A 4P lens capable of reducing temperature drift

Abstract

A 4P lens capable of reducing temperature drift, the lens comprises, from the object side to the image side, along the optical axis, a first lens P1, a second lens P2, a third lens P3, and a fourth lens P4, an aperture STO is arranged at the front end of the lens, the first lens P1 is a biconvex positive lens, the second lens P2 is a crescent-shaped positive lens with a concave surface facing the object side and a convex surface facing the image side, the third lens P3 is a crescent-shaped negative lens with a concave surface facing the object side and a convex surface facing the image side, and the fourth lens P4 is a crescent-shaped positive lens with a convex surface facing the object side and a concave surface facing the image side. The 4P lens of the present invention effectively solves the temperature drift problem of the optical lens, and can maintain the same image quality level as that at room temperature at high and low temperatures; at the same time, it can also achieve the technical effect of shortening the total length TTL of the lens and high imaging quality.

Description

Technical Field

[0001] The invention relates to an optical lens, in particular to a 4P lens capable of reducing temperature drift. Background Art

[0002] In the field of optical imaging, we strive for high pixels and high contrast, so more light is needed to increase the brightness of the picture to improve the image quality. As mobile phones and surveillance systems become more and more popular, the requirements for thin plastic lenses are also increasing, including that the imaging quality of the lens should not change at high and low temperatures. In the existing technology, plastic lenses are thin, light and short, but their physical properties will change at high and low temperatures, that is, the characteristics of thermal expansion and contraction will produce a "temperature drift" phenomenon. In order to ensure the image quality at high and low temperatures, the change in back focus at high and low temperatures must be minimized, so as to avoid lens defocusing and maintain image quality.

[0003] In order to reduce the "temperature drift", traditional camera lenses usually add a glass lens to the lens structure to compensate for the temperature drift. However, this glass lens structure not only increases the cost, but also makes the lens length TTL very long, which is not conducive to miniaturization, and easily complicates the process assembly, resulting in a loss of yield and increasing costs. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a 4P lens capable of reducing temperature drift, which effectively solves the temperature drift problem of the optical lens and maintains the same image quality level as that at room temperature at both high and low temperatures; at the same time, it can also achieve the technical effect of shortening the total length TTL of the lens and high imaging quality.

[0005] The technical solution adopted by the present invention is:

[0006] A 4P lens capable of reducing temperature drift, the lens comprises, from the object side to the image side along the optical axis, a first lens P1, a second lens P2, a third lens P3, and a fourth lens P4, an aperture STO is arranged at the front end of the lens, the first lens P1 is a double convex positive lens, the second lens P2 is a crescent-shaped positive lens with a concave surface facing the object side and a convex surface facing the image side, the third lens P3 is a crescent-shaped negative lens with a concave surface facing the object side and a convex surface facing the image side, and the fourth lens P4 is a crescent-shaped positive lens with a convex surface facing the object side and a concave surface facing the image side.

[0007] The first lens P1, the second lens P2, the third lens P3 and the fourth lens P4 are all plastic lenses, forming a "+, +, -, +" lens group structure.

[0008] The first lens P1, the second lens P2, the third lens P3, and the fourth lens P4 are all aspherical lenses with at least one surface.

[0009] The focal length of the first lens P1 is f1, the focal length of the second lens P2 is f2, the focal length of the third lens P3 is f3, the focal length of the fourth lens P4 is f4, and the combined focal length of the system is f;

[0010] Satisfies: 0.7<|f2 / f1|<1.2; 0.95<|f4 / f3|<1.5.

[0011] The outer diameter of the fourth lens P4 is D. The R2 surface shape curve of the fourth lens P4 has a positive tangent angle starting from the center, and will be inflected between 0.7D and 0.8D. Thereafter, the tangent angle will turn into a negative angle, and the tangent angle of the effective diameter 1.0D of the R2 surface of the fourth lens P4 is between -70 degrees and -80 degrees.

[0012] The lens also includes an infrared filter IR and protective glass CG.

[0013] The 4P lens capable of reducing temperature drift of the present invention has the advantages that:

[0014] 1) The first lens P1, the second lens P2, the third lens P3 and the fourth lens P4 are all aspherical plastic lenses, which utilize aspherical mold manufacturing technology, are suitable for mass production, reduce lens costs, facilitate assembly, and improve yield rate.

[0015] 2) Effectively solve the temperature drift problem of optical lenses, while achieving the advantage of shortening the total length TTL of the lens, reducing temperature drift while miniaturizing the lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the 4P lens structure of the present invention;

[0017] Among them: a represents the object side, b represents the image side, and sensor represents the imaging surface.

[0018] Figure 2 FIG. 4 is a shape curve diagram of the R2 surface of the fourth lens element P4 of the 4P lens of the present invention.

[0019] Figure 3 FIG. 4 is a graph showing the tangent angle of the R2 surface of the fourth lens element P4 of the 4P lens of the present invention.

