Prime lens

Abstract

The prime lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are sequentially arranged from an object plane to an image plane along an optical axis, 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 negative focal power, the fifth lens has positive focal power, and the sixth lens has positive focal power. The focal power of the first lens is # imgabs 0 #, the focal power of the second lens is # imgabs 1 #, the focal power of the third lens is # imgabs 2 #, the focal power of the fourth lens is # imgabs 3 #, the focal power of the fifth lens is # imgabs 4 #, the focal power of the sixth lens is # imgabs 5 #, and the focal power of the prime lens is # imgabs 6 #. According to the prime lens provided by the utility model, the imaging quality is improved under the condition of ensuring a large aperture and low cost.

Description

Technical Field

[0001] The utility model relates to the technical field of optical devices, and particularly relates to a fixed-focus lens. Background Art

[0002] Lidar lenses are widely used in industries such as warehousing logistics and vehicle-mounted applications. With the complexity of application scenarios, the laser has an increasing demand for the field of view angle of the lens. Most of the receiving-end lenses of lasers have a CRA that is not small enough, a small field of view angle, an insufficient aperture, a weak received signal, and more noise may be obtained after image enhancement processing. The change in ambient temperature affects the back focal length of the lens, and it is necessary to control the temperature of the lens to ensure the imaging quality. Therefore, it is necessary to develop an optical lens with a large aperture and low cost. Summary of the Utility Model

[0003] The utility model provides a fixed-focus lens to achieve a fixed-focus lens with a large aperture and low cost.

[0004] According to one aspect of the utility model, a fixed-focus lens is provided, which includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged in sequence from the object plane to the image plane along the optical axis;

[0005] 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 negative optical power, the fifth lens has a positive optical power, and the sixth lens has a positive optical power;

[0006] The optical power of the first lens is φ1, the optical power of the second lens is φ2, the optical power of the third lens is φ3, the optical power of the fourth lens is φ4, the optical power of the fifth lens is φ5, the optical power of the sixth lens is φ6, and the optical power of the fixed-focus lens is φ, where:

[0007] -0.554 < φ1 / φ < -0.290; -0.446 < φ2 / φ < -0.189; 0.258 < φ3 / φ < 0.579; -0.363 < φ4 / φ < -0.056; 0.531 < φ5 / φ < 0.776; -0.420 < φ6 / φ < -0.129.

[0008] Optionally, the surface of the lens adjacent to the object plane is the object side surface, and the surface of the lens adjacent to the image plane is the image side surface;

[0009] The object side of the first lens bulges towards the object surface, and the image side of the first lens bulges towards the object surface; the object side of the third lens bulges towards the object surface, and the image side of the third lens depresses towards the object surface; the object side of the fourth lens bulges towards the object surface, and the image side of the fourth lens bulges towards the object surface; the object side of the sixth lens bulges towards the object surface.

[0010] Optionally, the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens are all glass spherical lenses.

[0011] Optionally, the refractive index of the fourth lens is nd4, and the Abbe number is vd4, where: 1.80 ≤ nd4 ≤ 1.91; 20.00 ≤ vd4 ≤ 35.25.

[0012] Optionally, the radius of curvature of the near object surface of the fourth lens is R41, the radius of curvature of the near image surface is R42, and the central thickness of the fourth lens is D4; where: 0.3 ≤ |R1 - R2| - D4 ≤ 5.

[0013] Optionally, the entrance pupil diameter of the fixed-focus lens is EPD, and the effective focal length of the fixed-focus lens is EFL, where: 0.819 ≤ EPD / EFL ≤ 1.2.

[0014] Optionally, the image plane diameter of the fixed-focus lens is IC, and the overall optical length of the fixed-focus lens is TTL, where: IC / TTL ≤ 0.248.

[0015] Optionally, the f-number of the fixed-focus lens is F, where 1.2 ≤ F ≤ 1.3.

[0016] Optionally, the fixed-focus lens further includes a diaphragm;

[0017] The diaphragm is located in the optical path between the third lens and the fourth lens.

