Lens module and projector

Abstract

The invention provides a lens module and a projector, and the lens module comprises a first lens, a second lens, a third lens and a fourth lens. The first lens meets the conditions that the incident surface is a convex surface and the curvature radius of the incident surface is R1, and the emergent surface is a concave surface and the curvature radius of the emergent surface is R2; the second lens satisfies the following conditions: the incident surface is a convex surface and the curvature radius of the incident surface is R3, and the emergent surface is a convex surface and the curvature radius of the emergent surface is R4; the third lens meets the following conditions: the light-in surface is a concave surface and the curvature radius of the light-in surface is R5, and the light-out surface is a concave surface and the curvature radius of the light-out surface is R6; the fourth lens satisfies that the light-in surface is a concave surface and the curvature radius of the light-in surface is R7, and the light-out surface is a convex surface and the curvature radius of the light-out surface is R8. The first lens, the second lens, the third lens and the fourth lens meet the following conditional expressions: R1 is greater than R2, R3 is less than R4, R5 is less than R6, and R7 is greater than R8; r7 > R1 > R5 > R3, and R6 > R4 > R8 > R2. The lens module provided by the invention has relatively good resolving power.

Description

Technical Field

[0001] This application relates to the field of projection technology, and particularly to a lens module and a projector. Background Art

[0002] With the continuous development of LCD projection technology, the size of the LCD light valve has been continuously reduced and the resolution has been continuously improved, which has put forward higher requirements for the resolution of the lens module to achieve a higher-definition projection image. However, the resolution of existing lens modules is relatively low and cannot meet the high-definition projection requirements of small-size LCD light valves. Summary of the Invention

[0003] An embodiment of this application provides a lens module with good resolution.

[0004] To achieve the above object, the lens module proposed in this application includes a first lens, a second lens, a third lens, and a fourth lens that are coaxial and arranged in sequence. The first lens satisfies: the incident surface is convex and the radius of curvature of the incident surface is R1, the exit surface is concave and the radius of curvature of the exit surface is R2; the second lens satisfies: the incident surface is convex and the radius of curvature of the incident surface is R3, the exit surface is convex and the radius of curvature of the exit surface is R4; the third lens satisfies: the incident surface is concave and the radius of curvature of the incident surface is R5, the exit surface is concave and the radius of curvature of the exit surface is R6; the fourth lens satisfies: the incident surface is concave and the radius of curvature of the incident surface is R7, the exit surface is convex and the radius of curvature of the exit surface is R8.

[0005] The first lens, the second lens, the third lens, and the fourth lens satisfy the following conditional equations:

[0006] R1 > R2, R3 < R4, R5 < R6, R7 > R8;

[0007] R7 > R1 > R5 > R3, R6 > R4 > R8 > R2.

[0008] Optionally, in one embodiment, the range of R1 is 33.981 mm - 40.152 mm; the range of R2 is 23.579 mm - 28.251 mm; the range of R3 is 25.337 mm - 28.141 mm; the range of R4 is 41.256 mm - 48.530 mm; the range of R5 is 28.971 mm - 32.115 mm; the range of R6 is 45.597 mm - 52.818 mm; the range of R7 is 57.248 mm - 62.596 mm; the range of R8 is 27.222 mm - 33.554 mm.

[0009] Optionally, in one embodiment, R1 is 38.977 mm, R2 is 25.221 mm; R3 is 27.337 mm, R4 is 47.939 mm; R5 is 29.541 mm, R6 is 50.815 mm; R7 is 61.932 mm, R8 is 29.347 mm.

[0010] Optionally, in one embodiment, the distance between the first lens and the second lens is L1; the distance between the second lens and the third lens is L2; the distance between the third lens and the fourth lens is L3; the first lens, the second lens, the third lens, and the fourth lens satisfy the following conditional formula: L3 > L2 > L1.

[0011] Optionally, in one embodiment, the magnitudes of L1, L2, and L3 are all adjustable.

[0012] Optionally, in one embodiment, the range of L1 is: 0.2 mm - 0.35 mm; the range of L2 is: 1.3 mm - 1.8 mm; the range of L3 is: 7 mm - 11 mm.

[0013] Optionally, in one embodiment, the range of L1 is 0.2725 mm - 0.2734 mm, the range of L2 is 1.505 mm - 1.515 mm, and the range of L3 is 9.181 mm - 9.191 mm.

[0014] Optionally, in one embodiment, 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 the central thickness of the fourth lens is T4; the first lens, the second lens, the third lens, and the fourth lens also satisfy the following conditional formula: T4 > T2 > T1 = T3.

[0015] Optionally, in one embodiment, the range of T1 is 2.856 mm - 3.219 mm; the range of T2 is 3.78 mm - 4.96 mm; the range of T3 is 2.97 mm - 4.15 mm; the range of T4 is 4.45 mm - 5.37 mm.

[0016] Optionally, in one embodiment, T1 is 3.12 mm, T2 is 4.7 mm, T3 is 3.12 mm, and T4 is 5 mm.

[0017] Optionally, in one embodiment, the refractive index of the first lens is N1, the refractive index of the second lens is N2, the refractive index of the third lens is N3, and the refractive index of the fourth lens is N4; the first lens, the second lens, the third lens, and the fourth lens further satisfy the following conditional formula: N1 > N2 > N4 > N3.