[0020] FIG4(1) is a schematic diagram of the tangent angle of the R2 surface of the fourth lens element P4 of the 4P lens of the present invention;

[0021] Figure 4(2) is a local enlarged view of location M in Figure 4(1).

[0022] Figure 5 (1) is the MIF diagram of Case 1;

[0023] Figure 5(2) is the layout diagram of Case 1;

[0024] Figure 5(3) is the field curvature diagram for Case 1;

[0025] Figure 5(4) is the distortion diagram of Case 1;

[0026] Figure 5 (5) is the spherical aberration diagram of Case 1;

[0027] Figure 5(6) is a schematic diagram of the tangent angle change curve of Case 1.

[0028] Figure 6 (1) is the MIF diagram of Case 2;

[0029] Figure 6(2) is the layout diagram of Case 2;

[0030] Figure 6 (3) is the field curvature diagram for Case 2;

[0031] Figure 6(4) is the distortion diagram of Case 2;

[0032] Figure 6(5) is the spherical aberration diagram of Case 2;

[0033] Figure 6 (6) is a schematic diagram of the tangent angle change curve of Case 2.

[0034] Figure 7 (1) is the MIF diagram of Case 3;

[0035] Figure 7(2) is the layout diagram of Case 3;

[0036] Figure 7(3) is the field curvature diagram for Case 3;

[0037] Figure 7(4) is the distortion diagram of Case 3;

[0038] Figure 7(5) is the spherical aberration diagram of Case 3;

[0039] Figure 7(6) is a schematic diagram of the tangent angle change curve of Case 3.

[0040] Figure 8 (1) is the MIF diagram of Case 4;

[0041] Figure 8(2) is the layout diagram of Case 4;

[0042] Figure 8(3) is the field curvature diagram for Case 4;

[0043] Figure 8(4) is the distortion diagram of Case 4;

[0044] Figure 8(5) is the spherical aberration diagram of Case 4;

[0045] Figure 8(6) is a schematic diagram of the tangent angle change curve of Case 4.

[0046] Figure 9 (1) is the MIF diagram of Case 5;

[0047] Figure 9(2) is the layout diagram of Case 5;

[0048] Figure 9(3) is the field curvature diagram for Case 5;

[0049] Figure 9(4) is the distortion diagram of Case 5;

[0050] Figure 9(5) is the spherical aberration diagram of Case 5;

[0051] Figure 9(6) is a schematic diagram of the tangent angle change curve of Case 5.

[0052] Figure 10 (1) is the MIF diagram of Case 6;

[0053] Figure 10(2) is the layout diagram of Case 6;

[0054] Figure 10(3) is the field curvature diagram for Case 6;

[0055] Figure 10(4) is the distortion diagram of Case 6;

[0056] Figure 10(5) is the spherical aberration diagram of Case 6;

[0057] Figure 10(6) is a schematic diagram of the tangent angle change curve of Case 6. DETAILED DESCRIPTION

[0058] like Figure 1 As shown in the figure, a 4P lens capable of reducing temperature drift is a lens composed of 4 plastic lenses. The order from the object side is aperture STO, first lens P1, second lens P2, third lens P3, fourth lens P4, infrared filter IR, protective glass CG, P1 to P4 are all aspherical surfaces, and are used in electronic products such as camera lenses.

[0059] The present invention constitutes a 4P imaging lens including an aspherical lens, and an aperture STO is arranged at the front end of the lens.

[0060] The first lens P1 is a biconvex positive lens with at least one aspherical surface; its focal length is f1;

[0061] The second lens P2 is a positive meniscus lens with a concave surface on the object side and a convex surface on the image side, and at least one aspherical surface; its focal length is f2;

[0062] The third lens P3 is a meniscus-shaped negative lens with a concave surface on the object side and a convex surface on the image side, and at least one aspherical surface; its focal length is f3;

[0063] The fourth lens P4 is a crescent-shaped positive lens with a convex surface facing the object side and a concave surface facing the image side, and at least one aspherical surface; its focal length is f4, and the outer diameter of the fourth lens P4 is D.

[0064] The resulting focal length of the system is f.

[0065] Satisfying: 0.7<|f2 / f1|<1.2 is beneficial to controlling spherical aberration.

[0066] 0.95<|f4 / f3|<1.5, which is beneficial for controlling chromatic aberration and distortion.

[0067] The shape curve of the R2 surface of the fourth lens P4 is as follows: Figure 2 The tangent angle of the shape curve is from the center to the outer diameter D. Figure 3 As shown in the curve.

[0068] The tangent angle is positive from the center, and will be reversed between 0.7D and 0.8D, after which the tangent angle will turn negative. The tangent angle of the effective diameter of the R2 surface of the fourth lens P4 is 1.0D and will be between -70 degrees and -80 degrees.

[0069] The description of the tangent angle is shown in Figure 4 (1) and Figure 4 (2). The tangent angle θ is the angle between the tangent line of a point on the curved surface and the optical axis. The vertical height h from the center is indicated in the figure, and the effective diameter D is indicated in the figure.

