CN107728296B

CN107728296B - Optical lens

Info

Publication number: CN107728296B
Application number: CN201610650204.9A
Authority: CN
Inventors: 赖圣棠
Original assignee: Rays Optics Inc
Current assignee: Young Optics Inc
Priority date: 2016-08-10
Filing date: 2016-08-10
Publication date: 2022-03-04
Anticipated expiration: 2036-08-10
Also published as: CN107728296A

Abstract

An optical lens comprises a first lens group, a second lens group and a diaphragm arranged between the first lens group and the second lens group. The first lens group has negative diopter and contains less than 3 diopter lenses, and the second lens group has negative diopterThe group has positive diopter and includes aspheric lenses with diopter less than 5 and the second lens group has diffraction surface. The aspheric lens with the diffraction surface meets the condition that:

wherein

And V is the refractive power, refractive power and Abbe number of the diffraction surface of the lens with the diffraction surface.

Description

Optical lens

Technical Field

The invention relates to an optical lens with a diffraction element and day and night confocal performance.

Background

In recent years, smart home surveillance cameras have been increasingly developed, and demands for reduction in thickness and optical performance have been increasing. To meet such a demand, a lens having low cost, a large aperture, a wide viewing angle, light weight, and a day and night confocal property is generally required. Therefore, there is a need for an image capturing lens design that can achieve both light weight and day and night confocal, and provide lower manufacturing cost and better imaging quality.

Disclosure of Invention

Other objects and advantages of the present invention will be further understood from the technical features disclosed in the embodiments of the present invention.

An embodiment of the present invention provides an optical lens, including a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a stop disposed between the first lens group and the second lens group, wherein the first lens group and the second lens group are sequentially disposed from one direction, the first lens group includes lenses having a refractive power less than 3, the second lens group includes lenses having a refractive power less than 5, and the second lens group includes lenses having a diffractive surface and lenses having a diffractive surface, which satisfy the following conditions:

wherein

By the design of the embodiment of the invention, the optical lens design which can give consideration to light weight and day and night confocal and can provide lower manufacturing cost and better imaging quality can be provided.

Other objects and advantages of the present invention will be further understood from the technical features disclosed in the present invention. In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Drawings

Fig. 1 is a schematic diagram of an optical lens 10a according to an embodiment of the invention.

Fig. 2 to 5 are graphs of imaging optical simulation data of the optical lens of fig. 1, in which fig. 2 to 3 are graphs of light sectors of visible light and 850nm infrared light, respectively, and fig. 4 to 5 are graphs of diffraction optical transfer functions of 587 nm green light and 850nm infrared light, respectively.

Fig. 6 is a schematic diagram of an optical lens 10b according to another embodiment of the invention.

Fig. 7 to 10 are graphs of imaging optical simulation data of the optical lens of fig. 6, in which fig. 7 to 8 are graphs of light sectors of visible light and 850nm infrared light, respectively, and fig. 9 to 10 are graphs of diffraction optical transfer functions of 587 nm green light and 850nm infrared light, respectively.

Reference numerals:

10 a-10 b optical lens

12 optical axis

14 aperture

16 glass cover

18 imaging plane

20 first lens group

30 second lens group

L1-L5 lens

Surface S1-S13

Detailed Description

The foregoing and other technical and scientific aspects, features and advantages of the present invention will be apparent from the following detailed description of the embodiments, which is to be read in connection with the accompanying drawings. Directional terms as referred to in the following examples, for example: up, down, left, right, front or rear, etc., are referred to only in the direction of the attached drawings. Accordingly, the directional terminology is used for purposes of illustration and is in no way limiting.

