Optical lens

Abstract

The present invention provides an optical lens, which is composed of four lenses. Along the optical axis from the object side to the imaging surface, it sequentially includes: a first lens with a positive optical power, whose object side is convex and whose image side is concave; a second lens with a negative optical power, whose object side is concave and whose image side is convex; a third lens with a negative optical power, whose object side is concave and whose image side is convex; a fourth lens with a positive optical power, whose object side is convex and whose image side is concave; the true image height IH corresponding to the maximum field of view angle of the optical lens and the entrance pupil diameter EPD of the optical lens satisfy: 7.5 < IH / EPD < 9.3; the curvature radius R3 of the object side of the second lens and the curvature radius R4 of the image side of the second lens satisfy: -1 < (R3 - R4) / (R3 + R4) < -0.2. The optical lens provided by the present invention can improve the imaging quality of the optical lens, reduce aberration, and improve the imaging quality of the optical lens through specific surface shape matching and reasonable optical power distribution.

Description

Technical Field

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

[0002] With the development of information technology, barcodes and two-dimensional codes are widely used in fields such as retail, logistics, and industrial automation. To improve the scanning speed and accuracy, the performance requirements of scanning devices are constantly increasing. As a key component of scanning devices, the performance of optical lenses directly affects the image quality and recognition accuracy. However, the existing optical lenses for scanning devices have the following main problems: 1. Poor imaging quality: Traditional optical lenses are prone to chromatic aberration and aberration when processing multi-band light, resulting in image distortion. 2. Volume and weight limitations: Portable and handheld scanning devices have strict requirements for the volume and weight of lenses, and traditional lenses are difficult to meet this demand.

[0003] Therefore, there is an urgent need for a new type of optical lens that can solve the above problems to improve the performance and user experience of scanning devices. Summary of the Invention

[0004] In view of the above problems, the object of the present invention is to provide an optical lens with excellent imaging quality.

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

[0006] An optical lens is composed of four lenses, and sequentially includes from the object side to the imaging surface along the optical axis:

[0007] A first lens with positive optical power, whose object side is convex and whose image side is concave;

[0008] A second lens with negative optical power, whose object side is concave and whose image side is convex;

[0009] A third lens with negative optical power, whose object side is concave and whose image side is convex;

[0010] A fourth lens with positive optical power, whose object side is convex and whose image side is concave;

[0011] Wherein, the true image height IH corresponding to the maximum field of view angle of the optical lens and the entrance pupil diameter EPD of the optical lens satisfy: 7.5 < IH / EPD < 9.3; the curvature radius R3 of the object side of the second lens and the curvature radius R4 of the image side of the second lens satisfy: -1 < (R3 - R4) / (R3 + R4) < -0.2.

[0012] More preferably, the total optical length TTL of the optical lens and the effective focal length f of the optical lens satisfy: 1.3 < TTL / f < 1.6; the true image height IH corresponding to the maximum field of view angle of the optical lens and the effective focal length f of the optical lens satisfy: 1.6 < IH / f < 2.2.

[0013] More preferably, the entrance pupil diameter EPD of the optical lens and the maximum field of view angle FOV of the optical lens satisfy: 0.45 mm < EPD × Tan(FOV / 2) < 0.65 mm; the back focal length BFL of the optical lens and the total optical length TTL of the optical lens satisfy: 0.4 < BFL / TTL < 0.55.

[0014] More preferably, the effective focal length f of the optical lens and the focal length f1 of the first lens satisfy: 0.9 < f1 / f < 1.3; the effective focal length f of the optical lens and the image-side curvature radius R2 of the first lens satisfy: 0.8 < R2 / f < 5.7.

[0015] More preferably, the effective focal length f of the optical lens and the focal length f3 of the third lens satisfy: -36.7 < f3 / f < -3.3; the object-side curvature radius R5 of the third lens and the image-side curvature radius R6 of the third lens satisfy: -0.3 < (R5 - R6) / (R5 + R6) < 0.

[0016] More preferably, the effective focal length f of the optical lens and the focal length f4 of the fourth lens satisfy: 1.15 < f4 / f < 2.4; the image-side clear aperture semi-diameter d6 of the third lens and the object-side clear aperture semi-diameter d7 of the fourth lens satisfy: 0.4 < d6 / d7 < 0.6.

[0017] More preferably, the focal length f1 of the first lens and the combined focal length f234 of the second lens, the third lens and the fourth lens satisfy: 0 < f1 / f234 < 0.5; the object-side clear aperture semi-diameter d1 of the first lens and the true image height IH corresponding to the maximum field of view angle of the optical lens satisfy: 0.15 < d1 / (IH / 2) < 0.3.

[0018] More preferably, the focal length f2 of the second lens and the focal length f3 of the third lens satisfy: 0 < f2 / f3 < 0.8; the image-side curvature radius R4 of the second lens and the object-side curvature radius R5 of the third lens satisfy: R4 / R5 > 10.8.

