Wide-angle lens for laser radar

Abstract

The invention relates to the field of optical imaging lenses, in particular to a wide-angle lens for laser radar, which comprises a lens cone, and a first lens, a second lens, a third lens and an image plane are sequentially arranged in the lens cone. The R1 surface of the first lens is a convex surface at the optical axis, the R2 surface of the first lens is a conical concave surface at the optical axis, and an empty hole is formed in the edge of the R2 surface of the first lens; the R1 surface of the second lens is a convex surface at the optical axis, and the R2 surface of the second lens is a concave surface at the optical axis; the R1 surface of the third lens is a convex surface at the optical axis, and the R2 surface of the third lens is a convex surface at the optical axis. By adopting the technical scheme of the invention, a wide-angle lens category with a large field angle, short focus and high cost performance can be provided.

Description

Technical Field

[0001] This invention relates to the field of optical imaging lens technology, and more specifically, to a wide-angle lens for lidar. Background Technology

[0002] As a core sensor for environmental perception, LiDAR (Light Detection and Ranging) generates high-precision 3D point cloud data by emitting laser beams and receiving reflected signals from targets. It has become an indispensable key device in fields such as autonomous driving, robot navigation, drone obstacle avoidance, and high-precision surveying. With the continuous expansion of application scenarios, the market is placing more stringent demands on the performance, size, and cost of LiDAR. The optical receiving lens, as the "eye" of the LiDAR system, directly determines the overall performance, integration difficulty, and market competitiveness of the radar system through its field of view, light transmission, size, and manufacturing cost.

[0003] Currently, receiving lenses used in LiDAR typically employ a structure combining multiple spherical glass lenses to achieve a large detection range while ensuring image quality. However, obtaining a larger field of view (e.g., exceeding 120°) requires complex lens combinations to correct aberrations caused by the large field of view, resulting in bulky lenses and long total optical length (TTL), which is detrimental to the miniaturization and weight reduction of the device. Traditional multi-element spherical glass lenses have a large number of lenses, and the cold processing or molding aspherical processes for glass lenses are costly, resulting in relatively low production efficiency, making it difficult to meet the demands of consumer electronics and automotive electronics for low cost and high performance. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a wide-angle lens for LiDAR, offering a wide-angle lens category with a large field of view, short focal length, and high cost-effectiveness.

[0005] The present invention is achieved through the following technical solution: a wide-angle lens for lidar, comprising a lens barrel, wherein a first lens, a second lens, a third lens and an image plane are sequentially arranged inside the lens barrel;

[0006] The R1 surface of the first lens is convex at the optical axis, the R2 surface of the first lens is concave at the optical axis, and the edge of the R2 surface of the first lens is provided with a hole. The R1 surface of the second lens is convex at the optical axis, and the R2 surface of the second lens is concave at the optical axis. The R1 surface of the third lens is convex at the optical axis, and the R2 surface of the third lens is convex at the optical axis.

[0007] Furthermore, the first, second, and third lenses are all made of plastic.

[0008] Furthermore, the ratio of the curvature radii of the first lens R1 and R2 surfaces is 513:178, and the ratio of the aspherical diameters of the first lens R1 and R2 surfaces is 270:137.

[0009] Furthermore, the ratio of the curvature radii of the second lens's R1 and R2 surfaces is 843:3300, and the ratio of the aspherical diameters of the R1 and R2 surfaces is 1298:544.

[0010] Furthermore, the ratio of the curvature radii of the third lens's R1 and R2 surfaces is 1756:-390, and the ratio of the aspherical diameters of the R1 and R2 surfaces is 399:88.

[0011] Furthermore, the outer diameter ratio of the first lens, the second lens, and the third lens is 38:39:40, the middle thickness ratio is 2700:6649:6200, and the edge thickness ratio is 600:400:528.

