An in-vehicle monitoring camera

Abstract

This invention provides an in-vehicle monitoring lens, comprising a first lens, a second lens, a third lens, and a fourth lens arranged sequentially along the optical axis from the object side to the image side. An aperture is provided before the object side of the first lens, and a filter and a protective sheet are provided after the image side of the fourth lens. The object side of the first lens is convex, and the first lens has positive refractive power. The object side and image side of the second lens are both concave, and the second lens has negative refractive power. The object side of the third lens is concave, and the image side of the third lens is convex, and the third lens has positive refractive power. The object side of the fourth lens is convex, and the image side of the fourth lens is concave, and the fourth lens has positive refractive power. By rationally allocating the refractive power of each lens and adopting a four-element design, the number of lenses is small, the structure is simple, the size is compact, installation and use are convenient, and lens costs can be saved.

Description

Technical Field

[0001] This invention relates to the field of optical imaging lens technology, and more specifically to an in-vehicle monitoring lens. Background Technology

[0002] In-vehicle monitoring lenses are mainly used for real-time monitoring of in-vehicle safety during vehicle operation. Chinese patent document CN215895097U discloses a short-focal-length in-vehicle monitoring lens, which includes, from the object side to the image side along an optical axis, a first lens, a second lens, a third lens, an aperture, a fourth lens, a fifth lens, and a sixth lens. Each of the first to sixth lenses includes an object-side surface facing the object side and allowing imaging light to pass through, and an image-side surface facing the image side and allowing imaging light to pass through. The first lens has a negative refractive index, the second lens has a negative refractive index, the third lens has a positive refractive index, the fourth lens has a negative refractive index, the fifth lens has a positive refractive index, and the sixth lens has a positive refractive index.

[0003] The shortcomings of the aforementioned in-vehicle monitoring camera are: the distance from the center of the front surface of the first lens of the optical system to the image plane is too large, and there are too many lenses, which makes the overall cost and weight of the lens too high, and its installation and use are limited. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to propose an in-vehicle monitoring camera to solve the problems mentioned in the background section above.

[0005] This invention is achieved through the following technical solution:

[0006] An in-vehicle monitoring camera includes a first lens, a second lens, a third lens, and a fourth lens arranged sequentially along the optical axis from the object side to the image side, wherein:

[0007] The object-side surface of the first lens is convex, and the first lens has positive refractive power;

[0008] The object-side surface of the second lens is concave, the image-side surface of the second lens is concave, and the second lens has negative refractive power.

[0009] The object-side surface of the third lens is concave, the image-side surface of the third lens is convex, and the third lens has positive refractive power.

[0010] The object-side surface of the fourth lens is convex, the image-side surface of the fourth lens is concave, and the fourth lens has positive refractive power.

[0011] The beneficial effects of this embodiment are as follows: by reasonably allocating the diopter of each lens, optimizing the surface shape, thickness and distance between each lens, the lens has good imaging quality. It adopts a four-element design, with fewer lenses, simple structure, small and compact size, convenient installation and use, and can save lens costs.

[0012] Furthermore, the image-side surface of the first lens is planar.

[0013] The beneficial effects of this embodiment are as follows: the image side of the first lens is a plane, which can significantly improve the assembly accuracy of the optical system, reduce the complexity of the structural components, avoid increasing costs by digging steps on the image side of the first lens, or cause dust, scratches, tilting and other phenomena caused by direct contact between lenses.

[0014] Furthermore, the lens optical system satisfies the following relationship: 200≤DFOV*f≤300;

[0015] Where DFOV is the maximum field of view in degrees; f is the total focal length of the optical system in millimeters.

[0016] The beneficial effects of this embodiment are as follows: In order to solve the problem that the field of view of the lens monitoring in the prior art is too large or too small and cannot match the current specific field of view requirements, by setting 200≤DFOV*f≤300, the maximum field of view of the lens optical system of the present invention meets the actual use requirements, avoids the monitoring range of too small a field of view being too small, and avoids the waste of the lens imaging area caused by too large a field of view, resulting in a reduction in the pixel ratio of the image plane.

