CN117420667B

CN117420667B - Optical lens and optical system

Info

Publication number: CN117420667B
Application number: CN202311745559.2A
Authority: CN
Inventors: 谢雨辰; 周熠辰; 章彬炜; 曾昊杰
Original assignee: Jiangxi Lianyi Optics Co Ltd
Current assignee: Jiangxi Lianyi Optics Co Ltd
Priority date: 2023-12-19
Filing date: 2023-12-19
Publication date: 2024-03-26
Anticipated expiration: 2043-12-19
Also published as: CN117420667A

Abstract

The invention discloses an optical lens and an optical system, wherein the optical lens sequentially comprises from an object side to an imaging surface along an optical axis: a diaphragm; a first lens with positive focal power, wherein the object side surface of the first lens is a convex surface; a second lens having negative optical power, an image side surface of the second lens being a concave surface; a third lens with negative focal power, wherein the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface; a fourth lens element with optical power, wherein an object-side surface of the fourth lens element is concave and an image-side surface of the fourth lens element is convex; wherein, the effective focal length f of the optical lens and the image height IH corresponding to the maximum half field angle of the optical lens satisfy the following conditions: f/IH is more than 5.0 and less than 6.0. The optical lens and the optical system provided by the invention have the advantages of long focal length, large image plane and high pixel.

Description

Optical lens and optical system

Technical Field

The present invention relates to the field of imaging lenses, and in particular, to an optical lens and an optical system.

Background

In recent years, along with the pursuit of imaging quality of portable electronic products, multiple cameras have become standard of mobile phone products. In order to improve the imaging quality of remote objects, a flagship machine of most mobile phone factories is provided with a tele optical lens, and the effect of clearly amplifying scenes can be realized when long scenes are shot, so that the imaging quality of mobile phone shooting is improved.

In the existing multi-camera portable electronic products, the 35mm equivalent focal length ratio of most conventional long-focus lenses and wide-angle lenses is 3-5 times, the zoom ratio can reach 3-5 times by combination and collocation, and compared with the conventional zoom lenses, the optical zoom multiple is smaller, so that the high-definition imaging requirements of increasingly-improved portable electronic products of customers are difficult to meet.

Disclosure of Invention

Therefore, the present invention is directed to an optical lens and an optical system, which have at least the advantages of long focal length and large image surface.

The embodiment of the invention realizes the aim through the following technical scheme.

In one aspect, the present invention provides an optical lens comprising, in order from an object side to an imaging surface along an optical axis: a diaphragm; a first lens with positive focal power, wherein the object side surface of the first lens is a convex surface; a second lens having negative optical power, an image side surface of the second lens being a concave surface; a third lens with negative focal power, wherein the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface; a fourth lens element with optical power, wherein an object-side surface of the fourth lens element is concave and an image-side surface of the fourth lens element is convex; wherein, the effective focal length f of the optical lens and the image height IH corresponding to the maximum half field angle of the optical lens satisfy the following conditions: f/IH is more than 5.0 and less than 6.0.

In another aspect, the present invention provides an optical system comprising a prism and an optical lens as described above; the prism is used for turning incident light so as to enable the incident light to enter the optical lens; the optical lens is positioned on the light emitting side of the prism, and the first lens is arranged closer to the prism than the fourth lens.

Compared with the prior art, the optical lens and the optical system provided by the invention adopt four lenses with specific focal power, and the optical lens has the advantages of good imaging quality, long focal length and large image surface through specific surface shape collocation and reasonable focal power distribution, so that higher optical zoom multiple can be realized, and the high-definition imaging requirement of the current light and thin electronic product on long-distance vision can be better met.

Drawings

Fig. 1 is a schematic structural diagram of an optical lens according to a first embodiment of the present invention.

Fig. 2 is a distortion graph of an optical lens according to a first embodiment of the present invention.

Fig. 3 is a graph showing a field curvature of an optical lens according to a first embodiment of the present invention.