Fig. 1 is a schematic diagram illustrating an optical lens 10a according to an embodiment of the invention. The optical lens 10a is disposed between an enlargement side (left side in fig. 1; e.g., the object side) and a reduction side (right side in fig. 1; e.g., the image side). As shown in fig. 1, the optical lens 10a includes a first lens group (e.g., a front group) 20 having a negative refractive power and located between the enlargement side and the reduction side, a second lens group (e.g., a rear group) 30 having a positive refractive power and located between the first lens group 20 and the reduction side, and a diaphragm 14 located in a space between the first lens group 20 and the second lens group 30. Furthermore, a glass cover 16 and an image sensor may be disposed on the reduction side, an image plane 18 on the effective focal length of visible light of the optical lens 10a is indicated, and the glass cover 16 is located between the second lens group 30 and the image plane 18 on the effective focal length of visible light. The first lens group 20 may include a first lens L1 and a second lens L2 arranged in order from the enlargement side to the reduction side along the optical axis 12 of the optical lens 10a, and the second lens group 30 may include a third lens L3, a fourth lens L4 and a fifth lens L5 arranged in order from the enlargement side to the reduction side along the optical axis 12 of the optical lens 10a, diopters of the first lens L1 to the fifth lens L5 are respectively negative, positive, negative and positive. In this embodiment, the fourth lens element L4 can be an aspheric lens including a diffractive surface, the first lens element L1, the second lens element L2 and the fifth lens element L5 are aspheric lens elements, and the third lens element L3 is a biconvex lens element. In addition, the first lens L1 to the fifth lens L5 are separated from each other two by two. In an embodiment, two adjacent surfaces of two lenses have the same curvature radius and form a cemented lens, which is not limited by the embodiment of the invention. The lens design parameters, profile, aspheric coefficients and diffraction surface of the optical lens 10a are shown in table one, table two and table three, respectively, and in each of the following design examples of the present invention, the aspheric polynomial can be expressed by the following formula:

in the above formula (1), Z is the offset amount (sag) in the optical axis direction, c is the reciprocal of the radius of the osculating sphere (osculating sphere), that is, the reciprocal of the radius of curvature near the optical axis, k is the conic coefficient (conc), and r is the aspheric height, that is, the height from the lens center to the lens edge. A-D in Table two represent coefficient values of 4 th order, 6 th order, 8 th order and 10 th order of the aspheric surface polynomial, respectively.

In each of the following embodiments of the present invention, the diffraction surface polynomial can be expressed by the following equation:

φ(r)＝(2π/λ₀)∑C_nr²ⁿ (2)；

in the above formula (2), phi (r) is a phase function (phase) of the diffraction element (diffraction optical element), and r is a radial distance (λ) from the optical axis of the optical lens₀Is the reference wavelength (reference wavelength), that is to say the diffraction surface (diffraction optical surface) is the lens surface plus the phase function (phase). C1-C2 in Table III represent the 2 nd order and 4 th order coefficient values of the diffraction surface polynomial, respectively.

Watch 1

The spacing of S1 is the distance between the surfaces S1 and S2 on the optical axis 12, the spacing of S2 is the distance between the surfaces S2 and S3 on the optical axis 12, and the spacing of S13 is the distance between the surface of the glass cover S13 and the imaging plane 18 on the optical axis 12 at the effective focal length of visible light;

the effective focal length of visible light (EFL of visible light) is 3.984 mm;

infrared effective focal length (EFL of NIR 850nm light) 3.981 mm;

the F-Number is 2.0;

field of view (FOV) 103.2 degrees;

maximum imaging Circle (IMA) of the imaging plane at the effective focal length of visible light is 7.54 mm;

the total lens length (total track length, TTL, distance from S1 to the imaging plane at the effective focal length of visible light) is 23.5 mm.

