Optical receiving lens and laser radar

Abstract

The present invention provides an optical receiving lens and a laser radar, and relates to optical lens technology. The optical receiving lens includes a front lens group, an aperture, and a rear lens group arranged in sequence from the object side to the image side along the optical axis; the front lens group has a negative optical focal length and includes at least two lenses; the rear lens group has a positive optical focal length and includes at least two lenses; the lenses in the front lens group include a first lens and a second lens arranged in sequence from the object side to the image side along the optical axis, the first lens being the one in the front lens group farthest from the aperture, and the first lens and the second lens are aspherical lenses. The rear lens group includes a tenth lens, which is the one in the rear lens group farthest from the aperture, and the tenth lens is an aspherical lens. The embodiment of the present invention optimizes the image height position by partitioning the light rays from the edge field of view and the light rays to the center field of view, thereby correcting distortion and reducing off-axis aberrations.

Description

Technical Field

[0001] The present invention relates to optical lens technology, and in particular to optical receiving lenses and laser radars. Background Art

[0002] On-board radar can detect the speed, distance and position of objects around the car in real time. By detecting the physical environment around the car and based on the acquired road, vehicle position and obstacle information, it can realize blind spot detection, adaptive cruise control, collision warning and other functions, and then determine whether there are other vehicles, obstacles, pedestrians, etc. around the car that pose a threat to the car's driving, thereby reducing the probability of accidents.

[0003] Currently, common automotive radars include ultrasonic radar, lidar, millimeter-wave radar, and image sensors. Compared to ultrasonic and millimeter-wave radars, lidar offers higher spatial resolution and measurement accuracy. As a result, lidar has been increasingly used in driver assistance systems in recent years and is a key radar product for future development.

[0004] The current technical forms of LiDAR include mechanical scanning radar, semi-solid scanning radar, semi-solid rotating mirror scanning radar, and fully solid-state LiDAR. Mechanical LiDARs require 360-degree rotation and scanning of both the optical transmitter and receiver under motor control. Mechanical motors are subject to mechanical wear, resulting in a short LiDAR lifespan, relatively poor stability, and limited resolution. Although semi-solid scanning radars achieve scanning through micro-electromechanical systems (MEMS), the microscopic galvanometer still involves mechanical motion, resulting in poor stability and easy damage, making MEMS devices extremely difficult to pass automotive testing. Fully solid-state LiDARs will be the mainstream form of LiDARs in the future, offering high integration and excellent stability.

[0005] The optical portion of a fully solid-state LiDAR is primarily divided into a laser transmitter module (Tx) and a laser receiver module (RX). The laser transmitter chip in the laser transmitter module typically utilizes a two-dimensional array of vertical-cavity surface-emitting lasers (VCSELs), while the laser receiver module typically utilizes a two-dimensional array of highly sensitive photosensitive devices, such as single-photon avalanche diodes (SPADs). Current LiDARs require an increasingly wider field of view, increasing from 120 degrees to 150 degrees and even 180 degrees. The optical receiver lens is essentially a device similar to a fisheye lens, which exhibits significant optical distortion. The lens's large full-port diameter and heavy weight make lightweight design and distortion control significant challenges. Summary of the Invention

[0006] An embodiment of the present invention provides an optical receiving lens and a laser radar, so as to optimize the image height position by partitioning the light from the edge field of view and the light to the center field of view, thereby correcting the distortion and reducing the off-axis aberration.

[0007] In a first aspect, an embodiment of the present invention provides an optical receiving lens, comprising a front lens group, a stop, and a rear lens group arranged in sequence from the object side to the image side along an optical axis; the front lens group has a negative optical focal length and includes at least two lenses; the rear lens group has a positive optical focal length and includes at least two lenses;

[0008] The lenses in the front lens group include a first lens and a second lens arranged in sequence from the object side to the image side along the optical axis, the first lens is the one in the front lens group farthest away from the aperture stop, and the first lens and the second lens are aspherical lenses;

[0009] The rear lens group includes a tenth lens, which is the one of the rear lens group farthest away from the aperture, and the tenth lens is an aspherical lens.

