Fixed-focus optical system and vehicle-mounted lens
By designing a fixed-focus optical system composed of multiple lenses and photosensitive chips, the problem of poor imaging quality of vehicle-mounted DMS lenses in complex temperature differences is solved, and high resolution, low temperature drift and miniaturization imaging effects are achieved.
Patent Information
- Application Number
- CN202411662989.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-20
- Publication Date
- 2025-02-28
AI Technical Summary
Existing automotive DMS lenses cannot guarantee better imaging quality in complex and large temperature differences, resulting in low resolution, severe temperature drift and large volume.
A fixed-focus optical system is designed, including a structure composed of a first lens, a diaphragm, a second lens, a third lens, a fourth lens and a photosensitive chip. The light trend is controlled through the first lens with negative power and the second lens with positive power, and the light power is reasonably allocated by the combination of different lenses, so as to achieve high resolution, low temperature drift and miniaturization.
It achieves high resolution, low temperature drift, small size and bright image imaging effects, improving the performance and reliability of the lens.
Smart Images
Figure CN119535725A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of optical technology, and in particular to a fixed-focus optical system and a vehicle-mounted lens. Background Art
[0002] With the development of automobile intelligence and autonomous driving technology, driver monitoring system (DMS) has gradually become an important part of automobile safety. DMS monitors the driver's status in real time through cameras, such as fatigue driving, distraction, etc., so as to issue alarms in time to ensure driving safety. One of the core components of DMS is the camera lens, and its imaging quality directly affects the performance and reliability of the system.
[0003] Currently, most vehicle-mounted DMS lenses are made of glass lenses, and some glass-plastic hybrid designs cannot guarantee optimal imaging quality in complex environments with large temperature differences. Summary of the invention
[0004] The main purpose of the present invention is to provide a fixed-focus optical system and a vehicle-mounted lens, aiming to improve the resolution, achieve miniaturization, low temperature drift, and better imaging effect.
[0005] To achieve the above object, the present invention provides a fixed-focus optical system, wherein the fixed-focus optical system has an object side and an image side that are arranged opposite to each other along the optical axis direction, and the fixed-focus optical system is composed of a first lens, an aperture, a second lens, a third lens, a fourth lens, and a photosensitive chip that are arranged in sequence from the object side to the image side;
[0006] Wherein, the first lens has a negative optical power, a convex object side surface, and a concave image side surface;
[0007] The second lens has positive optical power, a convex object side surface and a convex image side surface;
[0008] The third lens has positive optical power, a concave object side surface, and a convex image side surface;
[0009] The fourth lens has negative optical power, a concave object-side surface, and a concave image-side surface.
[0010] In one embodiment, the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, and the focal length of the fourth lens is f4. The focal lengths of the first lens, the second lens, the third lens, and the fourth lens satisfy the following relationship: 6mm<|f1|<10mm, 4mm<|f2|<7mm, 2mm<|f3|<4.5mm, 3mm<|f4|<6.5mm.
[0011] In one embodiment, the refractive index of the first lens is n1, the refractive index of the second lens is n2, the refractive index of the third lens is n3, and the refractive index of the fourth lens is n4. The refractive indices of the first lens, the second lens, the third lens and the fourth lens satisfy the following relationship: 1.60≤n1≤1.90, 1.80≤n2≤2.05, 1.70≤n3≤2.05, and 1.50≤n4≤1.70.
[0012] In one embodiment, the dispersion coefficient of the first lens is v1, the dispersion coefficient of the second lens is v2, the dispersion coefficient of the third lens is v3, and the dispersion coefficient of the fourth lens is v4. The dispersion coefficients of the first lens, the second lens, the third lens and the fourth lens satisfy the following relationship: 40.0≤v1≤60.0, 18.0≤v2≤40.0, 25.0≤v3≤50.0, 50≤v4≤75.
[0013] In one embodiment, the image plane diameter of the photosensitive chip is IC, wherein IC≤4.8 mm.
[0014] In one embodiment, the first lens and the third lens are aspherical lenses, and the second lens and the fourth lens are spherical lenses.