[0017] Furthermore, the field of view of the lens optical system and the corresponding imaging circle diameter satisfy the following relationship:

[0018] 8.6≤DFOV / D≤14.6, 8.7≤HFOV / H≤14.7, 8.8≤VFOV / V≤14.8;

[0019] Where D is the diagonal dimension of the sensor, H is the horizontal dimension of the sensor, and V is the vertical dimension of the sensor, all in millimeters;

[0020] DFOV is the object-side field of view angle of the optical system under the corresponding D imaging circle, in degrees;

[0021] HFOV is the object-side field of view angle of the optical system under the H imaging circle, in degrees;

[0022] VFOV is the object-side field of view angle of the optical system under the corresponding V imaging circle, in degrees.

[0023] The beneficial effects of this embodiment are as follows: Based on the geometric parameters such as field of view and sensor size, the theoretical value of the focal length is calculated. The focal length of the optical system is controlled to the target value through scaling of the initial structure. Based on this, the focal length control is released, thereby controlling the field of view of the optical system to the target value, so that the field of view of the optical system meets specific requirements, and the object-side field of view of the optical system corresponding to the diameters of the D, H, and V imaging rings meets specific requirements.

[0024] Furthermore, the back focal length of the lens optical system and the half-image height of the optical system satisfy the following relationship: 0.7≤BFL / y'≤1.3;

[0025] Where BFL is the back intercept of the optical system, and y' is the half-image height of the optical system.

[0026] The beneficial effects of this embodiment are as follows: In order to solve the problem that the back focal length of the lens in the prior art is relatively long, resulting in a long distance between the contact point between the lens and the base and the end point of the base, which is not conducive to temperature drift, by setting 0.7≤BFL / y'≤1.3, the lens of the present invention has a smaller back focal length. By controlling the back focal length of the optical system and shortening it as much as possible, and at the same time selecting a shorter base, the temperature drift performance of the optical system is improved, which is beneficial to significantly improving the temperature drift performance of the lens of the present invention.

[0027] Furthermore, the total length of the lens optical system and the half-image height of the optical system satisfy the following relationship: 3≤TTL / y'≤4;

[0028] Where TTL is the total length of the optical system and y' is the half-image height of the optical system.

[0029] The beneficial effects of this embodiment are: by setting 3≤TTL / y'≤4, it is beneficial to reduce the total length of the optical phase, realize the structural design requirements of compact miniaturization, reduce the space occupied by the lens, and facilitate integration.

[0030] Furthermore, the radii of curvature of the first lens and the second lens satisfy the following relationship: |L1R2|≥200, 1≤L2R2≤5;

[0031] Wherein, L1R2 is the radius of curvature of the image-side surface of the first lens, and L2R2 is the radius of curvature of the image-side surface of the second lens.

[0032] The beneficial effects of this embodiment are as follows: In order to solve the problem that the lens has relatively large optical distortion in the prior art, resulting in severe distortion of the photographed object and making it difficult to observe, by setting |L1R2|≥200 and 1≤L2R2≤5, the image side of the first lens and the image side of the second lens generate negative distortion to compensate for the distortion of other surfaces of the optical system, and control the remaining distortion of the optical system to a relatively small value, so that the total distortion of the optical system is small, thereby obtaining a video image with small distortion of the photographed object.

[0033] Furthermore, the radius of curvature of the fourth lens and the maximum CRA of the lens optical system satisfy the following relationship:

[0034] 4.5≤L4R2≤9、16°≤CRA≤23°。

[0035] Where L4R2 is the radius of curvature of the image side surface of the fourth lens, and CRA is the maximum CRA angle within the imaging field of view.

[0036] The beneficial effects of this embodiment are as follows: In order to solve the problem that the lens CRA principal ray angle is too small in the prior art and cannot match the maximum CRA principal ray angle of the sensor, by setting 4.5≤L4R2≤9 and 16°≤CRA≤23°, and by controlling the exit angle of the last surface of the optical system, the incident angle of the edge field of view on the image plane is matched with the maximum incident angle in the sensor specification. This makes the maximum CRA principal ray angle of the optical system in the entire field of view match the maximum principal ray angle of the sensor, improves the edge light incident capability, improves the light energy utilization rate, and avoids color cast in the video image.

[0037] Furthermore,

[0038] The absolute value of the ratio of the focal length F1 of the first lens to the overall focal length F of the lens satisfies the following relationship: 0.6≤|F1 / F|≤1.13;

[0039] The absolute value of the ratio of the focal length F2 of the second lens to the overall focal length F of the lens satisfies the following relationship: 0.55≤|F2 / F|≤0.95;

[0040] The absolute value of the ratio of the focal length F3 of the third lens to the overall focal length F of the lens satisfies the following relationship: 1≤|F3 / F|≤1.6;

[0041] The absolute value of the ratio of the focal length F4 of the fourth lens to the overall focal length F of the lens satisfies the following relationship: 2.5≤|F4 / F|≤7;

[0042] The beneficial effect of this embodiment is that by rationally allocating the optical power of each lens in the system, the imaging performance of the optical system is improved.