[0018] Optionally, a filter is further provided along the object surface to the image surface; the filter is located on the side of the image side of the sixth lens.

[0019] The technical solution of the embodiment of the present invention provides a fixed-focus lens including a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens arranged in sequence along the optical axis from the object surface to the image surface; 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 negative optical power, the fifth lens has a positive optical power, and the sixth lens has a positive optical power; by reasonably distributing the optical powers of each lens, it is beneficial to correct aberration, ensure that the lens has a high resolution, and improve the imaging quality.

[0020] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present utility model, nor is it used to limit the scope of the present utility model. Other features of the present utility model will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0022] Figure 1 Structural schematic diagram of a fixed-focus lens provided by the present utility model;

[0023] Figure 2 Visible light spot diagram of a fixed-focus lens provided in Embodiment 1 of the present utility model;

[0024] Figure 3 Relative illuminance diagram of a fixed-focus lens provided in Embodiment 1 of the present utility model;

[0025] Figure 4 Structural schematic diagram of a fixed-focus lens provided in Embodiment 2 of the present utility model;

[0026] Figure 5 Visible light spot diagram of a fixed-focus lens provided in Embodiment 2 of the present utility model;

[0027] Figure 6 Relative illuminance diagram of a fixed-focus lens provided in Embodiment 2 of the present utility model;

[0028] Figure 7 Structural schematic diagram of a fixed-focus lens provided in Embodiment 3 of the present utility model;

[0029] Figure 8 Visible light spot diagram of a fixed-focus lens provided in Embodiment 3 of the present utility model;

[0030] Figure 9 Relative illuminance diagram of a fixed-focus lens provided in Embodiment 3 of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] To enable those skilled in the art to better understand the solution of the present utility model, the technical solutions in the embodiments of the present utility model will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0032] It should be noted that the terms "first", "second", etc. in the description and claims of the present utility model and the above-mentioned accompanying drawings are used to distinguish similar objects, and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances so that the embodiments of the present utility model described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0033] Figure 1 FIG. is a schematic structural diagram of a fixed-focus lens provided by the present utility model. The fixed-focus lens includes a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, and a sixth lens 106 arranged in sequence along the optical axis from the object plane to the image plane; the first lens 101 has a negative optical power, the second lens 102 has a negative optical power, the third lens 103 has a positive optical power, the fourth lens 104 has a negative optical power, the fifth lens 105 has a positive optical power, and the sixth lens 106 has a positive optical power; the optical power of the first lens 101 is φ1, the optical power of the second lens 102 is φ2, the optical power of the third lens 103 is φ3, the optical power of the fourth lens 104 is φ4, the optical power of the fifth lens 105 is φ5, and the optical power of the sixth lens 106 is φ6. The optical power of the fixed-focus lens is φ, where: -0.554 < φ1 / φ < -0.290; -0.446 < φ2 / φ < -0.189; 0.258 < φ3 / φ < 0.579; -0.363 < φ4 / φ < -0.056; 0.531 < φ5 / φ < 0.776; -0.420 < φ6 / φ < -0.129.

[0034] Among them, the optical 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 ability of the optical system to deflect light rays. The greater the absolute value of the optical power, the stronger the bending ability of the light rays; the smaller the absolute value of the optical power, the weaker the bending ability of the light rays. When the optical power is positive, the refraction of the light rays is convergent; when the optical power is negative, the refraction of the light rays is divergent. The optical power can be used to characterize a certain refracting surface of a lens (i.e., a surface of the lens), can be used to characterize a certain lens, or can be used to characterize a system formed by multiple lenses (i.e., a lens group). In the fixed-focus lens provided in this embodiment, each lens can be fixed in a lens barrel ( Figure 1 not shown in the figure). The first lens 101 is a negative optical power lens, which is used to control the incident angle of the optical system and correct the field curvature; the second lens 102 is a negative optical power lens, which is used to correct the off-axis aberration; the third lens 103 functions to correct spherical aberration, chromatic aberration of magnification, and axial chromatic aberration; reasonably allocate the optical power of each lens so that the light rays can be stable during the propagation process and do not have excessive deflection on a certain surface, so as to avoid introducing greater aberration.

