CN112505901B

CN112505901B - Optical lens and imaging apparatus

Info

Publication number: CN112505901B
Application number: CN202110170811.6A
Authority: CN
Inventors: 于笑枝; 曾昊杰; 刘绪明; 曾吉勇
Original assignee: Jiangxi Lianyi Optics Co Ltd
Current assignee: Hefei Lianchuang Optical Co.,Ltd.
Priority date: 2021-02-08
Filing date: 2021-02-08
Publication date: 2021-04-27
Anticipated expiration: 2041-02-08
Also published as: CN112505901A

Abstract

The invention discloses an optical lens and imaging equipment, the optical lens includes from the object side to the imaging surface along the optical axis in turn: the first lens with negative focal power has a convex object-side surface and a concave image-side surface; a diaphragm; the image side surface of the second lens is a convex surface; a third lens element having a positive optical power, an object-side surface being concave at a paraxial region and having at least one inflection point, and an image-side surface being convex; a fourth lens element having a negative optical power, an object-side surface of the fourth lens element being convex at a paraxial region and an image-side surface of the fourth lens element being concave at a paraxial region, the object-side surface and the image-side surface of the fourth lens element each having at least one inflection point; the first lens, the second lens, the third lens and the fourth lens are plastic aspheric lenses. The optical lens can realize the miniaturization and high-pixel balance of the wide-angle lens, and can effectively improve the shooting experience of a user.

Description

Optical lens and imaging apparatus

Technical Field

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

Background

The optical lens is an important component in an optical imaging system and is one of the standard configurations of terminals such as mobile phones, flat panels, security monitoring equipment, automobile data recorders and the like. In recent years, with the development of mobile information technology, the demand of terminals has increased, and the number of optical lenses mounted on the terminals has also increased.

With the enthusiasm of users for the light and thin terminal, in order to pursue a better imaging effect, the optical lens is required to meet the miniaturization requirement and have the characteristic of wide viewing angle.

Disclosure of Invention

To this end, an object of the present invention is to provide an optical lens and an imaging apparatus for solving the above problems.

The embodiment of the invention implements the above object by the following technical scheme.

In a first aspect, the present invention provides an optical lens, comprising, in order from an object side to an image plane along an optical axis: the lens comprises a first lens with negative focal power, a second lens and a third lens, wherein the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface; a diaphragm; the second lens has positive focal power, and the image side surface of the second lens is a convex surface; a third lens having a positive optical power, an object-side surface of the third lens being concave at a paraxial region and having at least one inflection point, an image-side surface of the third lens being convex; a fourth lens having a negative optical power, an object-side surface of the fourth lens being convex at a paraxial region, an image-side surface of the fourth lens being concave at a paraxial region, and both the object-side surface and the image-side surface of the fourth lens having at least one inflection point; the first lens, the second lens, the third lens and the fourth lens are plastic aspheric lenses; the optical lens satisfies the following conditional expression: 1.6< TTL/IH < 1.7; wherein, TTL represents the optical total length of the optical lens, and IH represents the actual half-image height of the optical lens.

In a second aspect, the present invention provides an imaging apparatus, comprising an imaging element and the optical lens provided in the first aspect, wherein the imaging element is configured to convert an optical image formed by the optical lens into an electrical signal.

Compared with the prior art, the optical lens and the imaging equipment provided by the invention have the advantages that the lens shapes and focal powers among the four lenses with specific refractive powers are reasonably matched, the high-pixel requirement is met, the structure is more compact, the miniaturization and high-pixel balance of the wide-angle lens are better realized, and the shooting experience of a user can be effectively improved.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

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

FIG. 2 is an astigmatism graph of an optical lens according to a first embodiment of the present invention;

FIG. 3 is a graph showing optical distortion 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 an astigmatism graph of an optical lens according to a second embodiment of the present invention;

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

FIG. 7 is a vertical axis chromatic aberration diagram of an optical lens according to a second embodiment of the present invention;

FIG. 8 is an astigmatism graph of an optical lens according to a third embodiment of the present invention;

fig. 9 is a graph showing an optical distortion of an optical lens in a third embodiment of the present invention;

FIG. 10 is a vertical axis chromatic aberration diagram of an optical lens according to a third embodiment of the present invention;

fig. 11 is a schematic structural view of an image forming apparatus according to a fourth embodiment of the present invention.

Detailed Description

In order to make the objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. Several embodiments of the invention are presented in the drawings. 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. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The present invention provides an optical lens, which includes, in order from an object side to an image plane, a first lens, a diaphragm, a second lens, a third lens, a fourth lens and a filter, where the object side is a side opposite to the image plane.

