CN215575895U - Fixed focus lens - Google Patents

Fixed focus lens Download PDF

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CN215575895U
CN215575895U CN202121101439.5U CN202121101439U CN215575895U CN 215575895 U CN215575895 U CN 215575895U CN 202121101439 U CN202121101439 U CN 202121101439U CN 215575895 U CN215575895 U CN 215575895U
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lens
equal
prime
less
satisfy
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张圆
陶雪
梁伟朝
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Sunny Optics Zhongshan Co Ltd
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Sunny Optics Zhongshan Co Ltd
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Abstract

The utility model relates to a fixed focus lens, which comprises a first lens (L1) with negative focal power, a second lens (L2) with negative focal power, a third lens (L3) with positive focal power, a fourth lens (L4) with negative focal power, a fifth lens (L5) with positive focal power, a sixth lens (L6) with positive focal power, a seventh lens (L7) with negative focal power and an eighth lens (L8) with positive focal power, wherein the first lens (L1) is a biconcave aspheric lens. The fixed-focus lens can realize large aperture, ensure higher pixels, larger image height and small volume, does not have virtual focus within the temperature range of minus 40-80 ℃, does not need infrared rays, and can be used for day and night.

Description

Fixed focus lens
Technical Field
The utility model relates to the technical field of optical imaging, in particular to a fixed-focus lens with a large aperture.
Background
With the development of scientific technology and the increasing popularization of security monitoring facilities, the fixed focus lens is widely applied to various fields due to the advantages of high imaging definition, wide monitoring visual field, clear imaging under low illumination and the like. Because at night or in the environment that the illumination condition is not enough, the security protection monitoring lens shoots the image luminance not enough, can't clear formation of image. Therefore, in the prior art, an infrared light supplement mode is usually adopted to achieve the purpose of imaging. However, the infrared imaging range is small, and real color information cannot be shot, so that color distortion is serious, and therefore, in the environment with insufficient illumination conditions or at night, the technical problem needing to be solved in the field of security monitoring is to ensure that a lens can clearly image.
SUMMERY OF THE UTILITY MODEL
The utility model aims to provide a fixed-focus lens.
In order to achieve the above object, the present invention provides a fixed focus lens, including a first lens having a negative refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, a fourth lens having a negative refractive power, a fifth lens having a positive refractive power, a sixth lens having a positive refractive power, a seventh lens having a negative refractive power, and an eighth lens having a positive refractive power, which are arranged in order from an object side to an image side along an optical axis, wherein the first lens is a biconcave aspheric lens.
According to an aspect of the present invention, the second lens is a concave-convex aspheric lens, the third lens is a concave-convex aspheric lens, the fourth lens is a concave-convex spherical lens, the fifth lens is a biconvex spherical lens, the sixth lens is a biconvex aspheric lens, the seventh lens is a biconcave aspheric lens, and the eighth lens is a biconvex aspheric lens.
According to one aspect of the utility model, the fourth lens and the fifth lens are cemented to form a cemented lens group with positive optical power.
According to an aspect of the utility model, further comprising a diaphragm, the diaphragm being located between the second lens and the third lens or between the third lens and the fourth lens.
According to an aspect of the present invention, the first lens, the second lens, the third lens, the sixth lens, the seventh lens, and the eighth lens are plastic lenses.
According to one aspect of the utility model, the zoom lens further comprises a flat glass positioned on the image side of the eighth lens.
According to an aspect of the present invention, an effective focal length f of the prime lens and an image-side radius L1R2 of the first lens satisfy the following relationship: L1R2/f is more than or equal to 1.05 and less than or equal to 1.15.
According to an aspect of the present invention, an effective focal length f of the prime lens and an effective focal length f1 of the first lens satisfy the following relationship: f1/f is more than or equal to-2 and less than or equal to-1.8.
According to an aspect of the present invention, the total angle of incidence θ 2 of the second lens and the maximum field angle FOV of the fixed-focus lens satisfy the following relationship: theta 2/FOV is less than or equal to 0.9;
the maximum field angle FOV, the effective focal length f and the maximum full image height H of the fixed-focus lens meet the following relations: 60 is less than or equal to (FOV x f)/H.
According to one aspect of the utility model, the total angle of incidence θ 4 of the fourth lens and the total angle of incidence θ 5 of the fifth lens satisfy the following relationship: theta 4/theta 5 is less than or equal to 2.
