Radar scanning device and method based on cascaded double-phase plate

Abstract

The invention discloses a radar scanning device and method based on cascaded double-phase plates. The device comprises a laser generator, a first phase plate and a second phase plate, the light output end of the laser generator is aligned with the first phase plate, and the laser generator is used for generating a light initial signal; a first phase distribution is etched on one surface, far away from the laser generator, of the first phase plate, and the first phase plate is used for performing primary modulation processing on a received optical initial signal to obtain a first optical signal; a second phase distribution is etched on one surface, facing the first phase plate, of the second phase plate, and the second phase plate is used for performing secondary modulation processing on the received first optical signal to obtain a two-dimensional grating scanning light beam; wherein the first phase distribution and the second phase distribution are designed to generate corresponding two-dimensional grating scanning beams according to the phase difference between the first phase distribution and the second phase distribution, so that the flexibility and the stability of the laser radar scanning system are enhanced.

Description

Technical Field

[0001] The present invention relates to the field of laser radar technology, and in particular to a radar scanning device and method based on a cascaded dual-phase plate. Background Art

[0002] With the rapid development of driverless technology, the demand for smaller, lower energy-consuming and more stable on-board LiDARs is becoming increasingly urgent. Among the core technologies of LiDARs, the beam scanning device is particularly critical. Its performance directly affects the imaging resolution of LiDARs, and thus becomes an important factor in ensuring the safety of autonomous driving. In order to achieve three-dimensional real-time imaging of the road environment during driving, the beam scanning device generates a two-dimensional array scanning light field and emits a scanning laser beam to the target object to reconstruct a three-dimensional image of the road environment.

[0003] The existing laser radar usually achieves two-dimensional scanning by controlling the one-dimensional beam deflection in the x-direction and the y-direction separately, and achieves beam scanning through the combination of the deflection in the x-direction and the y-direction. However, this method requires the structure of the beam scanning system to become very complex, large in size and high in optical component cost. At the same time, the stability and reliability of the system are limited, which is not conducive to the application in vehicle-mounted laser radar.

[0004] It can be seen that how to optimize the structural design of the radar scanning device to achieve two-dimensional scanning has become a technical problem that needs to be urgently solved by those skilled in the art. Summary of the invention

[0005] The present invention provides a radar scanning device and method based on a cascaded dual-phase plate, so as to improve the structure of the radar scanning device and enhance the stability of the system.

[0006] In order to solve the above technical problems, an embodiment of the present invention provides a radar scanning device based on a cascaded dual-phase plate, comprising:

[0007] A laser generator, a first phase plate, and a second phase plate;

[0008] The laser generator has an optical output end aligned with the first phase plate, and the laser generator is used to generate an optical initial signal;

[0009] The first phase plate has a first phase distribution etched on a side away from the laser generator, and the first phase plate is used to perform a primary modulation process on the received initial optical signal to obtain a first optical signal;

[0010] The second phase plate has a second phase distribution etched on a surface facing the first phase plate, and the second phase plate is used to perform secondary modulation processing on the received first optical signal to obtain a two-dimensional grating scanning light beam; wherein the first phase distribution and the second phase distribution are designed to generate a corresponding two-dimensional grating scanning light beam according to the phase difference between the two.

[0011] Furthermore, the planes of the first phase plate and the second phase plate are arranged parallel to each other along the optical axis.

[0012] Furthermore, the first phase plate and the second phase plate are respectively overlaid on corresponding glass substrates.

[0013] Furthermore, the first phase plate is manufactured by etching the first phase distribution on the back side of the first glass substrate, and the second phase plate is manufactured by etching the second phase distribution on the front side of the second glass substrate.

[0014] Further, the first phase plate and the second phase plate are designed to be in a disk shape.

[0015] Furthermore, the first phase plate and the second phase plate are respectively designed as one of a spatial light modulator, a diffractive optical element and a metasurface.

