阅读说明：本技术 大视场激光光束扫描系统及其设计方法和激光雷达装置 (Large-field-of-view laser beam scanning system, design method thereof and laser radar device ) 是由 罗先刚 张飞 蒲明博 李雄 马晓亮 罗欣 于 2021-09-10 设计创作，主要内容包括：本发明公开了大视场激光光束扫描系统及其设计方法和激光雷达装置,大视场激光光束扫描系统包括：平面微透镜阵列,具有第一介质衬底和阵列形成在第一介质衬底入射面上的若干组第一介质结构,形成若干组平面微透镜；平面二次相位透镜,具有第二介质衬底和形成在第二介质衬底出射面上的第二介质结构,第二介质结构和第一介质结构为亚波长结构,平面二次相位透镜与平面微透镜阵列匹配实现入射光的调制并产生出射方向不同且覆盖大视场的若干束阵列出射光束；微驱动器,与平面二次相位透镜连接并驱动其在垂直于其光轴的平面内以设定幅度振动,同时使若干束阵列出射光束同步在小视场内连续扫描。本发明质量轻、易集成、尺寸紧凑、视场大且扫描速度快。(The invention discloses a large-view field laser beam scanning system, a design method thereof and a laser radar device, wherein the large-view field laser beam scanning system comprises: the planar micro-lens array is provided with a first medium substrate and a plurality of groups of first medium structures which are formed on an incidence surface of the first medium substrate in an array mode, and a plurality of groups of planar micro-lenses are formed; the planar secondary phase lens is provided with a second medium substrate and a second medium structure formed on the emergent surface of the second medium substrate, the second medium structure and the first medium structure are sub-wavelength structures, and the planar secondary phase lens is matched with the planar micro-lens array to realize the modulation of incident light and generate a plurality of beam array emergent beams which have different emergent directions and cover a large visual field; and the micro driver is connected with the planar secondary phase lens and drives the planar secondary phase lens to vibrate with a set amplitude in a plane vertical to the optical axis of the planar secondary phase lens, and simultaneously, a plurality of beam array emergent light beams are enabled to be synchronously and continuously scanned in a small field of view. The invention has the advantages of light weight, easy integration, compact size, large field of view and high scanning speed.)

1. A large field of view laser beam scanning system, comprising:

the planar micro-lens array is provided with a first medium substrate and a plurality of groups of first medium structures which are formed on an incidence surface of the first medium substrate in an array mode, and a plurality of groups of planar micro-lenses are formed;

the planar secondary phase lens is provided with a second medium substrate and a second medium structure formed on the emergent surface of the second medium substrate, the second medium structure and the first medium structure are sub-wavelength structures, the planar secondary phase lens is matched with the planar micro-lens array to realize modulation of incident light and generate a plurality of beam array emergent beams which have different emergent directions and cover a large visual field;

and the micro driver is connected with the planar secondary phase lens and drives the planar secondary phase lens to vibrate with a set amplitude in a plane vertical to the optical axis of the planar secondary phase lens, and simultaneously the plurality of beam array emergent light beams are enabled to be synchronously and continuously scanned in a small field of view.

2. The large-field laser beam scanning system according to claim 1, wherein the set amplitude of the planar secondary phase lens vibration is within the period P of the planar micro-lens array, so that the outgoing beams of the plurality of beam arrays cover the entire 2 pi field without dead angles.

3. The large field of view laser beam scanning system of claim 1, wherein said incident light is a parallel laser beam or a diverging laser beam, said planar microlens array is capable of modulating said incident light and producing sets of array point sources, said planar secondary phase lens is capable of modulating light from said sets of array point sources located on a planar secondary phase lens focal plane and producing said sets of array exit beams.

4. The large field of view laser beam scanning system of claim 1, wherein said first dielectric substrate is made of alumina, silica or magnesium fluoride, and has a thickness t₁And t is₁Is more than or equal to 10 lambda, and the diameter or the minimum characteristic length of the first dielectric substrate is D₁And D₁Not less than MP; the second dielectric substrate is made of aluminum oxide, silicon dioxide or magnesium fluoride, and the thickness of the second dielectric substrate is t₂And t is₂Not less than 10 lambda, saidThe diameter or minimum feature length of the two-dielectric substrate is D₂And D₂≥MP+d；

Where d is the diameter of the emerging beam and θ_maxMaximum angle of emergence of the emergent beam, f₂Is the focal length of the planar secondary phase lens and f₂＝MP/2sinθ_maxM is the array number of the planar microlens array in the horizontal or vertical direction, P is a period of the planar microlens array, P is not less than 10 lambda and lambda is the wavelength of incident light, and the focal length f of the planar microlens array₁≈Pf₂/d。

5. The large-field laser beam scanning system according to claim 1, wherein the first dielectric structure is a sub-wavelength structure capable of realizing any wavefront modulation and is made of silicon, titanium dioxide or gallium nitride, the first dielectric structure is entirely circular, quadrangular or octagonal and is arrayed on the incident plane of the first dielectric substrate in a quadrangular arrangement or a hexagonal arrangement, the sub-wavelength structure of the first dielectric structure is one of any axisymmetric structural forms and is arranged in a regular quadrangular lattice structure or a regular hexagonal lattice structure to realize polarization-independent response;

the second dielectric structure is the same as or different from the sub-wavelength structure of the first dielectric structure and is made of silicon, titanium dioxide or gallium nitride, the sub-wavelength structure of the second dielectric structure is one of any axisymmetric structural forms and is arranged in a regular quadrilateral lattice structure or a regular hexagonal lattice structure;

the arrangement period of the sub-wavelength structures is L, lambda/6 is larger than or equal to L and smaller than or equal to lambda, the height is h, lambda/6 is larger than or equal to h and smaller than or equal to 2 lambda, the structure width is a, 0 is larger than a and smaller than or equal to L, and lambda is the wavelength of incident light.

