Laser radar receiving lens and system thereof

Abstract

A laser radar receiving lens and a system thereof relate to the technical field of optical design. The laser radar receiving lens provided by the utility model comprises an aperture diaphragm, a first lens with positive refractive power, a second lens with negative refractive power and a third lens with positive refractive power which are sequentially arranged along an optical axis from an object side to an image side, and at least one of six surfaces of the first lens, the second lens and the third lens is an aspheric surface. According to the laser radar receiving lens obtained through the design, the aperture diaphragm is arranged in front of the sides, close to the object plane, of the first lens, the second lens and the third lens, light beam control outside the laser radar receiving lens is facilitated while the compactness of the overall size of the lens is guaranteed, and then the signal-to-noise ratio and the imaging quality of a system are improved.

Description

Technical Field

[0001] The utility model relates to the technical field of optical design, and in particular, to a lidar receiving lens and its system. Background Technique

[0002] Lidar is used to measure the distance of a target object, can provide precise environmental perception and obstacle detection, and is widely used in fields such as autonomous driving and robots. The receiving energy system plays a decisive role in the optical performance of lidar. This lens system needs to have good optical imaging quality and needs to minimize the lens size as much as possible.

[0003] However, the apertures of most existing lidar receiving lenses are located inside the lens and between multiple lenses, which is not conducive to beam control and easily reduces the imaging quality. In addition, after the existing lidar receiving lens receives the signal light reflected by the target object, multiple lenses are required for beam convergence, resulting in a relatively large size of the lens assembly, which is not conducive to the miniaturization of the lens assembly. Summary of the Utility Model

[0004] The purpose of the utility model is to provide a lidar receiving lens and its system. By placing the aperture stop in front of the first lens, the second lens, and the third lens on the side close to the object plane, while reducing the overall size of the lens, it is conducive to beam control outside the lidar receiving lens, thereby improving the system signal-to-noise ratio and imaging quality.

[0005] The embodiments of the utility model are implemented as follows:

[0006] On the one hand, the utility model provides a lidar receiving lens, including an aperture stop, a first lens with a positive refractive power, a second lens with a negative refractive power, and a third lens with a positive refractive power arranged in sequence along the optical axis from the object side to the image side. Among them, at least one of the six surfaces of the first lens, the second lens, and the third lens is an aspherical surface.

[0007] Optionally, it further includes an infrared filter, and the infrared filter is arranged along the optical axis between the aperture stop and the first lens.

[0008] Optionally, the distance between the aperture stop and the side of the first lens close to the object side is greater than 20 mm.

[0009] Optionally, the first lens is a biconvex lens; the second lens is a concave-convex lens; the third lens is a concave-convex lens.

[0010] Optionally, the value range of the positive refractive power of the first lens is 0 < φ < 0.1; the value range of the negative refractive power of the second lens is -0.06 < φ < 0; the value range of the positive refractive power of the third lens is 0 < φ < 0.1.

[0011] Optionally, the ratio of the distance D along the optical axis between the surface of the first lens and the surface of the third lens to the focal length f of the lidar receiving lens satisfies: 1.5 < D / f < 2.5.

[0012] Optionally, the ratio of the semi-aperture d of the third lens near the object side to the radius of curvature r of the third lens near the object side satisfies: d / r > 0.

[0013] Optionally, the third lens includes a first body, a second body, and a third body. The second body is arranged along the optical axis, and the first body and the third body are respectively connected to both ends of the second body; the sides of the first body, the second body, and the third body away from the image plane are convex surfaces, and the sides of the first body and the second body close to the image plane are flat surfaces.

[0014] Optionally, the first lens, the second lens, and the third lens are made of glass, and the refractive index of the glass is 1.8088 and the dispersion value is 40.97.

[0015] On the other hand, the present utility model provides a lidar receiving system, which includes the above-mentioned lidar receiving lens.

[0016] The beneficial effects of the present utility model include:

[0017] The present application provides a lidar receiving lens, which sequentially arranges an aperture stop, a first lens with a positive refractive power, a second lens with a negative refractive power, and a third lens with a positive refractive power along the optical axis from the object side to the image side. Among them, at least one of the six surfaces of the first lens, the second lens, and the third lens is an aspherical surface. The lidar receiving lens obtained by the above design, by placing the aperture stop in front of the first lens, the second lens, and the third lens close to the object plane, is beneficial to beam control outside the lidar receiving lens while ensuring the compactness of the overall size of the lens, thereby improving the system signal-to-noise ratio and imaging quality. Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show some embodiments of the present utility model, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is the optical structure diagram of the lidar receiving lens provided by the present application;

[0020] Figure 2 It is the schematic diagram of the blur circle of the lidar receiving lens provided by the present application at a wavelength of 905 nm;

[0021] Figure 3 The field curvature curve graph and distortion curve graph of the lidar receiving lens provided for this application when the wavelength is from 890nm to 920nm;

[0022] Figure 4 The ray aberration curve graph of the lidar receiving lens provided for this application at a 0-degree field of view when the wavelength is from 890nm to 920nm;

[0023] Figure 5 The ray aberration curve graph of the lidar receiving lens provided for this application at an 8.75-degree field of view when the wavelength is from 890nm to 920nm;

[0024] Figure 6 The ray aberration curve graph of the lidar receiving lens provided for this application at a 12.75-degree field of view when the wavelength is from 890nm to 920nm.

