Laser scanning device and method based on dynamic coupling of transmission metasurface-wedge mirror

Abstract

The application relates to a laser scanning device and method based on transmission metasurface-wedge mirror dynamic coupling, and relates to the technical field of optical scanning. A transmission metasurface divides a single laser beam into multiple transmission laser beams with the same light intensity, and the propagation directions of the multiple transmission laser beams are all deflected by an angle relative to the incident direction of the single laser beam. A wedge prism is arranged on the outgoing light path of the transmission metasurface and performs secondary deflection on the multiple transmission laser beams before the laser beams are emitted to a target surface. By controlling the transmission metasurface and the wedge prism to rotate at the same or different speeds, corresponding scanning tracks are generated to cover the target surface for laser scanning. By coupling the transmission metasurface and the wedge prism, the single laser beam is divided into multiple transmission laser beams, and the scanning angle is significantly increased in cooperation with the rotating process, so that the amount of data obtained in the scanning process is increased, and the scanning precision is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical scanning technology, in particular to a laser scanning device and method based on dynamic coupling of a transmission metasurface-wedge mirror. BACKGROUND

[0002] Laser scanning technology is one of the core technologies of airborne laser radar, and is also an indispensable part of remote sensing surveying and mapping, three-dimensional reconstruction and other fields, and has wide practical value. At present, the main laser scanning methods used in airborne laser radar include line scanning method, rotating scanning method and fiber scanning method.

[0003] The line scanning method in the application of airborne laser radar can provide high-precision scanning data, but its shortcomings are also obvious. First, the scanning speed is limited, due to the limitation of mechanical moving parts, it cannot meet the demand of high-speed scanning, which affects the efficiency of data acquisition to some extent. Secondly, long-term use will cause wear and tear of mechanical parts, increase the failure rate, and reduce the reliability and stability of the device. In addition, environmental factors such as temperature and humidity may cause slight deformation of mechanical parts, thereby affecting the scanning accuracy. At the same time, the physical limitation of the scanning mirror makes the scanning range limited, which is difficult to meet the demand of large-scale scanning. Finally, the scanning lines on the ground may overlap, resulting in data redundancy, increasing the complexity and time cost of data processing.

[0004] The fiber scanning method as a new type of laser scanning method still has some obstacles in the application of airborne laser radar. First, the technology is not mature enough, there are potential technical risks and reliability problems, which limit its popularization in practical application. Secondly, high-performance fiber components and precise control devices result in high cost, and the complexity of the device increases, which increases the difficulty of use and maintenance. In addition, the fiber scanning method is sensitive to environmental factors, which may cause performance degradation or instability. At the same time, the length limitation of the fiber makes the scanning range limited, which cannot meet the demand of long-distance scanning. Finally, the fiber may have loss and attenuation in the transmission process, which affects the intensity and stability of the scanning signal, further limiting the application range of the fiber scanning method.

[0005] The rotating scanning method to some extent avoids the shortcomings of the above two methods, but its scanning range is not flexible, which is limited by the fixed inclination angle of the scanning mirror, lacks flexibility, and the polarization angle of the wedge prism in the rotating scanning method is limited, which also limits the scanning range and efficiency of the rotating scanning method. Moreover, when the plane flies at high speed, data acquisition may be missing, and the lack of data quantity may lead to the decrease of three-dimensional reconstruction accuracy, which is also a common problem of single laser scanning. Therefore, it is urgent to optimize and improve the existing rotating scanning method to solve the problems of limited scanning angle and few scanning laser beams. SUMMARY

[0006] To solve the problems in the background art, the application provides a laser scanning device and method based on dynamic coupling of a transmission metasurface-wedge mirror, which divides a single laser beam into multiple transmission laser beams by coupling a transmission metasurface with a wedge prism, significantly increases the scanning angle during rotation, and increases the amount of data obtained during scanning and improves scanning accuracy.

