Optical imaging lens

Abstract

The invention relates to the field of optical imaging, and particularly discloses an optical imaging lens. Comprising a first lens, a second lens, a third lens and a fourth lens which are sequentially distributed, the paraxial part of the image side surface of the first lens is a convex surface, and the paraxial part of the object side surface is a plane; the paraxial region of the image side surface of the second lens is a convex surface, and the paraxial region of the object side surface is a plane; the image side surface and the object side surface of the third lens are convex surfaces near the optical axis; the image-side surface and the object-side surface of the fourth lens are concave surfaces near the optical axis, and the convex surface of the image-side surface of the third lens near the optical axis is located in the concave surface formed near the optical axis of the object-side surface of the fourth lens; the optical imaging lens satisfies 0.34 lt; (CT2 + CT3) / TTLlt; and 0.41. According to the optical imaging lens, the problem that the thickness of the lens is relatively large is solved.

Description

Technical Field

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

[0002] The rapid development of technology, especially electronics, has led to the rapid spread of portable electronic devices, driving the rapid development of imaging module technologies for these devices. Currently, imaging modules are finding increasingly widespread applications in smartphones, tablets, dashcams, action cameras, and other fields. The continuous upgrade trend of smartphones and other electronic products is also driving increasingly demanding lens requirements. The refractive power configuration of traditional four-element lenses is insufficient to achieve both miniaturization and wide-angle imaging requirements.

[0003] Currently, there is an optical imaging lens as disclosed in application number 202010992595.9, which includes four lenses, each of which includes an object-side surface facing the object side and an image-side surface facing the image side, and the four lenses include, in order from the object side to the image side: a first lens having positive refractive power, and the object-side surface of the first lens is convex at the near optical axis; a second lens having negative refractive power, and the object-side surface of the second lens is concave at the near optical axis; a third lens having positive refractive power, the object-side surface of the third lens is concave at the near optical axis, and the image-side surface of the third lens is convex at the near optical axis; and a fourth lens having negative refractive power, the object-side surface of the fourth lens is convex at the near optical axis, the object-side surface of the fourth lens is concave away from the optical axis, the image-side surface of the fourth lens is concave at the near optical axis, and the image-side surface of the fourth lens is convex away from the optical axis.

[0004] While the aforementioned lens also includes four elements, they can adjust the viewing angle to meet different conditions, allowing for wider image coverage while minimizing distortion. However, the overall thickness of the lens is still relatively large, satisfying the thickness requirements of current electronic products such as mobile phones and tablets. Summary of the Invention

[0005] The present invention aims to provide an optical imaging lens to solve the problem of relatively large lens thickness.

[0006] To achieve the above-mentioned object, the present invention adopts the following technical solution: an optical imaging lens, comprising a first lens, a second lens, a third lens, and a fourth lens arranged in sequence, wherein the image-side surface of the first lens is convex at the near optical axis and the object-side surface is flat at the near optical axis; the image-side surface of the second lens is convex at the near optical axis and the object-side surface is flat at the near optical axis; the image-side surface and the object-side surface of the third lens are both convex at the near optical axis; the image-side surface and the object-side surface of the fourth lens are both concave at the near optical axis, and the convex surface of the image-side surface of the third lens at the near optical axis is located within the concave surface formed at the near optical axis of the object-side surface of the fourth lens;

[0007] The aspheric curve equations of the first lens, the second lens, the third lens and the fourth lens are:

[0008]

[0009] The optical imaging lens meets 0.34<(CT2+CT3) / TTL<0.41.

[0010] In this scheme, Z is the distance vector height of the aspheric surface from the origin of the aspheric surface when the aspheric surface is at a height of r along the optical axis, c is the paraxial curvature of the aspheric surface (radius of curvature R = 1 / c, which is the inverse of the curvature); k is the cone coefficient; Ai is the i-th order coefficient of the aspheric surface. TTL in this scheme refers to the distance from the object side of the first lens to the image plane at the paraxial point. The object side in this scheme is convex, which means that when the object side of the lens is cut through any point on the surface, the surface is always to the right of the cut surface, and its radius of curvature is positive; otherwise, the object side is concave, and its radius of curvature is negative. The image side is convex, which means that when the image side of the lens is cut through any point on the surface, the surface is always to the left of the cut surface, and its radius of curvature is negative; otherwise, the image side is concave, and its radius of curvature is positive.

[0011] In this solution, the first lens and the fourth lens both have negative refractive power, and the second lens and the third lens have positive refractive power.

