Optical system for extending the scanning angle of MEMS micro-vibration mirror laser imaging radar

Abstract

The present invention discloses an optical system for expanding the scanning angle of a MEMS micro-vibration mirror laser imaging radar, comprising a laser receiving module and a detection module; the laser receiving module is sequentially provided with a plurality of lenses, each with positive refractive power, along a first extension direction of an optical axis, for acquiring laser signals reflected from a target object and converging them onto the photosensitive surface of the detection module. By introducing an angle-expanding optical system comprising a plurality of lenses, each with positive refractive power, sequentially provided along the first extension direction of the optical axis, the present invention overcomes the limitation of the narrow scanning range of MEMS micro-vibration mirror laser imaging radars in the prior art, thereby expanding their scanning field of view to a certain extent. Furthermore, the optical system has a simple structure, is easy to assemble, and has low production costs.

Description

Technical Field

[0001] The present application relates to the field of laser radar technology, and more specifically, to an optical system for extending the scanning angle of a MEMS micro-vibration mirror laser imaging radar. Background Art

[0002] LiDAR technology is derived from laser ranging technology. It can obtain three-dimensional target information through point-by-point, line-by-line scanning or area array detector reception. Compared with microwave radar, it has the advantages of high spatial resolution and high ranging accuracy.

[0003] Currently, the main technical approaches for imaging lidar can be divided into two categories: mechanical rotating lidar and solid-state lidar. Mechanical rotating lidar uses mechanical rotating components to achieve beam scanning. This technology was developed first and is relatively mature, but its disadvantages include difficult assembly, low scanning frequency, and high price. The main approaches for solid-state lidar include micro-electromechanical system (MEMS) hybrid solid-state lidar, area array flash lidar, and optical phased array (OPA) lidar. Flash lidar can image a target in a single exposure. The image quality ultimately depends on the performance of the area array detector, but the data volume is large and the imaging speed is slow. Although flash technology has been partially commercialized, its main drawback is that when a high-energy laser flashes to illuminate the entire target scene, only a small portion of the reflected light is received by the detector. This wastes a large amount of laser energy, resulting in a low signal-to-noise ratio of the echo signal and limited detection range. OPA scanning technology is a fully solid-state radar technology, essentially based on the optical diffraction effect. Effective optical transmittance and sidelobe effects are key technical challenges that need to be addressed for its further development. To date, international research on OPA technology has limited its maximum detection range and maturity, leaving many key technical issues unresolved. The core technology of MEMS hybrid solid-state lidar replaces traditional one-dimensional mechanical rotating components with MEMS micromirrors, achieving a high level of integration and, to a certain extent, addressing the solid-state issue. MEMS lidar, due to its lightweight, fast scanning speed, and low-cost mass production, is one of the most promising technology paths and the solution with the greatest potential for large-scale practical application. However, its main drawbacks are the small aperture size and limited scanning angle (generally below 15°) of MEMS micromirrors, requiring further improvement in performance. Furthermore, its high production process threshold, high assembly costs, and poor robustness require further reduction in its economic cost. Summary of the Invention

[0004] In response to at least one defect or improvement need in the prior art, the present invention provides an optical system for expanding the scanning angle of a MEMS micro-vibration mirror laser imaging radar, so as to expand the scanning angle of the existing MEMS micro-vibration mirror laser imaging radar and improve the overall performance of the device.

[0005] In order to achieve the above-mentioned object, the present invention provides an optical system for extending the scanning angle of a MEMS micro-vibration mirror laser imaging radar, comprising a laser receiving module and a detection module;

[0006] The laser receiving module is provided with a plurality of lenses with positive refractive powers in sequence along the first extension direction of the optical axis, for acquiring the laser signal reflected by the target object and converging it onto the photosensitive surface of the detection module.

[0007] Furthermore, the plurality of lenses are all meniscus lenses and are curved toward the image side.

[0008] Furthermore, the plurality of lenses with positive refractive powers are four lenses with positive refractive powers.

[0009] Furthermore, the laser receiving module is provided with a first lens, a second lens, a third lens and a fourth lens, all of which have positive refractive powers, in sequence along a first extension direction of the optical axis;

[0010] The thickness of the first lens is 3.13±0.50 mm; the thickness of the second lens is 4.01±0.50 mm; the thickness of the third lens is 2.98±0.50 mm; the thickness of the fourth lens is 3.50±0.50 mm;

[0011] The distance between the first lens and the second lens is 0.50±0.20 mm; the distance between the second lens and the third lens is 1.25±0.20 mm; and the distance between the third lens and the fourth lens is 0.85±0.20 mm.

