Prime lens

Abstract

The prime lens comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged from an object plane to an image plane along an optical axis, the first lens is a negative-focal-power lens, the second lens is a negative-focal-power lens, the third lens is a positive-focal-power lens, the fourth lens is a positive-focal-power lens or a negative-focal-power lens, and the fifth lens is a positive-focal-power lens; the surface of the lens adjacent to the object surface is an object-side surface, and the surface of the lens adjacent to the image surface is an image-side surface; the curvature radius of the object side surface of the fourth lens is R41, the curvature radius of the image side surface of the fourth lens is R42, the focal length of the fourth lens is F4, the curvature radius of the object side surface of the fifth lens is R51, the curvature radius of the image side surface of the fifth lens is R52, and the focal length of the fifth lens is F5. According to the technical scheme of the embodiment of the utility model, the design of a vehicle-mounted lens which is high in imaging quality, compact in structure, large in aperture and large in field angle can be realized.

Description

Technical Field

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

[0002] With the development and application of technologies such as autonomous driving, smart cockpits and advanced driver assistance systems, the driver monitoring system (DMS) has become a research hotspot in the field of smart cars. The system is mainly used to monitor the driver's status and dangerous driving behaviors, which can effectively reduce traffic accidents.

[0003] As an important component of the DMS system, in-vehicle monitoring cameras are generally installed in positions facing the driver, such as the rearview mirror, driving recorder, steering wheel, central control screen, and A-pillar. However, the existing cameras are too large, which is not conducive to lens integration and the aesthetics of the interior. Utility Model Content

[0004] The utility model provides a fixed-focus lens to realize a vehicle-mounted lens design that takes into account imaging quality, compact structure, large aperture, and wide field of view.

[0005] The fixed-focus lens provided by the utility model comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence from the object plane to the image plane along the optical axis;

[0006] The first lens is a negative power lens, the second lens is a negative power lens, the third lens is a positive power lens, the fourth lens is a positive power lens or a negative power lens, and the fifth lens is a positive power lens;

[0007] 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 curvature radius of the object-side surface of the fourth lens is R41, the curvature radius of the image-side surface of the fourth lens is R42, and the focal length of the fourth lens is F4; the curvature radius of the object-side surface of the fifth lens is R51, the curvature radius of the image-side surface of the fifth lens is R52, and the focal length of the fifth lens is F5; wherein:

[0008]

[0009] Optionally, the first lens and the third lens are glass spherical lenses, and the second lens, the fourth lens and the fifth lens are plastic aspherical lenses.

[0010] Optionally, the object-side surface of the first lens is convex toward the object plane, and the image-side surface of the first lens is concave toward the image plane;

[0011] The object-side surface of the second lens is concave toward the object plane, and the image-side surface of the second lens is convex toward the image plane;

[0012] The object-side surface of the third lens is convex toward the object plane, and the image-side surface of the third lens is convex toward the image plane;

[0013] The object-side surface of the fourth lens element is concave toward the object plane, and the image-side surface of the fourth lens element is convex toward the image plane;

[0014] The object-side surface of the fifth lens is convex toward the object plane, and the image-side surface of the fifth lens is concave toward the image plane; or, the object-side surface of the fifth lens is convex toward the object plane, and the image-side surface of the fifth lens is convex toward the image plane.

[0015] Optionally, the refractive index of the first lens is Nd1, and the Abbe number of the first lens is Vd1; wherein:

[0016] 1.8 <Nd1<2.03,28.55<Vd1<60.90。

[0017] Optionally, the refractive index of the third lens is Nd3, and the Abbe number of the third lens is Vd3; wherein:

[0018] 1.91 <Nd3<2.1,24<Vd3<41。

[0019] Optionally, the refractive index of the fourth lens is greater than or equal to the refractive index of the fifth lens.

[0020] Optionally, the fixed-focus lens further includes an aperture;

[0021] The aperture is located in the optical path between the second lens and the third lens.

[0022] Optionally, the aspheric surface of the plastic aspheric lens satisfies:

[0023]

[0024] Among them, z represents the axial sagittal height in the Z direction of the aspheric surface; r represents the distance from the point on the aspheric surface to the optical axis; c represents the curvature of the fitted sphere, which is the inverse of the curvature radius; k represents the fitted cone coefficient; A, B, C, D, and E represent the 4th, 6th, 8th, 10th, and 12th order coefficients of the aspheric polynomial, respectively.