[0012] Furthermore, the first lens has a refractive index of 1.544 and an Abbe number of 56.1, the second lens has a refractive index of 1.661 and an Abbe number of 20.35, and the third lens has a refractive index of 1.544 and an Abbe number of 56.1.

[0013] Furthermore, the air gap between the first and second lenses is 0.397 mm; the air gap between the second and third lenses is 0.07 mm.

[0014] Furthermore, a filter and protective glass are provided between the third lens and the image plane.

[0015] Furthermore, a first light-blocking plate is provided between the first lens and the second lens, a second light-blocking plate is provided between the second lens and the third lens, and a third light-blocking plate is provided between the third lens and the filter; the second light-blocking plate is an aperture stop.

[0016] The technical solution of the present invention has at least the following beneficial effects: External light enters the lens barrel through the first lens, which has negative optical power and a conical R1-convex-R2 surface. This surface collects and initially compresses the light. The hollow design at the edge of the R2 surface not only provides a support base for subsequent components but also prevents manufacturing difficulties caused by excessive edge thickness. After being constrained by the first light-blocking plate, the light enters the second lens, which also has negative optical power and a concave R1-convex-R2 surface. This second lens receives the light processed by the first lens and converges it to the third lens. The light then passes through the third lens, which has positive optical power and focuses the image based on the convex R1-convex-R2 surface, ultimately forming an image on the image plane. Through the "negative-negative-positive" optical power distribution and precise surface proportion design of the three all-plastic aspherical lenses, various aberrations caused by the ultra-wide field of view are effectively corrected.

[0017] In this design, the imaging lens has a very small F-number (F-Number = 2.4). A smaller F-number indicates a larger aperture, resulting in a significantly larger amount of light intake and clearer imaging. The lens also has a short effective focal length (EFL) and a large field of view (FOV), with an EFL of 0.479mm and an FOV > 146°, allowing for the capture of a wider space. The imaging lens uses a 3-element structure, which has a relatively small number of elements, and all three elements can be injection molded using plastic molds, enabling mass production. This production efficiency is higher than that of traditional glass lenses, resulting in lower costs and a higher cost-performance ratio compared to similar lenses. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a wide-angle lens embodiment of the present invention used in lidar; Figure 2 This is a schematic diagram of the optical path of a wide-angle lens embodiment of the present invention used in lidar; Figure 3 This is a schematic diagram of the first lens in an embodiment of the wide-angle lens used in lidar according to the present invention; Figure 4 This is a schematic diagram of the second lens in an embodiment of the wide-angle lens used in lidar according to the present invention; Figure 5 This is a schematic diagram of the third lens in an embodiment of the wide-angle lens used in lidar according to the present invention; Figure 6 for Figure 1 An enlarged schematic diagram of part A in the middle; Figure 7 This is a schematic diagram of the middle section of the second light-shielding plate in an embodiment of the wide-angle lens for lidar according to the present invention.

[0019] Reference numerals: 1. Lens tube; 2. First lens; 3. Second lens; 4. Third lens; 5. Image plane; 6. Hole; 7. Filter; 8. Protective glass; 9. First light shield; 10. Second light shield; 11. Third light shield; 12. Optical axis. Detailed Implementation

[0020] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0021] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] The following detailed description illustrates the specific implementation method: Example 1 As attached Figures 1-7 As shown, a wide-angle lens for lidar includes a lens barrel 1, and a first lens 2, a second lens 3, a third lens 4 and an image plane 5 are arranged sequentially inside the lens barrel 1.

[0024] In optical lens design, R1 and R2 are standard naming conventions used to distinguish the two optical surfaces of a lens. R1 refers to the surface of the lens closer to the object, the surface that light first contacts when entering the lens, also known as the object-side surface. R2 refers to the surface of the lens closer to the imaging plane 5, the surface that light passes through when exiting the lens, also known as the image-side surface. The optical axis 12 is the reference line for the entire optical system, specifically the line connecting the centers of curvature of each lens surface. For rotationally symmetric optical systems, such as in this embodiment, the optical axis 12 is the geometric central axis of the lens.