[0012] Furthermore, the optical system further includes a filter for filtering to obtain laser light of a desired wavelength band;

[0013] The filter is arranged between the fourth lens and the photosensitive surface of the detection module; the distance between the fourth lens and the filter is 0.50±0.20㎜; the thickness of the filter is 1.00±0.50㎜; the distance between the filter and the photosensitive surface of the detection module is 3.20±0.20㎜; the photosensitive surface of the detection module is coplanar with the focal plane of the optical system.

[0014] Furthermore, the first lens, second lens, third lens and fourth lens, all of which have positive refractive powers, are arranged in sequence along the first extension direction of the optical axis and respectively include a first surface of the first lens with a curvature radius of 89.50 mm, a second surface of the first lens with a curvature radius of 105.32 mm, a first surface of the second lens with a curvature radius of 27.45 mm, a second surface of the second lens with a curvature radius of 541.80 mm, a first surface of the third lens with a curvature radius of 40.50 mm, a second surface of the third lens with a curvature radius of 89.70 mm, a first surface of the fourth lens with a curvature radius of 52.36 mm and a second surface of the fourth lens with a curvature radius of 55.24 mm.

[0015] Furthermore, the material models used for the first lens, the second lens, the third lens and the fourth lens are H-ZLAF80, H-LAK7, H-ZLAF80 and H-ZLAF60 respectively; none of the four lenses use aspherical lenses; and the material model used for the filter is H-K9L.

[0016] Furthermore, in the simulation experiment or actual construction of the optical system, the focal length weight is set to 0.85; the weight of the 25° field of view is set to 1.2, and the weights of the remaining fields of view are set to 1; the weights of the five primary aberrations of spherical aberration, coma, distortion, astigmatism and field curvature are set to 1, 1.1, 0.8, 0.5 and 0.6 respectively.

[0017] Furthermore, the distortion of the optical system from the 0° field of view to the 25° field of view does not exceed 0.05%, and the field curvature is less than 2.

[0018] The present invention also provides a MEMS micro-vibration mirror laser imaging radar, which includes the optical system described in any one of the above items.

[0019] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0020] (1) The present invention overcomes the limitation of the small scanning range of the MEMS micro-vibration mirror laser imaging radar in the prior art by introducing an angle-expanding optical system composed of a plurality of lenses with positive refractive powers arranged in sequence along the first extension direction of the optical axis, thereby expanding its scanning field of view to a certain extent.

[0021] (2) In order to achieve the project goal of expanding the current scanning field of view angle of less than 15° to no less than 40° (horizontal) × 30° (vertical), the present invention only uses a combination of four lenses, all of which have positive refractive power, to achieve this goal. Moreover, none of the lenses use aspherical mirrors or special optical elements. The optical system structure is relatively simple, easier to assemble, and the production cost is also low. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 A schematic diagram of the optical path and structure of an optical system for extending the scanning angle of a MEMS micro-vibration mirror laser imaging radar provided in an embodiment of the present application;

[0024] exist Figure 1 In the figure, 1 is the first lens, 2 is the second lens, 3 is the third lens, 4 is the fourth lens, and 5 is the filter;

[0025] Figure 2 This is an analysis diagram of field curvature and distortion provided in an embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0027] The terms "first," "second," or "third" in the specification, claims, or drawings of this application are used to distinguish between different objects, not to describe a specific order. In addition, the terms "including," "having," and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to the process, method, product, or apparatus.

[0028] like Figure 1 As shown in FIG, in one embodiment, an optical system for extending the scanning angle of a MEMS micro-vibration mirror laser imaging radar mainly includes a laser receiving module and a detection module. The laser receiving module extends along the first extension direction of the optical axis (i.e., the incident direction of the laser reflected from the target object). Figure 1 Several lenses with positive refractive powers are sequentially arranged (from left to right in the figure) to obtain the laser signal reflected from the target and converge it onto the photosensitive surface of the detection module (e.g., detector), thereby expanding the scanning angle of the MEMS micro-vibration mirror laser imaging radar.

