A fixed focus lens

Abstract

This invention discloses a fixed-focus lens, comprising a first lens, a second lens, a third lens, an aperture stop, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the optical axis from the object side to the image side. The first lens is a negative-power plastic aspherical lens; the second lens is a negative-power plastic aspherical lens; the third lens is a positive-power glass spherical lens; the fourth lens is a positive-power glass spherical lens; the fifth lens is a negative-power glass spherical lens; the sixth lens is a positive-power plastic aspherical lens; and the seventh lens is a negative-power plastic aspherical lens. The fourth and fifth lenses form a negative-power cemented doublet lens group. The fixed-focus lens provided by this invention achieves an imaging resolution of 8 megapixels, a maximum aperture of F1.02, and can be matched with a 1 / 1.8″ target surface imaging chip, meeting the application requirements of large aperture, large target surface, low cost, and compact structure.

Description

Technical Field

[0001] This invention relates to the field of optical device technology, and more particularly to a fixed-focus lens. Background Technology

[0002] Security surveillance cameras commonly use infrared illumination to enhance image quality in low-light and nighttime conditions. However, this method suffers from drawbacks such as a small imaging range and significant color distortion. To achieve better nighttime imaging, the demand for large-aperture lenses is increasing.

[0003] Large-aperture fixed-focus lenses, due to their large light transmission, wide depth of field, and high image quality, can meet the needs of security monitoring. However, most existing fixed-focus surveillance lenses have apertures of F1.6 or larger, resulting in limited light transmission in low-light environments, which prevents them from achieving high-resolution surveillance images. Furthermore, existing fixed-focus surveillance lenses are typically paired with 1 / 2.7-inch imaging sensors, resulting in a small sensor area. In addition, existing large-aperture lenses generally suffer from high cost and large size, making it impossible to simultaneously meet the security monitoring requirements of large aperture, large sensor area, low cost, and compact structure. Summary of the Invention

[0004] This invention provides a fixed-focus lens that achieves a large aperture, large focal length, low cost, and compact structure.

[0005] The present invention provides a fixed-focus lens, comprising a first lens, a second lens, a third lens, an aperture stop, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the optical axis from the object side to the image side;

[0006] The first lens is a plastic aspherical lens with negative optical power;

[0007] The second lens is a plastic aspherical lens with negative optical power;

[0008] The third lens is a glass spherical lens with positive optical power;

[0009] The fourth lens is a glass spherical lens with positive optical power;

[0010] The fifth lens is a glass spherical lens with negative optical power;

[0011] The sixth lens is a plastic aspherical lens with positive optical power;

[0012] The seventh lens is a plastic aspherical lens with negative optical power;

[0013] The fourth lens and the fifth lens form a cemented doublet lens group, which has negative optical power.

[0014] Optionally, 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, the optical power of the seventh lens is φ7, and the optical power of the fixed-focus lens is φ, wherein:

[0015] -0.448≤φ1 / φ≤-0.408;-0.42≤φ2 / φ≤-0.31;

[0016] 0.524≤φ3 / φ≤0.712; 0.672≤φ4 / φ≤0.755;

[0017] -0.987≤φ5 / φ≤-0.889;1.027≤φ6 / φ≤1.133;

[0018] -0.422≤φ7 / φ≤-0.323.

[0019] Optionally, the optical power of the cemented doublet lens group is φ8, and the optical power of the fixed-focus lens is φ, wherein -0.05≤φ8 / φ≤-0.012.

[0020] Optionally, the object-side surface of the first lens is convex, and the image-side surface of the first lens is concave.

[0021] The object-side surface of the second lens is concave, and the image-side surface of the second lens is convex.

[0022] The object-side surface of the third lens is convex, and the image-side surface of the third lens is convex.

[0023] The object-side surface of the fourth lens is convex, and the image-side surface of the fourth lens is convex.

[0024] The object-side surface of the fifth lens is concave, and the image-side surface of the fifth lens is also concave.

[0025] The object-side surface of the sixth lens is convex, and the image-side surface of the sixth lens is convex.

[0026] The object-side surface of the seventh lens is convex, and the image-side surface of the seventh lens is concave.

[0027] Optionally, the refractive index of the third lens is Nd3, where Nd3 > 1.6.

