Optical lens

Abstract

The application provides an optical lens which is composed of four lenses and sequentially comprises, along an optical axis from an object side to an imaging surface: a first lens with negative optical power, the image side of which is a concave surface; a second lens with positive optical power, the image side of which is a convex surface; a third lens with positive optical power, the image side of which is a convex surface; and a fourth lens with positive optical power, the image side of which is a convex surface; wherein the effective focal length f of the optical lens and the focal length f1 of the first lens satisfy: -7.8 < f1 / f < -3.5. The optical lens provided by the application 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 application relates to the technical field of imaging lenses, in particular to an optical lens. BACKGROUND

[0002] In recent years, with the development of automation industry, machine vision has achieved explosive growth, and the application field of industrial lenses is also more and more extensive. Due to the characteristics of high resolution, high definition and good stability, industrial lenses are widely used in size measurement, defect detection, image acquisition and other fields.

[0003] In order to realize good image acquisition and analysis function, such industrial lenses usually require high definition resolution to obtain the image characteristics of the photographed object, and require high relative illumination to ensure the uniformity of picture illumination. However, the existing industrial lenses still have many shortcomings, for example, most of the lenses are large in size; the field of view is small, the resolution is poor, the imaging quality is poor, and it is difficult to meet the market demand. SUMMARY

[0004] In view of the above problems, the purpose of the present application is to provide an optical lens, which has the advantages of excellent imaging quality.

[0005] The technical scheme adopted by the present application is:

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

[0007] The first lens with negative focal power, the image side surface of which is concave;

[0008] The second lens with positive focal power, the image side surface of which is convex;

[0009] The third lens with positive focal power, the image side surface of which is convex;

[0010] The fourth lens with positive focal power, the image side surface of which is convex;

[0011] Wherein, the effective focal length f of the optical lens and the focal length f1 of the first lens satisfy: -7.8 < f1 / f < -3.5.

[0012] Further preferably, the object side surface light half aperture radius DM11 of the first lens and the image side surface light half aperture radius DM42 of the fourth lens satisfy: 8 < DM11 / DM42 < 9.5.

[0013] Further preferably, the object side surface light half aperture radius sag31 of the third lens, the image side surface light half aperture radius sag32 of the third lens and the center thickness CT3 of the third lens satisfy: -0.6 < (SAG32-SAG31) / CT3 < 0.1.

[0014] Further preferably, a real image height IH corresponding to a maximum field angle of view of the optical lens and an effective focal length f of the optical lens satisfy: 3<IH / f<4.5.

[0015] Further preferably, an effective focal length f of the optical lens and a focal length f4 of the fourth lens satisfy: 4<f4 / f<125; a focal length f3 of the third lens and the focal length f4 of the fourth lens satisfy: 0<f3 / f4<1.6.

[0016] Further preferably, a back focal length BFL of the optical lens and a total optical length TTL of the optical lens satisfy: 0.06<BFL / TTL<0.13.

[0017] Further preferably, a maximum field angle of view FOV of the optical lens, an effective focal length f of the optical lens and a real image height IH corresponding to the maximum field angle of view of the optical lens satisfy: 28°<(f x FOV) / IH<43°.

[0018] Further preferably, a radius of curvature R1 of an object side surface of the first lens and a radius of curvature R2 of an image side surface of the first lens satisfy: 0.9<(R1+R2) / (R1-R2)<1.1.

[0019] Further preferably, a central thickness CT3 of the third lens and an edge thickness ET3 of the third lens satisfy: 0.9<CT3 / ET3<2.3.

[0020] Further preferably, a half diameter of light passing DM11 of the object side surface of the first lens and a real image height IH corresponding to a maximum field angle of view of the optical lens satisfy: 2.7<DM11 / IH<3.5.

[0021] Compared with the prior art, the optical lens provided by the present application adopts four lenses with specific optical powers, and through specific surface shape matching and reasonable optical power distribution, the imaging quality of the optical lens can be improved, the aberration can be reduced, and the imaging quality of the optical lens can be improved, so that the lens has one or more advantages of small total length, large field angle of view, high resolution, high imaging quality, etc. BRIEF DESCRIPTION OF DRAWINGS

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

[0023] Figure 1 FIG. 1 is a structural schematic diagram of an optical lens according to an embodiment of the present application.

[0024] Figure 2F-Tan(Theta) distortion curve of the optical lens in Embodiment 1 of the present application.