[0012] The beneficial effects of this program are:

[0013] 1. This solution controls the ratio (CT2 + CT3) / TTL, improving the processability of the second and third lenses while reducing the overall size of the optical imaging lens. The second and third lenses each produce weaker ghost images, and, in conjunction with the first lens, reduce chromatic aberration and distortion. Furthermore, the third lens is thinner, which helps reduce the sensitivity of the optical imaging lens.

[0014] 2. In this solution, the object side surface of the fourth lens is concave near the optical axis. After the third and fourth lenses are installed, the concave surface forms a groove, while the image side surface of the third lens is convex. At this time, the groove can accommodate the convex surface, so that the distance between the third and fourth lenses can be reduced, thereby reducing the overall thickness of the lens.

[0015] Further, VD1=VD2=VD3>45.

[0016] The beneficial effects of this solution are: VD1, VD2 and VD3 refer to the Abbe numbers of the first lens, the second lens and the third lens respectively, and the lens in this solution is more conducive to controlling the vertical axis chromatic aberration of the edge field of view.

[0017] Furthermore, the distortion is 16 to 26%.

[0018] The beneficial effects of this solution are: Distortion is the optical distortion value of the lens in the present invention at 1.0F, and the lens in this solution can keep the captured image from being deformed.

[0019] Furthermore, ND4>ND3.

[0020] The beneficial effects of this solution are as follows: ND3 and ND4 refer to the refractive indices of the third lens and the fourth lens respectively. The refractive index of the fourth lens in this solution is larger, which makes the lens have better imaging quality.

[0021] Furthermore, VD3 / VD4>2.

[0022] The beneficial effects of this solution are: VD4 refers to the Abbe number of the fourth lens. The lens in this solution is conducive to better control of chromatic aberration and achieve better imaging quality.

[0023] Further, 0.6 <f3 / f<0.73。

[0024] The beneficial effects of this solution are as follows: f refers to the focal length of the imaging lens system, and f3 refers to the focal length of the third lens. By controlling the ratio of the third lens' focal length to the overall system focal length, this solution prevents excessive focal length of the third lens, reduces lens sensitivity, effectively improves imaging quality, and simultaneously reduces the optical length of the lens.

[0025] Further, 0.60|f4 / f|<0.74.

[0026] This solution has the following beneficial effects: f4 refers to the focal length of the fourth lens. By controlling the ratio of the fourth lens' focal length to the overall system focal length, this solution can prevent excessive focal length of the fourth lens from decreasing the sensitivity of the optical imaging lens, further improving imaging quality while also shortening the optical length of the optical imaging lens.

[0027] Further, 0.30<(T12+T23) / ImgH<0.35.

[0028] The beneficial effects of this solution are as follows: T12 refers to the distance on the optical axis between the first and second lenses, and T23 refers to the distance on the optical axis between the second and third lenses. ImgH is half the diagonal length of the effective imaging area of ​​the wide-angle lens. In the lens of this solution, the first, second, and third lenses are rationally distributed, resulting in a compact optical imaging lens.

[0029] Further, 2.28 <CT2 / T23<7.05。

[0030] The beneficial effect of this solution is that CT2 refers to the maximum thickness of the second lens on the optical axis. The thickness of the lens in this solution is further reduced, which is beneficial to reducing the sensitivity of the optical imaging lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A front view of a lens according to an embodiment of the present invention;

[0032] Figure 2 Graphs showing astigmatism and distortion of the optical imaging lens in this embodiment of the present invention;

[0033] Figure 3 is a spherical aberration curve diagram of the optical imaging lens in an embodiment of the present invention;

[0034] Figure 4 is the aspheric curve equation in the embodiment of the present invention. DETAILED DESCRIPTION

[0035] The following is further described in detail through specific implementation methods:

[0036] The figure marks in the drawings of the specification include: first lens object side 1, first lens image side 2, aperture 3, second lens object side 4, second lens image side 5, third lens object side 6, third lens image side 7, fourth lens object side 8, fourth lens image side 9, infrared filter object side 10, infrared filter image side 11, and imaging surface 12.

