Optical lens

Abstract

This invention discloses an optical lens, which, from the object side to the imaging plane, comprises: a first lens with positive optical power, whose object side is convex and image side is concave or convex; a second lens with optical power, whose object side is convex or concave and image side is concave; a third lens with negative optical power, whose object side is concave or convex and image side is concave; a fourth lens with positive optical power, whose object side is convex and image side is convex; a fifth lens with optical power, whose object side is convex and image side is concave or convex; and a sixth lens with negative optical power, whose object side is concave and image side is convex; wherein the effective focal length f of the optical lens and the entrance pupil diameter EPD of the optical lens satisfy the condition: f / EPD > 2.8. This invention, by rationally allocating the optical power of each lens and rationally setting the surface shape of each lens, enables the optical lens to achieve high image quality while effectively reducing the lens size.

Description

Technical Field

[0001] This invention relates to the field of imaging lens technology, and in particular to an optical lens. Background Technology

[0002] With the development of mobile internet and the popularity of social media, video, and live streaming apps, people's love for photography is growing, and their demands for image quality are becoming more diverse. They require not only high-definition image quality but also a wide field of view to capture expansive, visually impactful scenes. Currently, drones are developing rapidly, winning over many consumers with their unique high-altitude perspective and wide-angle shooting capabilities. Correspondingly, the demand for compatible optical lenses in the drone industry is also increasing.

[0003] Because drones are often used in complex environments such as severe vibration, high pressure, and extreme temperatures, the performance requirements for their optical lenses are extremely high. They must have excellent thermal stability to withstand harsh outdoor conditions, a lightweight design to increase flight time during high-altitude shooting, and a large aperture to ensure clear and vivid images in varying day and night conditions. However, conventional optical lenses currently on the market struggle to meet the diverse needs of drone use. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide an optical lens that has at least the advantages of high imaging quality and small size.

[0005] To achieve the above-mentioned objective, the present invention provides an optical lens, which comprises, from the object side to the imaging plane, the following components in sequence: a first lens with positive optical power, wherein the object side is convex and the image side is concave or convex; a second lens with optical power, wherein the object side is convex or concave and the image side is concave; a third lens with negative optical power, wherein the object side is concave or convex and the image side is concave; a fourth lens with positive optical power, wherein the object side is convex and the image side is convex; a fifth lens with optical power, wherein the object side is convex and the image side is concave or convex; and a sixth lens with negative optical power, wherein the object side is concave and the image side is convex; wherein the effective focal length f of the optical lens and the entrance pupil diameter EPD of the optical lens satisfy the condition: f / EPD > 2.8.

[0006] Compared with the prior art, the optical lens provided by the present invention adopts a combination of six lenses. By rationally allocating the optical power of each lens and rationally setting the surface shape of each lens, the optical lens can effectively reduce the size of the lens while satisfying high image quality. Attached Figure Description

[0007] Figure 1This is a schematic diagram of the structure of an optical lens provided in the first embodiment of the present invention.

[0008] Figure 2 The F-Tanθ distortion curve of the optical lens provided in the first embodiment of the present invention.

[0009] Figure 3 The MTF diagram of the optical lens provided in the first embodiment of the present invention.

[0010] Figure 4 The transverse chromatic aberration diagram of the optical lens provided in the first embodiment of the present invention.

[0011] Figure 5 This is a schematic diagram of the structure of an optical lens provided in the second embodiment of the present invention.

[0012] Figure 6 The F-Tanθ distortion curve of the optical lens provided in the second embodiment of the present invention.

[0013] Figure 7 The MTF diagram of the optical lens provided in the second embodiment of the present invention.

[0014] Figure 8 The transverse chromatic aberration diagram of the optical lens provided in the second embodiment of the present invention.

[0015] Figure 9 This is a schematic diagram of the structure of an optical lens provided in the third embodiment of the present invention.

[0016] Figure 10 The F-Tanθ distortion curve of the optical lens provided in the third embodiment of the present invention.

[0017] Figure 11 The MTF diagram of the optical lens provided in the third embodiment of the present invention.

