A light beam scanning dimension expanding device based on transformation optics and a method thereof

Abstract

The application discloses a kind of based on transformation optics's laser radar light beam scanning dimension expansion device and method thereof, the device includes light beam collimation module, first phase plate and second phase plate;Wherein, light beam collimation module is used to emit one-dimensional straight line scanning light beam, and collimation is incident to first phase plate after;First phase plate is used to carry out light field transformation to one-dimensional straight line scanning light beam by the first phase modulation signal of loading, and one-dimensional straight line scanning light beam is transformed into two-dimensional surface array scanning light beam;Second phase plate is used to carry out wave vector correction to two-dimensional surface array scanning light beam by the second phase modulation signal of loading, and two-dimensional surface array scanning light beam parallel emission.The device provided by the application can be applied to laser radar light beam scanning system, greatly optimizes laser radar light beam scanning system structure, improves the stability of system while significantly reducing cost, can realize the customization of two-dimensional surface array scanning light field of arbitrary size, with very strong applicability.

Description

Technical Field

[0001] This invention relates to the field of lidar beam scanning technology, and in particular to a beam scanning dimension expansion device and method based on transformation optics. Background Technology

[0002] With the rapid development of autonomous driving technology, there is an urgent need for smaller, lower-power, and more stable vehicle-mounted LiDAR. Among these technologies, the beam scanning system, as one of the most crucial technologies in LiDAR, directly determines the imaging resolution and is a key guarantee for the safety of autonomous driving. To achieve real-time 3D imaging of the road scene during driving, the beam scanning system emits a two-dimensional area array scanning light field, sending a detection signal (scanning laser beam) towards the target. The received signal reflected from the target is then compared with the emitted signal to obtain the distance information of a single point scan. By scanning line by line and point by point, 3D point cloud data is obtained, reconstructing the 3D scene of the road.

[0003] Currently, the method for achieving two-dimensional area scanning in lidar beam scanning systems typically involves separately controlling the deflection of a one-dimensional beam in the x and y directions, and then combining these deflections to achieve two-dimensional scanning. This requires two sets of beam deflectors in the beam scanning system, such as MEMS (Micro-Electro-Mechanical Systems) mirrors, acousto-optic deflectors, and liquid crystal polarization gratings to control the deflection of the beam in the x and y directions respectively. This makes the beam scanning system complex, large, and expensive to manufacture, while also limiting its stability and reliability, which is not conducive to its application in automotive lidar. Alternatively, specific devices (MEMS mirrors, fiber arrays, etc.) can be placed on the output end face of a one-dimensional optical phased array to convert the one-dimensional beam into a two-dimensional beam. For example, placing a MEMS mirror on the output end face of a one-dimensional waveguide phased array reflects the light emitted from the waveguide into free space, achieving full-space two-dimensional optical scanning. However, the mechanical components in MEMS are prone to mechanical fatigue, which greatly reduces their reliability. In addition, by coupling optical fibers to the light-emitting end face of a one-dimensional optical phased array (1*16) and arranging the fibers into a 4*4 array, two-dimensional scanning of the light field is realized. However, the fiber array arrangement and processing are difficult in this method, and it is not suitable for large-scale two-dimensional beam scanning. Summary of the Invention

[0004] The present invention aims to solve the technical problems of existing beam scanning systems, such as complex structure, large size, high manufacturing cost, and low stability and reliability.

[0005] To address the aforementioned technical problems, this invention provides a beam scanning dimension expansion device based on transformation optics, comprising a beam collimation module, a first phase plate, and a second phase plate arranged sequentially along the optical path; wherein, the beam collimation module is used to emit a one-dimensional linear scanning beam, which is collimated and then incident on the first phase plate; the first phase plate is used to perform optical field transformation on the one-dimensional linear scanning beam using a first phase modulation signal, transforming the one-dimensional linear scanning beam into a two-dimensional area array scanning beam; the second phase plate is used to perform wave vector correction on the two-dimensional area array scanning beam using a second phase modulation signal, so that the two-dimensional area array scanning beam is emitted in parallel.

[0006] Preferably, the beam collimation module includes a laser module and a cylindrical lens.

[0007] Preferably, the plane of the cylindrical lens is parallel to the plane of the first phase plate.

[0008] Preferably, the first phase plate and the second phase plate are located on opposite sides of the glass substrate.

[0009] Preferably, the first phase plate and the second phase plate are etched onto the glass substrate.

[0010] Preferably, the first phase plate and the second phase plate are respectively a spatial light modulator, a diffractive optical element, and a metasurface.