Fig. 4 is a vertical axis chromatic aberration diagram of an optical lens according to a first embodiment of the present invention.

Fig. 5 is a schematic structural diagram of an optical lens according to a second embodiment of the present invention.

Fig. 6 is a distortion graph of an optical lens according to a second embodiment of the present invention.

Fig. 7 is a field curvature chart of an optical lens according to a second embodiment of the present invention.

Fig. 8 is a vertical axis chromatic aberration diagram of an optical lens according to a second embodiment of the present invention.

Fig. 9 is a schematic structural diagram of an optical lens according to a third embodiment of the present invention.

Fig. 10 is a distortion graph of an optical lens according to a third embodiment of the present invention.

Fig. 11 is a field curve diagram of an optical lens according to a third embodiment of the present invention.

Fig. 12 is a vertical axis chromatic aberration diagram of an optical lens according to a third embodiment of the present invention.

Fig. 13 is a schematic structural diagram of an optical lens according to a fourth embodiment of the present invention.

Fig. 14 is a distortion graph of an optical lens according to a fourth embodiment of the present invention.

Fig. 15 is a field curvature graph of an optical lens according to a fourth embodiment of the present invention.

Fig. 16 is a vertical axis chromatic aberration diagram of an optical lens according to a fourth embodiment of the present invention.

Fig. 17 is a schematic structural view of an optical system according to a fifth embodiment of the present invention.

Detailed Description

In order that the objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Several embodiments of the invention are presented in the figures. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

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

In this context, near the optical axis means the area near the optical axis. If the lens surface is convex and the convex position 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 concave position is not defined, it means that the lens surface is concave at least in the paraxial region.

The invention provides an optical lens, which sequentially comprises from an object side to an imaging surface along an optical axis: the optical centers of the diaphragm, the first lens, the second lens, the third lens, the fourth lens and the optical filter are positioned on the same straight line.

The first lens has positive focal power, the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a convex surface or a concave surface at a paraxial region; the second lens has negative focal power, the object side surface of the second lens is a convex surface or a concave surface at a paraxial region, and the image side surface of the second lens is a concave surface; the third lens has negative focal power, the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface; the fourth lens has positive focal power or negative focal power, the object side surface of the fourth lens is concave, and the image side surface of the fourth lens is convex. Meanwhile, the first lens to the fourth lens at least comprise one aspheric lens.

In some embodiments, a diaphragm for limiting the light beam may be disposed before the object side surface of the first lens, and the diaphragm is disposed in front of the object side surface, so that a longer distance between the exit pupil of the lens group and the imaging surface in the optical lens can be generated, the efficiency of receiving the image by the imaging chip is increased, and the long focal length performance of the optical lens is facilitated.

The optical lens provided by the embodiment of the invention adopts four aspheric lens combinations, and the diaphragm is arranged in front of the first lens, and meanwhile, the optical lens has good imaging quality under the conditions of meeting long focal length, large image surface and reasonable focal power distribution through specific surface shape collocation.

In some embodiments, the effective focal length f of the optical lens and the image height IH corresponding to the maximum half field angle of the optical lens satisfy: f/IH is more than 5.0 and less than 6.0. When the above conditional expression is satisfied, the optical lens can be ensured to have a sufficiently large effective focal length, which is beneficial to increasing the zoom ratio of the optical lens.

In some embodiments, the entrance pupil diameter EPD of the optical lens and the maximum half field angle θ of the optical lens satisfy: 1.6mm < EPD×tan θ < 1.7mm. When the above conditional expression is satisfied, the light inlet amount of the optical lens can be effectively improved, and the imaging quality of the optical lens in a darker environment is ensured.

In some embodiments, the effective focal length f of the optical lens and the total optical length TTL of the optical lens satisfy: 1.0 < f/TTL < 1.3. The optical lens can effectively shorten the total length of the optical lens on the premise of ensuring that the optical lens has a large enough focal length, thereby being beneficial to maintaining the miniaturization of the optical lens.

