Two-dimensional light beam scanning system and method based on double off-axis geometric phase lens group

Abstract

This invention discloses a two-dimensional beam scanning system and method based on a dual off-axis geometric phase lens group. Utilizing the principle of geometric phase, this invention designs an off-axis phase distribution on the lens surface, causing the pointing angle of the outgoing beam to deflect after the incident parallel beam passes through two independently rotating lenses at different speeds. The first lens focuses and deflects the incident circularly polarized light, resulting in orthogonally circularly polarized light. The second lens, through a specific phase conjugation design, continues to focus and deflect the orthogonally circularly polarized light using a positive lens. Through the independent differential rotation of the two off-axis positive lenses, high-speed two-dimensional scanning of various trajectories such as spirals, rose lines, and circles is achieved on the focal plane using the principle of vector synthesis. This invention employs a compact system and method with higher light energy utilization, and is free from the inertial limitations of mechanical galvanometers, making it particularly suitable for fields such as lidar, laser rotary cutting, and free-space optical communication.

Description

Technical Field

[0001] This invention relates to the field of optical scanning and laser application technology, and in particular to a two-dimensional beam scanning system and method based on a dual off-axis geometric phase lens group. Background Technology

[0002] Beam scanning is a core function of modern optical systems and is widely used in fields such as lidar, laser precision machining, and free-space optical communication. Existing mainstream implementation solutions have technical bottlenecks that are difficult to overcome and cannot meet the development needs of compact, high-speed, and multifunctional optical systems.

[0003] Mechanical galvanometers are inherently constrained by mechanical inertia, making it difficult to achieve ultra-high-speed stable scanning. Furthermore, their trajectory control is inflexible, making it impossible to efficiently generate high-fill-rate area scanning patterns. While dual-wedge systems can achieve wide-field scanning, the heavy glass prisms increase the motor load, and the refractive index-based beam deflection introduces dispersion, making them unsuitable for ultra-short pulse laser applications. Although traditional diffractive optical elements are thin and light, their diffraction efficiency is limited by photolithography processes, allowing them to achieve only static beam splitting and preventing continuous dynamic scanning.

[0004] While conventional geometric phase plane optical elements have the advantages of being ultra-thin and having flexible phase control, they are mostly limited to static focusing and beam splitting scenarios. Furthermore, due to the influence of spin-orbit interaction, the polarization direction of circularly polarized light is reversed after passing through the lens. Direct cascading can easily lead to system failure. The traditional solution of adding a half-wave plate will increase the system size, cost, and optical loss.

[0005] In summary, existing beam scanning technologies generally suffer from core problems such as large size, significant inertial limitations, limited scanning trajectory, and low light energy utilization. There is an urgent need to develop a new two-dimensional beam scanning system that is compact, has high-speed and flexible scanning capabilities, and high light energy utilization. Summary of the Invention

[0006] The purpose of this invention is to provide a two-dimensional beam scanning system and method based on a dual off-axis geometric phase lens group. Through the polarization-matched dual off-axis geometric phase lens cascade design, no additional polarization conversion element is required, realizing a compact structure and ultra-high-speed scanning without inertial constraints. It can flexibly generate multiple types of two-dimensional scanning trajectories, greatly improving light energy utilization and scene adaptability. It can be widely used in light scanning scenarios such as lidar, laser precision processing, laser medical treatment and holographic projection.

[0007] To achieve the above objectives, the present invention provides a two-dimensional beam scanning system based on a dual off-axis geometric phase lens group, comprising: The light source assembly is used to output the first spirally polarized laser beam; The first lens module is coaxially arranged along the main optical axis of the system on the light output path of the light source assembly, and includes a first geometric phase positive lens and a first hollow rotary motor. The second lens module is coaxially arranged on the light-emitting side of the first lens module along the main optical axis of the system, and includes a second geometric phase positive lens and a second hollow rotary motor. Both the first geometric phase positive lens and the second geometric phase positive lens are planar lenses with their phase centers off-axis. The phase distribution centers of both lenses are set at a preset off-axis distance relative to their own physical rotation centers, and the physical rotation centers of both lenses coincide with the main optical axis of the system. The first hollow rotary motor and the second hollow rotary motor independently drive the first geometric phase positive lens and the second geometric phase positive lens to rotate around the main optical axis of the system; The first geometric phase positive lens presents positive optical power for the first direction of circularly polarized light, and the second geometric phase positive lens presents positive optical power for the second direction of circularly polarized light that is opposite to the first direction of circularly polarized light.