[0019] Further preferably, the effective focal length f of the optical lens and the curvature radius R3 of the object side surface of the second lens satisfy: -1.4 < R3 / f < -0.9; the effective focal length f of the optical lens and the curvature radius R4 of the image side surface of the second lens satisfy: -24.9 < R4 / f < -2.25.

[0020] Further preferably, the sagittal height Sag3 of the clear aperture of the object side surface of the second lens and the clear aperture diameter d3 of the object side surface of the second lens satisfy: -0.2 < Sag3 / d3 < 0; the sagittal height Sag4 of the clear aperture of the image side surface of the second lens and the clear aperture diameter d4 of the image side surface of the second lens satisfy: -0.1 < Sag4 / d4 < 0.1.

[0021] Compared with the prior art, the optical lens provided by the present invention can effectively shorten the overall length of the optical lens through specific surface shape settings and reasonable optical power distribution. The object side surface of the first lens is convex, which helps to converge the incident light, reduces the aperture of the front lens, and is beneficial to the miniaturization of the head. At the same time, the lens has a small aperture. Through the design of a large F-number and a small aperture, a long depth of field range can be achieved while ensuring the imaging quality of the lens. When the image moves within a long range, the image can also be accurately captured. In addition, it can reasonably correct the overall aberration of the optical lens, has small distortion, can achieve high-definition imaging, and improves the imaging quality of the optical lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the following description of the embodiments in conjunction with the accompanying drawings, where:

[0023] Figure 1 is a schematic structural diagram of the optical lens in Embodiment 1 of the present invention.

[0024] Figure 2 is an astigmatism curve diagram of the optical lens in Embodiment 1 of the present invention.

[0025] Figure 3 is an F-Tan(Theta) distortion curve diagram of the optical lens in Embodiment 1 of the present invention.

[0026] Figure 4 is an axial aberration curve diagram of the optical lens in Embodiment 1 of the present invention.

[0027] Figure 5 is a lateral chromatic aberration curve diagram of the optical lens in Embodiment 1 of the present invention.

[0028] Figure 6 is a schematic structural diagram of the optical lens in Embodiment 2 of the present invention.

[0029] Figure 7Graph showing the astigmatism of the optical lens in Embodiment 2 of the present invention.

[0030] Figure 8 Graph showing the F-Tan (Theta) distortion of the optical lens in Example 2 of the present invention.

[0031] Fig. 9 Graph showing the axial aberration of the optical lens in Embodiment 2 of the present invention.

[0032] Fig.10 Graph showing the vertical axis chromatic aberration of the optical lens in Example 2 of the present invention.

[0033] Fig.11 Schematic diagram of the structure of the optical lens in Example 3 of the present invention.

[0034] Fig.12 4 is an astigmatism curve diagram of the optical lens in Example 3 of the present invention.

[0035] Fig.13 Graph showing the F-Tan (Theta) distortion of the optical lens in Example 3 of the present invention.

[0036] Fig.14 Graph showing the axial aberration of the optical lens in Embodiment 3 of the present invention.

[0037] Fig.15 Graph showing the vertical axis chromatic aberration of the optical lens in Example 3 of the present invention.

[0038] Fig.16 Schematic diagram of the structure of the optical lens in Example 4 of the present invention.

[0039] Fig.17 4 is an astigmatism curve diagram of the optical lens in Example 4 of the present invention.

[0040] Fig.18 4 is a F-Tan (Theta) distortion curve of the optical lens in Example 4 of the present invention.

[0041] Fig.19 4 is an axial aberration curve diagram of the optical lens in Example 4 of the present invention.

[0042] Fig. 20 Graph showing the vertical axis chromatic aberration of the optical lens in Example 4 of the present invention.

[0043] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0044] In order to better understand the present application, a more detailed description will be made of various aspects of the present application with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of the embodiments of the present application, and are not intended to limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0045] It should be noted that in this specification, the expressions of first, second, third, etc. are only used to distinguish one feature from another feature, and do not represent any limitation on the features. Therefore, without departing from the teaching of the present invention, the first lens discussed below may also be referred to as the second lens or the third lens.

[0046] In the drawings, the thickness, size and shape of the lenses have been slightly exaggerated for ease of explanation. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to the shapes of the spherical or aspherical surfaces shown in the drawings. The drawings are only examples and are not drawn strictly to scale.

[0047] In this article, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the object is called the object side of the lens, and the surface of each lens closest to the imaging plane is called the image side of the lens.

[0048] It should also be understood that the terms "comprises", "including", "having", "includes" and / or "comprising", when used in this specification, indicate the presence of the stated features, elements and / or components, but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof. In addition, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire listed features rather than modifying the individual elements in the list. In addition, when describing embodiments of the present application, "may" is used to mean "one or more embodiments of the present application". And, the term "exemplary" is intended to refer to an example or illustration.