In some embodiments, the effective focal length f1 of the first lens and the effective focal length f of the optical lens satisfy: f1/f is more than 0.4 and less than 0.5; the radius of curvature R11 of the first lens object-side surface and the radius of curvature R12 of the first lens image-side surface satisfy: -1.5 < (R11+R12)/(R11-R12) < -0.5. When the above conditional expression is satisfied, the light deflection amplitude entering the optical lens can be prevented from being too large, the sensitivity of the optical lens is reduced, meanwhile, the aberration of the optical lens is better balanced, and the imaging quality of the optical lens is improved.

In some embodiments, the effective focal length f1 of the first lens, the effective focal length f2 of the second lens, and the effective focal length f3 of the third lens satisfy: 4.0 < f1×f2/f3 < 16.5. When the above conditional expression is satisfied, the optical lens can better balance aberration, and is beneficial to field curvature correction of the optical lens, and imaging quality of the optical lens is improved.

In some embodiments, the center thickness CT3 of the third lens and the total optical length TTL of the optical lens satisfy: CT3/TTL is more than 0.2 and less than 0.3; the center thickness CT3 of the third lens and the effective focal length f of the optical lens satisfy: CT3/f is more than 0.2 and less than 0.3; the sagittal height SAG31 at the maximum effective aperture of the object-side surface of the third lens and the sagittal height SAG32 at the maximum effective aperture of the image-side surface of the third lens satisfy: 0.7 < SAG31/SAG32 < 1.0. When the conditional expression is satisfied, the influence of the aberration generated by the third lens on the imaging quality of the whole optical lens can be effectively reduced, the surface type complexity of the object side surface and the image side surface of the third lens is reduced, and the processing and production yield is improved.

In some embodiments, the combined focal length f34 of the third lens and the fourth lens and the effective focal length f of the optical lens satisfy: -1.0 < f34/f < -0.5. When the above conditional expression is satisfied, the overall focal length of the optical lens can be increased, the optical zoom magnification of the system is improved, and the long-focus performance of the optical lens is better realized.

In some embodiments, the center thickness CT3 of the third lens, the center thickness CT4 of the fourth lens, the air spacing AT34 between the third lens and the fourth lens AT the paraxial region satisfy: 7.8 < (CT3+AT34)/CT 4 < 12.5. When the above conditional expression is satisfied, the focal power distribution of the third lens and the fourth lens is facilitated, so that the light transition at each lens is smooth, and the overall imaging quality is improved.

In some embodiments, the optical back focal length BFL of the optical lens and the effective focal length f of the optical lens satisfy: BFL/f is more than 0.2 and less than 0.3. When the above conditional expression is satisfied, the optical lens can have larger optical back focus, so that the long focus performance of the optical lens is realized, the interference between the lens and the imaging chip is reduced, the propagation path of light is increased, and the large image surface effect of the optical lens is realized.

In some embodiments, the effective focal length f of the optical lens and the maximum half field angle θ of the optical lens satisfy: f×tan θ is 4.0 < 4.5. When the above conditional expression is satisfied, the optical lens can have a larger focal length, the optical zoom magnification of the optical system is improved, and the optical lens can have a large image plane effect.

In some embodiments, the effective focal length f2 of the second lens and the effective focal length f of the optical lens satisfy: -1.5 < f2/f < -0.5; the radius of curvature R21 of the object-side surface of the second lens and the radius of curvature R22 of the image-side surface of the second lens satisfy: 0.5 < (R21-R22)/(R21+R22) < 4.0. When the condition is satisfied, the optical lens is favorable for better balancing aberration, and meanwhile, the coma aberration and the curvature of field of the off-axis vision field are helped to be corrected, and the imaging quality of the optical lens is improved.

