0043] For the convenience of understanding the present utility model, the present utility model will be described in more detail below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is expressed as "fixed to" another element, it can be directly on the other element, or there can be one or more intermediate elements therebetween. When an element is expressed as "connected to" another element, it can be directly connected to the other element, or there can be one or more intermediate elements therebetween. The terms "upper", "lower", "inner", "outer", "vertical", "horizontal", etc. used in this specification indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation of the present utility model. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0044] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the technical field to which the present utility model belongs. The terms used in the specification of the present utility model are only for the purpose of describing specific embodiments and are not used to limit the present utility model. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0045] In addition, the technical features involved in different embodiments of the present utility model described below can be combined with each other as long as they do not conflict with each other.

[0046] Existing projection lenses include multiple lenses, which converge, diverge, and correct the light emitted by the image source through the multiple lenses, so as to magnify the image source and form a display screen for the user to observe the formed screen. Most of the lenses of existing projection lenses adopt spherical lenses, resulting in low resolution of the projection lens and easy increase of optical distortion of the projection lens. Among them, the resolution is used to describe the ability of the optical system to restore the details of an object and can directly reflect the imaging ability and quality of the optical system. The higher the resolution of the optical system, the better the imaging quality. Optical distortion refers to the degree of distortion of the image formed by the optical system of an object relative to the object itself.

[0047] Based on this, the present application provides a projection lens and a projection device. By setting the second lens in the projection lens as an aspherical lens, the resolution of the projection lens can be increased, and the optical distortion of the projection lens can also be reduced, thereby improving the display effect of the screen formed by the projection lens.

[0048] Please refer to Figure 1 and Figure 2, the projection lens 100 includes: a first lens 1, a second lens 2, a third lens 3, a Fresnel lens 4, and a screen assembly 5. The first lens 1, the second lens 2, the third lens 3, the Fresnel lens 4, and the screen assembly 5 are arranged at intervals, and the centers of the first lens 1, the second lens 2, the third lens 3, the Fresnel lens 4, and the screen assembly 5 are located on the same straight line. The second lens 2 is located between the first lens 1 and the third lens 3. The Fresnel lens 4 is located on the side of the first lens 1 away from the second lens 2, and the screen assembly 5 is located on the side of the Fresnel lens 4 away from the first lens 1. Among them, both the first lens 1 and the third lens 3 are positive lenses, the second lens 2 is a negative lens, and the second lens 2 is an aspherical lens. It should be noted that a positive lens refers to a lens that is thin at the edge and thick in the middle, which can converge incident light, and a negative lens refers to a lens that is thick at the edge and thin in the middle, which can diverge incident light. The screen assembly 5 is used to emit light, and the Fresnel lens 4 is used to converge the light emitted by the screen assembly 5, so that the light emitted by the display device is concentrated and irradiated on the first lens 1. The first lens 1 is used to converge the light emitted from the Fresnel lens 4 again, and the second lens 2 is used to diverge the light emitted from the first lens 1 to achieve the purpose of magnifying the picture. The third lens 3 is used to converge the light emitted from the second lens 2 so that a display picture is formed at a preset position. In this embodiment, by arranging the Fresnel lens 4 between the screen assembly 5 and the first lens 1, the light emitted by the screen assembly 5 can be converged, and the brightness and uniformity of the light can be improved, and the quality of the display picture can be enhanced; by setting the second lens 2 as an aspherical lens, compared with a spherical lens, it can provide more degrees of freedom for the projection lens 100 to optimize the design, thereby improving the resolution of the projection lens 100 and reducing the optical distortion of the projection lens 100, and further enhancing the quality of the display picture formed by the projection lens 100.

[0049] It should be noted that in this application, a spherical surface refers to a standard spherical surface with a concave or convex surface. An aspherical surface refers to a surface whose concave or convex surface is not a standard spherical surface, but a surface composed of multiple spherical surfaces. Compared with a spherical surface, an aspherical surface has higher resolution and lower optical distortion.

[0050] For the above-mentioned first lens 1, please refer to Figure 2 , the surface of the first lens 1 facing the Fresnel lens 4 is the third surface 11. The third surface 11 can be a spherical surface, the radius of curvature of the third surface 11 is R1, and -80mm ≤ R1 ≤ -50mm is satisfied.