[0029] Preferably, the plurality of lenses are all meniscus lenses, and are bent toward the image side (such as Figure 1 As shown, the four meniscus lenses are all bent toward the right side (i.e., the image side) to minimize spherical aberration and produce the smallest focus of the collimated incident light.

[0030] In the prior art, the scanning field of view angle of MEMS micro-vibration mirror laser imaging radar is generally less than 15°. In order to achieve the project goal of increasing the scanning field of view angle to no less than 40° (horizontal) × 30° (vertical), this embodiment only uses four lenses with positive refractive power. The laser receiving module is sequentially provided with a first lens 1, a second lens 2, a third lens 3 and a fourth lens 4 with positive refractive power along the first extension direction of the optical axis.

[0031] Preferably, the thickness of the first lens 1 is 3.13±0.50 mm; the thickness of the second lens 2 is 4.01±0.50 mm; the thickness of the third lens 3 is 2.98±0.50 mm; the thickness of the fourth lens 4 is 3.50±0.50 mm; the spacing between the first lens 1 and the second lens 2 is 0.50±0.20 mm; the spacing between the second lens 2 and the third lens 3 is 1.25±0.20 mm; and the spacing between the third lens 3 and the fourth lens 4 is 0.85±0.20 mm.

[0032] Preferably, the optical system further includes a filter 5 for filtering to obtain the laser light of the desired wavelength band. The filter 5 is provided between the fourth lens 4 and the photosensitive surface of the detection module ( Figure 1 not drawn); the distance between the fourth lens 4 and the filter 5 is 0.50±0.20㎜; the thickness of the filter 5 is 1.00±0.50㎜; the distance between the filter 5 and the photosensitive surface of the detection module is 3.20±0.20㎜; the photosensitive surface of the detection module is coplanar with the focal plane of the optical system.

[0033] Further preferred optical parameters are as follows:

[0034] Effective focal length: 13mm.

[0035] Effective caliber: 25mm.

[0036] Effective F#: 0.52.

[0037] Field of view: 40°×30°.

[0038] Since the project target field of view angle is 40°×30°, in order to meet this indicator during simulation design, the actual field of view angle is required to be While meeting imaging quality requirements, the optical system of this embodiment utilizes common glass materials and boasts a simple structure, using only four lenses and lacking aspherical mirrors or other specialized optical components. This makes assembly easy and cost-effective. The project goal is to achieve a field of view of no less than 40° (horizontally) by 30° (vertically). Further preferred optical parameters for this embodiment are shown in Table 1.

[0039]

[0040] Table 1 Optimal optical parameters of the optical system

[0041] In Table 1, the radius of curvature represents the radius of curvature of the surface included in each lens, and the pitch represents the distance between two adjacent surfaces. For example, the pitch of surface S1 represents the distance between surface S1 and surface S2, which is the thickness of first lens 1 (each lens has a certain thickness and includes two front and back surfaces). The pitch of surface S2 represents the distance between surface S2 and surface S3, which is the distance from the second surface of first lens 1 to the first surface of second lens 2, and the spacing between first lens 1 and second lens 2. And so on. In the Glass Material column, "Air" represents air, and "Infinity" represents infinity. If the front and back surfaces S9 and S10 of the filter are both infinity, it means that the filter is flat glass.

[0042] In this embodiment, the indicators that need to be controlled are the field of view, focal length and effective aperture of the optical system, and the aberrations that need to be considered are mainly five primary aberrations (spherical aberration, coma, distortion, astigmatism and field curvature). In order to improve the imaging quality, the error factor level is formulated based on professional knowledge and a large number of design experiments, and the weight parameters of each aberration and focal length and field of view are set. Through analysis and optimization, the best combination of each aberration parameter is determined. Among them, the focal length weight is set to 0.85, and the field of view weight needs to be adjusted according to the set target angle. The focus of this embodiment needs to meet the field of view angle. The optimal result is achieved when the weights of the five primary aberrations, spherical aberration, coma, distortion, astigmatism and field curvature, are set to 1, 1.1, 0.8, 0.5 and 0.6 respectively.

[0043] Based on the optimal aberration weight combination, the optical simulation software ZEMAX is used to optimize the image by using a special operator method. From the light trace distribution diagram of different fields of view of this embodiment, it can be seen that at a field of view of 25°, the detector can still receive the light spot, indicating that the field of view angle of the optical system of this embodiment meets the index requirement of 40°×30°. From the analysis diagram of field curvature and distortion of this embodiment ( Figure 2 ), it can be seen that the distortion of the optical system of this embodiment is controlled within 0.05% from the 0° field of view to the 25° field of view, and the field curvature is less than 2.

