CN215729053U - Fixed focus lens - Google Patents

Abstract

The utility model discloses a fixed-focus lens, which comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens which are sequentially arranged from an object plane to an image plane along an optical axis, wherein the first lens has negative focal power; the first lens, the second lens, the seventh lens and the eighth lens are all plastic aspheric lenses, and the third lens, the fourth lens, the fifth lens and the sixth lens are all glass spherical lenses. The prime lens provided by the utility model has the advantages of large aperture, low cost, large target surface and stable high and low temperature performance by setting the number of lenses and the focal power of each lens in the prime lens and adopting a mode of combining a glass lens and a plastic lens.

Description

Fixed focus lens

Technical Field

The embodiment of the utility model relates to the technical field of optical devices, in particular to a fixed-focus lens.

Background

With the progress and development of the optical device industry, the optical lens gradually draws close to the targets with large aperture, large target surface and high pixel. The large aperture can pass more light rays, so that a good imaging effect can be achieved in a dark environment; the larger the area of the photosensitive device is, the better the photosensitive performance is, the higher the signal-to-noise ratio is, and the better the imaging effect is.

The traditional large-aperture prime lens adopts an all-glass structure, so that the defects of large volume, low resolution and high cost are caused. Therefore, the design of a fixed focus lens with large aperture, low cost, large target surface and stable high and low temperature performance is a market development trend.

SUMMERY OF THE UTILITY MODEL

The utility model provides a fixed focus lens, which is used for realizing a fixed focus lens with a large aperture, low cost, a large target surface and stable high and low temperature performance.

An embodiment of the present invention provides a fixed focus lens, including:

the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens are arranged in sequence from the object plane to the image plane along the optical axis;

the first lens has a negative optical power, the second lens has a negative optical power, the third lens has a positive optical power, the fourth lens has a positive optical power, the fifth lens has a negative optical power, the sixth lens has a positive optical power, the seventh lens has a positive optical power, and the eighth lens has a positive optical power;

the first lens, the second lens, the seventh lens and the eighth lens are all plastic aspheric lenses; the third lens, the fourth lens, the fifth lens and the sixth lens are all glass spherical lenses.

Optionally, the fourth lens, the fifth lens and the sixth lens form a triple cemented lens group.

Optionally, an object-side surface of the first lens is a concave surface, and an 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 concave 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;

the object side surface of the fifth lens is a convex surface;

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

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

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

Optionally, the focal power of the first lens is ψ 1, the focal power of the second lens is ψ 2, the focal power of the third lens is ψ 3, the focal power of the fourth lens is ψ 4, the focal power of the fifth lens is ψ 5, the focal power of the sixth lens is ψ 6, the focal power of the seventh lens is ψ 7, and the focal power of the eighth lens is ψ 8, where:

-0.12＜ψ1＜-0.08；-0.03＜ψ2＜-0.1；0.08＜ψ3＜0.1；0.03＜ψ4＜0.05；-0.03＜ψ5＜-0.02；-0.01＜ψ6＜0.01；0.01＜ψ7＜0.04；0.03＜ψ8＜0.06。

optionally, a focal length of the first lens is f1, a focal length of the second lens is f2, a focal length of the seventh lens is f7, a focal length of the eighth lens is f8, and a focal length of the fixed focus lens is f, where:

1.8≤|f1/f|≤2.2；8.3≤|f2/f|≤10.2；5.3≤|f7/f|≤15.1；3.5≤|f8/f|≤5.5。

optionally, a focal length of the third lens is f3, a focal length of the fourth lens is f4, a focal length of the fifth lens is f5, a focal length of the sixth lens is f6, and a focal length of the fixed focus lens is f, where:

2≤|f3/f|≤2.5；7.8≤|(f4+f5+f6)/f|≤12.1。

optionally, a distance from an optical axis center of an image-side surface of the eighth lens element to the image plane is BFL, and a distance from an optical axis center of an object-side surface of the first lens element to the image plane is TTL, where BFL/TTL is greater than 0.17.

Optionally, the refractive index of the first lens is nd1, and the abbe number is vd 1; the refractive index of the second lens is nd2, and the Abbe number is vd 2; the refractive index of the seventh lens is nd7, and the Abbe number is vd 7; the refractive index of the eighth lens is nd8, the Abbe number is vd8, wherein:

1.5<nd1<1.6，55<vd1<95；1.52<nd2<2.1，55<vd2<95；1.62<nd7<1.81，16<vd7<95；1.53<nd8<1.6，55<vd8<95。

optionally, the refractive index of the third lens is nd3, and the abbe number is vd 3; the refractive index of the fourth lens is nd4, and the Abbe number is vd 4; the refractive index of the fifth lens is nd5, and the Abbe number is vd 5; the refractive index of the sixth lens is nd6, the Abbe number is vd6, wherein:

1.78<nd3<2.1，25<vd3<40；1.58<nd4<1.60，48<vd4<90；1.59<nd5<1.86，22<vd5<50；1.58<nd6<1.61，57<vd6<95。

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

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

The fixed focus lens provided by the embodiment of the utility model is provided with a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens which are sequentially arranged from an object plane to an image plane along an optical axis, wherein the first lens has negative focal power, the second lens has negative focal power, the third lens has positive focal power, the fourth lens has positive focal power, the fifth lens has negative focal power, the sixth lens has positive focal power, the seventh lens has positive focal power, and the eighth lens has positive focal power; the first lens, the second lens, the seventh lens and the eighth lens are all plastic aspheric lenses; the third lens, the fourth lens, the fifth lens and the sixth lens are all glass spherical lenses, so that the large-aperture fixed-focus lens with the aperture F being less than or equal to 1.0 is realized by reasonably setting the number of the lenses in the fixed-focus lens and the focal power of each lens and adopting a mode of combining the glass lenses and the plastic lenses, and the large-aperture fixed-focus lens has a large target surface, can be matched with a 1/1.8' oversized target surface sensing chip to the maximum extent, can meet the use conditions of-40-80 ℃, improves the environmental adaptability and effectively reduces the cost of the fixed-focus lens.