[0051] Furthermore, the radius of curvature R1 of the third surface 11 = -65.6mm.

[0052] It can be understood that the third surface 11 can also be set as a non-spherical surface. Setting the third surface 11 as a non-spherical surface can provide more degrees of freedom for the projection lens 100 to optimize the design, thereby further improving the resolution of the projection lens 100, reducing the optical distortion of the projection lens 100, and further improving the quality of the display image formed by the projection lens 100.

[0053] In some embodiments, referring to Figure 2 , the surface of the first lens 1 facing the second lens 2 is the fourth surface 12. The fourth surface 12 can be a spherical surface, the radius of curvature of the fourth surface 12 is R2, and 100 mm ≤ R2 ≤ 200 mm is satisfied.

[0054] Furthermore, the radius of curvature R2 of the fourth surface 12 = 151.4 mm.

[0055] It can be understood that the fourth surface 12 can also be set as a non-spherical surface, so as to provide more degrees of freedom for the projection lens 100 to optimize the design, thereby further improving the resolution of the projection lens 100, reducing the optical distortion of the projection lens 100, and further improving the quality of the display image formed by the projection lens 100.

[0056] In some embodiments, the refractive index of the first lens 1 is 1.65 - 1.70, and the Abbe number of the first lens 1 is 50 - 60.

[0057] Furthermore, the refractive index of the first lens 1 is 1.69, and the Abbe number of the first lens 1 is 55.5.

[0058] For the above-mentioned second lens 2, referring to Figure 2 , the surface of the second lens 2 facing the first lens 1 is the first surface 21. The first surface 21 is a non-spherical surface, the conic coefficient of the first surface 21 is K1, and 0.14 ≤ K1 ≤ 0.16 is satisfied. The conic coefficient is used to describe the similarity between the aspherical surface shape and a cone. The larger the conic coefficient, the more similar the aspherical surface shape is to the cone shape. The smaller the conic coefficient, the greater the difficulty, the lower the processing efficiency, and it is also difficult to guarantee the quality of the aspherical surface shape. Therefore, in this embodiment, by selecting the conic coefficient K1 of the first surface 21 to satisfy 0.14 ≤ K1 ≤ 0.16, the processing difficulty and the resolution of the projection lens 100 can be taken into account.

[0059] Furthermore, the conic coefficient K1 of the first surface 21 = 0.16.

[0060] In some embodiments, the fourth-order coefficient of the first surface 21 is 6.3*E -7 , the sixth-order coefficient is -2.0*E -7 , the eighth-order coefficient is 2.2*E -12。

[0061] In some embodiments, referring to Figure 2 , the surface of the second lens 2 facing the third lens 3 is the second surface 22, the second surface 22 is an aspherical surface, the conic coefficient of the second surface 22 is K2, and -0.046 ≤ K2 ≤ -0.042 is satisfied, so that the processing difficulty and the resolution of the projection lens 100 can be taken into account.

[0062] Furthermore, the conic coefficient K2 of the second surface 22 = -0.044.

[0063] In some embodiments, the fourth-order coefficient of the second surface 22 is 1.52*E -7 , the sixth-order coefficient is 9.1*E -10 , and the eighth-order coefficient is -7.8*E -13 。

[0064] In some embodiments, the second lens 2 is made of polycarbonate. Most of the existing lenses are made of glass. Glass can only be processed into a spherical surface by cold working, that is, a spherical surface is formed through processes such as grinding. For the processing of an aspherical surface, by using the cold working method, the processing difficulty is relatively large, and the shape quality of the processed aspherical surface is difficult to guarantee. Therefore, in this embodiment, the second lens 2 is made of polycarbonate. During the manufacturing process, mold injection molding can be used, which can improve production efficiency and the shape quality of the processed aspherical surface.

[0065] In some embodiments, the refractive index of the second lens 2 is 1.5 to 1.65, and the Abbe number of the second lens 2 is 25 to 35.

[0066] Furthermore, the refractive index of the second lens 2 is 1.59, and the Abbe number of the second lens 2 is 29.9.

[0067] For the above-mentioned third lens 3, referring to Figure 2 , the surface of the third lens 3 facing the second lens 2 is the fifth surface 31. The fifth surface 31 can be a spherical surface, the curvature radius of the fifth surface 31 is R3, and 200 mm ≤ R3 ≤ 500 mm is satisfied.