[0028] Optionally, the Abbe number of the fourth lens is Vd4, where Vd4 > 58.

[0029] Optionally, the image plane diameter of the fixed-focus lens is IC, and the entrance pupil diameter of the fixed-focus lens is EPD, wherein 0.96≤IC / EPD≤1.24.

[0030] Optionally, the image plane diameter of the fixed-focus lens is IC, and the total optical length of the fixed-focus lens is TTL, wherein 0.25≤IC / TTL≤0.34.

[0031] Optionally, the back focal length of the fixed-focus lens is BFL, and the total optical length of the fixed-focus lens is TTL, wherein 0.15 <BFL / TTL<0.35。

[0032] Optionally, the fixed-focus lens may also include a filter;

[0033] The filter is located on the image-side side of the seventh lens.

[0034] The fixed-focus lens provided in this invention consists of three glass spherical lenses and four plastic aspherical lenses. Along the optical axis, from the object side to the image side, it employs a structure of single lens, single lens, single lens, double lens, single lens, and single lens. By rationally combining the materials and optical power of each lens, an imaging resolution of 8 megapixels is achieved, exhibiting excellent imaging performance. Simultaneously, this fixed-focus lens has a maximum aperture of F1.02, can be matched with a 1 / 1.8″ sensor chip, and has a compact structure. Since the cost of plastic lenses is far lower than that of glass lenses, the use of a glass-plastic hybrid material ensures good resolution in high and low temperature environments ranging from -40℃ to +80℃ while effectively controlling the cost of the fixed-focus lens. This achieves a fixed-focus lens that balances a large aperture, large sensor surface area, low cost, and small size.

[0035] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the structure of a fixed-focus lens provided in an embodiment of the present invention;

[0038] Figure 2 This is a spherical aberration curve of a fixed-focus lens provided in Embodiment 1 of the present invention;

[0039] Figure 3 This is a field curvature distortion diagram of a fixed-focus lens provided in Embodiment 1 of the present invention;

[0040] Figure 4 This is a schematic diagram of the fixed-focus lens provided in Embodiment 2 of the present invention;

[0041] Figure 5 This is a spherical aberration curve of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0042] Figure 6 This is a field curvature distortion diagram of a fixed-focus lens provided in Embodiment 2 of the present invention;

[0043] Figure 7 This is a schematic diagram of the fixed-focus lens provided in Embodiment 3 of the present invention;

[0044] Figure 8 This is a spherical aberration curve of a fixed-focus lens provided in Embodiment 3 of the present invention;

[0045] Figure 9 This is a field curvature distortion diagram of a fixed-focus lens provided in Embodiment 3 of the present invention. Detailed Implementation

[0046] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0047] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0048] Figure 1 This is a schematic diagram of a fixed-focus lens provided in an embodiment of the present invention. The embodiment of the present invention can be applied to security monitoring scenarios, but is not limited thereto.

[0049] like Figure 1As shown, the fixed-focus lens provided in this embodiment of the invention includes a first lens 110, a second lens 120, a third lens 130, an aperture stop 100, a fourth lens 140, a fifth lens 150, a sixth lens 160, and a seventh lens 170 arranged sequentially along the optical axis from the object side to the image side. The first lens 110 is a plastic aspherical lens with negative optical power, the second lens 120 is a plastic aspherical lens with negative optical power, the third lens 130 is a glass spherical lens with positive optical power, the fourth lens 140 is a glass spherical lens with positive optical power, the fifth lens 150 is a glass spherical lens with negative optical power, the sixth lens 160 is a plastic aspherical lens with positive optical power, and the seventh lens 170 is a plastic aspherical lens with negative optical power. The fourth lens 140 and the fifth lens 150 form a cemented doublet lens group 200, which has negative optical power.

[0050] Specifically, optical power is equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam; it characterizes the ability of an optical system to deflect light. The larger the absolute value of the optical power, the stronger its ability to bend light; the smaller the absolute value, the weaker its ability to bend light. When the optical power is positive, the refraction of light is converging; when the optical power is negative, the refraction of light is diverging. Optical power can be used to characterize a single refractive surface of a lens (i.e., one surface of the lens), a single lens, or a system formed by multiple lenses (i.e., a lens group).