Watch two

	S1	S2	S3	S4
					K	0	0	0	0
A	1.031E-03	-5.591E-04	-1.937E-03	-8.18E-05
					B	-8.090E-05	-1.908E-04	9.177E-06	3.206E-06
C	4.695E-06	-1.152E-05	-1.122E-05	4.662E-06
					D	-9.313E-08	-1.412E-06	1.830E-06	-2.115E-07
	S8	S9	S10	S11
					K	6.593E+00	-6.251E+00	-3.680E+00	2.024E+00
A	-2.157E-03	-4.432E-03	-4.799E-03	4.021E-04
					B
	0	3.055E-04	1.797E-04	-4.327E-05
					C
	0	0	-1.512E-05	0
					D	0	0	5.706E-07	0

Watch III

	S8
		C1	-9.580E-04
C2	-3.751E-05

Fig. 2-3 are ray fan plots (ray fan plots) of visible light and 850nm infrared light, respectively, where the X-axis is the location where the light passes through the entrance pupil and the Y-axis is the relative value of the location where the chief ray is projected onto the image plane (e.g., the imaging plane 18). Fig. 4 to 5 are graphs of imaging optical simulation data of the optical lens 10a of the present embodiment, in which fig. 4 to 5 are graphs of diffraction transfer functions (MTFs) of 587 nm green light and 850nm infrared light, respectively, and a focal plane offset of the two graphs is about 7 μm. Note that the imaged optical simulation data plot can also be plotted using green light at 555 nanometers instead of green light at 587 nanometers. The graphs shown in the simulation data diagrams of fig. 2 to 5 are all within the standard range, so that it can be verified that the optical lens 10a of the present embodiment can have both good optical imaging quality and day and night confocal characteristics.

The optical lens of this embodiment may include two lens groups and the aperture value may be 2.0, and the optical lens may include an aspheric lens having a diffractive surface to correct aberration and chromatic aberration. Further, the following conditions may be satisfied:

20<V<60 (4)；

|(0.5*IMA)/(EFL*TAN(X))-1|<0.3 (5)；

TTL/IMA<3.3 (6)；

wherein

Diffraction surface S8 diopters, C1/(-0.5) in Table III,

the refractive power of the aspheric lens L4, V the abbe number of the aspheric lens L4, EFL the effective focal length of the lens in visible light, IMA the maximum imaging circle of the imaging plane at the effective focal length of visible light, X the 1/2 maximum field angle, and TTL the total lens length (S1 distance to the imaging plane at the effective focal length of visible light). Specifically, it is assumed that the optical lens of the present embodiment is designed to conform to

At this time, the diffraction diopter is large, the number of turns of the diffraction microstructure is large, and the manufacturing difficulty is high. Furthermore, if the optical lens of this embodiment is designed to satisfy | (0.5 × IMA)/(EFL × TAN (X)) -1| (Y |)>0.3, the image deformation amount on the imaging plane on the effective focal length of the visible light is large. If the optical lens of this embodiment is designed to conform to TTL/IMA>3.3, the lens volume is relatively large, which is not favorable for miniaturization. Therefore, the optical lens of the present embodiment is designed to meet the conditions of equations (3), (4), (5) and (6),the optical lens has the characteristics of good optical imaging quality, low manufacturing difficulty and day and night confocal property.

Fig. 6 is a schematic diagram illustrating an optical lens 10b according to another embodiment of the invention. The optical lens 10b is disposed between an enlargement side (left side in fig. 6; e.g., the object side) and a reduction side (right side in fig. 6; e.g., the image side). As shown in fig. 6, the optical lens 10b includes a first lens group (e.g., front group) 20 having a negative refractive power and located between the enlargement side and the reduction side, a second lens group (e.g., rear group) 30 having a positive refractive power and located between the first lens group 20 and the reduction side, and a diaphragm 14 located in a space between the first lens group 20 and the second lens group 30. Furthermore, a glass cover 16 and an image sensor may be disposed on the reduction side, an image plane 18 on the effective focal length of visible light of the optical lens 10b is indicated, and the glass cover 16 is located between the second lens group 30 and the image plane 18 on the effective focal length of visible light. The first lens group 20 may include a first lens L1 and a second lens L2 arranged in order from the enlargement side to the reduction side along the optical axis 12 of the optical lens 10b, and the second lens group 30 may include a third lens L3, a fourth lens L4 and a fifth lens L5 arranged in order from the enlargement side to the reduction side along the optical axis 12 of the optical lens 10b, diopters of the first lens L1 to the fifth lens L5 are respectively negative, positive, negative and positive. In this embodiment, the fifth lens element L5 can be an aspheric lens including a diffractive surface, the first lens element L1, the second lens element L2 and the fourth lens element L4 are aspheric lens elements, and the third lens element L3 is a biconvex lens element. In addition, the first lens L1 to the fifth lens L5 are separated from each other two by two. In an embodiment, two adjacent surfaces of two lenses have the same curvature radius and form a cemented lens, which is not limited by the embodiment of the invention. The lens design parameters, profile, aspheric coefficients and diffraction surface of the optical lens 10b are shown in table four, table five and table six, respectively, wherein a-D in table five represent the values of 4 th order, 6 th order, 8 th order and 10 th order of the aspheric polynomial (shown in formula 1), respectively. C1-C2 in Table six represent the 2 nd order and 4 th order coefficient values of the diffraction surface polynomial (as shown in equation 2).