[0018] Figure 12 The transverse chromatic aberration diagram of the optical lens provided in the third embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Several embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be thorough and complete.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Throughout this specification, the same reference numerals refer to the same elements.

[0021] The present invention provides an optical lens, which includes, from the object side to the imaging plane, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a filter, and the optical centers of each lens are located on the same straight line.

[0022] The first lens has positive optical power, its object-side surface is convex, and its image-side surface is either concave or convex; the second lens has negative or positive optical power, its object-side surface is either convex or concave, and its image-side surface is concave; the third lens has negative optical power, its object-side surface is either concave or convex, and its image-side surface is concave; the fourth lens has positive optical power, its object-side surface is convex, and its image-side surface is convex; the fifth lens has positive or negative optical power, its object-side surface is convex, and its image-side surface is either concave or convex; and the sixth lens has negative optical power, its object-side surface is concave, and its image-side surface is convex.

[0023] In some embodiments, the optical lens further includes an aperture stop, which is disposed between the third lens and the fourth lens, or between the fourth lens and the fifth lens. The position of the aperture stop is not limited to this, as long as it enables the optical lens to have a large aperture characteristic and can meet the shooting requirements of the optical lens in dark environments.

[0024] In some embodiments, the optical lens satisfies the following condition:

[0025] f / EPD > 2.8; (1)

[0026] Where f represents the effective focal length of the optical lens, and EPD represents the entrance pupil diameter of the optical lens. When condition (1) is satisfied, the optical lens can have a large aperture characteristic to meet the shooting requirements in dark environments. Furthermore, the effective focal length f and the entrance pupil diameter EPD of the optical lens can satisfy: 3.0 <f / EPD<4.5。

[0027] In some embodiments, the optical lens satisfies the following condition:

[0028] 1.0 < TTL / f < 1.2; (2)

[0029] Where TTL represents the total optical length of the optical lens, and f represents the effective focal length of the optical lens. When the above condition (2) is satisfied, by limiting the relationship between the total optical length and the effective focal length, the total optical length of the system can be effectively controlled while satisfying the field of view range, thus achieving lens miniaturization. When TTL / f > 1.2, the total optical length of the system is too long, which is not conducive to lens miniaturization; when TTL / f < 1.0, the effective focal length of the system is too long, which is not conducive to satisfying the field of view range of the system and cannot obtain sufficient object space information.

[0030] In some embodiments, the optical lens satisfies the following condition:

[0031] 0.8<EPD×tan(FOV / 2)<1.5; (3)

[0032] Wherein, EPD represents the entrance pupil diameter of the optical lens, and FOV represents the maximum field of view of the optical lens. When the above condition (3) is satisfied, by reasonably controlling the relationship between the entrance pupil diameter of the optical lens and the tangent of the maximum half field of view, it is beneficial to achieve a balance between light transmission and imaging range.

[0033] In some embodiments, the optical lens satisfies the following condition:

[0034] 1.0 < f1 / R1 < 1.8; (4)

[0035] Where f1 represents the effective focal length of the first lens, and R1 represents the radius of curvature of the object side of the first lens. When the above condition (4) is satisfied, the curvature of the object side of the first lens can be reasonably controlled, the light-gathering intensity of the off-axis field of view can be mitigated, the aberration between the off-axis field of view and the central field of view can be reduced, which is beneficial to improving the imaging quality of the optical lens.

[0036] In some embodiments, the optical lens satisfies the following condition:

[0037] -1.5<(R3+R4) / (R3-R4)<-0.5; (5)

[0038] Where R3 represents the radius of curvature of the object side of the second lens, and R4 represents the radius of curvature of the image side of the second lens. When the above condition (5) is satisfied, the shape of the second lens can be reasonably controlled, which is beneficial to reducing the ghosting phenomenon of the optical lens and improving the imaging quality of the optical lens.