[0025] The fixed-focus lens provided by the embodiment of the utility model can enhance the resolution and image quality by using five lenses and reasonably matching the optical power of each lens, and limiting the relationship between the curvature radius and focal length of the fourth lens and the fifth lens close to the image side. It can also meet the design requirements of automotive lenses for a large field of view, a large aperture and miniaturization.

[0026] 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 invention, nor is it 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

[0027] 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 paying any creative work.

[0028] Figure 1 This is a structural schematic diagram of a fixed-focus lens provided in Example 1 of the present utility model;

[0029] Figure 2 This is an MTF curve diagram of the fixed-focus lens provided in Example 1 of the present utility model;

[0030] Figure 3 This is a structural schematic diagram of a fixed-focus lens provided in Example 2 of the present utility model;

[0031] Figure 4 This is an MTF curve diagram of the fixed-focus lens provided in Example 2 of the present utility model;

[0032] Figure 5 This is a structural schematic diagram of a fixed-focus lens provided in Example 3 of the present utility model;

[0033] Figure 6 This is an MTF curve diagram of the fixed-focus lens provided in Example 3 of the present utility model. DETAILED DESCRIPTION

[0034] In order to help those skilled in the art better understand the present invention, the following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described 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 making creative efforts should fall within the scope of protection of the present invention.

[0035] The fixed-focus lens provided by the utility model includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged in sequence along the optical axis from the object plane to the image plane; the first lens is a negative power lens, the second lens is a negative power lens, the third lens is a positive power lens, the fourth lens is a positive power lens or a negative power lens, and the fifth lens is a positive power lens; 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 curvature radius of the object-side surface of the fourth lens is R41, the curvature radius of the image-side surface of the fourth lens is R42, the focal length of the fourth lens is F4, the curvature radius of the object-side surface of the fifth lens is R51, the curvature radius of the image-side surface of the fifth lens is R52, and the focal length of the fifth lens is F5; wherein:

[0036]

[0037] The above is the core concept of this utility model. By using five lenses and rationally matching the optical power of each lens, as well as limiting the relationship between the curvature radius and focal length of the fourth and fifth lenses near the image side, the lens resolution can be enhanced, image quality can be improved, and the design requirements of automotive lenses for a large field of view, large aperture, and miniaturization can be met.

[0038] The following is a clear and complete description of the technical solutions of the embodiments of the present invention in conjunction with the accompanying drawings. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0039] Example 1

[0040] Figure 1 This is a schematic structural diagram of a fixed-focus lens provided in the first embodiment of the present invention. Figure 1 As shown, the fixed-focus lens provided by the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, and a fifth lens 150, which are arranged in sequence along the optical axis from the object plane to the image plane. The first lens 110 is a negative power lens, the second lens 120 is a negative power lens, the third lens 130 is a positive power lens, the fourth lens 140 is a positive power lens, and the fifth lens 150 is a positive power lens. 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 fourth lens 140 has a curvature radius of R41, the image-side surface of the fourth lens 140 has a curvature radius of R42, the focal length of the fourth lens 140 is F4, the object-side surface of the fifth lens 150 has a curvature radius of R51, the image-side surface of the fifth lens 150 has a curvature radius of R52, and the focal length of the fifth lens 150 is F5.

[0041] Specifically, 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, and it characterizes the ability of the optical system to deflect light. The larger the absolute value of the optical power, the stronger the ability to bend light, and the smaller the absolute value of the optical power, the weaker the ability to bend light. When the optical power is a positive number, the refraction of light is convergent; when the optical power is a negative number, the refraction of light is divergent. The optical power can be applied to characterize a certain refractive surface of a lens (i.e., a surface of a lens), can be applied to characterize a certain lens, and can also be applied 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 to a lens barrel ( Figure 1 Not shown).

[0042] In this embodiment, by configuring first lens 110 as a negative power lens, second lens 120 as a negative power lens, third lens 130 as a positive power lens, fourth lens 140 as either a positive or negative power lens, and fifth lens 150 as a positive power lens, the optical power of the entire fixed-focus lens is rationally distributed. This ensures a balanced angle of incidence between the front and rear lenses, reduces lens sensitivity, improves lens stability, enhances image quality, and facilitates achieving a large aperture. In this embodiment, the fixed-focus lens can achieve an aperture value of up to 1.2.