Watch four

The spacing of S1 is the distance between the surfaces S1 and S2 at the optical axis 12, the spacing of S2 is the distance between the surfaces S2 and S3 at the optical axis 12, and the spacing of S13 is the distance between the surface of the glass cover S13 and the imaging plane 18 at the optical axis 12;

the effective focal length of visible light (EFL of visible light) is 3.883 mm;

infrared effective focal length (EFL of NIR 850nm light) 3.876 mm;

the F-Number is 2.0;

field of view (FOV) 104.9 degrees;

Watch five

	S1	S2	S3	S4
					K
	0	0	0	0
					A	1.658E-03	-6.320E-04	-2.464E-03	-3.682E-04
B	-7.884E-05	-8.546E-05	4.376E-05	1.835E-05
					C	3.126E-06	-5.632E-06	-6.879E-06	3.135E-06
D	-5.407E-08	-1.236E-06	1.078E-06	-1.587E-07
						S8	S9	S10	S11
K	1.692E+01	-7.793E+00	-4.575E+00	2.006E+00
					A	-3.103E-03	-3.109E-03	-4.439E-03	-3.899E-04
B
		0	4.067E-04	2.971E-04	-1.406E-05
C
		0	0	-1.504E-05	0
D						0	0	7.472E-07	0

Watch six

	S11
		C1	-1.048E-03
C2	4.038E-06

Fig. 7-8 are ray fan plots (ray fan plots) of visible light and 850nm infrared light, respectively, where the X-axis is the location where the light passes through the entrance pupil and the Y-axis is the relative value of the location where the chief ray is projected onto the image plane (e.g., the imaging plane 18). Fig. 9 to 10 are graphs of imaging optical simulation data of the optical lens 10b of the present embodiment, in which fig. 9 to 10 are graphs of diffraction transfer functions (MTFs) of 587 nm green light and 850nm infrared light, respectively, and the focal plane offset amounts of the two graphs are about 1 μm. Note that the imaged optical simulation data plot can also be plotted using green light at 555 nanometers instead of green light at 587 nanometers. The graphs shown in the simulation data diagrams of fig. 7 to 10 are all within the standard range, so that it can be verified that the optical lens 10b of the present embodiment can have both good optical imaging quality and day and night confocal characteristics.

20<V<60 (4)；

|(0.5*IMA)/(EFL*TAN(X))-1|<0.3 (5)；

TTL/IMA<3.3 (6)；

wherein

Diffraction surface S11 diopters, which is C1/(-0.5) in Table six,

is aspheric surface transparentThe refractive power of the mirror L5, V is the abbe number of the aspheric lens L5, EFL is the effective focal length of the lens in visible light, IMA is the maximum imaging circle of the imaging plane at the effective focal length of the visible light, X is 1/2 of the maximum field angle, and TTL is the total lens length (S1 distance to the imaging plane at the effective focal length of the visible light). Specifically, it is assumed that the optical lens of the present embodiment is designed to conform to

