Wide-angle prime lens

Abstract

The utility model discloses a wide-angle prime lens, which is suitable for a single electric camera and comprises three lens groups. The first lens group with the positive focal power comprises two meniscus negative lenses, a biconvex spherical positive lens, a first doublet lens and a biconvex spherical positive lens. And the second lens group with negative focal power comprises a biconcave spherical negative lens and a biconvex spherical positive lens, and can move during focusing. And the third lens group with positive focal power comprises a biconvex spherical positive lens, a second doublet lens, a third doublet lens, a biconcave spherical negative lens and a biconvex aspheric positive lens. The first doublet lens and the third doublet lens are basically symmetrical optically. The highest order of an even term of an aspheric expression of the wide-angle prime lens is 10.

Description

TECHNICAL FIELD

[0001] The utility model belongs to photographic lens technical field, concretely relates to wide-angle fixed focus lens for single electric camera. BACKGROUND

[0002] Single electric camera (micro single camera) is the current popular non-professional digital camera, and is configured with full-frame or half-frame (for example, APS-C specification) photosensitive element, and can replace the lens. The selling price of high imaging quality lens is high, and the automatic focusing power consumption is large.

[0003] There are multiple patents of wide-angle lens, and only one or two lenses are moved during focusing, so that the focusing is fast and the power consumption is low. In the patent CN112346229A, three aspheric lenses are adopted, and the highest order of even terms of aspheric surface expression (even polynomial) is 10. In the patents CN110045484A and CN115840281A, one aspheric lens is adopted, and the highest order of even terms of aspheric surface expression is 12. UTILITY MODEL CONTENTS

[0004] The technical problem to be solved by the utility model is how to improve the fixed focus lens to adapt to the single electric camera.

[0005] The utility model discloses a wide-angle fixed focus lens.

[0006] The wide-angle fixed focus lens comprises a first lens group of positive refractive power, a second lens group of negative refractive power and a third lens group of positive refractive power which are sequentially distributed along the direction of the central axis, and further comprises an aperture stop, and when focusing from the infinite distance to the close distance object, the first lens group, the aperture stop and the third lens group are fixed relative to the image surface, and the second lens group moves along the central axis to the image surface.

[0007] The first lens group comprises the following sequentially distributed along the direction of the central axis:

[0008] The first lens is configured as a negative lens, the object side surface is a spherical convex surface, and the image side surface is a spherical concave surface.

[0009] The second lens is configured as a negative lens, the object side surface is a spherical convex surface, and the image side surface is a spherical concave surface.

[0010] The third lens is configured as a double-convex spherical positive lens.

[0011] The fourth lens is configured as a double-concave spherical negative lens, the refractive index is 1.80-1.90, and the Abbe number is 21.0-26.0.

[0012] The fifth lens is configured as a double-convex spherical positive lens, the refractive index is 1.75-1.85, the Abbe number is 44.0-49.0, and the fifth lens and the fourth lens are glued to form a first double-glued lens.

[0013] The sixth lens is configured as a biconvex spherical positive lens.

[0014] The second lens group comprises, in sequence along the central axis direction:

[0015] The seventh lens is configured as a biconcave spherical negative lens.

[0016] The eighth lens is configured as a biconvex spherical positive lens.

[0017] The third lens group comprises, in sequence along the central axis direction:

[0018] The ninth lens is configured as a biconvex spherical positive lens.

[0019] The tenth lens is configured as a biconvex spherical positive lens.

[0020] The eleventh lens is configured as a biconcave spherical negative lens, and the eleventh lens and the tenth lens are glued to form a second double-glued lens.

[0021] The twelfth lens is configured as a biconvex spherical positive lens, and the twelfth lens and the fifth lens have consistent refractive indexes and Abbe numbers.

[0022] The thirteenth lens is configured as a biconcave spherical negative lens, and the thirteenth lens and the fourth lens have consistent refractive indexes and Abbe numbers, and the thirteenth lens and the twelfth lens are glued to form a third double-glued lens.

[0023] The fourteenth lens is configured as a biconcave spherical negative lens, and the fourteenth lens and the fourth lens have consistent refractive indexes and Abbe numbers.

[0024] The fifteenth lens is configured as a biconvex aspheric positive lens, and the highest order of even terms of aspheric surface expressions of an object side surface and an image side surface is 10.

