CN217902159U - Fixed focus lens - Google Patents

Abstract

A fixed focus lens is configured between an amplification side and a reduction side, and comprises a first lens group, an aperture diaphragm and a second lens group. The first lens group is located between the enlargement side and the reduction side and comprises six lenses arranged along an optical axis of the fixed-focus lens. The aperture diaphragm is configured between the first lens group and the second lens group. The second lens group is arranged between the first lens group and the reduction side and includes four lenses arranged along the optical axis, wherein an abbe number of a lens having a positive refractive power in the second lens group falls within a range of 60 to 95. The utility model discloses a tight shot can reach the lightweight design, also more general tight shot more wide angle.

Description

Fixed focus lens

Technical Field

The present invention relates to a fixed focus lens, and more particularly to a wide-angle fixed focus lens for a projection apparatus.

Background

The development of the projection apparatus towards miniaturization and light weight is one of the development trends in the market today. Therefore, manufacturers focus on designing a suitable and light lens structure and effectively reduce the production cost. In comprehensive consideration, the projection lens design is mainly based on a fixed focus lens.

However, the focal length of the fixed focus lens is too long, which results in a projection angle not wide enough, and the size of the projected image is easily limited due to insufficient space. When a large-size image is projected in a limited projection distance, a special wide-angle lens is required to shorten the imaging distance, however, the aberration derived from the wide-angle lens is a difficult problem that the lens designer must overcome.

The background section is only provided to aid in understanding the present invention, and therefore the disclosure in the background section may include some known techniques which do not constitute a part of the knowledge of those skilled in the art. The disclosure in the "background" section does not represent that content or the problems which may be solved by one or more embodiments of the present invention are known or appreciated by those skilled in the art prior to the filing of the present application.

SUMMERY OF THE UTILITY MODEL

The utility model provides a fixed focus camera lens can reach the lightweight design, also more the wide angle than general fixed focus camera lens.

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

In order to achieve one or a part of or all of the above or other objectives, an embodiment of the present invention provides a fixed focus lens. The fixed focus lens is configured between the amplification side and the reduction side, and comprises a first lens group, an aperture diaphragm and a second lens group. The first lens group is positioned between the enlargement side and the reduction side and comprises six lenses arranged along an optical axis of the fixed-focus lens. The aperture diaphragm is configured between the first lens group and the second lens group. The second lens group is arranged between the first lens group and the reduction side and comprises four lenses arranged along the optical axis, wherein the Abbe number of the lens with positive diopter in the second lens group is in a range of 60 to 95.

Based on the above, the embodiments of the present invention have at least one of the following advantages or effects. The utility model discloses an among the tight shot, including first lens crowd and second lens crowd to and set up the aperture diaphragm between first lens crowd and second lens crowd. The first lens group comprises six lenses arranged along the optical axis of the fixed-focus lens. The abbe number of the lens of the second lens group having a positive refractive power falls within a range of 60 to 95. Compared with the known lens, the fixed-focus lens of the utility model has simple structure and is suitable for mass production; the whole length of the fixed-focus lens is shortened, so that the volume of the system device can be reduced, and the fixed-focus lens is wider than a common fixed-focus lens; when the method is used for high-frequency analysis projection, the situation of poor analysis can be improved.

In order to make the aforementioned and other features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Drawings

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

Fig. 2 is a modulation transfer function graph of the fixed focus lens of fig. 1.

Fig. 3 is a graph of an out-of-focus modulation transfer function of the fixed-focus lens of fig. 1.

Fig. 4A to 4D are graphs of astigmatic field curvatures and distortions of the fixed-focus lens of fig. 1 for respective reference wavelengths.

Fig. 5A to 5C are lateral beam fan diagrams of the prime lens of fig. 1 for each reference wavelength.

Fig. 6A and 6B are a longitudinal chromatic aberration diagram and a lateral chromatic aberration diagram of the fixed-focus lens of fig. 1.

