A method for fast scanning target positioning using a shaped beam based on a single-pixel detector

Abstract

The present invention discloses a method for quickly scanning a target by a shaped light beam based on a single-pixel detector, comprising: shaping a pulsed laser beam emitted by a laser using a light speed shaping device, and scanning the target area using the shaped light beam; using a receiving telescope and a beam splitter to divide the field echo light intensity into two paths of light: one of the light paths images the echo light intensity distribution onto a grayscale gradient mask plate, and converges the light intensity distribution passing through the mask plate to the photosensitive detection surface of the single-pixel detector through a lens for detection; the other light path directly converges the echo light intensity to the single-pixel detector through a lens for detection; the position of the target centroid is calculated by two real-time synchronously obtained light path detection values, and the distance measured by the pulsed laser is combined to finally obtain the three-dimensional positioning coordinates of the target. The present invention has the characteristics of high detection sensitivity, long detection distance, and strong real-time performance, and can effectively realize the detection of small targets under simple backgrounds such as the sky and the ocean.

Description

Technical Field

[0001] The invention relates to the technical field of photoelectric scanning and positioning, and in particular to a shaping light beam fast scanning target positioning method based on a single-pixel detector. Background Art

[0002] Small target detection is of great significance in security and other fields. Traditional scanning laser radar uses a thin beam to scan point by point (such as CN108226954A, CN113596298A), which requires a high sampling rate and the search efficiency cannot meet the requirements.

[0003] The large-scale spot illumination and area array detection method, such as using ICCD detectors to obtain range images (such as CN101498786A, CN111722248A), is used to perform imaging before positioning. The sampling frequency is slow, and the detection range and depth are limited due to the dispersion of the emitted spot energy.

[0004] Therefore, there is an urgent need for a high-precision, high-sensitivity, fast search and positioning method. Summary of the invention

[0005] The present invention provides a shaped light beam fast scanning target positioning method based on a single-pixel detector, which has the characteristics of high detection sensitivity, long detection distance, and strong real-time performance, and can effectively realize small target detection under simple backgrounds such as sky and ocean.

[0006] A method for quickly scanning a target with a shaped beam based on a single-pixel detector comprises the following steps:

[0007] A light shaping device is used to shape the pulsed laser beam emitted by the laser, and the shaped beam is used to scan the field of view where the target is located;

[0008] The receiving telescope and beam splitter are used to split the field echo light intensity into two paths for detection: in one path, the echo light intensity distribution is imaged onto a grayscale gradient mask designed according to the shape of the shaped beam, and the light intensity distribution passing through the mask is converged to the photosensitive detection surface of a single-pixel detector through a lens for detection; in the other path, the echo light intensity is directly converged to another single-pixel detector through a lens for detection;

[0009] Two optical path detection values ​​are obtained synchronously in real time through two single-pixel detectors, and the position of the target's center of mass is calculated based on the detection values ​​of the two single-pixel detectors. Combined with the distance measured by the pulsed laser, the three-dimensional positioning coordinates of the target are finally obtained.

[0010] Furthermore, the grayscale gradient mask is designed according to the shape of the emitted shaped light beam, the grayscale gradient direction is consistent with the shape of the shaped light beam, and the grayscale gradient pattern is printed on the mask using the half-tone technology.

[0011] Furthermore, the single pixel detector includes but is not limited to a photomultiplier tube PMT, an avalanche photodiode APD, a photodiode PD, a silicon photomultiplier tube MPPC, and the like.

[0012] When a linear cross-section beam is used to scan the target area, the intensity-gradient modulated light field generated by the grayscale gradient mask It is expressed as:

[0013] ;

[0014] in, represents the linear cross-section coordinates of the light spot, is the intensity encoding slope constant; the beam splitter adopts a 1:1 light intensity fraction ratio, and the detection values ​​obtained by the two optical path single-pixel detectors are:

[0015] ;

[0016] ;

[0017] in, The target area irradiated by the linear cross-section beam in the field of view is obtained by scanning the linear cross-section beam to obtain the coordinate position of the target centroid in the linear cross-section direction. It is expressed as: ;

[0018] Combined with the target distance z obtained by pulse laser ranging, the three-dimensional cylindrical coordinates of the target (i0, φ, z) are finally obtained, where: It indicates the angle between the turntable and the initial position during the scanning process, which is obtained by the angle sensor on the turntable.