Drawings

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

FIG. 2 is a graph illustrating axial aberration curves according to a first embodiment of the present invention;

FIG. 3 is a graph of field curvature provided by an embodiment of the present invention;

FIG. 4 is a distortion curve provided by the first embodiment of the present invention;

FIG. 5 is a graph of color difference provided by the first embodiment of the present invention;

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

FIG. 7 is a graph illustrating axial aberrations according to a second embodiment of the present invention;

FIG. 8 is a graph of field curvature provided by a second embodiment of the present invention;

FIG. 9 is a distortion curve chart provided in the second embodiment of the present invention;

FIG. 10 is a graph of color difference provided by a second embodiment of the present invention;

fig. 11 is a schematic structural diagram of a fixed-focus lens according to a third embodiment of the present invention;

FIG. 12 is a graph illustrating axial aberrations provided by a third embodiment of the present invention;

FIG. 13 is a graph of field curvature provided by a third embodiment of the present invention;

FIG. 14 is a distortion curve chart provided in the third embodiment of the present invention;

FIG. 15 is a graph of color difference provided by a third embodiment of the present invention;

fig. 16 is a schematic structural diagram of a fixed-focus lens according to a fourth embodiment of the present invention;

FIG. 17 is a graph illustrating axial aberrations according to the fourth embodiment of the present invention;

FIG. 18 is a graph of field curvature provided by a fourth embodiment of the present invention;

FIG. 19 is a distortion plot provided in accordance with a fourth embodiment of the present invention;

fig. 20 is a graph of color difference provided by the fourth 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 utility model and are not limiting of the utility model. 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.

Fig. 1 is a schematic structural diagram of a fixed focus lens according to an embodiment of the present invention, and as shown in fig. 1, the fixed focus lens according to the embodiment of the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, a seventh lens 170, and an eighth lens 180, which are sequentially disposed along an optical axis from an object plane to an image plane. The first lens 110 has a negative power, the second lens 120 has a negative power, the third lens 130 has a positive power, the fourth lens 140 has a positive power, the fifth lens 150 has a negative power, the sixth lens 160 has a positive power, the seventh lens 170 has a positive power, and the eighth lens 180 has a positive power. The first lens 110, the second lens 120, the seventh lens 170, and the eighth lens 180 are all plastic aspherical lenses, and the third lens 130, the fourth lens 140, the fifth lens 150, and the sixth lens 160 are all glass spherical lenses.

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 the present embodiment, each lens may be fixed in a lens barrel (not shown in fig. 1), and the first lens 110 is set to be a negative power lens for controlling the incident angle of the optical system; the second lens 120 and the fifth lens 150 have negative optical power; the third lens 130, the fourth lens 140, the sixth lens 160, the seventh lens 170 and the eighth lens 180 have positive focal power, and the focal power of the whole fixed-focus lens is distributed according to a certain proportion, so that the balance of the incident angles of the front and rear lens groups is ensured, the sensitivity of the lens is reduced, and the production possibility is improved.

Meanwhile, in the present embodiment, the first lens 110, the second lens 120, the seventh lens 170, and the eighth lens 180 are all plastic aspheric lenses, and are used for correcting off-axis aberrations including field curvature, coma, astigmatism, and the like, so that the image quality is good and the cost is low; the third lens 130, the fourth lens 140, the fifth lens 150 and the sixth lens 160 are all glass spherical lenses, so that two materials of glass and plastic play a mutual compensation role, the high and low temperatures can be balanced, the total length of the lens can be reduced, the fixed-focus lens has the characteristic of stable high and low temperature performance, and the environmental adaptability of the fixed-focus lens is improved.

The plastic aspheric lens may be made of various plastics known to those skilled in the art, and the glass spherical lens may be made of various types of glass known to those skilled in the art, which is not limited in the embodiments of the present invention.

According to the prime lens provided by the embodiment of the utility model, the number of the lenses in the prime lens and the focal power of each lens are reasonably set, and a mode of combining a glass lens and a plastic lens is adopted, so that the large-aperture prime lens with the aperture F less than or equal to 1.0 can be realized, and the large-aperture prime lens has a large target surface, can be matched with a 1/1.8' oversized target surface sensing chip to the maximum extent, and meanwhile, the service condition of-40-80 ℃ can be met, the environmental adaptability is improved, and the cost of the prime lens is effectively reduced.

With continued reference to fig. 1, optionally, the fourth lens 140, the fifth lens 150, and the sixth lens 160 comprise a triple cemented lens group.