[0025] In some embodiments of the utility model, the total focal length of the wide-angle fixed focus lens is 20-30 mm. Further, the seventh lens has a curvature radius of -82 mm on the object side surface, a curvature radius of +28 mm on the image side surface, a refractive index of 1.67-1.77, and an Abbe number of 35.5-40.5; the eighth lens has a curvature radius of +353 mm on the object side surface, a curvature radius of -83 mm on the image side surface, a refractive index of 1.90-2.00, and an Abbe number of 18.5-23.5.

[0026] The technical scheme of the utility model is implemented, and the following beneficial effects can be obtained.

[0027] The utility model discloses a wide-angle fixed focus lens suitable for single electric camera, comprising three lens groups. The first lens group of positive refractive power includes two pieces of meniscus negative lens, a piece of double convex spherical positive lens, first double cemented lens and a piece of double convex spherical positive lens. The second lens group of negative refractive power includes a piece of double concave spherical negative lens and a piece of double convex spherical positive lens, and can be moved when focusing. The third lens group of positive refractive power includes a piece of double convex spherical positive lens, second double cemented lens, third double cemented lens, a piece of double concave spherical negative lens and a piece of double convex aspherical positive lens. The first and third double cemented lenses are basically symmetrical in optics. The highest order of even term of aspherical surface expression of the wide-angle fixed focus lens is 10. BRIEF DESCRIPTION OF DRAWINGS

[0028] The following drawings should be used in conjunction with the detailed description section.

[0029] Figure 1 It is the central axis sectional view of wide-angle fixed focus lens in example one, and the figure notes represent respectively: IMG - image plane, FIT - filter protector, STO - aperture stop, Z1 - central axis, T1 - moving range, REF - reference starting surface.

[0030] Figure 2 It is the optical path diagram when focusing on infinity of wide-angle fixed focus lens in example one.

[0031] Figure 3a And Figure 3b It is the spherical aberration diagram and the sagittal chromatic aberration diagram of wide-angle fixed focus lens calculated by ZEMAX software in example one, and the calculation conditions are: incident light mixing range 430~658nm, incident pupil radius 8.7471mm, aperture F / 1.4, near distance focusing state.

[0032] Figure 4a And Figure 4b It is two modulation transfer function (MTF) curve diagrams of wide-angle fixed focus lens calculated by ZEMAX software in example one, and the calculation conditions are as above. DETAILED DESCRIPTION

[0033] The following describes the embodiments in conjunction with the drawings.

[0034] In the specification, unless specifically stated, one embodiment, some embodiments and other embodiments are used to distinguish different embodiments, and do not mean all embodiments; The directions / positions of top, bottom, center, edge, inside, outside, far, near, long, wide, vertical, horizontal, upper, lower, front, back, left, right, etc. are observed based on the observation angle of the drawings, and cannot be understood as that the components / devices are located at a specific position and face a specific direction.

[0035] The lens grouping manner in the present specification is only for the convenience of describing the embodiments. It can be understood that other grouping manners can be adopted in optical design analysis, lens shaping and lens assembly.

[0036] A positive lens and a positive focal power both mean that the image-side focal length of the optical system is positive, which can converge a parallel incident light beam. A negative lens and a negative focal power both mean that the image-side focal length of the optical system is negative, which can diverge a parallel incident light beam. The light-transmitting surface of a lens can be simply referred to as a "surface", the side surface of the lens facing the object to be photographed is referred to as the "object-side surface", and the side surface of the lens facing the light-sensitive surface of the camera is referred to as the "image-side surface".

[0037] An aperture stop can be simply referred to as a "stop", and the plane where the stop is located is sequentially numbered together with the light-transmitting surface of the lens.

[0038] Embodiment I

[0039] A wide-angle fixed-focus lens is disclosed.

[0040] The wide-angle fixed-focus lens has a focal length of 23 mm, is adapted to a maximum aperture F / 1.4, and has an ASP-C specification imaging surface.

[0041] Please refer to Figure 1 and Figure 2 . Figure 1 In the drawings, the lens barrel is not drawn, the central axis Z1 (also referred to as the optical axis, the main axis, or the principal optical axis) points from left to right to the image surface IMG, and a filter protector FIT is arranged in front of the image surface IMG.