6. The large field of view laser beam scanning system of claim 1, wherein the direction of the optical axis of the planar secondary phase lens is the z-axis direction, the plane perpendicular to the optical axis is the xy-plane including the x-axis and the y-axis perpendicular to each other, and the exit angle of any exit beam of the plurality of array exit beams is the exit angle of the exit beamIs (theta, beta), wherein, theta is an included angle between the emergent beam and the optical axis of the planar secondary phase lens, beta is an included angle between the projection of the emergent beam on the xy plane and the x-axis direction, and f₂Is the focal length, S, of a planar secondary phase lens_XAnd S_YThe X-axis component and the Y-axis component of the S are respectively, and the S is the distance between the optical axis of the planar secondary phase lens and the optical axis of the planar micro-lens corresponding to any emergent light beam.

7. The large-field-of-view laser beam scanning system of claim 1, wherein the large field of view is capable of covering an exit range of-90 ° to 90 °, and a small field of view corresponding to any exit beam is capable of covering arcsin [ (S- | a |)/f₂]～arcsin[(S+|A|)/f₂]The scanning range of (a);

the micro-actuator is a piezoelectric micro-actuator, an MEMS micro-actuator, a magnetic micro-actuator or a micro-motor, and the actuating force F of the micro-actuator is mA omega²sin (ω t), where m is the mass of the planar secondary phase lens, ω is the execution speed of the micro-driver, a is the execution displacement of the micro-driver and-P/2 is not less than a and not more than P/2, and S is the distance between the optical axis of the planar secondary phase lens and the optical axis of the planar micro-lens corresponding to any one of the outgoing beams.

8. The design method of the large-field laser beam scanning system according to any one of claims 1 to 7, comprising the steps of:

A. based on the array number M and the period P of the given planar microlens array in the horizontal or vertical direction, the diameter d of the emergent beam and the maximum emergent angle theta of the emergent beam_maxCalculating to obtain the focal length f of the planar microlens array₁And the diameter or minimum feature length D of the first dielectric substrate₁And a planar secondary phase lensFocal length f of₂And the diameter or minimum feature length D of the second dielectric substrate₂；

B. Given the wavelength λ of the incident light, the focal length f of the planar secondary phase lens₂Obtaining the phase distribution of a planar secondary phase lensDetermining the material and thickness t of the second dielectric substrate of the planar secondary phase lens₂And the material and thickness t of the first dielectric substrate of the planar microlens array₁Wherein (x)₁，y₁) Is a position coordinate, k, on a planar secondary phase lens₀＝2π/λ；

C. Optimizing phase distribution of a set of planar microlenses using ray tracing in combination with incident light characteristicsWherein (x)₂，y₂) Is a position coordinate on a group of planar micro-lenses, N is more than or equal to 5, a_iIs a phase coefficient;

D. selecting a material of a second medium structure of the planar secondary phase lens and a material of a first medium structure of the planar micro-lens array according to the wavelength lambda of incident light, optimally designing the second medium structure and obtaining a mapping relation between the structure width a and the phase of the second medium structure, and performing structure and parameter selection of a sub-wavelength structure by combining the phase distribution obtained in the step B and the step C on the basis of the mapping relation to obtain a sub-wavelength structure layout of the planar secondary phase lens and a group of planar micro-lenses;

E. and arraying the subwavelength structure layouts of the group of planar microlenses in a preset arrangement mode to obtain an array layout of the planar microlens array, processing and preparing the planar secondary phase lens and the planar microlens array based on the information, and assembling the planar secondary phase lens and the planar microlens array with a micro driver in a combined manner to obtain the subwavelength structure-based large-field laser beam scanning system.

9. A lidar apparatus, comprising:

a laser light source for generating incident light;

the large-field laser beam scanning system according to any one of claims 1 to 7, configured to receive incident light from the laser light source and realize modulation of the incident light, generate a plurality of beam array emergent beams with different emergent directions and covering a large field of view, and simultaneously enable the plurality of beam array emergent beams to continuously scan in a small field of view synchronously;

and the receiving detection system is used for receiving the echo signal reflected by the target and acquiring target information according to the echo signal.

10. The lidar apparatus of claim 9, wherein the laser light source is a VCSEL area array light source, an expanded beam collimated light source, or a divergent point source; the array detector of the receiving detection system is arranged at the focal plane of the planar secondary phase lens in the large-field laser beam scanning system to independently detect the echo signal of each emergent beam.

Technical Field

The invention belongs to the technical field of laser radars, and particularly relates to a large-field-of-view laser beam scanning system based on a planar sub-wavelength structure, a design method of the large-field-of-view laser beam scanning system and a laser radar device.

Background

The laser radar can accurately acquire the distance and speed information of a target, and can realize target detection and imaging, so that the laser radar has good application prospect in the fields of intelligent transportation, unmanned aerial vehicle obstacle avoidance, smart homes, satellite surveying and mapping, navigation and the like. The laser beam scanning system is used as a core component of the laser radar and plays an important role in the performance of the laser radar.