According to an aspect of the present invention, a combined focal length fb of the fourth lens and the fifth lens and an effective focal length f of the prime lens satisfy the following relationship: fb/f is more than or equal to 2.0 and less than or equal to 3.0.
According to one aspect of the utility model, the Fno number of the fixed-focus lens satisfies the following condition: fno is less than or equal to 1.2.
According to one aspect of the utility model, the Fno number and the effective focal length f of the fixed-focus lens satisfy the following relation: fno/f is more than or equal to 0.1.
According to an aspect of the present invention, an effective focal length f of the prime lens and an effective focal length f4 of the fourth lens satisfy the following relationship: f4/f is not less than-3.8 and not more than-2.5.
According to one aspect of the utility model, the effective focal length f and the half-image height h of the fixed-focus lens satisfy the following relation: f/h is more than or equal to 0.9 and less than or equal to 1.1.
According to one aspect of the present invention, the effective focal length f and the total length TTL of the fixed-focus lens satisfy the following relationship: f/TTL is more than or equal to 0.1 and less than or equal to 0.2.
According to one aspect of the present invention, the total length TTL, the maximum full image height H, and the maximum field angle FOV of the fixed focus lens satisfy the following relationships: TTL/H/FOV is less than or equal to 0.1.
According to an aspect of the present invention, the first lens object side maximum clear half aperture D and the maximum full image height H and the maximum field angle FOV of the fixed focus lens satisfy the following relationships: D/H/FOV is less than or equal to 0.1.
According to an aspect of the present invention, a temperature coefficient of relative refractive index dn/dt of at least one of the fourth lens and the fifth lens satisfies the following condition: dn/dt is less than or equal to 4 x 10-6/℃。
According to an aspect of the present invention, an air interval T23 between the second lens and the third lens and a total length TTL of the fixed focus lens satisfy the following relationship: T23/TTL is less than or equal to 0.1.
According to the utility model, the glass-plastic mixed day and night wide-angle prime lens can realize large aperture, ensure higher pixels, larger image height and small volume, does not have virtual focus in the temperature range of-40-80 ℃ and does not need infrared rays.
According to the scheme of the utility model, through reasonably setting the positive and negative focal powers, the concavity and the convexity of each lens in the fixed-focus lens, the relationship between the effective focal length of the lens and the effective focal length and R2 of the first lens, the relationship between the incident full angle of the second lens and the maximum field angle of the lens, and the relationship between the maximum field angle, the effective focal length and the maximum total image height of the lens, the first lens can play a role in collecting light, the trend of light rays is gentle, and the realization of larger image height is facilitated.
According to the scheme of the utility model, the fourth lens and the fifth lens form the double-cemented lens group, and the incident full-angle relation of the fourth lens and the fifth lens and the relation between the combined focal length and the effective focal length of the lens are reasonably set, so that the chromatic aberration of the optical system can be corrected, and the realization of higher image quality is facilitated.
According to the scheme of the utility model, the aspheric lenses in the fixed-focus lens are all plastic lenses, so that the cost is reduced, and high-temperature and low-temperature imaging is corrected.
According to the scheme of the utility model, the relationship among the lens Fno number, the lens effective focal length, the relationship among the lens effective focal length, the first lens effective focal length, the half image height and the total length, the relationship among the lens total length, the maximum full image height and the maximum field angle, and the relationship among the maximum aperture of the object side of the first lens, the maximum full image height and the maximum field angle are reasonably set, so that the higher image quality is realized, and the smaller volume of the lens is ensured.
According to the scheme of the utility model, the temperature coefficient of the relative refractive index of at least one of the fourth lens and the fifth lens is smaller than a certain value, which is beneficial to realizing that the system does not have virtual focus within the temperature range of minus 40 ℃ to 80 ℃.
According to the scheme of the utility model, the air space between the second lens and the third lens is insensitive by reasonably setting the relationship between the air space between the second lens and the third lens and the total length of the lens, thereby being beneficial to the aberration correction of a system and the image quality improvement.