[0016] Furthermore, the phase distribution of the first phase plate is expressed by the following formula:

[0017]

[0018] Among them, (x1, y1) represents the plane where the first phase plate is located, x1 and y1 represent the horizontal and vertical coordinate values ​​in the (x1, y1) plane respectively; Φ1(x1, y1) represents the first phase distribution in the rectangular coordinate system, λ represents the working wavelength of the phase plate; a and b represent the coefficients that determine the horizontal and vertical fields of view of the grating scanning respectively; L and H represent the length and width of the first phase distribution respectively.

[0019] Furthermore, the phase distribution of the second phase plate is expressed by the following formula:

[0020]

[0021] Among them, (x2, y2) represents the plane where the second phase plate is located, x2 and y2 represent the horizontal and vertical coordinate values ​​in the (x2, y2) plane respectively; Φ2(x2, y2) represents the second phase distribution in the rectangular coordinate system, which is obtained by horizontally splicing N sub-phases; h represents a constant; L and H represent the length and width of the second phase distribution respectively.

[0022] Another embodiment of the present invention provides a radar scanning method based on a cascaded dual-phase plate, comprising:

[0023] transmitting the optical initial signal to the first phase plate through the laser generator;

[0024] The first phase plate receives the optical initial signal, performs reference phase modulation on the optical initial signal, and then transmits the signal to the second phase plate;

[0025] The second phase plate performs rotation phase modulation on the optical initial signal after reference phase modulation and then emits it to realize two-dimensional grating scanning.

[0026] Furthermore, two-dimensional grating scanning at any frame rate is performed by adjusting the rotation speed of the second phase plate.

[0027] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0028] The device provided by the present invention can be applied to the laser radar beam scanning system. By designing two phase plates (fixed plate and rotating plate) etched with different phase distributions, the structure of the laser radar beam scanning system is optimized, the stability of the system is improved, and the cost is significantly reduced. And by adjusting the rotation speed of the rotating plate, two-dimensional grating scanning with any frame rate can be obtained, which has strong flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic structural diagram of a radar scanning device based on a cascaded dual-phase plate in one embodiment of the present invention;

[0030] Figure 2 is a schematic diagram of a first phase distribution and a second phase distribution in a rectangular coordinate system in one embodiment of the present invention;

[0031] Figure 3 is a schematic diagram of the phase distribution of a disk in which a first phase plate and a second phase plate are engraved on a glass substrate in one embodiment of the present invention;

[0032] Figure 4 is a schematic diagram of an N-line scanning dot matrix generated in one embodiment of the present invention;

[0033] Figure 5 It is a schematic flow chart of a radar scanning method based on a cascaded dual-phase plate in one embodiment of the present invention;

[0034] Reference numerals:

[0035] Among them, 1. first phase plate; 11. first phase distribution in rectangular coordinate system; 12. first disk phase distribution; 2. second phase plate; 21. second phase distribution in rectangular coordinate system; 22. second disk phase distribution; 3. laser generator. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In the description of this application, the terms "first", "second", "third", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", "third", etc. may explicitly or implicitly include one or more of the feature. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0038] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be a connection between the two elements. The terms "vertical", "horizontal", "left", "right", "upper", "lower" and similar expressions used herein are only for illustrative purposes, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0039] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0040] Based on the problems of the existing beam scanning system with complex structure, large volume, high manufacturing cost, and low stability and reliability, an embodiment of the present invention provides a radar scanning device based on a cascaded dual-phase plate. For details, see Figure 1 , Figure 1FIG. 1 is a schematic diagram of a radar scanning device based on a cascaded dual-phase plate in one embodiment of the present invention, wherein the device comprises:

[0041] A laser generator 3, and a first phase plate 1 and a second phase plate 2 respectively etched with different phase distributions.

[0042] from Figure 1 It can be seen that the optical output end of the laser generator 3 is aligned with the first phase plate 1 to generate an optical initial signal, that is, an incident laser.

[0043] The first phase plate 1 has a first phase distribution etched on a surface thereof away from the laser generator 3 , and the first phase plate 1 is used to perform primary modulation processing on the received initial optical signal to obtain a first optical signal.

[0044] The second phase plate 2 has a second phase distribution etched on a surface facing the first phase plate 1, and the second phase plate 2 is used to perform secondary modulation processing on the received first optical signal to obtain a two-dimensional grating scanning light beam. The first phase distribution and the second phase distribution are designed to generate a corresponding two-dimensional grating scanning light beam according to the phase difference between the two.