[0010] Optionally, the first lens and / or the second lens are made of plastic;

[0011] And / or, the tenth lens is made of glass.

[0012] Optionally, the first lens has negative optical power, and the second lens has negative optical power.

[0013] Optionally, the optical power of the first lens is The optical power of the second lens is satisfy:

[0014]

[0015] Optionally,

[0016] Optionally, the lenses in the front lens group further include a third lens, a fourth lens and a fifth lens arranged in sequence from the object side to the image side along the optical axis;

[0017] The third lens is a glass spherical lens with negative optical power, the fourth lens is a glass spherical lens with positive optical power, and the fifth lens is a glass spherical lens with positive optical power.

[0018] Optionally, the optical power of the third lens is The optical power of the fourth lens is The optical power of the fifth lens is satisfy:

[0019]

[0020]

[0021] Optionally, the optical power of the tenth lens is satisfy:

[0022] Optionally, the rear lens group further includes a sixth lens, a seventh lens, an eighth lens and a ninth lens arranged in sequence from the object side to the image side along the optical axis;

[0023] The aperture is located between the front lens group and the sixth lens, and the ninth lens is located between the eighth lens and the tenth lens.

[0024] Optionally, the sixth lens and the seventh lens form a doublet lens;

[0025] And / or, the eighth lens and the ninth lens form a doublet lens.

[0026] Optionally, the combined optical power of the sixth lens and the seventh lens is The combined optical power of the eighth lens and the ninth lens is satisfy:

[0027]

[0028] In a second aspect, an embodiment of the present invention provides a laser radar, comprising a transmitting module and a receiving module, wherein the receiving module comprises the optical receiving lens described in the first aspect.

[0029] In an embodiment of the present invention, the first lens and the second lens are disposed at a position away from the aperture, and the first lens and the second lens are aspherical lenses. The first lens and the second lens are away from the aperture, and light rays of different fields of view are separated, passing through different aperture regions of the first lens and the second lens. In this way, the aspherical design of the first lens and the second lens allows the first lens and the second lens to have different curvature values ​​from the center to the edge within the entire aperture range, thereby achieving differentiated optical optimization, and optimizing the image height positions of light rays of the edge field of view and light rays of the center field of view, thereby allowing the first lens and the second lens to correct the image height errors of light rays of different field of view angles and achieve distortion correction. The tenth lens is placed in the rear lens group and away from the aperture. The tenth lens is a glass aspherical lens. The tenth lens mainly plays the role of optimizing and reducing off-axis aberrations, which include astigmatism and field curvature. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic structural diagram of an optical receiving lens provided by an embodiment of the present invention;

[0031] Figure 2 A schematic structural diagram of another optical receiving lens provided by an embodiment of the present invention;

[0032] Figure 3An optical distortion curve diagram of an optical receiving lens provided by an embodiment of the present invention;

[0033] Figure 4 An optical distortion grid diagram of an optical receiving lens provided by an embodiment of the present invention;

[0034] Figure 5 A point diagram of a focal plane light spot of an optical receiving lens provided by an embodiment of the present invention;

[0035] Figure 6 This is an MTF curve diagram of an optical receiving lens provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0037] Figure 1 This is a schematic diagram of the structure of an optical receiving lens provided by an embodiment of the present invention, with reference to Figure 1 The optical receiving lens includes a front lens group G1, an aperture P, and a rear lens group G2, which are arranged in sequence from the object side to the image side along the optical axis. The aperture P is located between the front lens group G1 and the rear lens group G2. The front lens group G1 has a negative optical focal length and includes at least two lenses. The rear lens group G2 has a positive optical focal length and includes at least two lenses. The lenses in the front lens group G1 include a first lens 1 and a second lens 2, which are arranged in sequence from the object side to the image side along the optical axis. The first lens 1 is the one farthest away from the aperture P in the front lens group G1, that is, the distance between the lenses in the front lens group G1 other than the first lens 1 and the aperture P is less than the distance between the first lens 1 and the aperture P. The first lens 1 and the second lens 2 are aspherical lenses. Among them, the optical focal length is the reciprocal of the focal length, which reflects the ability of a lens or lens group to converge light.