[0042] The lens data and positional relationship of the wide-angle fixed-focus lens are listed in Table 1 below, the aspherical surface expression f1, and Table 2 recording the aspherical surface expression coefficients,

[0043]

[0044]

[0045] In Table 1, the object-side surface of the first lens L1 is represented as surface S1, other light-transmitting surfaces (including the plane where the aperture stop STO is located, and the lens cementing surface) are sequentially numbered in ascending order along the central axis Z1, and the image-side surface of the fifteenth lens L15 is represented as surface S28. The "radius of curvature R" represents the on-axis radius of curvature value of the vertex of a surface. The lens located between the ith surface S i and the (i+1)th surface S i+1 has a "thickness" of the central axis thickness, a "refractive index Nd", and an "Abbe number Nd" of the d-line measurement value. The distance between the image-side surface of the former lens and the object-side surface of the latter lens in two adjacent lenses on the central axis Z1 is referred to as the central axis distance between the two lenses.

[0046] The 15 lenses of the wide-angle fixed lens are numbered in ascending order along the central axis, are all glass lenses, and can be divided into three groups. In the lens barrel (not shown) of the wide-angle fixed lens, a first lens group G1, a second lens group G2, an aperture stop STO, and a third lens group G3 are arranged in order along the central axis Z1 from the object side to the image side. Figure 1

[0047] In the focusing process of the wide-angle fixed lens, only the second lens group G2 can be driven by a stepping motor to move along the central axis Z1 back and forth, and the first lens group G1, the aperture stop STO, and the third lens group G3 are all fixed relative to the position of the image plane IMG. The central axis distance between the aperture stop STO and the surface S17 of the third lens group G1 is about 1.5 mm, and the central axis distance between the image plane IMG and the surface S21 of the third lens group G3 is about 15.0 mm.

[0048] The first lens group G1 has positive refractive power and is composed of six glass lenses, including two pieces of meniscus negative lenses, one piece of double convex spherical positive lens, first double cemented lens, and one piece of double convex spherical positive lens. The six glass lenses are arranged in order along the central axis Z1 as the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6. The fourth lens L4 and the fifth lens L5 form the first double cemented lens.

[0049] The second lens group G2 has negative refractive power and is composed of two glass lenses, which can move along the central axis during focusing. The two glass lenses are arranged in order along the central axis Z1 as the seventh lens L7 and the eighth lens L8. The seventh lens L7 is a double concave spherical negative lens. The eighth lens L8 is a double convex spherical positive lens, and its object side surface is close to a plane.

[0050] The third lens group G3 has positive refractive power and is composed of seven glass lenses, including one piece of double convex spherical positive lens, second double cemented lens, third double cemented lens, one piece of double concave spherical negative lens, and one piece of double convex aspherical positive lens. The seven glass lenses are arranged in order along the central axis Z1 as the ninth lens L9, the tenth lens L10, the eleventh lens L11, the twelfth lens L12, the thirteenth lens L13, the fourteenth lens L14, and the fifteenth lens L15. In the second double cemented lens formed by the tenth lens L10 and the eleventh lens L19, the object side surface is a convex spherical surface, the image side surface is a concave spherical surface, and the cemented surface is close to a plane with a negative curvature radius. The twelfth lens L12 and the thirteenth lens L13 form the third double cemented lens.

[0051] ​The third double cemented lens is substantially symmetrical to the first double cemented lens. In the first double cemented lens, the object side is a concave spherical surface, the image side is a convex spherical surface, and the curvature radius of the cemented surface is positive. In the third double cemented lens, the object side is a convex spherical surface, the image side is a concave spherical surface, and the curvature radius of the cemented surface is negative. The fourth lens L4, the thirteenth lens L13 and the fourteenth lens L14 are all concave lenses and adopt the same brand of optical glass. The fifth lens L5 and the twelfth lens L12 are both convex lenses and adopt the same brand of optical glass.

[0052] All the 15 glass lenses are sequentially arranged along the central axis Z1 to form the above three lens groups and are installed in the lens barrel. The lens barrel is provided with a stepping motor and a power supply interface.