[0015] In one embodiment, the total optical length of the fixed-focus optical system is TTL, and the effective focal length of the fixed-focus optical system is EFL, wherein TTL / EFL≤2.3.
[0016] In one embodiment, the aperture value of the fixed-focus optical system is F, wherein 2.2≤F≤2.4.
[0017] In one embodiment, the fixed-focus optical system includes a filter, and the filter is arranged between the fourth lens and the photosensitive chip along the optical axis; and / or,
[0018] The fixed-focus optical system also includes a protective glass, which is arranged between the fourth lens and the photosensitive chip along the optical axis and is arranged close to the photosensitive chip.
[0019] The present invention further provides a vehicle-mounted lens, comprising a fixed-focus optical system, wherein the fixed-focus optical system has an object side and an image side that are arranged opposite to each other along an optical axis direction, and the fixed-focus optical system is composed of a first lens, an aperture, a second lens, a third lens, a fourth lens, and a photosensitive chip that are sequentially arranged from the object side to the image side;
[0020] Wherein, the first lens has a negative optical power, a convex object side surface, and a concave image side surface;
[0021] The second lens has positive optical power, a convex object side surface and a convex image side surface;
[0022] The third lens has positive optical power, a concave object side surface, and a convex image side surface;
[0023] The fourth lens has negative optical power, a concave object-side surface, and a concave image-side surface.
[0024] The technical solution of the present invention is conducive to the control of temperature drift of the optical system and the control and collection of light entering the entire optical system by setting the first lens with negative optical power and the second lens with positive optical power. By comprehensively setting the optical power of each lens, the lens can well control the trend of light, while introducing more light and making the structure more compact, and by combining different lenses and reasonably allocating optical power, the resolution is high, the temperature drift is low, the volume is small, the picture is bright, and the imaging effect is better. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 the structures shown in these drawings without paying creative work.
[0026] Figure 1 A schematic structural diagram of an embodiment of a fixed-focus optical system provided by the present invention;
[0027] Figure 2 for Figure 1 A schematic diagram of an MTF curve of an embodiment of a medium fixed focus optical system;
[0028] Figure 3 for Figure 1 A schematic diagram of an MTF curve of another embodiment of a medium fixed-focus optical system.
[0029] Description of Figure Numbers:
[0030] 100. Fixed-focus optical system; 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Aperture; 6. Photosensitive chip; 7. Filter; 8. Protective glass.
[0031] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION
[0032] 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 described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0033] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.
[0034] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.
[0035] The present invention provides a fixed-focus optical system 100 .
[0036] First of all, it is important to understand that the focal power is equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam, and it characterizes the ability of the optical system to deflect light. The larger the absolute value of the focal power, the stronger the ability to bend light, and the smaller the absolute value of the focal power, the weaker the ability to bend light. When the focal power is a positive number, the refraction of light is convergent; when the focal power is a negative number, the refraction of light is divergent. The focal power can be used to characterize a certain refractive surface of a lens, a certain lens, or a system formed by multiple lenses.
[0037] See also Figure 1In one embodiment of the present invention, the fixed-focus optical system 100 has an object side and an image side which are arranged opposite to each other along the optical axis direction, and the fixed-focus optical system 100 is composed of a first lens 1, an aperture 5, a second lens 2, a third lens 3, a fourth lens 4 and a photosensitive chip 6 which are arranged in sequence from the object side to the image side; wherein the first lens 1 has a negative focal power, an object side surface is a convex surface, and an image side surface is a concave surface; the second lens 2 has a positive focal power, an object side surface is a convex surface, and an image side surface is a convex surface; the third lens 3 has a positive focal power, an object side surface is a concave surface, and an image side surface is a convex surface; the fourth lens 4 has a negative focal power, a object side surface is a concave surface, and an image side surface is a concave surface.