[0038] The rear lens group G2 includes a tenth lens element 10. The tenth lens element 10 is the element in the rear lens group G2 that is farthest from the aperture P. That is, the distance between the lenses in the rear lens group G2 other than the tenth lens element 10 and the aperture P is smaller than the distance between the tenth lens element 10 and the aperture P. The tenth lens element 10 is a glass aspherical lens.

[0039] In this embodiment of the present invention, the first and second lens elements 1 and 2 are positioned away from the aperture P and are aspherical lenses. With the first and second lens elements 1 and 2 positioned away from the aperture P, light rays from different fields of view are separated and pass through different aperture regions of the first and second lens elements 1 and 2. This aspherical design allows the first and second lens elements 1 and 2 to have different curvature values ​​across the entire aperture range, from center to edge. This achieves differentiated optical optimization, optimizing the image height positions of light rays from the edge and from the center of the field of view. This allows the first and second lens elements 1 and 2 to correct image height errors for light rays from different field angles, thereby correcting distortion. The tenth lens element 10 is positioned in the rear lens group G2 and away from the aperture P. It is a glass aspherical lens and primarily functions to optimize and reduce off-axis aberrations, including astigmatism and field curvature.

[0040] Figure 2 This is a schematic diagram of the structure of another optical receiving lens provided by an embodiment of the present invention, referring to Figure 1 and Figure 2 The front lens group G1 has a negative focal length, the rear lens group G2 has a positive focal length, and the optical receiving lens is a reverse telephoto objective lens. The front lens group G1 expands the light, and then focuses it through the rear lens group G2, and the main surface of the optical receiving lens (such as Figure 2 The optical receiver lens is positioned backward (as indicated by the arrow in the middle), and the actual length of the optical receiver lens is greater than its focal length. This achieves both a wide angle and a long back focus. The wide angle allows for a wider field of view and greater information acquisition. The long back focus allows for the placement of optical and mechanical components within the BFL to meet system requirements.

[0041] Optionally, refer to Figure 1 , the lenses in the front lens group G1 also include a third lens 3, a fourth lens 4, and a fifth lens 5, which are arranged in sequence from the object side to the image side along the optical axis. Thus, the lenses in the front lens group G1 include a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, and a fifth lens 5, which are arranged in sequence from the object side to the image side along the optical axis.

[0042] Optionally, refer to Figure 1 The first lens 1 and the second lens 2 are made of plastic. This means that either the first lens 1 or the second lens 2 can be a plastic lens. Plastic lenses are also called plastic lenses or resin lenses. In the front lens group G1, the first lens 1 and the second lens 2 serve as the light entrances of the optical receiving lens, receiving wide-angle incident light signals. Since the first lens 1 and the second lens 2 have large apertures, using plastic as the material for the first lens 1 and the second lens 2 helps reduce the overall weight of the optical receiving lens.

[0043] Exemplarily, the plastic is specifically optical resin material K26R.

[0044] For example, the aperture of the first lens 1 is larger than the aperture of the second lens 2. Therefore, when the first lens 1 is made of plastic, the overall weight of the optical receiving lens can be reduced more than when the second lens 2 is made of plastic. Preferably, both the first lens 1 and the second lens 2 are made of plastic, thereby reducing the overall weight of the optical receiving lens through the material design of both the first lens 1 and the second lens 2.

[0045] Optionally, refer to Figure 1 The first lens 1 has negative optical power, the second lens 2 has negative optical power, the third lens 3 is a glass spherical lens with negative optical power, the fourth lens 4 is a glass spherical lens with positive optical power, and the fifth lens 5 is a glass spherical lens with positive optical power.