[0044] In another embodiment, a MEMS micro-vibration mirror laser imaging radar is also provided, which includes the optical system described in any of the above items. Based on this optical system with angle expansion function, the field of view angle of the MEMS micro-vibration mirror laser imaging radar scanning can be expanded to a certain extent, thereby improving the overall performance of the radar device.

[0045] The above description is merely an exemplary embodiment of the present disclosure and is not intended to limit the scope of the present disclosure. That is, any equivalent changes and modifications made in accordance with the teachings of the present disclosure are still within the scope of the present disclosure. After considering the specification and practicing the disclosure herein, those skilled in the art will easily think of other embodiments of the present disclosure. This application is intended to cover any variations, uses or adaptations of the present disclosure, which follow the general principles of the present disclosure and include common knowledge or customary technical means in the art that are not described in the present disclosure. The description and examples are to be regarded as exemplary only, and the scope and spirit of the present disclosure are defined by the claims.

[0046] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described in detail. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0047] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An optical system for extending the scanning angle of a MEMS micro-vibration mirror laser imaging radar, characterized in that: Including laser receiving module and detection module; The laser receiving module is provided with a plurality of lenses with positive refractive power in sequence along the first extension direction of the optical axis, for acquiring the laser signal reflected by the target object and converging it onto the photosensitive surface of the detection module; Wherein, the optical system further includes a filter for filtering to obtain laser light of a desired wavelength band; The filter is arranged between the fourth lens and the photosensitive surface of the detection module; the distance between the fourth lens and the filter is 0.50±0.20 mm; the thickness of the filter is 1.00±0.50 mm; the distance between the filter and the photosensitive surface of the detection module is 3.20±0.20 mm; the photosensitive surface of the detection module is coplanar with the focal plane of the optical system; Wherein, the plurality of lenses are all meniscus lenses and are curved toward the image side; Wherein, the plurality of lenses with positive refractive powers are four lenses with positive refractive powers; The laser receiving module is provided with a first lens, a second lens, a third lens and a fourth lens, all of which have positive refractive powers, in sequence along a first extension direction of the optical axis; The thickness of the first lens is 3.13±0.50 mm; the thickness of the second lens is 4.01±0.50 mm; the thickness of the third lens is 2.98±0.50 mm; the thickness of the fourth lens is 3.50±0.50 mm; The distance between the first lens and the second lens is 0.50±0.20 mm; the distance between the second lens and the third lens is 1.25±0.20 mm; the distance between the third lens and the fourth lens is 0.85±0.20 mm; The first lens, the second lens, the third lens, and the fourth lens, all of which have positive refractive powers, are sequentially arranged along the first extension direction of the optical axis and respectively include a first surface of the first lens with a curvature radius of 89.50 mm, a second surface of the first lens with a curvature radius of 105.32 mm, a first surface of the second lens with a curvature radius of 27.45 mm, a second surface of the second lens with a curvature radius of 541.80 mm, a first surface of the third lens with a curvature radius of 40.50 mm, a second surface of the third lens with a curvature radius of 89.70 mm, a first surface of the fourth lens with a curvature radius of 52.36 mm, and a second surface of the fourth lens with a curvature radius of 55.24 mm. Among them, the material models used for the first lens, the second lens, the third lens and the fourth lens are H-ZLAF80, H-LAK7, H-ZLAF80 and H-ZLAF60 respectively; none of the four lenses are aspherical lenses; the material model used for the filter is H-K9L.

2. The optical system according to claim 1, wherein In the simulation experiment or actual construction of the optical system, the focal length weight is set to 0.85; the weight of the 25° field of view is set to 1.2, and the weight of the remaining fields of view is set to 1; The weights of the five primary aberrations of spherical aberration, coma, distortion, astigmatism and field curvature are set to 1, 1.1, 0.8, 0.5 and 0.6 respectively.

3. The optical system according to claim 2, wherein: The distortion of the optical system from the 0° field of view to the 25° field of view does not exceed 0.05%, and the field curvature is less than 2.

4. A MEMS micro-vibration mirror laser imaging radar, characterized in that: The MEMS micro-vibration mirror laser imaging radar includes the optical system according to any one of claims 1 to 3.

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