[0018] Optionally, in one embodiment, the range of N1 is 1.75 - 1.85; the range of N2 is 1.75 - 1.85; the range of N3 is 1.55 - 1.65; the range of N4 is 1.75 - 1.85.

[0019] Optionally, in one embodiment, N1 is 1.8467, N2 is 1.804, N3 is 1.6201, and N4 is 1.7725.

[0020] Optionally, in one embodiment, the Abbe number of the first lens is 23.784; the Abbe number of the second lens is 46.574; the Abbe number of the third lens is 36.346; the Abbe number of the fourth lens is 49.599.

[0021] Optionally, in one embodiment, the first lens further satisfies: the aperture of the incident light surface is D1 and the range of D1 is 21 mm - 26 mm, the aperture of the emergent light surface is D2 and the range of D2 is 18 mm - 23 mm; the second lens further satisfies: the aperture of the incident light surface is D3 and the range of D3 is 18 mm - 23 mm, the aperture of the emergent light surface is D4 and the range of D4 is 18 mm - 23 mm; the third lens further satisfies: the aperture of the incident light surface is D5 and the range of D5 is 15 mm - 20 mm, the aperture of the emergent light surface is D6 and the range of D6 is 18 mm - 23 mm; the fourth lens further satisfies: the aperture range of the incident light surface is D7 and D7 is 29.6 mm - 34.6 mm, the aperture of the emergent light surface is D8 and the range of D8 is 32 mm - 37 mm.

[0022] Optionally, in one embodiment, D1 is 22 mm, D2 is 19 mm, both D3 and D4 are 19 mm; D5 is 16 mm, D6 is 19 mm; D7 is 30.6 mm, D8 is 33 mm.

[0023] This application also provides a projector, which includes a light valve and the lens module according to any one of the above embodiments, and the light valve is located on one side where the incident light surface of the first lens is located.

[0024] Optionally, in one embodiment, the distance between the light valve and the first lens is not less than 48 mm.

[0025] Optionally, in one embodiment, a Fresnel lens is further provided between the light valve and the first lens, and the distance between the Fresnel lens and the light valve ranges from 6 mm to 12 mm.

[0026] Optionally, in one embodiment, the equivalent focal length of the Fresnel lens ranges from 50 mm to 55 mm.

[0027] The lens module provided by this application has good resolution. Description of the Drawings

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0029] Figure 1 It is a schematic structural diagram of one embodiment of the lens module of this application;

[0030] Figure 2 It is a schematic structural diagram of another embodiment of the lens module of this application

[0031] Figure 3 It is a schematic structural diagram of one embodiment of the projector of this application.

[0032] Figure 4 It is the MTF curve graph of the lens module of this application;

[0033] Figure 5 It is the vertical chromatic aberration curve graph of the lens module of this application;

[0034] Figure 6 It is the optical distortion of the lens module of this application.

[0035] Explanation of the reference numerals in the drawings: 100, lens module; 10, first lens; 20, second lens; 30, third lens; 40, fourth lens; 200, projector; 50, light valve; 60, Fresnel lens; Z, optical axis.

[0036] The realization of the purpose, functional features and advantages of this application will be further described in combination with the embodiments and with reference to the drawings. Detailed Embodiments

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0038] An embodiment of the present application provides a lens module to solve the problem that the resolution of the existing lens module is relatively low and cannot meet the high-definition projection requirements of a small-size LCD light valve. The following will be described with reference to the accompanying drawings.

[0039] In the embodiment of the present application, as Figure 1 shown, the lens module 100 includes a first lens 10, a second lens 20, a third lens 30, and a fourth lens 40 that are coaxial and arranged in sequence. Specifically, the optical axes Z of the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 coincide with each other. And in practical applications, the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 are arranged in sequence along the light propagation direction. For example, as Figure 2 shown, when the lens module 100 is applied to a projector 200, the first lens 10 is closest to the light valve 50, and the fourth lens 40 is farthest from the light valve 50.

[0040] Each of the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 has an incident surface and an exit surface that are opposite to each other. The incident surface is the surface where light enters the lens, and the exit surface is the surface where light leaves the lens. As Figure 1 shown, to more clearly illustrate the technical solution of the present application, the incident surface of the first lens 10 is denoted as S1, and the exit surface of the first lens 10 is denoted as S2; the incident surface of the second lens 20 is denoted as S3, and the exit surface of the second lens 20 is denoted as S4; the incident surface of the third lens 30 is denoted as S5, and the exit surface of the third lens 30 is denoted as S6; the incident surface of the fourth lens 40 is denoted as S7, and the exit surface of the fourth lens 40 is denoted as S8.

[0041] In the present application, as Figure 1 shown, the first lens satisfies that the incident surface S1 is a convex surface and the curvature radius of the incident surface S1 is R1, and the exit surface S2 is a concave surface and the curvature radius of the exit surface S2 is R2.

[0042] The second lens satisfies that the incident surface S3 is a convex surface and the curvature radius of the incident surface S3 is R3, and the exit surface S4 is a convex surface and the curvature radius of the exit surface S4 is R4.

[0043] The third lens satisfies that the incident surface S5 is a concave surface and the curvature radius of the incident surface S5 is R5, and the exit surface S6 is a concave surface and the curvature radius of the exit surface S6 is R6.

[0044] The fourth lens satisfies that the incident light surface S7 is concave with a radius of curvature of R7, and the outgoing light surface S8 is convex with a radius of curvature of R8.