[0025] Figure 3 Curvature plot of the optical lens in Embodiment 1 of the present application.

[0026] Figure 4 Curvature plot of the optical lens in Embodiment 1 of the present application.

[0027] Figure 5 Curvature plot of the optical lens in Embodiment 1 of the present application.

[0028] Figure 6 Structure diagram of the optical lens in Embodiment 2 of the present application.

[0029] Figure 7 F-Tan(Theta) distortion curve of the optical lens in Embodiment 2 of the present application.

[0030] Figure 8 Curvature plot of the optical lens in Embodiment 2 of the present application.

[0031] Figure 9 Curvature plot of the optical lens in Embodiment 2 of the present application.

[0032] Figure 10 Curvature plot of the optical lens in Embodiment 2 of the present application.

[0033] Figure 11 Structure diagram of the optical lens in Embodiment 3 of the present application.

[0034] Figure 12 F-Tan(Theta) distortion curve of the optical lens in Embodiment 3 of the present application.

[0035] Figure 13 Curvature plot of the optical lens in Embodiment 3 of the present application.

[0036] Figure 14 Curvature plot of the optical lens in Embodiment 3 of the present application.

[0037] Figure 15 Curvature plot of the optical lens in Embodiment 3 of the present application.

[0038] Figure 16 Structure diagram of the optical lens in Embodiment 4 of the present application.

[0039] Figure 17 F-Tan(Theta) distortion curve of the optical lens in Embodiment 4 of the present application.

[0040] Figure 18 A graph of the lateral chromatic aberration curve of the optical lens in Embodiment 4 of the present application.

[0041] Figure 19 A graph of the relative luminance curve of the optical lens in Embodiment 4 of the present application.

[0042] Figure 20 A graph of the MTF curve of the optical lens in Embodiment 4 of the present application.

[0043] The following detailed description will further describe the present application with reference to the above-mentioned drawings. DETAILED DESCRIPTION

[0044] For a better understanding of the present application, various aspects of the present application will be described in more detail below with reference to the accompanying drawings. It is to be noted that these detailed descriptions are only descriptions of embodiments of the present application and are not intended in any way to limit the scope of the present application. Throughout the specification, like drawing reference numerals refer to like elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0045] It is to be noted that, in the present specification, the expressions first, second, third and the like are used only to distinguish one feature from another feature, and do not indicate any limitation on the features. Thus, the first lens discussed below can also be referred to as the second lens or the third lens without departing from the teachings of the present application.

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

[0047] In the present specification, the paraxial region refers to a region near the optical axis. If a lens surface is convex and the position of the convex surface is not specified, it means that the lens surface is convex at least in the paraxial region. If a lens surface is concave and the position of the concave surface is not specified, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the object is referred to as the object side surface of the lens, and the surface of each lens closest to the image plane is referred to as the image side surface of the lens.

[0048] It should also be understood that the use of the terms "including", "including having", "having", "containing", and / or "containing having" when used in this specification intends that existence of stated features, elements and / or components but does not exclude the presence or addition of one or more other features, elements, components, and / or groups thereof. In addition, when describing the embodiments of the present application, the use of "may" means "one or more embodiments of the present application". Also, the term "exemplary" is intended to refer to an example or illustration.

[0049] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It should also be understood that the terms should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0050] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0051] The optical lens provided by the embodiments of the present application is composed of four lenses, which are sequentially arranged along the optical axis from the object side to the imaging surface as the first lens, the second lens, the third lens and the fourth lens.

[0052] In some embodiments, the first lens can have a negative focal power, the object side surface thereof can be a concave surface or a convex surface, and the image side surface thereof is a concave surface. The second lens can have a positive focal power, the object side surface thereof can be a concave surface or a convex surface, and the image side surface thereof is a convex surface. The third lens can have a positive focal power, the object side surface thereof can be a concave surface or a convex surface, and the image side surface thereof is a convex surface. The fourth lens can have a positive focal power, the object side surface thereof can be a concave surface or a convex surface, and the image side surface thereof is a convex surface.

[0053] In some embodiments, the optical lens can further comprise a diaphragm for limiting the light beam, which can be located between the third lens and the fourth lens or between the second lens and the third lens, thereby reducing the generation of ghost images of the optical lens and effectively reducing the difficulty of distortion correction of the lens.

