A multi-spectral laser imaging radar system based on an array of APDs and supercontinuum laser

Abstract

The application discloses a kind of multispectral laser imaging radar systems based on APD array and supercontinuum laser, wavelength covering 450~2400nm supercontinuum laser is used as light source, the continuous laser output is collimated after being collimated by laser collimating system, multi-band fast selection is realized by acousto-optic tunable filter, and uniform emission is completed in combination with variable-focus laser emission optical system;Then, large field of view receiving optical system is constructed, and the echo signal is detected by APD array detector to realize multi-pixel parallel detection, the echo intensity data corresponding to different wavelengths are acquired, and the multispectral reflection information of target is formed.Finally, the laser emission time and APD array receiving time are accurately synchronized, based on time-of-flight ranging principle, the high-precision space-time information of target point cloud data and multispectral information is synchronously acquired.The application realizes the high spectral information acquisition accuracy while breaking through the efficiency and resolution limit of traditional single-point imaging mode.

Description

Technical Field

[0001] This invention relates to methods in the field of laser remote sensing, and mainly designs a multispectral laser imaging radar system based on APD array and supercontinuous laser. Background Technology

[0002] With the rapid development of laser remote sensing technology, lidar (LiDAR), as an important active remote sensing method, possesses high-precision three-dimensional spatial perception capabilities and is widely used in topographic mapping, target recognition, UAV remote sensing, autonomous driving, and military reconnaissance. However, traditional lidar systems mainly acquire target distance and spatial structure information, with limited ability to identify target material composition and physical properties, making it difficult to meet the application requirements of high-precision target perception and fine classification in complex environments. In recent years, hyperspectral lidar (HSL), by combining the three-dimensional spatial perception capabilities of traditional lidar with the fine spectral discrimination capabilities of hyperspectral remote sensing, has achieved simultaneous acquisition of target spatial structure and spectral characteristics, becoming one of the important research directions in the field of laser remote sensing, and showing great potential in ecological and environmental monitoring, water observation, resource exploration, and national defense and security.

[0003] Existing HSL systems typically employ avalanche photodiodes (APDs) as photodetectors, combined with multi-band or tunable laser sources to detect multispectral echo signals from targets. However, these systems generally use a single-detector unit structure, acquiring target information point-by-point through mechanical scanning. This single-point imaging mode suffers from low imaging efficiency, complex system structure, limited stability and reliability, and difficulty in balancing a large field of view with high spatial resolution. Furthermore, traditional multi-band or tunable laser sources have limited wavelength coverage, complex system tuning, and high costs, making it difficult to achieve continuous, high-resolution spectral detection over a wide spectral range.

[0004] Supercontinuum lasers, with their advantages of wide spectral coverage, good continuity, and high temporal coherence, offer a new technological path for building next-generation multispectral laser imaging radar systems. However, effectively integrating supercontinuum lasers with high-performance detector arrays to overcome the limitations of traditional single-point imaging modes while ensuring hyperspectral detection capabilities, achieving multi-pixel parallel detection, improving imaging efficiency and spatial resolution, and enhancing system stability and practicality remain key challenges in current technological development.

[0005] Against this backdrop, there is an urgent need to develop a multispectral laser imaging radar system that integrates the broadband emission capability of supercontinuum lasers with the parallel detection advantages of APD arrays. This system should maintain the accuracy of high-spectral information acquisition while overcoming the efficiency and resolution limitations of traditional single-point imaging modes, enabling the simultaneous and efficient acquisition of target spatial structure and spectral characteristic information. This would meet the pressing demand for high-precision, multi-dimensional sensing capabilities in complex application scenarios. This invention is proposed in this context and possesses significant engineering application value and strategic importance. Summary of the Invention

[0006] To address the problems in existing technologies, this invention provides a multispectral laser imaging radar system based on an APD array and a supercontinuum laser. This system utilizes a supercontinuum laser with wavelengths covering 450–2400 nm as a light source, achieves rapid multi-band selection through an acousto-optic tunable filter, and combines this with a variable-focus laser emission optical system to achieve stable and uniform emission. Simultaneously, a large field-of-view receiving optical system is constructed, employing an APD array for multi-pixel parallel detection. Combined with the Time-of-Flight (TOF) ranging principle, this achieves high-precision spatiotemporal synchronous acquisition of target point cloud data and multispectral information, thereby significantly improving the system's imaging efficiency, spatial resolution, and stability.

[0007] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0008] The multispectral laser imaging radar system based on APD array and supercontinuum laser includes the following steps:

[0009] Step 1: Using supercontinuum laser as the light source, the output laser is collimated by a collimation system and then introduced into an acousto-optic tunable filter (AOTF) through an optical fiber to select the wavelength and filter the laser band.