[0045] The first lens, the second lens, the third lens, and the fourth lens satisfy the following conditional formula one:

[0046] R1 > R2, R3 < R4, R5 < R6, R7 > R8;

[0047] R7 > R1 > R5 > R3, R6 > R4 > R8 > R2.

[0048] As Figures 4 to 6 shown, Figure 4 is the MTF curve graph of the lens module 100, Figure 5 is the lateral chromatic aberration curve graph of the lens module 100, Figure 6 is the optical distortion graph of the lens module 100. By controlling the radii of curvature of the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 to satisfy the above conditional formula one, the modulation degree of the MTF value (MoTulation Transfer Function) of the lens module 100 at 20 lp / mm can be made greater than 0.33 (that is, the contrast and resolution of the lens are relatively high), the lateral chromatic aberration < 3 microns, and the optical distortion < 0.4%, which means that the lens module 100 has good resolving power.

[0049] Among them, in one embodiment, the range of R1 is 33.981 mm - 40.152 mm. For example, R1 can be 33.981 mm, 34.977 mm, 35.932 mm, 36.152 mm, 37.347 mm, 38.977 mm, 39.815 mm, 40.152 mm, and so on.

[0050] The range of R2 is 23.579 mm - 28.251 mm. For example, R2 can be 23.579 mm, 24.681 mm, 25.221 mm, 26.813 mm, 27.724 mm, 28.251 mm, and so on.

[0051] The range of R3 is 25.337 mm - 28.141 mm. For example, R3 can be 25.337 mm, 25.645 mm, 26.268 mm, 26.952 mm, 27.337 mm, 27.629 mm, 27.994 mm, 28.141 mm, and so on. The range of R4 is 41.256 mm - 48.530 mm. For example, R4 can be 41.256 mm, 42.678 mm, 43.216 mm, 44.357 mm, 465.598 mm, 46.485 mm, 47.939 mm, 48.530 mm, and so on.

[0052] The range of R5 is 28.971 mm - 32.115 mm. For example, R5 can be 28.971 mm, 28.066 mm, 28.734 mm, 29.032 mm, 29.541 mm, 29.569 mm, 30.485 mm, 31.785 mm, 32.115 mm, and so on.

[0053] The range of R6 is 45.597 mm - 52.818 mm. For example, R6 can be 45.597 mm, 46.842 mm, 47.265 mm, 48.156 mm, 49.426 mm, 50.815 mm, 51.947 mm, 52.068 mm, 52.818 mm, and so on.

[0054] The range of R7 is 57.248 mm - 62.596 mm. For example, R7 can be 57.248 mm, 58.485 mm, 59.652 mm, 60.143 mm, 60.866 mm, 61.355 mm, 61.932 mm, 62.115 mm, 62.596 mm, and so on.

[0055] The range of R8 is 27.222 mm - 33.554 mm. For example, R8 can be 27.222 mm, 27.964 mm, 28.644 mm, 29.374 mm, 29.875 mm, 30.815 mm, 31.947 mm, 32.068 mm, 33.554 mm, and so on.

[0056] It can be understood that if the curvature radius of the lens is too small, it will cause serious light scattering and aberration. If the curvature radius of the lens is too large, it will result in weak focusing ability of the lens for light, and thus poor resolution. Therefore, on the basis of making R1 to R8 satisfy the above conditional formula (1), by respectively controlling R1 to R8 within the ranges listed above, it can not only avoid serious light scattering and aberration, but also ensure that the lens module 100 has good focusing ability for light, and thus the lens module 100 has good resolution.

[0057] More specifically, in one embodiment, R1 is 38.977 mm, R2 is 25.221 m, R3 is 27.337 mm, R4 is 47.939 mm, R5 is 293541 mm, R6 is 50.815 mm, R7 is 61.932 mm, and R8 is 29.347 mm. As Figures 4 to 6 shown, when R1 to R8 take the above values respectively, the modulation transfer function (MTF) value of the lens module 100 at 20 lp / mm can have a modulation greater than 0.33, the lateral chromatic aberration < 3 microns, and the optical distortion < 0.4%, that is, the lens module 100 has good resolution.

[0058] Optionally, in one embodiment, as Figure 2 shown, the distance between the first lens 10 and the second lens 20 is L1, the distance between the second lens 20 and the third lens 30 is L2, and the distance between the third lens 30 and the fourth lens 40 is L3; the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 satisfy the following conditional formula two: L3 > L2 > L1.

[0059] It should be noted here that the "distance" between lenses refers to the width of the air gap at the position of the optical axis Z between the lenses, and reference can be made to Figure 2 , and the extension length of the optical axis Z between two adjacent lenses is the distance between the two adjacent lenses.

[0060] As Figures 4 to 6 shown, by controlling the distances between the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 to satisfy the above conditional formula two, the MTF value of the lens module 100 at 20 lp / mm can have a modulation greater than 0.33, the lateral chromatic aberration < 3 microns, and the optical distortion < 0.4%, that is, the lens module 100 has good resolution.

[0061] Optionally, in one embodiment, the magnitudes of L1, L2, and L3 are all adjustable. Specifically, after the first lens, the second lens, the third lens, and the fourth lens are assembled into a lens module, any one of the first lens, the second lens, the third lens, and the fourth lens can continue to be adjusted at the installation position. For example, the first lens, the second lens, the third lens, and the fourth lens are all slidably mounted along the optical axis Z, and thus the magnitudes of L1, L2, or L3 can be adjusted by sliding the lenses. Alternatively, multiple slots are preset on the installation housing of the lens module corresponding to each lens, and each lens can choose to be installed in one of the corresponding multiple slots according to the actual situation, that is, the magnitudes of L1, L2, or L3 can be adjusted by adjusting the installation slots of each lens. It should be noted that after the magnitudes of L1, L2, or L3 are adjusted, they still need to satisfy the conditional formula two, that is, L3 > L2 > L1.