[0019] Optionally, a cylindrical lens, a wave mirror or a Powell prism is used to shape the laser beam into a linear cross-section beam.

[0020] When a circular cross-section beam is used to scan the area where a small target is located, the position of the target in the field of view is expressed in polar coordinates. Indicates that is the radius of the annular cross-section spot in the field of view, obtained through experimental calibration; Indicates the angle between different coordinate positions of the annular cross-section spot and the horizontal direction;

[0021] Grayscale gradient mask template produces Correlated intensity gradient modulated light field It is expressed as:

[0022] ;

[0023] in, is the intensity encoding slope constant; the beam splitter adopts a 1:1 light intensity fraction ratio, and the detection values ​​obtained by the two optical path single-pixel detectors are:

[0024] ;

[0025] ;

[0026] in, is the target area illuminated by the annular cross-section beam in the field of view, and the angle between the position of the target centroid in the annular cross-section spot and the horizontal direction is obtained. ;

[0027] Combined with the target distance z obtained by pulse laser ranging, the three-dimensional coordinates of the target (r, θ o ,z).

[0028] Optionally, an axicon or a spiral phase plate is used to shape the laser beam into a beam with an annular cross-section.

[0029] Preferably, the two single-pixel detectors need to be triggered by a synchronous timing trigger module to achieve real-time synchronous acquisition of the two single-pixel detectors.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. In the present invention, when the shaped beam scans a small target, a receiving telescope and a beam splitter are used to divide the field echo light intensity into two paths for detection: in one path, the echo light intensity distribution is imaged onto a grayscale gradient mask, and the light intensity distribution passing through the mask is converged to the photosensitive detection surface of a single pixel detector through a lens for detection; in the other path, the echo light intensity is directly converged to the single pixel detector through a lens for detection, and the single pixel detection value is further subjected to corresponding centroid extraction operations to obtain the two-dimensional positioning of the target. Compared with the original shaped beam scanning array detection, the single pixel detection method used in the rapid scanning process of the shaped beam has the characteristics of high detection sensitivity, long detection distance, and strong real-time performance, and can effectively realize the detection of small targets under simple backgrounds such as the sky and the ocean.

[0032] 2. The receiving system of the present invention adopts a grayscale gradient mask and two single-pixel detectors for detection, with a faster scanning and positioning frequency and higher real-time detection. At the same time, compared with the solution using the traditional digital micromirror array DMD or spatial light modulator SLM, the hardware cost is greatly reduced; it can realize rapid scanning, searching and positioning of small targets in a simple background environment without imaging the target. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1This is a flow chart of a method for quickly scanning a target using a shaped light beam based on a single-pixel detector according to an embodiment of the present invention.

[0034] Figure 2 Schematic diagram of the scanning positioning system corresponding to the linear cross-section light beam in Example 1.

[0035] Figure 3 Schematic diagram of the scanning positioning system corresponding to the annular cross-section light beam in Example 2.

[0036] Figure 4 It is a grayscale gradient mask corresponding to different shaped beam shapes.

[0037] In the figure: 1-laser, 2-beam shaping device, 3-transmitting mirror group, 4-small target to be detected, 5-receiving telescope, 6-beam splitter, 7-converging lens No. 1, 8-single-pixel detector No. 1, 9-grayscale gradient mask, 10-converging lens No. 2, 11-single-pixel detector No. 2. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on the present invention.

[0039] The method provided by the present invention can be implemented by using corresponding modules, devices, units, etc. in the system. The embodiments in the method can be understood as preferred examples for constructing the system and will not be described in detail here.

[0040] like Figure 1 As shown, a method for quickly scanning a target with a shaped beam based on a single-pixel detector mainly includes the following steps:

[0041] S01, using a beam shaping device to shape the pulsed laser beam into a desired shape.

[0042] According to the needs, the shaped beam can be divided into a linear cross-section beam and a circular cross-section beam. Among them, the linear cross-section beam is obtained by shaping the laser beam using an aspheric lens (such as a cylindrical lens, a wave mirror, a Powell prism, etc.); the circular cross-section beam is obtained by shaping the laser beam using an aspheric lens (such as a conical lens, a spiral phase plate, etc.).

[0043] S02, the shaped light beam scans the target area through the medium.

[0044] S03, using a receiving telescope and a beam splitter to split the field of view echo light intensity into two paths of light for receiving and detection.