[0053] Figure 1 The object side boundary of the second lens group G2 in the moving range T1 is about 6.8 mm away from the central axis of the aperture stop STO. At this time, the wide-angle fixed focus lens is in a state of focusing on an infinite distance, and the optical path diagram is shown in FIG. 2. Figure 2 When the wide-angle fixed focus lens focuses on a close-range object, the second lens group G2 moves along the central axis to the image side IMG and does not exceed the image side boundary of the moving range T1. Because only two lenses are moved, the focusing power consumption of the wide-angle fixed focus lens is low, and the power consumption of the camera can be reduced.

[0054] The specific focal length of each glass lens, the three pairs of double cemented lenses and the three lens groups of the wide-angle fixed focus lens can be calculated using the data in Table 1 and Table 2. The details of each lens are as follows.

[0055] The first lens L1 is configured as a negative lens, the object side is a spherical convex surface with a curvature radius of +52.816 mm, the image side is a spherical concave surface with a curvature radius of +17.784 mm, the central axis thickness is 1.200 mm, the refractive index is 1.49, and the Abbe number is 70.4.

[0056] The second lens L2 is configured as a negative lens, the object side is a spherical convex surface with a curvature radius of +41.561 mm, the image side is a spherical concave surface with a curvature radius of +23.623 mm, the central axis thickness is 1.000 mm, the refractive index is 1.74, the Abbe number is 27.8, and the central axis distance from the first lens L1 is 3.058 mm.

[0057] The third lens L3 is configured as a double convex spherical positive lens, the object side curvature radius is +44.499 mm, the image side curvature radius is -282.110 mm, the central axis thickness is 3.323 mm, the refractive index is 1.91, the Abbe number is 35.3, and the central axis distance from the second lens L2 is 1.949 mm.

[0058] The fourth lens L4 is configured as a double-concave negative lens with a radius of curvature of -23.568 mm on the object side, a radius of curvature of +25.179 mm on the image side, a central axial thickness of 1.717 mm, a refractive index of 1.85, an Abbe number of 23.8, and a central axial spacing from the third lens L3 of 4.776 mm.

[0059] The fifth lens L5 is configured as a double-convex positive lens with a radius of curvature of +25.179 mm on the object side, a radius of curvature of -32.355 mm on the image side, a central axial thickness of 6.405 mm, a refractive index of 1.82, an Abbe number of 46.5, and is cemented with the fourth lens L4 to form a first double-cemented lens.

[0060] The sixth lens L6 is configured as a double-convex positive lens with a radius of curvature of +52.566 mm on the object side, a radius of curvature of -62.885 mm on the image side, a central axial thickness of 4.409 mm, a refractive index of 2.00, an Abbe number of 29.1, and a central axial spacing from the fifth lens L5 of 0.150 mm.

[0061] The seventh lens L7 is configured as a double-concave negative lens with a radius of curvature of -82.225 mm on the object side, a radius of curvature of +28.128 mm on the image side, a central axial thickness of 0.800 mm, a refractive index of 1.72, an Abbe number of 38.0, and a central axial spacing from the sixth lens L6 of 0.800 mm in an infinite focus state.

[0062] The eighth lens L8 is configured as a double-convex positive lens with a radius of curvature of +352.623 mm on the object side, a radius of curvature of -83.022 mm on the image side, a central axial thickness of 2.670 mm, a refractive index of 1.95, an Abbe number of 17.9, and a central axial spacing from the seventh lens L7 of 2.375 mm.

[0063] The ninth lens L9 is configured as a double-convex positive lens with a radius of curvature of +31.310 mm on the object side, a radius of curvature of -69.185 mm on the image side, a central axial thickness of 4.762 mm, a refractive index of 1.92, an Abbe number of 20.9, and a central axial spacing from the aperture stop STO of 1.500 mm.

[0064] The tenth lens L10 is configured as a double-convex positive lens with a radius of curvature of +54.480 mm on the object side, a radius of curvature of -186.432 mm on the image side, a central axial thickness of 2.837 mm, a refractive index of 1.59, an Abbe number of 68.6, and a central axial spacing from the ninth lens L9 of 0.150 mm.

[0065] The eleventh lens L11 is configured as a double-concave spherical negative lens with a radius of curvature of -186.432 mm on the object side, a radius of curvature of +19.059 mm on the image side, a central axial thickness of 1.000 mm, a refractive index of 1.85, and an Abbe number of 25.2, and is cemented with the tenth lens L10 to form a second double-cemented lens.