The first lens has negative 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 concave surface.

The second lens has positive focal power, and the image side surface of the second lens is a convex surface.

The third lens element has a positive optical power, an object-side surface of the third lens element being concave at a paraxial region and having at least one inflection point, and an image-side surface of the third lens element being convex.

The fourth lens element has a negative optical power, an object-side surface of the fourth lens element is convex at a paraxial region, an image-side surface of the fourth lens element is concave at a paraxial region, and both the object-side surface and the image-side surface of the fourth lens element have at least one inflection point.

As an embodiment, the optical lens satisfies the following conditional expression:

1.6<TTL/IH<1.7；（1）

wherein, TTL represents the total optical length of the optical lens, and IH represents the actual half-image height of the optical lens.

When the conditional expression (1) is satisfied, the optical total length of the optical lens can be reasonably controlled, and the miniaturization of the lens and the balance of a wide visual angle are favorably realized.

As an embodiment, the optical lens may further satisfy the following conditional expression:

0.5<DM1/tan(HFOV) <0.51；（2）

where DM1 denotes an effective half aperture of the first lens, and HFOV denotes a maximum half angle of view of the optical lens.

When the condition formula (2) is satisfied, the field depth of the optical lens can be reasonably controlled, the head size of the optical lens is reduced, the window opening area of the screen of the portable electronic device is reduced, and the screen occupation ratio of the portable electronic device is improved.

-0.15<f/f1<-0.05；（3）

2.65<DM4/DM1<2.75；（4）

where f denotes a focal length of the optical lens, f1 denotes a focal length of the first lens, DM1 denotes an effective half aperture of the first lens, and DM4 denotes an effective half aperture of the fourth lens.

When the conditional expressions (3) and (4) are satisfied, the imaging space depth and the effective focal length of the optical lens can be reasonably controlled, the super-large wide angle of the optical lens can be favorably realized, meanwhile, the effective calibers of the first lens and the fourth lens can be reasonably controlled, and the miniaturization of the optical lens can be favorably realized.

0.13< (CT1+CT2)/TTL<0.17；（5）

where CT1 denotes the center thickness of the first lens, CT2 denotes the center thickness of the second lens, and TTL denotes the total optical length of the optical lens.

When satisfying conditional expression (5), can rationally control the thickness of first lens and second lens, make first lens and second lens satisfy thin lens design, be favorable to rectifying aberration and optical distortion, simultaneously, can maintain the light flux volume, be favorable to the promotion of relative illuminance.

0.045< CT12/TTL<0.060；（6）

1.2< CT23/CT2<1.9；（7）

where CT2 denotes a center thickness of the second lens, CT12 denotes an air space between the first lens and the second lens on the optical axis, CT23 denotes an air space between the second lens and the third lens on the optical axis, and TTL denotes an optical total length of the optical lens.

When the conditional expressions (6) and (7) are met, the air intervals among the lenses are reasonably distributed, so that the total optical length of the optical lens can be shortened, meanwhile, the matching among the lenses can be reasonably controlled, the sensitivity of the optical lens can be reduced, and the product yield can be improved.

7<(R1+R2)/(R1-R2)<13；（8）

3.2<R2/tan(θ2)<3.9；（9）

where R1 denotes a radius of curvature of the object-side surface of the first lens, R2 denotes a radius of curvature of the image-side surface of the first lens, and θ 2 denotes a maximum surface inclination angle of the image-side surface of the first lens.

When the conditional expressions (8) and (9) are met, the surface shape of the first lens can be reasonably controlled, the focal power of the first lens is enhanced, the system can well correct aberration under large aperture, and the aperture of the subsequent lens and the total length of the optical lens are reduced.

0.4<f3/f2<3.2；（10）

where f2 denotes a focal length of the second lens, and f3 denotes a focal length of the third lens.

When the conditional expression (10) is satisfied, the refractive power balance distribution of the second lens element and the third lens element can be realized, which is beneficial to correcting the aberration of the optical lens and improving the resolving power of the optical lens.

-3<R5/f<-1；（11）

1.3<f/f3<2.0；（12）

where f denotes a focal length of the optical lens, R5 denotes a radius of curvature of the object side surface of the third lens, and f3 denotes a focal length of the third lens.

When the conditional expressions (11) and (12) are satisfied, the focal length of the third lens can be reasonably controlled, which is beneficial to correcting the optical distortion of the optical lens and reducing the aberration of the off-axis field.

0.8<YSAG5/DM31<1.0；（13）

where YSAG5 denotes the perpendicular distance of the inflection point on the object-side surface of the third lens element from the optical axis, and DM31 denotes the effective half aperture of the object-side surface of the third lens element.