[0025] Icon: 100 - Aperture stop; 110 - Infrared filter; 120 - First lens; 130 - Second lens; 140 - Third lens; 141 - First body; 142 - Second body; 143 - Third body. Detailed implementation manners

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Apparently, the described embodiments are some, but not all, of the embodiments of the present utility model. Usually, the components of the embodiments of the present utility model described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present utility model provided in the accompanying drawings is not intended to limit the scope of the present utility model to be protected, but merely represents the selected embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the scope of protection of the present utility model.

[0028] It should be noted that: Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0029] In the description of the present utility model, it should be noted that the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of this utility model is customarily placed during use. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation to the present utility model. In addition, terms such as "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0030] In addition, terms such as "horizontal" and "vertical" do not mean that the components are required to be absolutely horizontal or hanging vertically, but can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0031] In the description of the present utility model, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "installed", "connected", "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific situations.

[0032] Please refer to Figure 1 , this embodiment provides a lidar receiving lens, which includes an aperture stop 100, a first lens 120 with a positive refractive power, a second lens 130 with a negative refractive power, and a third lens 140 with a positive refractive power, which are sequentially arranged along the optical axis from the object side to the image side. Among them, at least one of the six surfaces of the first lens 120, the second lens 130, and the third lens 140 is an aspherical surface.

[0033] Specifically, for the lidar receiving lens provided in this application, an aperture stop 100, a first lens 120, a second lens 130, and a third lens 140 are sequentially arranged along the optical axis, where the aperture stop 100, the first lens 120, the second lens 130, and the third lens 140 are sequentially arranged from the object side to the image side.

[0034] Among them, the first lens 120 has a positive refractive power, the second lens 130 has a negative refractive power, and can be used to reduce aberrations, coma, and astigmatism caused by off-axis light; the third lens 140 has a positive refractive power and is used to balance the spherical aberration and distortion of the system, so that the full-field distortion is between 0 and 3%, and finally imaging is achieved.

[0035] It should be noted that, first, in the embodiments of the present application, the first lens 120 is a biconvex lens; the second lens 130 is a meniscus lens; the third lens 140 is a meniscus lens. Among them, both ends of the third lens 140 close to the image plane are flat surfaces, which facilitates the installation of the lens and the alignment of the optical path, and improves the efficiency of the assembly process of the lidar receiving lens.

[0036] Second, in the embodiments of the present application, the distance between the aperture stop 100 and the side of the first lens 120 close to the object side is greater than 20 mm. By such a setting method, it is beneficial to control the light beam outside the lidar receiving lens by the aperture stop 100, and the operability is strong, which is conducive to improving the system signal-to-noise ratio; in addition, the total system length of the lidar receiving lens refers to the distance from the center of the first lens 120 to the center of the image plane along the object plane to the image plane direction. Therefore, setting the aperture stop 100 on the side of the first lens 120 close to the object side and with a distance greater than 20 mm can reduce the total system length of the lidar receiving lens and achieve miniaturization.

[0037] Third, in the embodiments of the present application, at least one of the six surfaces of the first lens 120, the second lens 130, and the third lens 140 is an aspherical surface. The radius of curvature of the aspherical lens changes along the central axis, and has a better radius of curvature, which can maintain good aberration correction, thereby further improving the signal-to-noise ratio of the lidar receiving lens.

[0038] The present application provides a lidar receiving lens, which sequentially arranges an aperture stop 100, a first lens 120 with a positive refractive power, a second lens 130 with a negative refractive power, and a third lens 140 with a positive refractive power along the optical axis from the object side to the image side. Among them, at least one of the six surfaces of the first lens 120, the second lens 130, and the third lens 140 is an aspherical surface. The lidar receiving lens obtained by the above design, by placing the aperture stop 100 in front of the first lens 120, the second lens 130, and the third lens 140 on the side close to the object plane, while ensuring the compactness of the overall size of the lens, is beneficial to controlling the light beam outside the lidar receiving lens, thereby improving the system signal-to-noise ratio and imaging quality.

[0039] Optionally, the lidar receiving lens further includes an infrared filter 110, and the infrared filter 110 is arranged along the optical axis between the aperture stop 100 and the first lens 120.