[0068] Furthermore, the curvature radius R3 of the fifth surface 31 = 374.6 mm.

[0069] In some embodiments, the fifth surface 31 can also be set as an aspherical surface, so as to further improve the resolution of the projection lens 100, reduce optical distortion, and further improve the quality of the display picture formed by the projection lens 100.

[0070] In some embodiments, referring to Figure 2The surface of the third lens 3 facing away from the second lens 2 is the sixth surface 32. The sixth surface 32 can be a spherical surface. The radius of curvature of the sixth surface 32 is R4, and 30 mm ≤ R4 ≤ 60 mm is satisfied.

[0071] Furthermore, the radius of curvature R3 of the sixth surface 32 is 45.6 mm.

[0072] In some embodiments, the sixth surface 32 can also be set as an aspherical surface, so as to further improve the resolution of the projection lens 100, reduce optical distortion, and further improve the quality of the display picture formed by the projection lens 100.

[0073] In some embodiments, the refractive index of the third lens 3 is 1.60 - 1.67, and the Abbe number of the third lens 3 is 45 - 55.

[0074] Furthermore, the refractive index of the third lens 3 is 1.65, and the Abbe number of the third lens 3 is 50.8.

[0075] The refractive index is the ratio of the propagation speed of light in a vacuum to the propagation speed of light in the medium. The higher the refractive index, the stronger the ability to refract incident light. The Abbe number is used to measure the degree of chromatic dispersion of the lens. The greater the refractive index of the medium, the more serious the chromatic dispersion, and the smaller the Abbe number; conversely, the smaller the refractive index of the medium, the milder the chromatic dispersion, and the greater the Abbe number. Therefore, when selecting the first lens 1, the second lens 2, and the third lens 3, it is necessary to balance the refractive index and Abbe number of each lens, so that the projection lens 100 has a smaller chromatic dispersion while achieving a magnified display picture. Therefore, the refractive index of the first lens 1 is selected to be 1.65 - 1.70, and the Abbe number is selected to be 50 - 60; the refractive index of the second lens 2 is selected to be 1.5 - 1.65, and the Abbe number is selected to be 25 - 35. Selecting the refractive index of the third lens 3 to be 1.60 - 1.67 and the Abbe number to be 45 - 55 can make the projection lens 100 have a smaller chromatic dispersion while achieving a magnified display picture.

[0076] In some embodiments, please refer to Figure 2 The central thickness of the first lens 1 is T1, and 6.0 mm ≤ T1 ≤ 10.0 mm is satisfied. Herein, the central thickness of the first lens 1 refers to the distance between the most convex point of the third surface 11 and the most convex point of the fourth surface 12. When the central thickness T1 of the first lens 1 is small, the requirement for converging light cannot be met. When the central thickness T1 of the first lens 1 is large, it will cause the volume of the projection lens 100 to be too large. Therefore, the central thickness T1 of the first lens 1 is selected to satisfy 6.0 mm ≤ T1 ≤ 10.0 mm.

[0077] Furthermore, the central thickness T1 of the first lens 1 is 8.2 mm.

[0078] In some embodiments, the central thickness of the second lens 2 is T2, and 2.0 mm ≤ T2 ≤ 5.0 mm is satisfied, where the central thickness of the second lens 2 refers to the distance between the deepest point of the first surface 21 and the deepest point of the second surface 22. When the central thickness T2 of the second lens 2 is small, the requirement for light divergence cannot be met. When the central thickness T2 of the second lens 2 is large, it will cause the volume of the projection lens 100 to be too large. Therefore, the central thickness T2 of the second lens 2 is selected to satisfy 2.0 mm ≤ T2 ≤ 5.0 mm.

[0079] Further, the central thickness T2 of the second lens 2 = 3.0 mm.

[0080] In some embodiments, the central thickness of the third lens 3 is T3, and 6.0 mm ≤ T3 ≤ 9.0 mm is satisfied, where the central thickness of the third lens 3 refers to the distance between the most convex point of the fifth surface 31 and the most convex point of the sixth surface 32. When the central thickness T3 of the third lens 3 is small, the requirement for light convergence cannot be met. When the central thickness T3 of the third lens 3 is large, it will cause the volume of the projection lens 100 to be too large. Therefore, the central thickness T3 of the third lens 3 is selected within the above range.