[0049] Unless otherwise defined, all terms (including technical terms and scientific terms) used in this article have the same meaning as commonly understood by ordinary technicians in the field to which this application belongs. It should also be understood that terms (such as terms defined in commonly used dictionaries) should be interpreted as having the same meaning as their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined in this article.

[0050] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other. The following will describe the present application in detail with reference to the accompanying drawings and in conjunction with the embodiments.

[0051] The optical lens provided by the embodiment of the present invention is composed of four lenses, which are, in order from the object side to the imaging surface along the optical axis, a first lens, a second lens, a third lens, and a fourth lens.

[0052] In some embodiments, the first lens may have a positive optical power, its object side surface is convex, and its image side surface is concave. The second lens may have a negative optical power, its object side surface is concave, and its image side surface is convex. The third lens may have a negative optical power, its object side surface is concave, and its image side surface is convex. The fourth lens may have a positive optical power, its object side surface is convex, and its image side surface is concave.

[0053] In some embodiments, the optical lens may further include a diaphragm for restricting the light beam. The diaphragm may be located between the first lens and the second lens, which can reduce the generation of ghost images of the optical lens and effectively reduce the difficulty of distortion correction of the lens at the same time.

[0054] In some embodiments, the optical lens may further include a filter. The filter may be disposed between the fourth lens and the imaging surface. The filter is used to filter out interfering light to prevent the interfering light from reaching the imaging surface of the optical lens and affecting normal imaging.

[0055] In some embodiments, the true image height IH corresponding to the maximum field of view angle of the optical lens and the entrance pupil diameter EPD of the optical lens satisfy: 7.5 < IH / EPD < 9.3. Meeting the above range can better highlight the object to be photographed, blur the background, and achieve high-definition imaging of the object to be photographed within a specific distance. More specifically, 7.92 < IH / EPD < 8.5.

[0056] In some embodiments, the curvature radius R3 of the object side surface of the second lens and the curvature radius R4 of the image side surface of the second lens satisfy: -1 < (R3 - R4) / (R3 + R4) < -0.2. Meeting the above range can effectively slow down the deflection degree of the light entering the second lens, which is beneficial to maintaining the miniaturization of the lens head and increasing the light flux entering the lens at the same time. More specifically, -0.9 < (R3 - R4) / (R3 + R4) < -0.43.

[0057] In some embodiments, the overall optical length TTL of the optical lens and the effective focal length f of the optical lens satisfy: 1.3 < TTL / f < 1.6. Meeting the above range can reasonably control the ratio of the overall length to the effective focal length of the optical lens, so that the optical lens has a shorter overall length while achieving telephoto performance. More specifically, 1.34 < TTL / f < 1.45.

[0058] In some embodiments, the true image height IH corresponding to the maximum field of view angle of the optical lens and the effective focal length f of the optical lens satisfy: 1.6 < IH / f < 2.2. Meeting the above range can achieve the large image plane characteristic of the lens, can match a larger size of the chip, and realize high-pixel imaging of the lens. More specifically, 1.79 < IH / f < 2.08.

[0059] In some embodiments, the entrance pupil diameter EPD of the optical lens and the maximum field of view angle FOV of the optical lens satisfy: 0.45 mm < EPD × Tan(FOV / 2) < 0.65 mm. Meeting the above range is beneficial to achieving the balance of the light transmission amount and the imaging range by reasonably controlling the relationship between the entrance pupil diameter of the optical lens and the tangent value of the maximum half field of view angle. More specifically, 0.52 mm < EPD × Tan(FOV / 2) < 0.58 mm.

[0060] In some embodiments, the back focal length BFL of the optical lens and the total optical length TTL of the optical lens satisfy: 0.4 < BFL / TTL < 0.55. Meeting the above range makes the lens have a larger back focus, which is beneficial to the assembly of the module, reduces interference, and improves the production yield. More specifically, 0.4 < BFL / TTL < 0.46.

[0061] In some embodiments, the effective focal length f of the optical lens and the focal length f1 of the first lens satisfy: 0.9 < f1 / f < 1.3; the effective focal length f of the optical lens and the curvature radius R2 of the image side surface of the first lens satisfy: 0.8 < R2 / f < 5.7. Meeting the above range can make the incident light converge to a greater extent and allow more light to enter the system by setting the first lens to have a larger positive refractive power and the image side surface to be concave, which is beneficial to improving the light input amount of the lens and enabling the lens to achieve high-definition imaging in a darker environment. More specifically, 0.95 < f1 / f < 1.15; 0.9 < R2 / f < 5.2.