[0045] Optical path 1: Different grayscale gradient masks are designed according to the shape of the emitted shaped light beam, the echo light intensity distribution is imaged onto the grayscale gradient mask, and a single-pixel detector is used to detect the light intensity value passing through the mask.

[0046] Optical path 2: Directly use a single-pixel detector to detect the echo light intensity value in the field of view.

[0047] Single-pixel detectors can use photomultiplier tubes PMT, avalanche photodiodes APD, silicon photomultiplier tubes MPPC, etc.

[0048] S04, calculating the position of the target's centroid based on the single-pixel detection value, and performing ranging in combination with the pulse laser echo time, and finally obtaining the three-dimensional coordinates of the target. Example 1

[0049] This embodiment uses an aspherical lens (such as a cylindrical lens, a wave mirror, a Powell prism, etc.) to shape the laser beam into a linear cross-section beam.

[0050] like Figure 2 As shown, the transmitting system is installed on a turntable. In the transmitting system, the pulsed laser beam emitted by the laser 1 is shaped into a linear cross-section beam after passing through the beam shaping device 2; the linear cross-section beam passes through the transmitting mirror group 3 and scans the small target 4 to be detected in the target area through the medium;

[0051] In the receiving system, a receiving telescope 5 and a beam splitter 6 are used to divide the field echo light intensity into two paths for detection: in one path, the echo light intensity distribution is imaged onto a grayscale gradient mask plate 9 designed according to a linear cross-section light beam, and the light intensity distribution passing through the grayscale gradient mask plate 9 is converged to the photosensitive detection surface of the second single-pixel detector 11 through a second converging lens 10 for detection; in the other path, the echo light intensity is directly converged to the first single-pixel detector 8 through a first converging lens 7 for detection. The detection values ​​of the two light paths are obtained synchronously and in real time through the two single-pixel detectors.

[0052] The grayscale gradient mask corresponding to the linear cross-section beam is as follows: Figure 4 When a linear cross-section beam is used to scan the target area, the grayscale gradient mask produces the linear cross-section coordinates of the spot. Correlated intensity gradient modulated light field It is expressed as:

[0053] ;

[0054] in, is the intensity encoding slope constant; the beam splitter adopts a 1:1 light intensity fraction ratio, and the detection values ​​obtained by the two optical path single-pixel detectors are:

[0055] ;

[0056] ;

[0057] in, The target area irradiated by the linear cross-section beam in the field of view is obtained by scanning the linear cross-section beam to obtain the coordinate position of the target centroid in the linear cross-section direction. It is expressed as: ;

[0058] Combined with the target distance z obtained by pulse laser ranging, the three-dimensional cylindrical coordinates of the target (i0, φ, z) are finally obtained, where It represents the angle between the turntable and the initial position during the scanning process, which is obtained by the angle sensor. Example 2

[0059] This embodiment uses an aspherical lens (such as an aconic lens, a spiral phase plate, etc.) to shape the laser beam into a ring-shaped cross-section beam.

[0060] like Figure 3 As shown, the transmitting system is installed on a turntable. In the transmitting system, the pulsed laser beam emitted by the laser 1 is shaped into a circular cross-section beam after passing through the beam shaping device 2; the circular cross-section beam passes through the transmitting mirror group 3 and scans the small target 4 to be detected in the target area through the medium.

[0061] In the receiving system, a receiving telescope 5 and a beam splitter 6 are used to divide the field echo light intensity into two paths for detection: in one path, the echo light intensity distribution is imaged onto a grayscale gradient mask plate 9 designed with a ring-shaped cross-section beam, and the light intensity distribution passing through the grayscale gradient mask plate 9 is converged to the photosensitive detection surface of the second single-pixel detector 11 through the second converging lens 10 for detection; in the other path, the echo light intensity is directly converged to the first single-pixel detector 8 through the first converging lens 7 for detection. The detection values ​​of the two light paths are obtained synchronously and in real time through the two single-pixel detectors.

