CN213581568U

CN213581568U - Fixed focus lens

Info

Publication number: CN213581568U
Application number: CN202022796803.6U
Authority: CN
Inventors: 马育国; 何剑炜; 漆燕梅
Original assignee: Dongguan Yutong Optical Technology Co Ltd
Current assignee: Dongguan Yutong Optical Technology Co Ltd
Priority date: 2020-11-27
Filing date: 2020-11-27
Publication date: 2021-06-29
Anticipated expiration: 2030-11-27

Abstract

The utility model discloses a tight shot, include: the lens comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged from an object side to an image side along an optical axis; the first lens has a negative optical power, the second lens has a positive optical power, the third lens has a positive optical power, and the fourth lens has a negative optical power; the focal length of the fixed-focus lens is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, and the focal length of the fourth lens is f 4; wherein 1.0< | f1/f | < 4.0; 1.0< | f2/f | < 4.0; 1.0< | f3/f | < 4.0; 1.0< | f4/f | < 4.0. The utility model provides a fixed focus camera lens has the characteristics of big angle of vision, little volume and little purple boundary, and is confocal day and night moreover, and the front end need not increase protective glass when using, can reduce cost when improving environmental suitability, also avoids the camera to increase ghost and parasitic light that protective glass brought.

Description

Fixed focus lens

Technical Field

The utility model relates to an optical device technical field especially relates to a tight shot.

Background

With the rise of safety awareness of people and the increasing popularization of security monitoring facilities, the requirements on monitoring environment and pictures are higher and higher, but the cost requirements on the security monitoring facilities are more and more strict, and the security lens is also developed towards a large field angle. The fixed focus lens has the characteristics of short focal length, long depth of field and large field angle, and under the same condition, the larger the field angle is, the larger the amount of information which can be acquired is. The existing prime lens adopts a structure of 5-7 lenses, most of the first lenses are plastic aspheric surfaces, the existing prime lens has the defects of large volume and high cost, the environmental damage resistance is poor, and protective glass is required to be added at the front end of the lens to avoid the damage of the plastic lenses. In addition, the existing fixed focus lens still has the defects of dead angles, poor definition and the like, especially when the field angle exceeds 120 degrees, the distortion is too large, the image after imaging is seriously deformed, and the monitoring effect is influenced.

SUMMERY OF THE UTILITY MODEL

The embodiment of the utility model provides a fixed focus camera lens has the characteristics of big angle of vision, little volume and little purple boundary, and is confocal day and night moreover, and the front end need not increase protective glass when using, can reduce cost when improving environmental suitability, also avoids the camera to increase ghost and veiling glare that protective glass brought.

The embodiment of the utility model provides a fixed focus lens, including first lens, second lens, third lens and the fourth lens that arrange from the object space to the image space along the optical axis in proper order;

the first lens has a negative optical power, the second lens has a positive optical power, the third lens has a positive optical power, and the fourth lens has a negative optical power;

the focal length of the fixed-focus lens is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, and the focal length of the fourth lens is f 4;

wherein 1.0< | f1/f | < 4.0;

1.0<|f2/f|<4.0；

1.0<|f3/f|<4.0；

1.0<|f4/f|<4.0。

optionally, the first lens and the second lens are glass spherical lenses, and the third lens and the fourth lens are plastic aspheric lenses.

Optionally, the surface of the lens close to the object side is an object side surface, and the surface close to the image side is an image side surface;

the object side surface of the first lens is a concave surface, and the image side surface of the first lens is a concave surface;

the object side surface of the second lens is a convex surface, and the image side surface of the second lens is a convex surface;

the object side surface of the third lens is a convex surface, and the image side surface of the third lens is a convex surface;

the object side surface of the fourth lens is a concave surface, and the image side surface of the fourth lens is a convex surface.

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;

Optionally, the fixed-focus lens further includes a diaphragm;

the diaphragm is located in an optical path between the first lens and the second lens.

Optionally, the field angle of the fixed focus lens is FOV, wherein the FOV is greater than or equal to 120 °.

Optionally, the F-number of the fixed focus lens is F, wherein F is greater than or equal to 2.0 and less than or equal to 3.0.