[0045] It can be understood that the process of implementing grating scanning using the above device is as follows: using the laser generator 3, a one-dimensional light beam is emitted and incident on the first phase plate 1 and the second phase plate 2. The first phase plate 1 and the second phase plate 2 convert the one-dimensional light beam into a two-dimensional grating scanning light beam by superimposing and modulating the phase and then emitting it. It is worth noting that the incident laser emitted by the laser generator 3 should be vertically incident on the first phase plate 1.

[0046] In this embodiment, the first phase plate 1 is fixed to provide a reference phase, and the second phase plate 2 rotates along the optical axis to provide a variable phase. It can be understood that the device of this embodiment actually uses the total phase after the two phase plates are superimposed to deflect the incident laser, so that the laser after passing through the first and second phase plates forms a dynamic grating scan in space.

[0047] from Figure 1 It can be seen that both phase plates are designed to be disc-shaped with a gap between them, and the planes of the first phase plate 1 and the second phase plate 2 are arranged parallel to each other along the optical axis shown in the figure.

[0048] In some implementations of this embodiment, in order to fully exert the beam deflection effect, the interval between the two phase plates should be as small as possible. Preferably, the interval d can be set to 1 mm.

[0049] In some implementations of this embodiment, the first phase plate 1 and the second phase plate 2 are respectively overlaid on corresponding glass substrates, that is, the two phase plates are respectively located on the back and front sides of the two glass substrates.

[0050] In this embodiment, the two phase plates are designed as one of a diffractive optical element, a molded element, and a metasurface device. The diffractive optical element, the molded element, and the metasurface device have a light field phase control function and can realize two-dimensional grating scanning by laser wavefront phase control.

[0051] In order to enable the device to achieve two-dimensional grating scanning, the device of this embodiment etches two phase plates with different phase distributions respectively, so that the two phase plates have a phase difference.

[0052] In this embodiment, the first phase plate 1 is made by etching a first phase distribution on the back side of a first glass substrate, and the second phase plate 2 is made by etching a second phase distribution on the front side of a second glass substrate, thereby achieving precise control of the laser beam and expansion of the scanning dimension.

[0053] The following is a detailed description of the design process of the phase distribution of the two phase plates in the embodiment of the present invention. For details, please refer to Figure 2 As shown, Figure 2 It is a schematic diagram of the first phase distribution and the second phase distribution in a rectangular coordinate system in one embodiment of the present invention, and it can be seen that:

[0054] The first phase plate 1 of this embodiment performs initial phase modulation on the incident laser emitted by the laser generator 3, and the first phase distribution 11 of the first phase plate 1 is expressed by the following formula:

[0055]

[0056] Among them, (x1, y1) represents the plane where the first phase plate is located, x1 and y1 represent the horizontal and vertical coordinate values ​​in the (x1, y1) plane respectively; Φ1(x1, y1) represents the first phase distribution in the rectangular coordinate system, λ represents the working wavelength of the phase plate; a and b represent the coefficients that determine the horizontal and vertical fields of view of the grating scanning respectively; L and H represent the length and width of the first phase distribution respectively.

[0057] The second phase plate 2 of this embodiment is modulated again by the laser after the initial phase modulation, and the second phase distribution 21 of the second phase plate 2 is expressed by the following formula:

[0058]

[0059] Among them, (x2, y2) represents the plane where the second phase plate is located, x2 and y2 represent the horizontal and vertical coordinate values ​​in the (x2, y2) plane respectively; Φ2(x2, y2) represents the second phase distribution in the rectangular coordinate system, which is obtained by horizontally splicing N sub-phases; h represents a constant; L and H represent the length and width of the second phase distribution respectively.

[0060] It can be understood that the second phase distribution in the rectangular coordinate system is obtained by horizontally splicing N sub-phases, the size of each sub-phase is equal to the size of the first phase distribution, and the phase distribution of each sub-phase is

[0061]

[0062] It can be seen from the above formula that the formula derivation process is the phase distribution of the two phase plates in the rectangular coordinate system. Therefore, in this embodiment, the phase distribution of the first and second phase plates are respectively converted into the phase distribution in the polar coordinate system. For details, please refer to Figure 3 , Figure 3 The diagram shows a disk phase distribution diagram of a first phase plate and a second phase plate engraved on a glass substrate in one embodiment of the present invention.

