Prime lens

Abstract

The invention discloses a prime lens. A convex-concave first lens with negative focal power, a convex-concave second lens with negative focal power, a biconvex third lens with positive focal power, a diaphragm, a biconcave fourth lens with negative focal power, a biconvex fifth lens with positive focal power and a biconvex sixth lens with positive focal power are sequentially arranged from an object space to an image space along an optical axis. A concave-convex seventh lens with negative focal power, a biconvex eighth lens with positive focal power and a convex-concave ninth lens with negative focal power; wherein the first lens, the third lens, the fourth lens and the fifth lens are all glass spherical mirrors, and the second lens, the sixth lens, the seventh lens, the eighth lens and the ninth lens are all plastic aspheric mirrors, so that the focal power of each lens can be reasonably matched, and the material and the surface type of each lens can be reasonably matched; good imaging performance of the prime lens is achieved, the field angle of the prime lens is larger than 200 degrees, and the total optical length TTL is smaller than or equal to 17 mm.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to a fixed-focus lens. Background Art

[0002] As people's safety awareness increases, the market is becoming more and more demanding on lens parameters and performance. Wide-angle lenses are widely used in monitoring, photography, and vehicle-mounted industries because they can provide a wider field of view. In order to obtain a wider field of view, the field of view of the lens needs to be larger and larger, but at the same time, the cost of the lens also increases. Summary of the invention

[0003] The present invention provides a fixed-focus lens, which has a small size and low cost while being able to achieve a large field of view.

[0004] To achieve the above-mentioned purpose, an embodiment of the present invention provides a fixed-focus lens, comprising: a convex-concave first lens with negative power, a convex-concave second lens with negative power, a biconvex third lens with positive power, an aperture, a biconcave fourth lens with negative power, a biconvex fifth lens with positive power, a biconvex sixth lens with positive power, a concave-convex seventh lens with negative power, a biconvex eighth lens with positive power, and a convex-concave ninth lens with negative power, which are arranged in sequence from the object side to the image side along the optical axis;

[0005] Among them, the first lens, the third lens, the fourth lens, and the fifth lens are all glass spherical lenses, and the second lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens are all plastic aspherical lenses.

[0006] Optionally, the fourth lens and the fifth lens are cemented to form a first cemented lens.

[0007] Optionally, the sixth lens and the seventh lens are cemented to form a second cemented lens.

[0008] Optionally, the optical power of the first lens is The focal length of the fixed focal length lens Satisfies the relationship: The refractive index Nd1 of the first lens satisfies the relationship: 1.71≤Nd1≤2.10.

[0009] Optionally, the optical power of the second lens is The focal length of the fixed focal length lens Satisfies the relationship:

[0010] The focal power of the third lens The focal length of the fixed focal length lens Satisfies the relationship: The refractive index Nd3 of the third lens satisfies the relationship: 1.75≤Nd3≤2.10.

[0011] Optionally, the optical power of the fourth lens is The focal length of the fixed focal length lens Satisfies the relationship:

[0012] The optical power of the fifth lens The focal length of the fixed focal length lens Satisfies the relationship:

[0013]

[0014] The optical power of the sixth lens The focal length of the fixed focal length lens Satisfies the relationship:

[0015]

[0016] The optical power of the seventh lens The focal length of the fixed focal length lens Satisfies the relationship:

[0017]

[0018] Optionally, the Abbe number Vd4 of the fourth lens, the Abbe number Vd5 of the fifth lens, the Abbe number Vd6 of the sixth lens, and the Abbe number Vd7 of the seventh lens satisfy the following: 1.00≤Vd5-Vd4≤38.95; 23.15≤Vd6-Vd7≤50.5.

[0019] Optionally, the optical power of the eighth lens is The focal length of the fixed focal length lens Satisfies the relationship:

[0020] The optical power of the ninth lens The focal length of the fixed focal length lens Satisfies the relationship:

[0021]

[0022] Optionally, a refractive index Nd6 of the sixth lens, a refractive index Nd7 of the seventh lens, a refractive index Nd8 of the eighth lens, and a refractive index Nd9 of the ninth lens satisfy the following conditions: 2.98≤Nd6+Nd8≤3.20; 3.17≤Nd7+Nd9≤3.50.

