Monitoring lens

Abstract

The utility model discloses a monitoring lens comprising a first lens, a second lens and a third lens which are arranged from an object plane to an image plane along an optical axis. The curvature radius of the object side surface of the second lens is R21, the curvature radius of the image side surface of the second lens is R22, and the focal length of the second lens is f2; the curvature radius of the object side surface of the third lens is R31, the curvature radius of the image side surface of the third lens is R32, and the focal length of the third lens is f3; wherein 1.2 < ((R31 + R32) * f3) / ((R21 + R22) * f2) < 2.9. According to the technical scheme, the arrangement of the three lenses ensures that the number of the lenses in the monitoring lens is small, and small size and low cost can be realized; by reasonably setting the corresponding relation between the surface type and the focal length of the second lens and the third lens, the optical lens with small total length and large image surface can be set, the focal length distribution of the lens is balanced, the resolution capability is improved, and the imaging effect is further improved.

Description

Technical Field

[0001] The embodiment of the utility model relates to the technical field of optical devices, and in particular to a monitoring lens. Background Art

[0002] Fatigue and distracted driving are major causes of traffic accidents, and the introduction of driver monitoring systems (DMS) can effectively reduce these occurrences. As a key component of DMS, in-vehicle monitoring cameras must be operational 24 / 7. However, current DMSs are still too large and require further improvements in optical performance, such as resolution and low distortion. Utility Model Content

[0003] The utility model provides a monitoring lens, which realizes an optical lens with a short total length, a large image surface and good resolution capability by reasonably setting the lens composition mode and the matching mode of the lens surface shape and the focal length.

[0004] The embodiment of the utility model provides a monitoring lens, comprising a first lens, a second lens and a third lens arranged in sequence from the object plane to the image plane along the optical axis;

[0005] The object-side curvature radius of the second lens is R21, the image-side curvature radius of the second lens is R22, and the focal length of the second lens is f2; the object-side curvature radius of the third lens is R31, the image-side curvature radius of the third lens is R32, and the focal length of the third lens is f3;

[0006] Among them, 1.2<((R31+R32)*f3) / ((R21+R22)*f2)<2.9.

[0007] Optionally, the first lens is a positive power lens, the second lens is a positive power lens, and the third lens is a negative power lens.

[0008] Optionally, the first lens includes a glass spherical lens, the second lens includes a plastic aspherical lens, and the third lens includes a plastic aspherical lens.

[0009] Optionally, the object side surface of the first lens is convex and the image side surface is flat; the object side surface of the second lens is concave and the image side surface is convex; the object side surface of the third lens is convex and the image side surface is concave.

[0010] Optionally, the optical back focus of the monitoring lens is BFL, and the total optical length is TTL;

[0011] Among them, BFL / TTL>0.285.

[0012] Optionally, the image plane diameter of the monitoring lens is IC and the total optical length is TTL;

[0013] Among them, IC / TTL>0.75.

[0014] Optionally, the refractive index of the first lens is Nd1, and the Abbe number is Vd1; wherein, 1.86 <Nd1<2.1,24<Vd1<46;

[0015] A refractive index of the second lens is smaller than a refractive index of the third lens.

[0016] Optionally, the total optical length of the monitoring lens is TTL;

[0017] Among them, TTL<8.8mm.

[0018] Optionally, the maximum field of view of the monitoring lens is FOV, and the focal length of the monitoring lens is f;

[0019] Among them, FOV ≥ 66°, 4.5 ≤ f ≤ 6.

[0020] Optionally, the monitoring lens further includes an aperture and a filter;

[0021] The aperture is arranged in the optical path between the object plane and the first lens;

[0022] The filter is arranged in the optical path between the third lens and the image plane.

[0023] The monitoring lens provided by the embodiment of the present invention includes a first lens, a second lens and a third lens. The arrangement of the three lenses ensures that the number of lenses in the monitoring lens is small, which is conducive to realizing a small-volume and low-cost fixed-focus optical system; and the object side curvature radius R21, the image side curvature radius R22 and the focal length f2 of the second lens, and the object side curvature radius R31, the image side curvature radius R32 and the focal length f3 of the third lens satisfy 1.2<((R31+R32)*f3) / ((R21+R22)*f2)<2.9. By reasonably setting the correspondence between the surface shapes and focal lengths of the second and third lenses, it is conducive to realizing an optical lens arrangement with a small total length and a large image surface, while balancing the focal length distribution of the lenses, improving the resolution capability, and thus improving the imaging effect.