[0043] Furthermore,

[0044] The refractive index N1 of the first lens satisfies the following relationship: 1.93≤N1≤2.33;

[0045] The dispersion coefficient V1 of the first lens satisfies the following relationship: 22≤V1≤32;

[0046] The refractive index N1 of the second lens satisfies the following relationship: 1.55≤N1≤1.95;

[0047] The dispersion coefficient V1 of the second lens satisfies the following relationship: 30≤V1≤40;

[0048] The refractive index N1 of the third lens satisfies the following relationship: 1.85≤N1≤2.25;

[0049] The dispersion coefficient V1 of the third lens satisfies the following relationship: 23≤V1≤33;

[0050] The refractive index N1 of the fourth lens satisfies the following relationship: 1.62≤N1≤2.25;

[0051] The dispersion coefficient V1 of the fourth lens satisfies the following relationship: 17≤V1≤47.

[0052] The beneficial effect of this embodiment is that by rationally allocating the refractive index and dispersion coefficient of each lens in the system, the imaging performance of the optical system is improved. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the optical path in Embodiment 1 of the present invention.

[0054] Figure 2 This is an MTF curve diagram of Embodiment 1 of the present invention.

[0055] Figure 3 This is a field distortion diagram of Embodiment 1 of the present invention.

[0056] Figure 4 This is a spherical aberration diagram from Embodiment 1 of the present invention.

[0057] Figure 5 This is a diffraction energy curve diagram of Embodiment 1 of the present invention.

[0058] Figure 6 This is a CRA curve diagram of Embodiment 1 of the present invention.

[0059] Figure 7 This is a schematic diagram of the optical path in Embodiment 2 of the present invention.

[0060] Figure 8 This is an MTF curve diagram of Embodiment 2 of the present invention.

[0061] Figure 9 This is a field distortion diagram of Embodiment 2 of the present invention.

[0062] Figure 10 This is a spherical aberration diagram from Embodiment 2 of the present invention.

[0063] Figure 11 This is a diffraction energy curve diagram of Embodiment 2 of the present invention.

[0064] Figure 12 This is a CRA curve diagram of Embodiment 2 of the present invention.

[0065] Figure 13 This is a schematic diagram of the optical path in Embodiment 3 of the present invention.

[0066] Figure 14 This is the MTF curve of Embodiment 3 of the present invention.

[0067] Figure 15 This is a field distortion diagram of Embodiment 3 of the present invention.

[0068] Figure 16 This is a spherical aberration diagram from Embodiment 3 of the present invention.

[0069] Figure 17 This is a diffraction energy curve diagram of Embodiment 3 of the present invention.

[0070] Figure 18 This is a CRA curve diagram of Embodiment 3 of the present invention.

[0071] Figure 19 This is a schematic diagram of the optical path in Embodiment 4 of the present invention.

[0072] Figure 20 This is the MTF curve of Embodiment 4 of the present invention.

[0073] Figure 21 This is a field distortion diagram of Embodiment 4 of the present invention.

[0074] Figure 22 This is a spherical aberration diagram from Embodiment 4 of the present invention.

[0075] Figure 23 This is a diffraction energy curve diagram of Embodiment 4 of the present invention.

[0076] Figure 24 This is a CRA curve diagram of Embodiment 4 of the present invention.

[0077] The above figures include the following reference numerals:

[0078] 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Filter; 6. Protective film; 7. Aperture. Detailed Implementation

[0079] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0080] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0081] Reference Figures 1 to 24 As shown, an in-vehicle monitoring lens includes a first lens 1, a second lens 2, a third lens 3, and a fourth lens 4 arranged sequentially along the optical axis from the object side to the image side. An aperture 7 is provided before the object side of the first lens 1, and a filter 5 and a protective sheet 6 are provided after the image side of the fourth lens 4.

[0082] The object-side surface of the first lens 1 is convex, and the first lens 1 has positive refractive power;

[0083] The object-side surface of the second lens 2 is concave, the image-side surface of the second lens 2 is concave, and the second lens 2 has negative refractive power;

[0084] The object-side surface of the third lens 3 is concave, the image-side surface of the third lens 3 is convex, and the third lens 3 has positive refractive power.