[0023] Optionally, the total length TTL of the fixed-focus lens, the back focal length BFL of the fixed-focus lens, and the front focal length EFL of the fixed-focus lens satisfy the following relationship: 1.75≤EFL≤1.96; 0.05≤BFL / TTL≤0.14; 6.49≤(TTL-BFL) / EFL≤9.00.

[0024] The technical solution of the embodiment of the present invention is to arrange in sequence along the optical axis from the object side to the image side a convex-concave first lens with negative power, a convex-concave second lens with negative power, a biconvex third lens with positive power, an aperture, a biconcave fourth lens with negative power, a biconvex fifth lens with positive power, a biconvex sixth lens with positive power, a convex-concave seventh lens with negative power, a biconvex eighth lens with positive power and a convex-concave ninth lens with negative power; wherein the first lens, the third lens, the fourth lens, the fifth lens, the second lens, the second lens and the second lens are arranged in sequence from the object side to the image side; The first lens is a glass spherical lens, and the second lens, the sixth lens, the seventh lens, the eighth lens and the ninth lens are all plastic aspherical lenses. This arrangement can reasonably match the optical focal length of each lens, as well as the material and surface shape of each lens, so as to achieve good imaging performance of the fixed-focus lens, so that its field of view angle is greater than 200°, and the total optical length satisfies TTL≤17mm, thereby enabling the fixed-focus lens to achieve the effects of small size, low cost and large field of view angle, so as to meet the current needs of various industries for the field of view angle, volume and cost of the lens.

[0025] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 is a schematic structural diagram of a fixed-focus lens provided in Embodiment 1 of the present invention;

[0028] Figure 2 is a schematic diagram of axial aberration of a fixed-focus lens provided in Embodiment 1 of the present invention;

[0029] Figure 3 is a schematic structural diagram of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0030] Figure 4 is a schematic diagram of axial aberration of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0031] Figure 5 is a schematic structural diagram of a fixed-focus lens provided in Embodiment 3 of the present invention;

[0032] Figure 6 Schematic diagram of axial aberration of a fixed-focus lens provided in Embodiment 3 of the present invention. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0034] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0035] Figure 1 Schematic diagram of the structure of the fixed-focus lens proposed in Embodiment 1 of the present invention. Figure 3 Schematic diagram of the structure of the fixed-focus lens proposed in Embodiment 2 of the present invention. Figure 5 Schematic diagram of the structure of the fixed focus lens proposed in the third embodiment of the present invention. Figure 1 , Figure 3 and Figure 5 As shown, the fixed-focus lens comprises: a convex-concave first lens L1 with negative power, a convex-concave second lens L2 with negative power, a biconvex third lens L3 with positive power, an aperture STO, a biconcave fourth lens L4 with negative power, a biconvex fifth lens L5 with positive power, a biconvex sixth lens L6 with positive power, a convex-concave seventh lens L7 with negative power, a biconvex eighth lens L8 with positive power, and a convex-concave ninth lens L9 with negative power, which are arranged in sequence from the object side to the image side along the optical axis;

[0036] Among them, the first lens L1, the third lens L3, the fourth lens L4, and the fifth lens L5 are all glass spherical lenses, and the second lens L2, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the ninth lens L9 are all plastic aspherical lenses.

[0037] Specifically, the focal length is equal to the difference between the convergence of the image-side light beam and the convergence of the object-side light beam, and it characterizes the ability of the optical system to deflect light. The larger the absolute value of the focal length is, the stronger the ability to bend light is, and the smaller the absolute value of the focal length is, the weaker the ability to bend light is. When the focal length is a positive number, the refraction of light is convergent; when the focal length is a negative number, the refraction of light is divergent. The focal length can be used to characterize a certain refractive surface of a lens (i.e., a surface of a lens), can be used to characterize a certain lens, and can also 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 (not shown in the figure).