[0024] 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

[0025] 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.

[0026] Figure 1 This is a schematic structural diagram of a surveillance camera provided in the first embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of a distortion curve of a surveillance lens provided in Example 1 of the present utility model;

[0028] Figure 3 This is a schematic structural diagram of a surveillance camera provided in the second embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of a distortion curve of a surveillance lens provided in the second embodiment of the present utility model;

[0030] Figure 5 This is a schematic structural diagram of a surveillance camera provided by the third embodiment of the present invention;

[0031] Figure 6 This is a schematic diagram of a distortion curve of a surveillance lens provided in Example 3 of the present utility model. DETAILED DESCRIPTION

[0032] 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.

[0033] Example 1

[0034] Figure 1 This is a schematic diagram of the structure of a monitoring lens provided by the first embodiment of the present utility model. Figure 1As shown, the surveillance lens provided in Example 1 of the present invention includes a first lens 101, a second lens 102 and a third lens 103 arranged in sequence along the optical axis from the object plane to the image plane; the object side surface curvature radius of the second lens 102 is R21, the image side surface curvature radius of the second lens is R22, and the focal length of the second lens is f2; the object side surface curvature radius of the third lens is R31, the image side surface curvature radius of the third lens is R32, and the focal length of the third lens is f3; wherein, 1.2<((R31+R32)*f3) / ((R21+R22)*f2)<2.9.

[0035] Specifically, the surveillance camera provided by the present embodiment includes three lenses: a first lens 101, a second lens 102, and a third lens 103. These three lenses modulate incident light to achieve an optical system with a fixed focal length. Furthermore, because the optical system only includes three lenses, its structure is simple, making it easy to implement a compact and low-cost optical system.

[0036] Furthermore, the object side surface of the lens can be understood as the surface of the lens on the side close to the object surface, and the image side surface of the lens can be understood as the surface of the lens on the side close to the image surface. The curvature radius of the lens can represent the degree of convexity or concavity of the lens. By limiting the object side curvature radius R21, the image side curvature radius R22 and the focal length f2 of the second lens 102, and the object side curvature radius R31, the image side curvature radius R32 and the focal length f3 of the third lens to satisfy 1.2<((R31+R32)*f3) / ((R21+R22)*f2)<2.9, by reasonably setting the corresponding relationship between the surface shape and focal length of the second lens and the third lens, it is conducive to achieving an optical lens setting with a small total length and a large image surface, while balancing the focal length distribution of the lens, improving the resolution capability, and thus improving the imaging effect.

[0037] Specifically, in the embodiment of the present invention, the diameter of the image plane of the monitoring lens can reach 6.8 mm, and the total optical length is TTL, wherein TTL is less than 8.8 mm, thereby ensuring that a monitoring lens with a large image plane and a small total optical length can be realized.

[0038] In summary, the monitoring lens provided by the embodiment of the present invention has a three-lens arrangement that can ensure that the number of lenses in the monitoring lens is small, which is conducive to realizing a small-volume and low-cost fixed-focus optical system; and by reasonably setting the correspondence between the surface shape and focal length of the second lens and the third lens, it is conducive to realizing an optical lens arrangement with a small total length and a large image surface, while balancing the focal length distribution of the lenses, improving the resolution capability, and thus improving the imaging effect.

[0039] Based on the above embodiments, continue to refer to Figure 1As shown, the surveillance lens provided by the embodiment of the present invention may further include an aperture 104 and a filter 105; the aperture 104 is arranged in the optical path between the object plane and the first lens 101; the filter 105 is arranged in the optical path between the third lens 103 and the image plane.

[0040] Specifically, the aperture 104 can adjust the propagation direction of the light beam, which is beneficial for improving imaging quality. Furthermore, in this surveillance lens, the aperture 105 is located in the optical path between the object plane and the first lens 101. In other words, the aperture 104 is located on the object side of the first lens 101. This helps reduce the aperture and overall length of the surveillance lens.

[0041] The filter 105 is disposed in the optical path between the third lens 103 and the image plane to filter out stray light and improve imaging effects.