[0043] Specifically, the radius of curvature represents the degree of curvature of the lens surface. A positive radius of curvature indicates that the surface is curved toward the object plane, with its center closer to the image plane; a negative radius of curvature indicates that the surface is curved toward the image plane, with its center closer to the object plane. Specifically, focal length (also known as focal length) is a measure of light convergence or divergence in an optical system, referring to the distance from the optical center of a lens to the focal point where light converges when parallel light is incident. In this embodiment, by setting the radius of curvature R41 of the object-side surface of the fourth lens 140, the radius of curvature R42 of the image-side surface of the fourth lens 140, the focal length of the fourth lens 140 to F4, the radius of curvature R51 of the object-side surface of the fifth lens 150, the radius of curvature R52 of the image-side surface of the fifth lens 150, and the focal length F5 of the fifth lens 150 to satisfy the above relationship, the shape and optical power distribution of the fourth lens 140 and the fifth lens 150 can be well defined, which is beneficial for increasing the field of view, reducing the overall length of the lens, improving resolution, and ensuring image quality.

[0044] It should be noted that, in the first embodiment of the present invention, the fourth lens 140 is only illustrated as a positive power lens. In other embodiments, the fourth lens 140 may also be a negative power lens, which will be illustrated later.

[0045] In summary, the fixed-focus lens provided in the embodiment of the present invention, by using five lenses and rationally matching the optical focal lengths of each lens, and by limiting the relationship between the curvature radius and focal length of the fourth and fifth lenses close to the image side, can enhance resolution and improve image quality. It can also meet the design requirements of automotive lenses for a large field of view, a large aperture, and miniaturization.

[0046] Based on the above embodiment, optionally, the first lens 110 and the third lens 130 are glass spherical lenses, and the second lens 120 , the fourth lens 140 and the fifth lens 150 are plastic aspherical lenses.

[0047] Specifically, aspheric lenses are characterized by a continuously varying curvature from the center to the periphery. Unlike spherical lenses, which maintain a constant curvature from the center to the periphery, aspheric lenses have a more precise curvature radius, improving distortion and astigmatism. Using aspheric lenses minimizes aberrations that occur during imaging, thereby improving image quality. Spherical lenses also maintain a constant curvature from the center to the periphery, ensuring simple lens setup.

[0048] Furthermore, the material of the plastic aspheric lens can be various plastics known to those skilled in the art, and the material of the glass spherical lens can be various types of glass known to those skilled in the art. This is neither detailed nor limited in the present embodiment. Glass lenses have a low coefficient of thermal expansion and good stability, which helps maintain the focal length of fixed-focus lenses stable when the ambient temperature in which they are used fluctuates significantly. Plastic lenses are much less expensive than glass lenses, and using plastic lenses helps reduce the overall cost of fixed-focus lenses.

[0049] This embodiment utilizes a hybrid approach of glass spherical lenses and plastic aspherical lenses. By configuring the first lens 110 and the third lens 130 as glass spherical lenses, and the second lens 120, the fourth lens 140, and the fifth lens 150 as plastic aspherical lenses, the cost of the fixed-focus lens can be effectively controlled, reducing the processing requirements for the aspherical lenses. Furthermore, the embodiment can effectively correct for aberrations, ensuring sufficiently good image quality and allowing the lens materials to compensate for each other. This ensures that the fixed-focus lens can function normally in both high and low temperature environments, achieving stable high and low temperature resolution.

[0050] Optionally, the object surface of the first lens 110 bulges towards the object plane, and the image surface of the first lens 110 depresses towards the image plane; the object surface of the second lens 120 depresses towards the object plane, and the image surface of the second lens 120 bulges towards the image plane; the object surface of the third lens 130 bulges towards the object plane, and the image surface of the third lens 130 bulges towards the image plane; the object surface of the fourth lens 140 depresses towards the object plane, and the image surface of the fourth lens 140 bulges towards the image plane; the object surface of the fifth lens 150 bulges towards the object plane, and the image surface of the fifth lens 150 bulges towards the image plane.