[0038] In this article, the paraxial area refers to the area near the optical axis. If the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at least in the paraxial area; if the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial area. The surface of each lens close to the object side is called the object side surface of the lens, and the surface of each lens close to the image side is called the image side surface of the lens. The judgment of the surface shape in the paraxial area can be based on the judgment method of the general knowledge in this field, and the positive and negative R value (R refers to the radius of curvature of the paraxial area, usually refers to the R value on the lens database (lens data) in the optical software) is used to judge the convexity and concavity. When the R value is positive, the lens surface is convex to the object side, and when the R value is negative, the lens surface is convex to the image side.

[0039] Exemplarily, the first lens L1 is a convexo-concave lens, then the object side surface and the image side surface of the first lens L1 are both convex toward the object side, the second lens L2 is a convexo-concave lens, then the object side surface and the image side surface of the second lens L2 are both convex toward the object side, the third lens L3 is a convexo-convex lens, then the object side surface of the third lens L3 is convex toward the object side, and the image side surface is convex toward the image side, the fourth lens L4 is a concave-concave lens, then the object side surface of the fourth lens L4 is convex toward the image side, and the image side surface is convex toward the object side. The fifth lens L5 is a convexo-convex lens, then the object side surface of the fifth lens L5 is convex toward the object side, and the image side surface is convex toward the image side. The sixth lens L6 is a convexo-convex lens, then the object side surface of the sixth lens L6 is convex toward the object side, and the image side surface is convex toward the image side. The seventh lens L7 is a concave-convex lens, then the object side surface of the seventh lens L7 is convex toward the image side, and the image side surface is convex toward the image side. The eighth lens L8 is a convex-convex lens, and the object-side surface of the eighth lens L8 is convex toward the object side, and the image-side surface is convex toward the image side. The ninth lens L9 is a convex-concave lens, and the object-side surface and the image-side surface of the ninth lens L9 are both convex toward the object side.

[0040] The lens adopts a 4G5P structure that is a mixture of a glass spherical lens and a plastic aspherical lens. The lens design is achieved through reasonable optical power distribution and material matching. Among them, the use of plastic aspherical lenses reduces the design cost of the lens. And the optical performance of the lens can be optimized by using a combination of glass spherical lenses and plastic aspherical lenses.

[0041] Among them, the first lens L1 is a negative meniscus lens with a convex front and concave back with negative focal power, which can help more light enter the optical system and ensure that the lens has a larger field of view angle range, and the field of view angle reaches 200°. The second lens L2 is a convex front and concave back plastic aspherical lens with negative focal power; the third lens L3 is a biconvex glass spherical lens with positive focal power. This can effectively shrink the light and promote the improvement of image quality; it is conducive to realizing miniaturized lens design. The fourth lens L4 is a biconcave glass spherical lens with negative focal power, which can diverge the light entering the third lens L3 again, so that the light enters the fifth lens L5 smoothly. The fifth lens L5 is a biconvex glass spherical lens with positive focal power, which can shrink the incoming light so that the light can smoothly enter the sixth lens L6. The sixth lens L6 is a biconvex plastic aspherical lens with positive focal power, which can further shrink the incoming light. The seventh lens L7 is a concave-convex plastic aspherical lens with negative focal power, which can diverge the incoming light again. The eighth lens L8 is a biconvex plastic aspheric lens with positive focal length, which can further shrink the incoming light. The ninth lens L9 is a convex-concave plastic aspheric lens with negative focal length, which can further diverge the incoming light so that the light reaches the chip on the image side, which is beneficial to expand the imaging range.

[0042] Therefore, the embodiment of the present invention adopts nine lenses, and reasonably matches the optical focal length of each lens, as well as the material and surface shape of each lens, to achieve good imaging performance of the fixed-focus lens, so that its field of view angle is greater than 200°, and the total optical length satisfies TTL≤17mm, thereby enabling the fixed-focus lens to achieve the effects of small size, low cost and large field of view, so as to meet the current requirements of various industries for the field of view angle, volume and cost of the lens.