[0039] In some embodiments, the optical lens satisfies the following condition:

[0040] -1.0 < (f5 + f4) / f < 3.5; (6)

[0041] Where f4 represents the effective focal length of the fourth lens, f5 represents the effective focal length of the fifth lens, and f represents the effective focal length of the optical lens. When the above condition (6) is satisfied, the focal lengths of the fourth and fifth lenses can be reasonably allocated, which is beneficial to reducing higher-order aberrations and also beneficial to reducing the total optical length of the optical lens.

[0042] In some embodiments, the optical lens satisfies the following condition:

[0043] 0.3 < CT11 / TTL < 0.8; (7)

[0044] Wherein, CT11 represents the air gap on the optical axis between the fifth lens and the sixth lens, and TTL represents the total optical length of the optical lens. When the above condition (7) is satisfied, the back focal length of the optical lens can be reasonably allocated to meet the imaging effect under different object distances, and at the same time, it is beneficial to reduce the total optical length of the optical lens.

[0045] In some embodiments, the optical lens satisfies the following condition:

[0046] -2.0<(R12+R13) / (R12-R13)<-1.0; (8)

[0047] Wherein, R12 represents the radius of curvature of the object side of the sixth lens, and R13 represents the radius of curvature of the image side of the sixth lens. When the above condition (8) is satisfied, the shape of the sixth lens can be reasonably controlled, and the back focus of the optical lens can be reasonably controlled, which is beneficial to the aberration correction of the optical lens and improves the imaging quality of the optical lens.

[0048] In some embodiments, the optical lens satisfies the following condition:

[0049] 0.4 < CT3 / CT4 < 0.5; (9)

[0050] Wherein, CT3 represents the center thickness of the third lens; CT4 represents the center thickness of the fourth lens. When the above condition (9) is satisfied, by reasonably controlling the relationship between the center thickness of the third lens and the center thickness of the fourth lens, it is beneficial to realize the miniaturization of optical lenses.

[0051] In some embodiments, the optical lens satisfies the following condition:

[0052] 0.1 <Nd3-Nd4<0.6; (10)

[0053] -35 <Vd3-Vd4<0; (11)

[0054] Wherein, Nd3 represents the refractive index of the third lens, Nd4 represents the refractive index of the fourth lens, Vd3 represents the Abbe number of the third lens, and Vd4 represents the Abbe number of the fourth lens. The Abbe number is used to represent the dispersion ability of a transparent medium. Generally speaking, the smaller the Abbe number of a lens, the more severe the dispersion; conversely, the larger the Abbe number of a lens, the less severe the dispersion. The refractive index reflects the lens's ability to refract light. Generally speaking, the higher the refractive index, the stronger the refractive ability. When the above conditions (10) and (11) are met, by selecting appropriate lens materials, the third and fourth lens groups can bear part of the optical power of the optical lens, which helps to correct aberrations of the optical lens and improve resolution.

[0055] In some embodiments, the optical lens satisfies the following condition:

[0056] 1E-09<|f2×(dn / dt)2|<3E-09; (12)

[0057] Where f2 represents the effective focal length of the second lens, (dn / dt) 2 This represents the temperature coefficient of the refractive index of the material of the second lens. When the above condition (12) is satisfied, it is beneficial to reduce the sensitivity of the optical lens. At the same time, by controlling the relationship between the focal length of the second lens and the temperature coefficient of the refractive index of the material, it is beneficial to improve the high and low temperature performance of the optical lens.

[0058] In some embodiments, the optical lens satisfies the following condition:

[0059] 1.35 <CT1 / ET1<1.75; (13)

[0060] Wherein, CT1 represents the center thickness of the first lens, and ET1 represents the edge thickness of the first lens. When the above condition (13) is satisfied, by reasonably controlling the relationship between the edge thickness and the center thickness of the first lens, the processing yield of the first lens can be improved while ensuring the resolving power of the optical lens.

[0061] In some embodiments, the optical lens satisfies the following condition:

[0062] 13° <CRA<16°; (14)

[0063] Wherein, CRA represents the incident angle of the principal ray of the optical lens onto the imaging surface at the maximum field of view. When the above condition (14) is satisfied, it can better match the imaging requirements of conventional large CRA chips on the market.