At present, the principles of laser beam scanning devices can be divided into two main categories: mechanical laser beam scanning and solid state laser beam scanning. The mechanical laser beam scanning adopts a mechanical rotating part as a beam scanning implementation mode, large-angle scanning can be achieved, but assembly is difficult, and scanning frequency is low. Current implementations of solid state laser beam scanning are micro-electromechanical systems (MEMS), optical phased array technology (OPA), etc. The MEMS adopts a micro-scanning galvanometer, so that a certain integration level is achieved, but the scanning field of view is still limited by the deflection range of the galvanometer; the OPA scanning technology is a novel light beam pointing control technology developed based on a microwave phased array scanning theory and technology, has the advantages of no inertial device, accuracy and stability, random direction control and the like, but the light beam scanning field of view is smaller due to the fact that the phase regulation unit period is larger.

Based on the above background and current state of the art, the realization of the all-solid-state and miniaturized laser beam scanning system with high power, large scanning angle, high resolution and other high performance parameters still needs further research.

Disclosure of Invention

The present invention provides a large field of view laser beam scanning system, a method of designing the same and a lidar device to at least partially address the above-identified technical problems.

To this end, one aspect of the invention provides a large field of view laser beam scanning system comprising:

the planar micro-lens array is provided with a first medium substrate and a plurality of groups of first medium structures which are formed on an incidence surface of the first medium substrate in an array mode, and a plurality of groups of planar micro-lenses are formed;

the planar secondary phase lens is provided with a second medium substrate and a second medium structure formed on the emergent surface of the second medium substrate, the second medium structure and the first medium structure are sub-wavelength structures, the planar secondary phase lens is matched with the planar micro-lens array to realize modulation of incident light and generate a plurality of beam array emergent beams which have different emergent directions and cover a large visual field;

and the micro driver is connected with the planar secondary phase lens and drives the planar secondary phase lens to vibrate with a set amplitude in a plane vertical to the optical axis of the planar secondary phase lens, and simultaneously the plurality of beam array emergent light beams are enabled to be synchronously and continuously scanned in a small field of view.

Furthermore, the set amplitude of the vibration of the planar secondary phase lens is within the period P of the planar micro-lens array, so that the outgoing light beams of the plurality of beam arrays can cover the whole 2 pi field without dead angles.

Further, the incident light is a parallel laser beam or a divergent laser beam, the planar microlens array can modulate the incident light and generate a plurality of groups of array point sources, and the planar secondary phase lens can modulate the light of the plurality of groups of array point sources on the planar secondary phase lens focal plane and generate a plurality of beam array emergent beams.

Further, the first dielectric substrate is made of aluminum oxide, silicon dioxide or magnesium fluoride, and the thickness of the first dielectric substrate is t₁And t is₁Is more than or equal to 10 lambda, and the diameter or the minimum characteristic length of the first dielectric substrate is D₁And D₁≥MP；

The second dielectric substrate is made of aluminum oxide, silicon dioxide or magnesium fluoride, and the thickness of the second dielectric substrate is t₂And t is₂Is more than or equal to 10 lambda, and the diameter or the minimum characteristic length of the second dielectric substrate is D₂And D₂≥MP+d；

Where d is the diameter of the emerging beam and θ_maxMaximum angle of emergence of the emergent beam, f₂Is the focal length of the planar secondary phase lens and f₂＝MP/2sinθ_maxM is the array number of the planar microlens array in the horizontal or vertical direction, P is the period of the planar microlens array, P is not less than 10 lambda and lambda is the wavelength of incident light, and the focal length f of the planar microlens array₁≈Pf₂/d。

Further, the first dielectric structure is a sub-wavelength structure capable of realizing any wavefront regulation and is made of silicon, titanium dioxide or gallium nitride, the first dielectric structure is integrally circular, quadrangular or octagonal and is arrayed on the incident plane of the first dielectric substrate in a quadrangular arrangement or hexagonal arrangement mode, the sub-wavelength structure of the first dielectric structure is one of any structure forms symmetrical along an axis and is arranged in a regular quadrangular lattice structure or a regular hexagonal lattice structure to realize polarization-independent response;

the second dielectric structure is the same as or different from the sub-wavelength structure of the first dielectric structure and is made of silicon, titanium dioxide or gallium nitride, the sub-wavelength structure of the second dielectric structure is one of any axisymmetric structural forms and is arranged in a regular quadrilateral lattice structure or a regular hexagonal lattice structure;

the arrangement period of the sub-wavelength structures is L, lambda/6 is larger than or equal to L and smaller than or equal to lambda, the height is h, lambda/6 is larger than or equal to h and smaller than or equal to 2 lambda, the structure width is a, 0 is larger than a and smaller than or equal to L, and lambda is the wavelength of incident light.

Furthermore, the direction of the optical axis of the planar secondary phase lens is taken as the z-axis direction, the plane perpendicular to the optical axis is taken as the xy-plane including the x-axis and the y-axis which are perpendicular to each other, and the emergent angle of any emergent beam in the plurality of beam array emergent beams is (theta, beta))，Wherein, theta is an included angle between the emergent beam and the optical axis of the planar secondary phase lens, beta is an included angle between the projection of the emergent beam on the xy plane and the x-axis direction, and f₂Is the focal length, S, of a planar secondary phase lens_XAnd S_YThe X-axis component and the Y-axis component of the S are respectively, and the S is the distance between the optical axis of the planar secondary phase lens and the optical axis of the planar micro-lens corresponding to any emergent light beam.