When the conditional expression (13) is satisfied, the position of the inflection point on the object side surface of the third lens can be reasonably set, the imaging quality is favorably improved, the sensitivity of the third lens is reduced, and the production yield is improved.

0< Nd1- Nd2<0.15；（14）

30<V2-V1<36；（15）

where Nd1 denotes a refractive index of the first lens, Nd2 denotes a refractive index of the second lens, V1 denotes an abbe number of the first lens, and V2 denotes an abbe number of the second lens.

When conditional expressions (14) and (15) are satisfied, chromatic aberration correction and improvement of image power of the optical lens are facilitated.

In an embodiment, the first lens, the second lens, the third lens and the fourth lens may be aspheric lenses, and optionally, the lenses are plastic aspheric lenses. By adopting the aspheric lens, the number of the lenses can be effectively reduced, aberration can be corrected, and better optical performance can be provided.

Further, as an embodiment, when each lens in the optical lens is an aspherical lens, each aspherical surface type of the optical lens may satisfy the following equation:

，

wherein z is the distance rise from the aspheric surface vertex when the aspheric surface is at the position with the height h along the optical axis direction, c is the paraxial curvature of the surface, k is the conic coefficient, A_2iIs the aspheric surface type coefficient of 2i order.

According to the optical lens, the four lenses with specific refractive power are adopted, and the lens shapes and focal power combinations among the first lens, the second lens, the third lens and the fourth lens are reasonably matched, so that the structure is more compact on the premise of meeting the requirement of high pixel of the lens, the miniaturization and high pixel balance of the lens are better realized, and the shooting experience of a user can be effectively improved.

The invention is further illustrated below in the following examples. In each of the following embodiments, the thickness and the radius of curvature of each lens in the optical lens are different, and specific differences can be referred to in the parameter tables in the embodiments.

First embodiment

Referring to fig. 1, an optical lens 100 according to a first embodiment of the present invention sequentially includes, from an object side to an image plane: a first lens L1, a stop ST, a second lens L2, a third lens L3, a fourth lens L4 and a filter G.

The first lens element L1 has negative power, the object-side surface S1 of the first lens element is convex, and the image-side surface S2 of the first lens element is concave.

The second lens L2 has positive refractive power, and the object-side surface S3 and the image-side surface S4 of the second lens are convex.

The third lens L3 has positive power, an object-side surface S5 of the third lens is concave at the paraxial region and has at least one inflection point, and an image-side surface S6 of the third lens is convex.

The fourth lens element L4 has negative power, the object-side surface S7 of the fourth lens element is convex at the paraxial region, the image-side surface S8 of the fourth lens element is concave at the paraxial region, and both the object-side surface S7 and the image-side surface S8 of the fourth lens element have at least one inflection point.

Referring to table 1, related parameters of each lens of the optical lens 100 according to the first embodiment of the invention are shown. In the first embodiment of the present invention, the vertical distance between the inflection point of the object-side surface S5 of the third lens and the optical axis is 0.845 mm.

TABLE 1

Referring to table 2, the surface coefficients of the aspheric surfaces of the optical lens 100 according to the first embodiment of the present invention are shown.

TABLE 2

Referring to fig. 2, fig. 3 and fig. 4, an astigmatism graph, a distortion graph and a vertical axis chromatic aberration graph of the optical lens 100 of the first embodiment are respectively shown.

The astigmatism curve of fig. 2 indicates the degree of curvature of the meridional image plane and the sagittal image plane. In fig. 2, the horizontal axis represents the offset amount (unit: mm) and the vertical axis represents the angle of view (unit: degree). As can be seen from fig. 2, astigmatism of the meridional image plane and the sagittal image plane is controlled to be within ± 0.10 mm, which indicates that the astigmatism correction of the optical lens 100 is good.

Figure 3 distortion curves represent the distortion at different image heights on the imaging plane. In fig. 3, the horizontal axis represents the f-tan θ distortion value (percentage), and the vertical axis represents the angle of view (unit: degree). As can be seen from fig. 3, the f-tan θ distortion at different image heights on the image plane is controlled within ± 13%, indicating that the distortion of the optical lens 100 is well corrected.

The vertical axis chromatic aberration curve of fig. 4 shows chromatic aberration at different image heights on the image forming surface for the longest wavelength and the shortest wavelength. In fig. 4, the horizontal axis represents the homeotropic color difference (unit: μm) of each wavelength with respect to the center wavelength, and the vertical axis represents the normalized angle of view. As can be seen from fig. 4, the vertical chromatic aberration of the longest wavelength and the shortest wavelength are controlled within ± 3 microns, which indicates that the vertical chromatic aberration of the optical lens 100 is well corrected.