[0062] Specifically, in one embodiment, the range of L1 is 0.2 mm - 0.35 mm. For example, the specific range of L1 can be 0.2 mm - 0.35 mm, 0.2 mm - 0.33 mm, 0.2 mm - 0.32 mm, 0.2 mm - 0.3 mm, 0.2 mm - 0.28 mm, 0.2 mm - 0.25 mm, 0.2 mm - 0.22 mm. Within the above ranges, the specific range of L1 can also be 0.22 mm - 0.35 mm, 0.22 mm - 0.33 mm, 0.22 mm - 0.32 mm, 0.22 mm - 0.3 mm, 0.22 mm - 0.28 mm, 0.22 mm - 0.26 mm, 0.22 mm - 0.25 mm. Within the above ranges, the specific range of L1 can also be 0.25 mm - 0.35 mm, 0.25 mm - 0.33 mm, 0.25 mm - 0.32 mm, 0.25 mm - 0.3 mm, 0.25 mm - 0.28 mm, 0.25 mm - 0.27 mm. Within the above ranges, the specific range of L1 can also be 0.27 mm - 0.35 mm, 0.27 mm - 0.33 mm, 0.27 mm - 0.32 mm, 0.27 mm - 0.31 mm, 0.27 mm - 0.28 mm. Among them, the actual value of L1 can be 0.2 mm, 0.22 mm, 0.25 mm, 0.273 mm, 0.286 mm, 0.313 mm, 0.33 mm, 0.35 mm, etc.

[0063] The range of L2 is 1.3 mm - 1.8 mm. For example, the specific range of L2 can be 1.3 mm - 1.8 mm, 1.3 mm - 1.75 mm, 1.3 mm - 1.7 mm, 1.3 mm - 1.65 mm, 1.3 mm - 1.6 mm, 1.3 mm - 1.5 mm, 1.3 mm - 1.45 mm, 1.3 mm - 1.4 mm. Within the above ranges, the specific range of L2 can also be 1.4 mm - 1.8 mm, 1.4 mm - 1.75 mm, 1.4 mm - 1.7 mm, 1.4 mm - 1.65 mm, 1.4 mm - 1.6 mm. Within the above ranges, the specific range of L2 can also be 1.45 mm - 1.8 mm, 1.45 mm - 1.75 mm, 1.45 mm - 1.7 mm, 1.45 mm - 1.65 mm, 1.45 mm - 1.6 mm, 1.45 mm - 1.55 mm. Within the above ranges, the specific range of L1 can also be 1.5 mm - 1.8 mm, 1.5 mm - 1.75 mm, 1.5 mm - 1.7 mm, 1.5 mm - 1.65 mm, 1.5 mm - 1.6 mm, 1.5 mm - 1.55 mm. Among them, the actual values that L2 can take are 1.3 mm, 1.35 mm, 1.4 mm, 1.48 mm, 1.511 mm, 1.6 mm, 1.7 mm, 1.8 mm, etc.

[0064] The range of L3 is 7 mm - 11 mm. For example, the specific range of L1 can be 7 mm - 11 mm, 7 mm - 10.5 mm, 7 mm - 10 mm, 7 mm - 9.5 mm, 7 mm - 9.3 mm, 7 mm - 9.2 mm. Within the above ranges, the specific range of L1 can also be 7.5 mm - 11 mm, 7.5 mm - 10.5 mm, 7.5 mm - 10 mm, 7.5 mm - 9.5 mm, 7.5 mm - 9.3 mm, 7.5 mm - 9.2 mm. Within the above ranges, the specific range of L1 can also be 8 mm - 11 mm, 8 mm - 10.5 mm, 8 mm - 10 mm, 8 mm - 9.5 mm, 8 mm - 9.3 mm, 8 mm - 9.2 mm. Within the above ranges, the specific range of L1 can also be 8.5 mm - 11 mm, 8.5 mm - 10.5 mm, 8.5 mm - 10 mm, 8.5 mm - 9.5 mm, 8.5 mm - 9.3 mm, 8.5 mm - 9.2 mm. Within the above ranges, the specific range of L1 can also be 9 mm - 11 mm, 9 mm - 10.5 mm, 9 mm - 10 mm, 9 mm - 9.5 mm, 9 mm - 9.3 mm, 9 mm - 9.2 mm. Among them, the actual values that L3 can take are 7 mm, 7.9 mm, 8.6 mm, 9.186 mm, 9.5 mm, 10 mm, 10.6 mm, 11 mm, etc.

[0065] It can be understood that if the distance between each lens is too large, light is likely to scatter during propagation. If the distance between each lens is too small, light is likely to interfere and reflect between the lenses, thereby affecting the resolution of the lens module 100 and the clarity of the final image. Therefore, in this embodiment, on the basis that the distances between the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 satisfy the above condition formula two, by respectively controlling the distances between the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 to be within the above-listed numerical ranges, light scattering can be reduced and light is not likely to interfere and reflect, thereby enabling the lens module 100 to have better resolution.