[0043] Optionally, the fourth lens L4 and the fifth lens L5 are glued together to form a first glued lens. The glueing of the fourth lens L4 and the fifth lens L5 can effectively reduce the air gap between the two lenses, thereby helping to reduce the total length of the lens. In addition, the glued lens can minimize or eliminate chromatic aberration, so that various aberrations of the fixed-focus lens can be fully corrected. Under the premise of compact structure, it can improve resolution, optimize optical properties such as distortion, reduce light loss caused by reflection between lenses, and increase illumination, thereby improving image quality and improving the clarity of lens imaging. In addition, the use of glued lenses can also reduce the number of assembly components between the two lenses, simplify the assembly procedures in the lens manufacturing process, reduce costs, and reduce the sensitivity of lens units to tolerances such as tilt / eccentricity generated during the assembly process.

[0044] Optionally, the sixth lens L6 and the seventh lens L7 are cemented together to form a second cemented lens. Similarly, the sixth lens L6 and the seventh lens L7 are cemented together to effectively reduce the air space between the two lenses, thereby helping to reduce the overall length of the lens.

[0045] Optionally, the optical power of the first lens L1 is Optical power of fixed focal length lens Satisfies the relationship: The refractive index Nd1 of the first lens L1 satisfies the relationship: 1.71≤Nd1≤2.10. When the first lens L1 is made of a high refractive index material and the focal length is set within the above range, more light can enter the optical system, ensuring that the lens has a larger field of view angle range.

[0046] Optionally, the refractive power of the second lens L2 is Optical power of fixed focal length lens Satisfies the relationship: The refractive power of the third lens L3 Optical power of fixed focal length lens Satisfies the relationship: The refractive index Nd3 of the third lens L3 satisfies the relationship: 1.75≤Nd3≤2.10. When the focal lengths of the second lens L2 and the third lens L3 meet this range, it can not only effectively shrink the light, but also help correct the system aberration, thereby promoting the improvement of image quality; it is also conducive to realizing a miniaturized lens design.

[0047] Optionally, the refractive power of the fourth lens L4 is Optical power of fixed focal length lens Satisfies the relationship: Refractive power of the fifth lens L5 Optical power of fixed focal length lens Satisfies the relationship: Refractive power of the sixth lens L6 Optical power of fixed focal length lens Satisfies the relationship: The refractive power of the seventh lens L7 Optical power of fixed focal length lens Satisfies the relationship: When the optical powers of the fourth lens L4, the fifth lens L5, the sixth lens L6 and the seventh lens L7 meet this range, off-axis aberrations can be corrected and the imaging quality of the marginal field of view can be improved.

[0048] Optionally, the Abbe number Vd4 of the fourth lens L4, the Abbe number Vd5 of the fifth lens L5, the Abbe number Vd6 of the sixth lens L6, and the Abbe number Vd7 of the seventh lens L7 satisfy the following conditions: 1.00≤Vd5-Vd4≤38.95; 23.15≤Vd6-Vd7≤50.5. The fourth lens L4, the fifth lens L5, the sixth lens L6, and the seventh lens L7 use a combination of materials with different dispersion coefficients, which can compensate for the dispersion to achieve the purpose of achromatism, which is beneficial to improving the imaging performance of the optical system. The fourth lens L4 and the fifth lens L5 can be bonded by glue or supported by a spacer; the sixth lens L6 and the seventh lens L7 can be bonded by glue or supported by a spacer.

[0049] Optionally, the optical power of the eighth lens L8 is Optical power of fixed focal length lens Satisfies the relationship: Refractive power of the ninth lens L9 Optical power of fixed focal length lens Satisfies the relationship: When the optical powers of the eighth lens L8 and the ninth lens L9 meet this range, off-axis aberrations can be corrected, and performance such as the principal ray angle and distortion can be optimized.