[0038] The first lens 1 has a positive optical power, a convex object side surface, and a concave image side surface, which can introduce more light, thereby making the fixed-focus optical system 100 have a small volume; the aperture 5 is arranged between the first lens 1 and the second lens 2, and can adjust the field of view, block the far-axis light, and prevent the far-axis light from affecting the imaging quality, improve the image quality, and make the lens have a large light throughput; the second lens 2 has a concave object side surface and a concave image side surface, and the third lens 3 has a convex object side surface and a convex image side surface. Through such an arrangement, the concave and convex sides of the second lens 2 and the third lens 3 complement each other, are more fitted, and have a more compact structure; in addition, it is also ensured that the second lens 2 has a positive optical power and the third lens 3 has a positive optical power, which controls the light trend and improves the resolution.
[0039] In the technical solution of the present invention, by setting a first lens 1 with negative optical power and a second lens 2 with positive optical power, the overall focal length is maintained stable, thermal compensation is achieved, and it is beneficial to control the temperature drift of the optical system and control and collect the light entering the entire optical system. By comprehensively setting the optical power of each lens, the lens can well control the light trend, introduce more light and make the structure more compact, and by combining different lenses and reasonably allocating optical power, the resolution is high, the temperature drift is low, the volume is small, the picture is bright, and the imaging effect is better.
[0040] See also Figure 2In one embodiment of the present invention, it should be understood that the focal length refers to the distance from the rear surface of the lens to the image plane in the optical system. The focal length determines the magnification and viewing angle of the image. The focal power is the reciprocal of the focal length. The focal length of the first lens 1 is f1, the focal length of the second lens 2 is f2, the focal length of the third lens 3 is f3, and the focal length of the fourth lens is f4. The focal lengths of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 satisfy the following relationship: 6mm<|f1|<10mm, 4mm<|f2|<7mm, 2mm<|f3|<4.5mm, 3mm<|f4|<6.5mm. By combining different lenses and reasonably allocating the focal power, the optical system has a small volume and improves the resolution of the fixed-focus optical system 100. In addition, by reasonably setting the focal length ratio, the lens does not defocus under environmental conditions of -40°C to +105°C, and the working performance is more stable.
[0041] In one embodiment of the present invention, the refractive index of the first lens 1 is n1, the refractive index of the second lens 2 is n2, the refractive index of the third lens 3 is n3, and the refractive index of the fourth lens 4 is n4. The refractive indices of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 satisfy the following relationship: 1.60≤n1≤1.90, 1.80≤n2≤2.05, 1.70≤n3≤2.05, 1.50≤n4≤1.70. By controlling the refractive indices of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4, the refraction angle and path of the light can be more finely controlled, thereby ensuring that the light converges to the correct position to form a clear, distortion-free image. This helps to improve the sharpness and color accuracy of the picture.
[0042] In one embodiment of the present invention, the dispersion coefficient of the first lens 1 is v1, the dispersion coefficient of the second lens 2 is v2, the dispersion coefficient of the third lens 3 is v3, and the dispersion coefficient of the fourth lens 4 is v4. The dispersion coefficients of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4 satisfy the following relationship: 40.0≤v1≤60.0, 18.0≤v2≤40.0, 25.0≤v3≤50.0, 50≤v4≤75; it can be understood that different colors of light will be refracted to different degrees when passing through the lens due to their different wavelengths, resulting in different focusing positions, forming chromatic aberration, and affecting the clarity and color accuracy of the image. By limiting the dispersion coefficients of the first lens 1, the second lens 2, the third lens 3, and the fourth lens 4, the refractive index differences of light of various wavelengths can be effectively balanced, chromatic aberration can be reduced, and the image edge can be clearer and the color transition can be natural.
[0043] In one embodiment of the present invention, it can be understood that when the light-emitting surface is too large, the photosensitive chip 6 cannot collect all the light, affecting the imaging quality. For this reason, the image plane diameter of the photosensitive chip 6 is IC, where IC≤4.8mm, so that the fixed-focus optical system 100 can collect the complete image and improve the imaging effect.
[0044] See also Figure 1 In one embodiment of the present invention, the first lens 1 and the third lens 3 are aspherical lenses, and the second lens 2 and the fourth lens 4 are spherical lenses.