[0008] Preferably, both the first geometric phase positive lens and the second geometric phase positive lens are composed of a substrate and an array of subwavelength structural units arranged on the substrate; The length, width, and height of the subwavelength structural unit are all subwavelength scales. The phase of the transmitted light is modulated by adjusting the rotation angle of the subwavelength structural unit in the plane, and the phase delay satisfies the formula: ; in, This represents the phase retardation of the transmitted light. It is the spin state of the incident circularly polarized light, and Corresponding to left-handed circularly polarized light LCP, Corresponding to right-hand circularly polarized light RCP, , The coordinates are two-dimensional rectangular coordinates within the lens plane. For the subwavelength structural unit in the lens plane coordinates The rotation angle at the corresponding position.

[0009] Preferably, the first geometric phase positive lens is designed with a focusing phase distribution for left-handed circularly polarized light, and the second geometric phase positive lens is designed with a focusing phase distribution for right-handed circularly polarized light; The phase distributions of the first geometric phase positive lens and the second geometric phase positive lens both satisfy the off-axis focusing formula, and under the same incident polarized light, the phase responses of the first geometric phase positive lens and the second geometric phase positive lens are conjugate to each other.

[0010] Preferably, the phase distributions of the first geometrical phase positive lens and the second geometrical phase positive lens satisfy the off-axis focusing formula as follows: ; in, The phase distribution of a geometrically phased positive lens. As the focus item, The linear phase gradient is equivalent to a wedge prism in physical optics, and it represents the deflection term. For the system's operating wavelength, This corresponds to the focal length of a geometrically phase positive lens. The preset off-axis distance between the lens phase distribution center and its own physical rotation center. A constant phase term; phase off-axis distance Corresponding beam deflection angle The deflection effect of the lens is equivalent to a deflection vector with a fixed modulus. .

[0011] Preferably, it also includes a controller and a high-precision encoder; the controller is electrically connected to the first hollow rotary motor, the second hollow rotary motor, and the high-precision encoder respectively; the high-precision encoder is used to collect the real-time rotation angle and speed signals of the first hollow rotary motor and the second hollow rotary motor and feed them back to the controller; the controller is used to output matching speed and phase control commands according to the feedback signals to form independent closed-loop PID control for the two hollow rotary motors respectively.

[0012] A two-dimensional beam scanning method based on a dual off-axis geometric phase lens group is also provided, applied to the aforementioned two-dimensional beam scanning system based on a dual off-axis geometric phase lens group, including the following steps: The controller is activated, and the absolute zero position of the first hollow rotary motor and the second hollow rotary motor is obtained in real time through a high-precision encoder. According to the preset target, the controller pre-drives the first hollow rotary motor and the second hollow rotary motor to rotate to the target mechanical angle, sets the initial phase difference between the two motors, and completes the initial phase calibration of the system. Turn on the light source assembly to output a stable continuous wave or pulsed laser beam; adjust the optical path front-end assembly to ensure that the beam incident on the first geometric phase positive lens is circularly polarized light with a single rotation direction; The controller receives the target scanning trajectory command and independently controls the rotational angular velocity of the first hollow rotary motor and the second hollow rotary motor in a closed loop. The beam is sequentially subjected to two-stage phase modulation through the first geometric phase positive lens and the second geometric phase positive lens to form a corresponding deflection vector. The two deflection vectors are vector synthesized at the focal plane to form a two-dimensional beam scanning trajectory that matches the target command. During the scanning process, the high-precision encoder feeds back the real-time angle signals of the two motors to the controller in real time. The controller then performs closed-loop PID control based on the feedback signals to maintain the motor speed and phase accuracy.