[0085] The object side of the fourth lens 4 is convex, the image side of the fourth lens 4 is concave, and the fourth lens 4 has positive refractive power.

[0086] The beneficial effects of this embodiment are as follows: by reasonably allocating the diopter of each lens, optimizing the surface shape, thickness and distance between each lens, the lens has good imaging quality. It adopts a four-element design, with fewer lenses, simple structure, small and compact size, convenient installation and use, and can save lens costs.

[0087] The filter 5 is an infrared IR 940nm filter 5, which enables the lens of the present invention to have excellent shaping effect at night.

[0088] The first lens 1 to the fourth lens 4 are all made of glass spherical surfaces, thus ensuring the imaging effect.

[0089] Furthermore, the image-side surface of the first lens 1 is a plane.

[0090] The beneficial effects of this embodiment are as follows: the image side of the first lens 1 is a plane, which can significantly improve the assembly accuracy of the optical system, reduce the complexity of the structural components, avoid increasing costs by digging steps on the image side of the first lens 1, or cause dust, scratches, tilting and other phenomena caused by direct contact between lenses.

[0091] Furthermore, the lens optical system satisfies the following relationship: 200≤DFOV*f≤300;

[0092] Where DFOV is the maximum field of view in degrees; f is the total focal length of the optical system in millimeters.

[0093] The beneficial effects of this embodiment are as follows: In order to solve the problem that the field of view of the lens monitoring in the prior art is too large or too small and cannot match the current specific field of view requirements, by setting 200≤DFOV*f≤300, the maximum field of view of the lens optical system of the present invention meets the actual use requirements, avoids the monitoring range of too small a field of view being too small, and avoids the waste of the lens imaging area caused by too large a field of view, resulting in a reduction in the pixel ratio of the image plane.

[0094] Furthermore, the field of view of the lens optical system and the corresponding imaging circle diameter satisfy the following relationship:

[0095] 8.6≤DFOV / D≤14.6, 8.7≤HFOV / H≤14.7, 8.8≤VFOV / V≤14.8;

[0096] Where D is the diagonal dimension of the sensor, H is the horizontal dimension of the sensor, and V is the vertical dimension of the sensor, all in millimeters;

[0097] DFOV is the object-side field of view angle of the optical system under the corresponding D imaging circle, in degrees;

[0098] HFOV is the object-side field of view angle of the optical system under the H imaging circle, in degrees;

[0099] VFOV is the object-side field of view angle of the optical system under the corresponding V imaging circle, in degrees.

[0100] The beneficial effects of this embodiment are as follows: Based on the geometric parameters such as field of view and sensor size, the theoretical value of the focal length is calculated. The focal length of the optical system is controlled to the target value through scaling of the initial structure. Based on this, the focal length control is released, thereby controlling the field of view of the optical system to the target value, so that the field of view of the optical system meets specific requirements, and the object-side field of view of the optical system corresponding to the diameters of the D, H, and V imaging rings meets specific requirements.

[0101] Furthermore, the back focal length of the lens optical system and the half-image height of the optical system satisfy the following relationship: 0.7≤BFL / y'≤1.3;

[0102] Where BFL is the back intercept of the optical system, and y' is the half-image height of the optical system.

[0103] The beneficial effects of this embodiment are as follows: In order to solve the problem that the back focal length of the lens in the prior art is relatively long, resulting in a long distance between the contact point between the lens and the base and the end point of the base, which is not conducive to temperature drift, by setting 0.7≤BFL / y'≤1.3, the lens of the present invention has a smaller back focal length. By controlling the back focal length of the optical system and shortening it as much as possible, and at the same time selecting a shorter base, the temperature drift performance of the optical system is improved, which is beneficial to significantly improving the temperature drift performance of the lens of the present invention.

[0104] Furthermore, the total length of the lens optical system and the half-image height of the optical system satisfy the following relationship: 3≤TTL / y'≤4;

[0105] Where TTL is the total length of the optical system and y' is the half-image height of the optical system.

[0106] The beneficial effects of this embodiment are: by setting 3≤TTL / y'≤4, it is beneficial to reduce the total length of the optical phase, realize the structural design requirements of compact miniaturization, reduce the space occupied by the lens, and facilitate integration.