[0045] It can be understood that the characteristics of aspherical lenses are: the curvature changes continuously from the center of the lens to the periphery of the lens. Unlike spherical lenses with constant curvature from the center of the lens to the periphery of the lens, aspherical lenses have better curvature radius characteristics and have the advantages of improving distortion aberration and improving astigmatism aberration. After using aspherical lenses, the aberrations that occur during imaging can be eliminated as much as possible, thereby improving the imaging quality of the lens.
[0046] Specifically, in one embodiment of the present invention, the surface shape of the aspheric lens in the projection optical system should satisfy the following equation:
[0047]
[0048] Among them, c is the curvature corresponding to the radius; y is the radial coordinate (its unit is the same as the lens length unit); k is the conic quadratic curve coefficient, and A, B, C, D, E, F, G... represent the fourth-order, sixth-order, eighth-order, tenth-order, twelfth-order, fourteenth-order, sixteenth-order... aspheric coefficients respectively.
[0049] Specifically, in one embodiment of the present invention, the focal length of the fixed-focus optical system is f=3.9 mm, the aperture value is F=2.4, the image plane diameter is 4.8 mm, the diagonal field angle is 69.0°, and the parameters of the fixed-focus optical system are shown in Table 1 below, and the even-order coefficients of each aspheric surface are shown in Table 2 below.
[0050] The above parameters can be used to accurately set the shape and size of the lens' aspheric surface to correct distortion and eliminate aberrations that occur during imaging as much as possible, thereby improving the imaging quality of the lens. It can also be used to correct pupil aberrations caused by large apertures, thereby improving the imaging quality of the system. At the same time, it greatly reduces the number of spherical lenses set and reduces the system volume.
[0051] Table 1
[0052]
[0053]
[0054] Table 2
[0055]
[0056] Figure 2 FIG. 1 is a schematic diagram of an MTF curve of an embodiment of the present invention. Figure 2 It can be seen that the fixed-focus lens provided in this embodiment has good imaging capability.
[0057] In addition, in another embodiment of the present invention, the focal length of the fixed-focus optical system is f=4.85 mm, the aperture value is F=2.4, the image plane diameter is 4.8 mm, the diagonal field angle is 69.0°, and the parameters of the fixed-focus optical system are shown in Table 3 below, and the even-order coefficients of each aspheric surface are shown in Table 4 below.
[0058] The above parameters can be used to accurately set the shape and size of the lens' aspheric surface to correct distortion and eliminate aberrations that occur during imaging as much as possible, thereby improving the imaging quality of the lens. It can also be used to correct pupil aberrations caused by large apertures, thereby improving the imaging quality of the system. At the same time, it greatly reduces the number of spherical lenses set and reduces the system volume.
[0059] Table 3
[0060]
[0061] Table 4
[0062]
[0063] Figure 3 FIG. 1 is a schematic diagram of an MTF curve of another embodiment of the present invention. Figure 3 It can be seen that the fixed-focus lens provided in this embodiment also has good imaging capabilities.
[0064] In one embodiment of the present invention, the total optical length of the fixed-focus optical system 100, that is, the distance from the object side vertex of the first lens 1 to the photosensitive chip 6 is TTL, and the effective focal length of the fixed-focus optical system 100 is EFL, wherein TTL / EFL≤2.3; by limiting the total optical length, the volume of the fixed-focus lens can be further reduced, which is conducive to the miniaturization of the fixed-focus lens.
[0065] In one embodiment of the present invention, the aperture value of the fixed-focus optical system 100 is F, wherein 2.2≤F≤2.4; when the aperture value F of the fixed-focus optical system 100 is within this range, the resolution and contrast of the lens are optimal, and the lens has a large light transmittance, high picture brightness, and better imaging effect.
[0066] In one embodiment of the present invention, the fixed-focus optical system 100 includes a filter 7, which is arranged between the fourth lens 4 and the photosensitive chip 6 along the optical axis; and / or, the fixed-focus optical system 100 also includes a protective glass 8, which is arranged between the fourth lens 4 and the photosensitive chip 6 along the optical axis and is arranged close to the photosensitive chip 6.