[0051] In the fixed-focus lens provided in this embodiment, each lens can be fixed in a lens barrel ( Figure 1 (Not shown in the image) In this system, the first lens 110 is a plastic aspherical lens with negative optical power, which can make the object-side light rays enter the imaging system smoothly and reduce the proportion of high-order aberrations.

[0052] Setting the second lens 120 to a plastic aspherical lens with negative optical power can diffuse light at a relatively gentle angle, which is beneficial to achieving the large aperture characteristics of the system.

[0053] The third lens 130 is a glass spherical lens with positive optical power. By using a material with a higher refractive index, the light rays from each field of view can be drawn into the aperture stop 100 at a smaller angle, which can effectively reduce the aberrations related to the field of view.

[0054] The fourth lens 140 is a glass spherical lens with positive optical power, which allows light to contract at a gentle angle after passing through the aperture 100. Furthermore, since the fourth lens 140 is close to the aperture 100, the intersection points of light rays in different fields of view at different apertures of the lens are similar, which is beneficial for the correction of chromatic aberration in the system.

[0055] The fifth lens 150 is set as a glass spherical lens with negative optical power. By using a high-refractive-index negative lens, the light rays in the system can be deflected excessively at small angles.

[0056] The fifth lens 150 and the fourth lens 140 are further cemented together to form a cemented doublet lens group 200, which can correct chromatic aberration of the system. At the same time, it can effectively reduce the air gap between the fifth lens 150 and the fourth lens 140, thereby helping to reduce the overall length of the lens. Under the premise of compact structure, it can improve resolution, optimize optical performance such as distortion, and reduce light loss caused by reflection between lenses, thereby improving illumination, thus improving image quality and enhancing the clarity of the lens image.

[0057] By setting the cemented doublet lens group 200 to have a negative optical power, the cemented doublet lens group 200 can bear a smaller optical power, but plays a great role in correcting the chromatic aberration of the system.

[0058] Setting the sixth lens 160 to a plastic aspherical lens with positive optical power ensures smooth light deflection and reduces the introduction of advanced aberrations.

[0059] The seventh lens 170 is a plastic aspherical lens with negative optical power, which can compensate for the residual aberrations of the system and make the system aberrations more balanced.

[0060] The fixed-focus lens provided in this invention consists of three glass spherical lenses and four plastic aspherical lenses. Along the optical axis, from the object side to the image side, it employs a structure of single lens, single lens, single lens, double lens, single lens, and single lens. By rationally combining the materials and optical power of each lens, an imaging resolution of 8 megapixels is achieved, exhibiting excellent imaging performance. Simultaneously, this fixed-focus lens has a maximum aperture of F1.02, can be matched with a 1 / 1.8″ sensor chip, and has a compact structure. Since the cost of plastic lenses is far lower than that of glass lenses, the use of a glass-plastic hybrid material ensures good resolution in high and low temperature environments ranging from -40℃ to +80℃ while effectively controlling the cost of the fixed-focus lens. This achieves a fixed-focus lens that balances a large aperture, large sensor surface area, low cost, and small size.

[0061] As one feasible implementation, the optical power of the first lens 110 is φ1, the optical power of the second lens 120 is φ2, the optical power of the third lens 130 is φ3, the optical power of the fourth lens 140 is φ4, the optical power of the fifth lens 150 is φ5, the optical power of the sixth lens 160 is φ6, the optical power of the seventh lens 170 is φ7, and the optical power of the fixed-focus lens is φ, wherein -0.448≤φ1 / φ≤-0.408; -0.42≤φ2 / φ≤-0.31; 0.524≤φ3 / φ≤0.712; 0.672≤φ4 / φ≤0.755;

[0062] -0.987≤φ5 / φ≤-0.889;1.027≤φ6 / φ≤1.133;-0.422≤φ7 / φ≤-0.323;

[0063] By setting the optical power φ1 of the first lens 110 to satisfy -0.448≤φ1 / φ≤-0.408, the object-side light rays can be smoothly received into the imaging system, reducing the proportion of high-order aberrations.

[0064] By setting the optical power φ2 of the second lens 120 to satisfy -0.42≤φ2 / φ≤-0.31, the light can be diffused at a relatively gentle angle, which is beneficial to the realization of the system's large aperture characteristics.