[0062] In some embodiments, the effective focal length f of the optical lens and the focal length f3 of the third lens satisfy: -36.7 < f3 / f < -3.3; the curvature radius R5 of the object side surface of the third lens and the curvature radius R6 of the image side surface of the third lens satisfy: -0.3 < (R5 - R6) / (R5 + R6) < 0. Meeting the above range is beneficial to the smooth transition of light, better corrects the aberration and distortion brought by the front lens, and improves the overall imaging quality. More specifically, -33.43 < f3 / f < -3.64; -0.15 < (R5 - R6) / (R5 + R6) < -0.07.

[0063] In some embodiments, the effective focal length f of the optical lens and the focal length f4 of the fourth lens satisfy: 1.15 < f4 / f < 2.4. Meeting the above range, which defines that the fourth lens has an appropriate positive optical power, is conducive to converging light rays and helps to reduce the aberration of the optical lens. More specifically, 1.26 < f4 / f < 2.17.

[0064] In some embodiments, the semi-aperture d6 of the image side of the third lens and the semi-aperture d7 of the object side of the fourth lens satisfy: 0.4 < d6 / d7 < 0.6. Meeting the above range, by controlling the aperture ratio, the light ray trend is restricted within a reasonable range, making the illuminance of the imaging surface uniform. More specifically, 0.46 < d6 / d7 < 0.54.

[0065] In some embodiments, the focal length f1 of the first lens and the combined focal length f234 of the second, third, and fourth lenses satisfy: 0 < f1 / f234 < 0.5. Meeting the above range, by reasonably setting the focal length relationship between the front and rear lens groups, it helps the smooth transition of light rays, reduces the difficulty of correcting aberration of the rear-end lens, and improves the image quality of the optical imaging lens. More specifically, 0.07 < f1 / f234 < 0.45.

[0066] In some embodiments, the semi-aperture d1 of the object side of the first lens and the true image height IH corresponding to the maximum field angle of the optical lens satisfy: 0.15 < d1 / (IH / 2) < 0.3. Meeting the above range can balance the small aperture at the front end of the optical lens and the image plane, which is conducive to the miniaturization of the optical lens. More specifically, 0.18 < d1 / (IH / 2) < 0.27.

[0067] In some embodiments, the focal length f2 of the second lens and the focal length f3 of the third lens satisfy: 0 < f2 / f3 < 0.8; the radius of curvature R4 of the image side of the second lens and the radius of curvature R5 of the object side of the third lens satisfy: R4 / R5 > 10.8. Meeting the above range can reduce the deflection angle of light rays and make the light ray trend smoother; at the same time, it can correct coma and field curvature, improve the flatness of imaging, and enhance the imaging quality of the optical lens. More specifically, 0.05 < f2 / f3 < 0.72; 12.08 < R4 / R5 < 90.36.

[0068] In some embodiments, the effective focal length f of the optical lens and the radius of curvature R3 of the object side surface of the second lens satisfy: -1.4 < R3 / f < -0.9; the effective focal length f of the optical lens and the radius of curvature R4 of the image side surface of the second lens satisfy: -24.9 < R4 / f < -2.25. Meeting the above ranges, by controlling the surface shape of the second lens, the deflection degree of light entering the second lens can be effectively reduced, which is beneficial to maintaining the miniaturization of the lens head. More specifically, -1.29 < R3 / f < -1; -22.69 < R4 / f < -2.52.

[0069] In some embodiments, the sagittal height Sag3 of the clear aperture of the object side surface of the second lens and the clear aperture d3 of the object side surface of the second lens satisfy: -0.2 < Sag3 / d3 < 0; the sagittal height Sag4 of the clear aperture of the image side surface of the second lens and the clear aperture d4 of the image side surface of the second lens satisfy: -0.1 < Sag4 / d4 < 0.1. Meeting the above ranges helps to control the trend of light in the marginal field of view and highlight the detailed information of the central field of view of the optical lens. More specifically, -0.11 < Sag3 / d3 < -0.07; -0.03 < Sag4 / d4 < 0.04.

[0070] In some embodiments, the overall optical length TTL of the optical lens and the true image height IH corresponding to the maximum field of view angle of the optical lens satisfy: 0.6 < TTL / IH < 0.9. Meeting the above ranges, by reasonably restricting the ratio of the overall length of the optical lens to the image height, it is ensured that the lens has a larger image plane under the same overall length, achieving the balance between the miniaturization of the optical lens and the large image plane, and improving the market competitiveness. More specifically, 0.65 < TTL / IH < 0.81.

[0071] In some embodiments, the maximum field of view angle FOV of the optical lens and the f-number Fno of the optical lens satisfy: 17° < FOV / Fno < 24°. Meeting the above ranges, it is defined that the optical lens has a suitable field of view angle and f-number, and can collect light at a large angle and obtain good imaging quality. More specifically, 18.76° < FOV / Fno < 21.96°.