In some embodiments, the effective focal length f3 of the third lens and the effective focal length f of the optical lens satisfy: -3.0 < f3/f < -0.5; the radius of curvature R31 of the third lens object-side surface and the radius of curvature R32 of the third lens image-side surface satisfy: R31/R32 is more than 0 and less than 1.0. When the conditional expression is satisfied, the optical lens is favorable for better balancing aberration, and is favorable for correcting field curvature and distortion and improving the imaging quality of the optical lens.

In some embodiments, the center thickness CT2 of the second lens and the total optical length TTL of the optical lens satisfy: CT2/TTL is more than 0.01 and less than 0.05; the sagittal height SAG21 at the maximum effective aperture of the object-side surface of the second lens and the sagittal height SAG22 at the maximum effective aperture of the image-side surface of the second lens satisfy: -1.3 < SAG21/SAG22 < -0.4. When the conditional expression is satisfied, the astigmatic and coma contribution of the second lens in the whole optical lens can be effectively reduced, and meanwhile, the surface type complexity of the object side surface and the image side surface of the second lens is reduced, and the processing and production yield is improved.

In some embodiments, the center thickness CT1 of the first lens and the center thickness CT2 of the second lens satisfy: CT1/CT2 is more than 4.0 and less than 9.2; the center thickness CT3 of the third lens and the center thickness CT4 of the fourth lens satisfy: CT3/CT4 is more than 7.6 and less than 12.2. When the above conditional expression is satisfied, the focal power distribution among the lenses is facilitated, the light transition at the lenses is facilitated to be smooth, and the overall imaging quality of the optical lens is improved.

As an implementation mode, the first lens, the second lens, the third lens and the fourth lens can all adopt plastic lenses or glass-plastic mixed matching, and good imaging effect can be achieved. In the application, the first lens to the fourth lens are all plastic lenses, and the optical lens can have the advantages of long focal length, large image surface, short total length and high pixels at least by reasonably distributing the focal power of each lens and optimizing the surface shape. Furthermore, the first lens to the fourth lens can be plastic aspherical lenses, and the aspherical lenses can be used for effectively correcting aberration, improving imaging quality and providing optical performance products with higher cost performance.

The invention is further illustrated in the following examples. In various embodiments, the thickness and radius of curvature of each lens in the optical lens may be different, and for specific differences, reference may be made to the parameter tables of the various embodiments. The following examples are merely preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following examples, and any other changes, substitutions, combinations or simplifications that do not depart from the gist of the present invention are intended to be equivalent substitutes within the scope of the present invention.

In various embodiments of the present invention, when an aspherical lens is used as the lens, the surface shape of the aspherical lens satisfies the following equation:

；

where z is the distance sagittal height from the aspherical surface vertex when the aspherical surface is at a position of height h along the optical axis direction, c is the paraxial curvature of the surface, k is the conic coefficient conic, A _2i The aspherical surface profile coefficient of the 2 i-th order.

First embodiment

Referring to fig. 1, a schematic structural diagram of an optical lens 100 according to a first embodiment of the present invention is shown, where the optical lens 100 includes, in order from an object side to an imaging surface S11 along an optical axis: stop ST, first lens L1, second lens L2, third lens L3, fourth lens L4, and filter G1.

The first lens element L1 has positive refractive power, wherein an object-side surface S1 of the first lens element is convex, and an image-side surface S2 of the first lens element is concave at a paraxial region; the second lens element L2 has negative refractive power, wherein an object-side surface S3 of the second lens element is concave at a paraxial region thereof, and an image-side surface S4 of the second lens element is concave; the third lens element L3 has negative refractive power, wherein an object-side surface S5 of the third lens element is concave, and an image-side surface S6 of the third lens element is convex; the fourth lens element L4 has negative refractive power, wherein an object-side surface S7 of the fourth lens element is concave, and an image-side surface S8 of the fourth lens element is convex; the object side surface of the optical filter G1 is S9, and the image side surface is S10; meanwhile, the first lens L1, the second lens L2, the third lens L3 and the fourth lens L4 are all plastic aspherical lenses.