[0035] Optionally, the surface of the lens adjacent to the object surface side is the object side surface, and the surface of the lens adjacent to the image surface side is the image side surface; the object side surface of the first lens 101 protrudes toward the object surface, and the image side surface of the first lens 101 protrudes toward the object surface; the object side surface of the third lens 103 protrudes toward the object surface, and the image side surface of the third lens 103 is concave toward the object surface; the object side surface of the fourth lens 104 protrudes toward the object surface, and the image side surface of the fourth lens 104 protrudes toward the object surface; the object side surface of the sixth lens 106 protrudes toward the object surface.

[0036] Among them, as Figure 1 shown, the object side surface of the first lens 101 protrudes toward the object surface, and the image side surface of the first lens 101 protrudes toward the object surface; the object side surface of the second lens 102 protrudes toward the object surface, and the image side surface of the second lens 102 protrudes toward the object surface; the object side surface of the third lens 103 protrudes toward the object surface, and the image side surface of the third lens 103 is concave toward the object surface; the object side surface of the fourth lens 104 protrudes toward the object surface, and the image side surface of the fourth lens 104 protrudes toward the object surface; the object side surface of the fifth lens 1051 protrudes toward the object surface, and the image side surface of the fifth lens 105 is concave toward the object surface; the object side surface of the sixth lens 106 protrudes toward the object surface, and the image side surface of the fifth lens 101 is concave toward the object surface. By reasonably setting the surface types of each lens, while ensuring that the optical power of each lens meets the optical power requirements in the above embodiment, it is also possible to ensure that the entire fixed-focus lens has a compact structure and a high integration degree.

[0037] Optionally, the first lens 101, the second lens 102, the third lens 103, the fourth lens 104, the fifth lens 105, and the sixth lens 106 are all glass spherical lenses.

[0038] Among them, each lens in the fixed-focus lens adopts a glass spherical lens to better correct chromatic aberration and spherical aberration and improve image quality. The material of the glass spherical lens is various types of glass known to those skilled in the art, and the embodiments of the present invention will not elaborate or limit this.

[0039] Optionally, the refractive index of the fourth lens 104 is nd4, and the Abbe number is vd4, where: 1.80 ≤ nd4 ≤ 1.91; 20.00 ≤ vd4 ≤ 35.25.

[0040] Among them, the refractive index is the ratio of the propagation speed of light in a vacuum to the propagation speed of light in the medium, mainly used to describe the refractive ability of the material to light, and the refractive indices of different materials are different. The Abbe number is an index used to represent the dispersion ability of a transparent medium. The more severe the dispersion of the medium, the smaller the dispersion coefficient; conversely, the milder the dispersion of the medium, the larger the dispersion coefficient. Thus, by reasonably matching and setting the refractive index and dispersion coefficient of the lenses in the fixed-focus lens, the chromatic aberration of the lens can be corrected, and it is beneficial to realize the miniaturized design of the fixed-focus lens; at the same time, it is beneficial to achieve a higher pixel resolution and a larger aperture.

[0041] Optionally, the radius of curvature of the near object surface of the fourth lens 104 is R41, the radius of curvature of the near image surface is R42, and the central thickness of the fourth lens is D4; where: 0.3 ≤ |R1 - R2| - D4 ≤ 5.

[0042] Among them, by reasonably designing the curvature of both sides of the fourth lens 104, it is beneficial to meet the system functionality while facilitating lens processing.

[0043] Optionally, the entrance pupil diameter of the fixed-focus lens is EPD, and the effective focal length of the fixed-focus lens is EFL, where: 0.819 ≤ EPD / EFL ≤ 1.2.

[0044] Among them, the entrance pupil diameter EPD of the fixed-focus lens and the effective focal length EFL of the fixed-focus lens satisfy the above conditions, indicating that the fixed-focus lens has a large aperture. When the focal length is fixed, the larger the value of the entrance pupil diameter of the fixed-focus lens, the larger the aperture of the fixed-focus lens.