[0066] More specifically, in one embodiment, the range of L1 is 0.2725 mm - 0.2734 mm, the range of L2 is 1.505 mm - 1.515 mm, and the range of L3 is 1.505 mm - 1.515 mm. As Figures 4 to 6 shown, when L1, L2, and L3 respectively take the above numerical ranges, the modulation degree of the MTF value of the lens module 100 at 20 lp / mm can be greater than 0.33, the lateral chromatic aberration < 3 microns, and the optical distortion < 0.4%, that is, the lens module 100 has better resolution.

[0067] Optionally, in one embodiment, as Figure 2 shown, the central thickness of the first lens 10 is T1, the central thickness of the second lens 20 is T2, the central thickness of the third lens 30 is T3, and the central thickness of the fourth lens 40 is T4; the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 also satisfy the following condition formula three: T4 > T2 > T1 = T3.

[0068] It should also be noted here that the "central thickness" of the lens refers to the material thickness between the light incident surface and the light exiting surface of the lens at the optical axis Z, which can be referred to Figure 2 , and the extension length of the optical axis Z inside the lens is the central thickness of the lens.

[0069] As Figures 4 to 6 shown, by controlling the central thicknesses of the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 to satisfy the above condition formula three in this application, the modulation degree of the MTF value of the lens module 100 at 20 lp / mm can be greater than 0.33, the lateral chromatic aberration < 3 microns, and the optical distortion < 0.4%, that is, the lens module 100 has better resolution.

[0070] Specifically, in one embodiment, the range of T1 is 2.856 mm - 3.219 mm. For example, T1 can be 2.856 mm, 2.884 mm, 2.925 mm, 2.968 mm, 3.076 mm, 3.12 mm, 3.166 mm, 3.219 mm, and so on.

[0071] The range of T2 is 3.78 mm - 4.96 mm. For example, T2 can be 3.78 mm, 4.25 mm, 4.58 mm, 4.7 mm, 4.75 mm, 4.88 mm, 4.9 mm, 4.96 mm, and so on.

[0072] The range of T3 is 2.97 mm - 4.15 mm. For example, T3 can be 2.97 mm, 3.08 mm, 3.12 mm, 3.36 mm, 3.62 mm, 3.73 mm, 3.88 mm, 4.15 mm, and so on.

[0073] The range of T4 is 4.45 mm - 5.37 mm. For example, T4 can be 4.45 mm, 4.65 mm, 4.8 mm, 5 mm, 5.13 mm, 5.26 mm, 5.3 mm, 5.37 mm, and so on.

[0074] It can be understood that if the central thickness of each lens is too large, it is easy to cause spherical aberration, that is, the light cannot be focused at the same point after passing through the lens, resulting in blurred imaging; if the central thickness of each lens is too small, it is easy to cause aberration, that is, the light at different positions is focused at different positions after passing through the lens, resulting in poor imaging quality. Therefore, on the basis that the central thicknesses of the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 satisfy the above condition formula three, this embodiment also controls the central thicknesses of the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 to be within the numerical ranges listed above, so as to avoid spherical aberration or aberration in imaging, that is, to make the lens module 100 have better resolution.

[0075] More specifically, in one embodiment, T1 is 3.12 mm, T2 is 4.7 mm, T3 is 3.12 mm, and T4 is 5 mm. As Figures 4 to 6 shown, when T1, T2, T3, and T4 take the above values respectively, the modulation depth of the MTF value of the lens module 100 at 20 lp / mm can be greater than 0.33, the lateral chromatic aberration < 3 microns, and the optical distortion < 0.4%, that is, the lens module 100 has better resolution.

[0076] Optionally, in one embodiment, the refractive index of the first lens 10 is N1, the refractive index of the second lens 20 is N2, the refractive index of the third lens 30 is N3, and the refractive index of the fourth lens 40 is N4; the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 also satisfy the following conditional formula four: N1 > N2 > N4 > N3.

[0077] As Figures 4 to 6 shown, by controlling the refractive indices of the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 to satisfy the above conditional formula four, the modulation transfer function (MTF) value of the lens module 100 at 20 lp / mm can be made to have a modulation greater than 0.33, the lateral chromatic aberration < 3 microns, and the optical distortion < 0.4%, that is, the lens module 100 has good resolution.

[0078] Specifically, in one embodiment, the range of N1 is 1.75 - 1.85. For example, N1 can be 1.75, 1.755, 1.786, 1.824, 1.8467, 1.848, 1.85, etc.

[0079] The range of N2 is 1.75 - 1.85. For example, N2 can be 1.75, 1.755, 1.786, 1.804, 1.846, 1.848, 1.85, etc.

[0080] The range of N3 is 1.55 - 1.65. For example, N3 can be 1.55, 1.558, 1.606, 1.613, 1.6201, 1.63, 1.65, etc.

[0081] The range of N4 is 1.75 - 1.85. For example, N4 can be 1.75, 1.754, 1.769, 1.7725, 1.78, 1.8, 1.85, etc.

[0082] It can be understood that if the refractive index of each lens is too large, it may lead to an aggravation of the dispersion phenomenon, thereby increasing the chromatic aberration of the lens module 100 and causing color distortion of the image; while if the refractive index of each lens is too small, it will result in insufficient chromatic aberration correction, and it may be necessary to use thicker lenses to achieve the required focal length and optical power, which is not conducive to the miniaturization of the lens module 100. Therefore, on the basis that the refractive indices of the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 satisfy the above conditional formula four, by respectively controlling the refractive indices of the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 to be within the numerical ranges listed above, this can not only reduce the chromatic aberration of the lens module 100 but also avoid the situation of insufficient chromatic aberration correction, making the lens module 100 have good resolution.