[0054] In some embodiments, the optical lens can further comprise a filter, which can be arranged between the fourth lens and the imaging surface. The filter is used to filter out interference light to prevent the interference light from reaching the imaging surface of the optical lens and affecting normal imaging.

[0055] In some embodiments, the effective focal length f of the optical lens and the focal length f1 of the first lens satisfy: -7.8 < f1 / f < -3.5. Satisfying the above condition, the first lens has a proper negative focal length, which is beneficial to expand the field of view of the optical lens.

[0056] In some embodiments, the object-side half-field aperture radius DM11 of the first lens and the image-side half-field aperture radius DM42 of the fourth lens satisfy: 8 < DM11 / DM42 < 9.5. Satisfying the above range, by reasonably setting the focal length and aperture relationship of the first and last lenses, the area of the light entering the image plane is increased while ensuring as much light as possible enters the system, and high relative illumination of the lens is achieved.

[0057] In some embodiments, the object-side half-field aperture radius sag height SAG31 of the third lens, the image-side half-field aperture radius sag height SAG32 of the third lens, and the central thickness CT3 of the third lens satisfy: -0.6 < (SAG32-SAG31) / CT3 < 0.1. Satisfying the above condition, the surface shape of the third lens can be reasonably controlled, which is beneficial to correct the aberration of the system.

[0058] In some embodiments, the real image height IH corresponding to the maximum field of view of the optical lens and the effective focal length f of the optical lens satisfy: 3 < IH / f < 4.5. Satisfying the above range, by reasonably controlling the ratio of the image height and the focal length of the optical lens, the ultra-wide-angle characteristic is achieved, thereby meeting the shooting demand of large wide-angle.

[0059] In some embodiments, the effective focal length f of the optical lens and the focal length f4 of the fourth lens satisfy: 4 < f4 / f < 125. Satisfying the above condition, the field curvature is corrected, the chromatic aberration is balanced, the dispersion is complementary to the first three lens groups, and the sensor image plane is adapted.

[0060] In some embodiments, the focal length f3 of the third lens and the focal length f4 of the fourth lens satisfy: 0 < f3 / f4 < 1.6. Satisfying the above condition of focal power combination, the lens temperature drift stability performance can be improved, which helps to reduce the influence of environmental temperature on the lens group, and also meets the compactness requirement of the lens.

[0061] In some embodiments, the back focal length BFL of the optical lens and the total optical length TTL of the optical lens satisfy: 0.06 < BFL / TTL < 0.13. Satisfying the above condition, the ratio of the back focal length of the optical lens and the total optical length of the optical lens is reasonably configured, which is beneficial to realize the short back focal length of the optical lens, and in the case of ensuring sufficient space for optical element installation and focusing, it is beneficial to realize the miniaturization of the optical lens.

[0062] In some embodiments, the maximum field of view FOV of the optical lens, the effective focal length f of the optical lens, and the real image height IH corresponding to the maximum field of view FOV of the optical lens satisfy: 28° < (f x FOV) / IH < 43°. Satisfying the above range, by reasonably limiting the relationship among the focal length, the field of view angle, and the image height of the optical lens, the optical lens has good optical performance and can well capture the details of the object.

[0063] In some embodiments, the object-side surface radius of curvature R1 of the first lens and the image-side surface radius of curvature R2 of the first lens satisfy: 0.9 < (R1 + R2) / (R1 - R2) < 1.1. Satisfying the above condition, the object-side surface and the image-side surface of the first lens are reasonably controlled, thereby being conducive to controlling the shape of the first lens, correcting the aberration generated by itself, and improving the imaging quality.

[0064] In some embodiments, the center thickness CT3 of the third lens and the edge thickness ET3 of the third lens satisfy: 0.9 < CT3 / ET3 < 2.3. By making the optical system satisfy the above relationship, the lens processing and molding are facilitated, the assembly difficulty is reduced, and the field curvature of the system can be effectively corrected.

[0065] In some embodiments, the object-side half diameter of the first lens DM11 and the real image height IH corresponding to the maximum field of view angle of the optical lens satisfy: 2.7 < DM11 / IH < 3.5. Satisfying the above condition, the lens can have a larger field of view angle while the overall size of the lens is moderate.

[0066] In some embodiments, the total optical length TTL of the optical lens and the effective focal length f of the optical lens satisfy: 23 < TTL / f < 37. Satisfying the above condition, the length of the lens can be effectively limited, which is conducive to the miniaturization of the optical lens.