Wherein, by arranging the fourth lens 140, the fifth lens 150 and the sixth lens 160 to form a triple cemented lens group, the air space between the fourth lens 140, the fifth lens 150 and the sixth lens 160 can be effectively reduced, thereby reducing the total lens length. In addition, the triple-cemented lens group can reduce chromatic aberration or eliminate chromatic aberration to the maximum extent, so that various aberrations of the fixed-focus lens can be fully corrected, the resolution can be improved, the optical performances such as distortion and the like can be optimized on the premise of compact structure, the light quantity loss caused by reflection between lenses can be reduced, the illumination intensity is improved, the image quality is improved, and the imaging definition of the lens is improved. In addition, the use of the triple cemented lens group can also reduce the assembly parts between the two lenses, simplify the assembly procedure in the lens manufacturing process, reduce the cost and reduce the tolerance sensitivity problems of the lens units, such as inclination/decentration, and the like, generated in the assembly process.

Optionally, the fourth lens 140, the fifth lens 150, and the sixth lens 160 may be supported by spacers to form a triple cemented lens group, which is a simpler process. In other embodiments, the fourth lens 140, the fifth lens 150, and the sixth lens 160 may also be bonded together by glue to form a triple cemented lens group, which can be set by those skilled in the art according to actual needs.

With continued reference to fig. 1, optionally, the object-side surface of the first lens element 110 is concave, and the image-side surface of the first lens element 110 is concave; the object-side surface of the second lens element 120 is convex, and the image-side surface of the second lens element 120 is convex; the object-side surface of the third lens element 130 is a concave surface, and the image-side surface of the third lens element 130 is a convex surface; the object side surface of the fourth lens element 140 is concave; the object-side surface of the fifth lens element 150 is convex; the object-side surface of the sixth lens element 160 is concave, and the image-side surface of the sixth lens element 160 is convex; the object-side surface of the seventh lens element 170 is convex, and the image-side surface of the seventh lens element 170 is convex; the object-side surface of the eighth lens element 180 is concave, and the image-side surface of the eighth lens element 180 is concave.

The surface of the lens adjacent to the object plane is an object side surface, and the surface of the lens adjacent to the image plane is an image side surface. Concave refers to the surface convex towards the object plane, convex refers to the surface convex towards the image plane.

In this embodiment, by reasonably setting the surface type of each lens, the focal power of each lens and the focal power requirement in the above embodiments are ensured, and at the same time, the whole fixed-focus lens can be ensured to have a compact structure, and the integration level of the fixed-focus lens is high.

Optionally, the focal power of the first lens 110 is ψ 1, the focal power of the second lens 120 is ψ 2, the focal power of the third lens 130 is ψ 3, the focal power of the fourth lens 140 is ψ 4, the focal power of the fifth lens 150 is ψ 5, the focal power of the sixth lens 160 is ψ 6, the focal power of the seventh lens 170 is ψ 7, and the focal power of the eighth lens 180 is ψ 8, where:

-0.12＜ψ1＜-0.08；-0.03＜ψ2＜-0.1；0.08＜ψ3＜0.1；0.03＜ψ4＜0.05；-0.03＜ψ5＜-0.02；-0.01＜ψ6＜0.01；0.01＜ψ7＜0.04；0.03＜ψ8＜0.06。

the focal power of each lens is reasonably distributed, so that the correction of aberration in the case of an ultra-large aperture is facilitated, and the prime lens is ensured to have higher resolving power.

Optionally, the focal length of the first lens 110 is f1, the focal length of the second lens 120 is f2, the focal length of the seventh lens 170 is f7, the focal length of the eighth lens 180 is f8, and the focal length of the fixed-focus lens is f, where:

1.8≤|f1/f|≤2.2；8.3≤|f2/f|≤10.2；5.3≤|f7/f|≤15.1；3.5≤|f8/f|≤5.5。

the ratio relationship between the focal lengths of the first lens 110, the second lens 120, the seventh lens 170 and the eighth lens 180 and the focal length of the fixed focus lens is reasonably set, so that the off-axis aberrations such as field curvature, coma aberration and astigmatism can be better corrected, and the fixed focus lens is ensured to have higher resolving power.

Optionally, the focal length of the third lens 130 is f3, the focal length of the fourth lens 140 is f4, the focal length of the fifth lens 150 is f5, the focal length of the sixth lens 160 is f6, and the focal length of the fixed-focus lens is f, where:

2≤|f3/f|≤2.5；7.8≤|(f4+f5+f6)/f|≤12.1。

the ratio relationship between the focal lengths of the third lens 130, the fourth lens 140, the fifth lens 150 and the sixth lens 160 and the focal length of the fixed-focus lens is reasonably set, so that the total length of the lens is reduced, the correction of aberration in the case of an oversized aperture is facilitated, and the fixed-focus lens is ensured to have higher resolving power.

Optionally, a distance from an optical axis center of an image-side surface of the eighth lens element 180 to the image plane is BFL, and a distance from an optical axis center of an object-side surface of the first lens element 110 to the image plane is TTL, where BFL/TTL > 0.17.

The distance from the optical axis center of the image side surface of the eighth lens element 180 to the image plane can be understood as the back focal length of the fixed-focus lens, the distance from the optical axis center of the object side surface of the first lens element 110 to the image plane can be understood as the optical total length of the fixed-focus lens, and by reasonably setting the relationship between the back focal length of the fixed-focus lens and the total length of the fixed-focus lens, the compact structure of the whole fixed-focus lens can be ensured, the integration level of the fixed-focus lens is high, and sufficient installation space for the imaging sensor and the flat plate filter can be ensured while the short total length is realized.