[0083] More specifically, in one embodiment, N1 is 1.8467, N2 is 1.804, N3 is 1.6201, and N4 is 1.7725. As Figures 4 to 6 shown, when N1, N2, N3, and N4 take the above values respectively, the modulation transfer function (MTF) value of the lens module 100 at 20 lp / mm can have a modulation greater than 0.33, the lateral chromatic aberration < 3 microns, and the optical distortion < 0.4%, that is, the lens module 100 has good resolution.

[0084] Furthermore, the Abbe number of the first lens 10 is 23.784, the Abbe number of the second lens 20 is 46.574, the Abbe number of the third lens 30 is 36.346, and the Abbe number of the fourth lens 40 is 49.599. As Figures 4 to 6 shown, when the Abbe numbers of the first lens 10, the second lens 20, the third lens 30, and the fourth lens 40 take the above values respectively, the modulation transfer function (MTF) value of the lens module 100 at 20 lp / mm can have a modulation greater than 0.33, the lateral chromatic aberration < 3 microns, and the optical distortion < 0.4%, that is, the lens module 100 has good resolution.

[0085] Optionally, in one embodiment, as Figure 2 shown, the first lens 10 further satisfies that the aperture of the incident light surface is D1 and the range of D1 is 21 mm - 26 mm, and the aperture of the emergent light surface is D2 and the range of D2 is 18 mm - 23 mm.

[0086] The second lens 20 further satisfies that the aperture of the incident light surface is D3 and the range of D3 is 18 mm - 23 mm, and the aperture of the emergent light surface is D4 and the range of D4 is 18 mm - 23 mm.

[0087] The third lens 30 further satisfies that the aperture of the incident light surface is D5 and the range of D5 is 15 mm - 20 mm, and the aperture of the emergent light surface is D6 and the range of D6 is 18 mm - 23 mm.

[0088] The fourth lens 40 further satisfies that the aperture of the incident light surface is D7 and the range of D7 is 29.6 mm - 34.6 mm, and the aperture of the emergent light surface is D8 and the range of D8 is 32 mm - 37 mm.

[0089] It should be noted here that the "aperture" refers to the effective light-transmitting diameter of the lens. Taking the incident light surface S7 of the fourth lens 40 as an example, the incident light surface S7 is a concave arc surface, and when it is orthogonally projected onto a plane perpendicular to the optical axis, its projection is circular, and the outer diameter of its projection is the aperture of the incident light surface S7. It should be noted that when measuring the aperture of the incident light surface S7, a circle of planes outside the incident light surface S7 is not involved in the measurement.

[0090] Specifically, in this embodiment, D1 can be 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, etc., and D2 can be 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, etc.

[0091] D3 can be 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, etc., and D4 can be 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, etc.

[0092] D5 can be 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, etc., and D6 can be 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, etc.

[0093] D7 can be 29.6mm, 30.6mm, 32mm, 33mm, 34mm, 34.6mm, etc., and D8 can be 32mm, 33mm, 34mm, 35mm, 36mm, 37mm, etc.

[0094] It can be understood that if the apertures of the light incident surface and the light exiting surface of the lens are too large, it will lead to a relatively large volume of the lens module, which is not conducive to the miniaturized design of the lens module; while if the apertures are too small, it will lead to poor light collection ability, and then problems such as dim imaging or vignetting will occur. Therefore, in this embodiment, by respectively controlling D1 to D8 within the ranges listed above, it is possible to not only avoid the lens module 100 from having an overly large volume to adapt to a small-sized light valve, but also ensure the light collection ability to make the imaging clear and bright, that is, to enable the lens module 100 to have better resolution.

[0095] More specifically, in one embodiment, D1 is 22mm, D2 is 19mm, both D3 and D4 are 19mm, D5 is 16mm, D6 is 19mm, D7 is 30.6mm, and D8 is 33mm. As Figures 4 to 6 shown, when D1 to D8 respectively take the above values, the modulation degree of the MTF value of the lens module 100 at 20 lp / mm can be greater than 0.33, the lateral chromatic aberration < 3 microns, and the optical distortion < 0.4%, that is, the lens module 100 has better resolution.

[0096] In summary, the lens module 100 provided by the present application includes a first lens 10, a second lens 20, a third lens 30, and a fourth lens 40 that are coaxial and arranged in sequence. The shapes, radii of curvature, central thicknesses of the four lenses, and the values of the central distances between adjacent lenses are respectively defined, such that the F-number (i.e., the aperture value) of the lens module 100 of the present application is 3.0, the projection ratio is 1.2:1, the maximum diameter of the imaging circle supports 56 mm, the optical distortion is less than 0.4%, the lateral chromatic aberration is less than 3 microns, and the modulation transfer function (MTF) at 20 lp / mm is greater than 0.33, that is, the lens module 100 has good resolution and can support a full high-definition resolution of 1920×1080, and can meet the full high-definition projection requirements of a small-sized (such as 2-inch) LCD light valve 50.