[0050] Optionally, the refractive index Nd6 of the sixth lens L6, the refractive index Nd7 of the seventh lens L7, the refractive index Nd8 of the eighth lens L8, and the refractive index Nd9 of the ninth lens L9 satisfy: 2.98≤Nd6+Nd8≤3.20; 3.17≤Nd7+Nd9≤3.50. The sixth lens L6, the seventh lens L7, the eighth lens L8, and the ninth lens L9 use materials with different refractive indices, which can correct system aberrations and improve imaging quality.

[0051] Optionally, the total length TTL of the fixed-focus lens, the back focal length BFL of the fixed-focus lens, and the front focal length EFL of the fixed-focus lens satisfy the following relationship: 1.75≤EFL≤1.96; 0.05≤BFL / TTL≤0.14; 6.49≤(TTL-BFL) / EFL≤9.00. This ensures that the entire fixed-focus lens has a compact structure, high integration, and a short total length while also ensuring that there is sufficient installation space for the imaging sensor and the filter.

[0052] The technical solution of the embodiment of the present invention is to arrange in sequence along the optical axis from the object side to the image side a convex-concave first lens with negative power, a convex-concave second lens with negative power, a biconvex third lens with positive power, an aperture, a biconcave fourth lens with negative power, a biconvex fifth lens with positive power, a biconvex sixth lens with positive power, a convex-concave seventh lens with negative power, a biconvex eighth lens with positive power and a convex-concave ninth lens with negative power; wherein the first lens, the third lens, the fourth lens, the fifth lens, the second lens, the second lens and the second lens are arranged in sequence from the object side to the image side; The first lens is a glass spherical lens, and the second lens, the sixth lens, the seventh lens, the eighth lens and the ninth lens are all plastic aspherical lenses. This arrangement can reasonably match the optical focal length of each lens, as well as the material and surface shape of each lens, so as to achieve good imaging performance of the fixed-focus lens, so that its field of view angle is greater than 200°, and the total optical length satisfies TTL≤17mm, thereby enabling the fixed-focus lens to achieve the effects of small size, low cost and large field of view angle, so as to meet the current needs of various industries for the field of view angle, volume and cost of the lens.

[0053] The fixed-focus lens provided by the present invention is described below with reference to specific embodiments.

[0054] Table 1 Parameter table of each relational expression in Embodiment 1 to Embodiment 3

[0055]

[0056] Embodiment 1

[0057] Figure 1 is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 1 of the present invention. Figure 1 As shown, the fixed focus lens comprises: a convexo-concave first lens L1 with negative focal power, a convexo-concave second lens L2 with negative focal power, a biconvex third lens L3 with positive focal power, an aperture STO, a biconcave fourth lens L4 with negative focal power, a biconvex fifth lens L5 with positive focal power, a biconvex sixth lens L6 with positive focal power, a concave-convex seventh lens L7 with negative focal power, a biconvex eighth lens L8 with positive focal power, and a convexo-concave ninth lens L9 with negative focal power, which are arranged in sequence from the object side to the image side along the optical axis; wherein the first lens L1, the third lens L3, the fourth lens L4, and the fifth lens L5 are all glass spherical mirrors, and the second lens L2, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the ninth lens L9 are all plastic aspherical mirrors. wherein the aperture F# of the lens is 2.0, the image height Φ6mm corresponds to an angle of 200°, and the optical total axis length is 16.9mm. The fourth lens L4 and the fifth lens L5 are cemented together. The lens also includes a flat glass PL.

[0058] Table 2 Design values ​​of each lens in Example 1

[0059]

[0060]

[0061] The surface numbers S1-S20 in Table 2 are numbered according to the surface order of each lens, where "S1" represents the front surface of the first lens, "S2" represents the back surface of the first lens, and so on; "STO" represents the aperture of the lens; "IMA" represents the image plane of the lens; the radius of curvature represents the curvature of the lens surface, a positive value represents that the surface is bent toward the image plane, and a negative value represents that the surface is bent toward the object plane, where "Infinity" represents that the surface is a plane, the radius of curvature is infinite, and the distance is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light, and the space represents that the current position is air with a refractive index of 1; the Abbe number Vd represents the dispersion characteristics of the material between the current surface and the next surface to light, and the space represents that the current position is air; the semi-diameter represents the effective diameter of the light of the lens; the k value represents the numerical value of the cone coefficient of the aspheric surface.