[0067] In some embodiments, the total optical length TTL of the optical lens and the real image height IH corresponding to the maximum field of view angle of the optical lens satisfy: 5.5 < TTL / IH < 12. Satisfying the above condition, by controlling the ratio between the distance from the object-side surface of the first lens to the image surface of the optical system on the optical axis and the image height of the optical system, the total length of the optical system is short, the lens structure is compact, and the miniaturization is realized.

[0068] In some embodiments, the focal length f2 of the second lens and the effective focal length f of the optical lens satisfy: 9 < f2 / f < 25. Satisfying the above condition, the light path can be controlled, and more reasonable light incidence angles are provided for subsequent lenses, thereby reducing the astigmatism and the field curvature.

[0069] In some embodiments, the focal length f3 of the third lens and the effective focal length f of the optical lens satisfy: 1.1 < f3 / f < 7.5. Meeting the above conditions, the third lens converges the incident light rays at the front end, which is beneficial to correcting the aberration and distortion of the edge field of view brought by the front lens group, enabling the lens to have less distortion and providing a high-definition imaging effect.

[0070] In some embodiments, the maximum field of view FOV of the optical lens and the f-number Fno of the optical lens satisfy: 59° < FOV / Fno < 66°. Meeting the above conditions is beneficial to expanding the field of view angle of the optical lens and increasing the aperture of the optical lens, realizing the wide-angle and large-aperture characteristics of the lens. The realization of the wide-angle characteristic is beneficial for the optical lens to obtain more scene information and meet the requirements of large-range detection. The realization of the large-aperture characteristic is beneficial to improving the problem of the rapid decrease of the relative brightness of the edge field of view brought by the wide angle, and thus is also beneficial to obtaining more scene information.

[0071] In some embodiments, the overall optical length TTL of the optical lens, the true image height IH corresponding to the maximum field of view angle of the optical lens, and the maximum field of view angle FOV of the optical lens satisfy: 0.04 / ° < TTL / IH / FOV < 0.1 / °. Meeting the above range is beneficial to balancing the relationship among the overall length, image height, and field of view angle of the optical lens.

[0072] 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: 6 < IH / EPD < 9. Meeting the above conditions makes the field of view and light flux balanced and improves the imaging quality of the lens.

[0073] 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: 0.6 < (R3 + R4) / (R3 - R4) < 2. Meeting the above range can reduce the light ray deflection angle, 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.

[0074] In some embodiments, 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: 0.5 < (R5 + R6) / (R5 - R6) < 3.6. Meeting the above conditions, the third lens can balance the system field curvature and avoid the deterioration of the edge image quality.

[0075] In some embodiments, the curvature radius R7 of the object side surface of the fourth lens and the curvature radius R8 of the image side surface of the fourth lens satisfy: -2.5 < (R7 + R8) / (R7 - R8) < 0.7. Meeting the above conditions is beneficial to alleviating the deflection degree of the light ray passing through the lens and can well reduce the aberration.

[0076] In some embodiments, the image-side surface curvature radius R2 of the first lens and the effective focal length f of the optical lens satisfy: 2 < R2 / f < 4.2; the image-side surface curvature radius R4 of the second lens and the effective focal length f of the optical lens satisfy: -18 < R4 / f < -4.5; and the image-side surface curvature radius R6 of the third lens and the effective focal length f of the optical lens satisfy: -4 < R6 / f < -0.7. Satisfying the above ranges can control the direction of light rays, reduce spherical aberration, correct coma, increase light utilization, and improve stability.

[0077] In some embodiments, the image-side surface curvature radius R8 of the fourth lens and the effective focal length f of the optical lens satisfy: -3.5 < R8 / f < -1.5. Satisfying the above condition can help to moderate the deflection degree of light rays passing through the lens and can effectively reduce aberration.

[0078] In some embodiments, the object-side surface curvature radius R1 of the first lens, the image-side surface curvature radius R2 of the first lens, and the central thickness CT1 of the first lens satisfy: -25 < R1 / (R2+CT1) < 90. Satisfying the above range can reduce the correction difficulty of edge field distortion and control the distortion within a reasonable range.

[0079] In some embodiments, the focal length f1 of the first lens and the focal length f2 of the second lens satisfy: -0.5 < f1 / f2 < -0.3. Satisfying the above condition ensures that the optical power of the second lens is positive when the optical power of the first lens is negative, thereby effectively controlling the volume of the optical system. The first lens and the second lens have opposite optical powers, which can make the optical system have a better ability to balance aberration.