[0066] The twelfth lens L12 is configured as a double-convex spherical positive lens with a radius of curvature of +24.969 mm on the object side, a radius of curvature of -12.920 mm on the image side, a central axial thickness of 5.904 mm, a refractive index of 1.82, and an Abbe number of 46.5, and is spaced apart from the central axis of the eleventh lens L11 by a distance of 0.675 mm.

[0067] The thirteenth lens L13 is configured as a double-concave spherical negative lens with a radius of curvature of -12.920 mm on the object side, a radius of curvature of +28.046 mm on the image side, a central axial thickness of 1.200 mm, a refractive index of 1.85, and an Abbe number of 23.8, and is cemented with the twelfth lens L12 to form a third double-cemented lens.

[0068] The fourteenth lens L14 is configured as a double-concave spherical negative lens with a radius of curvature of -67.879 mm on the object side, a radius of curvature of +52.298 mm on the image side, a central axial thickness of 1.000 mm, a refractive index of 1.85, and an Abbe number of 23.8, and is spaced apart from the central axis of the thirteenth lens L13 by a distance of 1.966 mm.

[0069] The fifteenth lens L15 is configured as a double-convex aspherical positive lens with a radius of curvature of +33.681 mm on the object side, a radius of curvature of -46.256 mm on the image side, a central axial thickness of 4.381 mm, a refractive index of 1.81, and an Abbe number of 40.7, and is spaced apart from the central axis of the fourteenth lens L14 by a distance of 0.150 mm and from the central axis of the image plane IMG by a distance of about 15.0 mm. In the expression f1 of the two aspherical surfaces of the fifteenth lens L15, the highest order of even terms is 10.

[0070] The spherical aberration curve in the vertical direction (i.e., the radial, Y-axis direction) calculated under the conditions of the incident light mixing range 430~658 nm, the incident pupil radius 8.7471 mm, the aperture F / 1.4, and the infinity focus state of the wide-angle fixed-focus lens is shown in FIG. 6. Figure 3a The vertical chromatic aberration curve calculated under the conditions of the incident light mixing range 430~658 nm, the incident pupil radius 8.7471 mm, the aperture F / 1.4, and the infinity focus state of the wide-angle fixed-focus lens is shown in FIG. 7. Figure 3b . Figure 3a The spherical aberration of all curves in FIG. 6 is in the range of -0.10~0.05 mm. Figure 3b The chromatic aberration of all curves in FIG. 7 is in the range of -2.5~5.0 microns.

[0071] Please refer to FIG. 6 and FIG. 7. Figure 4a and Figure 4bThe diagram shows the modulation transfer function (MTF) curve of the wide-angle fixed-focus lens calculated under the above conditions. Figure 4a It can be seen that the MTF values ​​of each curve decrease relatively uniformly within the frequency range of 0~30 lp / mm, with most curves distributed within a narrow range of the vertical axis, and only the 14.2 mm-sagittal curve eventually decreasing to approximately 0.35. From Figure 4b It can be seen that the image quality of this wide-angle fixed-focus lens at an aperture of F / 1.4 can meet the requirements of APS-C cameras.

[0072] This wide-angle fixed-focus lens has three cemented doublet lenses. The positive and negative lenses of the cemented doublet have a large difference in dispersion coefficient, which can correct axial chromatic aberration, spherical aberration and distortion aberration, and can also control the axial length. In addition, it reduces the tolerance sensitivity of image quality and facilitates manufacturing and assembly.

[0073] In this wide-angle fixed-focus lens, the first lens group G1 includes two meniscus negative lenses, one biconvex spherical positive lens, a first cemented doublet lens, and another biconvex spherical positive lens. The movable second lens group G2 consists of one biconcave spherical negative lens and one biconvex spherical positive lens. The third lens group G3 includes one biconvex spherical positive lens, a second cemented doublet lens, a third cemented doublet lens, one biconcave spherical negative lens, and one biconvex aspherical positive lens. The first and third cemented doublet lenses are optically symmetrical. The highest order of the even-order term in the aspherical expression of the aspherical positive lens is 10, which facilitates manufacturing.

[0074] For details on the structure and function of this wide-angle fixed-focus lens as a replaceable component for APS-C cameras, especially mirrorless cameras, please refer to paragraphs 0110 to 0122 on pages 10-11 of the specification of patent CN10847825A, or refer to commercially available camera fixed-focus lenses.