At this time, the diffraction diopter is large, the number of turns of the diffraction microstructure is large, and the manufacturing difficulty is high. Furthermore, if the optical lens of this embodiment is designed to satisfy | (0.5 × IMA)/(EFL × TAN (X)) -1| (Y |)>0.3, the image deformation on the visible light effective focal length imaging plane is large. If the optical lens of this embodiment is designed to conform to TTL/IMA>3.3, the lens volume is relatively large, which is not favorable for miniaturization. Therefore, the optical lens of the present embodiment is designed to satisfy the conditions of equations (4), (5), (6) and (7), so that the optical lens has good optical imaging quality, low manufacturing difficulty and confocal property at day and night.

The design of the

embodiments

10a and 10b can provide an image capturing lens design that can achieve both light weight and day and night confocal characteristics, and can provide lower manufacturing cost and better imaging quality, and the field angle of the embodiment of the invention can be between 80 degrees and 110 degrees.

Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, not all objects, advantages, or features of the disclosure are necessarily to be achieved in any one embodiment or claimed herein. In addition, the abstract and the title of the invention are provided for assisting the search of patent documents and are not intended to limit the scope of the invention.

Claims

1. An optical lens, comprising:

the first lens group with negative diopter and the second lens group with positive diopter;

an aperture disposed between the first lens group and the second lens group, wherein the optical lens is a fixed focus lens having only one fixed effective focal length of visible light, the first lens group includes two lenses, the second lens group includes three lenses, and the three lenses include a lens having a diffraction surface; and

the lens with the diffraction surface meets the following conditions:

wherein

And V is the diffraction surface diopter, refraction diopter and Abbe number of the lens with the diffraction surface respectively, and the optical lens meets the following conditions:

if 555 nm or 587 nm green light passes through a focal plane of the optical lens as a measurement reference, the optical lens can satisfy the displacement of 850nm infrared light on the focal plane, and the displacement is less than 8 microns away from the measurement reference.

2. An optical lens, comprising:

a first lens group with negative diopter, which comprises two lenses;

a second lens group with positive diopter, which comprises three lenses, wherein one lens comprises a diffraction surface, and the first lens group and the second lens group are arranged in sequence from an object side to an image side;

the optical lens is a fixed focus lens only having a fixed visible light effective focal length value; and

the optical lens meets the following conditions:

|(0.5*IMA)/(EFL*TAN(X))-1|<0.3；

wherein, EFL is the effective focal length of the visible light of the optical lens, IMA is the maximum imaging circle of the imaging plane on the effective focal length of the visible light of the optical lens, and X is 1/2 of the maximum field angle of the optical lens; and

3. An optical lens, comprising:

a first lens group with negative diopter, which comprises two lenses;

a second lens group with positive diopter, wherein the second lens group comprises three lenses, the three lenses comprise a lens with diffraction surfaces, and the total number of the diffraction surfaces of the optical lens is 1;

the aperture is arranged between the first lens group and the second lens group, wherein the optical lens is a fixed focus lens only having a fixed visible light effective focal length value; and

the optical lens meets the following conditions:

TTL/IMA<3.3；

wherein, TTL is the total length of the optical lens, IMA is the maximum imaging circle of the imaging plane on the effective focal length of the visible light of the optical lens; and

4. The optical lens of any of claims 1-3, wherein the lens with the diffractive surface satisfies the following condition:

20<V<60。

5. an optical lens according to any one of claims 1 to 3, wherein the first lens group has negative diopter and includes an aspheric lens with positive diopter and an aspheric lens with negative diopter.

6. An optical lens according to any one of claims 1 to 3, wherein the second lens group has a positive refractive power and includes an aspheric lens with a positive refractive power and an aspheric lens with a negative refractive power.

7. An optical lens as claimed in any one of claims 1 to 3, characterized in that the lens is an aspherical lens.

8. An optical lens according to any one of claims 1-3, wherein the lens of the second lens group closest to the aperture is a spherical lens.

9. An optical lens according to claim 8, wherein the spherical lens satisfies the following condition:

V>70。