[0080] In some embodiments, the focal length f1 of the first lens and the focal length f4 of the fourth lens satisfy: -1.8 < f1 / f4 < 0. Satisfying the above condition can make the lens have a smaller head size while having a larger imaging surface by reasonably setting the focal length ratio of the first and last lenses, thereby better satisfying the balance between miniaturization and high pixels.

[0081] In some embodiments, the distance CT12 between the first lens and the second lens on the optical axis, the distance CT23 between the second lens and the third lens on the optical axis, the distance CT34 between the third lens and the fourth lens on the optical axis, and the total optical length TTL of the optical lens satisfy: 0.25 < (CT12+CT23+CT34) / TTL < 0.35. Satisfying the above condition can compress the total length of the lens by reducing the distance between the first lens, the second lens, the third lens, and the fourth lens.

[0082] In some embodiments, the center thickness CT2 of the second lens, the center thickness CT3 of the third lens, and the total track length TTL of the optical lens satisfy: 0.22 < (CT2 + CT3) / TTL < 0.45. Satisfying the above condition, the proportion of the second lens and the third lens in the total length is controlled, which can improve the stability of the lens and reduce the temperature drift.

[0083] In some embodiments, the distance ET12 at the edge of the first lens and the second lens and the distance CT12 of the first lens and the second lens on the optical axis satisfy: 0.1 < ET12 / CT12 < 0.2. Satisfying the above condition is conducive to the second lens correcting the aberration of the first lens, and is also conducive to the molding manufacturing and assembly.

[0084] In some embodiments, the half-aperture sagittal height SAG11 of the object side surface of the first lens, the half-aperture sagittal height SAG12 of the image side surface of the first lens, and the center thickness CT1 of the first lens satisfy: 0.3 < (SAG12 - SAG11) / CT1 < 1.5. Satisfying the above condition can control the shape of the first lens, reduce the molding difficulty of the first lens, thereby reducing the processing sensitivity, and is conducive to improving the production yield of the wide-angle lens.

[0085] In some embodiments, the half-aperture sagittal height SAG41 of the object side surface of the fourth lens, the half-aperture sagittal height SAG42 of the image side surface of the fourth lens, and the center thickness CT4 of the fourth lens satisfy: -0.1 < (SAG42 - SAG41) / CT4 < 0.1. Satisfying the above condition is conducive to correcting the coma of the off-axis field by controlling the relationship between the height difference of the image side surface and the object side surface of the fourth lens and the center thickness of the fourth lens, and is conducive to improving the imaging quality of the optical lens in the off-axis field.

[0086] In some embodiments, the half-aperture diameter DM11 of the object side surface of the first lens and the half-aperture diameter DM21 of the object side surface of the second lens satisfy: 1.8 < DM11 / DM21 < 4.5. Satisfying the above condition ensures that light rays enter the lens in a large range, and ensures that the lens has a large field of view.

[0087] In some embodiments, the half-aperture diameter DM11 of the object side surface of the first lens and the focal length f1 of the first lens satisfy: -3.2 < DM11 / f1 < -1.4. Satisfying the above condition controls the shape of the first lens by controlling the ratio of the half-aperture diameter of the object side surface of the first lens to the focal length of the first lens, so that the light rays enter the object side surface of the first lens at the maximum incidence angle, and the wide-angle of the optical system is realized.

[0088] In some embodiments, the optical lens satisfies the condition formula: 8.9mm < TTL < 10mm, 0.2mm < f < 0.5mm, 110° < FOV < 140°, 0.75mm < IH < 1.8mm, 1.9 < Fno < 2.1; wherein, TTL represents the total optical length of the optical lens, f represents the effective focal length of the optical lens, FOV represents the maximum field of view angle of the optical lens, IH represents the real image height corresponding to the maximum field of view angle of the optical lens, and Fno represents the aperture value of the optical lens. Satisfying the above condition indicates that the optical lens provided by the embodiment of the present application at least has the characteristics of small total length, large field of view angle, etc.

[0089] In some embodiments, the first lens, the second lens, the third lens and the fourth lens can adopt a spherical lens or an aspherical lens. Compared with a spherical structure, an 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 achieving lens miniaturization. More specifically, the first lens, the second lens, the third lens and the fourth lens of the present application can adopt an aspherical lens.