Fig. 7A to 7C are dot charts of the fixed focus lens of fig. 1 for a reference wavelength of 615 nm.

Fig. 8A to 8C are dot charts of the fixed-focus lens of fig. 1 for a reference wavelength of 525 nm.

Fig. 9A to 9C are dot charts of the fixed-focus lens of fig. 1 for a reference wavelength of 460 nm.

Detailed Description

The foregoing and other technical and other features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings. Directional terms as referred to in the following examples, for example: up, down, left, right, front or rear, etc., are simply directions with reference to the drawings. Accordingly, the directional terminology is used for purposes of illustration and is in no way limiting.

Fig. 1 is a schematic view of a fixed focus lens according to an embodiment of the present invention, please refer to fig. 1. The fixed-focus lens 100 of the present embodiment is disposed between the enlargement side AL and the reduction side AS, the fixed-focus lens 100 includes a first lens group G1, an aperture stop ST, and a second lens group G2, and the fixed-focus lens 100 has an optical axis OA. The first lens group G1 is located between the enlargement side AL and the reduction side AS, and includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a sixth lens L6 arranged in sequence along the optical axis OA. The aperture stop ST is disposed between the first lens group G1 and the second lens group G2. The second lens group G2 is disposed between the first lens group G1 and the reduction side AS, and includes a seventh lens L7, an eighth lens L8, a ninth lens L9, and a tenth lens L10 arranged in order along the optical axis OA, wherein an abbe number of a lens having a positive refractive power in the second lens group G2 falls within a range of 60 to 95. In addition, the fixed focus lens 100 of the present embodiment can be disposed between a coupling element 200 and the enlargement side AL, and an imaging element 300 can be disposed between the coupling element 200 and the reduction side AS, the coupling element 200 being between the imaging element 300 and the fixed focus lens 100 on the optical axis OA.

The imaging element 300 has an image end facing the amplification side AL, the imaging element 300 is used for generating an image beam, and it is a reflective light modulator such as a Digital Micromirror Device (DMD) or a Liquid Crystal On Silicon (LCOS), the number of the imaging elements 300 can be one or more (e.g. 3), the invention is not limited to the number and kinds of the imaging elements 300. The coupling element 200 may include, for example, a known reflector, an X-prism, a total internal reflection prism (TIR prism), or a glass sheet, and the coupling element 200 is used to guide an illumination beam from an illumination light source (not shown) to the imaging element 300, the imaging element 300 converts the illumination beam into an image beam, the coupling element 200 transmits the image beam to the focusing lens 100, and the glass sheet may be used to protect the imaging element 300 from dust, which is not limited to this.

In the fixed focus lens 100, the first lens group G1 includes six lenses L1 to L6 sequentially arranged on the optical axis OA from the enlargement side AL to the reduction side AS, wherein the first lens L1 and the second lens L2 are aspheric lenses. And diopters of the six lenses L1 to L6 of the first lens group G1 are negative, positive, negative, and positive in order from the enlargement side AL to the reduction side AS. As will be described in detail below.

The first lens L1 has a negative refractive power. The material of the first lens L1 may be glass or plastic, but the present invention is not limited thereto. A surface 11 of the first lens L1 facing the magnification side AL is a convex surface facing the magnification side AL. A surface 12 of the first lens L1 facing the reduction side AS is a concave surface facing the aperture stop ST (or facing the reduction side AS). That is, the first lens L1 is a convex-concave lens. In the present embodiment, both the surface 11 of the first lens L1 facing the enlargement side AL and the surface 12 facing the reduction side AS are aspheric surfaces (aspheric surfaces).

The second lens L2 has a negative refractive power. The material of the second lens L2 may be glass or plastic, but the invention is not limited thereto. A surface 21 of the second lens L2 facing the magnification side AL is a convex surface facing the magnification side AL. The surface 22 of the second lens L2 facing the reduction side AS is a concave surface facing the aperture stop ST (or facing the reduction side AS). That is, the second lens L2 is a convex-concave lens. In the present embodiment, both the surface 21 of the second lens L2 facing the enlargement side AL and the surface 22 facing the reduction side AS are aspheric surfaces (aspheric surfaces).