[0064] In some embodiments, the optical lens satisfies the following condition:

[0065] 0.5<(ET1+ET2+ET3+ET4+ET5) / (CT1+CT2+CT3+CT4+CT5)<1.5; (15)

[0066] Wherein, ET1 represents the edge thickness of the first lens, ET2 represents the edge thickness of the second lens, ET3 represents the edge thickness of the third lens, ET4 represents the edge thickness of the fourth lens, ET5 represents the edge thickness of the fifth lens, CT1 represents the center thickness of the first lens, CT2 represents the center thickness of the second lens, CT3 represents the center thickness of the third lens, CT4 represents the center thickness of the fourth lens, and CT5 represents the center thickness of the fifth lens. When the above condition (15) is satisfied, the light rays from the first lens to the fifth lens can converge and bear a specific optical power, which is beneficial to reducing the size of the optical lens and increasing the imaging surface.

[0067] In some embodiments, the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens are all made of glass. Using glass lenses gives the optical lens good thermal stability, improves its applicability at different temperatures, and ensures good image quality under various temperature conditions.

[0068] The present invention will be further described below with reference to several embodiments. In each embodiment, the thickness, radius of curvature, and material selection of each lens in the lens are different; for specific differences, please refer to the parameter tables of each embodiment. The following embodiments are merely preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following embodiments. Any changes, substitutions, combinations, or simplifications made without departing from the innovative points of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention.

[0069] First Embodiment

[0070] Please see Figure 1 The diagram shows a schematic of the structure of an optical lens 100 provided in the first embodiment of the present invention. The optical lens 100 includes, along the optical axis from the object side to the imaging surface S16, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, an aperture stop STO, a fifth lens L5, a sixth lens L6, and a filter G1, and the optical centers of each lens are located on the same straight line.

[0071] Specifically, the first lens L1 has positive optical power, with its object-side surface S1 being convex and its image-side surface S2 being concave; the second lens L2 has negative optical power, with its object-side surface S3 being concave and its image-side surface S4 being concave; the third lens L3 has negative optical power, with its object-side surface S5 being convex and its image-side surface concave; the fourth lens L4 has positive optical power, with its object-side surface S12 being convex and its image-side surface S8 being convex; the fifth lens L5 has positive optical power, with its object-side surface S10 being convex and its image-side surface S11 being convex; the sixth lens L6 has negative optical power, with its object-side surface S12 being concave and its image-side surface S13 being convex; and the filter G1 has an object-side surface S14 and an image-side surface S15. The third lens L3 and the fourth lens L4 form a cemented lens, with their cemented surface S6.

[0072] Please refer to Table 1, which shows the relevant parameters of each lens of the optical lens 100 in this embodiment.

[0073] Table 1

[0074]

[0075] Please see Figure 2 The figure shows the F-Tanθ distortion diagram of the optical lens 100 provided in the first embodiment of the present invention. It can be seen from the figure that the F-Tanθ distortion of the optical lens is small and less than 2%, indicating that the optical lens 100 can effectively correct the F-Tanθ distortion.

[0076] Please see Figure 3 The figure shows the MTF diagram of the optical lens 100 provided in the first embodiment of the present invention. It can be seen from the figure that the MTF value of the optical lens is above 0.45 at a spatial frequency of 157 lp / mm, indicating that the optical lens 100 has a high resolution.

[0077] Please see Figure 4 The figure shows the chromatic aberration diagram of the optical lens 100 provided in the first embodiment of the present invention. It can be seen from the figure that the offset of the chromatic aberration is within ±1μm, indicating that the optical lens 100 can effectively correct the chromatic aberration.

[0078] Second Embodiment

[0079] Please see Figure 5 The diagram shows a schematic of the structure of the optical lens 200 provided in the second embodiment. The optical lens 200 includes, along the optical axis from the object side to the imaging surface S16, the following components in sequence: a first lens L1, a second lens L2, a third lens L3, an aperture stop S10, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a filter G1. The optical centers of each lens are located on the same straight line.