[0040] Specifically, the lidar receiving lens provided in this application further includes an infrared filter 110, which is arranged on the optical axis between the aperture stop 100 and the first lens 120, and is coaxially arranged with the aperture stop 100 and the first lens 120. It should be noted that when the lidar receiving lens is used for a single band, a narrowband infrared filter 110 can be used. The setting of the infrared filter 110 can effectively filter out the light outside the working band, enabling the lidar receiving lens to have higher resolution in the infrared band. By arranging the infrared filter 110 between the first lens 120 and the aperture stop 100, rather than on the side of the third lens 140 close to the image plane, it is possible to avoid the increase of stray light caused by multiple reflections with the image plane and large-angle angular drift, which affect the ranging performance.

[0041] In a preferred solution of this application, in order to achieve the compactness of the lidar receiving lens while improving its light-gathering ability, the lidar receiving lens should satisfy: the positive refractive power of the first lens 120 ranges from 0 < φ < 0.1; the negative refractive power of the second lens 130 ranges from -0.06 < φ < 0; the positive refractive power of the third lens 140 ranges from 0 < φ < 0.1.

[0042] Furthermore, the ratio of the distance D along the optical axis between the surface of the first lens 120 and the surface of the third lens 140 to the focal length f of the lidar receiving lens satisfies: 1.5 < D / f < 2.5.

[0043] The ratio of the semi-aperture d of the third lens 140 near the object side to the curvature radius r of the third lens 140 near the object side satisfies: d / r > 0, thereby ensuring the light-gathering ability of the third lens 140 for light.

[0044] For the lidar receiving lens provided in this application, by setting the first lens 120, the second lens 130, and the third lens 140 according to the above relationships, the angle between the chief ray of each field of view and the image target plane can be made not greater than 20°, ensuring that the energy drop caused by the light incident angle is not greater than 20%.

[0045] Furthermore, the first lens 120, the second lens 130, and the third lens 140 are made of glass, and the refractive index of the glass is 1.8088 and the dispersion value is 40.97.

[0046] In an implementable manner of this application, the third lens 140 includes a first body 141, a second body 142, and a third body 143. The second body 142 is arranged along the optical axis, and the first body 141 and the third body 143 are respectively connected to both ends of the second body 142; the sides of the first body 141, the second body 142, and the third body 143 away from the image plane are convex surfaces, and the sides of the first body 141 and the second body 142 close to the image plane are flat surfaces.

[0047] Specifically, the third lens 140 of the present application is a concave-convex lens. The side of the third lens 140 away from the image plane is convex, and the side close to the image plane is concave. The third lens 140 includes a first body 141, a second body 142, and a third body 143. The second body 142 is arranged along the optical axis, and the first body 141 and the third body 143 are respectively connected to both ends of the second body 142. Among them, the sides of the first body 141, the second body 142, and the third body 143 away from the image plane are convex, and the sides of the first body 141 and the second body 142 close to the image plane are flat. Through such a setting method, the third lens 140 is more convenient for installation and at the same time more convenient for the adjustment of the optical path.

[0048] Preferably, at least one of the six surfaces of the first lens 120, the second lens 130, and the third lens 140 of the lidar receiving lens provided in the present application is an aspherical surface.

[0049] When at least one surface is an aspherical surface, the zernike sag formula should be satisfied:

[0050]

[0051] Among them, N is the number of Zernike coefficients in the series; α i is the surface coefficient of the even aspherical surface; A i is the coefficient of the i-th Zernike Standard polynomial; c represents the curvature of the aspherical vertex; r is the radial ray coordinate; ρ is the normalized radial ray coordinate; is the angular ray coordinate; the units of the above parameters all correspond to the unit of the lidar receiving lens.

[0052] The detailed parameters of the high-order coefficients are as follows, and the error is ±2%:

[0053]

[0054] In order to better eliminate aberration and be more convenient for processing, among the aspherical lenses of the first lens 120, the second lens 130, and the third lens 140, the side of the first lens 120 close to the object side and the side of the second lens 130 close to the image side are ellipsoidal surfaces, and the value range of the K value is -1 < k < 0; the side of the first lens 120 close to the image side, the side of the second lens 130 close to the object side, and the side of the third lens 140 close to the object side are hyperboloidal surfaces, the value range of the k value is k < -1, and the value range of the k value of the side of the third lens 140 close to the image side is k > 5.

[0055] In a specific embodiment of the present application, the lidar receiving lens has an F-number of 0.73, a field of view angle > 25°, an effective focal length < 12.4 mm, an image plane height ≤ 6 mm, and the distance between the center of the rear surface of the image plane distance L3 < 3 mm. The total length including the front aperture system is ≤ 60 mm, and the maximum outer contour of the lens Φ < 20 mm. The above lidar receiving lens has the advantages of large aperture, low aberration, and small volume, and can be used in the infrared band. In addition, the target surface lens of different sizes can be replaced, and the focal length and image plane height can be adjusted synchronously according to the ratio to meet different requirements. The resolution analysis of the lidar receiving lens in the infrared part is as follows.