[0075] In other embodiments, the lens can be made of other types of optical materials, the stepper motor can be replaced by a voice coil motor or an ultrasonic motor, and the total focal length of the wide-angle fixed-focus lens can be any value within the range of 20-30mm. Based on the lens data of Embodiment 1, the surface shape, central axis thickness, and central axis spacing of each lens can be adaptively adjusted to achieve clear imaging and other technical requirements of the camera. Specifically:

[0076] The refractive index of the first lens L1 is 1.45~1.55, and the Abbe number is 68.0~73.0;

[0077] The refractive index of the second lens L2 is 1.70~1.80, and the Abbe number is 25.0~30.0;

[0078] The refractive index of the third lens L3 is 1.85~1.95, and the Abbe number is 33.0~38.0;

[0079] The fourth lens L4, the thirteenth lens L13, and the fourteenth lens L14 use the same optical material with a refractive index of 1.80~1.90 and an Abbe number of 21.0~26.0.

[0080] The fifth lens L5 and the twelfth lens L12 use the same optical material with a refractive index of 1.75~1.85 and an Abbe number of 44~49.

[0081] The refractive index of the sixth lens L6 is 1.95~2.05, and the Abbe number is 26.5~31.5;

[0082] The seventh lens, L7, has a refractive index of 1.67 to 1.77 and an Abbe number of 35.5 to 40.5.

[0083] The eighth lens, L8, has a refractive index of 1.90~2.00 and an Abbe number of 16.5~21.5.

[0084] The refractive index of the ninth lens L9 is 1.87~1.97, and the Abbe number is 18.5~23.5.

[0085] The tenth lens L10 has a refractive index of 1.55~1.65 and an Abbe number of 66.0~71.0;

[0086] The refractive index of the eleventh lens L11 is 1.80~1.90, and the Abbe number is 23.0~28.0;

[0087] The refractive index of the fifteenth lens L15 is 1.75~1.85, and the Abbe number is 38.0~43.0.

[0088] All the embodiments, application examples, and technical analyses described above are intended to introduce the technical concept and features of this utility model, enabling those skilled in the art to implement the technical solution of this utility model, and do not constitute any limitation on the scope of protection of this utility model. Simple modifications and equivalent transformations to the above embodiments are all within the scope of protection of the claims of this utility model.

Claims

1. A wide-angle fixed-focus lens, comprising a first lens group with positive optical power, a second lens group with negative optical power, and a third lens group with positive optical power, which are sequentially distributed along the central axis. It also includes an aperture stop. When focusing from infinity to a nearby object, the first lens group, the aperture stop, and the third lens group are fixed relative to the image plane, and the second lens group moves along the central axis to the image plane. Its features are, The first lens group comprises lenses arranged sequentially along the central axis: The first lens is configured as a negative lens, with a spherical convex surface on the object side and a spherical concave surface on the image side; The second lens is configured as a negative lens, with a convex spherical surface on the object side and a concave spherical surface on the image side; The third lens is configured as a biconvex spherical positive lens; The fourth lens is configured as a biconcave spherical negative lens with a refractive index of 1.80~1.90 and an Abbe number of 21~26. The fifth lens, configured as a biconvex spherical positive lens, has a refractive index of 1.75~1.85 and an Abbe number of 44~49, and is cemented together with the fourth lens to form the first cemented doublet lens; and The sixth lens is configured as a biconvex spherical positive lens; The second lens group includes the following components distributed sequentially along the central axis: The seventh lens is configured as a biconcave spherical negative lens; and The eighth lens is configured as a biconvex spherical positive lens; The third lens group includes the following elements distributed sequentially along the central axis: The ninth lens is configured as a biconvex spherical positive lens; The tenth lens is configured as a biconvex spherical positive lens; The eleventh lens is configured as a double concave spherical negative lens and is cemented together with the tenth lens to form a second cemented doublet lens. The twelfth lens is configured as a biconvex spherical positive lens and has the same refractive index and Abbe number as the fifth lens; The thirteenth lens is configured as a double concave spherical negative lens, with the same refractive index and Abbe number as the fourth lens, and is cemented together with the twelfth lens to form the third cemented doublet lens; The fourteenth lens is configured as a biconcave spherical negative lens, with the same refractive index and Abbe number as the fourth lens; and The fifteenth lens is configured as a biconvex aspherical positive lens, and the highest order of the even-order terms of the aspherical expressions of the object side and image side is 10.