[0072] In some embodiments, the back focal length BFL of the optical lens and the effective focal length f of the optical lens satisfy: 0.5 < BFL / f < 0.7. Meeting the above ranges is beneficial to achieving a balance between obtaining good imaging quality and an optical back focal length that is easy to assemble, ensuring the imaging quality of the optical lens while reducing the assembly process difficulty of the camera module. More specifically, 0.54 < BFL / f < 0.62.

[0073] In some embodiments, the total optical length TTL of the optical lens and the sum ∑CT of the central thicknesses of the first lens to the fourth lens along the optical axis satisfy: 0.35 < ∑CT / TTL < 0.5. Satisfying the above range can effectively compress the total length of the optical lens, and at the same time is beneficial to the structural design and production process of the optical lens. More specifically, 0.39 < ∑CT / TTL < 0.43.

[0074] In some embodiments, the effective focal length f of the optical lens and the sum ∑CT of the central thicknesses of the first lens to the fourth lens along the optical axis satisfy: 0.45 < ∑CT / f < 0.65. Satisfying the above range, by reasonably distributing the central thicknesses of each lens, the manufacturing yield of the optical lens can be improved, and at the same time it helps to shorten the total length of the optical lens, maintain its miniaturization, so as to be conducive to application in portable and handheld scanning devices. More specifically, 0.54 < ∑CT / f < 0.6.

[0075] In some embodiments, the effective focal length f of the optical lens and the focal length f2 of the second lens satisfy: -2.85 < f2 / f < -1.9. Satisfying the above range makes the second lens have a negative optical power, which is beneficial to the smooth transition of light and improves the imaging resolution. -2.61 < f2 / f < -2.1.

[0076] In some embodiments, the radius of curvature R5 of the object side surface of the third lens and the effective focal length f of the optical lens satisfy: -0.35 < R5 / f < -0.15; the radius of curvature R6 of the image side surface of the third lens and the effective focal length f of the optical lens satisfy: -0.4 < R6 / f < -0.2. Satisfying the above range, by reasonably setting the shape of the third lens, it is beneficial to balance various aberrations of the lens, improve the imaging quality of the optical lens, and at the same time reduce the processing difficulty of the third lens and improve the processability. More specifically, -0.27 < R5 / f < -0.2; -0.32 < R6 / f < -0.27.

[0077] In some embodiments, the radius of curvature R7 of the object side surface of the fourth lens and the effective focal length f of the optical lens satisfy: 0.2 < R7 / f < 0.5; the radius of curvature R8 of the image side surface of the fourth lens and the effective focal length f of the optical lens satisfy: 0.2 < R8 / f < 0.7. Satisfying the above range is beneficial to balance various aberrations of the lens, improve the imaging quality of the optical lens, and at the same time reduce the processing difficulty of the fourth lens and improve the processability. More specifically, 0.31 < R7 / f < 0.39; 0.34 < R8 / f < 0.58.

[0078] In some embodiments, the optical lens satisfies the conditional formula: 2.1mm < f < 2.9mm, 0.5mm < EPD < 0.7mm, 2.8mm < TTL < 4.2mm, 3.7 < Fno < 4.8, 24.5° < CRA < 36.8°, 1.2mm < BFL < 1.8mm, 75° < FOV < 95°, 4.2mm < IH < 5.2mm; where f represents the effective focal length of the optical lens, EPD represents the entrance pupil diameter of the optical lens, TTL represents the total optical length of the optical lens, Fno represents the aperture value of the optical lens, CRA represents the chief ray angle of incidence at the maximum image height of the optical lens, BFL represents the back focal length of the optical lens, FOV represents the maximum field of view angle of the optical lens, and IH represents the true image height corresponding to the maximum field of view angle of the optical lens. Meeting the above conditions indicates that the optical lens provided by the embodiments of the present invention has at least the characteristics of a small aperture, a large depth of field, and a short total length. More specifically, 4.88mm < f < 5.1mm, 4.65mm < EPD < 4.86mm, 29.8mm < TTL < 30.2mm, 1.04 < Fno < 1.06, 10.86° < CRA < 15.37°, 4.49mm < BFL < 5.55mm, 106.12° < FOV < 112.03°, 9.1mm < IH < 9.3mm.

[0079] In some embodiments, the first lens, the second lens, the third lens, and the fourth lens may adopt spherical lenses or aspherical lenses. Compared with the spherical structure, the aspherical structure can effectively reduce the aberration of the optical system, thereby reducing the number of lenses and the size of the lenses, and better realizing the miniaturization of the lens. More specifically, the first lens, the second lens, the third lens, and the fourth lens of the present invention may adopt aspherical lenses.

[0080] In some embodiments, the lens material of the optical lens provided by the present invention may be glass or plastic. When the lens material is plastic, the production cost can be effectively reduced. When the lens material is glass, the geometric chromatic aberration of the optical system can be effectively corrected by the low dispersion characteristics of the glass itself. More specifically, the first lens, the second lens, the third lens, and the fourth lens of the present invention may be plastic lenses.