[0107] Furthermore, the radii of curvature of the first lens 1 and the second lens 2 satisfy the following relationship: |L1R2|≥200, 1≤L2R2≤5;

[0108] Wherein, L1R2 is the radius of curvature of the image side surface of the first lens 1, and L2R2 is the radius of curvature of the image side surface of the second lens 2.

[0109] The beneficial effects of this embodiment are as follows: In order to solve the problem that the lens has relatively large optical distortion in the prior art, resulting in severe distortion of the photographed object and making it difficult to observe, by setting |L1R2|≥200 and 1≤L2R2≤5, the image side of the first lens 1 and the image side of the second lens 2 generate negative distortion to compensate for the distortion of other surfaces of the optical system, and control the remaining distortion of the optical system to a relatively small value, so that the total distortion of the optical system is small, thereby obtaining a video image with small distortion of the photographed object.

[0110] Furthermore, the radius of curvature of the fourth lens 4 and the maximum CRA of the lens optical system satisfy the following relationship:

[0111] 4.5≤L4R2≤9, 16°≤CRA≤23°;

[0112] Where L4R2 is the radius of curvature of the image side surface of the fourth lens 4, and CRA is the maximum CRA angle within the imaging field of view.

[0113] The beneficial effects of this embodiment are as follows: In order to solve the problem that the lens CRA principal ray angle is too small in the prior art and cannot match the maximum CRA principal ray angle of the sensor, by setting 4.5≤L4R2≤9 and 16°≤CRA≤23°, and by controlling the exit angle of the last surface of the optical system, the incident angle of the edge field of view on the image plane is matched with the maximum incident angle in the sensor specification. This makes the maximum CRA principal ray angle of the optical system in the entire field of view match the maximum principal ray angle of the sensor, improves the edge light incident capability, improves the light energy utilization rate, and avoids color cast in the video image.

[0114] Furthermore,

[0115] The absolute value of the ratio of the focal length F1 of the first lens 1 to the overall focal length F of the lens satisfies the following relationship: 0.6≤|F1 / F|≤1.13;

[0116] The absolute value of the ratio of the focal length F2 of the second lens 2 to the overall focal length F of the lens satisfies the following relationship: 0.55≤|F2 / F|≤0.95;

[0117] The absolute value of the ratio of the focal length F3 of the third lens 3 to the overall focal length F of the lens satisfies the following relationship: 1≤|F3 / F|≤1.6;

[0118] The absolute value of the ratio of the focal length F4 of the fourth lens 4 to the overall focal length F of the lens satisfies the following relationship: 2.5≤|F4 / F|≤7.

[0119] The beneficial effect of this embodiment is that by rationally allocating the optical power of each lens in the system, the imaging performance of the optical system is improved.

[0120] Furthermore,

[0121] The refractive index N1 of the first lens 1 satisfies the following relationship: 1.93≤N1≤2.33;

[0122] The dispersion coefficient V1 of the first lens 1 satisfies the following relationship: 22≤V1≤32;

[0123] The refractive index N1 of the second lens 2 satisfies the following relationship: 1.55≤N1≤1.95;

[0124] The dispersion coefficient V1 of the second lens 2 satisfies the following relationship: 30≤V1≤40;

[0125] The refractive index N1 of the third lens 3 satisfies the following relationship: 1.85≤N1≤2.25;

[0126] The dispersion coefficient V1 of the third lens 3 satisfies the following relationship: 23≤V1≤33;

[0127] The refractive index N1 of the fourth lens 4 satisfies the following relationship: 1.62≤N1≤2.25;

[0128] The dispersion coefficient V1 of the fourth lens 4 satisfies the following relationship: 17≤V1≤47.

[0129] The beneficial effect of this embodiment is that by rationally allocating the refractive index and dispersion coefficient of each lens in the system, the imaging performance of the optical system is improved.

[0130] The present invention provides detailed optical data for embodiments one to four, as shown in Tables 1-1 to 1-4.