Furthermore, the large visual field covers the emergent range of-90 degrees, and the small visual field corresponding to any emergent light beam covers arcsin [ (S- | A |)/f₂]～arcsin[(S+|A|)/f₂]The scanning range of (a);

the micro-actuator is a piezoelectric micro-actuator, an MEMS micro-actuator, a magnetic micro-actuator or a micro-motor, and the actuating force F of the micro-actuator is mA omega²sin (ω t), where m is the mass of the planar secondary phase lens, ω is the execution speed of the micro-driver, a is the execution displacement of the micro-driver and-P/2 is not less than a and not more than P/2, and S is the distance between the optical axis of the planar secondary phase lens and the optical axis of the planar micro-lens corresponding to any one of the outgoing beams.

Another aspect of the present invention provides a design method of the above-mentioned large-field laser beam scanning system, including the following steps:

A. based on the array number M and the period P of the given planar microlens array in the horizontal or vertical direction, the diameter d of the emergent beam and the maximum emergent angle theta of the emergent beam_maxCalculating to obtain the focal length f of the planar microlens array₁And the diameter or minimum feature length D of the first dielectric substrate₁And focal length f of the planar secondary phase lens₂And the diameter or minimum feature length D of the second dielectric substrate₂；

B. Given the wavelength λ of the incident light, the focal length f of the planar secondary phase lens₂Obtaining the phase distribution of a planar secondary phase lensDetermining the material and thickness t of the second dielectric substrate of the planar secondary phase lens₂And the material and thickness t of the first dielectric substrate of the planar microlens array₁Wherein (x)₁，y₁) Is a position coordinate, k, on a planar secondary phase lens₀＝2π/λ；

C. Optimizing phase distribution of a set of planar microlenses using ray tracing in combination with incident light characteristicsWherein (x)₂，y₂) Is a position coordinate on a group of planar micro-lenses, N is more than or equal to 5, a_iIs a phase coefficient;

D. selecting a material of a second medium structure of the planar secondary phase lens and a material of a first medium structure of the planar micro-lens array according to the wavelength lambda of incident light, optimally designing the second medium structure and obtaining a mapping relation between the structure width a and the phase of the second medium structure, and performing structure and parameter selection of a sub-wavelength structure by combining the phase distribution obtained in the step B and the step C on the basis of the mapping relation to obtain a sub-wavelength structure layout of the planar secondary phase lens and a group of planar micro-lenses;

E. and arraying the subwavelength structure layouts of the group of planar microlenses in a preset arrangement mode to obtain an array layout of the planar microlens array, processing and preparing the planar secondary phase lens and the planar microlens array based on the information, and assembling the planar secondary phase lens and the planar microlens array with a micro driver in a combined manner to obtain the subwavelength structure-based large-field laser beam scanning system.

Yet another aspect of the present invention provides a laser radar apparatus including:

a laser light source for generating incident light;

the large-view-field laser beam scanning system is used for receiving incident light from a laser light source, realizing modulation of the incident light, generating a plurality of beam array emergent beams which have different emergent directions and cover a large view field, and synchronously and continuously scanning the plurality of beam array emergent beams in a small view field;

and the receiving detection system is used for receiving the echo signal reflected by the target and acquiring target information according to the echo signal.

Further, the laser light source is a VCSEL area array light source, a beam expanding parallel light or a divergent point source, and the array detector of the receiving and detecting system is arranged at a focal plane of a planar secondary phase lens in the large-field laser beam scanning system to independently detect an echo signal of each emergent beam.

The large-view-field laser beam scanning system provided by the invention can realize continuous scanning in different view fields and has the advantages of compact size, large view field, high scanning speed and the like, wherein the planar micro lens array and the planar secondary phase lens are both formed by sub-wavelength structures, and can realize random wave front regulation and control, so that the wave front phase difference RMS of the emergent parallel beams is inhibited. In addition, the large-view-field laser beam scanning system provided by the invention has the advantages of light weight, easiness in integration and the like, and can be popularized and applied in the aspects of machine vision, three-dimensional imaging, laser radar and the like.

Drawings

FIG. 1 shows a schematic block diagram of a large field of view laser beam scanning system according to an exemplary embodiment of the present invention.

Fig. 2 is a schematic diagram of a large field of view laser beam scanning system in combination with a VCSEL area array light source according to another exemplary embodiment of the present invention.

Fig. 3a and 3b show phase profiles of a planar microlens and a planar secondary phase lens, respectively, in a large-field laser beam scanning system according to embodiment 1 of the present invention.

Fig. 4 is a schematic structural diagram illustrating a sub-wavelength structure of a planar microlens and a planar secondary phase lens in a large-field laser beam scanning system according to embodiment 1 of the present invention.

Fig. 5a and 5b show the phase distribution diagram and the amplitude variation diagram corresponding to the sub-wavelength structure of the planar microlens and the planar secondary phase lens in the large-field laser beam scanning system according to embodiment 1 of the present invention at different structure widths a, respectively.

Fig. 6a to 6c respectively show simulation results corresponding to the large-field laser beam scanning system according to embodiment 1 of the present invention, where fig. 6a and 6b respectively show simulation wavefronts corresponding to the emergent beams at different S in the y-axis direction, and fig. 6c shows simulation results of maximum wavefront phase differences corresponding to different scanning angles θ of the emergent beams.

Fig. 7 is a diagram showing simulation and theoretical results of the exit angles of the corresponding exit beams of the large-field laser beam scanning system in the y-axis direction at different S according to the embodiment 1 of the present invention.

Fig. 8a to 8c show simulation results of scanning of the emergent beam corresponding to the planar secondary phase lens being driven by the micro-driver in the y-axis direction to vertically move within one planar microlens array period by the planar secondary phase lens in the large-field laser beam scanning system according to embodiment 1 of the present invention, where vertical moving distances corresponding to fig. 8a to 8c are respectively a-0, a-P/2, and a-P/2.