[0062] Table 3 Aspheric coefficients of each aspheric lens in Example 1

[0063]

[0064]

[0065] The aspheric cone coefficient can be defined by the following aspheric formula, but is not limited to the following representation method:

[0066]

[0067] Among them, z is the axial vector height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the radius of curvature; k is the fitting cone coefficient; the 4th, 6th, 8th, 10th, 12th, and 14th order coefficients of the AF aspheric polynomial.

[0068] Figure 2 Schematic diagram of axial aberration of the fixed-focus lens provided in Embodiment 1 of the present invention. Figure 2 As shown in the figure, the vertical direction represents the normalization of the aperture, 0 represents the optical axis, and the vertical vertex represents the maximum pupil radius (0.4868mm); the horizontal direction represents the offset relative to the ideal focus, in millimeters (mm). The different linear curves in the figure represent different wavelengths of system imaging (436nm, 486nm, 546nm, 588nm, 656nm), which are represented by Figure 2It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this fixed-focus lens at each wavelength is well controlled and can meet the needs of wide spectrum applications.

[0069] Embodiment 2

[0070] Figure 3 is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 2 of the present invention. Figure 3 As shown, the fixed focus lens comprises: a convexo-concave first lens L1 with negative focal power, a convexo-concave second lens L2 with negative focal power, a biconvex third lens L3 with positive focal power, an aperture STO, a biconcave fourth lens L4 with negative focal power, a biconvex fifth lens L5 with positive focal power, a biconvex sixth lens L6 with positive focal power, a concave-convex seventh lens L7 with negative focal power, a biconvex eighth lens L8 with positive focal power, and a convexo-concave ninth lens L9 with negative focal power, which are arranged in sequence from the object side to the image side along the optical axis; wherein the first lens L1, the third lens L3, the fourth lens L4, and the fifth lens L5 are all glass spherical mirrors, and the second lens L2, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the ninth lens L9 are all plastic aspherical mirrors. wherein the aperture F# of the lens is 2.0, the image height Φ6.07mm corresponds to an angle of 200°, and the total optical axis length is 16.832mm. The fourth lens L4 and the fifth lens L5 are cemented together, and the sixth lens L6 and the seventh lens L7 are cemented together. The lens also includes a flat glass PL.

[0071] Table 4 Design values ​​of each lens in Example 2

[0072]

[0073]

[0074] The surface numbers S1-S19 in Table 4 are numbered according to the surface order of each lens, where "S1" represents the front surface of the first lens, "S2" represents the back surface of the first lens, and so on; "STO" represents the aperture of the lens; "IMA" represents the image plane of the lens; the radius of curvature represents the curvature of the lens surface, a positive value represents that the surface is bent toward the image plane, and a negative value represents that the surface is bent toward the object plane, where "Infinity" represents that the surface is a plane, the radius of curvature is infinite, and the distance is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light, and the space represents that the current position is air with a refractive index of 1; the Abbe number Vd represents the dispersion characteristics of the material between the current surface and the next surface to light, and the space represents that the current position is air; the semi-diameter represents the effective diameter of the light of the lens; the k value represents the numerical value of the cone coefficient of the aspheric surface.

[0075] Table 5 Aspheric coefficients of each aspheric lens in Example 2

[0076]

[0077] The aspheric cone coefficient can be defined by the following aspheric formula, but is not limited to the following representation method:

[0078]

[0079] Among them, z is the axial vector height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the radius of curvature; k is the fitting cone coefficient; the 4th, 6th, 8th, 10th, 12th, and 14th order coefficients of the AF aspheric polynomial.

