CN210323549U - Fixed focus lens - Google Patents

Abstract

The embodiment of the utility model discloses tight shot is disclosed. The fixed-focus lens comprises a first lens with negative focal power, a second lens with negative focal power, a third lens with positive focal power, a fourth lens with positive focal power, a fifth lens with negative focal power and a sixth lens with positive focal power which are sequentially arranged from an object side to an image side along an optical axis; the fourth lens is a glass spherical lens; the first lens, the second lens, the third lens, the fifth lens and the sixth lens are all plastic aspheric lenses. The technical scheme of the embodiment of the utility model, the mixed optical structure is moulded to glass that adopts a slice glass lens and five plastic lens, and make full use of plastics aspheric lens aberration elimination, the infrared function is corrected to glass lens, can be under F1.8's prerequisite, make visible and all can reach the 4K resolution ratio requirement under the infrared light, the camera lens does not run burnt under ambient temperature-40 ℃ -80 ℃ state simultaneously, both the cost is reduced has guaranteed the performance again.

Description

Fixed focus lens

Technical Field

The embodiment of the utility model provides a relate to the camera lens technique, especially relate to a tight shot.

Background

The progress of science and technology brings convenience to human beings, and along with the improvement of safety consciousness of people, the security protection also has higher-level requirements. The monitoring lens converts the shot target into an image signal, and transmits the image signal to an image processing and identifying system, so that accurate image information is stored for places such as roads, markets, schools and the like, and data is provided for information acquisition and query.

With the technical development of the communication industry and the gradual popularization of 5G, the shot video is not limited by the transmission speed and the bandwidth. And the requirement of people for monitoring the image quality is higher and higher. So 4K (3840 × 2160) resolution monitoring cameras are gradually beginning to be accepted. The traditional 4K lens generally uses a large number of lenses, and has the problems of large volume, high manufacturing cost and the like.

SUMMERY OF THE UTILITY MODEL

The embodiment of the utility model provides a tight shot, this tight shot adopts a slice glass lens and five plastic lens's glass to mould mixed optical structure, and the aberration elimination of make full use of plastics aspheric lens, and the infrared function is corrected to glass lens, can make under F1.8's prerequisite, all can reach 4K resolution ratio requirement under visible and the infrared light, and the camera lens does not run burnt under ambient temperature-40 ℃ -80 ℃ state simultaneously, has both reduced the cost, has guaranteed the performance again.

The embodiment of the utility model provides a fixed focus camera lens, include the first lens of negative focal power, the second lens of negative focal power, the third lens of positive focal power, the fourth lens of positive focal power, the fifth lens of negative focal power and the sixth lens of positive focal power that follow optical axis and arrange in proper order from the object space to the image space;

wherein the fourth lens is a glass spherical lens;

the first lens, the second lens, the third lens, the fifth lens and the sixth lens are all plastic aspheric lenses.

Optionally, focal lengths of the third lens and the fourth lens and the focal length of the fixed-focus lens satisfy the following relation:

1.8<︱f3/f︱<2.1；

1.8<︱f4/f︱<2.1；

wherein f3, f4, and f denote focal lengths of the third lens, the fourth lens, and the prime lens, respectively.

Optionally, the first lens to the sixth lens satisfy the following parameters:

f1＝-5.3～-6.5	n1＝1.48～1.68	R1＝43～56	R2＝2.05～3.15
				f2＝-28～-32.5	n2＝1.55～1.75	R3＝-3.05～-4.45	R4＝-3.8～-5.2
f3＝8.1～9.6	n3＝1.48～1.68	R5＝6.8～7.9	R6＝-12.5～-14.5
				f4＝8.1～9.6	n4＝1.48～1.68	R7＝7.3～8.8	R8＝-7.3～-8.8
f5＝-5.8～-6.8	n5＝1.56～1.76	R9＝-41～-48	R10＝4.5～5.6
				f6＝6.8～7.5	n6＝1.48～1.68	R11＝4.1～4.8	R12＝-26.5～-30.8

wherein f1 to f6 represent focal lengths of the first lens to the sixth lens in mm, n1 to n6 represent refractive indices of the first lens to the sixth lens, R1, R3, R5, R7, R9, and R11 represent radii of curvature of the first lens to the sixth lens toward the center of the object side surface in this order, R2, R4, R6, R8, R10, and R12 represent radii of curvature of the first lens to the sixth lens toward the center of the image side surface in this order, respectively, in mm, and "-" represents a negative direction.