[0131] Table 1-1 shows the detailed optical data for the corresponding embodiment when the lens focal length f is 4.8mm, the lens aperture F is 2.1, the lens field of view (FOV) is 52.7°, and the total length of the lens optical system is 8.9mm:

[0132]

[0133] Table 1-2 shows the detailed optical data for the corresponding embodiments when the lens focal length f is 4.8mm, the lens aperture f is 2.1, the lens field of view (FOV) is 52.7°, and the total length of the lens optical system is 8.9mm:

[0134]

[0135] Table 1-3 shows the detailed optical data for the corresponding embodiments when the lens focal length f is 4.84mm, the lens aperture F is 2.1, the lens field of view (FOV) is 52.7°, and the total length of the lens optical system is 8.9mm:

[0136]

[0137] Table 1-4 shows the detailed optical data for the corresponding embodiments when the lens focal length f is 4.83mm, the lens aperture F is 2.1, the lens field of view (FOV) is 52.7°, and the total length of the lens optical system is 9mm:

[0138]

[0139] Figure 1 , Figure 7 , Figure 13 , Figure 19 These are optical path diagrams for Embodiments 1 to 4 of the present invention. As can be seen from the diagrams, the optical system consists of four lenses: a fifth lens (filter 5) and a sixth lens (protective lens 6). The system has a small number of lenses, a simple structure, and a compact size. The aperture stop 7 is positioned before the first lens 1, serving as the frame of the optical system. Light rays converge after passing through the first lens 1, diverge after passing through the second lens 2, and undergo a small angle change after passing through the third lens 3. The fourth lens 4 shifts the light rays while reducing their tilt angle, ultimately causing all light rays to converge on the image plane.

[0140] Figure 2 This is an MTF curve diagram of Embodiment 1 of the present invention. As can be seen from the figure, the MTF at the center field of view is 0.6 at 83 l p / mm, and the MTF at the 1.0 field of view is 0.24 at 83 l p / mm. The MTF curve is concentrated, with no drop in low frequencies, resulting in a relatively high MTF. The area enclosed by the MTF curve and the coordinate axes is large. This figure indicates that the optical system has good resolution and can meet the application requirements of a 1 / 4-inch near-infrared sensor.

[0141] Figure 3 This is a field curvature distortion diagram of Embodiment 1 of the present invention. The left image is the field curvature diagram, and the right image is the F-axis optical distortion diagram. From the left image, it can be clearly seen that the lens exhibits an S-shaped field curvature, with a maximum field curvature within 0.05mm. The overlap between meridional and sagittal rays across the entire field of view is good, indicating that the lens has good astigmatism correction. From the right image, it can be clearly seen that the maximum optical distortion of the lens is within -5%, indicating a small degree of distortion that meets the requirements for naked-eye observation.

[0142] Figure 4 This is a spherical aberration diagram of Embodiment 1 of the present invention. As can be seen from the diagram, the center spherical aberration of the lens is 0.042 mm, the full field-of-view spherical aberration is -0.031 mm, and the maximum spherical aberration is -0.073 mm. The optical system exhibits good spherical aberration correction.

[0143] Figure 5This is a diffraction energy curve of Embodiment 1 of the present invention. As can be seen from the figure, when the energy is 80%, the radius of the centroid star spot is approximately 8.7 μm, which is relatively small, indicating good lens formation.

[0144] Figure 6 This is a CRA curve diagram of Embodiment 1 of the present invention. As can be seen from the diagram, the CRA curve of this optical system is approximately a straight line, with a maximum CRA of 19.5° at a field of view of 1.0. This matches well with the maximum CRA of the sensor, avoiding color shift in the video image.

[0145] Figure 8 This is an MTF curve diagram of Embodiment 2 of the present invention. As can be seen from the figure, the MTF at the center field of view is 0.48 at 83 l p / mm, and the MTF at the 1.0 field of view is 0.39 at 83 l p / mm. The MTF curve is concentrated, with no drop in low frequencies, resulting in a relatively high MTF. The area enclosed by the MTF curve and the coordinate axes is large. This figure indicates that the optical system has good resolution and can meet the application requirements of a 1 / 4-inch near-infrared sensor.

[0146] Figure 9 This is a field curvature distortion diagram of Embodiment 2 of the present invention. The left image is the field curvature diagram, and the right image is the F-axis optical distortion diagram. From the left image, it can be clearly seen that the lens exhibits an S-shaped field curvature with a maximum curvature of approximately 0.05mm. The overlap between the meridional and sagittal rays across the entire field of view is good, indicating that the lens has good astigmatism correction. From the right image, it can be clearly seen that the maximum optical distortion of the lens is within -5%, indicating a small degree of deformation that meets the requirements for naked-eye observation.

[0147] Figure 10 This is a spherical aberration diagram for Embodiment 2 of the present invention. From the diagram, it can be seen that the center spherical aberration of the lens is 0.056 mm, the full field-of-view spherical aberration is -0.044 mm, and the maximum spherical aberration is -0.1 mm. The optical system exhibits good spherical aberration correction.