The third lens L3 has a negative refractive power. The third lens element L3 may be made of glass or plastic, but the invention is not limited thereto. A surface 31 of the third lens L3 facing the enlargement side AL is a concave surface facing the enlargement side AL. A surface 32 of the third lens L3 facing the reduction side AS is a concave surface facing the aperture stop ST (or facing the reduction side AS). That is, the third lens L3 is a double concave lens.

The fourth lens L4 has a positive refractive power. The material of the fourth lens element L4 may be glass or plastic, but the present invention is not limited thereto. It should be noted that the surface of the fourth lens L4 facing the enlargement side AL is convex and can be bonded to the surface 32 of the third lens L3 facing the reduction side AS, and the surface 42 of the fourth lens L4 facing the reduction side AS is convex toward the aperture stop ST (or toward the reduction side AS). That is, the fourth lens L4 is a biconvex lens, and the third lens L3 and the fourth lens L4 may form a cemented doublet lens. Thereby, the adverse effect of chromatic aberration of the fixed-focus lens 100 due to chromatic dispersion can be offset. The third lens L3 and the fourth lens L4 may be bonded by an optical transparent adhesive, but the present invention is not limited thereto.

The fifth lens L5 has a negative refractive power. The material of the fifth lens element L5 may be glass or plastic, but the invention is not limited thereto. A surface 51 of the fifth lens L5 facing the magnification side AL is a concave surface facing the magnification side AL. A surface 52 of the fifth lens L5 facing the reduction side AS is a concave surface facing the aperture stop ST (or facing the reduction side AS). That is, the fifth lens L5 is a double concave lens.

The sixth lens L6 has a positive refractive power. The material of the sixth lens element L6 may be glass or plastic, but the invention is not limited thereto. It should be noted that the surface of the sixth lens L6 facing the enlargement side AL is convex and can be bonded to the surface 52 of the fifth lens L5 facing the reduction side AS, and the surface 62 of the sixth lens L6 facing the reduction side AS is convex toward the aperture stop ST (or toward the reduction side AS). That is, the sixth lens L6 is a biconvex lens, and the fifth lens L5 and the sixth lens L6 may form a cemented doublet lens. Thereby, the adverse effect of chromatic aberration of the fixed-focus lens 100 due to chromatic dispersion can be offset. The fifth lens element L5 and the sixth lens element L6 may be bonded by an optical transparent adhesive, but the present invention is not limited thereto.

In summary, in the present embodiment, at least two lenses (e.g., the first lens L1 and the second lens L2) of the six lenses L1 to L6 of the first lens group G1 are aspheric lenses. And, of the six lenses L1 to L6, at least one cemented doublet is formed. The third lens L3 and the fourth lens L4 may form a double cemented lens, or the fifth lens L5 and the sixth lens L6 may form a double cemented lens, or the third lens L3 and the fourth lens L4 may form a double cemented lens, and the fifth lens L5 and the sixth lens L6 form another double cemented lens. The present invention is not limited thereto.

Please continue to refer to fig. 1. On the other hand, in the fixed focus lens 100, the second lens group G2 includes four lenses L7 to L10 arranged in order on the optical axis OA from the enlargement side AL to the reduction side AS, wherein the tenth lens L10 is an aspheric lens, and the seventh lens L7, the eighth lens L8, and the ninth lens L9 form a cemented triplet. Diopters of the four lenses L7 to L10 of the second lens group G2 are positive, negative, positive, and positive in order from the enlargement side AL to the reduction side AS. As will be described in detail below.