[0007] To achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0008] The laser scanning device based on dynamic coupling of a transmission metasurface-wedge mirror comprises transmission metasurfaces and wedge prisms arranged at intervals along the axial direction, the transmission metasurfaces can divide a single laser beam into multiple transmission laser beams with the same light intensity, and the propagation directions of the multiple transmission laser beams all have deflection angles relative to the incident direction of the single laser beam, the wedge prisms are arranged on the outgoing light path of the transmission metasurfaces and emit the multiple transmission laser beams to a target surface after secondary deflection, and the transmission metasurfaces and the wedge prisms are controlled to rotate at the same or different speeds to generate corresponding scanning tracks to cover the target surface for laser scanning.

[0009] Further, the material of the transmission metasurfaces is monocrystalline silicon, and the material of the wedge prisms is BK7 optical glass.

[0010] The laser scanning method based on dynamic coupling of a transmission metasurface-wedge mirror comprises the following steps:

[0011] First, a single laser beam is divided into multiple transmission laser beams with different deflection angles by a transmission metasurface;

[0012] Second, the multiple transmission laser beams are incident to a wedge prism for secondary deflection;

[0013] Finally, the transmission metasurface and the wedge prism are rotated at the same speed or different speeds in the axial direction to dynamically adjust the laser scanning path, wherein the deflection angles during dynamic coupling of the transmission metasurface and the wedge prism are mathematically expressed as follows:

[0014]

[0015] In the formula, θ m is the total deflection angle of the single laser beam after passing through the transmission metasurface and the wedge prism, is the deflection angle of the single laser beam after passing through the transmission metasurface, m is the beam order, n is the refractive index of the wedge prism, and a is the wedge angle of the wedge prism.

[0016] Compared with the prior art, the application has the following beneficial effects:

[0017] 1. The application adds a transmissive metasurface for light splitting in the single-wedge prism laser scanning mode, increases the number of scanning laser beams, increases the amount of data obtained during scanning, improves scanning accuracy, and significantly increases the scanning angle compared to the single-wedge prism laser scanning mode. The scanning area covered by the scanning trajectory can be more than 22 times that of the single-wedge prism scanning mode, achieving large-scale scanning tasks.

[0018] 2. Compared with the double-wedge prism laser combined scanning mode, the application not only obtains a larger laser scanning angle, but also has a compact structure, greatly reducing the volume and weight, which helps to reduce the load of the carrier, and can obtain a faster rotating speed during laser scanning, facilitating miniaturization and making the application more widely used.

[0019] 3. The application couples the transmissive metasurface with the wedge prism to realize multiple scanning beams during rotation, significantly increasing the scanning area of the light beam during laser scanning, especially suitable for use as a laser scanning part of an airborne laser radar, and can also be applied to more laser scanning scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a structural schematic diagram of the laser scanning device of the application;

[0021] Figure 2 is a schematic diagram of the beam propagation path of the laser scanning device in the embodiment;

[0022] Figure 3 is a laser spot position distribution diagram of a single laser beam after passing through the transmissive metasurface on a one-meter target surface in the embodiment;

[0023] Figure 4 is a laser spot position distribution diagram of a single laser beam after passing through the transmissive metasurface on a one-meter target surface in the embodiment;

[0024] Figure 5 is a laser spot trajectory diagram of the laser scanning device of the application in the rotating state on a one-meter target surface in the embodiment;

[0025] Figure 6 is a laser spot trajectory diagram of the laser scanning device of the application in the rotating state on a one-kilometer target surface in the embodiment;

[0026] Figure 7 is a scanning area comparison schematic diagram of the laser scanning device of the application and the single-transmissive metasurface scanning mode and the single-wedge prism scanning mode in the embodiment;

[0027] Figure 8is the laser landing point trajectory diagram of the wedge prism with a deflection angle of 8 degrees at a rotation speed of 8 rad / s of the transmissive metasurface of the laser scanning device of the application in the embodiment;