[0042] Furthermore, the surveillance lens provided in the embodiments of the present invention may also include a protective glass and an image capture element. The protective glass may be disposed on the image side of the filter, and the image capture element may be disposed on the image side of the protective glass. The protective glass protects the optical system, and the image capture element captures images, thereby achieving normal imaging function of the optical system.

[0043] Based on the above embodiment, the first lens 101 is a positive power lens, the second lens 102 is a positive power lens, and the third lens 103 is a negative power lens.

[0044] Furthermore, the focal length is equal to the difference between the convergence of the image plane light beam and the convergence of the object plane light beam, which characterizes the ability of the optical system to deflect light. The larger the absolute value of the focal length, the stronger the ability to bend light, and the smaller the absolute value of the focal length, the weaker the ability to bend light. 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 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 embodiment of the present invention, the first lens 101 and the second lens 102 are both positive focal length lenses, and the setting of their positive focal length can significantly correct the edge aberration of the optical imaging system, thereby improving the imaging resolution of the optical system. The third lens 103 is a negative focal length lens, and the setting of its negative focal length can effectively deflect the outgoing light, which is conducive to the design of a large image surface. By rationally allocating the optical power of each lens in the optical system, good imaging effects and a larger image plane design of the optical system can be ensured.

[0045] Based on the above embodiment, the first lens 101 includes a glass spherical lens, the second lens 102 includes a plastic aspherical lens, and the third lens 103 includes a plastic aspherical lens.

[0046] Specifically, spherical lenses are characterized by a constant curvature from the center to the periphery, ensuring simple lens configuration. Furthermore, because glass lenses have a low coefficient of thermal expansion and excellent stability, first lens 101 can be configured as a glass spherical lens. Glass spherical lenses offer greater thermal stability, ensuring good resolution over a wide temperature range when handling a wide range of optical powers. Furthermore, compared to plastic aspherical lenses, glass materials offer a wider range of material options, with relatively free choices of refractive index and Abbe constant. This allows for a certain degree of control over higher-order aberrations and chromatic aberrations, meeting the demands of use under complex conditions.

[0047] Aspheric lenses are characterized by a continuously varying curvature from the center to the periphery. Unlike spherical lenses, which have a constant curvature from the center to the periphery, aspheric lenses have a more optimized radius of curvature, improving distortion and astigmatism. Using aspheric lenses for the second lens 102 and the third lens 103 minimizes aberrations that occur during imaging, thereby improving the imaging quality of the lens. Furthermore, the aspheric lenses can be made of plastic, which simplifies the manufacturing process and reduces the cost of aspheric lenses.

[0048] In the monitoring lens provided by the embodiment of the present invention, a glass spherical lens and a plastic aspherical lens can be mixed and matched, which can effectively control the cost of the monitoring lens while ensuring the optical performance of the monitoring lens; at the same time, the materials of each lens have a mutual compensation effect, which can ensure that it can still be used normally in high and low temperature environments.

[0049] Based on the above embodiment, the object-side surface of the first lens 101 is convex and the image-side surface is flat; the object-side surface of the second lens 102 is concave and the image-side surface is convex; and the object-side surface of the third lens 103 is convex and the image-side surface is concave.

[0050] Specifically, the object side of the first lens 101 is convex and the image side is flat. It can be understood that the object side of the first lens 101 bulges towards the object plane at the position near the optical axis, and the image side is flat at the position near the optical axis. That is, the first lens 101 is a convex-plano lens. The object side of the second lens 102 is concave and the image side is convex. It can be understood that the object side of the second lens 102 depresses towards the object plane at the position near the optical axis, and the image side bulges towards the image plane at the position near the optical axis. That is, the second lens 102 is a concave-convex lens. The object side of the third lens 103 is convex and the image side is concave. It can be understood that the object side of the third lens 103 bulges towards the object plane at the position near the optical axis, and the image side depresses towards the image plane at the position near the optical axis. That is, the third lens 103 is a convex-concave lens. By reasonably setting the surface types of each lens, the trend of marginal rays can be ensured to be smoother, the relative illuminance between the marginal image and the central image can be improved, and the imaging effect can be enhanced.

[0051] Based on the above embodiments, the back focal length of the monitoring lens is BFL and the total optical length is TTL; where BFL / TTL > 0.285. In this way, sufficient installation space for the imaging sensor and the flat filter can be ensured.

[0052] Based on the above embodiments, the image plane diameter of the monitoring lens is IC and the total optical length is TTL; where IC / TTL > 0.75. In this way, it can be ensured that the monitoring lens has a relatively large target surface.