[0051] Specifically, in this embodiment, by reasonably setting the surface shapes of each lens, it is beneficial to ensure the image quality and can also ensure the compact structure of the entire fixed-focus lens, achieving a miniaturized design. Exemplarily, the surface shapes of the first lens 110 and the second lens 120 are similar to a crescent, and their bending directions are opposite. In this way, light can enter the optical system better, and during the propagation of light, it can be stable without excessive deflection, so as to avoid introducing greater aberration, ensure the image quality, and at the same time is beneficial to reducing the aperture and total length of the lens.

[0052] It should be noted that in the first embodiment of the present invention, only the example that the object surface of the fifth lens 150 bulges towards the object plane and the image surface of the fifth lens 150 bulges towards the image plane is used for illustration. In other embodiments, it is optional that the object surface of the fifth lens 150 bulges towards the object plane and the image surface of the fifth lens 150 depresses towards the image plane, which will be illustrated later.

[0053] Optionally, the refractive index of the first lens 110 is Nd1, and the Abbe number of the first lens 110 is Vd1; where: 1.8 < Nd1 < 2.03, 28.55 < Vd1 < 60.90. Specifically, the first lens 110 is a glass lens. By setting the refractive index and Abbe number of the first lens 110 to meet the above range, light can be better converged, the ratio of the lens aperture to the curvature radius can be reduced, and the edge illumination can be improved.

[0054] Optionally, the refractive index of the third lens 130 is Nd3, and the Abbe number of the third lens 130 is Vd3; where: 1.91 < Nd3 < 2.1, 24 < Vd3 < 41. Specifically, the third lens 130 is a glass lens. This lens plays a role in correcting defocus at high and low temperatures. By setting the refractive index and Abbe number of the third lens 130 to meet the above range and cooperating with the optical power of other lenses, it is beneficial to obtain stable resolution at high and low temperatures.

[0055] Optionally, the refractive index of the fourth lens 140 is equal to the refractive index of the fifth lens 150.

[0056] Specifically, the fourth lens 140 and the fifth lens 150 are plastic aspheric lenses. The matching of the refractive indices of the fourth lens 140 and the fifth lens 150 facilitates chromatic aberration correction, further reduces system aberrations, and facilitates achieving high-definition image quality. In other embodiments, the refractive index of the fourth lens 140 can be set to be greater than the refractive index of the fifth lens 150.

[0057] Optionally, the fixed-focus lens further includes an aperture 160, which is located in the optical path between the second lens 120 and the third lens 130. By setting the aperture 160 relatively forward, the lens diameter at the front end of the lens can be effectively reduced, which is conducive to achieving a large aperture.

[0058] Optionally, the fixed-focus lens further includes a protective glass 170 ; the protective glass 170 is located in the optical path between the fifth lens 150 and the image plane.

[0059] As a feasible implementation, the optical physical parameters such as the surface type, curvature radius, thickness, refractive index, Abbe number, and half-aperture of each lens in the fixed-focus lens are described below in conjunction with Table 1.

[0060] In Table 1, the surface numbers are numbered according to the order of the lens surfaces. For example, surface number "S1" represents the object-side surface of the first lens, surface number "S2" represents the image-side surface of the first lens, and so on. "STO" represents the aperture stop of a fixed-focus lens; "IMA" represents the image surface of a fixed-focus lens. The radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface is curved toward the object plane with its center close to the image plane, while a negative value indicates that the surface is curved toward the image plane with its center close to the object plane. "PL" represents a flat surface, and the radius of curvature of a flat surface is infinite. The thickness represents the axial distance from the current surface to the center of the next surface. Due to the different number of digits in each parameter, focusing errors may occur. Therefore, the thickness of surface 13 can vary slightly. The value can be adjusted as needed to achieve clear focus. The refractive index (Nd) represents the light refracting ability of the material between the current surface and the next surface. A blank space represents air at the current position, with a refractive index of 1. The Abbe number (Vd) represents the light dispersion properties of the material between the current surface and the next surface. A blank space represents air at the current position. The semi-aperture is the semi-diameter of the lens.

[0061] Table 1 Design values ​​of optical physical parameters of fixed focus lens

[0062]

[0063] Based on the above embodiment, optionally, the aspheric surfaces of the above aspheric lenses (i.e., the second lens 120, the fourth lens 140, and the fifth lens 150) satisfy:

[0064]

[0065] Among them, z represents the axial sagittal height in the Z direction of the aspheric surface; r represents the distance from the point on the aspheric surface to the optical axis; c represents the curvature of the fitted sphere, which is the inverse of the curvature radius; k represents the fitted cone coefficient; A, B, C, D, and E represent the 4th, 6th, 8th, 10th, and 12th order coefficients of the aspheric polynomial, respectively.