[0028] Figure 9 is the laser landing point trajectory diagram of the wedge prism with a deflection angle of 8 degrees at a rotation speed of 3 rad / s of the transmissive metasurface of the laser scanning device of the application in the embodiment;

[0029] Figure 10 is the laser landing point trajectory diagram of the wedge prism with a deflection angle of 8 degrees at a rotation speed of 6 rad / s of the transmissive metasurface of the laser scanning device of the application in the embodiment;

[0030] Figure 11 is the laser landing point trajectory diagram of the wedge prism with a deflection angle of 8 degrees at a rotation speed of 15 rad / s of the transmissive metasurface of the laser scanning device of the application in the embodiment;

[0031] Figure 12 is the laser landing point trajectory diagram of the wedge prism with a deflection angle of 8 degrees at a rotation speed of 30 rad / s of the transmissive metasurface of the laser scanning device of the application in the embodiment;

[0032] Figure 13 is the laser landing point trajectory diagram of the wedge prism with a deflection angle of 2 degrees at a rotation speed of 8 rad / s of the transmissive metasurface of the laser scanning device of the application in the embodiment.

[0033] In the figure: 1, single beam laser; 2, transmissive metasurface; 3, wedge prism; 4, laser. DETAILED DESCRIPTION

[0034] The technical solutions in the application will be described clearly and completely below in conjunction with the drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the protection scope of the application.

[0035] As Figure 1As shown, a laser scanning device based on dynamic coupling of a transmission metasurface and a wedge-shaped mirror comprises a transmission metasurface 2 and a wedge-shaped prism 3 arranged at intervals along the axial direction. The transmission metasurface 2 can split a single laser beam 1 into multiple transmission laser beams with the same light intensity. The propagation directions of the multiple transmission laser beams have a deflection angle relative to the incident direction of the single laser beam 1. The wedge-shaped prism 3 is arranged on the outgoing light path of the transmission metasurface 2 and performs secondary deflection on the multiple transmission laser beams. For example, the transmission metasurface 2 splits the single laser beam 1 into multiple transmission laser beams with the same light intensity. Seven transmitted laser beams with the same light intensity and deflection angles of a°, ±b°, ±c° and ±d° in the emission direction are incident on the plane of the wedge-shaped prism 3 with a fixed wedge angle and emitted to the target surface after being deflected by its oblique surface. By controlling the transmission metasurface 2 and the wedge-shaped prism 3 to rotate at the same or different speeds, corresponding scanning trajectories are generated to cover the target surface for laser scanning. Since the rotation speeds of the transmission metasurface 2 and the wedge-shaped prism 3 are independently adjustable, dynamic control of the scanning density can be achieved by adjusting the speed difference.

[0036] Preferably, the material of the transmissive metasurface 2 is single crystal silicon, and the material of the wedge prism 3 can be BK7. BK7 is a common optical glass widely used in visible light and near-infrared bands, and has good transmittance and excellent processing performance.

[0037] like Figure 1 As shown, the laser scanning method based on the dynamic coupling of the transmission metasurface and the wedge mirror includes the following steps:

[0038] First, a single laser beam 1 is split into multiple transmitted laser beams with different deflection angles through a transmissive metasurface 2.

[0039] Secondly, multiple beams of transmitted laser light are incident on the wedge-shaped prism 3 for secondary deflection, and the secondary deflection angle is determined by the refractive index and wedge angle of the wedge-shaped prism 3;

[0040] Finally, the transmissive metasurface 2 and the wedge-shaped prism 3 are rotated in the axial direction at the same speed or different speeds to dynamically adjust the laser scanning path. The deflection angle during the dynamic coupling between the transmissive metasurface 2 and the wedge-shaped prism 3 is mathematically expressed as follows:

[0041]

[0042] Where: θ m is the total deflection angle of a single laser beam after passing through the transmissive metasurface and the wedge prism, is the deflection angle of a single laser beam after passing through the transmissive metasurface, m is the beam order, n is the refractive index of the wedge prism, and α is the wedge angle of the wedge prism.