Description of reference numerals:

1-plane microlens array, 11-first dielectric structure, 12-first dielectric substrate, 2-plane secondary phase lens, 21-second dielectric structure, 22-second dielectric substrate, and 3-micro driver.

Detailed Description

All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.

Any feature disclosed in this specification may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features.

The invention provides a large-view-field laser beam scanning system based on a planar sub-wavelength structure, a design method thereof and a laser radar device, wherein the constructed large-view-field laser beam scanning system can realize beam scanning of a large view field and cover the whole 2 pi view field.

The large field of view laser beam scanning system of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 is a schematic structural diagram illustrating a large-field-of-view laser beam scanning system according to an exemplary embodiment of the present invention, and fig. 2 is a schematic structural diagram illustrating a large-field-of-view laser beam scanning system combined with a VCSEL area array light source according to another exemplary embodiment of the present invention.

As shown in fig. 1 and 2, according to an exemplary embodiment of the present invention, the large field-of-view laser beam scanning system includes: the planar micro-lens array 1 is provided with a first medium substrate 12 and a plurality of groups of first medium structures 11 arrayed on an incidence surface of the first medium substrate 12 to form a plurality of groups of planar micro-lenses; the planar secondary phase lens 2 is provided with a second medium substrate 22 and a second medium structure 21 formed on the emergent surface of the second medium substrate 22, the second medium structure 21 and the first medium structure 11 are sub-wavelength structures, and the planar secondary phase lens 2 is matched with the planar micro-lens array 1 to realize the modulation of incident light and generate a plurality of beam array emergent beams which have different emergent directions and cover a large visual field; and the micro driver 3 is connected with the planar secondary phase lens 2 and drives the planar secondary phase lens to vibrate with a set amplitude in a plane vertical to the optical axis of the planar secondary phase lens, and simultaneously, a plurality of beam array emergent light beams are continuously scanned in a small field of view synchronously.

In order to ensure that the array emergent beams can cover the whole 360 ranges, the set amplitude of the vibration of the planar secondary phase lens 2 is preferably controlled within one planar microlens array period P, so that the plurality of beam array emergent beams can cover the whole 2 pi field of view (namely 360-degree field of view) without dead angles.

The incident light suitable for the invention can be parallel laser beams (as shown in figure 1) or divergent laser beams (as shown in figure 2), is not only suitable for near infrared bands, but also suitable for optical bands, terahertz bands and microwave bands, and can be specifically designed into a planar micro-lens array and a planar secondary phase lens according to the incident light. When the laser beam is selected for emission, the phase distribution of the planar microlens array needs to be further optimized according to the divergence characteristic during design.

The planar micro-lens array 1 and the planar secondary phase lens 2 are both realized by a sub-wavelength structure, and the planar micro-lens array and the planar secondary phase lens have the advantages that any wave front regulation and control can be realized, so that the wave front difference RMS of an emergent light beam is inhibited; and the planar micro-lens array 1 and the planar secondary phase lens 2 adopt an all-dielectric structure, have the advantages of low loss, high efficiency and the like, and can realize high-efficiency and low-scattering regulation and control of incident light.

Specifically, the planar microlens array 1 is capable of modulating incident light and producing sets of array point sources at the focal plane of the planar secondary phase lens, while the planar secondary phase lens 2 is capable of modulating light of the sets of array point sources and producing sets of array exit beams. Fig. 1 and 2 respectively show an emergent beam obtained after incident lights of different light sources are modulated by the planar microlens array 1 and the planar secondary phase lens 2, wherein an included angle between the emergent beam and the optical axis of the planar secondary phase lens 2 is an emergent angle.

Specifically, the first dielectric substrate 12 of the planar microlens array 1 may be made of alumina, silicon dioxide or magnesium fluoride, and has a thickness t₁And t is₁Is more than or equal to 10 lambda, and the diameter or the minimum characteristic length of the first dielectric substrate is D₁And D₁Not less than MP. The second dielectric substrate 22 of the planar secondary phase lens 2 may also be made of alumina, silicon dioxide or magnesium fluoride, and has a thickness t₂And t is₂Is more than or equal to 10 lambda, and the diameter or the minimum characteristic length of the second dielectric substrate is D₂And D₂More than or equal to MP + d. The shapes of the first dielectric substrate and the second dielectric substrate may be common shapes such as a circle, a square, and the like, which is not limited in the present invention.

Where d is the diameter of the emerging beam and θ_maxMaximum angle of emergence of the emergent beam, f₂Is the focal length of the planar secondary phase lens and f₂＝MP/2sinθ_maxM is the array number of the planar microlens array in the horizontal or vertical direction, P is a period of the planar microlens array, P is not less than 10 lambda and lambda is the wavelength of incident light, and the focal length f of the planar microlens array₁≈Pf₂/d。

In this way,by giving d, theta_maxM and P, the focal length f of the planar microlens array 1 and the planar secondary phase lens 2 can be obtained₁And f₂And further designing to obtain a medium structure meeting the corresponding functional requirements.

According to the present invention, the first dielectric structures 11 of the planar microlens array 1 are sub-wavelength structures capable of realizing any wavefront control and are made of silicon, titanium dioxide or gallium nitride, the first dielectric structures 11 are circular, quadrilateral or hexagonal as a whole and are arrayed on the incident plane of the first dielectric substrate 12 in a quadrilateral arrangement or a hexagonal arrangement, the sub-wavelength structures of the first dielectric structures 11 may be one of any axisymmetric structural forms, such as octagon, square, circle, etc., and are arranged in a regular quadrilateral lattice structure or a regular hexagonal lattice structure to realize polarization-independent response.

