Low-distortion angle-expanding lens applied to MEMS laser radar
By designing a low-distortion angle expanding lens for MEMS lidar, using the combination of aspherical and spherical lenses, the problem of small scanning range and large distortion of MEMS lidar is solved, achieving a larger scanning angle and higher detection accuracy.
Patent Information
- Application Number
- CN202422222287.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-11
- Publication Date
- 2025-06-20
- Estimated Expiration
- 2034-09-11
AI Technical Summary
The scanning range of existing MEMS lidars is small, resulting in large distortions and unable to effectively increase the scanning angle.
A low-distortion angle expansion lens is designed, including a series of aspherical and spherical lenses, which expand the scanning angle of emitted and received light through a combination of lenses of positive and negative power, and is reversibly applied to the receiving system through the optical path.
The scanning angle of MEMS lidar is increased, which reduces distortion and improves the quality and detection accuracy of point cloud maps.
Smart Images
Figure CN223006344U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of lidar lenses, and particularly relates to a low-distortion wide-angle lens applied to MEMS lidar. Background Art
[0002] Lidar mainly includes pulsed lidar, phase lidar, and triangulation lidar. The pulsed lidar includes a laser transmitting and receiving module, which is mainly used for laser ranging in medium and long distances. The process of pulsed laser ranging is as follows: the laser emitted by the rangefinder is reflected by the measured object and then received by the rangefinder. The rangefinder simultaneously records the round-trip time of the laser. Half of the product of the speed of light and the round-trip time is the distance between the rangefinder and the measured object. Then this distance information is transmitted to an electronic chip for processing. The electronic software controls the radar to perform the next operation according to the received signal.
[0003] MEMS (Micro-Electro-Mechanical Systems) galvanometer lidar (LiDAR) is a lidar system implemented using micro-electro-mechanical system technology. Its main feature is the use of MEMS technology to construct a miniaturized movable mirror for rapid scanning of laser beams. Due to product size limitations of lidar based on MEMS galvanometers, the rotation range of the MEMS galvanometer is small, resulting in a small scanning range. Currently, similar lidar products on the market have problems such as small scanning and receiving angles and large distortion.
[0004] Therefore, how to provide a low-distortion wide-angle lens that can effectively increase the scanning angle of MEMS lidar is a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Utility Model
[0005] In view of the above research status and existing problems, the utility model provides a low-distortion wide-angle lens applied to MEMS lidar, which increases the scanning angle of the emitted light. According to the reversibility of the optical path, when applied to the receiving system, the corresponding receiving field of view is also increased accordingly. At the same time, the spot quality is improved and the distortion is reduced, resulting in an improved point cloud map quality.
[0006] A low-distortion wide-angle lens applied to MEMS lidar provided by the utility model, the lens system includes: a first lens, a second lens, and a third lens arranged in sequence along the optical axis from the transmitter / receiver end of the MEMS lidar to the measured object; wherein,
[0007] The first lens is an aspherical lens with positive optical power, and receives the collimated laser beam within the scanning range of the MEMS lidar;
[0008] The second lens is an aspherical lens with a negative optical power, covering the laser beam within the range of the outgoing light received by the first lens;
[0009] The third lens is a spherical lens with a negative optical power, covering the laser beam within the range of the outgoing light received by the second lens.
[0010] The collimated light emitted by the radar transmitter of the present utility model changes its angle through a galvanometer mirror, and then passes through the first lens, the second lens, and the third lens in sequence to emit light at different angles, realizing the function of large-angle scanning; this lens can also be used for a radar receiver. When used for a radar receiver, the light reflected by an object passes through the third lens, the second lens, and the first lens and enters the receiver. The laser radar wide-angle lens provided by the present utility model can expand the measurement range of the radar, realize the detection function in a large laser field of view range, reduce the distortion of the point cloud map, and increase the detection accuracy and efficiency.
[0011] Preferably, the third lens is a glass spherical lens. The glass spherical lens is at the outermost end of the lens system. The glass has stronger anti-wear ability than plastic, and the glass has the characteristic of high hardness, and can be used as a window piece to increase the anti-wear ability of the product.
