Angle-expanding lens applied to MEMS galvanometer

Abstract

The invention discloses an angle-expanding lens applied to an MEMS galvanometer. The angle-expanding lens comprises a first lens, a second lens, the MEMS galvanometer, a third lens and a fourth lens which are sequentially arranged along an optical axis from an object side to an image side, wherein the first lens is a meniscus lens with negative focal power; the second lens is a biconvex lens with positive focal power; the MEMS galvanometer is essentially a circular plane reflecting mirror; the third lens is a meniscus lens with negative focal power; and the fourth lens is a biconcave or plano-concave lens with negative focal power. According to the invention, the scanning field angle of the MEMS laser radar is expanded through the lens design.

Description

Technical Field

[0001] The present invention belongs to the technical field of lenses, and in particular relates to an angle-expanding lens applied to a MEMS galvanometer. Background Art

[0002] LiDAR is widely used in security, intelligent driving, medical treatment, scientific research and other fields. In recent years, with the improvement of LiDAR performance and the decrease of price, its application areas have become more and more extensive, and higher requirements have been placed on the design of LiDAR.

[0003] MEMS LiDAR is a scanning LiDAR based on micro-electromechanical systems (MEMS) technology. Its core principle is to use a MEMS galvanometer to control the scanning direction of the laser beam. By emitting laser light and receiving the light reflected from the target, the time or frequency difference of the laser's round trip is calculated, thereby accurately measuring the target's distance.

[0004] MEMS lenses are typically driven by electrostatic or electromagnetic forces, oscillating horizontally and / or vertically to achieve two-dimensional laser scanning. Due to the small size, fast response, and high integration of MEMS devices, this type of radar offers the advantages of miniaturization, low power consumption, and high-speed scanning. Currently, MEMS lidars typically have a very small scanning field of view due to the limitations of the mechanical scanning angle of the MEMS galvanometer. Summary of the Invention

[0005] The purpose of the present invention is to provide an angle expansion lens applied to a MEMS galvanometer.

[0006] The technical solution for achieving the purpose of the present invention is as follows: an angle expansion lens applied to a MEMS galvanometer mirror, comprising a first lens, a second lens, a MEMS galvanometer mirror, a third lens, and a fourth lens in sequence from the object side to the image side along the optical axis;

[0007] in,

[0008] The first lens is a meniscus lens with negative optical power;

[0009] The second lens is a biconvex lens with positive optical power;

[0010] The MEMS galvanometer is a circular plane reflective mirror;

[0011] The third lens is a meniscus lens with negative optical power;

[0012] The fourth lens is a biconcave or plano-concave lens with negative optical power.

[0013] Preferably, the air thickness between the first lens and the second lens ranges from 0.49 to 0.51 mm; the air thickness between the second lens and the MEMS galvanometer ranges from 9.1 to 10.8 mm; the air thickness between the MEMS galvanometer and the third lens ranges from 13.1 to 14.8 mm; and the air thickness between the third lens and the fourth lens ranges from 17.7 to 21.7 mm.

[0014] Preferably, the material of the first lens includes heavy lanthanum flint glass, the object side surface of the first lens is convex, and the curvature radius of the object side surface of the first lens ranges from 6.035 to 6.063 mm; the image side surface of the first lens is concave, and the curvature radius of the image side surface of the first lens ranges from 5.164 to 5.181 mm.

[0015] Preferably, the material of the second lens is heavy lanthanum flint glass, the object side surface of the second lens is convex, and the curvature radius of the object side surface of the second lens ranges from 18.838 to 19.076 mm; the image side surface of the second lens is convex, and the curvature radius of the image side surface of the second lens ranges from -7.074 to -7.051 mm.

[0016] Preferably, the MEMS oscillating mirror is a circular plane reflective mirror, the radius of the MEMS oscillating mirror is greater than 4.7 mm, and the mechanical vibration angle range of the MEMS oscillating mirror is -7.5 to 7.5 degrees.