Optionally, the optical module further includes a diaphragm disposed between the third lens and the fourth lens.

Optionally, the fourth lens is a biconvex lens.

Optionally, the first lens is a meniscus lens, the second lens is a meniscus lens, the third lens is a biconvex lens, the fifth lens is a biconcave lens, and the sixth lens is a biconvex lens.

Optionally, the first lens and the second lens are tightly matched through a soma, and the fifth lens and the sixth lens are tightly matched through a soma.

Optionally, the second lens and the third lens are tightly fitted through a spacer, the third lens and the fourth lens are tightly fitted through a spacer, and the fourth lens and the fifth lens are tightly fitted through a spacer.

Optionally, the surface type of the plastic aspheric lens satisfies the formula:

wherein z represents a rise in a distance from a vertex of the aspherical surface when the aspherical surface is at a position having a height y in the optical axis direction,

r represents a curvature radius of the face center, k represents a conic coefficient, and A, B, C, D, E, F represents a high-order aspherical coefficient.

Optionally, the aperture F of the fixed-focus lens is greater than or equal to 1.8.

The embodiment of the utility model provides a fixed focus camera lens, include the first lens of negative focal power, the second lens of negative focal power, the third lens of positive focal power, the fourth lens of positive focal power, the fifth lens of negative focal power and the sixth lens of positive focal power that arrange along the optical axis in proper order from the object space to the image space; the fourth lens is a glass spherical lens; the others are all plastic aspheric lenses. By adopting the glass-plastic mixed optical structure of one glass lens and five plastic lenses, the plastic aspheric lens has smaller quality and lower cost and has good aberration eliminating capability; the glass spherical lens is easy to process, has small temperature deformation, is beneficial to realizing high-low temperature infrared confocal, can meet the requirement of 4K resolution ratio under visible light and infrared light on the premise of F1.8 by matching the focal power of each lens, can be matched with a 1/2.5 inch chip with 4K resolution ratio, and simultaneously, the lens does not generate focus under the state of ambient temperature of minus 40 ℃ to 80 ℃, thereby reducing the cost and ensuring the performance.

Drawings

Fig. 1 is a schematic structural diagram of a fixed focus lens provided in an embodiment of the present invention;

fig. 2 is a schematic diagram of an MTF curve of a modulation transfer function of visible light according to an embodiment of the present invention;

fig. 3 is a schematic diagram of an MTF curve of infrared light provided by an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. It should be noted that the terms "upper", "lower", "left", "right", and the like used in the embodiments of the present invention are described in terms of the drawings, and should not be construed as limiting the embodiments of the present invention. In addition, in this context, it is also to be understood that when an element is referred to as being "on" or "under" another element, it can be directly formed on "or" under "the other element or be indirectly formed on" or "under" the other element through an intermediate element. The terms "first," "second," and the like, are used for descriptive purposes only and not for purposes of limitation, and do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

Fig. 1 is a schematic structural diagram of a fixed focus lens according to an embodiment of the present invention. Referring to fig. 1, the fixed focus lens provided in the present embodiment includes a first lens 10 with negative refractive power, a second lens 20 with negative refractive power, a third lens 30 with positive refractive power, a fourth lens 40 with positive refractive power, a fifth lens 50 with negative refractive power, and a sixth lens 60 with positive refractive power, which are arranged in this order from the object side to the image side along the optical axis; wherein the fourth lens 40 is a glass spherical lens; the first lens 10, the second lens 20, the third lens 30, the fifth lens 50, and the sixth lens 60 are all plastic aspherical lenses.