Specifically, the design parameters of each lens of the optical lens 100 provided in the present embodiment are shown in table 1.

TABLE 1

The surface profile coefficients of the aspherical surfaces of the optical lens 100 in this embodiment are shown in table 2.

TABLE 2

Referring to fig. 2, 3 and 4, a distortion curve, a field curvature curve and a vertical axis chromatic aberration curve of the optical lens 100 are shown. As can be seen from fig. 2, the optical distortion is controlled within ±1.0%, indicating that the distortion of the optical lens 100 is well corrected; as can be seen from fig. 3, the curvature of field is controlled within ±0.05mm, which indicates that the curvature of field of the optical lens 100 is better corrected; as can be seen from fig. 4, the vertical chromatic aberration at different wavelengths is controlled within ±1.5 microns, which indicates that the vertical chromatic aberration of the optical lens 100 is well corrected; as can be seen from fig. 2, 3, and 4, the aberration of the optical lens 100 is well balanced, and the optical imaging quality is good.

Second embodiment

Referring to fig. 5, a schematic structural diagram of an optical lens 200 according to a second embodiment of the present invention is shown, and the optical lens 200 according to the present embodiment is substantially the same as the first embodiment described above, and the difference is mainly that the radius of curvature, the aspheric coefficients and the thickness of each lens surface are different.

Specifically, the design parameters of the optical lens 200 provided in this embodiment are shown in table 3.

TABLE 3 Table 3

The surface profile coefficients of the aspherical surfaces of the optical lens 200 in this embodiment are shown in table 4.

TABLE 4 Table 4

Referring to fig. 6, 7 and 8, a distortion curve, a field curvature curve and a vertical axis chromatic aberration curve of the optical lens 200 are shown. As can be seen from fig. 6, the optical distortion is controlled within ±1.0%, indicating that the distortion of the optical lens 200 is well corrected; as can be seen from fig. 7, the curvature of field is controlled within ±0.08mm, which indicates that the curvature of field of the optical lens 200 is better corrected; as can be seen from fig. 8, the vertical chromatic aberration at different wavelengths is controlled within ±3.0 microns, which indicates that the vertical chromatic aberration of the optical lens 200 is well corrected; as can be seen from fig. 6, 7 and 8, the aberration of the optical lens 200 is well balanced, and the optical imaging quality is good.

Third embodiment

Referring to fig. 9, a schematic structural diagram of an optical lens 300 according to a third embodiment of the present invention is shown, and the optical lens 300 of the present embodiment is substantially the same as the first embodiment, and the main differences are that: the fourth lens has positive focal power, and the curvature radius, the aspherical coefficient and the thickness of each lens surface are different.

Specifically, the design parameters of the optical lens 300 provided in this embodiment are shown in table 5.

TABLE 5

The surface profile coefficients of the aspherical surfaces of the optical lens 300 in this embodiment are shown in table 6.

TABLE 6

Referring to fig. 10, 11 and 12, a distortion curve, a field curvature curve and a vertical axis chromatic aberration curve of the optical lens 300 are shown. As can be seen from fig. 10, the optical distortion is controlled within ±1.0%, indicating that the distortion of the optical lens 300 is well corrected; from fig. 11, it can be seen that the curvature of field is controlled within ±0.1mm, which indicates that the curvature of field of the optical lens 300 is better corrected; as can be seen from fig. 12, the vertical chromatic aberration at different wavelengths is controlled within ±3.8 microns, which indicates that the vertical chromatic aberration of the optical lens 300 is well corrected; as can be seen from fig. 10, 11, and 12, the aberration of the optical lens 300 is well balanced, and has good optical imaging quality.

Fourth embodiment

Referring to fig. 13, a schematic structural diagram of an optical lens 400 according to a fourth embodiment of the present invention is shown, and the optical lens 400 according to the present embodiment is substantially the same as the first embodiment described above, except that the radius of curvature, aspheric coefficients, and thicknesses of the lens surfaces are different.