[0090] In some embodiments, the lens material in the optical lens provided by the present application can 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 application can be plastic lenses.

[0091] In various embodiments of the present application, when the lens adopts an aspherical lens, the shape of each aspherical surface of the optical lens satisfies the following equation:

[0092] ;

[0093] wherein, z is the distance of the curved surface from the vertex of the curved surface in the direction of the optical axis, h is the distance from the optical axis to the curved surface, c is the curvature of the vertex of the curved surface, K is the quadratic surface coefficient, and B, C, D, E, F, G and H are respectively the fourth-order, sixth-order, eighth-order, tenth-order, twelfth-order, fourteenth-order and sixteenth-order surface coefficients.

[0094] The present application will be further described in the following embodiments. In various embodiments, the thickness, the radius of curvature and the material selection of each lens in the optical lens are different, and the specific differences can be referred to the parameter table of each embodiment. The following embodiments are only preferred embodiments of the present application, but the embodiments of the present application are not limited to the following embodiments only, and any changes, substitutions, combinations or simplifications made without departing from the innovative points of the present application should be regarded as equivalent replacement modes, and are included in the protection scope of the present application.

[0095] Embodiment 1

[0096] Referring to Figure 1 , a structural diagram of an optical lens 100 provided in Embodiment 1 of the present application is shown, which comprises, in order from the object side to the imaging surface along the optical axis, a first lens L1, a second lens L2, a third lens L3, a stop ST, a fourth lens L4, and a filter G1.

[0097] The first lens L1 has a negative focal power, the object side surface S1 is a concave surface, and the image side surface S2 is a concave surface.

[0098] The second lens L2 has a positive focal power, the object side surface S3 is a convex surface at the vicinity of the optical axis, and the image side surface S4 is a convex surface.

[0099] The third lens L3 has a positive focal power, the object side surface S5 is a concave surface, and the image side surface S6 is a convex surface.

[0100] The fourth lens L4 has a positive focal power, the object side surface S7 is a convex surface, and the image side surface S8 is a convex surface.

[0101] The object side surface S9 and the image side surface S10 of the filter G1 are both flat surfaces.

[0102] The imaging surface S11 is a flat surface.

[0103] The first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are plastic aspherical lenses.

[0104] The related parameters of the lenses in the optical lens 100 in Embodiment 1 are shown in Table 1-1.

[0105] Table 1-1

[0106]

[0107] The surface type parameters of the aspherical lenses of the optical lens 100 in Embodiment 1 are shown in Table 1-2.

[0108] Table 1-2

[0109]

[0110] In this embodiment, the F-Tan(Theta) distortion curve, the axial chromatic aberration curve, the relative luminance curve, and the MTF curve of the optical lens 100 are shown in Figure 2 , Figure 3 , Figure 4 , Figure 5 respectively.

[0111] Figure 2A F-Tan (Theta) distortion curve of the optical lens 100 of the embodiment 1 is shown, which represents the distortion of different field angles on the imaging plane, the horizontal axis represents the distortion value (unit: %), and the vertical axis represents the half field angle (unit: °). As can be seen from the figure, the distortion value is controlled within 0~40%, which shows that the optical lens 100 can correct the distortion well.

[0112] Figure 3 A curve of the axial chromatic aberration of the embodiment 1 is shown, which represents the chromatic aberration of different wavelengths on the imaging plane at different image heights relative to the central wavelength (0.546 μm), the horizontal axis represents the axial chromatic aberration value of each wavelength relative to the central wavelength (unit: μm), and the vertical axis represents the normalized field angle. As can be seen from the figure, the axial chromatic aberration of the longest wavelength and the shortest wavelength is controlled within ±1 μm, which shows that the optical lens 100 can correct the chromatic aberration well.

[0113] Figure 4 A relative illumination curve of the embodiment 1 is shown, which represents the relative illumination value of different field angles on the imaging plane, the horizontal axis represents the half field angle (unit: °), and the vertical axis represents the relative illumination (unit: %). As can be seen from the figure, the relative illumination value of the optical lens is still greater than 60% at the maximum half field angle, which shows that the optical lens 100 has good relative illumination.

[0114] Figure 5 A modulation transfer function (MTF) curve of the embodiment 1 is shown, which represents the imaging modulation degree of the lens at different spatial frequencies under each field of view, the horizontal axis represents the spatial frequency (unit: lp / mm), and the vertical axis represents the MTF value. As can be seen from the figure, the MTF value of the embodiment is above 0.3 within the full field of view, and the MTF curve uniformly and smoothly decreases from the center to the edge field of view, which has good imaging quality and good detail resolution ability in the case of low frequency and high frequency.