[0063] It can be understood that in this embodiment, the first phase distribution in the rectangular coordinate system is mapped through polar coordinates: And Φ1(x1,y1) is converted into the first disk phase distribution 12 in the polar coordinate system, which is specifically expressed by the following formula:

[0064]

[0065] Among them, (ρ1, θ1) represents the polar coordinate system, ρ1 and θ1 represent the radial coordinate value and angular coordinate value of the polar coordinate system respectively, and Ψ1(ρ1, θ1) represents the phase distribution of the first disk.

[0066] Similarly, the second phase distribution in the rectangular coordinate system is mapped through polar coordinates: Φ2(x2,y2) is converted into the second disk phase distribution 22 in the polar coordinate system, which is specifically expressed by the following formula:

[0067]

[0068] Among them, (ρ2,θ2) represents the polar coordinate system, ρ2 and θ2 represent the radial coordinate value and angular coordinate value of the polar coordinate system respectively; Ψ2(ρ2,θ2) represents the phase distribution of the second disk; the constant ρ0 determines the longitudinal interval between any two rows of the scanning light field.

[0069] Based on this, during the modulation process, the phases of the first phase plate 1 and the second phase plate 2 are subtracted, and a real-time changing phase slope can be generated at the laser incident point, that is, the phase slope changes with the rotation of the second phase plate 2. Specifically,

[0070] The phase difference ψ between the first disk phase distribution Ψ1 (ρ1, θ1) and the second disk phase distribution Ψ2 (ρ2, θ2) in the polar coordinate system controls the incident laser to achieve two-dimensional deflection of the laser. Since the first phase plate is fixed and the second phase plate is rotated by Δθ along the optical axis, the specific expression of the second disk phase distribution after rotation is as follows:

[0071]

[0072] The phase difference ψ generated by the superposition of two circular phase plates will change with the change of the rotation angle Δθ. By unifying the coordinate variables and noting ρ1=ρ2=ρ, θ1=θ2=θ, the specific expression of the superposition phase difference ψ is as follows:

[0073]

[0074] The phase slope of the superimposed phase difference ψ is the essential reason for realizing two-dimensional beam scanning. and radial The specific expression of the phase slope is as follows:

[0075]

[0076] in, and is the unit basis vector of the polar coordinate system.

[0077] The above formula shows that the tangential phase slope It is proportional to the rotation angle Δθ of the rotating phase plate. Therefore, as the rotating phase plate rotates, the laser scans in the tangential (or horizontal) direction. The radial phase slope at the laser incident point is is N discrete values, which means that the radial phase slope controls the laser to achieve line scanning in the radial (or vertical) direction, generating N line scans. For details, please refer to Figure 4 , Figure 4 FIG. 1 is a schematic diagram of an N-line scanning dot matrix generated in one embodiment of the present invention. As an example, Figure 4 As shown, it shows the scanning dot pattern when N=8 and 20.

[0078] In summary, the above device provided by the embodiment of the present invention can be applied to the laser radar beam scanning system, and the deflection modulation of the incident light is performed by cascading the dual phase plates, and the design of one static and one dynamic greatly optimizes the structure of the laser radar beam scanning system; and through the high-speed rotation of the phase plate, grating scanning of any number of lines and field of view can be achieved. This device can efficiently and conveniently convert a one-dimensional incident light beam into a two-dimensional grating, significantly reducing costs while improving the stability of the system.

[0079] Based on the above device embodiment, an embodiment of the present invention provides a radar scanning method based on a cascaded dual-phase plate. For details, see Figure 5 , Figure 5 The figure shows a flow chart of a radar scanning method for a cascaded dual-phase plate in one embodiment of the present invention, comprising the following steps:

[0080] S1. Transmitting the optical initial signal to the first phase plate through the laser generator.

[0081] S2. The first phase plate receives the optical initial signal, performs reference phase modulation on the optical initial signal, and then transmits the signal to the second phase plate.