[0013] Preferably, the total deflection position of the beam in the focal plane satisfies the vector composition relationship: ; in, The rotational angular velocity of the first hollow rotary motor, The rotational angular velocity of the second hollow rotary motor. For the time variable of the scanning process, for The beam of light is in the focal plane at any given moment. The deflection position in the axial direction, for The beam of light is in the focal plane at any given moment. The deflection position in the axial direction, The initial phase difference between the first hollow rotary motor and the second hollow rotary motor; This is the magnitude of the deflection vector corresponding to the first geometric phase positive lens. The deflection vector magnitude corresponding to the second geometric phase positive lens; by adjusting the rotational angular velocity of the first hollow rotary motor. The rotational angular velocity of the second hollow rotary motor The initial phase difference between the first hollow rotary motor and the second hollow rotary motor Three parameters control the shape, size, and fill density of the scan trajectory.

[0014] Preferably, by adjusting the rotational angular velocity of the first hollow rotary motor Rotational angular velocity of the second hollow rotary motor The matching relationship generates two-dimensional scanning trajectories in the form of circles, straight lines, spirals, and petals / quadrifoglio. When generating a circular scan trajectory, control By adjusting the initial phase difference between the first hollow rotary motor and the second hollow rotary motor Adjust the scan radius to achieve a scan radius from its minimum value. To the maximum value The stepless continuous scaling, the scan radius satisfies: ; in, This is the deflection magnitude corresponding to the first geometric phase positive lens. This is the deflection magnitude value corresponding to the second geometric phase positive lens; When generating a straight-line scan trajectory, control and By adjusting the initial spatial phase of the first hollow rotary motor and the second hollow rotary motor , Adjust the azimuth and tilt angles of the scanning line until the azimuth and tilt angles meet the requirements. This enables 360° full-range linear scanning pointing control; among which, The reference rotational angular velocity in linear scan mode. The equivalent deflection vector magnitude of the two lenses. This represents the initial spatial phase of the first hollow rotating electric motor. This represents the initial spatial phase of the second hollow rotating electric motor. The azimuth and tilt angle of the scanning line; When generating the spiral scan trajectory, control and There are tiny differences Archimedean spirals are formed based on the beat frequency effect, and by adjusting... The size of the radial fill density of the scan trajectory is adjusted by adjusting the reference rotation speed. Adjust the scan frame rate; among which, This represents the difference in angular velocity between the two rotating motors. This is the reference rotational speed for helical scanning; When generating the petal-shaped rose line scan trajectory, control and For a ratio of coprime integers m:n, satisfying , ,in, The basic unit angular velocity is m and n, which are positive integers that are coprime. The number of petals in the scanning trajectory is adjusted by adjusting the value of the coprime integer ratio m:n. The overall rotation of the scanning pattern on the focal plane is achieved by adjusting the initial phase of the first hollow rotary motor and the second hollow rotary motor.

[0015] Preferably, during the scanning process, the angular velocity of the first hollow rotary motor and the initial phase difference of the second hollow rotary motor are adjusted in real time by the controller to achieve real-time switching between different scanning trajectories.

[0016] Therefore, the two-dimensional beam scanning system and method based on dual off-axis geometric phase lens groups described above have the following beneficial effects: (1) The polarization-matched dual off-axis geometric phase lens cascade architecture can achieve polarization adaptation without the need for additional optical components, simplifying the system structure and reducing optical path transmission loss.

[0017] (2) Relying on the deflection vector synthesis mechanism of independent rotation of dual lenses, the beam scanning trajectory can be flexibly adjusted, and the scanning mode can be switched without modifying the hardware, thus improving the scene adaptability.