It will be appreciated that the optical power is equal to the difference between the image-side and object-side beam convergence, which characterizes the ability of the optical system to deflect light. The larger the absolute value of the focal power is, the stronger the bending ability to the light ray is, and the smaller the absolute value of the focal power is, the weaker the bending ability to the light ray is. When the focal power is positive, the refraction of the light is convergent; when the focal power is negative, the refraction of the light is divergent. The optical power can be suitable for representing a certain refractive surface of a lens (namely, a surface of the lens), can be suitable for representing a certain lens, and can also be suitable for representing a system (namely a lens group) formed by a plurality of lenses together. In the present embodiment, each lens can be fixed in one lens barrel (not shown in fig. 1), by reasonably distributing the optical power and the shape of the lens, for example, a first lens 10 and a second lens 20 with negative optical power are provided, and the light receiving surface of the first lens 10 is larger for receiving light, so as to increase the field angle; by arranging the fourth lens 40 as a glass spherical lens, the spherical lens is easy to process, the cost can be reduced, the glass material has small deformation along with temperature change, and high and low temperature confocal is realized; the first lens 10, the second lens 20, the third lens 30, the fifth lens 50 and the sixth lens 60 are all plastic aspheric lenses, the aspheric lenses are fully utilized to eliminate various aberrations, the plastic lenses are low in cost and easy to form, the lens can realize day and night confocal function within the wavelength range of 436nm to 850nm, optionally, the aperture F of the fixed-focus lens provided by the embodiment is larger than or equal to 1.8, the fixed-focus lens can be matched with a 1/2.5-inch 4K imaging chip, and the fixed-focus lens has the function of realizing visible light and infrared confocal at the ambient temperature of-40 ℃ to 80 ℃.

According to the technical scheme of the embodiment, by adopting the glass-plastic mixed optical structure of one glass lens and five plastic lenses, the plastic aspheric lens has smaller mass and lower cost and has good aberration eliminating capability; the glass spherical lens is easy to process, has small temperature deformation, is beneficial to realizing high-low temperature infrared confocal, can meet the requirement of 4K resolution ratio under visible light and infrared light on the premise of F1.8 by matching the focal power of each lens, can be matched with a 1/2.5 inch chip with 4K resolution ratio, and simultaneously, the lens does not generate focus under the state of ambient temperature of minus 40 ℃ to 80 ℃, thereby reducing the cost and ensuring the performance.

On the basis of the above technical solution, optionally, the focal lengths of the third lens 30 and the fourth lens 40 and the focal length of the fixed-focus lens satisfy the following relation:

1.8<︱f3/f︱<2.1 (1)；

1.8<︱f4/f︱<2.1 (2)；

where f3, f4, and f denote focal lengths of the third lens 30, the fourth lens 40, and the prime lens, respectively.

According to the fixed-focus lens provided by the embodiment, the third lens 30 and the fourth lens 40 are arranged to have positive focal power, the ratio range of the focal lengths of the third lens 30, the fourth lens 40 and the fixed-focus lens is given, the fourth lens 40 made of glass can compensate the focal length deviation of the plastic aspheric lens along with the temperature, the confocal effect of the fixed-focus lens at high and low temperatures is ensured, and the resolution of 4K is achieved.

Alternatively, the first lens 10 to the sixth lens 60 satisfy the following parameters:

TABLE 1 lens parameters

Where f1 to f6 indicate focal lengths of the first lens 10 to the sixth lens 60 in mm, n1 to n6 indicate refractive indices of the first lens 10 to the sixth lens 60, R1, R3, R5, R7, R9, and R11 indicate radii of curvature of the first lens 10 to the sixth lens 60 toward the center of the object-side surface in that order, R2, R4, R6, R8, R10, and R12 indicate radii of curvature of the first lens 10 to the sixth lens 60 toward the center of the image-side surface in that order, and the unit is mm, and "-" indicates a negative direction.

Optionally, with continuing reference to fig. 1, an embodiment of the present invention provides a fixed focus lens further including a diaphragm 70 disposed between the third lens 30 and the fourth lens 40. The diaphragm 70 can adjust the size of the view field, shield the far-axis light, avoid the far-axis light from influencing the imaging quality and improve the image quality.

Alternatively, the fourth lens 40 is a biconvex lens. Alternatively, the first lens element 10 is a meniscus lens element, the second lens element 20 is a meniscus lens element, the third lens element 30 is a biconvex lens element, the fifth lens element 50 is a biconcave lens element, and the sixth lens element 60 is a biconvex lens element.

It is understood that, in implementation, the shape of the specific lens can be selected according to the design of the optical power, and the above is only a specific example and is not a limitation to the embodiment of the present invention.

Alternatively, the first lens 10 is tightly fitted with the second lens 20 by a soma, and the fifth lens 50 is tightly fitted with the sixth lens 60 by a soma. Optionally, the second lens 20 and the third lens 30 are tightly fitted through a spacer, the third lens 30 and the fourth lens 40 are tightly fitted through a spacer, and the fourth lens 40 and the fifth lens 50 are tightly fitted through a spacer.