Drawings
Fig. 1 is a schematic diagram showing a construction of a fixed focus lens according to a first embodiment of the present invention;
fig. 2 schematically shows an MTF chart of a fixed-focus lens according to a first embodiment of the present invention;
FIG. 3 is a Through-Focus-MTF plot schematically illustrating a frequency of 125lp/mm for a fixed Focus lens in accordance with a first embodiment of the present invention;
FIG. 4 is a Through-Focus-MTF graph schematically showing a frequency of 125lp/mm at a high temperature of 80 ℃ for a fixed-Focus lens according to a first embodiment of the present invention;
FIG. 5 is a Through-Focus-MTF graph schematically showing a frequency of 125lp/mm at a low temperature of-40 ℃ in a fixed-Focus lens according to a first embodiment of the present invention;
fig. 6 is a schematic diagram showing a construction of a fixed focus lens according to a second embodiment of the present invention;
fig. 7 schematically shows an MTF chart of a fixed-focus lens according to a second embodiment of the present invention;
FIG. 8 is a Through-Focus-MTF plot schematically illustrating a frequency of 125lp/mm for a fixed Focus lens in accordance with a second embodiment of the present invention;
FIG. 9 is a Through-Focus-MTF graph schematically showing a frequency of 125lp/mm at a high temperature of 80 ℃ for a fixed-Focus lens according to a second embodiment of the present invention;
FIG. 10 is a Through-Focus-MTF graph schematically showing a frequency of 125lp/mm at-40 ℃ in a fixed-Focus lens according to a second embodiment of the present invention;
fig. 11 is a schematic diagram showing a construction of a fixed focus lens according to a third embodiment of the present invention;
fig. 12 schematically shows an MTF chart of a fixed-focus lens according to a third embodiment of the present invention;
FIG. 13 is a Through-Focus-MTF plot schematically illustrating a frequency of 125lp/mm for a fixed Focus lens in accordance with a third embodiment of the present invention;
FIG. 14 is a Through-Focus-MTF graph schematically showing a frequency of 125lp/mm at a high temperature of 80 ℃ for a fixed-Focus lens according to a third embodiment of the present invention;
FIG. 15 is a Through-Focus-MTF graph schematically showing a frequency of 125lp/mm at a low temperature of-40 ℃ in a fixed-Focus lens according to a third embodiment of the present invention;
fig. 16 is a schematic diagram showing a construction of a fixed focus lens according to a fourth embodiment of the present invention;
fig. 17 schematically shows an MTF chart of a fixed-focus lens according to a fourth embodiment of the present invention;
FIG. 18 is a Through-Focus-MTF graph schematically showing a frequency of 125lp/mm for a fixed-Focus lens according to a fourth embodiment of the present invention;
FIG. 19 is a Through-Focus-MTF graph schematically showing a frequency of 125lp/mm at a high temperature of 80 ℃ in a fixed-Focus lens according to a fourth embodiment of the present invention;
FIG. 20 is a Through-Focus-MTF graph schematically showing a frequency of 125lp/mm at a low temperature of-40 ℃ in a fixed-Focus lens according to a fourth embodiment of the present invention;
fig. 21 is a schematic view showing a construction of a fixed focus lens according to a fifth embodiment of the present invention;
fig. 22 schematically shows an MTF chart of a fixed-focus lens according to a fifth embodiment of the present invention;
FIG. 23 is a Through-Focus-MTF plot schematically illustrating a frequency of 125lp/mm for a fixed Focus lens according to a fifth embodiment of the present invention;
FIG. 24 is a Through-Focus-MTF graph schematically showing a frequency of 125lp/mm at a high temperature of 80 ℃ for a fixed-Focus lens according to a fifth embodiment of the present invention;
FIG. 25 is a Through-Focus-MTF graph schematically showing a frequency of 125lp/mm at a low temperature of-40 ℃ in a fixed-Focus lens according to a fifth embodiment of the present invention.
Detailed Description
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the utility model, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
In describing embodiments of the present invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship that is based on the orientation or positional relationship shown in the associated drawings, which is for convenience and simplicity of description only, and does not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus, the above-described terms should not be construed as limiting the present invention.
The present invention is described in detail below with reference to the drawings and the specific embodiments, which are not repeated herein, but the embodiments of the present invention are not limited to the following embodiments.