The utility model provides a fixed focus lens, which comprises a first lens, a second lens, a third lens and a fourth lens which are arranged in sequence from an object space to an image space along an optical axis; the first lens has negative focal power, the second lens has positive focal power, the third lens has positive focal power, and the fourth lens has negative focal power; the focal length of the fixed-focus lens is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, and the focal length of the fourth lens is f 4; wherein 1.0< | f1/f | < 4.0; 1.0< | f2/f | < 4.0; 1.0< | f3/f | < 4.0; 1.0< | f4/f | < 4.0. The embodiment of the utility model provides a tight shot through the focal power and the focus of reasonable each lens that set up, can realize guaranteeing little purple boundary under the condition of big angle of vision, reduced the quantity that uses lens simultaneously, reduced manufacturing cost, it is confocal day and night moreover, the camera lens is complementary with the base inflation under the environment of 40 ℃ - +80 ℃, realizes that imaging quality all satisfies the standard under each temperature.

Drawings

Fig. 1 is a schematic structural diagram of a fixed focus lens according to a first embodiment of the present invention;

fig. 2 is an axial aberration curve of the fixed-focus lens shown in fig. 1 according to an embodiment of the present invention;

fig. 3 is a field curvature curve of the fixed focus lens shown in fig. 1 according to an embodiment of the present invention;

fig. 4 is a distortion curve of the fixed-focus lens shown in fig. 1 according to an embodiment of the present invention;

fig. 5 is a chromatic aberration curve of the fixed-focus lens shown in fig. 1 according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of a fixed-focus lens provided in the second embodiment of the present invention;

fig. 7 is an axial aberration curve of the fixed-focus lens shown in fig. 6 according to the second embodiment of the present invention;

fig. 8 is a field curvature curve of the fixed-focus lens shown in fig. 6 according to the second embodiment of the present invention;

fig. 9 is a distortion curve of the fixed-focus lens shown in fig. 6 according to the second embodiment of the present invention;

fig. 10 is a chromatic aberration curve of the fixed-focus lens shown in fig. 6 according to the second 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.

Example one

Fig. 1 is a schematic structural diagram of a fixed focus lens according to a first embodiment of the present invention, as shown in fig. 1, a fixed focus lens 10 according to a first embodiment of the present invention includes a first lens 100, a second lens 200, a third lens 300, and a fourth lens 400 arranged in sequence from an object side to an image side along an optical axis AA'; the first lens 100 has a negative power, the second lens 200 has a positive power, the third lens 300 has a positive power, and the fourth lens 400 has a negative power; the focal length of the fixed-focus lens is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, and the focal length of the fourth lens is f 4; wherein 1.0< | f1/f | < 4.0; 1.0< | f2/f | < 4.0; 1.0< | f3/f | < 4.0; 1.0< | f4/f | < 4.0.

Wherein, the focal power is equal to the difference between the convergence of the image side light beam and the convergence of the object side light beam, which characterizes the capability of the optical system to deflect the 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 fixed focus lens provided in this embodiment, each lens may be fixed in a lens barrel (not shown in fig. 1), the first lens 100 is a negative power lens for controlling the incident angle of the optical system and correcting curvature of field, the second lens 200 and the third lens 300 are positive power lenses for focusing light beams, the fourth lens 400 is a negative power lens for correcting off-axis aberrations including curvature of field, coma aberration, astigmatism, and the like, and the power of the whole fixed focus lens is distributed according to a certain proportion, so that the balance of the incident angle of the front and rear lenses is ensured, the sensitivity of the lenses is reduced, and the production stability is improved. In this embodiment, by reasonably configuring the focal power of each lens, a small purple fringe can be ensured under the condition of a large field angle, the number of lenses used is reduced, and the production cost of the fixed-focus lens 10 is reduced.

The focal length is a measure for measuring the degree of light collection or divergence in an optical system, and specifically refers to the distance from the optical center of the lens to the focal point of light collection when parallel light is incident. In the first embodiment, the focal length ratio of each lens and the fixed-focus lens 10 is optimally configured, so that chromatic aberration of the fixed-focus lens 10 is effectively corrected, and the problem of focus drift of the fixed-focus lens 10 due to the ambient temperature is solved, so that the fixed-focus lens 10 has a temperature compensation function, performs confocal in day and night, ensures that the lens and the base expand and complement in an environment of-40 ℃ to +80 ℃, and realizes that the imaging quality at each temperature meets the standard. By reasonably distributing the focal lengths of the lenses, the spherical aberration and the field curvature of the imaging system are small at the same time, and the image quality of the on-axis and off-axis view fields is ensured. Through the optical system formed by the lenses, the total length of the light path is short, so that the overall size of the lens is small.