[0080] Figure 4 Schematic diagram of axial aberration of the fixed-focus lens provided in Embodiment 2 of the present invention. Figure 4 As shown in the figure, the vertical direction represents the normalization of the aperture, 0 represents the optical axis, and the vertical vertex represents the maximum pupil radius (0.4575mm); the horizontal direction represents the offset relative to the ideal focus, in millimeters (mm). The different linear curves in the figure represent different wavelengths of system imaging (436nm, 486nm, 546nm, 588nm, 656nm), which are represented by Figure 4 It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this fixed-focus lens at each wavelength is well controlled and can meet the needs of wide spectrum applications.

[0081] Embodiment 3

[0082] Figure 5 is a schematic diagram of the structure of a fixed-focus lens provided in Embodiment 3 of the present invention. Figure 5As shown, the fixed focus lens comprises: a convexo-concave first lens L1 with negative focal power, a convexo-concave second lens L2 with negative focal power, a biconvex third lens L3 with positive focal power, an aperture STO, a biconcave fourth lens L4 with negative focal power, a biconvex fifth lens L5 with positive focal power, a biconvex sixth lens L6 with positive focal power, a concave-convex seventh lens L7 with negative focal power, a biconvex eighth lens L8 with positive focal power, and a convexo-concave ninth lens L9 with negative focal power, which are arranged in sequence from the object side to the image side along the optical axis; wherein the first lens L1, the third lens L3, the fourth lens L4, and the fifth lens L5 are all glass spherical mirrors, and the second lens L2, the sixth lens L6, the seventh lens L7, the eighth lens L8, and the ninth lens L9 are all plastic aspherical mirrors. wherein the aperture F# of the lens is 2.0, the image height Φ6.1mm corresponds to an angle of 200°, and the total optical axis length is 16.117mm. The lens also includes flat glass PL.

[0083] Table 6 Design values ​​of each lens in Example 3

[0084]

[0085]

[0086] The surface numbers S1-S21 in Table 6 are numbered according to the surface order of each lens, where "S1" represents the front surface of the first lens, "S2" represents the back surface of the first lens, and so on; "STO" represents the aperture of the lens; "IMA" represents the image plane of the lens; the radius of curvature represents the curvature of the lens surface, a positive value represents that the surface is bent toward the image plane, and a negative value represents that the surface is bent toward the object plane, where "Infinity" represents that the surface is a plane, the radius of curvature is infinite, and the distance is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light, and the space represents that the current position is air with a refractive index of 1; the Abbe number Vd represents the dispersion characteristics of the material between the current surface and the next surface to light, and the space represents that the current position is air; the semi-diameter represents the effective diameter of the light of the lens; the k value represents the numerical value of the cone coefficient of the aspheric surface.

[0087] Table 7 Aspheric coefficients of each aspheric lens in Example 3

[0088]

[0089] The aspheric cone coefficient can be defined by the following aspheric formula, but is not limited to the following representation method:

[0090]

[0091] Among them, z is the axial vector height of the aspheric surface in the Z direction; r is the height of the aspheric surface; c is the curvature of the fitted sphere, which is the inverse of the radius of curvature; k is the fitting cone coefficient; the 4th, 6th, 8th, 10th, 12th, and 14th order coefficients of the AF aspheric polynomial.

[0092] Figure 6 Schematic diagram of axial aberration of the fixed-focus lens provided in Embodiment 3 of the present invention. Figure 6 As shown in the figure, the vertical direction represents the normalization of the aperture, 0 represents the optical axis, and the vertical vertex represents the maximum pupil radius (0.5008mm); the horizontal direction represents the offset relative to the ideal focus, in millimeters (mm). The different linear curves in the figure represent different wavelengths of system imaging (436nm, 486nm, 546nm, 588nm, 656nm), which are represented by Figure 6 It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.05mm, +0.05mm), indicating that the spherical aberration of this fixed-focus lens at each wavelength is well controlled and can meet the needs of wide spectrum applications.