Optionally, the refractive index of the first lens 110 is nd1, and the abbe number is vd 1; the refractive index of the second lens 120 is nd2, and the Abbe number is vd 2; the refractive index of the seventh lens 170 is nd7, and the Abbe number is vd 7; the refractive index of the eighth lens 180 is nd8, and the abbe number is vd8, wherein:

1.5<nd1<1.6，55<vd1<95；1.52<nd2<2.1，55<vd2<95；1.62<nd7<1.81，16<vd7<95；1.53<nd8<1.6，55<vd8<95。

the refractive index is the ratio of the propagation speed of light in vacuum to the propagation speed of light in the medium, and is mainly used for describing the refractive power of materials to light, and the refractive indexes of different materials are different. The abbe number is an index for expressing the dispersion capability of the transparent medium, and the more severe the dispersion of the medium is, the smaller the abbe number is; conversely, the more slight the dispersion of the medium, the greater the abbe number.

In this embodiment, the first lens 110, the second lens 120, the seventh lens 170, and the eighth lens 180 are made of plastic materials, so as to save cost and reduce weight, and meanwhile, by arranging the refractive indexes and abbe numbers of the first lens 110, the second lens 120, the seventh lens 170, and the eighth lens 180 in the fixed-focus lens in a matching manner, the uniformity of the incident angle of the front and rear lens groups is ensured, the sensitivity of the lens is reduced, and the implementation of higher pixel resolution is facilitated.

Optionally, the refractive index of the third lens 130 is nd3, and the abbe number is vd 3; the refractive index of the fourth lens 140 is nd4, and the Abbe number is vd 4; the refractive index of the fifth lens 150 is nd5, and the Abbe number is vd 5; the refractive index of the sixth lens 160 is nd6, and the abbe number is vd6, wherein:

1.78<nd3<2.1，25<vd3<40；1.58<nd4<1.60，48<vd4<90；1.59<nd5<1.86，22<vd5<50；1.58<nd6<1.61，57<vd6<95。

meanwhile, the refractive indexes and abbe numbers of the third lens 130, the fourth lens 140, the fifth lens 150 and the sixth lens 160 in the fixed-focus lens are matched, so that the balance of the incident angles of the front and rear lens groups is ensured, the sensitivity of the lens is reduced, and the realization of higher pixel resolution is facilitated.

With reference to fig. 1, optionally, the fixed focus lens provided in the embodiment of the present invention further includes a diaphragm 210, where the diaphragm 210 is located in an optical path between the second lens 120 and the third lens 130.

By arranging the diaphragm 210 in the optical path between the second lens 120 and the third lens 130, 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 improving the imaging quality.

With reference to fig. 1, optionally, the fixed-focus lens provided in the embodiment of the present invention further includes a flat filter 220, where the flat filter 220 is disposed on the image-side surface side of the eighth lens element 180.

The flat filter 220 is disposed between the eighth lens element 180 and the image plane to filter out unwanted stray light, so as to improve the image quality of the fixed focus lens, for example, the flat filter 220 filters out infrared light in the daytime to improve the imaging quality of the fixed focus lens.

Specific examples of the optical imaging lens group applicable to the above embodiments are further described below with reference to the drawings.

Example one

With continued reference to fig. 1, a fixed-focus lens provided in the first embodiment of the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, a seventh lens 170, and an eighth lens 180, which are sequentially disposed along an optical axis from an object plane to an image plane, wherein a stop 210 is disposed in an optical path between the second lens 120 and the third lens 130. Table 1 shows the radius of curvature, thickness, refractive index, abbe number, focal power applicable range, lens focal length/lens focal length, and lens focal length/lens focal length range of each lens in the fixed-focus lens provided in the first embodiment, where the unit of the radius of curvature and the unit of the thickness are both millimeters (mm).

TABLE 1 design value of prime lens

The surface numbers in Table 1 are numbered according to the order of the surfaces of the respective lenses, where "S1" represents the object-side surface of the first lens 110, "S2" represents the image-side surface of the first lens 110, and so on; "STO" represents the stop 210 of the fixed focus lens; 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, and a negative value represents that the surface is bent to the object surface side; wherein "PL" represents that the surface is planar with a radius of curvature of infinity; 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; "ψ 1" represents the optical power of the first lens 110, "ψ 2" represents the optical power of the second lens 120, and so on.

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.

Illustratively, table 2 details the aspheric coefficients of the lenses of the first embodiment in a possible implementation manner.

TABLE 2 design value of aspheric coefficients in fixed-focus lens

Value of K

A

B

C

D

E

F

S1

-101.94

-1.439708E-03

1.059440E-04

-4.517293E-06

1.185423E-07

-1.751585E-09

1.108648E-11

S2

-0.65

-1.297243E-03

8.351855E-05

7.879008E-06

-9.548998E-07

4.724012E-08

-6.630737E-10

S3

-3.61

-2.979532E-03

1.793181E-04

-3.788224E-06

-2.786528E-07

2.627905E-08

-6.771277E-10

S4

-6.56

-2.100298E-03

1.559358E-04

-8.412705E-06

3.477469E-07

-8.638659E-09

8.068894E-11

S12

-93.23

1.938502E-03

-1.683811E-04

1.048673E-05

-6.481777E-07

2.463469E-08

-4.290869E-10

S13

12.51

1.259426E-03

-6.812742E-05

3.226345E-06

-1.890461E-07

7.370430E-09

-1.215410E-10

S14

-5.47

1.187781E-03

-8.401625E-05

5.778210E-06

-1.308943E-07

2.099464E-09

2.834341E-12

S15

0.83

-1.224484E-03

7.611336E-05

-7.560849E-06

9.922973E-07

-5.4837S6E-08

1.370292E-09

wherein-1.439708E-03 indicates that the coefficient A with the surface number S1 is-1.439708 x 10^-3And so on.

