Optical receiving lens and laser radar

Abstract

The invention provides an optical receiving lens and a laser radar, and relates to an optical lens technology. The optical receiving lens comprises a front lens group, a diaphragm and a rear lens group which are sequentially arranged from an object space to an image space along an optical axis; the front lens group has negative focal power and comprises at least two lenses; the rear lens group has positive focal power and comprises at least two lenses; the lenses in the front lens group comprise a first lens and a second lens which are sequentially arranged from the object space to the image space along the optical axis, the first lens is the one farthest away from the diaphragm in the front lens group, and the first lens and the second lens are aspheric lenses. The rear lens group comprises a tenth lens, and the tenth lens is the one farthest away from the diaphragm in the rear lens group and is an aspheric lens. According to the embodiment of the invention, the light of the edge view and the light of the center view are partitioned to optimize the image height position, so that distortion correction is realized and off-axis aberration is reduced.

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] The 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] At present, common vehicle-mounted radars mainly include ultrasonic radar, laser radar, millimeter-wave radar and image sensor. Compared with ultrasonic radar and millimeter-wave radar, laser radar has higher spatial resolution and measurement accuracy, so laser radar has been increasingly widely used in assisted driving systems in recent years and is a radar product that will be developed in the future.

[0004] The current technical forms of LiDAR include mechanical scanning radar, semi-solid scanning radar, semi-solid rotating mirror scanning radar, and all-solid-state LiDAR. Mechanical LiDAR, because both the optical transmitting and receiving ends need to rotate 360 ​​degrees under the control of a motor to scan, the mechanical motor will have mechanical wear, resulting in a short life of the LiDAR, relatively poor stability, and limited resolution. Although the semi-solid scanning radar achieves scanning through a micro-electromechanical system, the microscopic galvanometer still has mechanical movement, and the stability is poor and easy to damage. MEMS devices are very difficult to pass automotive regulations testing. All-solid-state LiDAR is the mainstream form of LiDAR in the future, with high integration and good stability.

[0005] For the optical part of all-solid-state LiDAR, it is mainly divided into laser transmitting module (Tx) and laser receiving module (RX). The laser transmitting chip of the laser transmitting module generally adopts a two-dimensional array of vertical cavity surface emitting lasers (VCSEL), and the laser receiving module generally adopts a two-dimensional array of high-sensitivity photosensitive devices, such as single photon avalanche diodes (SPAD). At present, LiDAR has increasingly higher requirements for the field of view of detection, from 120 degrees to 150 degrees, or even 180 degrees. The lens at the optical receiving end is actually a device similar to a fisheye lens. This lens device has large optical distortion, large full-port diameter of the lens, and heavy weight, so lightweight design and distortion control have become very big challenges. Summary of the invention

[0006] The embodiments of the present invention provide an optical receiving lens and a laser radar, so as to optimize the image height position by partitioning the light to the edge field of view and the light to the center field of view, thereby achieving distortion correction and reducing off-axis aberrations.

[0007] In a first aspect, an embodiment of the present invention provides an optical receiving lens, comprising a front lens group, an aperture, 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 from the aperture stop, and the first lens and the second lens are aspherical lenses;

[0009] The rear lens group includes a tenth lens, the tenth lens is the one of the rear lens group farthest from the aperture stop, 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 material of the tenth lens is 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 focal 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, including a transmitting module and a receiving module, wherein the receiving module includes the optical receiving lens described in the first aspect.

[0029] In the embodiment of the present invention, the first lens and the second lens are arranged at a position far away from the aperture, and the first lens and the second lens are aspherical lenses. The first lens and the second lens are far away from the aperture, and the light rays of different fields of view are in a separated state, passing through different aperture areas of the first lens and the second lens. In this way, the aspherical design of the first lens and the second lens can allow 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, allowing the light rays of the edge field of view and the light rays to the center field of view to optimize the image height position, so that the first lens and the second lens correct the image height error of the light rays of different field of view angles, and achieve distortion correction. The tenth lens is placed in the rear lens group, and the tenth lens is far 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, and off-axis aberrations include astigmatism and field curvature. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0031] Figure 2 A schematic diagram of the structure 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 An MTF curve diagram of an optical receiving lens provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0037] Figure 1 A schematic diagram of the structure of an optical receiving lens provided by an embodiment of the present invention, referring to Figure 1 , the optical receiving lens comprises a front lens group G1, an aperture P and a rear lens group G2 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 the front lens group G1 comprises at least two lenses. The rear lens group G2 has a positive optical focal length, and the rear lens group G2 comprises at least two lenses. The lenses in the front lens group G1 comprise a first lens 1 and a second lens 2 arranged in sequence from the object side to the image side along the optical axis, and the first lens 1 is the one farthest 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 the lens or lens group to converge light.

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

[0039] In the embodiment of the present invention, the first lens 1 and the second lens 2 are arranged at a position far away from the aperture P, and the first lens 1 and the second lens 2 are aspherical lenses. The first lens 1 and the second lens 2 are far away from the aperture P, and the light rays of different fields of view are in a separated state, passing through different aperture areas of the first lens 1 and the second lens 2. In this way, the aspherical design of the first lens 1 and the second lens 2 allows the first lens 1 and the second lens 2 to have different curvature values ​​from the center to the edge within the entire aperture range, thereby achieving differentiated optical optimization, allowing the light rays of the edge field of view and the light rays to the center field of view to optimize the image height position, so that the first lens 1 and the second lens 2 correct the image height error of the light rays of different field of view angles, thereby achieving distortion correction. The tenth lens 10 is placed in the rear lens group G2, and the tenth lens 10 is far away from the aperture P. The tenth lens 10 is a glass aspherical lens. The tenth lens 10 mainly plays the role of optimizing and reducing off-axis aberrations, and the off-axis aberrations include astigmatism and field curvature.