Second embodiment

The optical lens system provided in the second embodiment of the present invention has substantially the same structure as the optical lens system 100 provided in the first embodiment, and mainly differs in the radius of curvature and material selection of each lens. In the second embodiment of the present invention, the vertical distance between the inflection point of the object-side surface S5 of the third lens and the optical axis is 0.795 mm.

Referring to table 3, parameters related to each lens in an optical lens system according to a second embodiment of the present invention are shown.

TABLE 3

Referring to table 4, the surface coefficients of the aspheric surfaces of the optical lens according to the second embodiment of the present invention are shown.

TABLE 4

Referring to fig. 5, 6 and 7, an astigmatism graph, a distortion graph and a vertical axis chromatic aberration graph of the optical lens of the second embodiment are shown, respectively.

The astigmatism curve of fig. 5 indicates the degree of curvature of the meridional image plane and the sagittal image plane. As can be seen from fig. 5, astigmatism in the meridional image plane and the sagittal image plane is controlled to within ± 0.1 mm, which indicates that the optical lens of the second embodiment has good astigmatism correction.

Fig. 6 distortion curves represent the distortion at different image heights on the imaging plane. As can be seen from fig. 6, the f-tan θ distortion at different image heights on the image plane is controlled to be within ± 13%, indicating that the distortion of the optical lens of the second embodiment is well corrected.

The vertical axis chromatic aberration curve of fig. 7 shows chromatic aberration at different image heights on the image forming surface for the longest wavelength and the shortest wavelength. As can be seen from fig. 7, the vertical chromatic aberration of the longest wavelength and the shortest wavelength are controlled within ± 3 μm, which indicates that the vertical chromatic aberration of the optical lens of the second embodiment is well corrected.

Third embodiment

The optical lens system provided in the third embodiment of the present invention has substantially the same structure as the optical lens system 100 provided in the first embodiment, and mainly differs in the radius of curvature and material selection of each lens. In the third embodiment of the present invention, the vertical distance between the inflection point of the object-side surface S5 of the third lens and the optical axis is 0.845 mm.

Referring to table 5, parameters related to each lens in an optical lens system according to a third embodiment of the present invention are shown.

TABLE 5

Referring to table 6, the surface coefficients of the aspheric surfaces of the optical lens 100 according to the third embodiment of the present invention are shown.

TABLE 6

Referring to fig. 8, 9 and 10, an astigmatism graph, a distortion graph and a vertical axis chromatic aberration graph of the optical lens of the third embodiment are shown, respectively.

The astigmatism curve of fig. 8 indicates the degree of curvature of the meridional image plane and the sagittal image plane. As can be seen from fig. 8, astigmatism in the meridional image plane and the sagittal image plane is controlled to within ± 0.11 mm, which indicates that the optical lens of the third embodiment has good astigmatism correction.

Fig. 9 distortion curves represent the distortion at different image heights on the imaging plane. As can be seen from fig. 9, the f-tan θ distortion at different image heights on the image forming surface S11 is controlled within ± 13%, which indicates that the distortion of the optical lens of the third embodiment is corrected well.

The vertical axis chromatic aberration curve of fig. 10 shows chromatic aberration at different image heights on the image forming surface for the longest wavelength and the shortest wavelength. As can be seen from fig. 10, the vertical chromatic aberration of the longest wavelength and the shortest wavelength are controlled within ± 3 μm, which indicates that the vertical chromatic aberration of the optical lens of the third embodiment is well corrected.

Referring to table 7, optical characteristics corresponding to the optical lenses provided in the three embodiments are shown. The optical characteristics mainly include a focal length F, an F # of the optical lens, an entrance pupil diameter EPD, a total optical length TTL, and a field angle FOV of the optical lens, and a correlation value corresponding to each of the aforementioned conditional expressions.

TABLE 7

In summary, the optical lens provided by the invention has the following advantages:

(1) because the shapes of the diaphragm and each lens are reasonably arranged, on one hand, the outer diameter of the head part of the lens can be made smaller, so that the optical lens has smaller windowing caliber, and the requirement of high screen ratio is met; on the other hand, the total length of the optical lens is shorter (TTL is less than or equal to 3.76 mm), the volume is smaller, and the development trend of light and thin portable electronic products can be better met.

(2) Four plastic aspheric lenses with specific refractive power are adopted, and the lenses are matched through specific surface shapes, so that the optical lens has ultrahigh pixel imaging quality.

(3) The field angle of the optical lens can reach 105 degrees, the optical distortion can be effectively corrected, the optical distortion is controlled within +/-13 percent, and the requirements of large field angle and high-definition imaging can be met.