[0011] Preferably, the first phase modulation signal is specifically expressed as follows:

[0012]

[0013] Where (x,y) represents the plane where the first phase plate is located, x and y represent the horizontal and vertical coordinates in (x,y) respectively, Q(x,y) represents the first phase modulation signal, β represents the horizontal scaling factor of the segmented optical field on the first phase plate plane after propagation to the second phase plate plane, k represents the wavenumber of the one-dimensional linear scanning beam, d represents the distance between the first and second phase plates, L represents the size of the horizontal scanning area of ​​the one-dimensional linear scanning beam, N represents the number of segmented optical fields of the one-dimensional linear scanning beam, and h represents the size of the vertical scanning area of ​​the two-dimensional area array scanning beam.

[0014] Preferably, the second phase modulation signal is specifically expressed as follows:

[0015]

[0016] Where (u,v) represents the plane where the second phase plate is located, u and v represent the horizontal and vertical coordinates in (u,v) respectively, and P(u,v) represents the second phase modulation signal.

[0017] This invention also provides a method for beam scanning dimension extension of the beam scanning dimension extension device as described in any of the preceding claims, comprising:

[0018] The beam collimation module emits a one-dimensional linear scanning beam, which is collimated and then incident on the first phase plate;

[0019] A preset first phase modulation signal is loaded on the first phase plate, and the light field of the one-dimensional linear scanning beam is transformed by the first phase modulation signal, thereby transforming the one-dimensional linear scanning beam into a two-dimensional area array scanning beam.

[0020] A preset second phase modulation signal is loaded on the second phase plate, and the wave vector of the two-dimensional area array scanning beam is corrected by the second phase modulation signal, and the corrected two-dimensional area array scanning beam is emitted in parallel.

[0021] Preferably, the step of transforming the one-dimensional linear scanning beam into a two-dimensional area array scanning beam includes:

[0022] The first phase plate divides the one-dimensional linear scanning beam into uniform segments, and then maps the uniformly segmented light field sequentially to different heights of the second phase plate.

[0023] This invention discloses a beam scanning dimension expansion device and method based on transformation optics. Compared with existing technologies, its advantages are as follows: When applied to a lidar beam scanning system, this device simplifies the two-dimensional beam deflector into a one-dimensional deflector, greatly optimizing the structure of the lidar beam scanning system, improving system stability, and significantly reducing costs. Furthermore, the phase plate design offers great flexibility, enabling the customization of two-dimensional area array scanning light fields of arbitrary sizes, thus demonstrating strong applicability. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of a beam scanning dimension expansion device based on transformation optics according to an embodiment of the present invention.

[0025] Figure 2 This is another structural schematic diagram of a beam scanning dimension expansion device based on transformation optics according to an embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram of the first phase plate and the second phase plate being overlaid on a glass substrate according to an embodiment of the present invention.

[0027] Figure 4 This is a flowchart illustrating a method for expanding the scanning dimension of a beam based on transformation optics according to an embodiment of the present invention.

[0028] Figure 5This is a schematic diagram of the incident one-dimensional scanning point and the emitted two-dimensional scanning point array after optical transformation, according to an embodiment of the present invention. Detailed Implementation

[0029] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0030] like Figure 1 As shown, this embodiment of the invention provides a beam scanning dimension expansion device based on transformation optics, including a beam collimation module 1, a first phase plate 2, and a second phase plate 3 arranged sequentially along the optical path.

[0031] The working principle of the device is as follows:

[0032] A one-dimensional linear scanning beam is emitted by the beam collimation module 1 and then collimated and incident on the first phase plate 2. The first phase plate 2 performs optical field transformation on the one-dimensional linear scanning beam through the first phase modulation signal, transforming the one-dimensional linear scanning beam into a two-dimensional area array scanning beam.

[0033] Specifically, the first phase plate 2 transforms the optical field of the one-dimensional linear scanning beam into a two-dimensional area array scanning beam by applying a first phase modulation signal. This is achieved by uniformly segmenting the one-dimensional linear scanning beam on the first phase plate and then sequentially mapping the uniformly segmented optical field onto different heights of the second phase plate 3. That is, the mapped segmented optical fields have the same horizontal coordinate but different vertical coordinates. Through the phase modulation of the optical field on the first phase plate 2, the one-dimensional linear scanning beam can be transformed into a two-dimensional area array scanning beam, thus expanding the scanning dimension of the beam.

[0034] The second phase plate 3 performs wave vector correction on the two-dimensional area array scanning beam by loading the second phase modulation signal, and emits the two-dimensional area array scanning beam in parallel.

[0035] Specifically, the second phase plate 3 performs wave vector correction on the two-dimensional area array scanning beam using a loaded second phase modulation signal. This is because, during the optical field mapping process, the optical field at different positions on the first phase plate 2 experiences different optical path lengths when propagating to the corresponding positions on the second phase plate 3, resulting in different wave vector directions at any point on the second phase plate 3, i.e., phase distortion exists in the optical field on the second phase plate 3. Therefore, the second phase plate 3 can compensate for this phase distortion of the optical field by loading the second phase modulation signal, adjusting the wave vector direction at any point on the second phase plate 3 to a direction parallel to the optical axis, and emitting the corrected two-dimensional area array scanning beam in parallel.