[0053] Based on the above embodiments, the refractive index of the first lens 101 is Nd1 and the Abbe number is Vd1; where 1.86 < Nd1 < 2.1 and 24 < Vd1 < 46; the refractive index of the second lens 102 is less than that of the third lens 103.

[0054] Specifically, by reasonably setting the refractive index and Abbe number of the first lens 101, light can be better converged, the aperture can be reduced, and the total length can be shortened. Moreover, among the second lens 102 and the third lens 103, one is a high-refractive-index lens and the other is a low-refractive-index lens. For example, the second lens 102 is a low-refractive-index lens with a refractive index less than 1.59; the third lens 103 is a high-refractive-index lens with a refractive index greater than 1.59. The refractive index combination of the second lens 102 and the third lens 103 is conducive to chromatic aberration correction, further reducing the aberration of the monitoring lens and facilitating the realization of high-definition image quality.

[0055] Based on the above embodiments, the maximum field angle of the monitoring lens is FOV and the focal length of the monitoring lens is f; where FOV ≥ 66° and 4.5 ≤ f ≤ 6. The field angle and focal length ranges are reasonable to achieve the in-vehicle monitoring function.

[0056] As a feasible implementation manner, the specific parameters in the monitoring lens will be described next.

[0057] Table 1 Optical design values ​​of the monitoring lens in Example 1

[0058] Scope of protection Example 1 Lower limit Upper limit Nd1 1.998 1.86 2.1 Vd1 30 24 46 ((R31+R32)*f3) / ((R21+R22)*f2) 1.375 1.2 2.9 BFL / TTL 0.309 0.285 \ IC / TTL 0.78 0.75 \

[0059] Table 2 Design values ​​of optical physical parameters of a surveillance lens

[0060]

[0061] The surface numbers in Table 2 are numbered according to the order of the lens surfaces. "STO" represents the aperture of the surveillance lens; "IMA" represents the image plane of the surveillance 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 image plane, while a negative value indicates that the surface is curved toward the object plane. "PL" indicates that the surface is flat and has an infinite radius of curvature. The thickness represents the axial distance from the center of the current surface to the next surface. Due to the different digits of each parameter, focusing errors may occur. Therefore, the thickness of the ninth surface 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 indicates that the current position is air, with a refractive index of 1. The material (Vd) represents the Abbe number, which is the light dispersion property of the material between the current surface and the next surface. A blank space indicates that the current position is air. The semi-diameter represents the semi-diameter of the lens.

[0062] The aspheric cone coefficient can be defined by the following aspheric formula, but is not limited to the following expression method:

[0063]

[0064] Wherein, z is the axial sagittal 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; AG is the coefficient of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial.

[0065] Table 3 Aspheric coefficients of a surveillance lens

[0066]

[0067] Among them, "-2.2030518E-03" means --2.2030518*10 -3 , and the remaining coefficients all use this representation method.

[0068] Based on the above parameter limitations, the optical parameters that can be achieved by the surveillance lens in the first embodiment of the present invention are as follows:

[0069] Focal length f: 5mm.

[0070] Maximum field of view FOV: 67.25°.

[0071] Figure 2 This is a schematic diagram of the distortion curve for a surveillance lens provided in Example 1 of the present invention. The horizontal axis represents the degree of distortion, expressed in %, while the vertical axis represents the normalized image height, without units. It can be seen that the distortion of the lens provided in this example is well corrected, with the absolute value of imaging distortion less than 3%, and the difference between the image and the actual object is minimal.

[0072] In summary, the surveillance lens provided in Example 1 of the present invention utilizes a glass spherical surface and two plastic aspherical surfaces. By rationally combining the surface shape with the focal length, the optical power, and other optical parameter settings, a surveillance lens with excellent overall performance is designed that takes into account imaging requirements, a compact structure, minimal distortion, and low cost.

[0073] Example 2

[0074] Figure 3 This is a schematic diagram of the structure of a monitoring lens provided by the second embodiment of the present utility model. Figure 3 As shown, the surveillance lens provided in Example 2 of the present invention includes a first lens 101, a second lens 102, and a third lens 103 arranged in sequence along the optical axis from the object plane to the image plane; the object side surface curvature radius of the second lens 102 is R21, the image side surface curvature radius of the second lens is R22, and the focal length of the second lens is f2; the object side surface curvature radius of the third lens is R31, the image side surface curvature radius of the third lens is R32, and the focal length of the third lens is f3; wherein, 1.2<((R31+R32)*f3) / ((R21+R22)*f2)<2.9.