Referring to fig. 1, the fixed focus lens of the present invention includes, in order from an object side to an image side along an optical axis, a first lens L1 having negative power, a second lens L2 having negative power, a third lens L3 having positive power, a fourth lens L4 having negative power, a fifth lens L5 having positive power, a sixth lens L6 having positive power, a seventh lens L7 having negative power, and an eighth lens L8 having positive power. A protective plate glass CG is disposed on the image side of the eighth lens element L8.
In the present invention, the first lens L1 is a biconcave type aspheric lens, the second lens L2 is a concavo-convex type aspheric lens, the third lens L3 is a concavo-convex type aspheric lens, the fourth lens L4 is a concavo-convex type spherical lens, the fifth lens L5 is a biconvex type spherical lens, the sixth lens L6 is a biconvex type aspheric lens, the seventh lens L7 is a biconcave type aspheric lens, and the eighth lens L8 is a biconvex type aspheric lens. The prime lens of the present invention further includes a STOP, which may be located between the second lens L2 and the third lens L3, or may be located between the third lens L3 and the fourth lens L4. In the present invention, the effective focal length f of the prime lens and the image-side radius L1R2 of the first lens L1 satisfy the following relationship: L1R2/f is more than or equal to 1.05 and less than or equal to 1.15. The effective focal length f of the prime lens and the effective focal length f1 of the first lens L1 satisfy the following relationship: f1/f is more than or equal to-2 and less than or equal to-1.8.
In the present invention, the total angle θ 2 of incidence of the second lens L2 and the maximum field angle FOV of the fixed-focus lens satisfy the following relationship: theta 2/FOV is less than or equal to 0.9. Meanwhile, the maximum field angle FOV, the effective focal length f and the maximum full image height H of the fixed-focus lens satisfy the following relationship: 60 is less than or equal to (FOV x f)/H.
According to the arrangement, the first lens L1 can play a role in light collection, so that the light trend is gentle, and the realization of larger image height is facilitated. Specifically, the height of the image plane can reach phi 9.1mm, and the image plane can be adapted to sensors (sensors) such as 1/1.8 ', 1/2.5 ', 1/2.7 ', so that the method has a wide application prospect, and greatly improves the market competitiveness of the fixed-focus lens.
In the present invention, the fourth lens element L4 and the fifth lens element L5 are cemented together to form a (double) cemented lens group having positive optical power. The total angle of incidence θ 4 of the fourth lens L4 and the total angle of incidence θ 5 of the fifth lens L5 satisfy the following relationship: theta 4/theta 5 is less than or equal to 2. The combined focal length fb of the fourth lens L4 and the fifth lens L5 (i.e., the focal length of the cemented lens group) and the effective focal length f of the fixed-focus lens satisfy the following relationship: fb/f is more than or equal to 2.0 and less than or equal to 3.0. Thus, the cemented lens group of the present invention composed of the fourth lens element L4 and the fifth lens element L5 can correct chromatic aberration of the system, which is favorable for achieving higher image quality.
In the present invention, the first lens L1, the second lens L2, the third lens L3, the sixth lens L6, the seventh lens L7 and the eighth lens L8 are plastic lenses. Therefore, the aspheric lens is made of plastic materials, so that high and low temperature imaging is corrected while cost is reduced.
In the utility model, the Fno number of the fixed-focus lens meets the following conditions: fno is less than or equal to 1.2. The Fno number of the fixed-focus lens and the effective focal length f satisfy the following relation: fno/f is more than or equal to 0.1. The effective focal length f of the prime lens and the effective focal length f4 of the fourth lens L4 satisfy the following relationship: f4/f is not less than-3.8 and not more than-2.5. The effective focal length f and the half-image height h of the fixed-focus lens satisfy the following relation: f/h is more than or equal to 0.9 and less than or equal to 1.1. The effective focal length f and the total length TTL of the fixed-focus lens satisfy the following relation: f/TTL is more than or equal to 0.1 and less than or equal to 0.2. The total length TTL, the maximum full image height H and the maximum field angle FOV of the fixed-focus lens satisfy the following relations: TTL/H/FOV is less than or equal to 0.1. The first lens L1 has the maximum object-side light-passing half aperture D and the maximum full image height H and the maximum field angle FOV of the fixed-focus lens satisfying the following relationships: D/H/FOV is less than or equal to 0.1. This is done. Satisfying the above relation is beneficial to realizing higher image quality and ensuring smaller volume.