[0045] Optionally, the image plane diameter of the fixed-focus lens is IC, and the overall optical length of the fixed-focus lens is TTL, where: IC / TTL ≤ 0.248.

[0046] Among them, the effective image plane diameter of the fixed-focus lens is IC (Image circle), and the distance from the optical axis center of the object side of the first lens to the image plane is the overall optical length TTL. In this embodiment, by reasonably setting the relationship between the image plane diameter IC of the fixed-focus lens and the overall optical length TTL of the fixed-focus lens, while meeting the image plane requirements, the overall length of the fixed-focus lens is reduced, the miniaturization of the fixed-focus lens is realized, and it is beneficial for later assembly.

[0047] Optionally, the aperture number of the fixed-focus lens is F, where 1.2 ≤ F ≤ 1.3.

[0048] Among them, the function of the aperture is to determine the amount of light entering the fixed-focus lens and adjust the amount of light entering the fixed-focus lens. The smaller the aperture number, the larger the aperture, and the more the amount of light entering; conversely, the larger the aperture number, the smaller the aperture, and the less the amount of light entering. The optical setting of the fixed-focus lens can meet a large light flux, so as to meet the use effect under low-illumination and low-light conditions. Further, a large field of view angle of 161° can be achieved, realizing a wide range of field of view requirements.

[0049] Optionally, the fixed-focus lens further includes a diaphragm 10; the diaphragm 10 is located in the optical path between the third lens 103 and the fourth lens 104.

[0050] Among them, by setting the diaphragm 10 in the optical path between the third lens 103 and the fourth lens 104, the propagation direction of the light beam can be adjusted, and the incident angle of the light can be adjusted, which is beneficial to improving the imaging quality. At the same time, the diaphragm 10 is located in the middle of the fixed-focus lens, which can also ensure the minimization of the front and rear apertures of the fixed-focus lens.

[0051] Optionally, a filter 11 is further provided along the object surface to the image surface; the filter 11 is located on the image side of the sixth lens 106.

[0052] Among them, by setting the filter 11 between the sixth lens 106 and the image surface, unnecessary stray light is filtered out, thereby improving the image quality of the fixed-focus lens. For example, the imaging quality of the fixed-focus lens is improved by filtering out infrared light during the day through the filter 11.

[0053] In summary, the fixed-focus lens provided by the embodiment of the present invention provides a fixed-focus lens with a field of view angle that can reach 161° by reasonably distributing the optical power. At the same time, the use of all-glass lenses realizes the characteristics of low cost, and the maximum can match a 1 / 1.7″ target surface photosensitive chip, realizing a fixed-focus lens with a large aperture, small CRA, small blur spot, high relative illumination, uniform imaging, and short overall length.

[0054] The following further describes a specific embodiment of the fixed-focus lens applicable to the above embodiment with reference to the accompanying drawings.

[0055] Embodiment 1

[0056] Continue to refer to Figure 1, the fixed - focus lens includes a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, and a sixth lens 106 arranged in sequence along the optical axis from the object plane to the image plane; the object side surface of the first lens 101 bulges towards the object plane, and the image side surface of the first lens 101 bulges towards the object plane; the object side surface of the second lens 102 bulges towards the object plane, and the image side surface of the second lens 102 bulges towards the object plane; the object side surface of the third lens 103 bulges towards the object plane, and the image side surface of the third lens 103 is concave towards the object plane; the object side surface of the fourth lens 104 bulges towards the object plane, and the image side surface of the fourth lens 104 bulges towards the object plane; the object side surface of the fifth lens 105 bulges towards the object plane, and the image side surface of the fifth lens 105 is concave towards the object plane; the object side surface of the sixth lens 106 bulges towards the object plane, and the image side surface of the sixth lens 106 is concave towards the object plane. Among them, the aperture stop 10 is arranged in the optical path between the third lens 103 and the fourth lens 104. Exemplarily, Table 1, in a feasible implementation manner, details the specific optical and physical parameters of each lens in the fixed - focus lens provided in the first embodiment of the present invention. The fixed - focus lens in Table 1 corresponds to Figure 1 the aforesaid fixed - focus lens.