The second dielectric structure 21 of the planar secondary phase lens 2 may be the same as or different from the subwavelength structure of the first dielectric structure and made of silicon, titanium dioxide or gallium nitride, and the subwavelength structure of the second dielectric structure 11 may also be one of any axisymmetric structural forms and arranged in a regular tetragonal lattice structure or a regular hexagonal lattice structure. Preferably, the second dielectric structure 21 of the planar secondary phase lens 2 is the same structure but different in size and arrangement as the first dielectric structure 11 of the planar microlens array 1.

Wherein, the arrangement period of the sub-wavelength structure is L, λ/6 is not less than L and not more than λ, the height is h, λ/6 is not less than h and not more than 2 λ, the structure width is a, 0 < a and not more than L, λ is the wavelength of the incident light, and those skilled in the art know how the arrangement period L, the height h and the structure width a of different sub-wavelength structures are defined, and are not described herein again.

When the plane secondary phase lens is matched with the plane micro-lens array to realize function matching, the plane micro-lens array can realize random wave front regulation and generate a point source perfectly matched with the plane secondary phase lens, so that the RMS of an emergent beam is effectively inhibited, and the plane secondary phase lens can convert the translational symmetry of the point source into the rotational symmetry of the emergent beam, so that the beam scanning of a large field of view is realized. Also, the number and diameter of the outgoing beams can be determined by the number and period of the planar microlenses.

Taking fig. 1 and fig. 2 as an example, when the direction of the optical axis of the planar secondary phase lens is taken as the z-axis direction, and the plane perpendicular to the optical axis is taken as the xy-plane including the x-axis and the y-axis which are perpendicular to each other, the exit angle of any exit beam in the plurality of beam array exit beams is (θ, β),wherein, theta is an included angle between the emergent beam and the optical axis of the planar secondary phase lens, beta is an included angle between the projection of the emergent beam on the xy plane and the x-axis direction, and f₂Is the focal length, S, of a planar secondary phase lens_XAnd S_YThe X-axis component and the Y-axis component of the S are respectively, and the S is the distance between the optical axis of the planar secondary phase lens and the optical axis of the planar micro-lens corresponding to any emergent light beam.

When the planar secondary phase lens is still, the distance S between the optical axis of the planar secondary phase lens and the optical axis of the planar microlens corresponding to any outgoing beam is fixed, i.e. S is equal to the original distance S₀And the exit angles of the exit beams of the plurality of beam arrays are also fixed and cover a corresponding large field range. However, when the planar secondary phase lens is dithered in the XY plane by the microactuator, the distance S between the optical axis of the planar secondary phase lens and the optical axis of the planar microlens for any outgoing beam changes from time to time, i.e., S equals S₀A, a is the performed displacement of the micro-drive, where the exit angles of the several array exit beams also achieve a continuous scanning over a small field of view on the basis of the original exit angle, thereby making the array exit beams cover the entire 2 pi field of view.

According to the present invention, the micro-actuator 3 may be a piezoelectric micro-actuator, a MEMS micro-actuator, a magnetic micro-actuator or a micro-motor, the micro-actuator having an actuating force F ═ mA ω²sin (ω t), where m is the mass of the planar secondary phase lens, ω is the execution speed of the micro-actuator, A is the execution displacement of the micro-actuator and-P/2 is greater than or equal to A is less than or equal to P/2.

It can be seen that the actuating force F is mainly influenced by the mass of the moving part, given a fixed oscillation frequency and fixed actuating displacement of the microactuator. The planar secondary phase lens is composed of a sub-wavelength structure, and has the advantage of light weight, so when the execution force F is fixed, the smaller the mass m of the planar secondary phase lens is, the faster the execution response speed of the micro-driver is, and the higher the scanning frequency is, thereby being more beneficial to realizing the expected view field and execution speed of laser beam scanning.

Aiming at the large-view-field laser beam scanning system, the large view field can realize the emission range of covering-90 degrees to 90 degrees, and the small view field corresponding to any emission beam can cover arcsin [ (S- | A |)/f₂]～arcsin[(S+|A|)/f₂]The scanning range of (1).

The invention also provides a design method for the large-field laser beam scanning system, which specifically comprises the following steps.

Step A:

based on the array number M and the period P of the given planar microlens array in the horizontal or vertical direction, the diameter d of the emergent beam and the maximum emergent angle theta of the emergent beam_maxCalculating to obtain the focal length f of the planar microlens array₁And the diameter or minimum feature length D of the first dielectric substrate₁And focal length f of the planar secondary phase lens₂And the diameter or minimum feature length D of the second dielectric substrate₂。

In particular, d is the diameter of the outgoing beam, θ_maxMaximum angle of emergence of the emergent beam, f₂Is the focal length of the planar secondary phase lens and f₂＝MP/2sinθ_maxM is the array number of the planar microlens array in the horizontal or vertical direction, P is the period of the planar microlens array, P is not less than 10 lambda and lambda is the wavelength of incident light, and the focal length f of the planar microlens array₁≈Pf₂D, the diameter or minimum characteristic length of the first dielectric substrate is D₁And D₁≧ MP, the diameter or minimum feature length of the second dielectric substrate is D₂And D₂≥MP+d。