[0081] In each embodiment of the present invention, when the lens adopts an aspherical lens, the aspherical surface shapes of the optical lens satisfy the following equation:

[0082] ;

[0083] Among them, z is the distance between the surface and the vertex of the surface in the direction of the optical axis, h is the distance from the optical axis to the surface, c is the curvature of the surface vertex, K is the quadratic surface coefficient, B, C, D, E, F, G, and H are the fourth-order, sixth-order, eighth-order, tenth-order, twelfth-order, fourteenth-order, and sixteenth-order surface coefficients respectively.

[0084] The present invention is further described below in multiple embodiments. In each embodiment, the thickness, radius of curvature, and material selection of each lens in the optical lens are different. For specific differences, please refer to the parameter table of each embodiment. The following embodiments are only preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following embodiments. Any other changes, substitutions, combinations or simplifications that do not deviate from the innovative points of the present invention should be regarded as equivalent replacement methods and are included in the protection scope of the present invention.

[0085] Example 1

[0086] See also Figure 1 , which is a schematic diagram of the structure of the optical lens 100 provided in Embodiment 1 of the present invention, wherein the optical lens includes, in sequence from the object side to the imaging surface along the optical axis: a first lens L1, an aperture ST, a second lens L2, a third lens L3, a fourth lens L4 and a filter G1.

[0087] The first lens L1 has positive refractive power, its object side surface S1 is convex, and its image side surface S2 is concave;

[0088] The second lens L2 has negative refractive power, its object side surface S3 is concave, and its image side surface S4 is convex;

[0089] The third lens L3 has negative refractive power, its object-side surface S5 is concave, and its image-side surface S6 is convex;

[0090] The fourth lens L4 has positive refractive power, its object-side surface S7 is convex, and its image-side surface S8 is concave;

[0091] The object side surface S9 and the image side surface S10 of the filter G1 are both planes;

[0092] The imaging surface S11 is a plane.

[0093] The first lens L1, the second lens L2, the third lens L3 and the fourth lens L4 are plastic aspherical lenses.

[0094] The relevant parameters of each lens in the optical lens 100 in Example 1 are shown in Table 1-1.

[0095] Table 1-1

[0096]

[0097] The surface parameters of the aspheric lens of the optical lens 100 in Example 1 are shown in Table 1-2.

[0098] Table 1-2

[0099]

[0100] In this embodiment, the astigmatism curve, F-Tan (Theta) distortion curve, axial aberration curve, and vertical chromatic aberration curve of the optical lens 100 are respectively as follows: Figure 2 , Figure 3 , Figure 4 , Figure 5 shown.

[0101] Figure 2 The astigmatism curve of Example 1 is shown, which represents the astigmatism of light of different wavelengths on the meridional image plane and the sagittal image plane, the horizontal axis represents the offset (unit: mm), and the vertical axis represents the half field angle (unit: °). It can be seen from the figure that the astigmatism of the meridional image plane and the sagittal image plane is controlled within ±0.2mm, indicating that the optical lens 100 can correct the astigmatism well.

[0102] Figure 3 The F-Tan (Theta) distortion curve of Example 1 is shown, which represents the distortion of different field angles on the imaging plane, with the horizontal axis representing the distortion value (unit: %) and the vertical axis representing the half field angle (unit: °). It can be seen from the figure that the distortion value is controlled within ±1%, indicating that the optical lens 100 can correct the distortion well.

[0103] Figure 4 The axial aberration curve of Example 1 is shown, which represents the aberration of each wavelength on the optical axis at the imaging surface, the horizontal axis represents the axial aberration value (unit: mm), and the vertical axis represents the normalized pupil radius. As can be seen from the figure, the offset of the axial aberration is controlled within ±0.04mm, indicating that the optical lens 100 can better correct the axial aberration.

[0104] Figure 5 The vertical axis chromatic aberration curve of Example 1 is shown, which represents the chromatic aberration of each wavelength relative to the central wavelength (0.588 μm) at different image heights on the imaging surface, the horizontal axis represents the vertical axis chromatic aberration value of each wavelength relative to the central wavelength (unit: μm), and the vertical axis represents the normalized field angle. It can be seen from the figure that the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ±2 μm, indicating that the optical lens 100 can correct chromatic aberration well.

[0105] Example 2

[0106] See also Figure 6, shown is a schematic diagram of the structure of the optical lens 200 provided in Example 2 of the present invention. Compared with Example 1, the main difference between this embodiment and Example 1 is that the optical parameters such as the curvature radius of each lens surface and the lens thickness are different.

[0107] The relevant parameters of each lens in the optical lens 200 in Example 2 are shown in Table 2-1.