[0017] Preferably, the material of the third lens includes heavy lanthanum flint glass, the object side surface of the third lens is concave, and the radius of the curvature of the object side surface of the third lens ranges from 12.857 to 13.072 mm; the image side surface of the third lens is convex, and the radius of the curvature of the image side surface of the third lens ranges from 15.907 to 16.196 mm.

[0018] Preferably, the material of the fourth lens comprises heavy lanthanum flint glass, the object side surface of the fourth lens is concave, and the curvature radius of the object side surface of the fourth lens ranges from 36.532 to 40.196 mm; the image side surface of the fourth lens is concave or flat, and the curvature radius of the image side surface of the second lens ranges from -∞ to

[0019] -900mm.

[0020] Compared with the prior art, the present invention has the following significant advantages:

[0021] The present invention achieves 60° field of view scanning using only four lenses, and the scanning angle is linearly related to the MEMS deflection angle. It still maintains good optical properties under -40°C and +85°C conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solution of the present invention, the following is a brief description of the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without inventive work.

[0023] Figure 1 The figure is a schematic structural diagram of an angle expansion lens applied to a MEMS galvanometer provided by an embodiment of the present invention.

[0024] Figure 2 Schematic diagram of the beam divergence angle of an angle expansion lens applied to a MEMS galvanometer provided by an embodiment of the present invention at a field of view angle of 0°.

[0025] Figure 3 Schematic diagram of the beam divergence angle of an angle-expanding lens applied to a MEMS galvanometer provided by an embodiment of the present invention at a field of view of 30°.

[0026] Figure 4 This is a diagram showing the relationship between the MEMS galvanometer angle and the scanning field of view of an angle expansion lens applied to a MEMS galvanometer provided by an embodiment of the present invention.

[0027] Figure 5 This is a relationship diagram between the MEMS galvanometer angle and the scanning field of view at different temperatures provided by an angle expansion lens applied to a MEMS galvanometer according to an embodiment of the present invention.

[0028] Figure 6 This is a schematic diagram of the light beam divergence angle corresponding to different MEMS galvanometer angles at different temperatures provided by an angle expansion lens applied to a MEMS galvanometer according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The step numbers in the following embodiments are provided for ease of description only and do not limit the order of the steps. The order of execution of the steps in the embodiments can be adaptively adjusted based on the understanding of those skilled in the art.

[0030] In the following description, reference is made to “some embodiments”, which describes a subset of all possible embodiments, but it will be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0031] In the following description, the terms "first\second\third" are merely used to distinguish similar objects and do not represent a specific ordering of the objects. It is understandable that "first\second\third" can be interchanged with a specific order or sequence where permitted, so that the embodiments of the present invention described herein can be implemented in an order other than that illustrated or described herein.

[0032] Unless otherwise defined, all technical and scientific terms used in the embodiments of the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention pertains. The terms used in the embodiments of the present invention are for the purpose of describing the embodiments of the present invention only and are not intended to limit the present invention.

[0033] Before further explaining the embodiments of the present invention in detail, the nouns and terms involved in the embodiments of the present invention are explained. The nouns and terms involved in the embodiments of the present invention are subject to the following interpretations.

[0034] like Figure 1 As shown, the present invention proposes an angle-expanding lens for a MEMS galvanometer, which includes a first lens L1, a second lens L2, a MEMS galvanometer M1, a third lens L3, and a fourth lens L4 in sequence from the object side to the image side along the optical axis; wherein,

[0035] The first lens L1 is a meniscus lens with negative optical power;

[0036] The second lens L2 is a biconvex lens with positive refractive power;

[0037] The MEMS galvanometer M1 is essentially a circular plane mirror;

[0038] The third lens L3 is a meniscus lens with negative optical power;

[0039] The fourth lens L4 is a biconcave or plano-concave lens with negative refractive power.

[0040] Specifically, the angle-expanding lens provided in an embodiment of the present invention is applied to a MEMS laser radar; the light emitted by the light source passes through the first lens L1, the second lens L2, the MEMS galvanometer M1, the third lens L3 and the fourth lens L4 in sequence, and finally exits to achieve a 60° field of view scanning.