The prime lens of the first embodiment achieves the following technical indexes:

focal length: f is 5.1 mm;

f number: f is 1.0;

BFL/TTL＝0.17。

further, fig. 2 is a graph of axial aberration provided by the first embodiment of the present invention, as shown in fig. 2, the phase differences of the fixed-focus lens at different wavelengths (0.436 μm, 0.486 μm, 0.588 μm, and 0.656 μm) are all within 0.03mm, and different wavelength curves are relatively concentrated, which indicates that the axial aberration of the fixed-focus lens is small, so that it can be known that the fixed-focus lens provided by the first embodiment of the present invention can better correct aberration.

Fig. 3 is a graph of curvature of field according to an embodiment of the present invention, as shown in fig. 3, a horizontal coordinate represents the size of curvature of field in mm; the vertical coordinate represents the normalized image height, with no units; wherein T represents meridian and S represents arc loss; as can be seen from fig. 3, the fixed focus lens provided by this embodiment is effectively controlled in curvature of field from light with a wavelength of 436nm to light with a wavelength of 656nm, i.e. when imaging, the difference between the image quality at the center and the image quality at the periphery is small.

Fig. 4 is a distortion curve chart provided in the first embodiment of the present invention, as shown in fig. 4, a horizontal coordinate represents the magnitude of distortion, and the unit is%; the vertical coordinate represents the normalized image height, with no units; as can be seen from fig. 4, the distortion of the fixed-focus lens provided by the embodiment is better corrected, the imaging distortion is smaller, and the requirement of low distortion is met.

Fig. 5 is a graph of chromatic aberration provided by the first embodiment of the present invention, as shown in fig. 5, a vertical direction represents normalization of an angle of view, 0 represents on an optical axis, and a vertex in the vertical direction represents a maximum radius of the field of view; the horizontal direction is the offset in units of microns (μm) with 0.588 μm as the reference meridian range. The numbers on the graph in the figure indicate the wavelength represented by the graph in microns (mum), and it can be seen from fig. 5 that the homeotropic chromatic aberration can be controlled in the range of (-3 μm, 2 μm).

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, the fixed-focus lens according to the second embodiment of the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, a seventh lens 170, and an eighth lens 180, which are sequentially disposed along an optical axis from an object plane to an image plane, wherein a stop 210 is disposed in an optical path between the second lens 120 and the third lens 130. Table 3 shows the radius of curvature, thickness, refractive index, abbe number, focal power applicable range, lens focal length/lens focal length, and lens focal length/lens focal length range of each lens in the fixed-focus lens provided in example two, where the unit of the radius of curvature and the unit of the thickness are both millimeters (mm).

TABLE 3 design value of prime lens

The surface numbers in Table 3 are numbered according to the order of the surfaces of the respective lenses, where "S1" represents the object-side surface of the first lens 110, "S2" represents the image-side surface of the first lens 110, and so on; "STO" represents the stop 210 of the fixed focus lens; 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, and a negative value represents that the surface is bent to the object surface side; wherein "PL" represents that the surface is planar with a radius of curvature of infinity; 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; "ψ 1" represents the optical power of the first lens 110, "ψ 2" represents the optical power of the second lens 120, and so on.

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.

Table 4 illustrates aspheric coefficients of each lens in the second embodiment in a possible implementation manner.

TABLE 4 design value of aspheric surface coefficient in fixed focus lens

Value of K

A

B

C

D

E

F

S1

-102.00

-1.444793E-03

1.064705E-04

-4.512554E-06

1.185619E-07

-1.752192E-09

1.106355E-11

S2

-0.74

-1.459009E-03

8.160026E-05

7.659005E-06

-9.687401E-07

4.654309E-08

-7.153960E-10

S3

-3.64

-2.957773E-03

1.792414E-04

-3.898485E-06

-2.834901E-07

2.637667E-08

-6.405333E-10

S4

-6.76

-2.094722E-03

1.561416E-04

-8.385858E-06

3.493443E-07

-8.543631E-09

8.678601E-11

S12

-99.39

1.968411E-03

-1.673490E-04

1.047564E-05

-6.500424E-07

2.455232E-08

-4.201471E-10

S13

12.34

1.245419E-03

-6.835286E-05

3.245377E-06

-1.870734E-07

7.374259E-09

-1.217207E-10

S14

-5.90

1.196705E-03

-8.151998E-05

5.709664E-06

-1.297025E-07

2.146931E-09

1.268830E-11

S15

1.41

-1.117376E-03

7.298519E-05

-7.656442E-06

9.968044E-07

-5.517890E-08

1.408340E-09

wherein-1.444793E-03 indicates that the coefficient A with the surface number S1 is-1.444793 x 10^-3And so on.