[0115] Embodiment 2

[0116] Please refer to Figure 6 , which is a structural schematic diagram of the optical lens 200 provided in the embodiment 2 of the present application. Compared with the embodiment 1, the main difference is that the diaphragm ST is arranged between the second lens L2 and the third lens L3; the object side S1 of the first lens L1 is a convex surface; the object side S3 of the second lens L2 is a concave surface; the object side S5 of the third lens L3 is a convex surface; the object side S7 of the fourth lens L4 is a concave surface; and the optical parameters such as the curvature radius and the lens thickness of each lens surface are different.

[0117] The related parameters of each lens in the optical lens 200 in the embodiment 2 are shown in Table 2-1.

[0118] Table 2-1

[0119]

[0120] The surface profile parameters of the aspherical lens of the optical lens 200 in Embodiment 2 are shown in Table 2-2.

[0121] Table 2-2

[0122]

[0123] In the present embodiment, the F-Tan(Theta) distortion curve, the axial chromatic aberration curve, the relative illumination curve and the MTF curve of the optical lens 200 are shown in Figure 7 、 Figure 8 、 Figure 9 、 Figure 10 respectively.

[0124] As can be seen from Figure 7 , the distortion value is controlled within 0-20%, which shows that the optical lens 200 can correct the distortion well.

[0125] As can be seen from Figure 8 , the axial chromatic aberration of the longest wavelength and the shortest wavelength is controlled within -2 μm-4 μm, which shows that the optical lens 200 can correct the chromatic aberration well.

[0126] As can be seen from Figure 9 , the relative illumination value of the optical lens at the maximum half field angle is still greater than 30%, which shows that the optical lens 200 has good relative illumination.

[0127] As can be seen from Figure 10 , the MTF value of the present embodiment is above 0.58 in the full field of view, and the MTF curve is uniformly and smoothly decreased from the center to the edge of the field of view, which has good imaging quality and good detail resolution ability in the case of low frequency and high frequency.

[0128] Embodiment 3

[0129] Please refer to Figure 11 , which is a structural schematic diagram of the optical lens 300 provided in Embodiment 3 of the present application. Compared with Embodiment 1, the main difference is that the object side S1 of the first lens L1 is a convex surface; the object side S3 of the second lens L2 is a concave surface; and the optical parameters such as the curvature radius and the lens thickness of each lens surface are different.

[0130] The related parameters of each lens in the optical lens 300 in Embodiment 3 are shown in Table 3-1.

[0131] Table 3-1

[0132]

[0133] The surface profile parameters of the aspherical lens of the optical lens 300 in Example 3 are shown in Table 3-2.

[0134] Table 3-2

[0135]

[0136] In this embodiment, the F-Tan (Theta) distortion curve, transverse chromatic aberration curve, relative illumination curve, and MTF curve of the optical lens 300 are respectively as follows: Figure 12 , Figure 13 , Figure 14 , Figure 15 As shown.

[0137] from Figure 12 As can be seen, the distortion value is controlled within -25% to 20%, indicating that the optical lens 300 can correct distortion well.

[0138] from Figure 13 As can be seen, the chromatic aberration of the longest and shortest wavelengths is controlled within ±1μm, indicating that the optical lens 300 can correct chromatic aberration well.

[0139] from Figure 14 As can be seen, the relative illumination value of the optical lens is still greater than 55% at the maximum half field of view, indicating that the optical lens 300 has good relative illumination.

[0140] from Figure 15 As can be seen, the MTF value of this embodiment is above 0.5 throughout the entire field of view. The MTF curve decreases smoothly and evenly from the center to the edge of the field of view, demonstrating good imaging quality and good detail resolution in both low and high frequency conditions.

[0141] Example 4

[0142] Please see Figure 16 The figure shows a schematic diagram of the structure of the optical lens 400 provided in Embodiment 4 of the present invention. The main difference between this embodiment and Embodiment 1 is that the object side surface S1 of the first lens L1 is a convex surface; the optical parameters such as the radius of curvature and lens thickness of each lens surface are different.

[0143] The relevant parameters of each lens in the optical lens 400 in Example 4 are shown in Table 4-1.