[0018] (3) The planar optical element design avoids the inertial limitations of traditional mechanical scanning and the dispersion problem of refractive elements, thereby improving the scanning speed and the range of light source compatibility.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1This is a structural diagram of a two-dimensional beam scanning system based on a dual off-axis geometric phase lens group according to an embodiment of the present invention; Figure 2 This is a flowchart of a two-dimensional beam scanning method based on a dual off-axis geometric phase lens group according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the geometric phase modulation principle according to an embodiment of the present invention; Figure 4 The diagram shows the phase distribution (equivalent prism principle) of the off-axis lens according to an embodiment of the present invention: (a) Focusing phase term (b) Linear gradient term (prism) (c) Total phase of off-axis lens ; Figure 5 The following are schematic diagrams of scanning patterns according to embodiments of the present invention: (a) circular scan; (b) linear scan; (c) spiral scan; (d) petal scan (four-leaf); (e) dense scan; (f) extremely high density fill. Detailed Implementation

[0021] Example like Figure 1 As shown, this invention discloses a two-dimensional beam scanning system based on a dual off-axis geometric phase lens group, along the optical axis. The directions are distributed sequentially, including: The light source assembly is used to output the first spirally polarized laser beam (wavelength is...). Left-handed circularly polarized (LCP) laser); The first lens module is coaxially arranged along the main optical axis of the system on the light output path of the light source assembly, and includes a first geometric phase positive lens and a first hollow rotary motor; the second lens module is coaxially arranged along the main optical axis of the system on the light output side of the first lens module, and includes a second geometric phase positive lens and a second hollow rotary motor. It also includes a controller and a high-precision encoder; the controller is electrically connected to the first hollow rotary motor, the second hollow rotary motor and the high-precision encoder respectively. The high-precision encoder is used to collect the real-time rotation angle and speed signals of the first hollow rotary motor and the second hollow rotary motor and feed them back to the controller. The controller is used to output matching speed and phase control commands according to the feedback signals to form independent closed-loop PID control for the two hollow rotary motors respectively.

[0022] Both the first geometric phase positive lens and the second geometric phase positive lens are planar lenses with their phase centers off-axis. The phase distribution centers of both lenses are set at a preset off-axis distance relative to their own physical rotation centers, and the physical rotation centers of both lenses coincide with the main optical axis of the system.

[0023] The off-axis distance of the phase center of the first lens module is: ,focal length Driven by the first hollow rotary motor M1. The phase center off-axis distance of the second lens module is... ,focal length Driven by a second hollow rotary motor M2, the lens is designed to focus right-hand circularly polarized (RCP) light.

[0024] Both the first geometric phase positive lens and the second geometric phase positive lens are composed of a substrate and an array of subwavelength structural units arranged on the substrate. like Figure 3 As shown, the length, width, and height of the subwavelength structural unit are all subwavelength scales. The phase of the transmitted light is modulated by adjusting the rotation angle of the subwavelength structural unit in the plane, and the phase delay satisfies the formula: ; in, This represents the phase retardation of the transmitted light. It is the spin state of the incident circularly polarized light, and Corresponding to left-handed circularly polarized light LCP, Corresponding to right-hand circularly polarized light RCP, , The coordinates are two-dimensional rectangular coordinates within the lens plane. For the subwavelength structural unit in the lens plane coordinates The rotation angle at the corresponding position.

[0025] The first geometric phase positive lens is designed to focus the phase distribution for left-hand circularly polarized light, and the second geometric phase positive lens is designed to focus the phase distribution for right-hand circularly polarized light. The phase distributions of the first geometric phase positive lens and the second geometric phase positive lens both satisfy the off-axis focusing formula, and under the same incident polarized light, the phase responses of the first geometric phase positive lens and the second geometric phase positive lens are conjugate to each other.

[0026] The core of this system is to solve the polarization problem by using two lenses with differentiated designs.