[0062] The grayscale gradient mask corresponding to the annular cross-section beam is as follows: Figure 4 When a circular beam is used to scan the area where a small target is located, the position of the target in the field of view is expressed in polar coordinates. Indicates that is the radius of the annular cross-section spot in the field of view, obtained through experimental calibration; Indicates the angle between different coordinate positions of the annular cross-section spot and the horizontal direction;

[0063] The angle between the grayscale gradient mask and the horizontal direction Correlated intensity gradient modulated light field It is expressed as:

[0064] ;

[0065] in, is the intensity encoding slope constant; the beam splitter adopts a 1:1 light intensity fraction ratio, and the detection values ​​obtained by the two optical path single-pixel detectors are:

[0066] ;

[0067] ;

[0068] in, is the target area illuminated by the annular cross-section beam in the field of view, and the angle between the position of the target centroid in the annular cross-section spot and the horizontal direction is obtained. ;

[0069] Combined with the target distance z obtained by pulse laser ranging, the three-dimensional coordinates of the target (r, θ o ,z).

[0070] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for quickly scanning a target using a shaped beam based on a single-pixel detector, characterized in that: The following steps are involved: A light shaping device is used to shape the pulsed laser beam emitted by the laser, and the shaped beam is used to scan the field of view where the target is located; When a linear cross-section beam is used to scan the target area, the intensity-gradient modulated light field generated by the grayscale gradient mask It is expressed as: ； in, represents the linear cross-section coordinates of the light spot, is the intensity encoding slope constant; the beam splitter adopts a 1:1 light intensity fraction ratio, and the detection values ​​obtained by the two optical path single-pixel detectors are: ； ； in, The target area irradiated by the linear cross-section beam in the field of view is obtained by scanning the linear cross-section beam to obtain the coordinate position of the target centroid in the linear cross-section direction. It is expressed as: ; Combined with the target distance z obtained by pulse laser ranging, the three-dimensional cylindrical coordinates of the target (i0, φ, z) are finally obtained, where It indicates the angle between the turntable and the initial position during scanning, which is obtained by the angle sensor on the turntable; When a circular cross-section beam is used to scan the area where a small target is located, the position of the target in the field of view is expressed in polar coordinates. Indicates that is the radius of the annular cross-section spot in the field of view, obtained through experimental calibration; Indicates the angle between different coordinate positions of the annular cross-section spot and the horizontal direction; Grayscale gradient mask template produces Correlated intensity gradient modulated light field It is expressed as: ； in, is the intensity encoding slope constant; the beam splitter adopts a 1:1 light intensity fraction ratio, and the detection values ​​obtained by the two optical path single-pixel detectors are: ； ； in, is the target area illuminated by the annular cross-section beam in the field of view, and the angle between the position of the target centroid in the annular cross-section spot and the horizontal direction is obtained. ; Combined with the target distance z obtained by pulse laser ranging, the three-dimensional coordinates of the target (r, θ o ,z); The receiving telescope and beam splitter are used to split the field echo light intensity into two paths for detection: in one path, the echo light intensity distribution is imaged onto a grayscale gradient mask designed according to the shape of the shaped beam, and the light intensity distribution passing through the mask is converged to the photosensitive detection surface of a single-pixel detector through a lens for detection; in the other path, the echo light intensity is directly converged to another single-pixel detector through a lens for detection; Two optical path detection values ​​are obtained synchronously in real time through two single-pixel detectors, and the position of the target's center of mass is calculated based on the detection values ​​of the two single-pixel detectors. Combined with the distance measured by the pulsed laser, the three-dimensional positioning coordinates of the target are finally obtained.

2. The method for quickly scanning a target using a shaped beam based on a single pixel detector according to claim 1, characterized in that: The grayscale gradient mask is designed according to the shape of the emitted shaped light beam, the grayscale gradient direction is consistent with the shape of the shaped light beam, and the grayscale gradient pattern is printed on the mask using the half-tone technology.

3. The method for quickly scanning a target using a shaped beam based on a single pixel detector according to claim 1, characterized in that: The single pixel detector adopts a photomultiplier tube PMT, an avalanche photodiode APD, a photodiode PD or a silicon photomultiplier tube MPPC.

4. The method for quickly scanning a target using a shaped beam based on a single pixel detector according to claim 1, characterized in that: A cylindrical lens, wave mirror or Powell prism is used to shape the laser beam into a linear cross-section beam.

5. The method for quickly scanning a target using a shaped beam based on a single pixel detector according to claim 1, characterized in that: A conic lens or a spiral phase plate is used to shape the laser beam into a beam with a ring cross section.

6. The method for quickly scanning a target using a shaped beam based on a single pixel detector according to claim 1, characterized in that: The two single-pixel detectors need to be triggered by a synchronous timing trigger module to achieve real-time synchronous acquisition of the two single-pixel detectors.

Images