[0065] By setting the optical power φ3 of the third lens 130 to satisfy 0.524≤φ3 / φ≤0.712, the light rays from each field of view can be drawn into the aperture stop 100 at a smaller angle, which can effectively reduce the aberrations related to the field of view.

[0066] By setting the optical power φ4 of the fourth lens 140 to satisfy 0.672≤φ4 / φ≤0.755, the light can be contracted at a gentle angle after passing through the aperture 100. Furthermore, since the fourth lens 140 is close to the aperture 100, the intersection points of the light rays in each field of view at different apertures of the lens are similar, which is beneficial for the correction of chromatic aberration in the system.

[0067] By setting the optical power φ5 of the fifth lens 150 to satisfy -0.987≤φ5 / φ≤-0.889, the light in the system can be deflected excessively at small angles.

[0068] By setting the optical power φ6 of the sixth lens 160 to satisfy 1.027≤φ6 / φ≤1.133, the light deflection of the system can be guaranteed to be smooth, reducing the introduction of higher aberrations.

[0069] By setting the optical power of the seventh lens 170 to satisfy -0.422≤φ7 / φ≤-0.323, the residual aberrations of the system can be compensated, making the system aberrations more balanced.

[0070] In this embodiment, by reasonably setting the optical power of each lens, it is beneficial to realize a fixed-focus lens with a large aperture, large target area, low cost and compact structure, so as to meet the needs of security monitoring.

[0071] As a feasible implementation, the optical power of the cemented doublet lens group 200 is φ8, and the optical power of the fixed-focus lens is φ, wherein -0.05≤φ8 / φ≤-0.012.

[0072] Specifically, by setting the optical power φ8 of the cemented doublet lens group 200 to satisfy -0.05≤φ8 / φ≤-0.012, the cemented doublet lens group 200 can handle a smaller optical power, which is beneficial for correcting the chromatic aberration of the system.

[0073] As a possible implementation method, such as Figure 1 As shown, the object-side surface of the first lens 110 is convex, and the image-side surface of the first lens 110 is concave; the object-side surface of the second lens 120 is concave, and the image-side surface of the second lens 120 is convex; the object-side surface of the third lens 130 is convex, and the image-side surface of the third lens 130 is convex; the object-side surface of the fourth lens 140 is convex, and the image-side surface of the fourth lens 140 is convex; the object-side surface of the fifth lens 150 is concave, and the image-side surface of the fifth lens 150 is concave; the object-side surface of the sixth lens 160 is convex, and the image-side surface of the sixth lens 160 is convex; the object-side surface of the seventh lens 170 is convex, and the image-side surface of the seventh lens 170 is concave.

[0074] By setting the first lens 110 as a meniscus negative lens with a convex front and a concave back, it helps to smoothly receive object-side light into the imaging system and reduce the proportion of high-order aberrations.

[0075] By setting the second lens 120 as a meniscus negative lens that is concave in the front and convex in the back, and symmetrically arranged with the first lens 110, this layout is beneficial to improving the image quality of the system.

[0076] By setting the third lens 130 as a biconvex lens with positive optical power, it helps to reduce the light rays in each field of view by narrowing the aperture stop 100 at a smaller angle, which can effectively reduce the aberrations related to the field of view.

[0077] By setting the fourth lens 140 as a convex lens with positive optical power, it helps the light to contract at a gentle angle after passing through the aperture 100. Furthermore, since the fourth lens 140 is close to the aperture 100, the intersection points of the light rays in each field of view at different apertures of the lens are similar, which is beneficial for the correction of chromatic aberration in the system.

[0078] By setting the fifth lens 150 as a concave lens with negative optical power, it helps to deflect the system light excessively at small angles.

[0079] By setting the sixth lens 160 as a convex lens with positive optical power, it helps to ensure that the light deflection of the system is smooth and reduces the introduction of advanced aberrations.

[0080] By setting the object-side surface of the seventh lens 170 to include a convex surface and the image-side surface of the seventh lens 170 to include a concave surface, the residual aberrations of the system can be compensated, making the system aberrations more balanced.

[0081] In this embodiment, by reasonably setting the curvature direction of each lens surface, while ensuring that the optical power of each lens meets the optical power requirements of the above embodiment, and realizing a fixed-focus lens with large aperture, large target surface, low cost and compact structure, it also helps to improve the integration of the fixed-focus lens, ensure the compact structure of the entire fixed-focus lens, and reduce the overall length of the fixed-focus lens.