[0066] Next, the data on the aspherical surface of the aspherical lens will be described in conjunction with Table 2 using a feasible implementation method.

[0067] Table 2 Parameter design values ​​of each surface of the aspheric lens in the fixed focus lens

[0068]

[0069] Among them, 6.3626825E-03 means that the coefficient A of the surface number S3 is 6.3626825*10 -3 , and so on.

[0070] The optical system of this embodiment achieves the following technical specifications: focal length f of 1.674mm, field of view of 144°, and aperture number of 1.2. The above solution enables the design of a fixed-focus lens that combines image quality, compact structure, large aperture, and wide field of view for automotive applications.

[0071] Furthermore, Figure 2 This is the MTF curve of the fixed focus lens provided by Example 1 of the present invention. The MTF curve represents the comprehensive resolution level of an optical system. The vertical direction in the figure is the normalized MTF, which indicates the quality of contrast and marks the resolution of the lens. The higher the better, and 1 is the full score. The horizontal direction represents the spatial frequency, 0 represents the spatial frequency of 0lp / mm, and the further to the right, the higher the spatial frequency. Figure 2 It can be seen that when the wavelength range is 0.92μm-0.96μm, the MTF value at the center field of view of 60lp / mm is ≥0.8, and the MTF value at the edge field of view of 60lp / mm is ≥0.45. The imaging from the center field of view to the edge field of view has excellent resolution.

[0072] Example 2

[0073] Figure 3 This is a schematic structural diagram of a fixed-focus lens provided in the second embodiment of the present invention. Figure 3As shown, the fixed-focus lens provided by the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, and a fifth lens 150, which are arranged in sequence along the optical axis from the object plane to the image plane. The first lens 110 is a negative power lens, the second lens 120 is a negative power lens, the third lens 130 is a positive power lens, the fourth lens 140 is a positive power lens, and the fifth lens 150 is a positive power lens. 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 fourth lens 140 has a curvature radius of R41, the image-side surface of the fourth lens 140 has a curvature radius of R42, the focal length of the fourth lens 140 is F4, the object-side surface of the fifth lens 150 has a curvature radius of R51, the image-side surface of the fifth lens 150 has a curvature radius of R52, and the focal length of the fifth lens 150 is F5.

[0074] The materials, refractive index, Abbe number, and other optical and physical parameter ranges of each lens are the same as those in Example 1 and are not further described here. The differences between this embodiment and Example 1 are that, first, the surface shape of the fifth lens is different. In this embodiment, the object-side surface of the fifth lens 150 is convex toward the object plane, while the image-side surface of the fifth lens 150 is concave toward the image plane. Second, in Example 1, the refractive index of the fourth lens 140 is equal to the refractive index of the fifth lens 150, while in this embodiment, the refractive index of the fourth lens 140 is greater than the refractive index of the fifth lens 150.

[0075] Table 3 describes in detail the specific setting parameters of each lens in the fixed-focus lens provided in Example 2 of the present invention in another feasible implementation manner. The fixed-focus lens in Table 3 corresponds to Figure 3 Prime lens shown.

[0076] Table 3 Design values ​​of optical physical parameters of fixed focus lens

[0077]

[0078] In Table 3, the surface numbers are numbered according to the order of the lens surfaces. For example, surface number "S1" represents the object-side surface of the first lens, surface number "S2" represents the image-side surface of the first lens, and so on. "STO" represents the aperture stop of a fixed-focus lens; "IMA" represents the image surface of a fixed-focus lens. The radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface is curved toward the object plane with its center close to the image plane, while a negative value indicates that the surface is curved toward the image plane with its center close to the object plane. "PL" represents a flat surface, and the radius of curvature of a flat surface is infinite. The thickness represents the axial distance from the current surface to the center of the next surface. Due to the different number of digits in each parameter, focusing errors may occur. Therefore, the thickness of surface 13 can vary slightly. The value can be adjusted as needed to achieve clear focus. The refractive index (Nd) represents the light deflection ability of the material between the current surface and the next surface. A blank space represents air at the current position, with a refractive index of 1. The Abbe number (Vd) represents the light dispersion characteristics of the material between the current surface and the next surface. A blank space represents air at the current position. The semi-aperture is the semi-diameter of the lens.