[0012] Preferably, the first lens and the second lens are plastic aspherical lenses.
[0013] Preferably, the d-light refractive index of the first lens and the second lens is nd1, and the Abbe number is v1, satisfying the following condition: 34 < v1 / nd1 < 38. Being within the range of the relational expression is beneficial to realizing the expansion of the infrared light angle, achieving the wide-angle effect, and having a large Abbe number and good dispersion.
[0014] Preferably, the d-light refractive index of the third lens is nd2, and the Abbe number is v2, satisfying the following condition: 40 < v2 / nd2 < 43.
[0015] Preferably, the total focal length F and the entrance pupil diameter D of the lens system satisfy the following condition: 0 < (D / F) 2 < 0.1. Being within the range of the relational expression, the lens has a sufficiently large aperture number, and the more light enters. When used for a transmitter, as much light as possible can be emitted. When used for a receiver, more light in a larger range can be received into the system as much as possible, improving the receiving efficiency. It can ensure the collection of light energy by the detector within different measurement ranges under the condition that the optical system remains unchanged.
[0016] Preferably, the radius of curvature R1 of the side surface of the first lens of the MEMS lidar and the radius of curvature R2 of the side surface of the object to be measured satisfy the following conditions: 0.9 ≤ (R1 + R2) / (R1 - R2) ≤ 1.1. Within the range of the relational expression, while ensuring the optical power of the lens, it is possible to effectively collect light energy and correct aberration; the effective focal length f1 of the first lens, the on-axis thickness d1, the total focal length F of the lens system, and the total optical length L satisfy the following conditions: 0 < |f1 / F| ≤ 0.4, 0 < d1 / L ≤ 0.4; the range of the relational expression between the effective focal length f1 and the total focal length F is conducive to appropriately converging parallel light beams while ensuring the optical power of the lens, which is beneficial for aberration correction and subsequent expansion of the light emission angle; the range of the relational expression between the on-axis thickness d1 and the total optical length L is conducive to shortening the system length and reducing the mechanical assembly difficulty.
[0017] Preferably, the radius of curvature R3 of the side surface of the second lens of the MEMS lidar and the radius of curvature R4 of the side surface of the object to be measured satisfy the following conditions: -2 ≤ (R3 + R4) / (R3 - R4) ≤ -0.5. Within the range of the relational expression, while ensuring the optical power of the lens, it is possible to effectively collect light energy and correct aberration; the effective focal length f2 of the second lens, the on-axis thickness d2, the total focal length F of the lens system, and the total optical length L satisfy the following conditions: 0 < f2 / F ≤ 0.4, 0 < d2 / L ≤ 0.4; the range of the relational expression between the effective focal length f2 and the total focal length F is conducive to expanding the deflection angle of the light while ensuring the optical power of the lens, realizing the angle expansion function of the lens group; the range of the relational expression between the on-axis thickness d2 and the total optical length L is conducive to shortening the system length and reducing the mechanical assembly difficulty.
[0018] Preferably, the radius of curvature R5 of the side surface of the third lens of the MEMS lidar and the radius of curvature R6 of the side surface of the object to be measured satisfy the following conditions: -2 ≤ (R5 + R6) / (R5 - R6) ≤ -0.5. Within the range of the relational expression, while ensuring the optical power of the lens, it is possible to effectively collect light energy; the effective focal length f3 of the third lens, the on-axis thickness d3, the total focal length F of the lens system, and the total optical length L satisfy the following conditions: 0.1 < f3 / F ≤ 0.5; 0 < d3 / L ≤ 0.4. The range of the relational expression between the effective focal length f3 and the total focal length F is conducive to further deflecting the light while ensuring the optical power of the lens, which is beneficial for subsequent expansion of the emission angle of the light and collection of light received in a large range; the range of the relational expression between the on-axis thickness d3 and the total optical length L is conducive to shortening the system length and reducing the mechanical assembly difficulty.
[0019] Preferably, the total optical length L of the lens system is less than or equal to 48 mm.