[0082] As a possible implementation, the refractive index of the third lens 130 is Nd3, where Nd3 > 1.6.

[0083] By using a high-refractive-index material for the third lens 130, the light rays from each field of view are drawn into the system aperture 100 at a smaller angle, which can effectively reduce the aberrations related to the field of view.

[0084] As a possible implementation, the Abbe number of the fourth lens 140 is Vd4, where Vd4 > 58.

[0085] The fourth lens 140 is located near the aperture stop. The intersection points of the light rays in each field of view at different apertures of the lens are similar. Therefore, the fourth lens 140 is extremely beneficial for correcting the chromatic aberration of the system. In this embodiment, by setting the fourth lens 140 to use a large Abbe number material, the chromatic aberration can be reduced to the greatest extent.

[0086] As a feasible implementation method, the image plane diameter of the fixed-focus lens is IC, and the entrance pupil diameter of the fixed-focus lens is EPD, wherein 0.96≤IC / EPD≤1.24.

[0087] By setting the image plane diameter IC and the entrance pupil diameter EPD to satisfy 0.96≤IC / EPD≤1.24, the fixed-focus lens can control the entrance pupil diameter of the optical system while satisfying the requirements of large image plane and high-quality imaging, ensuring sufficient light at the edge of the large image plane imaging system and improving the brightness of the image plane.

[0088] As a feasible implementation method, the image plane diameter of the fixed-focus lens is IC, and the total optical length of the fixed-focus lens is TTL, wherein 0.25≤IC / TTL≤0.34.

[0089] The distance from the center of the optical axis on the object side of the first lens 110 to the image plane is the total optical length TTL. By setting the image plane diameter IC and the total optical length TTL to satisfy 0.25≤IC / TTL≤0.34, the fixed-focus lens can have a larger image plane and a smaller volume, ensuring that the optical system has better imaging quality and a clearer image while having a smaller volume.

[0090] As one feasible implementation, the back focal length of the fixed-focus lens is BFL, and the total optical length of the fixed-focus lens is TTL, where 0.15 <BFL / TTL<0.35。

[0091] In this context, the distance from the center of the optical axis on the object side of the first lens 110 to the image plane is the total optical length TTL, and the distance from the center of the optical axis on the image side of the seventh lens 170 to the image plane BFL can be understood as the back focal length of a fixed-focus lens.

[0092] In this embodiment, by setting the back focal length BFL and the total optical length TTL to satisfy 0.15 < BFL / TTL < 0.35, it is beneficial to compress the total length of the lens, and at the same time, it can ensure that there is sufficient installation space for the imaging sensor and the flat filter.

[0093] As a feasible implementation manner, as Figure 1 shown, the fixed-focus lens provided by the embodiment of the present invention further includes a filter 300, and the filter 300 is located on the image side of the seventh lens 170.

[0094] Among them, by arranging the filter 300 on the image side of the seventh lens 170, unnecessary stray light can be filtered out, thereby improving the image quality of the fixed-focus lens. For example, by filtering out infrared light through the filter 300 during the day, the imaging quality of the fixed-focus lens can be improved. At the same time, the filter 300 can also protect the imaging sensor.

[0095] The following further describes specific embodiments of the fixed-focus lens applicable to the above embodiments with reference to the drawings.

[0096] Embodiment 1

[0097] Continuing to refer to Figure 1 , the fixed-focus lens provided by Embodiment 1 of the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, and a seventh lens 170 arranged in sequence from the object side to the image side along the optical axis. Among them, the fourth lens 140 and the fifth lens 150 form a doublet lens group 200, the aperture stop 100 is located in the optical path between the third lens 130 and the fourth lens 140, and the filter 300 is located on the image side of the seventh lens 170.

[0098] Table 1 details the specific optical physical parameters of each lens in the fixed-focus lens provided by Embodiment 1 of the present invention in a feasible implementation manner. The fixed-focus lens in Table 1 corresponds to Figure 1 the fixed-focus lens shown.