[0027] Geometric phase principle: The phase delay introduced by the rotation angle of the subwavelength structure is related to the spin state of the incident circularly polarized light; The first lens is designed with a structural angular distribution for the incident LCP to generate a focusing phase, and the polarization state of the beam is reversed to RCP after passing through it. The second lens is designed with a structural rotation angle for the incident RCP. In order to make the focusing phase positive, the structural rotation angle distribution is the opposite of that of the first lens (conjugate). The second lens micro-nano structure is the conjugate image of the first lens, with the opposite rotation direction. It can directly converge the RCP light emitted from the first lens without the need for intermediate conversion elements, thus achieving the superposition of two levels of positive optical power.

[0028] like Figure 4 As shown, the phase distributions of the first and second geometrical phase positive lenses satisfy the off-axis focusing formula: ; in, The phase distribution of a geometrically phased positive lens. As the focus item, The linear phase gradient is equivalent to a wedge prism in physical optics, and it represents the deflection term. For the system's operating wavelength, This corresponds to the focal length of a geometrically phase positive lens. The preset off-axis distance between the lens phase distribution center and its own physical rotation center. A constant phase term; phase off-axis distance Corresponding beam deflection angle The deflection effect of the lens is equivalent to a deflection vector with a fixed modulus. .

[0029] The phase distribution of the geometric phase lens is designed as an off-axis focusing function, and the deflection term is a linear phase gradient, which is equivalent to a wedge prism. In addition to focusing, each off-axis lens also causes the beam to produce a fixed deflection angle, and this deflection effect is defined as the deflection vector.

[0030] The first hollow rotary motor and the second hollow rotary motor independently drive the first geometric phase positive lens and the second geometric phase positive lens to rotate around the main optical axis of the system; The first geometric phase positive lens presents positive optical power for the first direction of circularly polarized light, and the second geometric phase positive lens presents positive optical power for the second direction of circularly polarized light that is opposite to the first direction of circularly polarized light.

[0031] A two-dimensional beam scanning method based on a dual off-axis geometric phase lens group is also disclosed, such as... Figure 2 As shown, the two-dimensional beam scanning system applied to the above-mentioned dual off-axis geometric phase lens group includes the following steps: The controller is activated, and the absolute zero position of the first hollow rotary motor and the second hollow rotary motor is obtained in real time through a high-precision encoder. According to the preset target, the controller pre-drives the first hollow rotary motor and the second hollow rotary motor to rotate to the target mechanical angle, sets the initial phase difference between the two motors, and completes the initial phase calibration of the system. Turn on the light source assembly to output a stable continuous wave or pulsed laser beam; adjust the optical path front-end assembly to ensure that the beam incident on the first geometric phase positive lens is circularly polarized light with a single rotation direction; The controller receives the target scanning trajectory command and independently controls the rotational angular velocity of the first and second hollow rotary motors in a closed loop; the beam undergoes two-stage phase modulation through the first and second geometrical phase positive lenses to form a corresponding deflection vector; the total deflection position of the beam on the focal plane satisfies the vector composition relationship: ; in, The rotational angular velocity of the first hollow rotary motor, The rotational angular velocity of the second hollow rotary motor. For the time variable of the scanning process, for The beam of light is in the focal plane at any given moment. The deflection position in the axial direction, for The beam of light is in the focal plane at any given moment. The deflection position in the axial direction, The initial phase difference between the first hollow rotary motor and the second hollow rotary motor; This is the magnitude of the deflection vector corresponding to the first geometric phase positive lens. The deflection vector magnitude corresponding to the second geometric phase positive lens; by adjusting the rotational angular velocity of the first hollow rotary motor. The rotational angular velocity of the second hollow rotary motor The initial phase difference between the first hollow rotary motor and the second hollow rotary motor Three parameters control the shape, size, and fill density of the scan trajectory.

[0032] The core of this system's two-dimensional scanning capability lies in vector synthesis. By adjusting the starting phase relationship between the two motors through a controller, the synthesized amplitude of the scanning trajectory can be continuously adjusted without changing the lens structure; independent adjustment is also possible. , It can achieve circular, straight line, spiral, and petal / quadrifoglio scanning modes.