Alternatively, the first lens 100 and the second lens 200 may be glass spherical lenses, and the third lens 300 and the fourth lens 400 may be plastic aspherical lenses. The aspheric lens has the function of correcting aberrations such as field curvature, astigmatism, spherical aberration, coma aberration and the like. The material of glass lens is various types of glass that the technical staff in this field can know, and the material of plastic lens can be various plastics that the technical staff in this field can know, the embodiment of the utility model is to this no longer give unnecessary details nor do the restriction. The lens cost of plastics material is far less than the lens cost of glass material, the embodiment of the utility model provides an in the tight shot 10, adopted the mode of glass lens and plastic lens combination, the front end need not increase protective glass when using, reduces the manufacturing cost of tight shot 10 when improving environmental suitability, also avoids camera to increase ghost and parasitic light that protective glass brought.

Optionally, with continued reference to fig. 1, a surface of the lens close to the object side is an object side surface, and a surface close to the image side is an image side surface; the object-side surface of the first lens element 100 is concave, and the image-side surface of the first lens element 100 is concave; the object-side surface of the second lens element 200 is convex, and the image-side surface of the second lens element 200 is convex; the object-side surface of the third lens element 300 is convex, and the image-side surface of the third lens element 300 is convex; the object-side surface of the fourth lens element 400 is concave, and the image-side surface of the fourth lens element 400 is convex. Through the reasonable setting of the surface type of each lens, the focal power and the focal length of each lens can meet the focal power and the focal length requirement in the above embodiment, and meanwhile, the whole fixed-focus lens 10 can be ensured to be compact in structure, and the integration level of the fixed-focus lens 10 is high.

Optionally, as shown in fig. 1, the fixed focus lens 10 may further include a diaphragm 500; the stop 500 is located in the optical path between the first lens 100 and the second lens 200. By arranging the diaphragm 500 in the optical path between the first lens 100 and the second lens 200, the propagation direction of the light beam can be adjusted, and the incident angle of the light beam can be adjusted, which is beneficial to further improving the imaging quality.

Optionally, the field angle of the fixed focus lens 10 may be FOV, where FOV is greater than or equal to 120 °. The embodiment of the present invention provides a fixed focus lens 10, which is a large field angle fixed focus lens and satisfies the requirement of large field.

Optionally, the F-number of the fixed focus lens 10 may be F, where F is greater than or equal to 2.0 and less than or equal to 3.0. The embodiment of the utility model provides a tight shot 10 is a big light ring tight shot, satisfies super large throughput requirement.

As a possible embodiment, the design values of the respective lenses of the fixed focus lens 10 in the first embodiment are described below as shown in table 1.

Table 1 shows design values (F3.56 mm; F2.0) of each lens of the fixed focus lens 10 in the first embodiment

Number of noodles	Radius of curvature	Thickness of	Value of K	Refractive index	Abbe number
						S1	102.45	1.00		1.62	60.37
S2	2.99	6.11
						STO	PL	0.05
S4	8.53	3.83		1.55	63.37
						S5	-6.64	0.93
S6	5.30	2.44	-45.39	1.54	55.71
						S7	-2.55	0.12	-0.38
S8	-1.68	0.75	-4.80	1.64	23.50
						S9	-5.04	0.30	-62.23
S10	PL	0.70		1.52	64.21
						S11	PL	4.32

The surface numbers in table 1 are numbered according to the surface order of the respective lenses, wherein "S1" represents the front surface of the first lens 100, "S2" represents the rear surface of the first lens 100, and so on; "STO" represents the diaphragm 500 of the fixed focus lens 10; the curvature radius represents the bending degree of the lens surface, a positive value represents that the surface is bent to the image surface side, a negative value represents that the surface is bent to the object surface side, wherein 'PL' represents that the surface is a plane, and the curvature radius is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the deflection capability of the material between the current surface and the next surface to light, the blank space represents that the current position is air, and the refractive index is 1; the abbe number represents the dispersion characteristic of the material between the current surface and the next surface to light, and the blank space represents that the current position is air; the K value represents the magnitude of the best fitting conic coefficient for the aspheric surface.

The aspheric conic coefficients can be defined by the following aspheric equation, but are not limited to the following representation:

wherein Z is the axial rise of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitting sphere, and the numerical value is the reciprocal of the curvature radius; k is a fitting cone coefficient; A-F are coefficients of 4 th, 6 th, 8 th, 10 th, 12 th and 14 th order terms of the aspheric polynomial.

The aspherical surface type parameters of the fixed focus lens 10 in the first embodiment are shown in table 2.