[0079] Next, the data on the aspherical surface of the aspherical lens will be described in conjunction with Table 4 using a feasible implementation method.

[0080] Table 4 Parameter design values ​​of each surface of the aspheric lens in the fixed focus lens

[0081]

[0082] Among them, 6.4409052E-03 means that the coefficient A of the surface number S3 is 6.4409052*10 -3 , and so on.

[0083] The optical system of this embodiment achieves the following technical specifications: focal length f of 1.673mm, field of view of 144°, and aperture number 1.2. The above solution enables the design of a fixed-focus lens that combines image quality, compact structure, large aperture, and wide field of view for automotive applications.

[0084] Further, Figure 4 This is the MTF curve of the fixed focus lens provided by Example 2 of the present invention. The MTF curve represents the comprehensive resolution level of an optical system. The vertical direction in the figure is the normalized MTF, which indicates the quality of contrast and marks the resolution of the lens. The higher the better, and 1 is the full score. The horizontal direction represents the spatial frequency, 0 represents the spatial frequency of 0lp / mm, and the further to the right, the higher the spatial frequency. Figure 4 It can be seen that when the wavelength range is 0.92μm-0.96μm, the MTF value at the center field of view of 60lp / mm is ≥0.8, and the MTF value at the edge field of view of 60lp / mm is ≥0.55. The imaging from the center field of view to the edge field of view has excellent resolution.

[0085] Example 3

[0086] Figure 5 This is a schematic structural diagram of a fixed-focus lens provided in the third embodiment of the present invention. Figure 5 As shown, the fixed-focus lens provided by the present invention includes a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, and a fifth lens 150, which are arranged in sequence along the optical axis from the object plane to the image plane. The first lens 110 is a negative-power lens, the second lens 120 is a negative-power lens, the third lens 130 is a positive-power lens, the fourth lens 140 is a negative-power lens, and the fifth lens 150 is a positive-power lens. 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 fourth lens 140 has a curvature radius of R41, the image-side surface of the fourth lens 140 has a curvature radius of R42, the focal length of the fourth lens 140 is F4, the object-side surface of the fifth lens 150 has a curvature radius of R51, the image-side surface of the fifth lens 150 has a curvature radius of R52, and the focal length of the fifth lens 150 is F5.

[0087] The materials, refractive index, Abbe number, and other optical and physical parameter ranges of each lens are the same as those in Example 1 and are not further described here. The differences between this embodiment and Example 1 are that, first, the optical power of the fourth lens 140 is inconsistent. In this embodiment, the fourth lens 140 is a negative optical power lens; second, the surface shape of the fifth lens 150 is inconsistent. In this embodiment, the object-side surface of the fifth lens 150 is convex toward the object plane, and the image-side surface of the fifth lens 150 is concave toward the image plane; and third, in Example 1, the refractive index of the fourth lens 140 is equal to the refractive index of the fifth lens 150, while in this embodiment, the refractive index of the fourth lens 140 is greater than the refractive index of the fifth lens 150.

[0088] Table 5 describes in detail the specific setting parameters of each lens in the fixed-focus lens provided in Example 3 of the present invention in another feasible implementation manner. The fixed-focus lens in Table 5 corresponds to Figure 5 Prime lens shown.

[0089] Table 5 Design values ​​of optical physical parameters of fixed focus lens

[0090]

[0091] In Table 5, the surface numbers are numbered according to the order of the surfaces of each lens. For example, surface number "S1" represents the object-side surface of the first lens, surface number "S2" represents the image-side surface of the first lens, and so on. "STO" represents the aperture of a fixed-focus lens; "IMA" represents the image surface of a fixed-focus lens. The radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface is curved toward the object plane with its center close to the image plane, while a negative value indicates that the surface is curved toward the image plane with its center close to the object plane. "PL" represents a plane, and the radius of curvature of a plane is infinite. The thickness represents the axial distance from the center of the current surface to the next surface. Due to the different number of digits in each parameter, focusing errors may occur. Therefore, the thickness of surface 13 can vary slightly. The value can be adjusted as needed to achieve clear focus. The refractive index (Nd) represents the light refracting ability of the material between the current surface and the next surface. A blank space represents air at the current position, with a refractive index of 1. The Abbe number (Vd) represents the light dispersion characteristics of the material between the current surface and the next surface. A blank space represents air at the current position. The semi-aperture is the semi-diameter of the lens.