[0075] The configuration of the lens is the same as that in the first embodiment, and will not be described again here.

[0076] As another feasible implementation, the specific parameters in the monitoring lens are described below.

[0077] Table 4 Optical design values ​​of the monitoring lens in Example 2

[0078] Scope of protection Example 2 Lower limit Upper limit Nd1 1.907 1.86 2.1 Vd1 45 24 46 ((R31+R32)*f3) / ((R21+R22)*f2) 1.527 1.2 2.9 BFL / TTL 0.313 0.285 \ IC / TTL 0.81 0.75 \

[0079] Table 5 Design values ​​of optical physical parameters of a surveillance lens

[0080]

[0081] The surface numbers in Table 5 are numbered according to the order of the lens surfaces. "STO" represents the aperture of the surveillance lens; "IMA" represents the image plane of the surveillance 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 image plane, while a negative value indicates that the surface is curved toward the object plane. "PL" represents a flat surface with an infinite radius of curvature. The thickness represents the axial distance from the center of the current surface to the next surface. Due to the different digits of each parameter, focusing errors may occur. Therefore, the thickness of the ninth surface 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 the current position as air with a refractive index of 1. The material (Vd) represents the Abbe number, that is, the light dispersion characteristics of the material between the current surface and the next surface. A blank space represents the current position as air. The semi-diameter represents the semi-diameter of the lens.

[0082] The aspheric cone coefficient can be defined by the following aspheric formula, but is not limited to the following expression method:

[0083]

[0084] Wherein, z is the axial sagittal 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; AG is the coefficient of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial.

[0085] Table 6 Aspheric coefficients of a surveillance lens

[0086]

[0087] Among them, "-2.6245183E-04" means -2.6245183*10 -4 , and the remaining coefficients all use this representation method.

[0088] Based on the above parameter limitations, the optical parameters that can be achieved by the surveillance lens in the second embodiment of the present invention are as follows:

[0089] Focal length f: 5.05mm.

[0090] Maximum field of view FOV: 67.25°.

[0091] Figure 4 This is a schematic diagram of the distortion curve for a surveillance lens provided in Example 2 of the present invention. The horizontal axis represents the degree of distortion in %, while the vertical axis represents the normalized image height in units of zero. It can be seen that the lens provided in this example achieves excellent distortion correction, with an absolute value of imaging distortion less than 3%, and the difference between the image and the actual object is minimal.

[0092] In summary, the surveillance lens provided in Example 2 of the present invention uses a glass spherical surface and two plastic aspherical surfaces. By reasonably matching the surface shape with the focal length, the optical power, and other optical parameter settings, a surveillance lens with excellent comprehensive performance that can meet imaging requirements, compact structure, low distortion, and low cost is designed.

[0093] Example 3

[0094] Figure 5 This is a schematic diagram of the structure of a monitoring lens provided by the third embodiment of the present utility model. Figure 5 As shown, the surveillance lens provided in Example 3 of the present invention includes a first lens 101, a second lens 102 and a third lens 103 arranged in sequence along the optical axis from the object plane to the image plane; the object side surface curvature radius of the second lens 102 is R21, the image side surface curvature radius of the second lens is R22, and the focal length of the second lens is f2; the object side surface curvature radius of the third lens is R31, the image side surface curvature radius of the third lens is R32, and the focal length of the third lens is f3; wherein, 1.2<((R31+R32)*f3) / ((R21+R22)*f2)<2.9.

[0095] The configuration of the lens is the same as that in the first embodiment, and will not be described again here.

[0096] As another feasible implementation, the specific parameters in the monitoring lens are described below.