[0080] Specifically, the first lens L1 has positive optical power, with its object-side surface S1 being convex and its image-side surface S2 being concave; the second lens L2 has negative optical power, with its object-side surface S3 being concave and its image-side surface S4 being concave; the third lens L3 has negative optical power, with its object-side surface S5 being convex and its image-side surface S6 being concave; the fourth lens L4 has positive optical power, with its object-side surface S8 being convex and its image-side surface S9 being convex; the fifth lens L5 has positive optical power, with its object-side surface S10 being convex and its image-side surface S11 being concave; the sixth lens L6 has negative optical power, with its object-side surface S12 being concave and its image-side surface S13 being convex; and the filter G1 has an object-side surface S14 and an image-side surface S15.

[0081] Please refer to Table 2, which shows the relevant parameters of each lens element of the optical lens 200 in this embodiment.

[0082] Table 2

[0083]

[0084] Please see Figure 6 The figure shows the F-Tanθ distortion diagram of the optical lens 200 provided in the second embodiment of the present invention. It can be seen from the figure that the F-Tanθ distortion of the optical lens is small and less than 2%, indicating that the optical lens 200 can effectively correct the F-Tanθ distortion.

[0085] Please see Figure 7 The figure shows the MTF diagram of the optical lens 200 provided in the second embodiment of the present invention. It can be seen from the figure that the MTF value of the optical lens is above 0.5 at a spatial frequency of 157 lp / mm, indicating that the optical lens 200 has a high resolution.

[0086] Please see Figure 8 The figure shows the lateral chromatic aberration diagram of the optical lens 200 provided in the second embodiment of the present invention. It can be seen from the figure that the offset of the lateral chromatic aberration is within ±1μm, indicating that the optical lens 200 can effectively correct field curvature.

[0087] Third Embodiment

[0088] Please see Figure 9 The figure shown is a schematic diagram of the structure of the optical lens 300 provided in the third embodiment. The optical lens 300 includes, along the optical axis from the object side to the imaging surface S16, the following components in sequence: a first lens L1, a second lens L2, a third lens L3, an aperture stop STO, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a filter G1, and the optical centers of each lens are located on the same straight line.

[0089] Specifically, the first lens L1 has positive optical power, with its object-side surface S1 being convex and its image-side surface S2 being convex; the second lens L2 has positive optical power, with its object-side surface S3 being convex and its image-side surface S4 being concave; the third lens L3 has negative optical power, with its object-side surface S5 being concave and its image-side surface S6 being concave; the fourth lens L4 has positive optical power, with its object-side surface S8 being convex and its image-side surface S9 being convex; the fifth lens L5 has negative optical power, with its object-side surface S10 being convex and its image-side surface S11 being concave; the sixth lens L6 has negative optical power, with its object-side surface S12 being concave and its image-side surface S13 being convex; and the filter G1 has an object-side surface S14 and an image-side surface S15.

[0090] Please refer to Table 3, which shows the relevant parameters of each lens of the optical lens 300 in this embodiment.

[0091] Table 3

[0092]

[0093] Please see Figure 10 The figure shows the F-Tanθ distortion diagram of the optical lens 300 provided in the third embodiment of the present invention. It can be seen from the figure that the F-Tanθ distortion of the optical lens is small and less than 2%, indicating that the optical lens 300 can effectively correct the F-Tanθ distortion.

[0094] Please see Figure 11 The figure shows the MTF diagram of the optical lens 300 provided in the third embodiment of the present invention. It can be seen from the figure that the MTF value of the optical lens is above 0.5 at a spatial frequency of 157 lp / mm, indicating that the optical lens 300 has a high resolution.

[0095] Please see Figure 12 The figure shows the lateral chromatic aberration diagram of the optical lens 300 provided in the third embodiment of the present invention. It can be seen from the figure that the offset of the lateral chromatic aberration is within ±1μm, indicating that the optical lens 300 can effectively correct field curvature.