The seventh lens L7 has a positive refractive power. The seventh lens element L7 may be made of glass or plastic, but the invention is not limited thereto. A surface 71 of the seventh lens L7 facing the enlargement side AL is a convex surface facing the enlargement side AL (or facing the aperture stop ST). A surface 72 of the seventh lens L7 facing the reduction side AS is a convex surface facing the reduction side AS. That is, the seventh lens L7 is a biconvex lens.

The eighth lens L8 has a negative refractive power, and the ninth lens L9 has a positive refractive power. The eighth lens element L8 and the ninth lens element L9 may be made of glass or plastic, but the present invention is not limited thereto. It is to be noted that the surface of the eighth lens L8 facing the enlargement side AL is concave and can be attached to the surface 72 of the seventh lens L7 facing the reduction side AS; the surface 82 of the eighth lens L8 facing the reduction side AS is a concave surface facing the reduction side AS and may be cemented with a convex surface of the ninth lens L9 facing the enlargement side AL (or facing the aperture stop ST), and the surface 92 of the ninth lens L9 facing the reduction side AS is a convex surface facing the reduction side AS. That is, the eighth lens L8 is a biconcave lens, and the ninth lens L9 is a biconvex lens. And the seventh lens L7, the eighth lens L8, and the ninth lens L9 may form a set of cemented triplet lenses. Thereby further offsetting the adverse effect of chromatic aberration of the fixed focus lens 100 caused by chromatic dispersion. The seventh lens element L7, the eighth lens element L8, and the ninth lens element L9 may be bonded by an optical transparent adhesive, which is not limited in the present invention.

The tenth lens L10 has a positive refractive power. The tenth lens element L10 may be made of glass or plastic, but the invention is not limited thereto. A surface 101 of the tenth lens L10 facing the enlargement side AL is a convex surface facing the enlargement side AL (or facing the aperture stop ST). A surface 102 of the tenth lens L10 facing the reduction side AS is a convex surface facing the reduction side AS. That is, the tenth lens L10 is a biconvex lens. In the present embodiment, both the surface 101 of the tenth lens L10 facing the enlargement side AL and the surface 102 facing the reduction side AS are aspheric surfaces (aspheric surfaces).

In summary, in the present embodiment, at least two of the four lenses L7 to L10 of the second lens group G2 have positive refractive power, such as the seventh lens L7 and the ninth lens L9. And among the ten lenses L1 to L10 of the fixed focus lens 100, at least two cemented lenses are formed, for example, the third lens L3 and the fourth lens L4 form a double cemented lens, and the seventh lens L7, the eighth lens L8, and the ninth lens L9 form a triple cemented lens. However, the present invention is not limited thereto.

Other detailed optical data are shown in the following table, wherein the fixed focus lens 100 of the above embodiment is designed such that the effective focal length falls within the range of 1.0 mm to 4.0 mm. The first lens group G1 has negative diopter, and the second lens group G2 has positive diopter. The Numerical aperture value (NA) of the reduction side AS of the fixed-focus lens 100 at the image end of the imaging element 300 falls within a range of 0.208 to 0.294. The field angle of the fixed focus lens 100 on the magnification side AL is greater than 100 degrees. Therefore, the fixed focus lens 100 of the present embodiment can meet the requirement of wide viewing angle.

It should be noted that the radius of curvature of the surface 11 of the first lens L1 shown in table one refers to the radius of curvature of the surface 11 of the first lens L1 toward the enlargement side AL in the optical axis OA region, the radius of curvature of the surface 12 of the first lens L1 refers to the radius of curvature of the surface 12 of the first lens L1 toward the reduction side AS in the optical axis OA region, and so on. The pitch of the surface 11 (2.50 mm as shown in table one) refers to the distance between the surface 11 and the next surface (surface 12 in this example) on the optical axis OA, i.e. the thickness of the first lens L1 on the optical axis OA is 2.50mm. The pitch of the surfaces 12 (4.70 mm AS shown in table one) means a pitch of the surface 12 of the first lens L1 facing the reduction side AS and the surface 21 of the second lens L2 facing the enlargement side AL on the optical axis OA, that is, a pitch of the first lens L1 and the second lens L2 on the optical axis OA is 4.70mm. The pitch of the surface 62 (0.20 mm AS shown in table one) means that the distance between the surface 62 of the sixth lens L6 facing the reduction side AS and the stop ST on the optical axis is 0.20mm. The pitch of the surface of the diaphragm ST (2.60 mm as shown in table one) means that the diaphragm ST and the seventh lens L7 are spaced apart by 2.60mm on the optical axis OA, and so on. In addition, as can be seen from table i, the seventh lens L7, the ninth lens L9 and the tenth lens L10 in the second lens group G2 are lenses having positive refractive power and an abbe number falling within a range of 60 to 95.