It will be appreciated that the soma is a thin, edge-opaque spacer, and in this embodiment, the distance between the edges of the first lens 10 and the second lens 20 and the distance between the edges of the fifth lens 50 and the sixth lens 60 are relatively close, so that the soma is adopted for tight fitting, the distance between the edges of the other lenses is relatively large, and the distance between the edges of the other lenses is adopted for tight fitting, wherein the spacer can be a plastic spacer, so as to fix the relative positions of the lenses and improve the stability of the fixed focus lens.

Table 2 shows the parameter design values of the specific embodiment of the fixed-focus lens provided in the embodiment of the present invention:

TABLE 2 design values for lenses in a refractive lens group

Number of noodles	Surface type	R(mm)	D(mm)	nd	k
						1	Aspherical surface	45.62	0.95	1.65	-1.23
2	Aspherical surface	3.05	2.23		0.28
						3	Aspherical surface	-3.12	1.60	1.72	2.36
4	Aspherical surface	-5.12	0.05		4.13
						5	Aspherical surface	7.65	2.50	1.65	-12.56
6	Aspherical surface	-13.56	3.05		1.33
						Diaphragm surface	Plane surface	PL	0.25
8	Spherical surface	8.63	3.16	1.55
						9	Spherical surface	-8.63	0.30
10	Aspherical surface	-42.05	0.92	1.65	103.10
						11	Aspherical surface	4.66	0.10		-52.60
12	Aspherical surface	4.73	2.56	1.53	112.70
						13	Aspherical surface	-31.65	4.73		-13.20
15	Spherical surface	Plane surface	0.70	1.52
						16	Spherical surface	Plane surface	1.10

Wherein, the surface number 1 indicates the front surface of the first lens 10 close to the object, and so on, PL indicates that the surface is a plane, and the surface numbers 15 and 16 indicate two surfaces of the lens protective glass; r represents the radius of the spherical surface, positive represents the side of the center of the spherical surface close to the image surface, and negative represents the side of the center of the spherical surface close to the object surface; d represents the distance on the optical axis from the current surface to the next surface; nd represents a refractive index of the lens; k denotes the conic coefficient of the aspheric surface.

Optionally, the surface shape of the plastic aspheric lens satisfies the formula:

wherein z represents a rise in a distance from a vertex of the aspherical surface when the aspherical surface is at a position having a height y in the optical axis direction,

r represents a curvature radius of the face center, k represents a conic coefficient, and A, B, C, D, E, F represents a high-order aspherical coefficient.

Table 3 shows the even coefficients for various aspheric surfaces of the above examples:

TABLE 3 aspheric parameters

Number of noodles

A

B

C

D

E

F

1

-1.25614E-03

-1.95622E-05

3.75634E-06

-1.40156E-07

2.27430E-09

0

2

-2.02352E-01

1.12691E-06

5.31227E-06

1.98210E-06

3.21635E-09

0

3

6.67469E-01

-5.00693E-03

-9.49971E-05

1.18155E-07

-2.91604E-07

0

4

-3.97995E-03

-1.33104E-04

4.88324E-06

5.18010E-07

2.95659E-08

0

5

-1.40156E-02

-1.73041E-06

1.38243E-06

-6.09372E-09

7.51699E-05

0

6

-6.00832E-03

1.41786E-04

-4.53997E-04

1.32201E-05

-3.49924E-07

0

10

-3.35853E-03

4.08395E-04

-3.13451E-04

1.21470E-05

-3.46001E-07

0

11

2.97932E-03

-4.70156E-05

-6.49300E-05

8.20797E-06

-2.48457E-07

0

12

-4.01382E-04

3.54836E-05

-5.17497E-06

3.79343E-07

-4.20965E-09

0

13

-2.03759E-03

1.90309E-04

-8.52281E-05

1.50984E-05

-9.44239E-07

0

Wherein, the numbers 1, 3, 5, 10, 12 correspond to the front surfaces of the first lens 10, the second lens 20, the third lens 30, the fifth lens 50, and the sixth lens 60 close to the object plane, respectively, and the numbers 2, 4, 6, 11, 13 correspond to the rear surfaces of the first lens 10, the second lens 20, the third lens 30, the fifth lens 50, and the sixth lens 60 close to the image plane, respectively, -1.25614E-03 represents-1.25614 × 10^-3。

The prime lens provided by the embodiment can achieve the resolution of 4K pixels in visible light and infrared states, can be matched with a 4K 1/2.5 inch imaging chip, and can obtain a clear picture even in a low-illumination environment at night. Meanwhile, the design does not run coke when used in an environment of-40 ℃ to 80 ℃.