Table 2 shows aspheric surface parameters of the fixed focus lens 10 in the first embodiment

Fig. 2 is an axial aberration curve of the fixed-focus lens shown in fig. 1 according to an embodiment of the present invention; fig. 3 is a field curvature curve of the fixed focus lens shown in fig. 1 according to an embodiment of the present invention; fig. 4 is a distortion curve of the fixed-focus lens shown in fig. 1 according to an embodiment of the present invention; fig. 5 is a chromatic aberration curve of the fixed-focus lens shown in fig. 1 according to an embodiment of the present invention. As can be seen from fig. 2, the axial aberrations of the fixed-focus lens are small for the light rays with different wavelengths (0.486 μm, 0.588 μm and 0.656 μm), and the aberrations can be corrected well; as can be seen from FIG. 3, the field curvature in the meridional direction and the sagittal direction of the light rays of the fixed-focus lens pair with different wavelengths (0.486 μm, 0.588 μm and 0.656 μm) is within + -0.20 mm; as can be seen from fig. 4, the fixed focus lens is effectively controlled in curvature of field, that is, when imaging, the difference between the central image quality and the peripheral image quality is small, and the distortion of the fixed focus lens is better corrected, the imaging distortion is small, and the requirement of low distortion is met; as can be seen from fig. 5, the plastic aspheric lens is used to effectively reduce the lateral chromatic aberration of the longer wavelength spectrum, and is beneficial to eliminating the purple-edge phenomenon during the use of the lens, so that the clear imaging can be realized in the night environment.

The embodiment of the utility model provides a tight shot through the focal power and the focus of reasonable each lens that set up, can realize guaranteeing little purple boundary under the condition of big angle of vision, reduced the quantity that uses lens simultaneously, reduced manufacturing cost, it is confocal day and night moreover, the definition can both accord with the standard under the environment of-40 ℃ - +80 ℃.

Example two

Fig. 6 is a schematic structural diagram of a fixed focus lens according to a second embodiment of the present invention, and as shown in fig. 6, a fixed focus lens 10 according to a second embodiment of the present invention includes a first lens 100, a second lens 200, a third lens 300, and a fourth lens 400 sequentially arranged from an object side to an image side along an optical axis AA'; the first lens 100 has a negative power, the second lens 200 has a positive power, the third lens 300 has a positive power, and the fourth lens 400 has a negative power; the focal length of the fixed-focus lens is f, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, and the focal length of the fourth lens is f 4; wherein 1.0< | f1/f | < 4.0; 1.0< | f2/f | < 4.0; 1.0< | f3/f | < 4.0; 1.0< | f4/f | < 4.0.

In the fixed focus lens provided in this embodiment, each lens may be fixed in a lens barrel (not shown in fig. 1), the first lens 100 is a negative power lens for controlling the incident angle of the optical system and correcting curvature of field, the second lens 200 and the third lens 300 are positive power lenses for focusing light beams, the fourth lens 400 is a negative power lens for correcting off-axis aberrations including curvature of field, coma aberration, astigmatism, and the like, and the power of the whole fixed focus lens is distributed according to a certain proportion, so that the balance of the incident angle of the front and rear lenses is ensured, the sensitivity of the lenses is reduced, and the production stability is improved. In this embodiment, by reasonably configuring the focal power of each lens, a small purple fringe can be ensured under the condition of a large field angle, the number of lenses used is reduced, and the production cost of the fixed-focus lens 10 is reduced. In the embodiment, the focal length ratio of each lens and the fixed-focus lens 10 is optimally configured, so that the chromatic aberration of the fixed-focus lens 10 is effectively corrected, the problem of focus drift of the fixed-focus lens 10 due to the environmental temperature is solved, the fixed-focus lens 10 has a temperature compensation function, and is confocal day and night, thereby ensuring that the lens and the base are expanded and complemented under the environment of-40 ℃ to +80 ℃, and realizing that the imaging quality at each temperature meets the standard. By reasonably distributing the focal lengths of the lenses, the spherical aberration and the field curvature of the imaging system are small at the same time, and the image quality of the on-axis and off-axis view fields is ensured. Through the optical system formed by the lenses, the total length of the light path is short, so that the overall size of the lens is small.

Optionally, with continued reference to fig. 6, a surface of the lens close to the object side is an object side surface, and a surface close to the image side is an image side surface; the object-side surface of the first lens element 100 is convex, and the image-side surface of the first lens element 100 is concave; the object-side surface of the second lens element 200 is convex, and the image-side surface of the second lens element 200 is convex; the object-side surface of the third lens element 300 is convex, and the image-side surface of the third lens element 300 is convex; the object-side surface of the fourth lens element 400 is concave, and the image-side surface of the fourth lens element 400 is convex. Through the reasonable setting of the surface type of each lens, the focal power and the focal length of each lens can meet the focal power and the focal length requirement in the above embodiment, and meanwhile, the whole fixed-focus lens 10 can be ensured to be compact in structure, and the integration level of the fixed-focus lens 10 is high.