[0046] Exemplarily, the first lens 1 is a plastic aspheric lens with negative optical power, and the second lens 2 is a plastic aspheric lens with negative optical power.

[0047] Optionally, refer to Figure 1 , the optical power of the first lens 1 is The optical power of the second lens 2 is

[0048] Optionally, refer to Figure 1 ,

[0049] Optionally, refer to Figure 1 , the optical power of the first lens 1 is The optical power of the second lens 2 is The optical power of the third lens 3 is The optical power of the fourth lens 4 is The optical power of the fifth lens 5 is satisfy:

[0050] Exemplarily, the tenth lens 10 is made of low-melting-point glass D-LAK50.

[0051] Optionally, refer to Figure 1, the rear lens group G2 also includes a sixth lens 6, a seventh lens 7, an eighth lens 8, and a ninth lens 9, which are arranged in sequence along the optical axis from the object side to the image side. The aperture P is located between the fifth lens 5 and the sixth lens 6, and the ninth lens 9 is located between the eighth lens 8 and the tenth lens 10. Thus, the rear lens group G2 includes the sixth lens 6, the seventh lens 7, the eighth lens 8, the ninth lens 9, and the tenth lens 10, which are arranged in sequence along the optical axis from the object side to the image side. The optical receiving lens includes 10 lenses. The optical receiving lens includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, an aperture P, a sixth lens 6, a seventh lens 7, an eighth lens 8, a ninth lens 9, and a tenth lens 10, which are arranged in sequence along the optical axis from the object side to the image side.

[0052] Optionally, refer to Figure 1 , the sixth lens 6 and the seventh lens 7 form a double-cemented lens. The eighth lens 8 and the ninth lens 9 form a double-cemented lens. The double-cemented lens can reduce the wavelength-related aberration introduced by the bandwidth of the laser light source, that is, reduce the chromatic aberration. In the embodiment of the present invention, the sixth lens 6 and the seventh lens 7 form a double-cemented lens, and the eighth lens 8 and the ninth lens 9 form a double-cemented lens. The two double-cemented lenses can better reduce the chromatic aberration. In other embodiments, the sixth lens 6 and the seventh lens 7 can also form a double-cemented lens, while the eighth lens 8 and the ninth lens 9 do not form a double-cemented lens. Alternatively, the sixth lens 6 and the seventh lens 7 do not form a double-cemented lens, and the eighth lens 8 and the ninth lens 9 form a double-cemented lens.

[0053] Optionally, refer to Figure 1 The combined optical power of the sixth lens 6 and the seventh lens 7 is The combined optical power of the eighth lens 8 and the ninth lens 9 is The optical power of the tenth lens 10 is Satisfied: -0.05

[0054]

[0055] For example,

[0056] Exemplarily, the aperture P is located on the object focal plane, and the image-side chief ray is parallel to the optical axis, and the convergence center of the chief ray is located at infinity on the image side. Ideally, the magnification is independent of the image distance, and the measurement error introduced by inaccurate image-side focusing can be eliminated. In an embodiment of the present invention, an image-side telecentric architecture is adopted, and the aperture P is located on the object focal plane. On the image plane, the chief ray angle of the central field of view is 0 degrees, and the chief ray angle of the edge field of view is as close to 0 degrees as possible. According to actual implementation, the image-side chief ray angle (chief ray angle, CRA) can be controlled to be within 5 degrees. This can better avoid the difference in the energy of the reflected signal received by the sensor due to the difference in the angle of the central chief ray incident on the sensor in different fields of view.

[0057] Figure 3 An optical distortion curve diagram of an optical receiving lens provided by an embodiment of the present invention, Figure 4 An optical distortion grid diagram of an optical receiving lens provided by an embodiment of the present invention, referring to Figure 3 and Figure 4 After the distortion of the optical receiving lens is corrected, the optical distortion of the entire field of view is less than 5.5%.