[0099] Table 1 Design values of the optical physical parameters of the fixed-focus lens

[0100]

[0101] In Table 1, the surface numbers are assigned according to the surface sequence of each lens. For example, surface number "S1" represents the object side of the first lens 110, surface number "S2" represents the image side of the first lens 110, and so on. "STO" represents the aperture 100 of the fixed-focus lens. The radius of curvature represents the curvature of the lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "PL" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance between the current surface and the next surface. The refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air and the refractive index is 1. The Abbe number (Vd) represents the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current position is air. The k value represents the magnitude of the fitting conic coefficient of the aspherical surface. IMA represents the image plane.

[0102] Its aspherical conic coefficient can be defined by the following equation for the shape of the aspherical surface, but is not limited to the following representation:

[0103]

[0104] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; and AF are the coefficients of the 4th, 6th, 8th, 10th, 12th, and 14th order terms of the aspherical polynomial.

[0105] For example, Table 2 details the aspherical coefficients of each lens in this embodiment one of feasible implementations.

[0106] Table 2 Design values ​​of aspherical coefficients for various lenses in fixed-focus lenses

[0107]

[0108] The fixed-focus lens provided in this embodiment has a focal length f of 8.41mm and an F# of 1.02.

[0109] Furthermore, Figure 2 The spherical aberration curve of the fixed-focus lens provided in Embodiment 1 of the present invention is shown below. Figure 2 As shown, the vertical direction represents the normalized aperture, 0 indicates it is on the optical axis, and the vertical vertex represents the maximum pupil radius; 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 the system imaging, determined by... Figure 2It can be seen that the axial aberrations at different wavelengths (0.436μm, 0.486μm, 0.546μm, 0.588μm and 0.656μm) are all controlled within the range of (-0.03mm, +0.03mm), indicating that the spherical aberration of this fixed-focus lens is well controlled at each wavelength, which can meet the requirements of wide-spectrum applications.

[0110] Figure 3 The field curvature distortion diagram of the fixed-focus lens provided in Embodiment 1 of the present invention is as follows: Figure 3 As shown, in the coordinate system on the left, the horizontal coordinate represents the magnitude of the field curvature, in mm; the vertical coordinate represents the normalized image height, which has no unit; from Figure 3 As can be seen, the fixed-focus lens provided in this embodiment effectively controls the field curvature of light from wavelengths of 0.436μm to 0.656μm, meaning that during imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal axis represents the magnitude of distortion (F-Tan (Theta)) in %; the vertical axis represents the normalized image height, which has no unit; from Figure 3 As can be seen, the distortion of the fixed-focus lens provided in this embodiment has been well corrected, and the imaging distortion is small.

[0111] Example 2

[0112] Figure 4 This is a schematic diagram of the fixed-focus lens provided in Embodiment 2 of the present invention, as shown below. Figure 4 As shown, the fixed-focus lens provided in Embodiment 2 of the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, and a seventh lens 170 arranged sequentially along the optical axis from the object side to the image side. The fourth lens 140 and the fifth lens 150 form a cemented doublet lens group 200. The aperture stop 100 is located in the optical path between the third lens 130 and the fourth lens 140. The filter 300 is located on the image side side of the seventh lens 170.

[0113] Table 3 details the specific optical physical parameters of each lens in the fixed-focus lens provided in Embodiment 2 of the present invention, according to a feasible implementation method.

[0114] Table 3 Design values ​​of optical physical parameters for fixed-focus lenses

[0115]

[0116] In Table 3, the surface numbers are assigned according to the surface sequence of each lens. For example, surface number "S1" represents the object side of the first lens 110, surface number "S2" represents the image side of the first lens 110, and so on. "STO" represents the aperture 100 of the fixed-focus lens. The radius of curvature represents the curvature of the lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "PL" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance between the current surface and the next surface. The refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air and the refractive index is 1. The Abbe number (Vd) represents the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current position is air. The k value represents the magnitude of the fitting conic coefficient of the aspherical surface. IMA represents the image plane.

[0117] Its aspherical conic coefficient can be defined by the following equation for the shape of the aspherical surface, but is not limited to the following representation:

[0118]

[0119] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; and AF are the coefficients of the 4th, 6th, 8th, 10th, 12th, and 14th order terms of the aspherical polynomial.

[0120] For example, Table 4 details the aspherical coefficients of each lens in this embodiment two according to a feasible implementation.

[0121] Table 4 Design values ​​of aspherical coefficients for various lenses in fixed-focus lenses

[0122]

[0123] The fixed-focus lens provided in this embodiment has a focal length f of 8.40mm and an F# of 1.04.