[0081] Further, the central thickness T3 of the third lens 3 = 8.2 mm.

[0082] In some embodiments, the surface of the Fresnel lens 4 facing the first lens 1 is a plane, the surface of the Fresnel lens 4 facing the screen assembly 5 is a Fresnel surface, and the annular serrated structure of the Fresnel surface is an equal-width design or an equal-depth design.

[0083] In some embodiments, please refer to Figure 2 , the central thickness of the Fresnel lens 4 is 1.8 mm.

[0084] In some embodiments, please refer to Figure 2 , the distance between the Fresnel lens 4 and the screen assembly 5 is D1, and 9 mm ≤ D1 ≤ 11 mm is satisfied. When D1 is small, the distance between the Fresnel lens 4 and the screen assembly 5 is small, and the light emitted by the screen assembly 5 is converged by the Fresnel lens 4 before it is fully diffused, which easily causes the projection lens 100 to be unable to form an enlarged display image at the preset position; if D1 is large, the distance between the Fresnel lens 4 and the screen assembly 5 is large, and the light emitted by the screen assembly 5 is severely diffused, and a larger area of the Fresnel lens 4 needs to be set to converge all the light. Therefore, selecting the distance D1 between the Fresnel lens 4 and the screen assembly 5 to satisfy 9 mm ≤ D1 ≤ 11 mm can save the area of the Fresnel lens 4 and form a display image at the preset position.

[0085] Further, the distance D1 between the Fresnel lens 4 and the screen assembly 5 = 10 mm.

[0086] In some embodiments, the central distance between the Fresnel lens 4 and the first lens 1 is D2, and 70 mm ≤ D2 ≤ 80 mm is satisfied. Herein, the central distance between the Fresnel lens 4 and the first lens 1 refers to the distance between the Fresnel lens 4 and the most convex point of the third surface 11 of the first lens 1. When D2 is relatively small, the distance between the Fresnel lens 4 and the first lens 1 is relatively small, and then the first lens 1 needs to have a larger diameter to converge all the light passing through the Fresnel lens 4; when D2 is relatively large, the distance between the Fresnel lens 4 and the first lens 1 is relatively large, which will also cause the projection lens 100 to be unable to form a display picture at the preset position. Therefore, it is necessary to make the distance between the Fresnel lens 4 and the first lens 1 satisfy 70 mm ≤ D2 ≤ 80 mm.

[0087] Furthermore, the central distance D2 between the Fresnel lens 4 and the first lens 1 is 75.6 mm.

[0088] In some embodiments, the central distance between the first lens 1 and the second lens 2 is D3, and 7 mm ≤ D3 ≤ 9 mm is satisfied. Herein, the central distance between the first lens 1 and the second lens 2 is the distance between the most convex point of the fourth surface 12 of the first lens 1 and the most concave point of the first surface 21 of the second lens 2. If the distance between the first lens 1 and the second lens 2 is relatively close, then it is necessary to increase the diameter of the second lens 2 to receive all the light; if the distance between the first lens 1 and the second lens 2 is relatively far, it is difficult for the projection lens 100 to form a display picture at the preset position. Therefore, it is necessary to make the distance between the first lens 1 and the second lens 2 satisfy 7 mm ≤ D2 ≤ 9 mm.

[0089] Furthermore, the central distance D3 between the first lens 1 and the second lens 2 is 8.2 mm.

[0090] In some embodiments, the central distance between the second lens 2 and the third lens 3 is D4, and 10 mm ≤ D4 ≤ 12 mm is satisfied. Herein, the central distance between the second lens 2 and the third lens 3 is the distance between the most concave point of the second surface 22 of the second lens 2 and the most convex point of the fifth surface 31 of the third lens 3. When D4 is relatively small, the distance between the second lens 2 and the third lens 3 is relatively small, and then the third lens 3 needs to have a larger diameter to converge all the light diverged by the second lens 2; when D4 is relatively large, the distance between the second lens 2 and the third lens 3 is relatively large, which will also cause the projection lens 100 to be unable to form a display picture at the preset position. Therefore, it is necessary to make the distance between the second lens 2 and the third lens 3 satisfy 10 mm ≤ D4 ≤ 12 mm.

[0091] Furthermore, the central distance D4 between the second lens 2 and the third lens 3 is 10.8 mm.