[0070] Case 1:

[0071] Satisfying conditions and definition of tangent angle:

[0072] Conditions: 0.7<|f2 / f1|<1.2; 0.95<|f4 / f3|<1.5

[0073]

[0074] For example, the tangent angle: the tangent angle starts to bend at 0.76D; and the 1.0D angle is -78.8°.

[0075] Case 2:

[0076] The conditions are not met and the tangent angle definition is not met:

[0077] Conditions: 0..7<||f2 / f1||<1..2; 0..95<||f4 / f3||<1..5

[0078]

[0079] Temperature drift -20 degrees Temperature drift 60 degrees <![CDATA[0.011 mm (Change in optical back focus ) > <![CDATA[0.047 mm (Change in optical back focus ) >

[0080] Example 2: Tangent angle: The tangent angle starts to bend at 0.67D; and the 1.0D angle is -29.9°.

[0081] Case 3:

[0082] Satisfies the conditions but does not satisfy the tangent angle definition:

[0083] Conditions: 0.7<|f2 / f1|<1.2; 0.95<|f4 / f3|<1.5

[0084] Case 3 P1(f1) P2(f2) P3(f3) P4(f4) LENS(f) f2 / f1 f4 / f3 Focal length f 5.2869 5.4026 -2.5996 3.3815 4.2160 1.0219 -1.3008

[0085] Temperature drift -20 degrees Temperature drift 60 degrees <![CDATA[-0.025mm (Change in optical back focus) ) > <![CDATA[0.028mm (variation of optical back focus ) >

[0086] Example 3: Tangent angle: The tangent angle starts to bend at 0.82D; and the 1.0D angle is -62.9°.

[0087] Case 4:

[0088] Satisfying conditions and definition of tangent angle:

[0089] Conditions: 0.7<|f2 / f1|<1.2; 0.95<|f4 / f3|<1.5

[0090]

[0091] Temperature drift -20 degrees Temperature drift 60 degrees <![CDATA[-0.004 mm (Change in optical back focus) ) > <![CDATA[0.0015mm (variation of optical back focal length ) >

[0092] Example 4: Tangent angle: The tangent angle starts to bend at 0.76D; and the 1.0D angle is -78.9°.

[0093] Case 5:

[0094] Satisfies the conditions but does not satisfy the tangent angle definition:

[0095] Conditions: 0.7<|f2 / f1|<1.2; 0.95<|f4 / f3|<1.5

[0096]

[0097] Temperature drift -20 degrees Temperature drift 60 degrees <![CDATA[-0.034mm (Change in optical back focal length) ) > <![CDATA[0.036mm (variation of optical back focal length ) >

[0098] Example 5: Tangent angle: The tangent angle starts to bend at 0.87D; and the 1.0D angle is -30°.

[0099] Case 6:

[0100] The conditions are not met and the tangent angle definition is not met:

[0101] Conditions: 0.7<|f2 / f1|<1.2; 0.95<|f4 / f3|<1.5

[0102]

[0103] Temperature drift -20 degrees Temperature drift 60 degrees <![CDATA[-0.026mm (Change in optical back focus) ) > <![CDATA[0.0395mm (Change in optical back focus ) >

[0104] Example 6: Tangent angle: The tangent angle starts to bend at 0.94D; and the 1.0D angle is -7.8°.

Claims

1. A 4P lens capable of reducing temperature drift, characterized in that: The lens comprises, from the object side to the image side, along the optical axis: a first lens P1, a second lens P2, a third lens P3, and a fourth lens P4, an aperture STO is arranged at the front end of the lens, the first lens P1 is a biconvex positive lens, the second lens P2 is a crescent-shaped positive lens with a concave surface on the object side and a convex surface on the image side, the third lens P3 is a crescent-shaped negative lens with a concave surface on the object side and a convex surface on the image side, and the fourth lens P4 is a crescent-shaped positive lens with a convex surface on the object side and a concave surface on the image side; the focal length of the first lens P1 is f1, the focal length of the second lens P2 is f2, the focal length of the third lens P3 is f3, and the focal length of the fourth lens P4 is f4, and the composite focal length of the system is f; Satisfies: 0.7<|f2 / f1|<1.2; 0.95<|f4 / f3|<1.5; the outer diameter of the fourth lens P4 is D, the R2 surface shape curve of the fourth lens P4 has a positive tangent angle starting from the center, and will be inflected when it satisfies the range of 0.7D to 0.8D, after which the tangent angle will turn to a negative angle, and the tangent angle of the R2 surface effective diameter 1.0D of the fourth lens P4 is between -70 degrees and -80 degrees; the first lens P1, the second lens P2, the third lens P3, and the fourth lens P4 are all plastic lenses.

2. A 4P lens capable of reducing temperature drift according to claim 1, characterized in that: The first lens P1, the second lens P2, the third lens P3, and the fourth lens P4 are all lenses with at least one aspherical surface.

3. A 4P lens capable of reducing temperature drift as claimed in any one of claims 1 to 2, characterized in that: The lens also includes an infrared filter IR and protective glass CG.

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