[0058] Figure 5 A point diagram of a focal plane spot of an optical receiving lens provided by an embodiment of the present invention, with reference to Figure 5 The optical receiving lens receives the light signal at infinity (the object signal above 0.5m is regarded as infinity) and focuses it to the spot size on the light sensor. The focused spot size gradually diffuses and becomes larger from the center field of view to the edge field of view.

[0059] Specifically, the RMS radius of the light spot with a half-angle field of view of 0 degrees is 2.862 μm, the RMS radius of the light spot with a half-angle field of view of 15 degrees is 4.967 μm, the RMS radius of the light spot with a half-angle field of view of 30 degrees is 5.757 μm, the RMS radius of the light spot with a half-angle field of view of 45 degrees is 13.165 μm, the RMS radius of the light spot with a half-angle field of view of 60 degrees is 18.78 μm, and the RMS radius of the light spot with a half-angle field of view of 75 degrees is 35.798 μm.

[0060] Figure 6 The MTF curve of an optical receiving lens provided by an embodiment of the present invention is shown in FIG. Figure 6 The spatial resolution of the optical receiving lens reaches 30lp / mm, and the MTF of the optical receiving lens is greater than 0.2@spatial frequency 30lp / mm. When the spatial frequency is 17lp / mm, the MTF of the optical receiving lens performs extremely well, reaching MTF>0.6@spatial frequency 17lp / mm.

[0061] The optical receiving lens provided by the embodiment of the present invention supports lasers or other incoherent light sources in any wavelength range of 850nm to 1560nm and a bandwidth of 20nm.

[0062] The optical receiving lens provided by the embodiment of the present invention adopts an image-side telecentric design, and the image-side chief ray angle (CRA) of the marginal field of view is less than 3.8°.

[0063] Table 1 A design value of the optical receiving lens

[0064] Surface number Radius of curvature thickness Material Semi-caliber 0 infinity infinity 0.000 1 62.43～69 1.9～2.1 1.59,59.1 31.01～34.27 2 6.69～7.39 17.99～19.89 11.98～13.24 3 38.4～42.44 2.85～3.15 1.59,59.1 9.18～10.14 4 5.1～5.61 4.09～4.53 5.47～6.05 5 -26.92 7.70 1.52,62.4 5.68 6 -332 4.91 3.91 7 9.97 1.00 1.74,28.3 2.15 8 -16.51 0.10 1.97 9 4.71 0.92 1.74,28.3 1.61 10 5.07 0.48 1.19 11 infinity 1.77 0.90 12 -4.14 0.60 1.69,31.2 1.56 13 3.94 1.80 1.65,58.4 2.25 14 -5.56 0.09 2.49 15 -104.96 2.27 1.65,58.4 2.78 16 -3.22 0.46 1.74,28.3 2.91 17 -10.34 0.13 3.46 18 6.12～6.76 1.71～1.89 1.67,59.3 3.82～4.22 19 -61.34～-61.34 2.58～2.86 3.79～4.19 20 infinity 0.00 3.59

[0065] Table 1 shows a design value of the optical receiving lens, the specific value of which can be adjusted according to product requirements and is not a limitation of the embodiment of the present invention. The optical receiving lens shown in Table 1 can be Figure 1 As shown in . A lens generally includes two surfaces, each of which is a refractive surface. The surface numbers in Table 1 are numbered according to the surfaces of each lens. Among them, surface number 0 represents the object surface. Surface number 1 represents the front surface of the first lens 1 (i.e., the object side surface), surface number 2 represents the back surface of the first lens 1 (i.e., the image side surface), and so on, which are not repeated here. Surface number 20 represents the receiving surface of the optical signal receiver. The radius of curvature represents the degree of curvature of the lens surface. A positive radius of curvature value indicates that the center of curvature is on the side of the surface close to the image side, and a negative radius of curvature value indicates that the center of curvature is on the side of the surface away from the image side. The unit of the radius of curvature is mm. Infinity in the radius of curvature column indicates that the surface is flat. The value in the thickness column represents the axial distance from the current surface to the next surface. The unit of thickness is mm. The value in the half-aperture column represents half of the aperture size of the current surface. The unit of half-aperture is mm.