Fourth embodiment

Referring to fig. 11, a fourth embodiment of the invention provides an imaging device 200, where the imaging device 200 includes an imaging element 210 and an optical lens (e.g., the optical lens 100) in any of the embodiments described above. The imaging element 210 may be a CMOS (Complementary Metal Oxide Semiconductor) image sensor, and may also be a CCD (Charge Coupled Device) image sensor.

The imaging device 200 may be a smartphone, Pad, or any other form of portable electronic device that incorporates the optical lens described above.

The imaging device 200 provided by the embodiment of the application includes the optical lens 100, and since the optical lens 100 has the advantages of small size, wide viewing angle and high pixels, the imaging device 200 having the optical lens 100 also has the advantages of small size, wide viewing angle and high pixels.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean 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 invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. 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 are merely illustrative of several embodiments of the present invention, and the description thereof is more specific and detailed, but not to be construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. An optical lens, comprising, in order from an object side to an image plane along an optical axis:

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

a diaphragm;

the second lens has positive focal power, and the image side surface of the second lens is a convex surface;

a third lens having a positive optical power, an object-side surface of the third lens being concave at a paraxial region and having at least one inflection point, an image-side surface of the third lens being convex;

a fourth lens having a negative optical power, an object-side surface of the fourth lens being convex at a paraxial region, an image-side surface of the fourth lens being concave at a paraxial region, and both the object-side surface and the image-side surface of the fourth lens having at least one inflection point;

the optical lens comprises four lenses with focal power, and the first lens, the second lens, the third lens and the fourth lens are plastic aspheric lenses;

the optical lens satisfies the following conditional expression: 1.6< TTL/IH < 1.7;

wherein, TTL represents the optical total length of the optical lens, IH represents the actual half-image height of the optical lens;

the optical lens satisfies the conditional expression: 0.5mm < DM1/tan (hfov) <0.51 mm;

where DM1 denotes an effective half aperture of the first lens, and HFOV denotes a maximum half field angle of the optical lens.

2. An optical lens according to claim 1, wherein the optical lens satisfies the conditional expression: -0.15< f/f1< -0.05; 2.65< DM4/DM1< 2.75;

3. An optical lens according to claim 1, wherein the optical lens satisfies the conditional expression: 0.13< (CT1+ CT2)/TTL < 0.17;

wherein CT1 represents the center thickness of the first lens and CT2 represents the center thickness of the second lens.

4. An optical lens according to claim 1, wherein the optical lens satisfies the conditional expression: 0.045< CT12/TTL < 0.060; 1.2< CT23/CT2< 1.9;

wherein CT2 denotes a center thickness of the second lens, CT12 denotes an air space on an optical axis between the first lens and the second lens, and CT23 denotes an air space on an optical axis between the second lens and the third lens.

5. An optical lens according to claim 1, wherein the optical lens satisfies the conditional expression: 7< (R1+ R2)/(R1-R2) < 13; 3.2mm < R2/tan (θ 2) <3.9 mm;

wherein R1 denotes a radius of curvature of an object-side surface of the first lens, R2 denotes a radius of curvature of an image-side surface of the first lens, and θ 2 denotes a maximum surface inclination angle of the image-side surface of the first lens.

6. An optical lens according to claim 1, wherein the optical lens satisfies the conditional expression: 0.4< f3/f2< 3.2;

wherein f2 denotes a focal length of the second lens, and f3 denotes a focal length of the third lens.

7. An optical lens according to claim 1, wherein the optical lens satisfies the conditional expression: -3< R5/f < -1; 1.3< f/f3< 2.0;

wherein R5 denotes a radius of curvature of an object side surface of the third lens, f denotes a focal length of the optical lens, and f3 denotes a focal length of the third lens.

8. An optical lens according to claim 1, wherein the optical lens satisfies the conditional expression: 0.8< YSAG 5/DM 31< 1.0;

where YSAG5 represents the perpendicular distance of the inflection point on the object-side surface of the third lens element from the optical axis, and DM31 represents the effective half aperture of the object-side surface of the third lens element.

9. An optical lens according to claim 1, wherein the optical lens satisfies the conditional expression: 0< Nd1-Nd2< 0.15; 30< V2-V1 < 36;

wherein Nd1 denotes a refractive index of the first lens, Nd2 denotes a refractive index of the second lens, V1 denotes an abbe number of the first lens, and V2 denotes an abbe number of the second lens.

10. An imaging apparatus comprising the optical lens according to any one of claims 1 to 9 and an imaging element for converting an optical image formed by the optical lens into an electric signal.