[0092] In some embodiments, the diameter of the first lens 1 is 40 mm, the diameter of the second lens 2 is 37 mm, and the diameter of the third lens 3 is 46 mm.

[0093] In some embodiments, the contour of the Fresnel lens 4 is rectangular, and its size is 89 mm * 52 mm.

[0094] In some embodiments, the first lens 1 and the third lens 3 are made of glass.

[0095] In some embodiments, the Fresnel lens 4 is made of polymethyl methacrylate.

[0096] In some embodiments, the screen assembly 5 is a 3.5-inch LCD liquid crystal screen, and its resolution is 1920 * 1080.

[0097] In the embodiments of the present invention, by reasonably setting the refractive index, Abbe number, thickness, and spacing of the Fresnel lens 4, the first lens 1, the second lens 2, and the third lens 3, after the light passes through different degrees of convergence and divergence, various aberrations in the projection device can be effectively corrected, the resolution of the projection lens 100 can be improved, and the optical distortion can be reduced, thereby improving the display quality of the display screen. Moreover, a projection ratio of 1.25 can be achieved, meeting the requirements of miniaturization and large screen of the projection device.

[0098] To enable readers to better understand the concept of this application, experimental verification is carried out below.

[0099] Table 1 shows some parameters of the first lens 1, the second lens 2, and the third lens 3 in the projection lens 100 used in the experiment. Among them, the conic coefficient K1 of the first surface 21 is 0.16, the conic coefficient K2 of the second surface 22 is -0.044, the distance D1 between the screen assembly 5 and the Fresnel lens 4 is 10 mm, the center distance D2 between the Fresnel lens 4 and the first lens 1 is 75.6 mm, the center distance D3 between the first lens 1 and the second lens 2 is 8.2 mm, the center distance D4 between the second lens 2 and the third lens 3 is 10.8 mm, the screen assembly 5 is a 3.5-inch LCD liquid crystal screen, its resolution is 1920 * 1080, the pixel size is 45 microns, and the corresponding spatial resolution is 12.3 lp / mm.

[0100] Table 1

[0101]

[0102]

[0103] Through the above parameter limitations, the Figure 3 modulation transfer function curve in andFigure 4 The distortion curve in it. The Modulation Transfer Function (MTF) reflects the resolving power of an optical system, is used to evaluate the imaging quality of the optical system, and can reflect the ability of the optical system to restore object details. Distortion is the phenomenon that light rays become bent after passing through a lens. Distortion is caused by the change in the magnification of the lens with the angle between the light ray and the optical axis. The farther the light ray is from the optical axis, the greater the distortion. The distortion can be reduced by optimizing the surface shape and curvature of the lens.

[0104] Please refer to Figure 3 , measure the MTF curves in the meridional direction and sagittal direction of the projection lens 100 with field angles of 0 degrees, 7.2 degrees, 12 degrees, 16.8 degrees, 20.4 degrees, and 24 degrees respectively. Among them, the meridional direction refers to the direction of the plane extended by the chief ray of an off-axis object point and the main axis of the projection lens 100, and the sagittal direction refers to the direction of the plane extended by the chief ray passing through the off-axis object point and perpendicular to the meridional plane. In Figure 3 , the abscissa is the spatial resolution, with the unit of line pairs per millimeter (lp / mm), and the ordinate is the corresponding MTF value. The larger the spatial resolution, the larger the corresponding MTF value, indicating that the resolving power of the optical system is higher and the imaging quality is better.

[0105] Please refer to Figure 3 , L1 represents the MTF curve in the meridional direction when the field angle is 24 degrees, L2 represents the MTF curve in the sagittal direction when the field angle is 24 degrees, L3 represents the MTF curve in the meridional direction when the field angle is 20.4 degrees, L4 represents the MTF curve in the sagittal direction when the field angle is 20.4 degrees, L5 represents the MTF curve in the meridional direction when the field angle is 16.8 degrees, L6 represents the MTF curve in the sagittal direction when the field angle is 16.8 degrees, L7 represents the MTF curve in the meridional direction when the field angle is 12 degrees, L8 represents the MTF curve in the meridional direction when the field angle is 7.2 degrees, L9 represents the MTF curve in the sagittal direction when the field angle is 7.2 degrees, L10 represents the MTF curve in the meridional direction when the field angle is 0 degrees. The MTF curve in the sagittal direction when the field angle is 0 degrees coincides with the MTF curve in the meridional direction when the field angle is 0 degrees, and the MTF curve in the sagittal direction when the field angle is 12 degrees coincides with the MTF curve in the sagittal direction when the field angle is 20.4 degrees. It can be seen from Figure 3 that the MTF values of the projection lens 100 provided by the present application in the meridional direction and sagittal direction at a spatial resolution of 12.3 lp / mm are both greater than 0.3, having a high resolving power.