The fixed-focus lens of the second embodiment achieves the following technical indexes:

focal length: f is 5.1 mm;

f number: f is 1.0;

BFL/TTL＝0.17。

further, fig. 7 is a graph of axial aberration provided in the second embodiment of the present invention, as shown in fig. 7, the phase differences of the fixed-focus lens at different wavelengths (0.436 μm, 0.486 μm, 0.588 μm, and 0.656 μm) are all within 0.04mm, and the curves of different wavelengths are relatively concentrated, which indicates that the axial aberration of the fixed-focus lens is small, so that it can be known that the fixed-focus lens provided in the second embodiment of the present invention can better correct the aberration.

Fig. 8 is a graph of curvature of field according to a second embodiment of the present invention, as shown in fig. 8, the horizontal coordinate represents the size of the curvature of field in mm; the vertical coordinate represents the normalized image height, with no units; wherein T represents meridian and S represents arc loss; as can be seen from fig. 8, the fixed focus lens provided by this embodiment is effectively controlled in curvature of field from light with a wavelength of 436nm to light with a wavelength of 656nm, that is, when imaging, the difference between the image quality at the center and the image quality at the periphery is small.

Fig. 9 is a distortion curve chart provided by the second embodiment of the present invention, as shown in fig. 9, a horizontal coordinate represents the magnitude of distortion, and the unit is%; the vertical coordinate represents the normalized image height, with no units; as can be seen from fig. 9, the distortion of the fixed-focus lens provided by the embodiment is better corrected, the imaging distortion is smaller, and the requirement of low distortion is met.

Fig. 10 is a graph of chromatic aberration provided by the second embodiment of the present invention, as shown in fig. 10, a vertical direction represents normalization of a field angle, 0 represents on an optical axis, and a vertex in the vertical direction represents a maximum field radius; the horizontal direction is the offset in units of microns (μm) with 0.588 μm as the reference meridian range. The numbers on the graph in the figure indicate the wavelength represented by the graph in microns (mum), and it can be seen from fig. 10 that the homeotropic chromatic aberration can be controlled in the range of (-1.5 μm, 1.5 μm).

EXAMPLE III

Fig. 11 is a schematic structural diagram of a fixed-focus lens according to a third embodiment of the present invention, and as shown in fig. 11, the fixed-focus lens according to the third embodiment of the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, a seventh lens 170, and an eighth lens 180, which are sequentially disposed along an optical axis from an object plane to an image plane, where a stop 210 is disposed in an optical path between the second lens 120 and the third lens 130. Table 5 shows the radius of curvature, thickness, refractive index, abbe number, focal power applicable range, lens focal length/lens focal length, and lens focal length/lens focal length range of each lens in the fixed-focus lens provided in example three, where the unit of the radius of curvature and the thickness are both millimeters (mm).

TABLE 5 design value of prime lens

The surface numbers in Table 5 are numbered according to the order of the surfaces of the respective lenses, where "S1" represents the object-side surface of the first lens 110, "S2" represents the image-side surface of the first lens 110, and so on; "STO" represents the stop 210 of the fixed focus lens; 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, and a negative value represents that the surface is bent to the object surface side; wherein "PL" represents that the surface is planar with a radius of curvature of infinity; 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; "ψ 1" represents the optical power of the first lens 110, "ψ 2" represents the optical power of the second lens 120, and so on.

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.

Table 6 illustrates aspheric coefficients of each lens in the third embodiment in a possible implementation manner.

TABLE 6 design value of aspheric surface coefficient in fixed-focus lens

Value of K

A

B

C

D

E

F

S1

-71.63

-1.393281E-03

1.066393E-04

-4.506880E-06

1.185953E-07

-1.755326E-09

1.100045E-11

S2

-0.73

-1.502129E-03

1.024720E-04

7.567828E-06

-9.772340E-07

4.688189E-08

-4.613617E-10

S3

-4.17

-2.896690E-03

1.800139E-04

-3.836329E-06

-2.739294E-07

2.642140E-08

-6.895358E-10

S4

-7.48

-2.138851E-03

1.534905E-04

-8.384553E-06

3.525436E-07

-8.561286E-09

7.983919E-11

S12

100.00

2.201181E-03

-1.585593E-04

1.037104E-05

-6.618475E-07

2.444774E-08

-4.056142E-10

S13

11.11

1.123878E-03

-6.398389E-05

3.344228E-06

-1.936791E-07

6.934976E-09

-1.231050E-10

S14

-7.54

9.997580E-04

-8.489449E-05

5.8487S2E-06

-1.284571E-07

2.022344E-09

-2.268211E-12

S15

1.00

-1.270852E-03

9.071807E-05

-7.360970E-06

9.573770E-07

-5.588901E-08

1.527175E-09

wherein-1.393281E-03 indicates that the coefficient A with the surface number S1 is-1.393281 x 10^-3And so on.

The prime lens in the third embodiment achieves the following technical indexes:

focal length: f is 4.93 mm;

f number: f is 1.0;

BFL/TTL＝0.18。

further, fig. 12 is a graph of axial aberration provided by the third embodiment of the present invention, as shown in fig. 12, the phase differences of the fixed-focus lens at different wavelengths (0.436 μm, 0.486 μm, 0.588 μm, and 0.656 μm) are all within 0.04mm, and the curves of different wavelengths are relatively concentrated, which indicates that the axial aberration of the fixed-focus lens is small, so that it can be known that the fixed-focus lens provided by the third embodiment of the present invention can better correct the aberration.