And B:

given the wavelength λ of the incident light, on a planar basisFocal length f of secondary phase lens₂Obtaining the phase distribution of a planar secondary phase lensDetermining the material and thickness t of the second dielectric substrate of the planar secondary phase lens₂And the material and thickness t of the first dielectric substrate of the planar microlens array₁Wherein (x)₁，y₁) Is a position coordinate, k, on a planar secondary phase lens₀＝2π/λ。

The first dielectric substrate can be made of aluminum oxide, silicon dioxide or magnesium fluoride, and the thickness of the first dielectric substrate is t₁And t is₁Not less than 10 lambda; the second dielectric substrate can be made of aluminum oxide, silicon dioxide or magnesium fluoride, and the thickness of the second dielectric substrate is t₂And t is₂≥10λ。

And C:

optimizing phase distribution of a set of planar microlenses using ray tracing in combination with incident light characteristicsWherein (x)₂，y₂) Is a position coordinate on a group of planar micro-lenses, N is more than or equal to 5, a_iIs the phase coefficient. Wherein, N is an empirical value, and the larger N is, the more flexible the corresponding phase distribution is, and the RMS can be better suppressed.

Step D:

selecting a material of a second medium structure of the planar secondary phase lens and a material of a first medium structure of the planar micro-lens array according to the wavelength lambda of incident light, optimally designing the second medium structure and obtaining a mapping relation between the structure width a and the phase of the second medium structure, and performing structure and parameter selection of a sub-wavelength structure by combining the phase distribution obtained in the step B and the step C on the basis of the mapping relation to obtain a sub-wavelength structure layout of the planar secondary phase lens and a group of planar micro-lenses, wherein the simulation optimization can be specifically performed by adopting CST electromagnetic simulation software and ZEMAX optical design software.

The first dielectric structure and the second dielectric structure can be made of silicon, titanium dioxide or gallium nitride, the first dielectric structure is round, quadrilateral or octagonal as a whole and is arrayed on the incident plane of the first dielectric substrate in a quadrilateral arrangement or a hexagonal arrangement mode, the sub-wavelength structures of the first dielectric structure and the second dielectric structure can be one of any structural forms symmetrical along the x axis and the y axis and are arranged in a regular quadrilateral lattice structure or a regular hexagonal lattice structure to realize polarization-independent response. The arrangement period of the sub-wavelength structures is L, lambda/6 is more than or equal to L and less than or equal to lambda, the height is h, lambda/6 is more than or equal to h and less than or equal to 2 lambda, the width of the structures is a, 0 is more than a and less than or equal to L, and lambda is the wavelength of incident light.

Step E:

and (3) arraying the subwavelength structural layouts of a group of planar microlenses in a preset arrangement mode to obtain an array layout of the planar microlens array, processing and preparing the planar secondary phase lens and the planar microlens array based on the information, and assembling the planar secondary phase lens and the planar microlens array with a micro driver in a combined manner to obtain the large-field-of-view laser beam scanning system based on the subwavelength structure.

The present invention also provides a laser radar apparatus, comprising: a laser light source for generating incident light; the large-view-field laser beam scanning system is used for receiving incident light from a laser light source, realizing modulation of the incident light, generating a plurality of beam array emergent beams which have different emergent directions and cover a large view field, and synchronously and continuously scanning the plurality of beam array emergent beams in a small view field; and the receiving detection system is used for receiving the echo signal reflected by the target and acquiring target information according to the echo signal.

The laser light source can be a VCSEL area array light source, expanded beam parallel light or a divergent point source. Compared with parallel light incidence, the light source generated by the VCSEL laser has the advantages of high peak power density of emitted light, high signal-to-noise ratio and the like, and can be flexibly controlled and integrated more easily. Meanwhile, different types of VCSEL lasers have different divergence characteristics, and therefore, the phase distribution of the planar microlens array needs to be further optimized according to the divergence characteristics.

Preferably, the array detector of the receiving detection system of the present invention may be disposed at a focal plane of a planar secondary phase lens in a large-field laser beam scanning system to independently detect an echo signal of each outgoing beam and further convert the echo signal into corresponding target information. The present invention is not limited thereto, and in fact, it falls within the scope of the present invention as long as the large-field laser beam scanning system of the present invention is employed and a corresponding laser radar apparatus is obtained based thereon.

The present invention will be further explained with reference to the following examples and drawings.

Example 1:

the embodiment designs large-field-of-view laser beam scanning based on a planar sub-wavelength structure for near-infrared bands, but is also suitable for optical bands, terahertz bands and microwave bands. The large-field laser beam scanning system of the present embodiment adopts the system structure shown in fig. 1, and is simply described by using the light source as parallel light to enter and using the micro-actuator to drive the planar secondary phase lens to vibrate in one direction in the y direction, where the exit angle β is 0 °.

In the embodiment, the CST electromagnetic simulation software and the ZEMAX optical design software are adopted to perform simulation test on the performance of the system, and the design process is not elaborated.

In particular, the thickness t of the first dielectric substrate of the planar microlens array₁0.2mm, diameter D₁9mm, one planar microlens array period P1 mm, focal length f₁2.23 mm; thickness t of second dielectric substrate of planar secondary phase lens₂0.2mm, diameter D₂12mm, focal length f₂4.5 mm; the diameter d of the emergent beam was 2 mm.

The first dielectric structure and the second dielectric structure are made of silicon, and the first dielectric substrate and the second dielectric substrate are made of aluminum oxide. In the simulation, the dielectric constant of silicon was 13.1, the dielectric constant of alumina was 3.09056, the operating wavelength λ was set to 905nm, M was 8, and θ max was 90 °.

Fig. 3a and 3b show phase profiles of a planar microlens and a planar secondary phase lens, respectively, in a large-field laser beam scanning system according to embodiment 1 of the present invention.