[0106] Please refer to Figure 4, the abscissa represents the magnitude of distortion, the ordinate represents the magnitude of the field of view, L11 represents the distortion reference line, and L12 represents the optical distortion curve of the projection lens 100. Among them, the optical distortion curves of red, green, and blue light roughly coincide. From Figure 4 it can be seen that the optical distortion of the projection lens 100 is less than 0.5%, having a small optical distortion.

[0107] The present utility model further provides an embodiment of a projection device. The projection device includes the above-mentioned projection lens 100. For the specific structure and function of the projection lens 100, reference can be made to the above embodiment, and details will not be repeated here.

[0108] The above are only embodiments of the present utility model, and do not limit the patent scope of the present utility model. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present utility model, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present utility model.

Claims

1. A projection lens, characterized in that, It includes a first lens, a second lens, a third lens, a Fresnel lens, and a screen assembly. The centers of the first lens, the second lens, the third lens, the Fresnel lens, and the screen assembly are located on the same straight line. The second lens is located between the first lens and the third lens. The Fresnel lens is located on the side of the first lens away from the second lens. The screen assembly is arranged on the side of the Fresnel lens away from the first lens. The light emitted by the screen assembly passes through the Fresnel lens, the first lens, the second lens, and the third lens in sequence and is emitted to a preset position. Among them, both the first lens and the third lens are positive lenses, the second lens is a negative lens, and the second lens is an aspherical lens.

2. The projection lens according to claim 1, wherein the second lens is made of polycarbonate.

3. The projection lens according to claim 2, wherein the surface of the second lens facing the first lens is the first surface, the conic coefficient of the first surface is K1, the surface of the second lens facing the third lens is the second surface, the conic coefficient of the second surface is K2, and at least one of the conditions (a) and (b) is satisfied: (a) 0.14 ≤ K1 ≤ 0.16; (b) -0.046 ≤ K2 ≤ -0.

042.

4. The projection lens according to claim 1, wherein the refractive index of the second lens is 1.5 to 1.65, and the Abbe number of the second lens is 25 to 35.

5. The projection lens according to claim 1, wherein the surface of the first lens facing the Fresnel lens is the third surface, the curvature radius of the third surface is R1, the surface of the first lens facing the second lens is the fourth surface, the curvature radius of the fourth surface is R2, and at least one of the conditions (c) and (d) is satisfied: (c) -80 mm ≤ R1 ≤ -50 mm; (d) 100 mm ≤ R2 ≤ 200 mm.

6. The projection lens according to claim 1, wherein the refractive index of the first lens is 1.65 to 1.70, and the Abbe number of the first lens is 50 to 60.

7. The projection lens according to claim 1, wherein the surface of the third lens facing the second lens is the fifth surface, the surface curvature radius of the fifth surface is R3, the surface of the third lens away from the second lens is the sixth surface, the surface curvature radius of the sixth surface is R4, and at least one of the conditions (e) and (f) is satisfied: (e) 200 mm ≤ R3 ≤ 500 mm; (f) 30 mm ≤ R4 ≤ 60 mm.

8. The projection lens according to claim 1, wherein the refractive index of the third lens is 1.60 to 1.67, and the Abbe number of the third lens is 45 to 55.

9. The projection lens according to claim 1, wherein The central thickness of the first lens is T1, the central thickness of the second lens is T2, the central thickness of the third lens is T3, and at least one of the conditions (g), (h), (i): (g) 6.0 mm ≤ T1 ≤ 10.0 mm; (h) 2.0 mm ≤ T2 ≤ 5.0 mm; (i) 6.0 mm ≤ T3 ≤ 9.0 mm.

10. A projection device, characterized in that, Comprising a projection lens according to any one of claims 1-9.

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