Table one:

it should be noted that, in the fixed focus lens 100 of the present embodiment, the following 3 line-column types are satisfied:

the prime lens 100 meets 20< | f1/f | <30;

the prime lens 100 satisfies 3.0< | f2/f | <4.0; and

the prime lens 100 satisfies 0.1< | f/H | 1.0.

Wherein, the first and the second end of the pipe are connected with each other,

f is the effective focal length of the fixed focus lens 100;

f1 is the effective focal length of the first lens group G1;

f2 is the effective focal length of the second lens group G2; and

h is the image height of the fixed focus lens 100 on the reduction side AS.

In the present embodiment, the surfaces 11, 21, 101 facing the enlargement side and the surfaces 12, 22, 102 facing the reduction side are all aspheric surfaces in total of six, and these aspheric surfaces are defined by the following formulas:

y is the distance between a point on the aspheric curve and the optical axis;

z is the depth of the aspheric surface, namely the vertical distance between a point on the aspheric surface, which is Y away from the optical axis, and a tangent plane tangent to the vertex on the aspheric surface optical axis;

r is the radius of curvature of the lens surface;

k is the cone coefficient;

a2i is the 2 i-th order aspheric coefficient.

The aspheric coefficients of the aspheric surfaces in formula (1) in this embodiment are shown in table two below. In the second table, the column number 11 indicates the aspheric coefficient of the surface 11 of the first lens L1 facing the enlargement side AL, the column number 12 indicates the aspheric coefficient of the surface 12 of the first lens L1 facing the reduction side AS, and so on. In the present embodiment, the 2 nd order aspherical surface coefficient a of each aspherical surface ₂ Are all zero and are not listed in the table.

A second table:

surface of

K

a 4

a 6

a 8

a 10

a 12

a 14

a 16

11

0.00

7.391E-05

8.471E-07

-1.555E-08

1.159E-10

-4.036E-13

5.188E-16

2.695E-19

12

-0.63

-3.726E-04

7.593E-06

4.408E-08

-6.665E-09

1.082E-10

-6.906E-13

1.811E-15

21

0.00

1.240E-03

-3.500E-05

-9.421E-08

1.393E-08

-1.442E-10

-4.249E-13

9.487E-15

22

0.00

2.321E-03

-3.445E-05

-1.444E-06

2.043E-08

5.608E-09

-2.378E-10

3.037E-12

101

-3.90

-3.602E-05

2.197E-06

-8.344E-07

6.633E-08

-2.154E-09

2.121E-11

0.000E+00

102

-0.37

1.198E-04

-1.251E-06

-3.971E-07

1.887E-08

8.795E-11

-1.678E-11

0.000E+00

Fig. 2 is a modulation transfer function graph of the fixed-focus lens of fig. 1. Fig. 3 is a graph of an out-of-focus modulation transfer function of the fixed-focus lens of fig. 1. In the figure, the solid line (denoted by T) represents the meridian plane, and the broken line (denoted by S) represents the sagittal plane. The corresponding numbers represent different field heights (in mm). Fig. 2 and fig. 3 illustrate that the fixed-focus lens 100 of the present embodiment still has good contrast at the spatial frequency response 93 (cycles/mm). The description shows that the fixed focus lens 100 of the present embodiment can effectively improve the situation of poor analysis when used for high-frequency analysis projection.