[0020] The low-distortion wide-angle lens applied to the MEMS lidar proposed by the present utility model has the following beneficial effects compared with the prior art:
[0021] The present utility model corrects aberration with an aspherical lens of positive optical power, and uses an aspherical lens of negative optical power and a spherical lens of negative optical power to expand the exit angle and collimate the light again, achieving the function of expanding the emission scanning angle and the receiving angle. According to the reversibility of the optical path, this method is applied to the receiving system, and the corresponding receiving field of view is also increased accordingly. At the same time, the spot quality is improved and the distortion is reduced, so as to obtain a point cloud map with better imaging quality, which is convenient for radar detection and data analysis. Description of the Drawings
[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.
[0023] Figure 1 It is a schematic diagram of the principle of a MEMS lidar provided by an embodiment of the present utility model;
[0024] Figure 2 It is a schematic diagram of an optical system of a low-distortion wide-angle lens applied to a MEMS lidar provided by an embodiment of the present utility model;
[0025] Figure 3 It is a schematic diagram of the structure of a low-distortion wide-angle lens applied to a MEMS lidar provided by an embodiment of the present utility model;
[0026] Figure 4 It is a distortion diagram of the lens system provided by an embodiment of the present utility model;
[0027] Figure 5 It is a spot diagram of the lens system provided by an embodiment of the present utility model. Detailed Embodiments
[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present utility model with reference to the drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present utility model.
[0029] As Figure 1 shown, first, the working principle of the MEMS lidar will be described:
[0030] The transmitting module A1 is used to emit a collimated detection beam, and the receiving module A2 is used to receive the laser reflected by the object to be measured.
[0031] The emission module A1 includes a laser emitting diode and an emission lens. The laser emitting diode can be single or multiple; the emission lens can be a single lens or multiple lenses, without special requirements. The emission module is required to emit a collimated light beam.
[0032] The receiving module A2 receives the parallel laser deflected by the galvanometer. The receiver can be one or more of avalanche photodiodes APDs and silicon photomultipliers SiPMs, and the number of lenses in the receiving system is not limited either.
[0033] A low-distortion wide-angle lens applied to a MEMS lidar provided by an embodiment of the present utility model. The collimated light emitted by the emission module A1 is deflected by the angle of the galvanometer, and successively passes through the first lens 1, the second lens 2, and the third lens 3 to expand the laser emission angle, and hits an object 4 in the detection area. The laser reflected by the object 4 in the detection area successively passes through the third lens 3, the second lens 2, and the first lens 1, is deflected by the galvanometer 0, and is received by the receiving module A2.
[0034] As Figure 2 shown, the lens system of the embodiment of the present utility model includes: a first lens 1, a second lens 2, and a third lens 3 arranged in sequence along the optical axis from the transmitter / receiver end of the MEMS lidar 10 to the object to be measured 4; wherein, the first lens 1 is an aspherical lens with a positive optical power, and receives the collimated light laser beam within the scanning range of the MEMS lidar 10; the second lens 2 is an aspherical lens with a negative optical power, and covers and receives the laser beam within the outgoing light range of the first lens 1; the third lens 3 is a spherical lens with a negative optical power, and covers and receives the laser beam within the outgoing light range of the second lens 2.
[0035] As Figure 3 shown, the first lens 1, the second lens 2, and the third lens 3 are fixedly connected as a whole lens system through a fixing bracket according to the positional relationship set along the optical axis. The fixing bracket can be a ring-shaped cylindrical structure, and three annular slots are respectively arranged at corresponding depth positions of the cylinder for fixedly installing the first lens 1, the second lens 2, and the third lens 3.
[0036] In one embodiment, the third lens 3 is a glass spherical lens, which has high hardness to prevent scratching and low cost. The whole lens system is installed outside the laser window of the MEMS lidar, and the third lens 3 is at the outermost end, increasing the anti-wear ability of the product.
[0037] In this embodiment, the first lens 1 and the second lens 2 are plastic aspherical lenses.
[0038] In one embodiment, the d-line refractive index of the first lens 1 and the second lens 2 is nd1, and the Abbe number is v1, satisfying the following conditions: 34 < v1 / nd1 < 38. Further, the following conditions are satisfied: 35 < v1 / nd1 < 36.