[0043] Example

[0044] The material of the transmission metasurface 2 in the embodiment is monocrystalline silicon with a thickness of 525±15 μm, and the material of the wedge prism 3 is BK7 optical glass with a refractive index of 1.51 at a wavelength of 1064 nm and a wedge angle of 5.318°±0.002°.

[0045] In combination Figure 2 As shown in the figure, the laser 4 emits a single laser beam 1 with a wavelength of 1064 nm, and the transmission metasurface 2 divides the single laser beam 1 into seven transmission laser beams with the same intensity and a deflection angle of 0°, ±10°, ±30°, and ±50° relative to the incident direction. The seven laser beams are incident to the wedge prism 3, and the scanning angle is expanded after being deflected again.

[0046] In combination Figure 3 As shown in the figure, the laser beam 1 is only deflected by the transmission metasurface 2, and the laser spot position distribution on the target surface one meter away from the transmission metasurface 2 is shown.

[0047] The transmission metasurface 2 and the wedge prism 3 are coupled in the present application, which can further deflect the transmission laser based on the transmission metasurface 2, in combination Figure 4 As shown in the figure, the laser beam 1 is deflected by the transmission metasurface 2 and the wedge prism 3 in a static state, and the laser spot position distribution on the target surface one meter away from the transmission metasurface 2 is shown. The transmission metasurface 2 and the wedge prism 3 are rotated together to generate a concentric circular ring of the laser spot trajectory, in combination Figure 5 As shown in the figure, the laser spot trajectory on the target surface one meter away from the transmission metasurface 2 in a rotating state is shown. The target surface is moved away from the transmission metasurface 2 to a position one kilometer away, in combination Figure 6 As shown in the figure, the laser spot trajectory on the target surface one kilometer away from the transmission metasurface 2 in a rotating state is shown.

[0048] Compared with the single transmission metasurface scanning mode and the single wedge prism scanning mode, the laser scanning device of the present application can greatly increase the scanning area of the light beam during the scanning process, in combination Figure 7As shown, the scanning area comparison between the laser scanning device of the present invention and the single transmission metasurface scanning method and the single wedge prism scanning method is shown. The three scanning methods have the same conditions, namely, a rotation speed of 20 rad / s, a distance of 100m from the ground, and a working time of 3 seconds. The direction of the arrow in the figure is the flight direction of the aircraft. Part (a) shows the scanning trajectory of the transmitted laser with the largest deflection angle of the laser scanning device of the present invention, part (b) shows the scanning trajectory of the single transmission metasurface scanning method, and part (c) shows the scanning trajectory of the single wedge prism scanning method. The scanning area width of the laser scanning device of the present invention is 320 meters, while the scanning area width of the single transmission metasurface scanning method is 119.17 meters, and the scanning area width of the single wedge prism scanning method is 14.06 meters, which verifies that the present invention significantly increases the scanning area during the scanning process.

[0049] In addition, the transmissive metasurface 2 and the wedge-shaped prism 3 in the laser scanning device of the present invention can also rotate at different speeds. As the differential speed changes, the trajectory of the laser scanning point will also be adjusted accordingly. Figure 8 As shown, the laser landing trajectory of the transmissive metasurface 2 at a rotation speed of 1 rad / s and the wedge prism 3 with a deflection angle of 8 degrees at a rotation speed of 8 rad / s is shown; combined with Figure 9 As shown, the laser landing trajectory of the transmissive metasurface 2 at a rotation speed of 1 rad / s and the wedge prism 3 with a deflection angle of 8 degrees at a rotation speed of 3 rad / s is shown; combined with Figure 10 As shown, the laser landing trajectory of the transmissive metasurface 2 at a rotation speed of 1 rad / s and the wedge prism 3 with a deflection angle of 8 degrees at a rotation speed of 6 rad / s is shown; combined with Figure 11 As shown, the laser landing trajectory of the transmissive metasurface 2 at a rotation speed of 1 rad / s and the wedge prism 3 with a deflection angle of 8 degrees at a rotation speed of 15 rad / s is shown; Figure 12 As shown, the laser landing trajectory of the transmissive metasurface 2 at a rotation speed of 1 rad / s and the wedge prism 3 with a deflection angle of 8 degrees at a rotation speed of 30 rad / s is shown; combined with Figure 13 As shown, the laser landing trajectory of the transmissive metasurface 2 at a rotation speed of 1 rad / s and the wedge prism 3 with a deflection angle of 2 degrees at a rotation speed of 8 rad / s is shown.