[0025] Medium thickness is the distance between the vertices of two facets of a lens element; edge thickness is the distance between the two large planes at the edge of the lens. FOV refers to the field of view of the lens, which is the range of images the lens can capture. EFL refers to the focal length of the lens.

[0026] The first lens 2 is an aspherical lens made of plastic with a refractive index nd=1.544 and an Abbe number vd=56.1. The outer diameter of the first lens 2 is D1=Φ3.8mm, the middle thickness is CT1=0.27mm, and the edge thickness is ET1=0.60mm. The radius of curvature of the R1 surface of the first lens 2 is 0.513mm, and the aspherical diameter is Φ2.7mm. The radius of curvature of the R2 surface is 0.178mm, and the aspherical diameter is Φ1.37mm. The R1 surface of the first lens 2 is convex at the optical axis 12, and the R2 surface is concave at the optical axis 12. A hole 6 is provided at the edge of the R2 surface of the first lens 2.

[0027] The second lens 3 is an aspherical lens made of plastic with a refractive index nd=1.661 and an Abbe number vd=20.35. The outer diameter of the second lens 3 is D2=Φ3.9mm, the median thickness CT2=0.6649mm, and the edge thickness ET2=0.40mm. The radius of curvature of the R1 surface of the second lens 3 is 0.843mm, and the aspherical diameter is Φ1.298mm. The radius of curvature of the R2 surface is 3.3mm, and the aspherical diameter is Φ0.544mm. Its R1 surface is convex at optical axis 12, and its R2 surface is concave at optical axis 12.

[0028] The third lens, 4, is an aspherical lens made of plastic with a refractive index nd=1.544 and an Abbe number vd=56.1. The outer diameter of the third lens, 4, is D3=Φ4.00mm, the center thickness CT3=0.62mm, and the edge thickness ET3=0.528mm. The radius of curvature of the R1 surface of the third lens, 4, is 1.756mm, and its aspherical diameter is Φ0.399mm. The radius of curvature of the R2 surface is -0.390mm, and its aspherical diameter is Φ0.88mm. Both the R1 and R2 surfaces are convex at optical axis 12.

[0029] The air gap between the first lens 2 and the second lens 3 is 0.397 mm; the air gap between the second lens 3 and the third lens 4 is 0.07 mm.

[0030] A filter 7 and a protective glass 8 are disposed between the third lens 4 and the image plane 5. The filter 7 is made of glass with a refractive index nd=1.517 and an Abbe number vd=64.2. The filter 7 has a thickness of 0.21mm. The image plane 5 is a photosensitive chip used to receive light.

[0031] A first light-shielding plate 9 is provided between the first lens 2 and the second lens 3, a second light-shielding plate 10 is provided between the second lens 3 and the third lens 4, and a third light-shielding plate 11 is provided between the third lens 4 and the filter 7; the second light-shielding plate 10 is an aperture stop. The surfaces of the first light-shielding plate 9 and the second light-shielding plate 10 undergo anti-glare treatment. This anti-glare treatment is used to confine light and control the generation of stray light. Specifically, the untreated surface of the light-shielding plate reflects light like a mirror. The anti-glare treatment, by forming a micro-roughened surface or using light-absorbing materials, converts the incident light into diffuse reflection or direct absorption, thereby preventing light from bouncing back and forth within the lens barrel 1. The third light-shielding plate 11 is located between the third lens 4 and the filter 7, suppressing stray light while providing sufficient space for the filter 7 to prevent interference.