[0057] Table 1 Design values of the optical and physical parameters of the fixed - focus lens

[0058] Surface number Surface type Radius of curvature Thickness Material (nd) Material (vd) Semi-diameter S1 Spherical surface 24.040 1.000 2.003 28.32 9.58 S2 Spherical surface 6.609 4.593 6.10 S3 Spherical surface 105.559 3.339 1.438 94.52 5.81 S4 Spherical surface 7.215 1.820 4.45 S5 Spherical surface 16.720 6.101 1.801 34.97 4.48 S6 Spherical surface -18.494 0.125 4.07 STO Spherical surface Infinity 0.644 3.92 S7 Spherical surface 23.777 5.317 1.911 35.25 4.21 S8 Spherical surface 13.689 1.118 4.65 S9 Spherical surface 2657.726 1.766 2.003 28.32 4.97 S10 Spherical surface -14.081 1.760 5.26 S11 Spherical surface 12.810 4.683 2.003 28.32 7.10 S12 Spherical surface -600.528 2.244 6.69 S13 Spherical surface PL 0.50 1.517 64.199 5.88 S14 Spherical surface PL 5.77

[0059] Among them, the surface serial number is numbered according to the surface order of each lens. For example, the surfaces with surface serial numbers S1 and S2 are the object side surface and the image side surface of the first lens 101 respectively, the surfaces with surface serial numbers S3 and S4 are the object side surface and the image side surface of the second lens 102 respectively, and so on. The radius of curvature represents the degree of curvature of the lens surface. A positive value represents that the surface bends towards the object plane side and the center of the circle is close to the image plane, and a negative value represents that the surface bends towards the image plane side and the center of the circle is close to the object plane. Among them, PL represents that the surface is a plane and the radius of curvature is infinite; the thickness represents the central axial distance from the current surface to the next surface. Among them, due to different digit numbers of each parameter value, there is an error in focusing. Therefore, the thickness of the object side surface S14 of the filter is not given a specific value and can be adjusted according to the situation to achieve clear focusing; the material (nd) represents the refractive index, that is, the ability of the material between the current surface and the next surface to deflect light. A space represents that the current position is air and the refractive index is 1; the material (vd) represents the Abbe number, that is, the dispersion characteristic of the material between the current surface and the next surface to light. A space represents that the current position is air. The semi - diameter represents the semi - aperture of the lens. STO represents the aperture stop.

[0060] The fixed - focus lens of the first embodiment satisfies the following parameters: focal length: 4.076 mm; aperture: F1.24, field of view angle: 163.15°; total optical length: 39.63 mm.

[0061] Furthermore, Figure 2 This is the spot diagram of visible light of a fixed-focus lens provided in the first embodiment of the present invention. Among them, the spot diagram is one of the most commonly used evaluation methods in modern optical design. The spot diagram refers to the fact that many rays emitted by a point light source, after passing through an optical system, due to aberration, their intersection points with the image plane are no longer concentrated at the same point, but form a diffuse pattern scattered within a certain range. As Figure 2 shown, for the fixed-focus lens provided in the first embodiment of the present invention, the diffuse patterns of three different wavelengths of visible light (0.930μm, 0.940μm, 0.950μm) in each field of view are relatively concentrated and evenly distributed, and there is no phenomenon that the diffuse pattern in a certain field of view is separated vertically by a large amount with the change of wavelength, indicating no obvious purple fringing. At the same time, the diffuse spots of three different wavelengths of visible light (0.930μm, 0.940μm, 0.950μm) in different fields of view of the fixed-focus lens are relatively small (the CEO radius is less than 30μm), and the imaging rays are relatively concentrated, indicating that the lens can well meet the usage requirements of lidar.

[0062] Figure 3 This is the relative illumination diagram of a fixed-focus lens provided in the first embodiment of the present invention. The ordinate is the normalized relative illumination value, and the abscissa is the corresponding field of view. It can be seen from the figure that the relative illumination of the edge field of view of this optical system is higher than 80%, and the imaging uniformity is better.