[0050] In summary, the laser scanning device and method based on dynamic coupling of transmission metasurface and wedge mirror designed in the present invention have significant advantages over other laser scanning methods. It can achieve large laser scanning angle and multiple scanning beams, and the device structure is compact. During the laser scanning process, the scanning area of ​​the beam is greatly increased. It is particularly suitable for use as the laser scanning part of airborne laser radar, and can also be applied to more laser scanning scenarios.

[0051] It is apparent to a person skilled in the art that the present application is not limited to the details of the above-described exemplary embodiments, but that it can be implemented in other embodiments without departing from the spirit or essential characteristics of the application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, the scope of the application being defined by the appended claims rather than by the above description, and all changes coming within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. No reference signs in the claims should be considered as limiting the scope of the claims to the features to which the reference signs are attached.

[0052] Furthermore, it should be understood that although the description is made on embodiments, not every embodiment contains only one independent technical solution, and the description is made in this way only for the sake of clarity, and a person skilled in the art should consider the description as a whole, and the technical solutions in each embodiment can also be combined appropriately to form other embodiments that can be understood by a person skilled in the art.

Claims

1. A laser scanning device based on dynamic coupling of a transmissive metasurface and a wedge mirror, characterized by: The invention comprises a transmissive metasurface (2) and a wedge-shaped prism (3) arranged at intervals along an axial direction. The transmissive metasurface (2) can split a single laser beam (1) into multiple transmitted laser beams with the same light intensity, and the propagation directions of the multiple transmitted laser beams all have a deflection angle relative to the incident direction of the single laser beam (1). The wedge-shaped prism (3) is arranged on the outgoing light path of the transmissive metasurface (2) and deflects the multiple transmitted laser beams twice before emitting them to a target surface. By controlling the transmissive metasurface (2) and the wedge-shaped prism (3) to rotate at the same or different speeds, a corresponding scanning trajectory is generated to cover the target surface for laser scanning.

2. The laser scanning device based on dynamic coupling of a transmission metasurface and a wedge mirror according to claim 1, characterized in that: The material of the transmissive metasurface (2) is single crystal silicon, and the material of the wedge-shaped prism (3) is BK7 optical glass.

3. A laser scanning method based on dynamic coupling of a transmission metasurface and a wedge mirror, characterized by: The laser scanning device according to claim 1, wherein the scanning method comprises the following steps: First, a single laser beam (1) is split into multiple transmitted laser beams with different deflection angles by a transmissive metasurface (2); Secondly, multiple beams of transmitted laser light are incident on a wedge-shaped prism (3) for secondary deflection; Finally, the transmissive metasurface (2) and the wedge-shaped prism (3) are rotated in the axial direction at the same speed or different speeds to dynamically adjust the laser scanning path, wherein the deflection angle during the dynamic coupling between the transmissive metasurface (2) and the wedge-shaped prism (3) is mathematically expressed as follows: Where: θ m is the total deflection angle of a single laser beam after passing through the transmissive metasurface and the wedge prism, is the deflection angle of a single laser beam after passing through the transmissive metasurface, m is the beam order, n is the refractive index of the wedge prism, and α is the wedge angle of the wedge prism.

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