[0037] Example

[0038] The embodiment is basically as follows Figure 1As shown, an optical imaging lens includes a first lens, a second lens, a third lens, and a fourth lens, which are arranged in sequence from left to right, and gaps are provided between adjacent lenses. In this embodiment, the first lens and the fourth lens both have negative refractive power, and the second lens and the third lens have positive refractive power: the left side of the lens is the object side, the right side of the lens is the image side, the left side surfaces of the first lens, the second lens, the third lens, and the fourth lens are the object side surfaces, and the right side surfaces are the image side surfaces. The image side surface of the first lens is convex at the near optical axis, and the object side surface is flat at the near optical axis; the image side surface of the second lens is convex at the near optical axis, and the object side surface is flat at the near optical axis; the image side surface and the object side surface of the third lens are both convex at the near optical axis; the image side surface and the object side surface of the fourth lens are both concave at the near optical axis, and the convex surface of the image side surface of the third lens at the near optical axis is located within the concave surface formed at the near optical axis of the object side surface of the fourth lens.

[0039] The object side of the second lens is provided with an aperture;

[0040] The aspheric curve equations of the first lens, the second lens, the third lens and the fourth lens are:

[0041]

[0042] In this solution, Z is the distance vector height of the aspheric surface from the origin of the aspheric surface at a height of r along the optical axis, c is the paraxial curvature of the aspheric surface (radius of curvature R = 1 / c, which is the inverse of the curvature); k is the conic coefficient; Ai is the i-th order coefficient of the aspheric surface. Specifically, the high-order coefficients in the present invention include A4, A6, A8, A10, A12, A14, A16, A18, and A20. The aspheric coefficients in this embodiment are specifically shown in the following table:

[0043]

[0044]

[0045] The optical imaging lens meets the following conditions at the same time:

[0046] 0.34<(CT2+CT3) / TTL<0.41;

[0047] VD1=VD2=VD3>45;

[0048] Distortion is 16-26%;

[0049] ND4>ND3;

[0050] VD3 / VD4>2;

[0051] 0.6 <f3 / f<0.73;

[0052] 0.60|f4 / f|<0.74;

[0053] 0.30<(T12+T23) / ImgH<0.35;

[0054] 2.28 <CT2 / T23<7.05;

[0055] f4 / f5>0.

[0056] Specifically, the parameters in this embodiment are shown in the following table:

[0057] (CT2+CT3) / TTL 0.442 |f4 / f| 0.665 Distortion 26.88％ (T12+T23) / ImgH 0.352 f3 / f 0.703 CT2 / T23 5.072

[0058] The curvature radius of the optical lens, the thickness of the lens, the air gap, the refractive index and the Abbe coefficient of the lens material, and the focal length of the lens in this embodiment are specifically shown in the following table:

[0059]

[0060]

[0061] Specifically, the focal length of the imaging lens group in this embodiment is 1.56 mm, Fno=2, Fov=119.1°, and the lens in this embodiment is tested. Figure 2 Astigmatism, distortion curves and Figure 3 As can be seen from the spherical aberration curve, the lens of the present invention has high imaging clarity and low deformation of the photographed object while maintaining a relatively small thickness.

[0062] The above is only an embodiment of the present invention, and the common knowledge such as the specific technical solutions and / or characteristics in the solution are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. An optical imaging lens, comprising a first lens, a second lens, a third lens and a fourth lens arranged in sequence, characterized in that: The first lens has a convex surface at the near optical axis on the image side surface and a flat surface at the near optical axis on the object side surface; the second lens has a convex surface at the near optical axis on the image side surface and a flat surface at the near optical axis on the object side surface; the third lens has convex surfaces at the near optical axis on both the image side surface and the object side surface; the fourth lens has concave surfaces at the near optical axis on both the image side surface and the object side surface, and the convex surface at the near optical axis on the image side surface of the third lens is located within the concave surface formed at the near optical axis on the object side surface of the fourth lens; The aspheric curve equations of the first lens, the second lens, the third lens and the fourth lens are: The optical imaging lens satisfies 0.34<(CT2+CT3) / TTL<0.

41.

2. The optical imaging lens according to claim 1, characterized in that: VD1=VD2=VD3>45.

3. The optical imaging lens according to claim 2, wherein: Distortion is 16-26%.

4. The optical imaging lens according to claim 3, characterized in that: ND4>ND3.

5. The optical imaging lens according to claim 4, characterized in that: VD3 / VD4>2.

6. The optical imaging lens according to claim 5, characterized in that: 0.6 <f3 / f<0.73。 7. The optical imaging lens according to claim 6, characterized in that: 0.60|f4 / f|<0.

74.

8. The optical imaging lens according to claim 7, characterized in that: 0.30<(T12+T23) / ImgH<0.

35.

9. The optical imaging lens according to claim 8, characterized in that: 2.28 <CT2 / T23<7.05。

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