[0067] The filter 7 can filter out stray light to prevent the stray light from reaching the photosensitive chip 6 and interfering with normal visible light imaging, thereby improving the imaging quality. The protective glass 8 is arranged close to the photosensitive chip 6 to provide effective protection for the photosensitive chip 6.
[0068] It can be understood that the filter 7 and the protective glass 8 can be set separately, and in order to provide a better imaging effect, the filter 7 and the protective glass 8 can also be set at the same time, and the light carrying the information of the subject can pass through the first lens 1, the aperture 5, the second lens 2, the third lens 3, the fourth lens 4, the filter 7 and the protective glass 8 in sequence and finally be imaged on the photosensitive chip 6.
[0069] The present invention also proposes a vehicle-mounted lens, which includes a fixed-focus optical system. The specific structure of the fixed-focus optical system refers to the above-mentioned embodiment. Since the vehicle-mounted lens adopts all the technical solutions of all the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here one by one.
[0070] The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.
Claims
1. A fixed-focus optical system, characterized in that: The fixed-focus optical system has an object side and an image side that are arranged opposite to each other along the optical axis direction, and the fixed-focus optical system is composed of a first lens, an aperture, a second lens, a third lens, a fourth lens, and a photosensitive chip that are arranged in sequence from the object side to the image side; Wherein, the first lens has a negative optical power, a convex object side surface, and a concave image side surface; The second lens has positive optical power, a convex object side surface and a convex image side surface; The third lens has positive optical power, a concave object side surface, and a convex image side surface; The fourth lens has negative optical power, a concave object-side surface, and a concave image-side surface.
2. The fixed-focus optical system according to claim 1, wherein: The focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, and the focal length of the fourth lens is f4. The focal lengths of the first lens, the second lens, the third lens, and the fourth lens satisfy the following relationship: 6mm<|f1|<10mm, 4mm<|f2|<7mm, 2mm<|f3|<4.5mm, 3mm<|f4|<6.5mm.
3. The fixed-focus optical system according to claim 1, wherein: The refractive index of the first lens is n1, the refractive index of the second lens is n2, the refractive index of the third lens is n3, and the refractive index of the fourth lens is n4. The refractive indices of the first lens, the second lens, the third lens and the fourth lens satisfy the following relationship: 1.60≤n1≤1.90, 1.80≤n2≤2.05, 1.70≤n3≤2.05, and 1.50≤n4≤1.
70.
4. The fixed-focus optical system according to claim 1, wherein: The dispersion coefficient of the first lens is v1, the dispersion coefficient of the second lens is v2, the dispersion coefficient of the third lens is v3, and the dispersion coefficient of the fourth lens is v4. The dispersion coefficients of the first lens, the second lens, the third lens and the fourth lens satisfy the following relationship: 40.0≤v1≤60.0, 18.0≤v2≤40.0, 25.0≤v3≤50.0, 50≤v4≤75.
5. The fixed-focus optical system according to claim 1, wherein: The image plane diameter of the photosensitive chip is IC, where IC≤4.8mm.
6. The fixed-focus optical system according to claim 1, wherein: The first lens and the third lens are aspherical lenses, and the second lens and the fourth lens are spherical lenses.
7. The fixed-focus optical system according to claim 1, wherein: The total optical length of the fixed-focus optical system is TTL, and the effective focal length of the fixed-focus optical system is EFL, wherein TTL / EFL≤2.
3.
8. The fixed-focus optical system according to claim 1, wherein: The aperture value of the fixed-focus optical system is F, wherein 2.2≤F≤2.
4.
9. The fixed-focus optical system according to claim 1, wherein: The fixed-focus optical system comprises a filter, and the filter is arranged between the fourth lens and the photosensitive chip along the optical axis; and / or, The fixed-focus optical system also includes a protective glass, which is arranged between the fourth lens and the photosensitive chip along the optical axis and is arranged close to the photosensitive chip.
10. A vehicle-mounted lens, characterized in that: Comprising the fixed-focus optical system as described in any one of claims 1 to 9.