[0039] In one embodiment, the d-line refractive index of the third lens 3 is nd2, and the Abbe number is v2, satisfying the following conditions: 40 < v2 / nd2 < 43. Further, the following conditions are satisfied: 41 < v4 / nd4 < 42.
[0040] In one embodiment, as Figure 2 shown, the total focal length F and the entrance pupil diameter D of the lens system satisfy the following conditions: 0 < (D / F) 2 < 0.1.
[0041] In one embodiment, as Figure 3 shown, the side curvature radius R1 of the MEMS lidar 10 of the first lens 1 and the side curvature radius R2 of the object 4 to be measured satisfy the following conditions: 0.9 ≤ (R1 + R2) / (R1 - R2) ≤ 1.1; the effective focal length f1, the on-axis thickness d1 of the first lens 1 and the total focal length F, the optical total length L of the lens system satisfy the following conditions: 0 < |f1 / F| ≤ 0.4, 0 < d1 / L ≤ 0.4.
[0042] Further, the side curvature radius R1 of the MEMS lidar 10 of the first lens 1 and the side curvature radius R2 of the object 4 to be measured satisfy the following conditions: 1.0 ≤ (R1 + R2) / (R1 - R2) ≤ 1.05.
[0043] Further, the effective focal length f1, the on-axis thickness d1 of the first lens 1 and the total focal length F, the optical total length L of the lens system satisfy the following conditions: 0 < |f1 / F| ≤ 0.2, 0 < d1 / L ≤ 0.2.
[0044] Further, the effective focal length f1, the on-axis thickness d1 of the first lens 1 and the total focal length F, the optical total length L of the lens system satisfy the following conditions: 0 < |f1 / F| ≤ 0.15, 0.05 < d1 / L ≤ 0.15.
[0045] In one embodiment, as Figure 3 shown, the side curvature radius R3 of the MEMS lidar 10 of the second lens 2 and the side curvature radius R4 of the object 4 to be measured satisfy the following conditions: -2 ≤ (R3 + R4) / (R3 - R4) ≤ -0.5; the effective focal length f2, the on-axis thickness d2 of the second lens 2 and the total focal length F, the optical total length L of the lens system satisfy the following conditions: 0 < f2 / F ≤ 0.4, 0 < d2 / L ≤ 0.4.
[0046] Furthermore, the curvature radius R3 of the side surface of the second lens 2 and the curvature radius R4 of the side surface of the object 4 to be measured of the MEMS lidar 10 satisfy the following condition: -1.5 ≤ (R3 + R4) / (R3 - R4) ≤ -1.
[0047] Furthermore, the effective focal length f2 of the second lens 2, the on-axis thickness d2, the total focal length F of the lens system, and the total optical length L satisfy the following conditions: 0 < f2 / F ≤ 0.2, 0 < d2 / L ≤ 0.2.
[0048] Furthermore, the effective focal length f2 of the second lens 2, the on-axis thickness d2, the total focal length F of the lens system, and the total optical length L satisfy the following conditions: 0 < f2 / F ≤ 0.2, 0.05 < d2 / L ≤ 0.15.
[0049] In one embodiment, as Figure 3 shown, the curvature radius R5 of the side surface of the third lens 3 and the curvature radius R6 of the side surface of the object 4 to be measured of the MEMS lidar 10 satisfy the following condition: -2 ≤ (R5 + R6) / (R5 - R6) ≤ -0.5; the effective focal length f3 of the third lens 3, the on-axis thickness d3, the total focal length F of the lens system, and the total optical length L satisfy the following conditions: 0.1 < f3 / F ≤ 0.5; 0 < d3 / L ≤ 0.4.
[0050] Furthermore, the curvature radius R5 of the side surface of the third lens 3 and the curvature radius R6 of the side surface of the object 4 to be measured of the MEMS lidar 10 satisfy the following condition: -1.5 ≤ (R5 + R6) / (R5 - R6) ≤ -1.
[0051] Furthermore, the effective focal length f3 of the third lens 3, the on-axis thickness d3, the total focal length F of the lens system, and the total optical length L satisfy the following conditions: 0.1 < f3 / F ≤ 0.3, 0.1 < d3 / L ≤ 0.3.