Fig. 4A to 4D are graphs of astigmatic field curvatures and distortions of the fixed-focus lens of fig. 1 for respective reference wavelengths. Fig. 4A, 4B and 4C respectively correspond to Field Curvature (Field Curvature) Aberration in the Sagittal (Sagittal) direction (labeled S) and Field Curvature Aberration in the Tangential (Tangential) direction (labeled T) at the reference wavelengths 615 nm, 525 nm and 460 nm of the fixed-focus lens 100 of the present embodiment, and fig. 4D illustrates Distortion Aberration (Distortion Aberration) of the fixed-focus lens 100 of the present embodiment at the reference wavelengths 615 nm, 525 nm and 460 nm. As can be seen from fig. 4A to fig. 4C, the curvature of field aberration of the fixed focus lens 100 of the present embodiment falls within ± 0.03 mm, which indicates that the fixed focus lens 100 of the present embodiment can effectively eliminate the aberration. Fig. 4D shows that the distortion aberration is maintained within ± 2%, which illustrates that the distortion aberration of the fixed-focus lens 100 of the present embodiment has the requirement of image quality and can provide good image quality.

Fig. 5A to 5C are lateral beam fan diagrams of the prime lens of fig. 1 for each reference wavelength. A transverse ray fan plot (transverse ray fan plot) of the fixed focus lens 100 of the present embodiment at different image heights is illustrated, which is a simulation data plot made of light with wavelengths of 615 nm, 525 nm, and 460 nm. It can be seen from the figure that the integrated error control of the fixed focus lens 100 of the present embodiment is in a good range.

Fig. 6A and 6B are a longitudinal chromatic aberration diagram and a lateral chromatic aberration diagram of the fixed-focus lens of fig. 1. Fig. 6A illustrates Longitudinal Chromatic Aberration (Longitudinal Chromatic Aberration) of the fixed-focus lens 100 of the present embodiment at reference wavelengths 615 nm, 525 nm and 460 nm, and fig. 6B illustrates Lateral Chromatic Aberration (transverse Chromatic Aberration) of the fixed-focus lens 100 of the present embodiment at reference wavelengths 615 nm, 525 nm and 460 nm. It can be seen from the figure that the chromatic aberration of the fixed-focus lens 100 of the present embodiment is small between different wavelengths, so that the chromatic aberration is well shown.

Fig. 7A to 7C are dot charts of the fixed focus lens of fig. 1 for a reference wavelength of 615 nm. Fig. 8A to 8C are dot charts of the fixed-focus lens of fig. 1 for a reference wavelength of 525 nm. Fig. 9A to 9C are dot charts of the fixed-focus lens of fig. 1 for a reference wavelength of 460 nm. As can be seen from the above dot charts, the fixed-focus lens 100 of the present embodiment has a controllable aberration in a controllable range for the diffuse spots formed on different imaging planes for each reference wavelength.

Based on the above, the embodiments of the present invention have at least one of the following advantages or effects. The utility model discloses an among the tight shot, including first lens crowd and second lens crowd to and set up the diaphragm between first lens crowd and second lens crowd. The first lens group comprises six lenses arranged along the optical axis of the fixed-focus lens. The abbe number of the lens of the second lens group having a positive refractive power falls within a range of 60 to 95. Compared with the known lens, the fixed-focus lens of the utility model has simple structure and is suitable for mass production; the whole length of the fixed focus lens is shortened, so that the volume of the system device can be reduced, and the fixed focus lens is wider than a common fixed focus lens; when the method is used for high-frequency analysis projection, the situation of poor analysis can be improved.