[0036] like Figure 2As shown, in a preferred embodiment, the beam collimation module 1 includes a laser module 11 and a cylindrical lens 12. The laser module 11 is used to emit a one-dimensional linear scanning beam, and the cylindrical lens 12 is used to collimate the one-dimensional linear scanning beam before it is incident on the first phase plate 2. By using the cylindrical lens 12, the light can be focused in one direction and not focused in another direction, thus ensuring that the one-dimensional linear scanning beam is incident perpendicularly on the first phase plate 2.

[0037] The plane of the cylindrical lens 12 is parallel to the plane of the first phase plate 2, which ensures that the collimated one-dimensional linear scanning beam is entirely incident on the first phase plate 2.

[0038] The first phase plate 2 and the second phase plate 3 are located on opposite sides of the glass substrate. The glass substrate can fix the two-dimensional area array scanning beam emitted from the first phase plate 2, ensuring that the entire two-dimensional area array scanning beam is incident on the second phase plate 3.

[0039] like Figure 3 As shown, in a preferred embodiment, the first phase plate 2 and the second phase plate 3 are etched onto a glass substrate. To make the device of the present invention more suitable for use in lidar beam scanning systems, this embodiment etches the two phase plates that achieve beam scanning dimension expansion onto a single glass substrate, enabling precise alignment of the two phase plates during manufacturing.

[0040] The first phase plate 2 and the second phase plate 3 are respectively a spatial light modulator, a diffractive optical element, and a metasurface. The spatial light modulator, diffractive optical element, or metasurface has the function of optical field phase modulation, which can expand the scanning dimension of the beam through optical field transformation.

[0041] The process of beam scanning dimension expansion in an embodiment of the present invention will be described in detail below.

[0042] This invention transforms a one-dimensional linear scanning beam into a two-dimensional area array scanning beam. The corresponding mapping relationship is expressed as follows:

[0043]

[0044] Where (x,y) represents the plane where the first phase plate 2 is located, and x and y represent the horizontal and vertical coordinates in (x,y) respectively; (u,v) represents the plane where the second phase plate 3 is located, and u and v represent the horizontal and vertical coordinates in (u,v) respectively; β represents the horizontal scaling factor of the segmented light field on the (x,y) plane after propagation to the (u,v) plane, usually β≥1; d1 represents the distance between the center of any segmented light field on the (x,y) plane and the y-axis; d2 represents the distance between any segmented light field on the (x,y) plane after it is mapped to the (u,v) plane and the u-axis.

[0045] The first phase modulation signal is expressed as follows:

[0046]

[0047] Where Q(x,y) represents the first phase modulation signal; k represents the wavenumber of the one-dimensional linear scanning beam, i.e., k = 2π / λ, where λ is the wavelength of the incident one-dimensional scanning beam; d represents the distance between the first phase plate 2 and the second phase plate 3; L represents the size of the transverse scanning area of ​​the one-dimensional linear scanning beam; N represents the number of segmented optical fields of the one-dimensional linear scanning beam, which is equal to the number of scanning rows of the two-dimensional scanning beam; and h represents the size of the longitudinal scanning area of ​​the two-dimensional area array scanning beam. The range of x is... The range of values ​​for y is D is the diameter of the incident one-dimensional linear scanning beam. The first phase plate 2 transforms the one-dimensional linear scanning beam into a two-dimensional area array scanning beam by applying a first phase modulation signal, thus expanding the scanning dimension of the beam. By changing the parameters β, N, L, and h, the phase distribution of the first phase plate 2 can be altered, thereby producing output scanning light fields with different parameters. In other words, by modifying the parameters β, N, L, and h, the customization of a two-dimensional area array scanning light field of arbitrary size can be achieved.

[0048] The second phase modulation signal is expressed as follows:

[0049]

[0050] Where P(u,v) represents the second phase modulation signal. The range of values ​​for u is... The range of values ​​for v is The second phase plate 3 performs wave vector correction on the two-dimensional array scanning beam by loading the second phase modulation signal, which can compensate for the phase distortion of the light field incident on the second phase plate 3 and output the segmented light field in parallel.

[0051] Based on the above-described apparatus embodiments, the present invention provides corresponding method embodiments.

[0052] like Figure 4 As shown, this embodiment of the invention also provides a method for beam scanning dimension expansion using the beam scanning dimension expansion device as described in any of the above claims, comprising the following steps:

[0053] S1. The beam collimation module 1 emits a one-dimensional linear scanning beam, which is collimated and then incident on the first phase plate 2.