[0063] Embodiment 2

[0064] Figure 4 This is the structural schematic diagram of the fixed-focus lens provided in the second embodiment of the present invention. As Figure 4 shown, the fixed-focus lens provided in the second embodiment of the present invention includes a first lens 201, a second lens 202, a third lens 203, a fourth lens 204, a fifth lens 205, and a sixth lens 206 arranged in sequence along the optical axis from the object plane to the image plane; the object side of the first lens 201 bulges toward the object plane, and the image side of the first lens 201 bulges toward the object plane; the object side of the second lens 202 is concave toward the object plane, and the image side of the second lens 202 bulges toward the object plane; the object side of the third lens 203 bulges toward the object plane, and the image side of the third lens 203 is concave toward the object plane; the object side of the fourth lens 204 bulges toward the object plane, and the image side of the fourth lens 204 bulges toward the object plane; the object side of the fifth lens 205 bulges toward the object plane, and the image side of the fifth lens 205 is concave toward the object plane; the object side of the sixth lens 206 bulges toward the object plane, and the image side of the sixth lens 201 bulges toward the object plane. Among them, the aperture stop 10 is arranged in the optical path between the third lens 203 and the fourth lens 204. Exemplarily, Table 2 details the specific optical physical parameters of each lens in the fixed-focus lens provided in the second embodiment of the present invention in a feasible implementation manner. The fixed-focus lens in Table 2 corresponds toFigure 4 The fixed-focus lens described above.

[0065] Table 2 Design values of the optical physical parameters of the fixed-focus lens

[0066]

[0067] Among them, the surface numbers are numbered according to the surface order of each lens. For example, the surfaces with surface numbers S1 and S2 are the object side and the image side of the first lens 201 respectively, and the surfaces with surface numbers S3 and S4 are the object side and the image side of the second lens 202 respectively, and so on. The radius of curvature represents the degree of curvature of the lens surface. A positive value represents that the surface bends towards the object side, and the center of the circle is close to the image side. A negative value represents that the surface bends towards the image side, and the center of the circle is close to the object side. Among them, PL represents that the surface is a plane and the radius of curvature is infinite; the thickness represents the central axial distance from the current surface to the next surface. Among them, due to the different number of digits of each parameter value, there is an error in focusing. Therefore, the thickness of the object side S14 of the filter is not given a specific value, and the value can be adjusted according to the situation to achieve the purpose of clear focusing; the material (nd) represents the refractive index, that is, the ability of the material between the current surface and the next surface to deflect light. A space represents that the current position is air and the refractive index is 1; the material (vd) represents the Abbe number, that is, the dispersion characteristic of the material between the current surface and the next surface to light. A space represents that the current position is air. The semi-diameter represents the semi-aperture of the lens. STO represents the aperture stop.

[0068] The fixed-focus lens of the second embodiment satisfies the following parameters: focal length: 4.076 mm; aperture: F1.24, field of view angle: 163.3°; total optical length: 39.6 mm.

[0069] Furthermore, Figure 5 This is the spot diagram of visible light points of a fixed-focus lens provided by the second embodiment of the present invention. Among them, the spot diagram is one of the most commonly used evaluation methods in modern optical design. The spot diagram refers to a dispersion pattern formed by many rays emitted from a point light source passing through an optical system. Due to aberration, the intersection points of these rays with the image plane are no longer concentrated at the same point, but are scattered within a certain range. As Figure 5 shown, for the fixed-focus lens provided by the second embodiment of the present invention, the dispersion patterns of three different wavelengths of visible light (0.930 μm, 0.940 μm, 0.950 μm) under each field of view are relatively concentrated and evenly distributed. There is no phenomenon that the dispersion pattern under a certain field of view is separated vertically by a large amount with the change of wavelength, indicating no obvious purple fringing. At the same time, the dispersion spots of three different wavelengths of visible light (0.920 μm, 0.940 μm, 0.960 μm) under different fields of view of this fixed-focus lens are relatively small (the CEO radius is less than 30 μm), and the imaging rays are relatively concentrated, indicating that this lens can well meet the use requirements of lidar.