[0032] Lens data list:

[0033] The conic coefficient and higher-order coefficients of the aspherical lens in this embodiment are:

[0034] In use, large-angle light rays (FOV>146°) from the object space enter the lens system at different field-of-view angles. Due to the extremely short focal length of the system (EFL=0.479mm), the object-side light rays exhibit a high degree of convergence upon entering the first lens element 2, reflecting the typical characteristics of a short-focal-length system. The first lens element 2 is a negative-power aspherical lens. Its R1 surface (convex surface) initially diverges the incident light rays, while its R2 surface (concave surface) compresses them. Through precise control of the aspherical surface shape, the first lens element 2 can effectively correct the distortion and astigmatism of light rays at the edge of the large field of view, providing good incident conditions for subsequent lenses. The first lens element 2 has a concave surface with a large taper. To accommodate the manufacturing of the large taper, the edge thickness of the first lens element 2 is greater (the center is concave and therefore has normal thickness). Due to the difference in thickness, uneven cooling is likely to occur during cooling, which can easily cause warping due to thermal stress, making injection molding difficult. Therefore, the design utilizes the hole 6 to thin the locally thick-walled area, making the overall wall thickness of the lens more uniform. This effectively avoids shrinkage marks, warping, and internal stress problems caused by uneven cooling during injection molding, significantly improving the surface accuracy and yield of the lens, and adapting to the manufacturing of large-tapered recesses. At the same time, the hole 6 also serves as a support structure, providing a reliable positioning reference for the subsequent stacking and assembly of the first light-shielding plate 9 and the second lens element 3, ensuring the overall assembly accuracy of the lens.

[0035] Light passing through the first lens 2 enters the area of ​​the first light-shielding plate 9. The inner diameter of the light-shielding plate is precisely matched to the beam cross-section, allowing only effective light to pass through. At the same time, its surface is treated with anti-glare to absorb stray light reflected from the lens edge and the inner wall of the lens barrel 1, preventing it from entering the subsequent optical path.

[0036] The second lens, 3, is a negative power aspherical lens that performs the main aberration correction function. Its R1 surface (convex surface) converges light rays, while its R2 surface (concave surface) further adjusts the angle of light rays, gradually bringing light rays from different fields of view toward a unified focal plane. The use of a high refractive index material (nd=1.661) helps to achieve sufficient optical power with thin lenses.

[0037] The second light-shielding plate 10 also serves as the system's aperture stop, with its inner diameter precisely controlling the light-passing aperture. The beam cross-section is smallest at this location, resulting in the most significant aperture effect. The second light-shielding plate 10 also undergoes anti-glare treatment, effectively blocking reflected light from the edge of the second lens 3 and the inner wall of the lens barrel 1, preventing the formation of ghost images or stray light.

[0038] The third lens 4 is an aspherical lens with positive power. Its R1 surface (convex surface) further refracts and adjusts the light, while its R2 surface (convex surface) precisely guides the light to the image plane 5. The third lens 4 performs the final correction of residual aberrations, ensuring that the light rays from each field of view form a clear focus on the image plane 5.

[0039] The third light-shielding plate 11, located between the third lens 4 and the filter 7, has an inner diameter slightly larger than the light-transmitting aperture. This serves to constrain the divergence angle of the light emitted from the third lens 4 and provide sufficient installation space for the filter 7, preventing mechanical interference with the third lens 4. Its surface treatment also absorbs stray light. The filter 7 employs a specific wavelength transmission design, allowing only light of the lidar's operating wavelength (such as 905nm or 1550nm) to pass through, effectively filtering out ambient light interference. The protective glass 8 provides physical protection for the photosensitive chip, preventing dust, moisture, and other contaminants from affecting image quality. The light modulated by these components ultimately converges onto the photosensitive chip on the image plane 5, forming a clear, low-distortion image. Due to the system's relatively low F-number, the image plane 5 receives sufficient illumination, which is beneficial for improving the lidar's signal-to-noise ratio and detection range.

[0040] In this example, the three aspherical lenses respectively perform the functions of divergence, convergence, and optimization. By matching the surface parameters, a balance between a large field of view and high image quality is achieved with a limited number of lenses.