In the present invention, the temperature coefficient of relative refractive index dn/dt of at least one of the fourth lens element L4 and the fifth lens element L5 satisfies the following relationship: dn/dt is less than or equal to 4 x 10-6V. C. Satisfying the above relation is beneficial to the system to realize no virtual coke in the temperature range of-40 ℃ to 80 ℃.
In the present invention, the air interval T23 between the second lens L2 and the third lens L3 and the total length TTL of the prime lens satisfy the following relationship: T23/TTL is less than or equal to 0.1. Satisfying the above relation makes the air space between the second lens L2 and the third lens L3 insensitive, which is beneficial to the aberration correction and image quality improvement of the system.
In summary, the prime lens of the utility model can realize large aperture and high pixel, Fno is less than or equal to 1.2, large aperture, large light flux, relatively uniform overall illumination and better brightness (relative illumination is more than 40%). The fixed focus lens can also effectively correct aberration by optimally configuring the positive and negative focal powers of all the lenses. In addition, the fixed-focus lens can realize no virtual focus within the temperature range of minus 40 ℃ to 80 ℃, and can be suitable for different environments. Also, image capturing at a maximum field angle of 155 ° can be realized. The total length of the fixed-focus lens is less than or equal to 30mm (with protective plate glass), so the volume is small. And the lens single part and the assembly tolerance are better, thereby having good manufacturability.
The following describes the prime lens of the present invention in five embodiments. In the following embodiments, the surfaces of the lenses are represented by S1, S2, …, and SN, and both the object plane OBJ, the STOP, the image plane IMA, and the plate glass CG are included. Wherein, the plastic aspheric lens satisfies the following formula:
Figure BDA0003078279560000101
wherein z is the axial distance from the curved surface to the top point at the position which is vertical to the optical axis along the optical axis and has the height h; c is the curvature of the vertex of the aspheric surface; k is a conic coefficient; a. the4、A6、A8、A10、A12、A14、A16The aspheric coefficients are four, six, eight, ten, twelve, fourteen and sixteen.
The parameters of each embodiment specifically satisfying the above conditional expressions are shown in table 1 below:
Figure BDA0003078279560000102
TABLE 1
First embodiment
Referring to fig. 1, in the present embodiment, a STOP is located between the third lens L3 and the fourth lens L4. Each parameter of the fixed focus lens in the present embodiment is, F #: 1.02; total lens length: 29.669 mm; the field angle: 148 deg.
The relevant parameters of the lens of the fixed-focus lens in this embodiment include surface type, curvature radius, thickness, refractive index of the material, and abbe number, as shown in table 2 below:
number of noodles Surface type R value Thickness of Refractive index Abbe number
S0(OBJ) Spherical surface Infinity Infinity
S1 Aspherical surface -45.3948 2.1834 1.54 55.7
S2 Aspherical surface 4.7945 2.9021
S3 Aspherical surface -6.0037 1.3701 1.54 55.7
S4 Aspherical surface -16.4047 0.10
S5 Aspherical surface 9.3186 3.9606 1.64 23.5
S6 Aspherical surface 23.1255 0.1926
S7(STO) Spherical surface Infinity 0.10
S8 Spherical surface 49.9993 1.9336 1.74 28.3
S9 Spherical surface 9.2174 3.8487 1.77 49.6
S10 Spherical surface -10.3124 0.2332
S11 Aspherical surface 6.7715 3.1749 1.54 55.7
S12 Aspherical surface -31.9352 0.2583
S13 Aspherical surface -10.1921 0.9981 1.64 23.5
S14 Aspherical surface 11.3716 0.7269
S15 Aspherical surface 5.8374 2.6487 1.54 55.7
S16 Aspherical surface -29.9992 3.9378
S17 Spherical surface Infinity 0.8 1.52 64.2
S18 Spherical surface Infinity 0.3
S19(IMA) Spherical surface Infinity - - -
TABLE 2
The aspherical surface coefficients of the aspherical lenses in this embodiment are shown in table 3 below:
Figure BDA0003078279560000111
Figure BDA0003078279560000121
TABLE 3
Where K is the conic constant of the surface, and A, B, C, D, E, F are aspheric coefficients of fourth, sixth, eighth, tenth, twelfth, and fourteenth orders, respectively.