[0033] The two deflection vectors are combined at the focal plane to form a two-dimensional beam scanning trajectory that matches the target command. During the scanning process, the high-precision encoder feeds back the real-time angle signals of the two motors to the controller in real time. The controller performs closed-loop PID control based on the feedback signal to maintain the motor speed and phase accuracy.

[0034] like Figure 5 As shown, by adjusting the rotational angular velocity of the first hollow rotary motor Rotational angular velocity of the second hollow rotary motor The matching relationship generates two-dimensional scanning trajectories in the form of circles, straight lines, spirals, and petals / quadrifoglio. like Figure 5As shown in (a), when generating a circular scan trajectory, control By adjusting the initial phase difference between the first hollow rotary motor and the second hollow rotary motor Adjust the scan radius to achieve a scan radius from its minimum value. To the maximum value The stepless continuous scaling, the scan radius satisfies: ; in, This is the deflection magnitude corresponding to the first geometric phase positive lens. This is the deflection magnitude value corresponding to the second geometric phase positive lens; like Figure 5 As shown in (b), when generating a straight-line scan trajectory, control... and By adjusting the initial spatial phase of the first hollow rotary motor and the second hollow rotary motor , Adjust the azimuth and tilt angles of the scanning line until the azimuth and tilt angles meet the requirements. This enables 360° full-range linear scanning pointing control; among which, The reference rotational angular velocity in linear scan mode. The equivalent deflection vector magnitude of the two lenses. This represents the initial spatial phase of the first hollow rotating electric motor. This represents the initial spatial phase of the second hollow rotating electric motor. The azimuth and tilt angle of the scanning line; like Figure 5 As shown in (c), when generating the helical scan trajectory, control and There are tiny differences Archimedean spirals are formed based on the beat frequency effect, and by adjusting... The size of the radial fill density of the scan trajectory is adjusted by adjusting the reference rotation speed. Adjust the scan frame rate; among which, This represents the difference in angular velocity between the two rotating motors. This is the reference rotational speed for helical scanning; like Figure 5 As shown in (d), when generating the petal / quadrifoglio-shaped scanning trajectory, control... and For a ratio of coprime integers m:n, satisfying , ,in, The basic unit angular velocity is m and n, which are positive integers that are coprime. The number of petals in the scanning trajectory is adjusted by adjusting the value of the coprime integer ratio m:n. The overall rotation of the scanning pattern on the focal plane is achieved by adjusting the initial phase of the first hollow rotary motor and the second hollow rotary motor.

[0035] like Figure 5 (e) in Figure 5 As shown in (f), by adjusting the rotation speed difference and the initial phase, dense scanning and ultra-high density filling scanning can be achieved to meet the needs of different application scenarios.

[0036] During the scanning process, the angular velocity and initial phase difference of the first and second hollow rotary motors are adjusted in real time by the controller to achieve real-time switching between different scanning trajectories.

[0037] Therefore, this invention employs the aforementioned two-dimensional beam scanning system and method based on dual off-axis geometric phase lens groups, effectively solving the core pain points of existing beam scanning technologies, such as large size, strong mechanical inertia constraints, high optical path loss, and insufficient scanning trajectory flexibility. This invention achieves coordinated control of polarization adaptation and beam deflection with a minimalist dual-lens cascade architecture, combining the technical advantages of planarization, low loss, high-speed controllability, and multi-mode scanning. It provides a high-performance beam scanning solution for fields such as lidar, laser precision machining, and free-space optical communication, possessing significant technical advantages and broad industrial application prospects.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A two-dimensional beam scanning system based on a dual off-axis geometric phase lens group, characterized in that, include: The light source assembly is used to output the first spirally polarized laser beam; The first lens module is coaxially arranged along the main optical axis of the system on the light output path of the light source assembly, and includes a first geometric phase positive lens and a first hollow rotary motor. The second lens module is coaxially arranged on the light-emitting side of the first lens module along the main optical axis of the system, and includes a second geometric phase positive lens and a second hollow rotary motor. Both the first geometric phase positive lens and the second geometric phase positive lens are planar lenses with their phase centers off-axis. The phase distribution centers of both lenses are set at a preset off-axis distance relative to their own physical rotation centers, and the physical rotation centers of both lenses coincide with the main optical axis of the system. The first hollow rotary motor and the second hollow rotary motor independently drive the first geometric phase positive lens and the second geometric phase positive lens to rotate around the main optical axis of the system; The first geometric phase positive lens presents positive optical power for the first direction of circularly polarized light, and the second geometric phase positive lens presents positive optical power for the second direction of circularly polarized light that is opposite to the first direction of circularly polarized light.