[0054] S2. A preset first phase modulation signal is loaded on the first phase plate 2. The light field of the one-dimensional linear scanning beam is transformed by the first phase modulation signal, and the one-dimensional linear scanning beam is transformed into a two-dimensional area array scanning beam.

[0055] S3. A preset second phase modulation signal is loaded onto the second phase plate 3. The wave vector of the two-dimensional area array scanning beam is corrected by the second phase modulation signal, and the corrected two-dimensional area array scanning beam is emitted in parallel.

[0056] By implementing the above-described method embodiments of the present invention, the scanning dimension of the beam can be expanded, and a two-dimensional area array scanning light field of any size can also be customized.

[0057] Specifically, the steps for transforming a one-dimensional linear scanning beam into a two-dimensional area array scanning beam include:

[0058] The first phase plate 2 uniformly segments the one-dimensional linear scanning beam, and then sequentially maps the uniformly segmented light field onto different heights of the second phase plate 3. That is, the mapped segmented light fields have the same horizontal coordinate but different vertical coordinates; see [reference needed] for details. Figure 5 By uniformly segmenting a one-dimensional linear scanning beam, a single line of light field can be transformed into multiple lines, thus expanding the scanning dimension of the beam.

[0059] In summary, the embodiments of the present invention provide a beam scanning dimension expansion device and method based on transformation optics. When applied to a lidar beam scanning system, this device simplifies a two-dimensional beam deflector to a one-dimensional deflector, greatly optimizing the structure of the lidar beam scanning system, improving system stability, and significantly reducing costs. Furthermore, the phase plate design offers great flexibility, enabling the customization of two-dimensional area array scanning light fields of arbitrary sizes, demonstrating strong applicability.

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A beam scanning dimension expansion device based on transformation optics, characterized in that, The system includes a beam collimation module, a first phase plate, and a second phase plate arranged sequentially along the optical path. The beam collimation module emits a one-dimensional linear scanning beam, which is then collimated and incident on the first phase plate. The first phase plate performs optical field transformation on the one-dimensional linear scanning beam using a first phase modulation signal, transforming the one-dimensional linear scanning beam into a two-dimensional area array scanning beam. The second phase plate performs wave vector correction on the two-dimensional area array scanning beam using a second phase modulation signal, ensuring the two-dimensional area array scanning beam exits in parallel. The first phase modulation signal is specifically expressed as follows: Where (x,y) represents the plane where the first phase plate is located, x and y represent the horizontal and vertical coordinates in (x,y) respectively, and Q(x,y) represents the first phase modulation signal. denoted by , k represents the lateral scaling factor after the segmented light field on the first phase plate plane propagates to the second phase plate plane, d represents the distance between the first and second phase plates, L represents the size of the lateral scanning area of ​​the one-dimensional linear scanning beam, N represents the number of segmented light fields of the one-dimensional linear scanning beam, and h represents the size of the longitudinal scanning area of ​​the two-dimensional area array scanning beam. The second phase modulation signal is specifically expressed as follows: Where (u,v) represents the plane where the second phase plate is located, u and v represent the horizontal and vertical coordinates in (u,v) respectively, and P(u,v) represents the second phase modulation signal.

2. The beam scanning dimension expansion device according to claim 1, characterized in that, The beam collimation module includes a laser module and a cylindrical lens.

3. The beam scanning dimension expansion device according to claim 2, characterized in that, The plane of the cylindrical lens is parallel to the plane of the first phase plate.

4. The beam scanning dimension expansion device according to claim 1, characterized in that, The first phase plate and the second phase plate are located on opposite sides of the glass substrate.

5. The beam scanning dimension expansion device according to claim 4, characterized in that, The first phase plate and the second phase plate are etched onto the glass substrate.

6. The beam scanning dimension expansion device according to claim 5, characterized in that, The first phase plate and the second phase plate are respectively a spatial light modulator, a diffractive optical element, and a metasurface.

7. A method for beam scanning dimension expansion using the beam scanning dimension expansion device as described in any one of claims 1 to 6, characterized in that, include: The beam collimation module emits a one-dimensional linear scanning beam, which is collimated and then incident on the first phase plate; A preset first phase modulation signal is loaded on the first phase plate, and the light field of the one-dimensional linear scanning beam is transformed by the first phase modulation signal, thereby transforming the one-dimensional linear scanning beam into a two-dimensional area array scanning beam. A preset second phase modulation signal is loaded on the second phase plate, and the wave vector of the two-dimensional area array scanning beam is corrected by the second phase modulation signal, and the corrected two-dimensional area array scanning beam is emitted in parallel.

8. The beam scanning dimension expansion method according to claim 7, characterized in that, The step of transforming the one-dimensional linear scanning beam into a two-dimensional area array scanning beam includes: The first phase plate divides the one-dimensional linear scanning beam into uniform segments, and then maps the uniformly segmented light field sequentially to different heights of the second phase plate.

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