[0041] In traditional wide-angle lens designs, a large field of view often leads to sharp bending of light rays at the edges, resulting in severe distortion and astigmatism, requiring the use of multiple lens elements (such as 5-7 elements) or complex aspherical lenses for correction. This invention, through the rational allocation of optical power of three aspherical lens elements and the coordinated design of the light-blocking system, minimizes the number of lens elements while maintaining a large field of view, significantly reducing system complexity and cost.

[0042] The imaging lens obtained in this embodiment has a very small F-number, F-Number = 2.4. The smaller the F-number, the larger the aperture, resulting in a particularly large amount of light intake and clear imaging. The lens has a short effective focal length (EFL) and a relatively large field of view (FOV), with an EFL of 0.479mm and an FOV > 146°, allowing for the capture of a wider space. The imaging lens adopts a 3-element structure, which has a relatively small number of elements. Furthermore, the three elements are injection molded using plastic molds, enabling mass production. This production efficiency is higher than that of traditional glass lenses, resulting in a lower cost and higher cost-effectiveness compared to similar lenses.

[0043] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A wide-angle lens for lidar, characterized in that, It includes a lens tube (1), and inside the lens tube (1) are arranged a first lens (2), a second lens (3), a third lens (4) and an image plane (5); The R1 surface of the first lens (2) is convex at the optical axis (12), and the R2 surface of the first lens (2) is concave at the optical axis (12). The edge of the R2 surface of the first lens (2) is provided with a hole (6). The R1 surface of the second lens (3) is convex at the optical axis (12), and the R2 surface of the second lens (3) is concave at the optical axis (12); The R1 surface of the third lens (4) is convex at the optical axis (12), and the R2 surface of the third lens (4) is convex at the optical axis (12).

2. The wide-angle lens for lidar according to claim 1, characterized in that, The first lens (2), the second lens (3), and the third lens (4) are all made of plastic.

3. The wide-angle lens for lidar according to claim 1, characterized in that, The ratio of the curvature radii of the first lens (2) R1 and R2 surfaces is 513:178, and the ratio of the aspherical diameters of the first lens (2) R1 and R2 surfaces is 270:

137.

4. The wide-angle lens for lidar according to claim 3, characterized in that, The second lens (3) has a radius of curvature ratio of 843:3300 for R1 and R2 surfaces and a non-spherical diameter ratio of 1298:544 for R1 and R2 surfaces.

5. The wide-angle lens for lidar according to claim 4, characterized in that, The ratio of the curvature radii of the third lens (4) to the R1 and R2 surfaces is 1756:-390, and the ratio of the aspherical diameters of the R1 and R2 surfaces is 399:

88.

6. The wide-angle lens for lidar according to claim 5, characterized in that, The outer diameter ratio of the first lens (2), the second lens (3), and the third lens (4) is 38:39:40, the middle thickness ratio is 2700:6649:6200, and the edge thickness ratio is 600:400:

528.

7. The wide-angle lens for lidar according to claim 6, characterized in that, The first lens (2) has a refractive index of 1.544 and an Abbe number of 56.

1. The second lens (3) has a refractive index of 1.661 and an Abbe number of 20.

35. The third lens (4) has a refractive index of 1.544 and an Abbe number of 56.

1.

8. The wide-angle lens for lidar according to claim 7, characterized in that, The air gap between the first lens (2) and the second lens (3) is 0.397 mm; the air gap between the second lens (3) and the third lens (4) is 0.07 mm.

9. The wide-angle lens for lidar according to claim 8, characterized in that, A filter (7) and a protective glass (8) are provided between the third lens (4) and the image plane (5).

10. The wide-angle lens for lidar according to claim 9, characterized in that, A first light-shielding plate (9) is provided between the first lens (2) and the second lens (3), a second light-shielding plate (10) is provided between the second lens (3) and the third lens (4), and a third light-shielding plate (11) is provided between the third lens (4) and the filter (7); the second light-shielding plate (10) is an aperture stop.

Images