[0052] Furthermore, the effective focal length f3 of the third lens 3, the on-axis thickness d3, the total focal length F of the lens system, and the total optical length L satisfy the following conditions: 0.1 < f3 / F ≤ 0.3, 0 < d3 / L ≤ 0.2.
[0053] In one embodiment, the total optical length L of the lens system is less than or equal to 48 mm.
[0054] As Figure 4 shown, the distortion of the entire field of view of the lens system provided by the present utility model is < 2%, which can increase the accuracy and efficiency of radar detection. The lens system can not only be used in the transmitting system to expand the scanning angle, but also be applied to the receiving system to expand the receiving field of view.
[0055] The above has introduced in detail a low-distortion wide-angle lens applied to a MEMS lidar provided by the present utility model. Specific examples are used in this article to elaborate on the principle and implementation manner of the present utility model. The description of the above embodiments is only used to help understand the method and its core idea of the present utility model; at the same time, for those of ordinary skill in the art, according to the idea of the present utility model, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present utility model.
[0056] In this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or device including the said element.
Claims
1. A low distortion expanded angle lens for MEMS laser radar, characterized in that: The lens system includes: a first lens, a second lens and a third lens arranged in sequence along the optical axis from the transmitter / receiver end of the MEMS laser radar to the object to be measured; wherein, The first lens is an aspheric lens with positive optical power, receiving the collimated laser beam within the scanning range of the MEMS laser radar; The second lens is an aspheric lens with negative optical power, and covers and receives the laser beam within the range of the output light of the first lens; The third lens is a spherical lens with negative optical power, and covers and receives the laser beam within the range of the output light of the second lens.
2. The low distortion expanded angle lens for MEMS laser radar according to claim 1, characterized in that: The third lens is a glass spherical lens.
3. The low distortion expanded angle lens for MEMS laser radar according to claim 2, characterized in that: The first lens and the second lens are plastic aspherical lenses.
4. The low distortion expanded angle lens for MEMS laser radar according to claim 1, characterized in that: The d-light refractive index of the first lens and the second lens is nd1, and the Abbe number is v1, which satisfies the following conditions: <v1 / nd1<38。 5. The low distortion expanded angle lens for MEMS laser radar according to claim 1, characterized in that: The third lens has a d-light refractive index of nd2 and an Abbe number of v2, satisfying the following conditions: <v2 / nd2<43。 6. The low distortion expanded angle lens for MEMS laser radar according to claim 1, characterized in that: The total focal length F and entrance pupil diameter D of the lens system satisfy the following conditions: 0<(D / F) 2 <0.
1.
7. The low distortion expanded angle lens for MEMS laser radar according to claim 1, characterized in that: The MEMS laser radar side curvature radius R1 of the first lens and the measured object side curvature radius R2 satisfy the following conditions: 0.9≤(R1+R2) / (R1-R2)≤1.1; the effective focal length f1, the axial thickness d1 of the first lens and the total focal length F and the total optical length L of the lens system satisfy the following conditions: 0<|f1 / F|≤0.4, 0<d1 / L≤0.
4.
8. The low distortion expanded angle lens for MEMS laser radar according to claim 1, characterized in that: The MEMS laser radar side curvature radius R3 of the second lens and the measured object side curvature radius R4 satisfy the following conditions: -2≤(R3+R4) / (R3-R4)≤-0.5; the effective focal length f2, axial thickness d2 of the second lens and the total focal length F and total optical length L of the lens system satisfy the following conditions: 0<f2 / F≤0.4, 0<d2 / L≤0.
4.
9. The low distortion angle-expanding lens for MEMS laser radar according to claim 1, characterized in that: The MEMS laser radar side curvature radius R5 of the third lens and the measured object side curvature radius R6 satisfy the following conditions: -2≤(R5+R6) / (R5-R6)≤-0.5; the effective focal length f3, the axial thickness d3 of the third lens and the total focal length F and the total optical length L of the lens system satisfy the following conditions: 0.1<f3 / F≤0.5; 0<d3 / L≤0.
4.
10. The low distortion expanded angle lens for MEMS laser radar according to claim 1, characterized in that: The total optical length L of the lens system is less than or equal to 48 mm.