The focal power, focal length, surface shape, material, field angle, f-number and diaphragm position of each lens are the same as those in the first embodiment, and are not described herein again.

As one possible embodiment, the following describes design values of the respective lenses of the fixed focus lens 10 in the second embodiment, as shown in table 3.

Table 3 design values (F3.25 mm; F2.0) of the respective lenses of the fixed focus lens 10 in the second embodiment:

The surface numbers in table 3 are numbered according to the surface order of the respective lenses, wherein "S1" represents the front surface of the first lens 100, "S2" represents the rear surface of the first lens 100, and so on; "STO" represents the diaphragm 500 of the fixed focus lens 10; the curvature radius represents the bending degree of the lens surface, a positive value represents that the surface is bent to the image surface side, a negative value represents that the surface is bent to the object surface side, wherein 'PL' represents that the surface is a plane, and the curvature radius is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the deflection capability of the material between the current surface and the next surface to light, the blank space represents that the current position is air, and the refractive index is 1; the abbe number represents the dispersion characteristic of the material between the current surface and the next surface to light, and the blank space represents that the current position is air; the K value represents the magnitude of the best fitting conic coefficient for the aspheric surface.

The aspherical surface type parameters of the fixed focus lens 10 in the second embodiment are shown in table 4.

Table 4 shows aspheric surface parameters of the fixed focus lens 10 in the second embodiment

Fig. 7 is an axial aberration curve of the fixed-focus lens shown in fig. 6 according to the second embodiment of the present invention; fig. 8 is a field curvature curve of the fixed-focus lens shown in fig. 6 according to the second embodiment of the present invention; fig. 9 is a distortion curve of the fixed-focus lens shown in fig. 6 according to the second embodiment of the present invention; fig. 10 is a chromatic aberration curve of the fixed-focus lens shown in fig. 6 according to the second embodiment of the present invention. As can be seen from fig. 7, the axial aberrations of the fixed-focus lenses are small for the different wavelengths of light (0.486 μm, 0.588 μm and 0.656 μm), and the aberrations can be corrected well; as can be seen from fig. 8, the field curvature in the meridional direction and the sagittal direction of the light rays of the fixed-focus lens pair with different wavelengths (0.486 μm, 0.588 μm and 0.656 μm) is within ± 0.20 mm; as can be seen from fig. 9, the fixed focus lens is effectively controlled in curvature of field, that is, when imaging, the difference between the central image quality and the peripheral image quality is small, and the distortion of the fixed focus lens is better corrected, the imaging distortion is small, and the requirement of low distortion is met; as can be seen from fig. 10, the plastic aspheric lens is used to effectively reduce the lateral chromatic aberration of the longer wavelength spectrum, and is beneficial to eliminating the purple-edge phenomenon during the use of the lens, so as to realize clear imaging even in the night environment.

The embodiment of the utility model provides a tight shot through the focal power and the focus of reasonable each lens that set up, can realize guaranteeing little purple boundary under the condition of big angle of vision, reduced the quantity that uses lens simultaneously, reduced manufacturing cost, it is confocal day and night moreover, the camera lens is complementary with the base inflation under the environment of 40 ℃ - +80 ℃, realizes that imaging quality all satisfies the standard under each temperature.

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

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

wherein 1.0< | f1/f | < 4.0;

1.0<|f2/f|<4.0；

1.0<|f3/f|<4.0；

1.0<|f4/f|<4.0。

2. the prime lens according to claim 1, wherein the first lens and the second lens are glass spherical lenses, and the third lens and the fourth lens are plastic aspherical lenses.

3. The prime lens according to claim 1, wherein the surface of the lens close to the object side is an object side surface, and the surface close to the image side is an image side surface;

4. The prime lens according to claim 1, wherein the surface of the lens close to the object side is an object side surface, and the surface close to the image side is an image side surface;

5. The prime lens according to claim 1, further comprising a diaphragm;

6. The prime lens according to claim 1, wherein the field angle of the prime lens is FOV, wherein FOV is greater than or equal to 120 °.

7. The prime lens according to claim 1, wherein the F-number of the prime lens is F, wherein F is greater than or equal to 2.0 and less than or equal to 3.0.