[0097] As Figure 2 shown, an embodiment of the present application further provides a projector 200. The projector 200 includes a light valve 50 and a lens module 100. The specific structure of the lens module 100 refers to the above embodiment. The light valve 50 is an LCD light valve 50 (i.e., a liquid crystal light valve 50), and the light valve 50 is located on the side where the incident light surface of the first lens 10 is located. Furthermore, the lens module 100 can project the image on the light valve 50 onto a screen. Since the projector 200 of the present application adopts all the technical solutions of the above all embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated herein one by one.

[0098] Optionally, in one embodiment, the distance between the light valve 50 and the first lens 10 is not less than 48 mm, and specifically can be 48 mm, 49 mm, 50 mm, 51 mm, 52 mm, 53 mm, 54 mm, 55 mm, etc.

[0099] It should be noted here that the "distance" between the light valve 50 and the first lens 10 refers to the width of the air gap at the position of the optical axis Z between the light valve 50 and the first lens 10, that is, the extension length of the optical axis Z between the light valve 50 and the first lens 10.

[0100] It can be understood that if the distance between the light valve 50 and the first lens 10 is too small, the image may be too compact or distorted. Therefore, in this embodiment, by controlling the distance between the light valve 50 and the first lens 10 to be not less than 48 mm, it is possible to avoid being too compact or distorted and ensure the imaging effect.

[0101] Optionally, in one embodiment, a Fresnel lens 60 is further provided between the light valve 50 and the first lens 10. The Fresnel lens 60 functions as a field lens to improve the brightness and contrast of the projected image. The distance between the Fresnel lens 60 and the light valve 50 ranges from 6 mm to 12 mm, and the specific distance can be 6 mm, 7 mm, 8 mm, 8.5 mm, 9 mm, 10 mm, 11 mm, 12 mm, etc.

[0102] It should also be noted here that the Fresnel lens 60 and the light valve 50 are parallel and spaced apart. The distance between the Fresnel lens 60 and the light valve 50 refers to the width of the air gap between the two, that is, the extension length of the optical axis Z between the Fresnel lens 60 and the light valve 50 is the distance between the Fresnel lens 60 and the light valve 50.

[0103] It can be understood that if the distance between the Fresnel lens 60 and the light valve 50 is too large, the light will diffuse after passing through the Fresnel lens 60 and cannot be accurately focused on the screen, resulting in a blurred and distorted projected image. If the distance between the Fresnel lens 60 and the light valve 50 is too small, the refraction and focusing ability of the light in the Fresnel lens 60 will be limited, resulting in the light not being fully expanded and projected onto the screen, resulting in an overly compact or distorted projected image. Therefore, in this embodiment, by controlling the distance between the Fresnel lens 60 and the light valve 50 to be between 6 mm and 12 mm, it is possible to avoid the diffusion of light after passing through the Fresnel lens 60 and ensure the refraction and focusing ability of the light in the Fresnel lens 60, thereby improving the projection quality.

[0104] Optionally, in one embodiment, the equivalent focal length of the Fresnel lens 60 ranges from 50 mm to 55 mm, and the specific equivalent focal length can be 50 mm, 51 mm, 52 mm, 52.5 mm, 53 mm, 54 mm, 54.5 mm, 55 mm, etc.

[0105] It can be understood that if the equivalent focal length of the Fresnel lens 60 is too long, the projected image will become larger, while reducing the clarity and resolution of the image. If the equivalent focal length of the Fresnel lens 60 is too short, the projected image will become smaller, and image distortion and aberration may occur. Therefore, in this embodiment, by controlling the equivalent focal length of the Fresnel lens 60 to be in the range of 50 mm to 55 mm, it is possible to ensure the clarity and resolution of the projected image and avoid image distortion and aberration, thereby improving the projection effect.

[0106] Furthermore, the refractive index of the Fresnel lens 60 is 1.4918, the Abbe number is 57.441, and the central thickness is 1.5 mm. As Figures 4 to 6As shown in the figure, by using the Fresnel lens 60 with the above refractive index, Abbe number, and central thickness in combination with the lens module 100 described above, the modulation at 20 lp / mm of the MTF value can be made greater than 0.33, the lateral chromatic aberration < 3 μm, and the optical distortion < 0.4%, that is, high-definition projection of the light valve 50 can be achieved.

[0107] In summary, by respectively defining the distance between the light valve 50 and the first lens 10, the distance between the light valve 50 and the Fresnel lens 60, as well as the equivalent focal length, refractive index, Abbe number, and central thickness of the Fresnel lens 60, high-definition projection of the small-sized light valve 50 can be achieved in combination with the aforementioned lens module 100, improving the quality of the projection image.

[0108] In the above embodiments, the descriptions of the respective embodiments have their own emphases. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments. In the description of the present application, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more features.

[0109] The above has introduced the lens module provided by the embodiments of the present application in detail. Specific examples are used herein to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those skilled in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A lens module, characterized in that, it includes: a first lens, a second lens, a third lens, and a fourth lens that are coaxial and arranged in sequence; the first lens satisfies: the incident light surface is convex and the radius of curvature of the incident light surface is R1, the outgoing light surface is concave and the radius of curvature of the outgoing light surface is R2; the second lens satisfies: the incident light surface is convex and the radius of curvature of the incident light surface is R3, the outgoing light surface is convex and the radius of curvature of the outgoing light surface is R4; the third lens satisfies: the incident light surface is concave and the radius of curvature of the incident light surface is R5, the outgoing light surface is concave and the radius of curvature of the outgoing light surface is R6; the fourth lens satisfies: the incident light surface is concave and the radius of curvature of the incident light surface is R7, the outgoing light surface is convex and the radius of curvature of the outgoing light surface is R8; the first lens, the second lens, the third lens, and the fourth lens satisfy the following conditional expressions: R1 > R2, R3 < R4, R5 < R6, R7 > R8; R7 > R1 > R5 > R3, R6 > R4 > R8 > R2.