However, the above description is only a preferred embodiment of the present invention, and the scope of the present invention should not be limited thereby, and all the simple equivalent changes and modifications made according to the claims and the contents of the present invention are still included in the scope of the present invention. Moreover, it is not necessary for any embodiment or claim of the invention to address or to achieve all of the objects, advantages, or features disclosed herein. In addition, the abstract and the title (the title of the utility model) are used for assisting the retrieval of patent documents and are not intended to limit the scope of the present invention. Furthermore, the terms "first", "second", and the like in the description or the claims are used only for naming elements (elements) or distinguishing different embodiments or ranges, and are not used for limiting the upper limit or the lower limit on the number of elements.

Description of reference numerals:

100: fixed focus lens

200: coupling element

300: imaging element

AL: side of enlargement

AS: reduction side

G1: a first lens group

G2: the second lens group

L1: first lens

L2: second lens

L3: third lens

L4: fourth lens

L5: fifth lens element

L6: sixth lens element

L7: seventh lens element

L8: eighth lens element

L9: ninth lens

L10: tenth lens

ST: and (4) an aperture diaphragm.

Claims (17)

1. A fixed focus lens configured between an enlargement side and a reduction side, the fixed focus lens comprising a first lens group, an aperture stop, and a second lens group, wherein:

the first lens group is arranged between the enlargement side and the reduction side, and includes six lenses arranged along an optical axis of the fixed-focus lens;

the aperture diaphragm is configured between the first lens group and the second lens group; and

the second lens group is disposed between the first lens group and the reduction side, and includes four lenses arranged along the optical axis, wherein an abbe number of a lens having a positive refractive power in the second lens group falls within a range of 60 to 95.

2. The prime lens according to claim 1, wherein the diopter of the six lenses of the first lens group is negative, positive, negative and positive in order from the magnifying side to the reducing side.

3. The fixed-focus lens according to claim 1, wherein the fixed-focus lens conforms to 20< | f1/f | <30, where f1 is an effective focal length of the first lens group, and f is an effective focal length of the fixed-focus lens.

4. The prime lens according to claim 1, wherein an effective focal length of the prime lens falls within a range of 1.0 mm to 4.0 mm.

5. The prime lens according to claim 1, wherein the first lens group has a negative refractive power and the second lens group has a positive refractive power.

6. The prime lens according to claim 1, wherein at least two of the six lenses of the first lens group are aspheric lenses.

7. The prime lens according to claim 1, wherein at least one cemented lens is formed among the six lenses of the first lens group.

8. The prime lens according to claim 1, wherein the diopters of the four lenses of the second lens group are positive, negative, positive and positive in order from the magnification side to the reduction side.

9. The prime lens according to claim 1, wherein at least two of the four lenses of the second lens group have a positive refractive power.

10. The fixed-focus lens according to claim 1, wherein the fixed-focus lens conforms to 3.0< | f2/f | <4.0, where f2 is an effective focal length of the second lens group, and f is the effective focal length of the fixed-focus lens.

11. The fixed-focus lens according to claim 1, wherein the fixed-focus lens conforms to 0.1< | f/H | <1.0, where f is an effective focal length of the fixed-focus lens, and H is an image height of the fixed-focus lens on the reduction side.

12. The prime lens according to claim 1, wherein at least two cemented lenses are formed among ten lenses of the prime lens.

13. The prime lens according to claim 1, wherein a numerical aperture value of the reduction-side image end of the prime lens falls within a range of 0.208 to 0.294.

14. The fixed focus lens according to claim 1, wherein a field angle of the fixed focus lens on the magnification side is larger than 100 degrees.

15. The prime lens according to claim 1, wherein the first lens group comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens arranged in sequence from the magnification side to the reduction side, wherein the first lens and the second lens are aspheric lenses.

16. The prime lens according to claim 15, wherein the third lens and the fourth lens form a doublet, and the fifth lens and the sixth lens form another doublet.

17. The prime lens according to claim 1, wherein the second lens group comprises a seventh lens, an eighth lens, a ninth lens and a tenth lens arranged in sequence from the magnification side to the reduction side, wherein the tenth lens is an aspheric lens, and the seventh lens, the eighth lens and the ninth lens form a cemented lens.

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