[0124] Furthermore, Figure 5 The spherical aberration curve of the fixed-focus lens provided in Embodiment 2 of the present invention is shown below. Figure 5 As shown, the vertical direction represents the normalized aperture, 0 indicates it is on the optical axis, and the vertical vertex represents the maximum pupil radius; 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 the system imaging, determined by... Figure 5It can be seen that the axial aberrations at different wavelengths (0.436μm, 0.486μm, 0.546μm, 0.588μm and 0.656μm) are all controlled within the range of (-0.025mm, +0.025mm), indicating that the spherical aberration of this fixed-focus lens is well controlled at each wavelength, which can meet the requirements of wide-spectrum applications.

[0125] Figure 6 The field curvature distortion diagram of the fixed-focus lens provided in Embodiment 2 of the present invention is shown below. Figure 6 As shown, in the coordinate system on the left, the horizontal coordinate represents the magnitude of the field curvature, in mm; the vertical coordinate represents the normalized image height, which has no unit; from Figure 6 As can be seen, the fixed-focus lens provided in this embodiment effectively controls the field curvature of light from wavelengths of 0.436μm to 0.656μm, meaning that during imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal axis represents the magnitude of distortion (F-Tan (Theta)) in %; the vertical axis represents the normalized image height, which has no unit; from Figure 6 As can be seen, the distortion of the fixed-focus lens provided in this embodiment has been well corrected, and the imaging distortion is small.

[0126] Example 3

[0127] Figure 7 This is a schematic diagram of the fixed-focus lens provided in Embodiment 3 of the present invention, as shown below. Figure 7 As shown, the fixed-focus lens provided in Embodiment 3 of the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens 160, and a seventh lens 170 arranged sequentially along the optical axis from the object side to the image side. The fourth lens 140 and the fifth lens 150 form a cemented doublet lens group 200. The aperture stop 100 is located in the optical path between the third lens 130 and the fourth lens 140. The filter 300 is located on the image side side of the seventh lens 170.

[0128] Table 5 details the specific optical physical parameters of each lens in the fixed-focus lens provided in Embodiment 3 of the present invention, according to a feasible implementation method.

[0129] Table 5 Design values ​​of optical physical parameters for fixed-focus lenses

[0130]

[0131] In Table 5, the surface numbers are assigned according to the surface sequence of each lens. For example, surface number "S1" represents the object side of the first lens 110, surface number "S2" represents the image side of the first lens 110, and so on. "STO" represents the aperture 100 of the fixed-focus lens. The radius of curvature represents the curvature of the lens surface. A positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "PL" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance between the current surface and the next surface. The refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air and the refractive index is 1. The Abbe number (Vd) represents the dispersion characteristics of the material between the current surface and the next surface. A blank space indicates that the current position is air. The k value represents the magnitude of the fitting conic coefficient of the aspherical surface. IMA represents the image plane.

[0132] Its aspherical conic coefficient can be defined by the following equation for the shape of the aspherical surface, but is not limited to the following representation:

[0133]

[0134] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the coefficient of the fitted cone; and AF are the coefficients of the 4th, 6th, 8th, 10th, 12th, and 14th order terms of the aspherical polynomial.

[0135] For example, Table 6 details the aspherical coefficients of each lens in this embodiment three according to a feasible implementation.

[0136] Table 6 Design values ​​of aspherical coefficients for various lenses in fixed-focus lenses

[0137]

[0138] The fixed-focus lens provided in this embodiment has a focal length f of 8.41mm and an F# of 1.02.

[0139] Furthermore, Figure 8 The spherical aberration curve of the fixed-focus lens provided in Embodiment 3 of the present invention is shown below. Figure 8 As shown, the vertical direction represents the normalized aperture, 0 indicates it is on the optical axis, and the vertical vertex represents the maximum pupil radius; 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 the system imaging, determined by... Figure 8It can be seen that the axial aberrations at different wavelengths (0.436μm, 0.486μm, 0.546μm, 0.588μm and 0.656μm) are all controlled within the range of (-0.025mm, +0.025mm), indicating that the spherical aberration of this fixed-focus lens is well controlled at each wavelength, which can meet the requirements of wide-spectrum applications.