[0066] The design values ​​for the optical receiving lens shown in Table 1 include a focal length of 1.3 mm and an optical aperture of F / 2.4. The supported sensor target surface size is 6 mm. The diagonal field of view is 150 degrees. The wavelength range is applicable to optical signals within the 850 nm to 1560 nm band, with a bandwidth of less than 20 nm. Image telecentricity is less than 5 degrees, and distortion is less than 5.2%.

[0067] An embodiment of the present invention further provides a laser radar, comprising a transmitting module and a receiving module, wherein the receiving module includes the optical receiving lens of the aforementioned embodiment. This achieves the beneficial effects of the optical receiving lens of the aforementioned embodiment, namely, optimizing the image height positions of light rays from the edge field of view and light rays from the center field of view, thereby enabling the first lens to correct image height errors of light rays from different field of view angles, thereby achieving distortion correction.

[0068] Note that the above are only preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will appreciate that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, combinations, and substitutions are possible for those skilled in the art without departing from the scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments and may include many other equivalent embodiments without departing from the scope of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. An optical receiving lens, characterized in that: The optical system comprises a front lens group, a diaphragm, and a rear lens group arranged in sequence from the object side to the image side along the optical axis; the front lens group has a negative optical power; and the rear lens group has a positive optical power. The lenses in the front lens group are composed of a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged in sequence from the object side to the image side along the optical axis, the first lens is the one in the front lens group farthest from the aperture stop, and the first lens and the second lens are aspherical lenses; The first lens has negative optical power, the second lens has negative optical power, the third lens has negative optical power, the fourth lens has positive optical power, and the fifth lens has positive optical power; the rear lens group consists of a sixth lens, a seventh lens, an eighth lens, a ninth lens, and a tenth lens arranged in sequence from the object side to the image side along the optical axis, the tenth lens being the one in the rear lens group farthest from the aperture stop, and the tenth lens is an aspherical lens; The sixth lens has negative optical power, the seventh lens has positive optical power, the eighth lens has positive optical power, the ninth lens has negative optical power, and the tenth lens has positive optical power; The focal power of the first lens is φ1, and the focal power of the second lens is φ2, satisfying: 0.7≤φ1 / φ2≤1.0; The optical power of the fourth lens is φ4, which satisfies: 0.1≤φ4≤0.

2.

2. The optical receiving lens according to claim 1, wherein: The first lens and the second lens are made of plastic; And / or, the tenth lens is made of glass.

3. The optical receiving lens according to claim 1, wherein: -0.1≤φ1≤-0.05;-0.1≤φ2≤-0.

05.

4. The optical receiving lens according to claim 1, wherein: The third lens is a glass spherical lens, the fourth lens is a glass spherical lens, and the fifth lens is a glass spherical lens.

5. The optical receiving lens according to claim 4, characterized in that: The focal power of the third lens is φ3, and the focal power of the fifth lens is φ5, satisfying: -0.03≤φ3≤-0.01; 0.01≤φ5≤0.

1.

6. The optical receiving lens according to claim 1, wherein: The optical power of the tenth lens is φ10, which satisfies the following: 0.1≤φ10≤0.

2.

7. The optical receiving lens according to claim 1, wherein: The aperture is located between the front lens group and the sixth lens.

8. The optical receiving lens according to claim 7, wherein: The sixth lens and the seventh lens form a doublet lens; And / or, the eighth lens and the ninth lens form a doublet lens.

9. The optical receiving lens according to claim 7, wherein: The combined focal power of the sixth lens and the seventh lens is φ67, and the combined focal power of the eighth lens and the ninth lens is φ89, satisfying: -0.05≤φ67≤-0.01;0.01≤φ89≤0.

1.

10. A laser radar, characterized in that: It comprises a transmitting module and a receiving module, wherein the receiving module comprises the optical receiving lens according to any one of claims 1 to 9.

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