In pairWhen designing the sub-wavelength structure of the planar microlens and the planar secondary phase lens, the phase distribution of the planar secondary phase lens needs to be determined firstObtaining a phase distribution diagram as shown in FIG. 3b, and optimizing the phase distribution of a set of planar microlenses by ray tracing method in combination with incident light characteristicsAnd obtaining a phase distribution diagram as shown in fig. 3a, optimally designing a second dielectric structure by combining the materials of the two dielectric structures, obtaining a mapping relation between the structure width a and the phase of the second dielectric structure, and selecting the structure and parameters of the subwavelength structure by combining the phase distribution on the basis of the mapping relation.

Fig. 4 is a schematic structural diagram illustrating a sub-wavelength structure of a planar microlens and a planar secondary phase lens in a large-field laser beam scanning system according to embodiment 1 of the present invention.

As shown in fig. 4, the cross-sectional shape of the sub-wavelength structure in this embodiment is an octagon with a height h, the size of the octagon is determined by the widths a and b of the structure, and a and b have the following equation relationship: b is a/4; the subwavelength structures are arranged according to a regular hexagonal lattice structure with an arrangement period of L.

Fig. 5a and 5b show the phase distribution diagram and the amplitude variation diagram corresponding to the sub-wavelength structure of the planar microlens and the planar secondary phase lens in the large-field laser beam scanning system according to embodiment 1 of the present invention at different structure widths a, respectively.

Specifically, the arrangement period L of the sub-wavelength structure is 300nm, the height h of the sub-wavelength structure is 750nm, the wavelength of incident light is 905nm, and the performance is simulated and tested by using CST electromagnetic simulation software. Fig. 5a shows the phase change corresponding to different structure widths a under normal incidence, and it can be seen that the phase can cover 2 pi when a is changed from 100nm to 200 nm. Fig. 5b shows the amplitude variation corresponding to different structure widths a under normal incidence, and it can be seen that the average value of the amplitude is greater than 0.93 when a is varied from 100nm to 200 nm. Therefore, the characteristic size of the sub-wavelength structure can be selected based on the characteristic size, the planar micro lens and the planar secondary phase lens which meet the phase covering requirement can be designed, and the planar micro lens array can be obtained by arraying the planar micro lenses according to a specific arrangement mode.

Fig. 6a to 6c respectively show simulation results corresponding to the large-field laser beam scanning system according to embodiment 1 of the present invention, where fig. 6a and 6b respectively show simulation wavefronts corresponding to the outgoing beams at different S in the y-axis direction, and fig. 6c shows simulation results of maximum wavefront phase differences corresponding to different outgoing beams at different outgoing angles.

As can be seen from fig. 6a and 6b, in the present embodiment, when s is 0mm and s is ± 2.25mm, the RMS after the present system is adopted approaches 0. At the same time, it can be seen from fig. 6c that the RMS does not vary substantially with the exit angle of the beam.

Fig. 7 is a diagram showing simulation and theoretical results of the exit angles of the corresponding exit beams of the large-field laser beam scanning system in the y-axis direction at different S according to the embodiment 1 of the present invention.

As can be seen from fig. 7, the simulation result of the large-field laser beam scanning system designed in this embodiment is very consistent with the theoretical result. When S is changed from-4.5 mm to 4.5mm, the exit angle theta of the exit beam is changed from-90 degrees to 90 degrees, which proves that the laser beam scanning system designed by the embodiment can realize beam scanning with a large field of view.

Fig. 8a to 8c show simulation results of scanning of the emergent beam corresponding to the planar secondary phase lens being driven by the micro-driver in the y-axis direction to vertically move within one planar microlens array period by the planar secondary phase lens in the large-field laser beam scanning system according to embodiment 1 of the present invention, where vertical moving distances corresponding to fig. 8a to 8c are respectively a-0, a-P/2, and a-P/2.

In order to specifically describe the small-field scanning condition of the outgoing beam under the vibration condition, fig. 8a to 8c change the period of a plurality of planar microlens arrays in the large-field laser beam scanning system into one planar microlens array period, and other structures and parameters thereof are fixed. Here, one planar microlens array period is set to P ═ 1mm, but the planar microlens array period P is not limited to the size set here. When the actuating force F of the micro-actuator is fixed, the smaller the actuating displacement of the micro-actuator, the faster the actuating response speed, and the higher the scanning frequency, so that the one planar microlens array period P can also be set smaller. As can be seen from fig. 8a to 8c, when the planar microlens array optical axis 1 overlaps the planar secondary phase lens optical axis 2, i.e. a is 0, the light beam exit angle is 0 °; when the optical axis 1 of the planar microlens array is fixed, the optical axis 2 of the planar secondary phase lens is vertically moved in the y-axis direction, and the vertical movement distance is changed from a-P/2 to a-P/2, the beam exit angle θ is changed from 6.4 ° to-6.4 °. Therefore, when one planar microlens array period is changed into a plurality of planar microlens array periods in the large-field laser beam scanning system, if the planar secondary phase lens continuously vibrates at high frequency under the action of the micro-driver, each emergent beam can realize synchronous continuous scanning in a small-field range.

Example 2:

the large-field laser beam scanning system obtained in the embodiment 1 is adaptively combined with a laser light source and a receiving detection system, so that a corresponding laser radar device can be obtained.

The above description of the embodiments is only intended to facilitate the understanding of the method and the core idea of the present invention. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

The invention is not limited to the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification and any novel method or process steps or any novel combination of features disclosed.