Specifically, the design parameters of the optical lens 400 provided in this embodiment are shown in table 7.

TABLE 7

The surface profile coefficients of the aspherical surfaces of the optical lens 300 in this embodiment are shown in table 8.

TABLE 8

Referring to fig. 13, 14 and 15, a distortion curve, a field curvature curve and a vertical axis chromatic aberration curve of the optical lens 400 are shown. As can be seen from fig. 10, the optical distortion is controlled within ±1.0%, indicating that the distortion of the optical lens 400 is well corrected; from fig. 11, it can be seen that the curvature of field is controlled within ±0.12mm, which indicates that the curvature of field of the optical lens 400 is better corrected; as can be seen from fig. 12, the vertical chromatic aberration at different wavelengths is controlled within ±2.5 microns, which indicates that the vertical chromatic aberration of the optical lens 400 is well corrected; as can be seen from fig. 10, 11, and 12, the aberration of the optical lens 400 is well balanced, and good optical imaging quality is achieved.

Referring to table 9, the optical characteristics of the optical lens provided in the above four embodiments, including the maximum field angle 2θ, the total optical length TTL, the half image height IH, the aperture value FNO, the effective focal length f, and the correlation values corresponding to each of the foregoing conditional expressions, are shown.

TABLE 9

As can be seen from the distortion curve graph, the field curvature graph and the vertical axis chromatic aberration graph of the above embodiments, the distortion value of the optical lens in each embodiment is within +/-1%, the field curvature value is within +/-0.12 mm, and the vertical axis chromatic aberration is within +/-3.8 micrometers, which indicates that the optical lens provided by the embodiment of the invention has the advantages of long focal length, large image plane, short total length and the like, and has good resolving power.

In summary, the optical lens provided by the invention adopts four aspheric lenses with specific focal power, and has the advantages of good imaging quality, long focal length, large image surface and short total length through specific surface shape collocation and reasonable focal power distribution; meanwhile, the optical lens provided by the invention can realize more than 5 times of optical zooming, can bring better imaging effect to distant view, and meets the high-definition imaging requirement of electronic products.

Fifth embodiment

The optical total length of the optical lens provided by any of the embodiments of the present invention exceeds 21mm, and the thickness of the far ultra-portable electronic device cannot be directly applied to the portable electronic device. When the optical lens provided by the invention is used on portable electronic equipment such as a mobile phone, the lens can be designed into a periscope type lens imaging system by utilizing an optical reflecting surface such as a prism and the like, and the periscope type lens imaging system is embedded into the mobile phone so as to meet the requirements of light and thin electronic products.

Referring to fig. 17, a schematic diagram of an optical system 500 according to a fifth embodiment of the invention is shown, wherein the lens assembly is the same as the optical lens (e.g. the optical lens 200) according to any of the above embodiments.

Specifically, the optical system 500 includes, in order from the object side to the imaging plane along the optical axis: a prism P1, a diaphragm ST, and a lens group L (composed of a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4). The prism P1 is arranged at an entrance opening of the lens group L, the first lens L1 is closer to an exit opening of the prism P1 than the fourth lens L4, and incident light enters the lens group L after being turned by the prism P1; the lens group L may be the same as that in the optical lens in any of the above embodiments, that is, the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 have the same structure as the above embodiments.

Further, the prism P1 includes an entrance surface 501, an exit surface 502, and a reflection surface 503. The incident plane 501 is perpendicular to the exit plane 502, and the reflecting plane 503 is at an angle with respect to the incident plane 501 and the exit plane 502. For example, the prism P1 may be an isosceles right-angle prism, that is, the angle between the reflecting surface 503 and the incident surface 501 is 45 °, the angle between the reflecting surface 503 and the emergent surface 502 is also 45 °, when the external light enters the incident surface 501 of the prism P1, the emergent light is formed after passing through the turn of the reflecting surface 503, and exits from the emergent surface 502, that is, the light enters the prism P1 and then enters the lens group after having a turn of 90 °. Therefore, the light path of the optical system 500 can be redirected by the prism, so that the thickness of the optical system in the optical axis direction of the lens set can be effectively reduced, and space is saved for portable electronic products such as mobile phones, so as to meet the development requirement of light and thin portable electronic products. Of course, in other embodiments, the prism may also adopt other prism structures with a reverse form, which is not limited thereto.