[0144] Table 4-1

[0145]

[0146] The surface profile parameters of the aspherical lens of the optical lens 400 in Example 4 are shown in Table 4-2.

[0147] Table 4-2

[0148]

[0149] In this embodiment, the F-Tan (Theta) distortion curve, transverse chromatic aberration curve, relative illumination curve, and MTF curve of the optical lens 400 are respectively as follows: Figure 17 , Figure 18 , Figure 19 , Figure 20 As shown.

[0150] from Figure 17 As can be seen, the distortion value is controlled within -20% to 25%, indicating that the optical lens 400 can correct distortion well.

[0151] from Figure 18 As can be seen, the transverse chromatic aberration of the longest and shortest wavelengths is controlled within ±1μm, indicating that the optical lens 400 can correct chromatic aberration well.

[0152] from Figure 19 As can be seen, the relative illumination value of the optical lens is still greater than 50% at the maximum half field of view, indicating that the optical lens 400 has good relative illumination.

[0153] from Figure 20 As can be seen, the MTF value of this embodiment is above 0.3 throughout the entire field of view. The MTF curve decreases smoothly and evenly from the center to the edge of the field of view, demonstrating good imaging quality and good detail resolution in both low and high frequency conditions.

[0154] Please refer to Tables 5-1 and 5-2 for the optical characteristics corresponding to the above embodiments, including the effective focal length f, total optical length TTL, aperture value Fno, true image height IH corresponding to the maximum field of view, maximum field of view FOV, principal ray incident angle CRA at the maximum image height, and the values ​​corresponding to each conditional expression in each embodiment.

[0155] Table 5-1

[0156]

[0157] Table 5-2

[0158]

[0159] In summary, the optical lens provided by the present invention uses four lenses with specific optical powers. Through specific surface shape matching and reasonable optical power distribution, it can improve the imaging quality of the optical lens, reduce aberrations, and enhance the imaging quality of the optical lens, giving the lens one or more advantages such as small overall length, large field of view, high resolution, and high imaging quality.

[0160] 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.

[0161] 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, comprising four lenses, characterized in that, Along the optical axis from the object side to the imaging plane, the following are included in sequence: The first lens with negative optical power has a concave image-side surface. A second lens with positive optical power has a convex image-side surface. The third lens with positive optical power has a convex image-side surface; The fourth lens has positive optical power and its image-side surface is convex. Wherein, the effective focal length f of the optical lens and the focal length f1 of the first lens satisfy: -7.8 <f1 / f<-3.5; The object-side half-aperture DM11 of the first lens and the image-side half-aperture DM42 of the fourth lens satisfy: 8 <DM11 / DM42<9.5。 2. The optical lens according to claim 1, characterized in that, The total optical length TTL of the optical lens and the effective focal length f of the optical lens satisfy: 23 <TTL / f<37。 3. The optical lens according to claim 1, characterized in that, The object-side half-aperture height SAG31 of the third lens, the image-side half-aperture height SAG32 of the third lens, and the center thickness CT3 of the third lens satisfy the following condition: -0.6 < (SAG32 - SAG31) / CT3 < 0.

1.

4. The optical lens according to claim 1, characterized in that, The true image height IH corresponding to the maximum field of view of the optical lens and the effective focal length f of the optical lens satisfy: 3 <IH / f<4.5。 5. 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: 4 <f4 / f<125。 6. The optical lens according to claim 1, characterized in that, The back focal length (BFL) of the optical lens and the total optical length (TTL) of the optical lens satisfy: 0.06 <BFL / TTL<0.13。 7. The optical lens according to claim 1, characterized in that, The maximum field of view (FOV) of the optical lens, the effective focal length (f) of the optical lens, and the true image height (IH) corresponding to the maximum field of view of the optical lens satisfy the following condition: 28° < (f × FOV) / IH < 43°.

8. The optical lens according to claim 1, characterized in that, The object-side radius of curvature R1 of the first lens and the image-side radius of curvature R2 of the first lens satisfy: 0.9 < (R1 + R2) / (R1 - R2) < 1.

1.

9. The optical lens according to claim 1, characterized in that, The center thickness CT3 and the edge thickness ET3 of the third lens satisfy: 0.9 <CT3 / ET3<2.3。 10. The optical lens according to claim 1, characterized in that, The half-aperture DM11 of the object-side surface of the first lens and the true image height IH corresponding to the maximum field of view of the optical lens satisfy: 2.7 <DM11 / IH<3.5。

Images