[0092] Next, the data on the aspherical surface of the aspherical lens will be described in conjunction with Table 6 using a feasible implementation method.

[0093] Table 6 Parameter design values ​​of each surface of the aspheric lens in the fixed focus lens

[0094]

[0095] In Table 6, 4.0507006E-03 indicates that the coefficient A of the surface number S3 is 4.0507006*10 -3 , and so on.

[0096] The optical system of this embodiment achieves the following technical specifications: focal length f of 1.636mm, field of view of 144°, and aperture number of 1.2. The above solution enables the design of a fixed-focus lens that combines image quality, compact structure, large aperture, and wide field of view for automotive applications.

[0097] Further, Figure 6 This is the MTF curve of the fixed focus lens provided by the third embodiment of the present invention. The MTF curve represents the comprehensive resolution level of an optical system. The vertical direction of the figure is the normalized MTF, which indicates the quality of contrast and marks the resolution of the lens. The higher the better, and 1 is the full score. The horizontal direction represents the spatial frequency, 0 represents the spatial frequency of 0lp / mm, and the further to the right, the higher the spatial frequency. Figure 6 It can be seen that when the wavelength range is 0.92μm-0.96μm, the MTF value at the center field of view of 60lp / mm is ≥0.8, and the MTF value at the edge field of view of 60lp / mm is ≥0.4. The imaging from the center field of view to the edge field of view has excellent resolution.

[0098] The above specific embodiments do not limit the scope of protection of this utility model. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model shall be included within the scope of protection of this utility model.

Claims

1. A fixed-focus lens, characterized in that: comprising a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence along the optical axis from the object plane to the image plane; The first lens is a negative power lens, the second lens is a negative power lens, the third lens is a positive power lens, the fourth lens is a positive power lens or a negative power lens, and the fifth lens is a positive power lens; 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 curvature radius of the object-side surface of the fourth lens is R41, the curvature radius of the image-side surface of the fourth lens is R42, and the focal length of the fourth lens is F4; the curvature radius of the object-side surface of the fifth lens is R51, the curvature radius of the image-side surface of the fifth lens is R52, and the focal length of the fifth lens is F5; wherein:

2. The fixed-focus lens according to claim 1, wherein: The first lens and the third lens are glass spherical lenses, and the second lens, the fourth lens and the fifth lens are plastic aspherical lenses.

3. The fixed-focus lens according to claim 1, wherein: The object-side surface of the first lens is convex toward the object plane, and the image-side surface of the first lens is concave toward the image plane; The object-side surface of the second lens is concave toward the object plane, and the image-side surface of the second lens is convex toward the image 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 convex toward the image plane; The object-side surface of the fourth lens is concave toward the object plane, and the image-side surface of the fourth lens is convex toward the image plane; The object-side surface of the fifth lens is convex toward the object plane, and the image-side surface of the fifth lens is concave toward the image plane; Alternatively, the object-side surface of the fifth lens is convex toward the object plane, and the image-side surface of the fifth lens is convex toward the image plane.

4. The fixed-focus lens according to claim 1, wherein: The refractive index of the first lens is Nd1, and the Abbe number of the first lens is Vd1; wherein: 1.8 <Nd1<2.03,28.55<Vd1<60.90。 5. The fixed-focus lens according to claim 1, wherein: The refractive index of the third lens is Nd3, and the Abbe number of the third lens is Vd3; wherein: 1.91 <Nd3<2.1,24<Vd3<41。 6. The fixed-focus lens according to claim 1, wherein: The refractive index of the fourth lens is greater than or equal to the refractive index of the fifth lens.

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

8. The fixed-focus lens according to claim 2, wherein: The aspheric surface of the plastic aspheric lens satisfies: Among them, z represents the axial sagittal height in the Z direction of the aspheric surface; r represents the distance from the point on the aspheric surface to the optical axis; c represents the curvature of the fitted sphere, which is the inverse of the curvature radius; k represents the fitted cone coefficient; A, B, C, D, and E represent the 4th, 6th, 8th, 10th, and 12th order coefficients of the aspheric polynomial, respectively.

Images