[0096] Please refer to Table 4, which shows the optical characteristics of each optical lens in the three embodiments above, including the maximum field of view (FOV), image height (IH), total optical length (TTL), effective focal length (f), and the relevant values ​​corresponding to each condition in the above conditions.

[0097] Table 4

[0098]

[0099] Compared with the prior art, the optical lens provided by the present invention has at least the following advantages:

[0100] 1. The optical lens provided by the present invention significantly reduces the total length and volume of the optical lens by reasonably allocating the optical power of each lens and reasonably setting the thickness of each lens and the spacing between each lens, thereby improving the applicability of the optical lens.

[0101] 2. The optical lens provided by the present invention adopts a six-glass lens structure, which enables the optical lens to have good thermal stability, improves the applicability of the optical lens at different temperatures, and can obtain good image quality under different temperature conditions.

[0102] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0103] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. An optical lens, characterized in that, There are a total of six lenses with optical power, arranged sequentially along the optical axis from the object side to the image plane: A first lens having positive optical power, wherein the object side of the first lens is convex; A second lens with optical power; A third lens with negative optical power, wherein the image-side surface of the third lens is concave; A fourth lens with positive optical power; A fifth lens with optical power, wherein the object side of the fifth lens is convex; A sixth lens with negative optical power; The effective focal length f of the optical lens and the entrance pupil diameter EPD of the optical lens satisfy the condition: 2.8 < f / EPD < 4.

5.

2. The optical lens according to claim 1, characterized in that, It also includes an aperture stop, which is located between the third lens and the fourth lens.

3. The optical lens according to claim 1, characterized in that, It also includes an aperture stop, which is disposed between the fourth lens and the fifth lens.

4. The optical lens according to claim 3, characterized in that, The third lens and the fourth lens together form a cemented lens.

5. The optical lens according to claim 1, characterized in that, The optical lens satisfies the following condition: 1.0 < TTL / f < 1.2; Wherein, TTL represents the total optical length of the optical lens, and f represents the effective focal length of the optical lens.

6. The optical lens according to claim 1, characterized in that, The optical lens satisfies the following condition: 0.8<EPD×tan(FOV / 2)<1.5; Wherein, EPD represents the entrance pupil diameter of the optical lens, and FOV represents the maximum field of view of the optical lens.

7. The optical lens according to claim 1, characterized in that, The optical lens satisfies the following condition: 1.0 < f1 / R1 < 1.8; Where f1 represents the effective focal length of the first lens, and R1 represents the radius of curvature of the object side surface of the first lens.

8. The optical lens according to claim 1, characterized in that, The optical lens satisfies the following condition: -1.5<(R3+R4) / (R3-R4)<-0.5; Wherein, R3 represents the radius of curvature of the object side of the second lens, and R4 represents the radius of curvature of the image side of the second lens.

9. The optical lens according to claim 1, characterized in that, The optical lens satisfies the following condition: -1.0 < (f5 + f4) / f < 3.5; Where f4 represents the effective focal length of the fourth lens, f5 represents the effective focal length of the fifth lens, and f represents the effective focal length of the optical lens.

10. The optical lens according to claim 1, characterized in that, The optical lens satisfies the following condition: 0.3 <CT11 / TTL<0.8; Wherein, CT11 represents the air gap on the optical axis between the fifth lens and the sixth lens, and TTL represents the total optical length of the optical lens.

11. The optical lens according to claim 1, characterized in that, The optical lens satisfies the following condition: -2.0<(R12+R13) / (R12-R13)<-1.0; Wherein, R12 represents the radius of curvature of the object side of the sixth lens, and R13 represents the radius of curvature of the image side of the sixth lens.

12. The optical lens according to claim 1, characterized in that, The optical lens satisfies the following condition: 0.4 < CT3 / CT4 < 0.5; Wherein, CT3 represents the center thickness of the third lens; CT4 represents the center of the fourth lens; The image-side surface of the second lens is concave; the object-side surface of the fourth lens is convex, and the image-side surface is convex; the object-side surface of the sixth lens is concave, and the image-side surface is convex.

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