According to the embodiment of the invention, the optical system 500 is designed into a periscope type lens imaging system by utilizing the reflection optical surface of one prism, so that the length of incident light rays in the optical axis direction can be greatly reduced, meanwhile, as the optical lens in the optical system 500 has the advantages of long focal length and large image surface, the optical zoom multiple of more than 5 times can be realized, and better imaging effect can be brought to long-range views, so that the optical system 500 can better meet the high-definition imaging requirement of current light and thin electronic products on the long-range views.

In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above examples merely represent a few embodiments of the present invention, which are described in more detail and are not to be construed as limiting the scope of the present invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of the invention should be assessed as that of the appended claims.

Claims

1. An optical lens comprising four lenses in order from an object side to an imaging surface along an optical axis, comprising:

a diaphragm;

a first lens with positive focal power, wherein the object side surface of the first lens is a convex surface;

a second lens having negative optical power, an image side surface of the second lens being a concave surface;

a third lens with negative focal power, wherein the object side surface of the third lens is a concave surface, and the image side surface of the third lens is a convex surface;

a fourth lens element with optical power, wherein an object-side surface of the fourth lens element is concave and an image-side surface of the fourth lens element is convex;

wherein, the effective focal length f of the optical lens and the image height IH corresponding to the maximum half field angle of the optical lens satisfy the following conditions: f/IH is more than 5.0 and less than 6.0; the optical back focal length BFL of the optical lens and the effective focal length f of the optical lens satisfy the following conditions: BFL/f is more than 0.2 and less than 0.3.

2. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

1.6mm＜EPD×tanθ＜1.7mm；

wherein EPD represents the entrance pupil diameter of the optical lens and θ represents the maximum half field angle of the optical lens.

3. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

1.0＜f/TTL＜1.3；

where f represents the effective focal length of the optical lens, and TTL represents the total optical length of the optical lens.

4. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

0.4＜f1/f＜0.5；

-1.5＜(R11+R12)/(R11-R12)＜-0.5；

wherein f1 represents an effective focal length of the first lens, f represents an effective focal length of the optical lens, R11 represents a radius of curvature of an object side surface of the first lens, and R12 represents a radius of curvature of an image side surface of the first lens.

5. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

4.0＜f1×f2/f3＜16.5；

wherein f1 represents an effective focal length of the first lens, f2 represents an effective focal length of the second lens, and f3 represents an effective focal length of the third lens.

6. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

0.2＜CT3/TTL＜0.3；

0.2＜CT3/f＜0.3；

wherein CT3 represents the center thickness of the third lens, TTL represents the total optical length of the optical lens, and f represents the effective focal length of the optical lens.

7. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

-1.0＜f34/f＜-0.5；

wherein f34 represents a combined focal length of the third lens and the fourth lens, and f represents an effective focal length of the optical lens.

8. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

7.8＜(CT3+AT34)/CT4＜12.5；

wherein CT3 represents the center thickness of the third lens, CT4 represents the center thickness of the fourth lens, and AT34 represents the air gap between the third lens and the fourth lens AT the paraxial region.

9. The optical lens according to claim 1, wherein the optical lens satisfies the following conditional expression:

4.0＜f×tanθ＜4.5；

where f represents the effective focal length of the optical lens, and θ represents the maximum half field angle of the optical lens.

10. An optical system, comprising: a prism and an optical lens as claimed in any one of claims 1 to 9; the prism is used for turning incident light so as to enable the incident light to enter the optical lens; the optical lens is positioned on the light emitting side of the prism, and the first lens is arranged closer to the prism than the fourth lens.