[0070] Figure 6 This is the relative illumination diagram of a fixed-focus lens provided in the second embodiment of the present invention. The vertical axis is the normalized relative illumination value, and the horizontal axis is the corresponding field of view. It can be seen from the figure that the relative illumination of the edge field of view of this optical system is higher than 80%, and the imaging uniformity is better.

[0071] Embodiment 3

[0072] Figure 7 This is the structural schematic diagram of the fixed-focus lens provided in the third embodiment of the present invention. As Figure 4 shown, the fixed-focus lens provided in the third embodiment of the present invention includes a first lens 301, a second lens 302, a third lens 303, a fourth lens 304, a fifth lens 305, and a sixth lens 306 arranged in sequence along the optical axis from the object plane to the image plane; the object side of the first lens 301 protrudes toward the object plane, and the image side of the first lens 301 protrudes toward the object plane; the object side of the second lens 302 protrudes toward the object plane, and the image side of the second lens 302 protrudes toward the object plane; the object side of the third lens 303 protrudes toward the object plane, and the image side of the third lens 303 is recessed toward the object plane; the object side of the fourth lens 304 protrudes toward the object plane, and the image side of the fourth lens 304 protrudes toward the object plane; the object side of the fifth lens 305 is recessed toward the object plane, and the image side of the fifth lens 305 protrudes toward the object plane; the object side of the sixth lens 306 protrudes toward the object plane, and the image side of the sixth lens 301 protrudes toward the object plane. Among them, the aperture stop 10 is disposed in the optical path between the third lens 303 and the fourth lens 304. Exemplarily, Table 3 details the specific optical and physical parameters of each lens in the fixed-focus lens provided in the third embodiment of the present invention in a feasible implementation manner. The fixed-focus lens in Table 3 corresponds to Figure 7 the fixed-focus lens described above.

[0073] Table 3 Design values of the optical and physical parameters of the fixed-focus lens

[0074]

[0075] Among them, the surface numbers are numbered according to the surface order of each lens. For example, the surfaces with surface numbers S1 and S2 are the object side and the image side of the first lens 301 respectively, and the surfaces with surface numbers S3 and S4 are the object side and the image side of the second lens 302 respectively, and so on. The radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface bends towards the object side, and the center of the circle is close to the image side. A negative value indicates that the surface bends towards the image side, and the center of the circle is close to the object side. Among them, PL represents that the surface is a plane and the radius of curvature is infinite; the thickness represents the central axial distance from the current surface to the next surface. Among them, due to the different number of digits of each parameter value, there is an error in focusing. Therefore, the thickness of the object side S14 of the filter is not given a specific value, and the value can be adjusted according to the situation to achieve the purpose of clear focusing; the material (nd) represents the refractive index, that is, the ability of the material between the current surface and the next surface to deflect light. A space represents that the current position is air and the refractive index is 1; the material (vd) represents the Abbe number, that is, the dispersion characteristic of the material between the current surface and the next surface to light. A space represents that the current position is air. The semi-diameter represents the semi-aperture of the lens. STO represents the aperture stop.

[0076] The fixed-focus lens of the first embodiment satisfies the following parameters: focal length: 4.043 mm; aperture: F1.2, field of view: 161.94°; total optical length: 38.7 mm.

[0077] Furthermore, Figure 8 This is a visible light spot diagram of a fixed-focus lens provided by Embodiment 3 of the present invention. Among them, the spot diagram is one of the most commonly used evaluation methods in modern optical design. The spot diagram refers to a dispersion pattern formed by many rays emitted from a point light source after passing through an optical system. Due to aberration, the intersection points of these rays with the image plane are no longer concentrated at the same point, but are scattered within a certain range. As Figure 8 shown, for the fixed-focus lens provided by Embodiment 3 of the present invention, the dispersion patterns of three different wavelengths of visible light (0.930 μm, 0.940 μm, 0.950 μm) at each field of view are relatively concentrated and evenly distributed. There is no phenomenon that the dispersion pattern at a certain field of view is separated up and down significantly with the wavelength, indicating no obvious purple fringing. At the same time, the dispersion spots of three different wavelengths of visible light (0.930 μm, 0.940 μm, 0.950 μm) at different fields of view of this fixed-focus lens are relatively small (the CEO radius is less than 30 μm), and the imaging rays are relatively concentrated, indicating that this lens can well meet the usage requirements of lidar.