[0093] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0094] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A fixed-focus lens, characterized in that: include: Arranged in sequence from the object side to the image side along the optical axis are a convex-concave first lens with negative power, a convex-concave second lens with negative power, a biconvex third lens with positive power, an aperture, a biconcave fourth lens with negative power, a biconvex fifth lens with positive power, a biconvex sixth lens with positive power, a convex-concave seventh lens with negative power, a biconvex eighth lens with positive power, and a convex-concave ninth lens with negative power; Among them, the first lens, the third lens, the fourth lens, and the fifth lens are all glass spherical lenses, and the second lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens are all plastic aspherical lenses.

2. The fixed-focus lens according to claim 1, characterized in that: The fourth lens and the fifth lens are cemented together to form a first cemented lens.

3. The fixed-focus lens according to claim 2, characterized in that: The sixth lens and the seventh lens are cemented together to form a second cemented lens.

4. The fixed-focus lens according to any one of claims 1 to 3, characterized in that: The focal power φ1 of the first lens and the focal power φ of the fixed-focus lens satisfy the relationship: -0.45≤φ1 / φ≤-0.35; the refractive index Nd1 of the first lens satisfies the relationship: 1.71≤Nd1≤2.

10.

5. The fixed-focus lens according to any one of claims 1 to 3, characterized in that: The focal power φ2 of the second lens and the focal power φ of the fixed-focus lens satisfy the relationship: -0.36≤φ2 / φ≤-0.23; The focal power φ3 of the third lens and the focal power φ of the fixed-focus lens satisfy the relationship: 0.23≤φ3 / φ≤0.43; the refractive index Nd3 of the third lens satisfies the relationship: 1.75≤Nd3≤2.

10.

6. The fixed-focus lens according to any one of claims 1 to 3, characterized in that: The focal power φ4 of the fourth lens and the focal power φ of the fixed-focus lens satisfy the relationship: -0.92≤φ4 / φ≤-0.45; The focal power φ5 of the fifth lens and the focal power φ of the fixed-focus lens satisfy the relationship: 0.49≤φ5 / φ≤0.77; The focal power φ6 of the sixth lens and the focal power φ of the fixed-focus lens satisfy the relationship: 0.35≤φ6 / φ≤0.47; The optical power φ7 of the seventh lens and the optical power φ of the fixed-focus lens satisfy the relationship: -0.26≤φ7 / φ≤-0.

14.

7. The fixed-focus lens according to any one of claims 1 to 3, characterized in that: The Abbe number Vd4 of the fourth lens, the Abbe number Vd5 of the fifth lens, the Abbe number Vd6 of the sixth lens, and the Abbe number Vd7 of the seventh lens satisfy the following conditions: 1.00≤Vd5-Vd4≤38.95; 23.15≤Vd6-Vd7≤50.

5.

8. The fixed-focus lens according to any one of claims 1 to 3, characterized in that: The focal power φ8 of the eighth lens and the focal power φ of the fixed-focus lens satisfy the relationship: 0.18≤φ8 / φ≤0.27; The optical power φ9 of the ninth lens and the optical power φ of the fixed-focus lens satisfy the relationship: -0.17≤φ9 / φ≤-0.

10.

9. The fixed-focus lens according to any one of claims 1 to 3, characterized in that: A refractive index Nd6 of the sixth lens, a refractive index Nd7 of the seventh lens, a refractive index Nd8 of the eighth lens, and a refractive index Nd9 of the ninth lens satisfy the following conditions: 2.98≤Nd6+Nd8≤3.20; 3.17≤Nd7+Nd9≤3.

50.

10. The fixed-focus lens according to any one of claims 1 to 3, characterized in that: The total length TTL of the fixed-focus lens, the back focal length BFL of the fixed-focus lens, and the front focal length EFL of the fixed-focus lens satisfy the relationship: 1.75≤EFL≤1.96; 0.05≤BFL / TTL≤0.14; 6.49≤(TTL-BFL) / EFL≤9.00.

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