[0056] As Figure 2 shown, it is a diagram of the spot diagram of the lidar receiving lens provided in this embodiment at a wavelength of 905 nm and field of view angles of 0, 3.75, 8.75, 10.63, and 12.75 degrees, and the RMS spot size < 30 μm; as Figure 3 shown, it is the field curvature curve and distortion curve of λ = 890 nm - 920 nm. Among them, the abscissa of the field curvature curve is the image-side position, the ordinate is the field of view angle of the optical system, the solid line is the meridional curve, and the dashed line is the sagittal direction curve. The abscissa of the distortion curve is the percentage change. It can be seen from the figure that the distortion increases as the field of view angle increases, and the maximum distortion is less than 3%; when imaging through the lidar receiving lens, the image quality of the off-axis part is affected, and different parts have different magnifications, resulting in a deterioration of the similarity of the object-image relationship.

[0057] As Figure 4 , Figure 5 and Figure 6 shown, it is the aberration curve diagram of the lidar receiving lens provided in this embodiment at field of view angles of 0, 8.75, and 12.75 degrees and a wavelength of 890 - 920 nm; among them, the left column Py / ey indicates the meridional image plane, Py represents the y coordinate on the aperture, and ey represents the y coordinate of the image plane; the right column Px / ex curve represents the sagittal image plane, g represents the light ray with a wavelength of λ = 890 nm, b represents the light ray with a wavelength of λ = 905 nm, and r represents the light ray with a wavelength of λ = 920 nm. The inconsistency between the curve of the meridional image plane and the curve of the sagittal image plane indicates the existence of a certain amount of astigmatism. It can be seen from the above figure that due to the reasonable distribution of the optical power and the lens structure of the lidar receiving lens provided in the present application, the lidar receiving lens can well correct various aberrations and exhibit good optical performance.

[0058] On the other hand, the present application also provides a lidar receiving system, including the above-mentioned lidar receiving lens. This lidar receiving system can be used to measure the distance of a target object, provide precise environmental perception and obstacle detection, and is widely used in fields such as autonomous driving and robotics. The excellent imaging quality of the lidar receiving lens determines the imaging quality of the lidar receiving system provided by the present application. Among them, the specific structure and beneficial effects of the lidar receiving lens have been introduced in detail above and will not be elaborated here. The lidar receiving system obtained by the above design can improve the system signal-to-noise ratio and imaging quality while miniaturizing.

[0059] The above are only optional embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0060] In addition, it should be noted that in the various specific technical features described in the above specific embodiments, they can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

Claims

1. A laser radar receiving lens, characterized in that: The lens comprises an aperture stop, a first lens with positive refractive power, a second lens with negative refractive power and a third lens with positive refractive power, which are arranged in sequence along the optical axis from the object side to the image side, wherein at least one of the six surfaces of the first lens, the second lens and the third lens is an aspherical surface; The positive refractive power of the first lens is in the range of 0<φ<0.1; the negative refractive power of the second lens is in the range of -0.06<φ<0; and the positive refractive power of the third lens is in the range of 0<φ<0.

1.

2. The laser radar receiving lens according to claim 1, characterized in that: It also includes an infrared filter, which is arranged between the aperture stop and the first lens along the optical axis.

3. The laser radar receiving lens according to claim 1, characterized in that: The distance between the aperture stop and a surface of the first lens close to the object side is greater than 20 mm.

4. The laser radar receiving lens according to claim 1, characterized in that: The first lens is a biconvex lens; the second lens is a concave-convex lens; and the third lens is a concave-convex lens.

5. The laser radar receiving lens according to claim 1, characterized in that: The ratio of the distance D between the surface of the first lens and the surface of the third lens along the optical axis to the focal length f of the laser radar receiving lens satisfies: 1.5<D / f<2.

5.

6. The laser radar receiving lens according to claim 1, characterized in that: A ratio of a semi-aperture d of the third lens close to the object side to a curvature radius r of the third lens close to the object side satisfies: d / r>0.

7. The laser radar receiving lens according to claim 4, characterized in that: The third lens includes a first body, a second body and a third body, the second body is arranged along the optical axis, and the first body and the third body are respectively connected to two ends of the second body; the first body, the second body and the third body are convex on the side away from the image plane, and the first body and the second body are flat on the side close to the image plane.

8. The laser radar receiving lens according to claim 1, characterized in that: The first lens, the second lens and the third lens are made of glass, and the refractive index of the glass is 1.8088 and the dispersion value is 40.

97.

9. A laser radar receiving system, characterized in that: It comprises the laser radar receiving lens as described in any one of claims 1-8.

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