[0148] Figure 11 This is a diffraction energy curve of Embodiment 2 of the present invention. It can be seen from the figure that when the energy is 80%, the radius of the centroid star spot is approximately 10 μm, which is relatively small, indicating good lens formation.

[0149] Figure 12 This is a CRA curve diagram of Embodiment 2 of the present invention. As can be seen from the diagram, the CRA curve of this optical system is approximately a straight line, with a maximum CRA of 20.4° at a field of view of 1.0. This matches well with the maximum CRA of the sensor, avoiding color shift in the video image.

[0150] Figure 14This is the MTF curve of Embodiment 3 of the present invention. As can be seen from the figure, the MTF at the center field of view is 0.49 at 83 l p / mm, and the MTF at the 1.0 field of view is 0.33 at 83 l p / mm. The MTF curve is concentrated, with no drop in low frequencies, resulting in a relatively high MTF. The area enclosed by the MTF curve and the coordinate axes is large. This figure indicates that the optical system has good resolution and can meet the application requirements of a 1 / 4-inch near-infrared sensor.

[0151] Figure 15 This is a field curvature distortion diagram of Embodiment 3 of the present invention. The left image is the field curvature diagram, and the right image is the F-axis optical distortion diagram. From the left image, it can be clearly seen that the field curvature of this lens is approximately straight, with a slight S-shape. The maximum field curvature is within 0.1mm, and the overlap between the meridional and sagittal rays across the entire field of view is good, indicating that the lens has good astigmatism correction. From the right image, it can be clearly seen that the maximum optical distortion of the lens is within -5%, and the degree of distortion is not significant, meeting the requirements for naked-eye observation.

[0152] Figure 16 This is a spherical aberration diagram for Embodiment 3 of the present invention. From the diagram, it can be seen that the center spherical aberration of the lens is 0.056 mm, the full field-of-view spherical aberration is -0.043 mm, and the maximum spherical aberration is -0.099 mm. The optical system exhibits good spherical aberration correction.

[0153] Figure 17 This is a diffraction energy curve of Embodiment 3 of the present invention. As can be seen from the figure, when the energy is 80%, the radius of the centroid star spot is approximately 9 μm, which is relatively small, indicating good lens formation.

[0154] Figure 18 This is the CRA curve diagram of Embodiment 3 of the present invention. As can be seen from the figure, the CRA curve of this optical system is approximately a straight line, with a maximum CRA of 19.5° at a field of view of 1.0. This matches well with the maximum CRA of the sensor, avoiding color shift in the video image.

[0155] Figure 20 This is the MTF curve diagram of Embodiment 4 of the present invention. As can be seen from the figure, the MTF at the center field of view is 0.53 at 83 l p / mm, and the MTF at the 1.0 field of view is 0.36 at 83 l p / mm. The MTF curve is concentrated, with no drop in low frequencies, resulting in a relatively high MTF. The area enclosed by the MTF curve and the coordinate axes is large. This figure indicates that the optical system has good resolution and can meet the application requirements of a 1 / 4-inch near-infrared sensor.

[0156] Figure 21This is a field curvature distortion diagram of Embodiment 4 of the present invention. The left image is the field curvature diagram, and the right image is the F-axis optical distortion diagram. From the left image, it can be clearly seen that the field curvature of this lens is approximately straight, with a slight S-shape. The maximum field curvature is less than 0.1 mm. The meridional rays and sagittal rays in the entire field of view are slightly different, but the value is very small, and the surface astigmatism correction is good. From the right image, it can be clearly seen that the maximum optical distortion of the lens is within -5%, and the degree of deformation is not significant, meeting the requirements for naked-eye observation.

[0157] Figure 22 This is a spherical aberration diagram for Embodiment 4 of the present invention. From the diagram, it can be seen that the center spherical aberration of the lens is 0.052 mm, the full field-of-view spherical aberration is -0.045 mm, and the maximum spherical aberration is -0.097 mm. The optical system exhibits good spherical aberration correction.

[0158] Figure 23 This is the diffraction energy curve of Embodiment 4 of the present invention. From the graph, it can be concluded that when the energy is 80%, the radius of the centroid star spot is approximately 8 μm, indicating good lens formation.

[0159] Figure 24 This is the CRA curve diagram of Embodiment 4 of the present invention. From the diagram, it can be seen that the CRA curve of this optical system is approximately a straight line, with a maximum CRA of 19.6° at a field of view of 1.0. This matches well with the maximum CRA of the sensor, avoiding color shift in the video image.