[0140] Figure 9 The field curvature distortion diagram of the fixed-focus lens provided in Embodiment 3 of the present invention is shown below. Figure 9 As shown, in the coordinate system on the left, the horizontal coordinate represents the magnitude of the field curvature, in mm; the vertical coordinate represents the normalized image height, which has no unit; from Figure 9 As can be seen, the fixed-focus lens provided in this embodiment effectively controls the field curvature of light from wavelengths of 0.436μm to 0.656μm, meaning that during imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal axis represents the magnitude of distortion (F-Tan (Theta)) in %; the vertical axis represents the normalized image height, which has no unit; from Figure 9 As can be seen, the distortion of the fixed-focus lens provided in this embodiment has been well corrected, and the imaging distortion is small.

[0141] To provide a clearer explanation of the above embodiments, Table 7 details the specific optical physical parameters of each lens in the fixed-focus lens provided in Embodiments 1 to 3 of the present invention, as well as other feasible optical physical parameters.

[0142] Table 7 Design values ​​of optical physical parameters for fixed-focus lenses

[0143]

[0144] The specific embodiments described above do not constitute a limitation on the scope of protection of this 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 principles of this invention should be included within the scope of protection of this invention.

Claims

1. A fixed-focus lens, characterized in that, The lens comprises a first lens, a second lens, a third lens, an aperture stop, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially from the object side to the image side along the optical axis; the fixed-focus lens has seven lenses with optical power. The first lens is a plastic aspherical lens with negative optical power; The second lens is a plastic aspherical lens with negative optical power; The third lens is a glass spherical lens with positive optical power; The fourth lens is a glass spherical lens with positive optical power; The fifth lens is a glass spherical lens with negative optical power; The sixth lens is a plastic aspherical lens with positive optical power; The seventh lens is a plastic aspherical lens with negative optical power; The fourth lens and the fifth lens form a cemented doublet lens group, and the cemented doublet lens group has negative optical power; 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, the optical power of the seventh lens is φ7, and the optical power of the fixed-focus lens is φ, wherein: -0.448≤φ1 / φ≤-0.408; -0.42≤φ2 / φ≤-0.31; 0.524≤φ3 / φ≤0.712; 0.672≤φ4 / φ≤0.755; -0.987≤φ5 / φ≤-0.889; 1.027≤φ6 / φ≤1.133; -0.422≤φ7 / φ≤-0.

323.

2. The fixed-focus lens according to claim 1, characterized in that, The optical power of the doublet lens group is φ8, where -0.05≤φ8 / φ≤-0.

012.

3. The fixed-focus lens according to claim 1, characterized in that, The object-side surface of the first lens is convex, and the image-side surface of the first lens is concave. The object-side surface of the second lens is concave, and the image-side surface of the second lens is convex. The object-side surface of the third lens is convex, and the image-side surface of the third lens is convex. The object-side surface of the fourth lens is convex, and the image-side surface of the fourth lens is convex. The object-side surface of the fifth lens is concave, and the image-side surface of the fifth lens is also concave. The object-side surface of the sixth lens is convex, and the image-side surface of the sixth lens is convex. The object-side surface of the seventh lens is convex, and the image-side surface of the seventh lens is concave.

4. The fixed-focus lens according to claim 1, characterized in that, The refractive index of the third lens is Nd3, where 1.6 < Nd3 < 1.

98.

5. The fixed-focus lens according to claim 1, characterized in that, The Abbe number of the fourth lens is Vd4, where 58 < Vd4 < 96.

6. The fixed-focus lens according to claim 1, characterized in that, The image plane diameter of the fixed-focus lens is IC, and the entrance pupil diameter of the fixed-focus lens is EPD, wherein 0.96≤IC / EPD≤1.

24.

7. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens has an image plane diameter of IC and an optical length of TTL, wherein 0.25 ≤ IC / TTL ≤ 0.

34.

8. The fixed-focus lens according to claim 1, characterized in that, The back focal length of the fixed-focus lens is BFL, and the total optical length of the fixed-focus lens is TTL, where 0.15 <BFL / TTL≤5.4309 / 30.0647。 9. The fixed-focus lens according to claim 1, characterized in that, The fixed-focus lens also includes a filter; The filter is located on the image-side side of the seventh lens.

Images