As can be seen from fig. 2 to 5, the fixed focus lens of the present embodiment can achieve a large aperture and a high pixel count of 250lp/mm, and the MTF of the 0 field is greater than 0.35; the integral illumination is uniform; the defocusing amount is less than 3um in the temperature range of-40 ℃ to 80 ℃, and the focus is not deficient.
Second embodiment
Referring to fig. 6, in the present embodiment, a STOP is located between the second lens L2 and the third lens L3. Each parameter of the fixed focus lens in the present embodiment is, F #: 1.08; total lens length: 29.9982 mm; the field angle: 151 deg.
The parameters related to the lens of the fixed focus lens in this embodiment include surface type, curvature radius, thickness, refractive index of the material, and abbe number, as shown in table 4 below:
Figure BDA0003078279560000122
Figure BDA0003078279560000131
TABLE 4
The aspherical surface coefficients of the aspherical lenses in this embodiment are shown in table 5 below:
Figure BDA0003078279560000132
TABLE 5
Where K is the conic constant of the surface, and A, B, C, D, E, F are aspheric coefficients of fourth, sixth, eighth, tenth, twelfth, and fourteenth orders, respectively.
As can be seen from fig. 7 to 10, the fixed focus lens of the present embodiment can achieve a large aperture and a high pixel count of 250lp/mm, and the MTF of the 0 field is greater than 0.35; the integral illumination is uniform; the defocusing amount is less than 3um in the temperature range of-40 ℃ to 80 ℃, and the focus is not deficient.
Third embodiment
Referring to fig. 11, in the present embodiment, a STOP is located between the third lens L3 and the fourth lens L4. Each parameter of the fixed focus lens in the present embodiment is, F #: 1.05; total lens length: 29.9929 mm; the field angle: 141 deg.
The parameters related to the lens of the fixed focus lens in this embodiment include surface type, curvature radius, thickness, refractive index of the material, and abbe number, as shown in table 6 below:
number of noodles Surface type R value Thickness of Refractive index Abbe number
S0(OBJ) Spherical surface Infinity Infinity
S1 Aspherical surface -57.7913 2.2285 1.54 55.7
S2 Aspherical surface 4.8179 2.8751
S3 Aspherical surface -6.0477 1.3948 1.54 55.7
S4 Aspherical surface -15.5595 0.1
S5 Aspherical surface 9.1217 3.7929 1.64 23.5
S6 Aspherical surface 23.3080 0.5276
S7(STO) Spherical surface Infinity 0.1
S8 Spherical surface 80.0164 1.8237 1.74 27.8
S9 Spherical surface 9.6929 3.5281 1.77 49.6
S10 Spherical surface -10.2485 0.5772
S11 Aspherical surface 6.7575 3.3339 1.54 55.7
S12 Aspherical surface -32.7577 0.2471
S13 Aspherical surface -9.8842 1.0128 1.64 23.5
S14 Aspherical surface 11.5410 0.7810
S15 Aspherical surface 5.9092 2.6438 1.54 55.7
S16 Aspherical surface -28.8888 3.9264
S17 Spherical surface Infinity 0.8 1.52 64.2
S18 Spherical surface Infinity 0.3
S19(IMA) Spherical surface Infinity - - -
TABLE 6
The aspherical surface coefficients of the aspherical lenses in this embodiment are shown in table 7 below:
Figure BDA0003078279560000151
TABLE 7
Where K is the conic constant of the surface, and A, B, C, D, E, F are aspheric coefficients of fourth, sixth, eighth, tenth, twelfth, and fourteenth orders, respectively.
As can be seen from fig. 12 to 15, the fixed focus lens of the present embodiment can realize a large aperture and a high pixel, 250lp/mm, and the MTF of the 0 field is greater than 0.35; the integral illumination is uniform; the defocusing amount is less than 3um in the temperature range of-40 ℃ to 80 ℃, and the focus is not deficient.
Fourth embodiment
Referring to fig. 16, in the present embodiment, a STOP is located between the third lens L3 and the fourth lens L4. Each parameter of the fixed focus lens in the present embodiment is, F #: 1.06; total lens length: 30.0007 mm; the field angle: 143.