[0041] Optionally, the air thickness between the first lens L1 and the second lens L2 ranges from 0.49 to 0.51 mm; the air thickness between the second lens L2 and the MEMS galvanometer M1 ranges from 9.1 to 10.8 mm; the air thickness between the MEMS galvanometer M1 and the third lens L3 ranges from 13.1 to 14.8 mm; and the air thickness between the third lens L3 and the fourth lens L4 ranges from 17.7 to 21.7 mm.

[0042] Specifically, the air thickness refers to the shortest distance from the center of the image side surface of one lens to the center of the object side surface of the next lens; the specific air thickness between lenses is determined according to actual conditions and is not limited in the embodiments of the present invention.

[0043] Optionally, the material of the first lens L1 includes heavy lanthanum flint glass, the object-side surface of the first lens L1 is convex, and the radius of the curvature of the object-side surface of the first lens L1 ranges from 6.035 to 6.063 mm; the image-side surface of the first lens L1 is concave, and the radius of the curvature of the image-side surface of the first lens L1 ranges from 5.164 to 5.181 mm.

[0044] Specifically, the material of the first lens L1 includes wave material H-ZLAF90; the thickness of the first lens L1 ranges from 3 to 7 mm. The specific thickness is determined according to actual conditions and is not limited in the embodiment of the present invention.

[0045] In a specific embodiment, the refractive index of the first lens L1 is 2.000, and the Abbe coefficient of the first lens L1 is 25.425.

[0046] Optionally, the material of the second lens L2 includes heavy lanthanum flint glass, the object-side surface of the second lens L2 is convex, and the radius of the curvature of the object-side surface of the second lens L2 ranges from 18.838 to 19.076 mm; the image-side surface of the second lens L2 is convex, and the radius of the curvature of the image-side surface of the second lens L2 ranges from -7.074 to -7.051 mm.

[0047] Specifically, the material of the second lens L2 includes wave material H-ZLAF90; the thickness of the second lens L2 ranges from 3.17 to 3.23 mm. The specific thickness is determined according to actual conditions and is not limited in the embodiments of the present invention.

[0048] In a specific embodiment, the refractive index of the second lens L2 is 2.000, and the Abbe coefficient of the second lens L2 is 25.425.

[0049] Optionally, the MEMS galvanometer M1 is a circular plane reflective mirror, and the radius of the MEMS galvanometer M1 is greater than 4.7 mm; the mechanical vibration angle range of the MEMS galvanometer M1 is -7.5 to 7.5 degrees.

[0050] In a specific embodiment, the radius of the MEMS galvanometer M1 is 2.5 mm, and the mechanical vibration angle range of the MEMS galvanometer M1 is -7.5 to 7.5 degrees.

[0051] Optionally, the material of the third lens L3 includes heavy lanthanum flint glass, the object side surface of the third lens L3 is concave, and the radius of the curvature of the object side surface of the third lens L3 ranges from 12.857 to 13.072 mm; the image side surface of the third lens L3 is convex, and the radius of the curvature of the image side surface of the third lens L3 ranges from 15.907 to 16.196 mm.

[0052] Specifically, the material of the third lens L3 includes wave material H-ZLAF90; the thickness of the third lens L3 ranges from 2.85 to 3.88 mm. The specific thickness is determined according to actual conditions and is not limited in the embodiments of the present invention.

[0053] In a specific embodiment, the refractive index of the third lens L3 is 2.000, and the Abbe coefficient of the third lens L3 is 25.425.

[0054] Optionally, the material of the fourth lens L4 includes heavy lanthanum flint glass, the object side surface of the fourth lens L4 is concave, and the range of the radius of the curved surface of the object side surface of the fourth lens L4 is 36.532 to 40.196 mm; the image side surface of the fourth lens L4 is concave or flat, and the range of the radius of the curved surface of the image side surface of the fourth lens L4 is -∞ to

[0055] -900mm.

[0056] Specifically, the material of the fourth lens L4 includes wave material H-ZLAF90; the thickness of the fourth lens L4 ranges from 1 to 4 mm, and the specific thickness is determined according to actual conditions and is not limited in the embodiment of the present invention.