[0082] S3. The second phase plate performs rotational phase modulation on the optical initial signal after reference phase modulation and then emits the signal to achieve two-dimensional grating scanning.

[0083] In this embodiment, the second phase plate is rotatable, provides a phase change, and rotates at a high speed along the optical axis.

[0084] Based on this, it can be understood that the frame rate of the two-dimensional grating scan is equal to the rotation rate of the rotating phase plate, and grating scans of any frame rate can be obtained by adjusting the rotation speed of the rotating plate, which has strong flexibility.

[0085] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A radar scanning device based on a cascaded dual-phase plate, characterized in that: The device includes a laser generator, a first phase plate and a second phase plate; The laser generator has an optical output end aligned with the first phase plate, and the laser generator is used to generate an optical initial signal; The first phase plate has a first phase distribution etched on a side away from the laser generator, and the first phase plate is used to perform a primary modulation process on the received initial optical signal to obtain a first optical signal; The second phase plate has a second phase distribution etched on a surface facing the first phase plate, and the second phase plate is used to perform secondary modulation processing on the received first optical signal to obtain a two-dimensional grating scanning light beam; wherein the first phase distribution and the second phase distribution are designed to generate a corresponding two-dimensional grating scanning light beam according to the phase difference between the two.

2. The radar scanning device based on the cascaded dual-phase plate according to claim 1, characterized in that: The planes of the first phase plate and the second phase plate are arranged parallel to each other along the optical axis.

3. The radar scanning device based on the cascaded dual-phase plate according to claim 1, characterized in that: The first phase plate and the second phase plate are respectively overlaid on corresponding glass substrates.

4. The radar scanning device based on the cascaded dual-phase plate according to claim 1, characterized in that: The first phase plate is manufactured by etching the first phase distribution on the back side of a first glass substrate, and the second phase plate is manufactured by etching the second phase distribution on the front side of a second glass substrate.

5. The radar scanning device based on the cascaded dual-phase plate according to claim 1, characterized in that: The first phase plate and the second phase plate are designed in a disk shape.

6. The radar scanning device based on the cascaded dual-phase plate according to claim 1, characterized in that: The first phase plate and the second phase plate are respectively designed as one of a spatial light modulator, a diffractive optical element and a metasurface.

7. The radar scanning device based on the cascaded dual-phase plate according to claim 1, characterized in that: The phase distribution of the first phase plate is expressed by the following formula: Among them, (x1, y1) represents the plane where the first phase plate is located, x1 and y1 represent the horizontal and vertical coordinate values ​​in the (x1, y1) plane respectively; Φ1(x1, y1) represents the first phase distribution in the rectangular coordinate system, λ represents the working wavelength of the phase plate; a and b represent the coefficients that determine the horizontal and vertical fields of view of the grating scanning respectively; L and H represent the length and width of the first phase distribution respectively.

8. The radar scanning device based on the cascaded dual-phase plate as claimed in claim 1, characterized in that: The phase distribution of the second phase plate is expressed by the following formula: Among them, (x2, y2) represents the plane where the second phase plate is located, x2 and y2 represent the horizontal and vertical coordinate values ​​in the (x2, y2) plane respectively; Φ2(x2, y2) represents the second phase distribution in the rectangular coordinate system, which is obtained by horizontally splicing N sub-phases; h represents a constant; L and H represent the length and width of the second phase distribution respectively.

9. A radar scanning method based on a cascaded dual-phase plate, applied to a radar scanning device based on a cascaded dual-phase plate as claimed in any one of claims 1 to 8, characterized in that: include: transmitting the optical initial signal to the first phase plate through the laser generator; The first phase plate receives the optical initial signal, performs reference phase modulation on the optical initial signal, and then transmits the signal to the second phase plate; The second phase plate performs rotation phase modulation on the optical initial signal after reference phase modulation and then emits it to realize two-dimensional grating scanning.

10. The radar scanning method based on cascaded dual-phase plates as claimed in claim 9, characterized in that: Two-dimensional grating scanning at any frame rate is performed by adjusting the rotation speed of the second phase plate.

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