The relevant parameters of the lens of the fixed-focus lens in this embodiment include surface type, curvature radius, thickness, refractive index of the material, and abbe number, as shown in table 8 below:
number of noodles Surface type R value Thickness of Refractive index Abbe number
S0(OBJ) Spherical surface Infinity Infinity
S1 Aspherical surface -52.1118 2.3210 1.54 55.7
S2 Aspherical surface 4.8988 2.8722
S3 Aspherical surface -6.0626 1.3622 1.54 55.7
S4 Aspherical surface -15.5958 0.1936
S5 Aspherical surface 9.1486 3.4929 1.64 23.4
S6 Aspherical surface 22.2762 0.5230
S7(STO) Spherical surface Infinity 0.23
S8 Spherical surface 120.8825 1.8250 1.73 28.3
S9 Spherical surface 9.5017 3.6133 1.77 49.6
S10 Spherical surface -10.1915 0.4534
S11 Aspherical surface 6.7651 3.4085 1.54 55.7
S12 Aspherical surface -33.2113 0.2494
S13 Aspherical surface -9.7495 0.9821 1.64 23.4
S14 Aspherical surface 11.6354 0.7571
S15 Aspherical surface 5.8552 2.7065 1.54 55.7
S16 Aspherical surface -28.0937 3.9105
S17 Spherical surface Infinity 0.8 1.52 64.2
S18 Spherical surface Infinity 0.3
S19(IMA) Spherical surface Infinity - - -
TABLE 8
The aspherical coefficients of the aspherical lenses in this embodiment are shown in table 9 below:
Figure BDA0003078279560000161
Figure BDA0003078279560000171
TABLE 9
Where K is the conic constant of the surface, and A, B, C, D, E, F are aspheric coefficients of fourth, sixth, eighth, tenth, twelfth, and fourteenth orders, respectively.
As can be seen from fig. 17 to 20, the fixed focus lens of the present embodiment can realize a large aperture and a high pixel, 250lp/mm, and the MTF of the 0 field is greater than 0.35; the integral illumination is uniform; the defocusing amount is less than 3um in the temperature range of-40 ℃ to 80 ℃, and the focus is not deficient.
Fifth embodiment
Referring to fig. 21, in the present embodiment, a STOP is located between the second lens L2 and the third lens L3. Each parameter of the fixed focus lens in the present embodiment is, F #: 1.20; total lens length: 29.9648 mm; the field angle: 127.
The parameters related to the lens of the fixed focus lens in this embodiment include surface type, curvature radius, thickness, refractive index of the material, and abbe number, as shown in table 10 below:
Figure BDA0003078279560000172
Figure BDA0003078279560000181
watch 10
The aspherical coefficients of the aspherical lenses in this embodiment are shown in table 11 below:
Figure BDA0003078279560000182
TABLE 11
Where K is the conic constant of the surface, and A, B, C, D, E, F are aspheric coefficients of fourth, sixth, eighth, tenth, twelfth, and fourteenth orders, respectively.
As can be seen from fig. 22 to 25, the fixed focus lens of the present embodiment can realize a large aperture and high pixel, 250lp/mm, and the MTF of 0 field is greater than 0.35; the integral illumination is uniform; the defocusing amount is less than 3um in the temperature range of-40 ℃ to 80 ℃, and the focus is not deficient.
The above description is only one embodiment of the present invention, and is not intended to limit the present invention, and it is apparent to those skilled in the art that various modifications and variations can be made in the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (18)

1. A fixed focus lens comprising, in order from an object side to an image side along an optical axis, a first lens (L1) having negative power, a second lens (L2) having negative power, a third lens (L3) having positive power, a fourth lens (L4) having negative power, a fifth lens (L5) having positive power, a sixth lens (L6) having positive power, a seventh lens (L7) having negative power, and an eighth lens (L8) having positive power, characterized in that the first lens (L1) is a biconcave aspheric lens;
an effective focal length f of the prime lens and an effective focal length f1 of the first lens (L1) satisfy the following relationship: f1/f is more than or equal to-2 and less than or equal to-1.8.
2. The fixed focus lens according to claim 1, wherein the second lens (L2) is an aspherical lens of concave-convex type, the third lens (L3) is an aspherical lens of concave-convex type, the fourth lens (L4) is a spherical lens of concave-convex type, the fifth lens (L5) is a spherical lens of biconvex type, the sixth lens (L6) is an aspherical lens of biconvex type, the seventh lens (L7) is an aspherical lens of biconcave type, and the eighth lens (L8) is an aspherical lens of biconvex type.