[0108] Table 2-1

[0109]

[0110] The surface parameters of the aspheric lens of the optical lens 200 in Example 2 are shown in Table 2-2.

[0111] Table 2-2

[0112]

[0113] In this embodiment, the astigmatism curve, F-Tan (Theta) distortion curve, axial aberration curve, and vertical chromatic aberration curve of the optical lens 200 are respectively as follows: Figure 7 , Figure 8 , Fig. 9 , Fig.10 shown.

[0114] from Figure 7 It can be seen that the astigmatism of the meridional image plane and the sagittal image plane is controlled within ±0.1 mm, indicating that the optical lens 200 can correct the astigmatism well.

[0115] from Figure 8 It can be seen that the distortion value is controlled within ±1%, indicating that the optical lens 200 can correct the distortion well.

[0116] from Fig. 9 It can be seen that the offset of the axial aberration is controlled within ±0.02 mm, indicating that the optical lens 200 can correct the axial aberration well.

[0117] from Fig.10 It can be seen that the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ±2μm, indicating that the optical lens 200 can correct chromatic aberration well.

[0118] Example 3

[0119] See also Fig.11 , shown is a schematic diagram of the structure of the optical lens 300 provided in Example 3 of the present invention. Compared with Example 1, the main difference between this embodiment and Example 1 is that the optical parameters such as the curvature radius of each lens surface and the lens thickness are different.

[0120] The relevant parameters of each lens in the optical lens 300 in Example 3 are shown in Table 3-1.

[0121] Table 3-1

[0122]

[0123] The surface parameters of the aspheric lens of the optical lens 300 in Example 3 are shown in Table 3-2.

[0124] Table 3-2

[0125]

[0126] In this embodiment, the astigmatism curve, F-Tan (Theta) distortion curve, axial aberration curve, and vertical chromatic aberration curve of the optical lens 300 are respectively as follows: Fig.12 , Fig.13 , Fig.14 , Fig.15 shown.

[0127] from Fig.12 It can be seen that the astigmatism of the meridional image plane and the sagittal image plane is controlled within ±0.2 mm, indicating that the optical lens 300 can correct the astigmatism well.

[0128] from Fig.13 It can be seen that the distortion value is controlled within ±1%, indicating that the optical lens 300 can correct the distortion well.

[0129] from Fig.14 It can be seen that the offset of the axial aberration is controlled within ±0.03 mm, indicating that the optical lens 300 can correct the axial aberration well.

[0130] from Fig.15 It can be seen that the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ±2μm, indicating that the optical lens 300 can correct chromatic aberration well.

[0131] Example 4

[0132] See also Fig.16 , shown is a schematic diagram of the structure of an optical lens 400 provided in Example 4 of the present invention. Compared with Example 1, the main difference between this embodiment and Example 1 is that the optical parameters such as the curvature radius of each lens surface and the lens thickness are different.

[0133] The relevant parameters of each lens in the optical lens 400 in Example 4 are shown in Table 4-1.

[0134] Table 4-1

[0135]

[0136] The surface parameters of the aspheric lens of the optical lens 400 in Example 4 are shown in Table 4-2.

[0137] Table 4-2

[0138]

[0139] In this embodiment, the astigmatism curve, F-Tan (Theta) distortion curve, axial aberration curve, and vertical chromatic aberration curve of the optical lens 400 are respectively as follows: Fig.17 , Fig.18 , Fig.19 , Fig. 20 shown.

[0140] from Fig.17 It can be seen that the astigmatism of the meridian image plane and the sagittal image plane is controlled within ±0.1 mm, indicating that the optical lens 400 can correct the astigmatism well.

[0141] from Fig.18 It can be seen that the distortion value is controlled within ±1%, indicating that the optical lens 400 can correct the distortion well.

[0142] from Fig.19 It can be seen that the offset of the axial aberration is controlled within ±0.02 mm, indicating that the optical lens 400 can correct the axial aberration well.

[0143] from Fig. 20 It can be seen that the vertical axis chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ±2μm, indicating that the optical lens 400 can correct chromatic aberration well.

[0144] Please refer to Table 5, which shows the optical characteristics corresponding to the above embodiments, including the effective focal length f of the optical lens, the total optical length TTL, the aperture value Fno, the real image height IH corresponding to the maximum field of view angle, the maximum field of view angle FOV, and the numerical value corresponding to each conditional expression in each embodiment.

[0145] Table 5

[0146]

[0147] In summary, the optical lens provided by the present invention has at least the following advantages:

[0148] (1) It can effectively shorten the overall length of the optical lens, which is conducive to better realizing the miniaturization and lightness of the equipment. The object side of the first lens is convex, which helps to converge the incident light, reduce the aperture of the head lens, and facilitate the miniaturization of the head.