Fig. 13 is a graph of curvature of field according to a third embodiment of the present invention, as shown in fig. 13, the horizontal coordinate represents the size of curvature of field in mm; the vertical coordinate represents the normalized image height, with no units; wherein T represents meridian and S represents arc loss; as can be seen from fig. 13, the fixed focus lens provided by this embodiment is effectively controlled in curvature of field from light with a wavelength of 436nm to light with a wavelength of 656nm, that is, when imaging, the difference between the image quality at the center and the image quality at the periphery is small.

Fig. 14 is a distortion curve chart provided by the third embodiment of the present invention, as shown in fig. 14, a horizontal coordinate represents the magnitude of distortion, and the unit is%; the vertical coordinate represents the normalized image height, with no units; as can be seen from fig. 14, the distortion of the fixed-focus lens provided by the embodiment is better corrected, the imaging distortion is smaller, and the requirement of low distortion is met.

Fig. 15 is a graph of chromatic aberration provided by the third embodiment of the present invention, as shown in fig. 15, a vertical direction represents normalization of a field angle, 0 represents on an optical axis, and a vertex in the vertical direction represents a maximum field radius; the horizontal direction is the offset in units of microns (μm) with 0.588 μm as the reference meridian range. The numbers on the graph in the figure indicate the wavelength represented by the graph in microns (mum), and it can be seen from fig. 15 that the homeotropic chromatic aberration can be controlled in the range of (-1 μm, 1 μm).

Example four

Fig. 16 is a schematic structural diagram of a fixed focus lens according to a fourth embodiment of the present invention, and as shown in fig. 16, the fixed focus lens according to the fourth embodiment of the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, a seventh lens 170, and an eighth lens 180, which are sequentially disposed along an optical axis from an object plane to an image plane, wherein a stop 210 is disposed in an optical path between the second lens 120 and the third lens 130. Table 7 shows the radius of curvature, thickness, refractive index, abbe number, optical power, applicable range of optical power, focal length/focal length of lens, and range of focal length/focal length of lens of each lens in the fixed-focus lens provided in example four, in which the unit of the radius of curvature and the thickness are both millimeters (mm).

TABLE 7 design value of prime lens

The surface numbers in table 7 are numbered according to the surface order of the respective lenses, where "S1" represents the object-side surface of the first lens 110, "S2" represents the image-side surface of the first lens 110, and so on; "STO" represents the stop 210 of the fixed focus lens; 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, and a negative value represents that the surface is bent to the object surface side; wherein "PL" represents that the surface is planar with a radius of curvature of infinity; 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; "ψ 1" represents the optical power of the first lens 110, "ψ 2" represents the optical power of the second lens 120, and so on.

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.

Table 8 illustrates aspheric coefficients of each lens in the fourth embodiment in a possible implementation manner.

TABLE 8 design value of aspheric surface coefficient in fixed-focus lens

Value of K

A

B

C

D

E

F

S1

-26.45

-1.387542E-03

1.066978E-04

-4.520950E-06

1.179532E-07

-1.759582E-09

1.139633E-11

S2

-0.71

-1.433493E-03

1.000163E-04

7.885610E-06

-9.990487E-07

4.688747E-08

-4.418887E-10

S3

-3.91

-2.866051E-03

1.828766E-04

-3.700490E-06

-2.848531E-07

2.595164E-08

-6.461592E-10

S4

-7.06

-2.172531E-03

1.542630E-04

-8.352081E-06

3.512013E-07

-8.529883E-09

7.996376E-11

S12

-100.06

2.020666E-03

-1.688966E-04

1.035758E-05

-6.536941E-07

2.450901E-08

-4.222777E-10

S13

11.46

1.185090E-03

-7.094202E-05

3.107015E-06

-1.936260E-07

7.210894E-09

-1.166997E-10

S14

-6.18

1.179960E-03

-8.802734E-05

5.556458E-06

-1.316552E-07

2.224032E-09

3.953249E-12

S15

1.96

-1.061988E-03

6.744278E-05

-7.696498E-06

9.987508E-07

-5.518951E-08

1.342898E-09

wherein-1.387542E-03 indicates that the coefficient A with the surface number S1 is-1.387542 x 10^-3And so on.

The fixed-focus lens in the fourth embodiment achieves the following technical indexes:

focal length: f is 5.02 mm;

f number: f is 0.96;

BFL/TTL＝0.18。

further, fig. 17 is a graph of axial aberration provided in the fourth embodiment of the present invention, as shown in fig. 17, the phase differences of the fixed-focus lens at different wavelengths (0.436 μm, 0.486 μm, 0.588 μm, and 0.656 μm) are all within 0.07mm, and different wavelength curves are relatively concentrated, which indicates that the axial aberration of the fixed-focus lens is small, so that it can be known that the fixed-focus lens provided in the fourth embodiment of the present invention can correct the aberration well.

Fig. 18 is a graph of curvature of field according to a fourth embodiment of the present invention, as shown in fig. 18, the horizontal coordinate represents the size of the curvature of field in mm; the vertical coordinate represents the normalized image height, with no units; wherein T represents meridian and S represents arc loss; as can be seen from fig. 18, the fixed focus lens provided by this embodiment is effectively controlled in curvature of field from light with a wavelength of 436nm to light with a wavelength of 656nm, that is, when imaging, the difference between the image quality at the center and the image quality at the periphery is small.