[0097] Table 7 Optical design values ​​of the monitoring lens in Example 3

[0098] Scope of protection Example 3 Lower limit Upper limit Nd1 2.05 1.86 2.1 Vd1 25 24 46 ((R31+R32)*f3) / ((R21+R22)*f2) 2.795 1.2 2.9 BFL / TTL 0.295 0.285 \ IC / TTL 0.78 0.75 \

[0099] Table 8 Design values ​​of optical physical parameters of a surveillance lens

[0100]

[0101] The surface numbers in Table 8 are numbered according to the order of the surfaces of each lens. "STO" represents the aperture of the surveillance lens; "IMA" represents the image plane of the surveillance 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 image plane, while a negative value indicates that the surface is curved toward the object plane. "PL" represents a flat surface with an infinite radius of curvature. The thickness represents the axial distance from the center of the current surface to the next surface. Due to the different digits of each parameter, focusing errors may occur. Therefore, the thickness of the ninth surface 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 the current position as air with a refractive index of 1. The material (Vd) represents the Abbe number, that is, the light dispersion characteristics of the material between the current surface and the next surface. A blank space represents the current position as air. The semi-diameter represents the semi-diameter of the lens.

[0102] The aspheric cone coefficient can be defined by the following aspheric formula, but is not limited to the following expression method:

[0103]

[0104] Wherein, z is the axial sagittal 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; AG is the coefficient of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspheric polynomial.

[0105] Table 9 Aspheric coefficients of a surveillance lens

[0106]

[0107] Among them, "2.4015007E-05" means 2.4015007*10 -5 , and the remaining coefficients all use this representation method.

[0108] Based on the above parameter limitations, the optical parameters that can be achieved by the surveillance lens in the third embodiment of the present invention are as follows:

[0109] Focal length f: 5.01mm.

[0110] Maximum field of view FOV: 67.25°.

[0111] Figure 6 This is a schematic diagram of the distortion curve for a surveillance lens provided in Example 3 of the present invention. The horizontal axis represents the degree of distortion in %, while the vertical axis represents the normalized image height in units of zero. It can be seen that the lens provided in this example achieves excellent distortion correction, with an absolute value of imaging distortion less than 3%, and the difference between the image and the actual object is minimal.

[0112] In summary, the surveillance lens provided in Example 3 of the present invention uses a glass spherical surface and two plastic aspherical surfaces. By reasonably matching the surface shape with the focal length, the optical power, and other optical parameter settings, a surveillance lens with excellent comprehensive performance that can meet imaging requirements, compact structure, low distortion, and low cost is designed.

[0113] 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 surveillance camera, characterized in that: comprising a first lens, a second lens, and a third lens arranged in sequence from the object plane to the image plane along the optical axis; The object-side curvature radius of the second lens is R21, the image-side curvature radius of the second lens is R22, and the focal length of the second lens is f2; the object-side curvature radius of the third lens is R31, the image-side curvature radius of the third lens is R32, and the focal length of the third lens is f3; Among them, 1.2<((R31+R32)*f3) / ((R21+R22)*f2)<2.

9.

2. The surveillance camera according to claim 1, wherein: The first lens is a positive power lens, the second lens is a positive power lens, and the third lens is a negative power lens.

3. The surveillance camera according to claim 1, wherein: The first lens includes a glass spherical lens, the second lens includes a plastic aspherical lens, and the third lens includes a plastic aspherical lens.

4. The surveillance camera according to claim 1, wherein: The object-side surface of the first lens is convex, and the image-side surface is flat; the object-side surface of the second lens is concave, and the image-side surface is convex; the object-side surface of the third lens is convex, and the image-side surface is concave.

5. The surveillance camera according to claim 1, wherein: The optical back focus of the monitoring lens is BFL, and the total optical length is TTL; Among them, BFL / TTL>0.

285.

6. The surveillance camera according to claim 1, wherein: The image diameter of the monitoring lens is IC, and the total optical length is TTL; Among them, IC / TTL>0.

75.

7. The surveillance camera according to claim 1, wherein: The refractive index of the first lens is Nd1, and the Abbe number is Vd1; wherein, 1.86 <Nd1<2.1,24<Vd1<46; A refractive index of the second lens is smaller than a refractive index of the third lens.

8. The surveillance camera according to claim 1, wherein: The total optical length of the monitoring lens is TTL; Among them, TTL<8.8mm.

9. The surveillance camera according to claim 1, wherein: The maximum field of view of the monitoring lens is FOV, and the focal length of the monitoring lens is f; Among them, FOV ≥ 66°, 4.5 ≤ f ≤ 6.

10. The surveillance camera according to claim 1, wherein: The monitoring lens also includes an aperture and a filter; The aperture is arranged in the optical path between the object plane and the first lens; The filter is arranged in the optical path between the third lens and the image plane.

Images