2. The wide-angle fixed-focus lens according to claim 1, characterized in that, The total focal length of this wide-angle fixed-focus lens is 20~30 mm.

3. The wide-angle fixed-focus lens according to claim 2, characterized in that, The seventh lens has an object-side surface curvature radius of -82mm, an object-side surface curvature radius of +28mm, a refractive index of 1.67~1.77, and an Abbe number of 35.5~40.

5. The eighth lens has an object-side surface curvature radius of +353mm, an object-side surface curvature radius of -83mm, a refractive index of 1.90~2.00, and an Abbe number of 18.5~23.

5.

4. The wide-angle fixed-focus lens according to claim 3, characterized in that, The first lens has an object-side radius of curvature of +52.816 mm, an image-side radius of curvature of +17.784 mm, a central axis thickness of 1.200 mm, a refractive index of 1.49, and an Abbe number of 70.

4. The second lens has an object-side radius of curvature of +41.561 mm, an image-side radius of curvature of +23.623 mm, a central axis thickness of 1.000 mm, a refractive index of 1.74, and an Abbe number of 27.

8. The third lens has an object-side radius of curvature of +44.499 mm, an image-side radius of curvature of -282.110 mm, a central axis thickness of 3.323 mm, a refractive index of 1.91, and an Abbe number of 35.

3. The fourth lens has an object-side radius of curvature of -23.568 mm, an image-side radius of curvature of +25.179 mm, a central axis thickness of 1.717 mm, a refractive index of 1.85, and an Abbe number of 23.

8. The fifth lens has an object-side radius of curvature of +25.179 mm, an image-side radius of curvature of -32.355 mm, a central axis thickness of 6.405 mm, a refractive index of 1.82, and an Abbe number of 46.

5. The sixth lens has an object-side radius of curvature of +52.566 mm, an image-side radius of curvature of -62.885 mm, a central axis thickness of 4.409 mm, a refractive index of 2.00, and an Abbe number of 29.

1.

5. The wide-angle fixed-focus lens according to claim 4, characterized in that, The ninth lens has an object-side radius of curvature of +31.310 mm, an image-side radius of curvature of -69.185 mm, a central axis thickness of 4.762 mm, a refractive index of 1.92, and an Abbe number of 20.

9. The tenth lens has an object-side radius of curvature of +54.480 mm, an image-side radius of curvature of -186.432 mm, a central axis thickness of 2.837 mm, a refractive index of 1.59, and an Abbe number of 68.

6. The eleventh lens has an object-side radius of curvature of -186.432 mm, an image-side radius of curvature of +19.059 mm, a central axis thickness of 1.000 mm, a refractive index of 1.85, and an Abbe number of 25.

2. The twelfth lens has an object-side radius of curvature of +24.969 mm, an image-side radius of curvature of -12.920 mm, a central axis thickness of 5.904 mm, a refractive index of 1.82, and an Abbe number of 46.

5. The thirteenth lens has an object-side radius of curvature of -12.920 mm, an image-side radius of curvature of +28.046 mm, a central axis thickness of 1.200 mm, a refractive index of 1.85, and an Abbe number of 23.

8. The fourteenth lens has an object-side radius of curvature of -67.879 mm, an image-side radius of curvature of +52.298 mm, a central axis thickness of 1.000 mm, a refractive index of 1.85, and an Abbe number of 23.

8. The fifteenth lens has an object-side radius of curvature of 33.681 mm, an image-side radius of curvature of -46.256 mm, a central axis thickness of 4.381 mm, a refractive index of 1.81, and an Abbe number of 40.

7.

6. The wide-angle fixed-focus lens according to claim 5, characterized in that, The seventh lens has an object-side radius of curvature of -82.225 mm, an image-side radius of curvature of +28.128 mm, a central axis thickness of 0.800 mm, a refractive index of 1.72, and an Abbe number of 38.

0. The eighth lens has an object-side radius of curvature of +352.623 mm, an image-side radius of curvature of -83.022 mm, a central axis thickness of 2.670 mm, a refractive index of 1.95, and an Abbe number of 17.

9.

7. The wide-angle fixed-focus lens according to claim 6, characterized in that, The aperture stop is positioned between the second lens group and the third lens group.

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