3. The prime lens according to claim 1, wherein the fourth lens (L4) is cemented with the fifth lens (L5) to form a cemented lens group having positive optical power.
4. The prime lens according to claim 1, further comprising a STOP (STOP) located between the second lens (L2) and the third lens (L3) or between the third lens (L3) and the fourth lens (L4).
5. The prime lens according to claim 2, wherein the first lens (L1), the second lens (L2), the third lens (L3), the sixth lens (L6), the seventh lens (L7), and the eighth lens (L8) are plastic lenses.
6. A prime lens according to any one of claims 1 to 5, wherein the effective focal length f of the prime lens and the image side radius L1R2 of the first lens (L1) satisfy the following relationship: L1R2/f is more than or equal to 1.05 and less than or equal to 1.15.
7. The prime lens according to any one of claims 1 to 5, wherein the full angle of incidence θ 2 of the second lens (L2) and the maximum field angle FOV of the prime lens satisfy the following relationship: theta 2/FOV is less than or equal to 0.9;
the maximum field angle FOV, the effective focal length f and the maximum full image height H of the fixed-focus lens meet the following relations: 60 is less than or equal to (FOV x f)/H.
8. The prime lens according to claim 3, wherein the total angle of incidence θ 4 of the fourth lens (L4) and the total angle of incidence θ 5 of the fifth lens (L5) satisfy the following relationship: theta 4/theta 5 is less than or equal to 2.
9. The prime lens according to claim 3, wherein a combined focal length fb of the fourth lens (L4) and the fifth lens (L5) and an effective focal length f of the prime lens satisfy the following relationship: fb/f is more than or equal to 2.0 and less than or equal to 3.0.
10. The fixed focus lens according to any one of claims 1 to 5, wherein the Fno number of the fixed focus lens satisfies the following condition: fno is less than or equal to 1.2.
11. The prime lens according to any one of claims 1 to 5, wherein the Fno number and the effective focal length f of the prime lens satisfy the following relationship: fno/f is more than or equal to 0.1.
12. The prime lens according to any one of claims 1 to 5, wherein an effective focal length f of the prime lens and an effective focal length f4 of the fourth lens (L4) satisfy the following relationship: f4/f is not less than-3.8 and not more than-2.5.
13. The prime lens according to any one of claims 1 to 5, wherein the effective focal length f and the half-image height h satisfy the following relationship: f/h is more than or equal to 0.9 and less than or equal to 1.1.
14. The fixed focus lens as claimed in any one of claims 1 to 5, wherein an effective focal length f and a total length TTL of the fixed focus lens satisfy the following relationship: f/TTL is more than or equal to 0.1 and less than or equal to 0.2.
15. The fixed focus lens as claimed in any one of claims 1 to 5, wherein the total length TTL, the maximum full image height H, and the maximum field angle FOV of the fixed focus lens satisfy the following relationships: TTL/H/FOV is less than or equal to 0.1.
16. The prime lens according to any one of claims 1 to 5, wherein the first lens (L1) has an object side maximum clear half aperture D and a maximum full image height H and a maximum field angle FOV of the prime lens satisfy the following relationships: D/H/FOV is less than or equal to 0.1.
17. The prime lens according to any one of claims 1 to 5, wherein a temperature coefficient of relative refractive index dn/dt of at least one of the fourth lens (L4) and the fifth lens (L5) satisfies the following condition: dn/dt is less than or equal to 4 x 10-6/℃。
18. The prime lens according to any one of claims 1 to 5, wherein an air interval T23 between the second lens (L2) and the third lens (L3) and a total length TTL of the prime lens satisfy the following relationship: T23/TTL is less than or equal to 0.1.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113126265A (en) * 2021-05-21 2021-07-16 舜宇光学(中山)有限公司 Fixed focus lens
CN114815179A (en) * 2022-06-30 2022-07-29 江西联创电子有限公司 Optical lens

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113126265A (en) * 2021-05-21 2021-07-16 舜宇光学(中山)有限公司 Fixed focus lens
CN114815179A (en) * 2022-06-30 2022-07-29 江西联创电子有限公司 Optical lens
CN114815179B (en) * 2022-06-30 2022-11-01 江西联创电子有限公司 Optical lens

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