Specifically, fig. 2 shows the modulation transfer function MTF curve diagram of the visible light provided by the embodiment of the present invention, and fig. 3 shows the MTF curve diagram of the infrared light provided by the embodiment of the present invention. The MTF curve shown in fig. 2 is obtained under the condition that the visible light wavelength is 436nm to 656nm, the MTF curve shown in fig. 3 is obtained under the condition that the infrared light wavelength is 850nm, and when the spatial resolution is 230 line pairs/mm to achieve the 4K pixel resolution, the MTF of the visible light of the central view field is greater than 0.4, and the MTF of the infrared light of the central view field is greater than 0.2. Referring to fig. 2 and 3, it can be seen that the condition of 4K resolution is satisfied for both visible light and infrared light.

It should be noted that the foregoing is only a preferred embodiment of the present invention and the technical principles applied. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail with reference to the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the scope of the present invention.

Claims (10)

1. A fixed focus lens is characterized by comprising a first lens with negative focal power, a second lens with negative focal power, a third lens with positive focal power, a fourth lens with positive focal power, a fifth lens with negative focal power and a sixth lens with positive focal power, which are sequentially arranged from an object side to an image side along an optical axis;

wherein the fourth lens is a glass spherical lens;

the first lens, the second lens, the third lens, the fifth lens and the sixth lens are all plastic aspheric lenses.

2. The prime lens according to claim 1, wherein the focal lengths of the third and fourth lenses and the focal length of the prime lens satisfy the following relationship:

1.8<︱f3/f︱<2.1；

1.8<︱f4/f︱<2.1；

wherein f3, f4, and f denote focal lengths of the third lens, the fourth lens, and the prime lens, respectively.

3. The prime lens according to claim 1, wherein the first to sixth lenses satisfy the following parameters:

f1＝-5.3～-6.5 n1＝1.48～1.68 R1＝43～56 R2＝2.05～3.15 f2＝-28～-32.5 n2＝1.55～1.75 R3＝-3.05～-4.45 R4＝-3.8～-5.2 f3＝8.1～9.6 n3＝1.48～1.68 R5＝6.8～7.9 R6＝-12.5～-14.5 f4＝8.1～9.6 n4＝1.48～1.68 R7＝7.3～8.8 R8＝-7.3～-8.8 f5＝-5.8～-6.8 n5＝1.56～1.76 R9＝-41～-48 R10＝4.5～5.6 f6＝6.8～7.5 n6＝1.48～1.68 R11＝4.1～4.8 R12＝-26.5～-30.8

wherein f1 to f6 represent focal lengths of the first lens to the sixth lens in mm, n1 to n6 represent refractive indices of the first lens to the sixth lens, R1, R3, R5, R7, R9, and R11 represent radii of curvature of the first lens to the sixth lens toward the center of the object side surface in this order, R2, R4, R6, R8, R10, and R12 represent radii of curvature of the first lens to the sixth lens toward the center of the image side surface in this order, respectively, in mm, and "-" represents a negative direction.

4. The prime lens according to claim 1, further comprising a diaphragm disposed between the third lens and the fourth lens.

5. The prime lens according to claim 1, wherein the fourth lens is a biconvex lens.

6. The prime lens according to claim 5, wherein the first lens is a meniscus lens, the second lens is a meniscus lens, the third lens is a biconvex lens, the fifth lens is a biconcave lens, and the sixth lens is a biconvex lens.

7. The fixed focus lens as claimed in claim 6, wherein said first lens is tightly fitted with said second lens by a soma and said fifth lens is tightly fitted with said sixth lens by a soma.

8. The fixed focus lens as claimed in claim 6, wherein the second lens is tightly fitted with the third lens through a spacer, the third lens is tightly fitted with the fourth lens through a spacer, and the fourth lens is tightly fitted with the fifth lens through a spacer.

9. The prime lens according to claim 1, wherein the surface shape of the plastic aspherical lens satisfies the formula:

wherein z represents a rise in a distance from a vertex of the aspherical surface when the aspherical surface is at a position having a height y in the optical axis direction,

r represents a curvature radius of the face center, k represents a conic coefficient, and A, B, C, D, E, F represents a high-order aspherical coefficient.

10. The prime lens according to claim 1, wherein an aperture F of the prime lens is greater than or equal to 1.8.

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