2. The two-dimensional beam scanning system based on a dual off-axis geometric phase lens group according to claim 1, characterized in that: Both the first geometric phase positive lens and the second geometric phase positive lens are composed of a substrate and an array of subwavelength structural units arranged on the substrate. The length, width, and height of the subwavelength structural unit are all subwavelength scales. The phase of the transmitted light is modulated by adjusting the rotation angle of the subwavelength structural unit in the plane, and the phase delay satisfies the formula: ； in, This represents the phase retardation of the transmitted light. It is the spin state of the incident circularly polarized light, and Corresponding to left-handed circularly polarized light LCP, Corresponding to right-hand circularly polarized light RCP, , The coordinates are two-dimensional rectangular coordinates within the lens plane. For the subwavelength structural unit in the lens plane coordinates The rotation angle at the corresponding position.

3. The two-dimensional beam scanning system based on a dual off-axis geometric phase lens group according to claim 2, characterized in that: The first geometric phase positive lens is designed to focus the phase distribution for left-hand circularly polarized light, and the second geometric phase positive lens is designed to focus the phase distribution for right-hand circularly polarized light. The phase distributions of the first geometric phase positive lens and the second geometric phase positive lens both satisfy the off-axis focusing formula, and under the same incident polarized light, the phase responses of the first geometric phase positive lens and the second geometric phase positive lens are conjugate to each other.

4. The two-dimensional beam scanning system based on a dual off-axis geometric phase lens group according to claim 3, characterized in that: The off-axis focusing formula satisfied by the phase distributions of the first and second geometrical phase positive lenses is: ； in, The phase distribution of a geometrically phased positive lens. As the focus item, The linear phase gradient is equivalent to a wedge prism in physical optics, and it represents the deflection term. For the system's operating wavelength, This corresponds to the focal length of a geometrically phase positive lens. The preset off-axis distance between the lens phase distribution center and its own physical rotation center. A constant phase term; phase off-axis distance Corresponding beam deflection angle The deflection effect of the lens is equivalent to a deflection vector with a fixed modulus. .

5. The two-dimensional beam scanning system based on a dual off-axis geometric phase lens group according to claim 1, characterized in that: It also includes a controller and a high-precision encoder; the controller is electrically connected to the first hollow rotary motor, the second hollow rotary motor and the high-precision encoder respectively. The high-precision encoder is used to collect the real-time rotation angle and speed signals of the first hollow rotary motor and the second hollow rotary motor and feed them back to the controller. The controller is used to output matching speed and phase control commands according to the feedback signals to form independent closed-loop PID control for the two hollow rotary motors respectively.

6. A two-dimensional beam scanning method based on a dual off-axis geometric phase lens group, applied to the two-dimensional beam scanning system based on a dual off-axis geometric phase lens group as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Start the controller and obtain the absolute zero position of the first hollow rotary motor and the second hollow rotary motor in real time through the high-precision encoder; according to the preset target, the controller pre-drives the first hollow rotary motor and the second hollow rotary motor to rotate to the target mechanical angle, sets the initial phase difference between the two motors, and completes the initial phase calibration of the system. S2. Turn on the light source component to output a stable continuous wave or pulsed laser beam; Adjust the front-end components of the optical path to ensure that the light beam incident on the first geometric phase positive lens is circularly polarized light with a single rotation direction; S3. The controller receives the target scanning trajectory command and independently controls the rotational angular velocity of the first hollow rotary motor and the second hollow rotary motor in a closed loop. The beam is sequentially subjected to two-stage phase modulation through the first geometric phase positive lens and the second geometric phase positive lens to form a corresponding deflection vector. The two deflection vectors are vector synthesized at the focal plane to form a two-dimensional beam scanning trajectory that matches the target command. S4. During the scanning process, the high-precision encoder feeds back the real-time angle signals of the two motors to the controller in real time. The controller performs closed-loop PID control based on the feedback signals to maintain the motor speed and phase accuracy.