[0078] Figure 9 This is a relative illumination diagram of a fixed-focus lens provided by Embodiment 3 of the present invention. The ordinate is the normalized relative illumination value, and the abscissa is the corresponding field of view. It can be seen from the figure that the relative illumination of the edge field of view of this optical system is higher than 85%, and the imaging uniformity is better.

[0079] To more clearly illustrate the above embodiments, Table 4 details the specific optical physical parameters of each lens in the fixed-focus lenses provided in the first to third embodiments of the present invention, as well as other feasible optical physical parameters.

[0080] Table 4 Design values of the optical physical parameters of the fixed-focus lens

[0081]

[0082]

[0083] The above specific implementation manners do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A fixed-focus lens, characterized in that: It includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are arranged in sequence from the object plane to the image plane along the optical axis; The first lens has negative optical power, the second lens has negative optical power, the third lens has positive optical power, the fourth lens has negative optical power, the fifth lens has positive optical power, and the sixth lens has positive optical power; The focal power of the first lens is φ1, the focal power of the second lens is φ2, the focal power of the third lens is φ3, the focal power of the fourth lens is φ4, the focal power of the fifth lens is φ5, the focal power of the sixth lens is φ6, and the focal power of the fixed focus lens is φ, wherein: -0.554<φ1 / φ<-0.290; -0.446<φ2 / φ<-0.189; 0.258<φ3 / φ<0.579; -0.363<φ4 / φ<-0.056; 0.531<φ5 / φ<0.776; -0.420<φ6 / φ<-0.

129.

2. The fixed-focus lens according to claim 1, characterized in that: The surface of the lens adjacent to the object plane is the object side surface, and the surface of the lens adjacent to the image plane is the image side surface; The object side surface of the first lens is convex toward the object plane, and the image side surface of the first lens is convex toward the object plane; the object side surface of the third lens is convex toward the object plane, and the image side surface of the third lens is concave toward the object plane; the object side surface of the fourth lens is convex toward the object plane, and the image side surface of the fourth lens is convex toward the object plane; the object side surface of the sixth lens is convex toward the object plane.

3. The fixed-focus lens according to claim 1, characterized in that: The first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens are all glass spherical lenses.

4. The fixed-focus lens according to claim 1, wherein: The refractive index of the fourth lens is nd4, and the Abbe number is vd4, wherein: 1.80≤nd4≤1.91; 20.00≤vd4≤35.

25.

5. The fixed-focus lens according to claim 1, wherein: The near object surface curvature radius of the fourth lens is R41, the near image surface curvature radius is R42, and the center thickness of the fourth lens is D4; wherein: 0.3≤|R1-R2|-D4≤5.

6. The fixed-focus lens according to claim 1, wherein: The entrance pupil diameter of the fixed-focus lens is EPD, and the effective focal length of the fixed-focus lens is EFL, wherein: 0.819≤EPD / EFL≤1.

2.

7. The fixed-focus lens according to claim 1, wherein: The image diameter of the fixed-focus lens is IC, and the total optical length of the fixed-focus lens is TTL, wherein: IC / TTL≤0.

248.

8. The fixed-focus lens according to claim 1, wherein: The aperture number of the fixed-focus lens is F, wherein 1.2≤F≤1.

3.

9. The fixed-focus lens according to claim 1, wherein: The fixed-focus lens further includes an aperture; The aperture stop is located in an optical path between the third lens and the fourth lens.

10. The fixed-focus lens according to claim 1, wherein: A filter is also arranged along the object plane to the image plane; the filter is located on the image side of the sixth lens.

Images