2. The lens module according to claim 1, characterized in that: the range of R1 is 33.981 mm - 40.152 mm; the range of R2 is 23.579 mm - 28.251 mm; the range of R3 is 25.337 mm - 28.141 mm; the range of R4 is 41.256 mm - 48.530 mm; the range of R5 is 28.971 mm - 32.115 mm; the range of R6 is 45.597 mm - 52.818 mm; the range of R7 is 57.248 mm - 62.596 mm; the range of R8 is 27.222 mm - 33.554 mm.

3. The lens module according to claim 2, characterized in that: R1 is 38.977 mm, and R2 is 25.221 mm; R3 is 27.337 mm, and R4 is 47.939 mm; R5 is 29.541 mm, and R6 is 50.815 mm; R7 is 61.932 mm, and R8 is 29.347 mm.

4. The lens module according to claim 1, characterized in that: the distance between the first lens and the second lens is L1; the distance between the second lens and the third lens is L2; the distance between the third lens and the fourth lens is L3; the first lens, the second lens, the third lens, and the fourth lens also satisfy the following conditional expression: L3 > L2 > L1.

5. The lens module according to claim 4, characterized in that, the sizes of L1, L2, and L3 can be adjusted and set.

6. The lens module according to claim 4, characterized in that: the range of L1 is: 0.2 mm - 0.35 mm; the range of L2 is: 1.3 mm - 1.8 mm; the range of L3 is: 7 mm - 11 mm.

7. The lens module according to claim 6, characterized in that: the range of L1 is 0.2725 mm - 0.2734 mm; The range of the L2 is 1.505 mm - 1.515 mm; The range of the L3 is 9.181 mm - 9.191 mm.

8. The lens module according to claim 1, characterized in that: 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 the central thickness of the fourth lens is T4; The first lens, the second lens, the third lens and the fourth lens also satisfy the following conditional formula: T4 > T2 > T1 = T3.

9. The lens module according to claim 8, characterized in that: The range of the T1 is 2.856 mm - 3.219 mm; The range of the T2 is 3.78 mm - 4.96 mm; The range of the T3 is 2.97 mm - 4.15 mm; The range of the T4 is 4.45 mm - 5.37 mm.

10. The lens module according to claim 9, characterized in that, The T1 is 3.12 mm, the T2 is 4.7 mm, the T3 is 3.12 mm, and the T4 is 5 mm.

11. The lens module according to claim 1, characterized in that: The refractive index of the first lens is N1, the refractive index of the second lens is N2, the refractive index of the third lens is N3, and the refractive index of the fourth lens is N4; The first lens, the second lens, the third lens and the fourth lens also satisfy the following conditional formula: N1 > N2 > N4 > N3.

12. The lens module according to claim 11, characterized in that: The range of the N1 is 1.75 - 1.85; The range of the N2 is 1.75 - 1.85; The range of the N3 is 1.55 - 1.65; The range of the N4 is 1.75 - 1.

85.

13. The lens module according to claim 12, characterized in that, The N1 is 1.8467, the N2 is 1.804, the N3 is 1.6201, and the N4 is 1.7725.

14. The lens module according to claim 13, characterized in that: The Abbe number of the first lens is 23.784; The Abbe number of the second lens is 46.574; The Abbe number of the third lens is 36.346; The Abbe number of the fourth lens is 49.

599.

15. The lens module according to any one of claims 1 to 14, characterized in that: The first lens further satisfies: the aperture of the incident light surface is D1 and the range of the D1 is 21 mm - 26 mm, the aperture of the outgoing light surface is D2 and the range of the D2 is 18 mm - 23 mm; The second lens further satisfies: the aperture of the incident light surface is D3 and the range of the D3 is 18 mm - 23 mm, the aperture of the outgoing light surface is D4 and the range of the D4 is 18 mm - 23 mm; The third lens further satisfies: the aperture of the incident light surface is D5 and the range of the D5 is 15 mm - 20 mm, the aperture of the outgoing light surface is D6 and the range of the D6 is 18 mm - 23 mm; The fourth lens further satisfies that the aperture of the incident light surface is D7, and the range of D7 is 29.6 mm - 34.6 mm, the aperture of the outgoing light surface is D8, and the range of D8 is 32 mm - 37 mm.

16. The lens module according to claim 15, characterized in that: D1 is 22 mm, D2 is 19 mm; both D3 and D4 are 19 mm; D5 is 16 mm, D6 is 19 mm; D7 is 30.6 mm, D8 is 33 mm.

17. A projector, characterized in that, comprising a light valve and the lens module according to any one of claims 1 to 16, and the light valve is located on the side where the incident light surface of the first lens is located.

18. The projector according to claim 17, characterized in that, the distance between the light valve and the first lens is not less than 48 mm.

19. The projector according to claim 17, characterized in that, a Fresnel lens is further provided between the light valve and the first lens, and the distance between the Fresnel lens and the light valve ranges from 6 mm to 12 mm.

20. The projector according to claim 19, characterized in that, the range of the equivalent focal length of the Fresnel lens is: 50 mm - 55 mm.

Images