[0160] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. An in-vehicle monitoring camera, characterized in that: It consists of a first lens, a second lens, a third lens, and a fourth lens arranged sequentially along the optical axis from the object side to the image side, wherein: The object-side surface of the first lens is convex, and the first lens has positive refractive power; The object-side surface of the second lens is concave, the image-side surface of the second lens is concave, and the second lens has negative refractive power. The object-side surface of the third lens is concave, the image-side surface of the third lens is convex, and the third lens has positive refractive power. The object-side surface of the fourth lens is convex, the image-side surface of the fourth lens is concave, and the fourth lens has positive refractive power. The image-side surface of the first lens is a plane; The focal length of the first lens The absolute value of the ratio to the overall focal length F of the lens satisfies the following relationship: 0.6 ≤ / F ≤1.13; The focal length of the second lens The absolute value of the ratio to the overall focal length F of the lens satisfies the following relationship: 0.55 ≤ / F ≤0.95; The focal length of the third lens The absolute value of the ratio to the overall focal length F of the lens satisfies the following relationship: 1 ≤ / F ≤1.6; The focal length of the fourth lens The absolute value of the ratio of the total focal length F of the lens to the total focal length F of the lens satisfies the following relationship: 2.5 ≤ / F ≤7.

2. The in-vehicle monitoring camera according to claim 1, characterized in that: The lens optical system satisfies the following relationship: 200≤DFOV*f≤300; Where DFOV is the maximum field of view in degrees; f is the total focal length of the optical system in millimeters.

3. The in-vehicle monitoring camera according to claim 1, characterized in that: The field of view of the lens optical system and the corresponding imaging circle diameter satisfy the following relationship: 8.6≤DFOV / D≤14.6, 8.7≤HFOV / H≤14.7, 8.8≤VFOV / V≤14.8; Where D is the diagonal dimension of the sensor, H is the horizontal dimension of the sensor, and V is the vertical dimension of the sensor, all in millimeters; DFOV is the object-side field of view angle of the optical system under the corresponding D imaging circle, in degrees; HFOV is the object-side field of view angle of the optical system under the H imaging circle, in degrees; VFOV is the object-side field of view angle of the optical system under the corresponding V imaging circle, in degrees.

4. The in-vehicle monitoring camera according to claim 1, characterized in that: The back focal length of the lens optical system and the half-image height of the optical system satisfy the following relationship: 0.7≤BFL / y'≤1.3; Where BFL is the back intercept of the optical system, and y' is the half-image height of the optical system.

5. The in-vehicle monitoring camera according to claim 1, characterized in that: The total length of the lens optical system and the half-image height of the optical system satisfy the following relationship: 3≤TTL / y'≤4; Where TTL is the total length of the optical system and y' is the half-image height of the optical system.

6. The in-vehicle monitoring camera according to claim 1, characterized in that: The radii of curvature of the first lens and the second lens satisfy the following relationship: |L1R2|≥200, 1≤L2R2≤5; Wherein, L1R2 is the radius of curvature of the image-side surface of the first lens, and L2R2 is the radius of curvature of the image-side surface of the second lens.

7. The in-vehicle monitoring camera according to claim 1, characterized in that: The radius of curvature of the fourth lens and the maximum CRA of the lens optical system satisfy the following relationships: 4.5≤L4R2≤9, 16°≤CRA≤23°. Where L4R2 is the radius of curvature of the image side surface of the fourth lens, and CRA is the maximum CRA angle within the imaging field of view.

8. An in-vehicle monitoring camera according to claim 1, characterized in that: The refractive index N1 of the first lens satisfies the following relationship: 1.93≤N1≤2.33; The dispersion coefficient V1 of the first lens satisfies the following relationship: 22≤V1≤32; The refractive index N1 of the second lens satisfies the following relationship: 1.55≤N1≤1.95; The dispersion coefficient V1 of the second lens satisfies the following relationship: 30≤V1≤40; The refractive index N1 of the third lens satisfies the following relationship: 1.85≤N1≤2.25; The dispersion coefficient V1 of the third lens satisfies the following relationship: 23≤V1≤33; The refractive index N1 of the fourth lens satisfies the following relationship: 1.62≤N1≤2.25; The dispersion coefficient V1 of the fourth lens satisfies the following relationship: 17≤V1≤47.

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