[0057] In a specific embodiment, the refractive index of the fourth lens L4 is 2.000, and the Abbe coefficient of the fourth lens L4 is 25.425.

[0058]

[0059] like Figure 1 As shown, the optical scanning angle of this embodiment is 60 degrees, which shows that the angle expansion of this embodiment has achieved a good effect.

[0060] like Figure 2 and 3 As shown, the optical divergence angle of the embodiment with a field of view angle of 0° is 0.044 millirads, and the optical divergence angle with a field of view angle of 30° is 0.056 millirads, indicating that the beam divergence angle of the embodiment is well controlled.

[0061] like Figure 4 As shown, the MEMS micro-vibration mirror angle of this embodiment is substantially linearly related to the corresponding FOV angle, indicating that this embodiment achieves linear scanning.

[0062] like Figure 5and Figure 6 As shown, under extreme temperatures (-40°C, 85°C), the maximum optical divergence angle of this embodiment is still less than 0.2mrad, and the MEMS micro-mirror angle and the corresponding FOV angle still maintain a linear relationship, indicating that the temperature adaptability of this embodiment is very good.

Claims

1. An angle expansion lens for a MEMS galvanometer, characterized in that: The optical axis includes a first lens, a second lens, a MEMS galvanometer, a third lens, and a fourth lens from the object side to the image side in sequence; wherein, The first lens is a meniscus lens with negative optical power; The second lens is a biconvex lens with positive optical power; The MEMS galvanometer is a circular plane reflective mirror; The third lens is a meniscus lens with negative optical power; The fourth lens is a biconcave or plano-concave lens with negative optical power.

2. The angle expansion lens for MEMS galvanometer according to claim 1, characterized in that: The air thickness between the first lens and the second lens ranges from 0.49 to 0.51 mm; the air thickness between the second lens and the MEMS galvanometer ranges from 9.1 to 10.8 mm; the air thickness between the MEMS galvanometer and the third lens ranges from 13.1 to 14.8 mm; and the air thickness between the third lens and the fourth lens ranges from 17.7 to 21.7 mm.

3. The angle expansion lens for MEMS galvanometer according to claim 1, characterized in that: The material of the first lens includes heavy lanthanum flint glass, the object side surface of the first lens is convex, and the curvature radius of the object side surface of the first lens ranges from 6.035 to 6.063 mm; the image side surface of the first lens is concave, and the curvature radius of the image side surface of the first lens ranges from 5.164 to 5.181 mm.

4. The angle expansion lens for MEMS galvanometer according to claim 1, characterized in that: The material of the second lens is heavy lanthanum flint glass, the object side surface of the second lens is convex, and the curvature radius of the object side surface of the second lens ranges from 18.838 to 19.076 mm; the image side surface of the second lens is convex, and the curvature radius of the image side surface of the second lens ranges from -7.074 to -7.051 mm.

5. The angle expansion lens for MEMS galvanometer according to claim 1, characterized in that: The MEMS oscillating mirror is a circular plane reflecting mirror, and the radius of the MEMS oscillating mirror is greater than 4.7 mm; the mechanical vibration angle range of the MEMS oscillating mirror is -7.5 to 7.5 degrees.

6. The angle expansion lens for MEMS galvanometer according to claim 1, characterized in that: The material of the third lens includes heavy lanthanum flint glass, the object side surface of the third lens is concave, and the radius of the curvature of the object side surface of the third lens ranges from 12.857 to 13.072 mm; the image side surface of the third lens is convex, and the radius of the curvature of the image side surface of the third lens ranges from 15.907 to 16.196 mm.

7. The angle expansion lens for MEMS galvanometer according to claim 1, characterized in that: The material of the fourth lens includes heavy lanthanum flint glass, the object side surface of the fourth lens is concave, and the curvature radius of the object side surface of the fourth lens ranges from 36.532 to 40.196 mm; the image side surface of the fourth lens is concave or flat, and the curvature radius of the image side surface of the second lens ranges from -∞ to -900 mm.

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