Fig. 19 is a distortion curve chart according to a fourth embodiment of the present invention, as shown in fig. 19, a horizontal coordinate represents the magnitude of distortion in units of%; the vertical coordinate represents the normalized image height, with no units; as can be seen from fig. 19, the distortion of the fixed-focus lens provided by the embodiment is better corrected, the imaging distortion is smaller, and the requirement of low distortion is met.

Fig. 20 is a graph of chromatic aberration provided by the fourth embodiment of the present invention, as shown in fig. 20, the vertical direction represents the normalization of the field angle, 0 represents on the optical axis, and the vertex in the vertical direction represents the maximum field radius; the horizontal direction is the offset in units of microns (μm) with 0.588 μm as the reference meridian range. The numbers on the graph in the figure indicate the wavelength represented by the graph in microns (mum), and it can be seen from fig. 20 that the homeotropic chromatic aberration can be controlled in the range of (-2 μm, 1 μm).

According to the prime lens provided by the embodiment of the utility model, through reasonably setting the number of the lenses, the material, focal power, focal length, refractive index, Abbe number and the like in the prime lens, the aperture F is less than or equal to 1.0, the ultra-large target surface sensing chip of 1/1.8' can be matched to the maximum extent, and the use condition of minus 40-80 ℃ can be met, so that the prime lens has the characteristics of large aperture, large target surface, small purple edge and low cost, and the prime lens can be matched with a day-night full-color camera to use.

It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. 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 utility model. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims (10)

1. A prime lens, comprising:

the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens are arranged in sequence from the object plane to the image plane along the optical axis;

the first lens has a negative optical power, the second lens has a negative optical power, the third lens has a positive optical power, the fourth lens has a positive optical power, the fifth lens has a negative optical power, the sixth lens has a positive optical power, the seventh lens has a positive optical power, and the eighth lens has a positive optical power;

the first lens, the second lens, the seventh lens and the eighth lens are all plastic aspheric lenses; the third lens, the fourth lens, the fifth lens and the sixth lens are all glass spherical lenses.

2. The prime lens according to claim 1,

the fourth lens, the fifth lens and the sixth lens form a triple cemented lens group.

3. The prime lens according to claim 1,

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 concave 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;

the object side surface of the fifth lens is a convex surface;

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

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

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

4. The prime lens according to claim 1, wherein the first lens has an optical power of ψ 1, the second lens has an optical power of ψ 2, the third lens has an optical power of ψ 3, the fourth lens has an optical power of ψ 4, the fifth lens has an optical power of ψ 5, the sixth lens has an optical power of ψ 6, the seventh lens has an optical power of ψ 7, the eighth lens has an optical power of ψ 8, wherein:

-0.12＜ψ1＜-0.08；-0.03＜ψ2＜-0.1；0.08＜ψ3＜0.1；0.03＜ψ4＜0.05；-0.03＜ψ5＜-0.02；-0.01＜ψ6＜0.01；0.01＜ψ7＜0.04；0.03＜ψ8＜0.06。

5. the prime lens according to claim 1, wherein the first lens has a focal length of f1, the second lens has a focal length of f2, the seventh lens has a focal length of f7, the eighth lens has a focal length of f8, and the prime lens has a focal length of f, wherein:

1.8≤|f1/f|≤2.2；8.3≤|f2/f|≤10.2；5.3≤|f7/f|≤15.1；3.5≤|f8/f|≤5.5。

6. the prime lens according to claim 1, wherein the third lens has a focal length of f3, the fourth lens has a focal length of f4, the fifth lens has a focal length of f5, the sixth lens has a focal length of f6, and the prime lens has a focal length of f, wherein:

2≤|f3/f|≤2.5；7.8≤|(f4+f5+f6)/f|≤12.1。

7. the fixed focus lens as claimed in claim 1, wherein a distance from an optical axis center of an image side surface of the eighth lens element to the image plane is BFL, and a distance from an optical axis center of an object side surface of the first lens element to the image plane is TTL, wherein BFL/TTL > 0.17.

8. The prime lens according to claim 1, wherein the first lens has a refractive index nd1, an abbe number vd 1; the refractive index of the second lens is nd2, and the Abbe number is vd 2; the refractive index of the seventh lens is nd7, and the Abbe number is vd 7; the refractive index of the eighth lens is nd8, the Abbe number is vd8, wherein:

1.5<nd1<1.6，55<vd1<95；1.52<nd2<2.1，55<vd2<95；1.62<nd7<1.81，16<vd7<95；1.53<nd8<1.6，55<vd8<95。

9. the prime lens according to claim 1, wherein the refractive index of the third lens is nd3, the abbe number is vd 3; the refractive index of the fourth lens is nd4, and the Abbe number is vd 4; the refractive index of the fifth lens is nd5, and the Abbe number is vd 5; the refractive index of the sixth lens is nd6, the Abbe number is vd6, wherein:

1.78<nd3<2.1，25<vd3<40；1.58<nd4<1.60，48<vd4<90；1.59<nd5<1.86，22<vd5<50；1.58<nd6<1.61，57<vd6<95。

10. the prime lens according to claim 1, further comprising a diaphragm;

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

Images