7. The two-dimensional beam scanning method based on a dual off-axis geometric phase lens group according to claim 6, characterized in that: The total deflection position of the beam in the focal plane satisfies the vector composition relationship: ； in, The rotational angular velocity of the first hollow rotary motor, The rotational angular velocity of the second hollow rotary motor. For the time variable of the scanning process, for The beam of light is in the focal plane at any given moment. The deflection position in the axial direction, for The beam of light is in the focal plane at any given moment. The deflection position in the axial direction, The initial phase difference between the first hollow rotary motor and the second hollow rotary motor; This is the magnitude of the deflection vector corresponding to the first geometric phase positive lens. The deflection vector magnitude corresponding to the second geometric phase positive lens; by adjusting the rotational angular velocity of the first hollow rotary motor. The rotational angular velocity of the second hollow rotary motor The initial phase difference between the first hollow rotary motor and the second hollow rotary motor Three parameters control the shape, size, and fill density of the scan trajectory.

8. The two-dimensional beam scanning method based on a dual off-axis geometric phase lens group according to claim 7, characterized in that: By adjusting the rotational angular velocity of the first hollow rotary motor Rotational angular velocity of the second hollow rotary motor The matching relationship generates two-dimensional scanning trajectories in the form of circles, straight lines, spirals, and petals / quadrifoglio. When generating a circular scan trajectory, control By adjusting the initial phase difference between the first hollow rotary motor and the second hollow rotary motor Adjust the scan radius to achieve a scan radius from its minimum value. To the maximum value The stepless continuous scaling, the scan radius satisfies: ； in, This is the deflection magnitude corresponding to the first geometric phase positive lens. This is the deflection magnitude value corresponding to the second geometric phase positive lens; When generating a straight-line scan trajectory, control and By adjusting the initial spatial phase of the first hollow rotary motor and the second hollow rotary motor , Adjust the azimuth and tilt angles of the scanning line until the azimuth and tilt angles meet the requirements. This enables 360° full-range linear scanning pointing control; among which, The reference rotational angular velocity in linear scan mode. The equivalent deflection vector magnitude of the two lenses. This represents the initial spatial phase of the first hollow rotating electric motor. This represents the initial spatial phase of the second hollow rotating electric motor. The azimuth and tilt angle of the scanning line; When generating the spiral scan trajectory, control and There are tiny differences Archimedean spirals are formed based on the beat frequency effect, and by adjusting... The size of the radial fill density of the scan trajectory is adjusted by adjusting the reference rotation speed. Adjust the scan frame rate; among which, This represents the difference in angular velocity between the two rotating motors. This is the reference rotational speed for helical scanning; When generating petal / quadrifoglio-shaped scan trajectories, control and For a ratio of coprime integers m:n, satisfying , ,in, The basic unit angular velocity is m and n, which are positive integers that are coprime. The number of petals in the scanning trajectory is adjusted by adjusting the value of the coprime integer ratio m:n. The overall rotation of the scanning pattern on the focal plane is achieved by adjusting the initial phase of the first hollow rotary motor and the second hollow rotary motor.

9. The two-dimensional beam scanning method based on a dual off-axis geometric phase lens group according to claim 6, characterized in that: During the scanning process, the angular velocity and initial phase difference of the first and second hollow rotary motors are adjusted in real time by the controller to achieve real-time switching between different scanning trajectories.

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