[0149] (2) The lens has a small aperture. Through the design of a large F number and a small aperture, a longer depth of field is achieved while ensuring the imaging quality of the lens, so that the image can be accurately captured even when the image moves over a longer range. At the same time, the aperture is set between the first lens and the second lens, which helps to reduce various aberrations, especially spherical aberration and coma. The small aperture further reduces the impact of these aberrations, making the image quality higher and the edges clearer.

[0150] (3) Through specific surface shape settings and reasonable optical focal length distribution, it has small distortion, can achieve high-definition imaging, and improve the imaging quality of the optical lens.

[0151] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0152] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An optical lens, consisting of four lenses, characterized in that: From the object side to the imaging plane along the optical axis, it sequentially includes: A first lens with a positive optical power, whose object side is convex and whose image side is concave; A second lens with a negative optical power, whose object side is concave and whose image side is convex; A third lens with a negative optical power, whose object side is concave and whose image side is convex; A fourth lens with a positive optical power, whose object side is convex and whose image side is concave; Wherein, the true image height IH corresponding to the maximum field of view angle of the optical lens and the entrance pupil diameter EPD of the optical lens satisfy: 7.5 < IH / EPD < 9.3; the curvature radius R3 of the object side of the second lens and the curvature radius R4 of the image side of the second lens satisfy: -1 < (R3 - R4) / (R3 + R4) < -0.

2.

2. The optical lens according to claim 1, characterized in that: The overall optical length TTL of the optical lens and the effective focal length f of the optical lens satisfy: 1.3 < TTL / f < 1.6; the true image height IH corresponding to the maximum field of view angle of the optical lens and the effective focal length f of the optical lens satisfy: 1.6 < IH / f < 2.

2.

3. The optical lens according to claim 1, characterized in that: The entrance pupil diameter EPD of the optical lens and the maximum field of view angle FOV of the optical lens satisfy: 0.45mm < EPD×Tan(FOV / 2) < 0.65mm; the back focal length BFL of the optical lens and the overall optical length TTL of the optical lens satisfy: 0.4 < BFL / TTL < 0.

55.

4. The optical lens according to claim 1, characterized in that: The effective focal length f of the optical lens and the focal length f1 of the first lens satisfy: 0.9 < f1 / f < 1.3; the curvature radius R2 of the image side of the first lens and the effective focal length f of the optical lens satisfy: 0.8 < R2 / f < 5.

7.

5. The optical lens according to claim 1, characterized in that: The effective focal length f of the optical lens and the focal length f3 of the third lens satisfy: -36.7 < f3 / f < -3.3; the curvature radius R5 of the object side of the third lens and the curvature radius R6 of the image side of the third lens satisfy: -0.3 < (R5 - R6) / (R5 + R6) < 0.

6. The optical lens according to claim 1, characterized in that: The effective focal length f of the optical lens and the focal length f4 of the fourth lens satisfy: 1.15 < f4 / f < 2.4; the clear aperture semi-diameter d6 of the image side of the third lens and the clear aperture semi-diameter d7 of the object side of the fourth lens satisfy: 0.4 < d6 / d7 < 0.

6.

7. The optical lens according to claim 1, characterized in that: The focal length f1 of the first lens and the combined focal length f234 of the second lens, the third lens and the fourth lens satisfy: 0 < f1 / f234 < 0.5; the clear aperture semi-diameter d1 of the object side of the first lens and the true image height IH corresponding to the maximum field of view angle of the optical lens satisfy: 0.15 < d1 / (IH / 2) < 0.

3.

8. The optical lens according to claim 1, characterized in that: The focal length f2 of the second lens and the focal length f3 of the third lens satisfy: 0 < f2 / f3 < 0.8; the curvature radius R4 of the image side of the second lens and the curvature radius R5 of the object side of the third lens satisfy: 12.08 < R4 / R5 < 90.

36.

9. The optical lens according to claim 1, characterized in that: The effective focal length f of the optical lens and the curvature radius R3 of the object side surface of the second lens satisfy: -1.4 < R3 / f < -0.9; the effective focal length f of the optical lens and the curvature radius R4 of the image side surface of the second lens satisfy: -24.9 < R4 / f < -2.

25.

10. The optical lens according to claim 1, characterized in that: The sagittal height Sag3 of the clear aperture of the object side surface of the second lens and the clear aperture d3 of the object side surface of the second lens satisfy: -0.2 < Sag3 / d3 < 0; the sagittal height Sag4 of the clear aperture of the image side surface of the second lens and the clear aperture d4 of the image side surface of the second lens satisfy: -0.1 < Sag4 / d4 < 0.1; the true image height IH corresponding to the maximum field of view angle of the optical lens and the entrance pupil diameter EPD of the optical lens satisfy: 7.92 < IH / EPD < 8.5; the curvature radius R3 of the object side surface of the second lens and the curvature radius R4 of the image side surface of the second lens satisfy: -0.9 < (R3 - R4) / (R3 + R4) < -0.43.

Images