[0040] Figure 2 A schematic diagram of another optical receiving lens provided in 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 actual length of the optical receiving lens is greater than the focal length of the optical receiving lens. Thus, it has both wide angle and long back focus. The wide angle is to observe a larger field of view and obtain more information. The long back focus is to place optical and mechanical components within the BFL range 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 material of the first lens 1 and the second lens 2 is plastic. That is to say, the first lens 1 and the second lens 2 can be a plastic lens. Plastic lenses are also called plastic lenses and resin lenses. In the front lens group G1, the first lens 1 and the second lens 2 serve as the light inlet of the optical receiving lens, receiving wide-angle incident light signals. The apertures of the first lens 1 and the second lens 2 are large, so the material of the first lens 1 and the second lens 2 is plastic, which is conducive to reducing the overall weight of the optical receiving lens.

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

[0044] Exemplarily, the aperture of the first lens 1 is larger than the aperture of the second lens 2, so that when the material of the first lens 1 is plastic, the overall weight of the optical receiving lens can be reduced more than when the material of the second lens 2 is plastic. Preferably, the materials of the first lens 1 and the second lens 2 are both plastic, so as to reduce the overall weight of the optical receiving lens in terms of the material design of 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 focal length 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 focal length 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 arranged in sequence from the object side to the image side along the optical axis. 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 a sixth lens 6, a seventh lens 7, an eighth lens 8, a ninth lens 9 and a tenth lens 10 arranged in sequence from the object side to the image side along the optical axis. 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 arranged in sequence from the object side to the image side along the optical axis.

[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, and 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 be formed as 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 focal length 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

[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 focusing on the image side 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 when the fields of view are different.

[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 in 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 light spot of an optical receiving lens provided by an embodiment of the present invention, referring to Figure 5 The optical receiving lens receives the light signal from infinity (the object signals above 0.5m are regarded as infinity) and focuses it to the spot size on the light sensor. The focused spot size gradually diffuses and increases 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 This is an MTF curve diagram of an optical receiving lens provided in an embodiment of the present invention, referring to Figure 6 The spatial resolution of the optical receiving lens reaches 30lp / mm, and the MTF of the optical receiving lens is >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 in 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 (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, and its specific value can be adjusted according to product requirements and is not a limitation of the embodiments 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 rear surface of the first lens 1 (i.e., the image side surface), and so on, which will not be 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 represents that the center of curvature is on the side of the surface close to the image side, and a negative radius of curvature value represents 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. The infinity in the radius of curvature column represents that the surface is a plane. 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 semi-aperture column represents half of the aperture size of the current surface. The unit of semi-aperture is mm.

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

[0067] The embodiment of the present invention further provides a laser radar, which includes a transmitting module and a receiving module, and the receiving module includes the optical receiving lens in the above embodiment. Thus, the laser radar has the beneficial effect of the optical receiving lens in the above embodiment, that is, the image height position is optimized by partitioning the light of the edge field of view and the light of the center field of view, so that the first lens corrects the image height error of the light of different field of view angles, and realizes the correction of distortion.

[0068] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, combinations and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and 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 invention comprises a front lens group, a stop and a rear lens group which are sequentially arranged from the object side to the image side along the optical axis; the front lens group has a negative optical focal length and comprises at least two lenses; the rear lens group has a positive optical focal length and comprises 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 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 rear lens group includes a tenth lens, the tenth lens is the one of the rear lens group farthest from the aperture stop, and the tenth lens is an aspherical lens.

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

3. The optical receiving lens according to claim 1, characterized in that: The first lens has negative refractive power, and the second lens has negative refractive power.

4. The optical receiving lens according to claim 3, characterized in that: 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.

5. The optical receiving lens according to claim 4, characterized in that: -0.1≤φ1≤-0.05; -0.1≤φ2≤-0.

05.

6. The optical receiving lens according to claim 1, characterized in that: The lenses in the front lens group also 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; 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.

7. The optical receiving lens according to claim 6, characterized in that: The focal power of the third lens is φ3, the focal power of the fourth lens is φ4, and the focal power of the fifth lens is φ5, which satisfies: -0.03≤φ3≤-0.01; 0.1≤φ4≤0.2; 0.01≤φ5≤0.

1.

8. The optical receiving lens according to claim 1, characterized in that: The optical power of the tenth lens is φ10, satisfying: 0.1≤φ10≤0.

2.

9. The optical receiving lens according to claim 1, characterized in that: 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; 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.

10. The optical receiving lens according to claim 9, characterized in that: The sixth lens and the seventh lens form a doublet lens; And / or, the eighth lens and the ninth lens form a doublet lens.

11. The optical receiving lens according to claim 9, characterized in that: 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, which satisfies: -0.05≤φ67≤-0.01; 0.01≤φ89≤0.

1.

12. 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 11.

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