[0010] Step 2: A zoomable laser emission system is constructed using a zoom lens structure to adjust the laser divergence angle and spot size so that the laser illuminates the target scene in a uniform and stable manner.

[0011] Step 3: Use an APD array to perform high-precision detection and array imaging of multi-band laser echo intensity, simultaneously acquire the imaging position of the target on the image plane and the corresponding multispectral intensity information, and combine the imaging geometric model to realize the spatial position and orientation calculation of the target.

[0012] Step 4: Accurately synchronize the laser emission time with the avalanche photodiode (APD) array reception time, calculate the target distance information based on the time of flight (TOF) to obtain point cloud data, and perform time and space registration with the multispectral information to achieve high-precision spatiotemporal synchronization of target point cloud and spectral data.

[0013] Furthermore, in step 1, this invention utilizes the advantages of supercontinuum lasers, such as wide spectral coverage, good continuity, and high temporal coherence, employing a supercontinuum laser with a spectral coverage of 450~2400nm to generate a broadband continuous-spectrum laser signal. The output beam of the supercontinuum laser is collimated and shaped by a collimating lens group, ensuring good spatial consistency and stable beam quality. Based on this, the collimated laser is introduced into an acousto-optic tunable filter (AOTF) via fiber optic coupling, enabling rapid selection and filtering of the desired wavelength from the supercontinuum laser. The AOTF is a tunable bandpass narrowband filter with a bandwidth of several nanometers to tens of nanometers. It utilizes the acousto-optic effect to achieve diffraction and frequency modulation of the optical signal, typically controlled by applying a radio frequency (RF) signal. Using an AOTF device, rapid and dynamic selection of a specific wavelength from a broadband supercontinuum laser source can be achieved. As the frequency of the RF signal applied to the AOTF changes, the filtering center wavelength changes continuously in the time dimension, thereby generating a laser pulse with high spectral resolution. The wavelength tuning process is typically completed within tens of microseconds or even less. The selected wavelength satisfies the following relationship:

[0014]

[0015] in, Selected wavelength; The difference in refractive index is caused by birefringence; The frequency of the applied radio frequency signal; The velocity of sound waves in a crystalline material; The incident angle between the source laser beam and the crystal material to be modulated in the radio frequency.

[0016] Furthermore, in step 2, a zoom-emitting optical system composed of multiple lens groups is used as the laser emitting lens. This system employs a zoom lens structure, including a front lens group, a middle zoom lens group, and a rear compensation lens group. Each lens group is arranged along the optical axis and its displacement is controlled by a precision mechanical adjustment mechanism. By adjusting the relative positions of the lens groups, the overall focal length of the system is adjusted, thereby precisely controlling the divergence angle and spot size of the output laser. Through this zoom adjustment structure and control method, while maintaining good collimation and energy distribution stability of the laser beam, the laser divergence characteristics are continuously adjustable, enabling uniform and stable laser illumination of the target scene according to different detection distances and imaging resolution requirements.

[0017] Furthermore, in step 3, the laser echo signal first enters the complete optical receiving system, which includes a receiving lens, a filter, an APD array, and a back-end processing circuit. Based on the detection of multi-band laser echo intensity and array imaging by the APD array, the imaging position of the target on the image plane and the corresponding multispectral intensity information are acquired simultaneously. Combined with the imaging geometric model, the spatial position and orientation of the target are calculated. Specifically, this includes the following two sub-steps:

[0018] Step 3.1: After the laser pulse is emitted and reflected by the target, the echo light signals of different bands are converged by the receiving optical system and imaged onto the detection surface of the APD array. After collimation, focusing, and aberration correction, a stable two-dimensional energy distribution image of the target on the array is formed. Each pixel of the array performs photon counting and integral sampling processing on the echo light intensity of each band, and obtains the two-dimensional intensity distribution of the target on the array within a preset time gate window.

[0019] Let the size of the APD array be , No. The echo signal corresponding to each pixel is Integral processing is performed on each pixel within a preset time-gated window:

[0020]

[0021] Obtain the multi-band two-dimensional intensity distribution of the target on the array:

[0022]

[0023] vector The multispectral feature information of the target is constituted; the precise imaging position of the target on the array image plane is calculated by the weighted centroid method.

[0024] By utilizing the fixed spatial relationships between array pixels, a weighted centroid calculation is performed on the echo energy distribution to determine the precise imaging position of the target on the array image plane.

[0025] .

[0026] in, , These represent the first and second digits of the APD array, respectively. The horizontal and vertical coordinates of a pixel in the image plane coordinate system are used to characterize the spatial position of the pixel. , They respectively represent based on the first Band intensity distribution The weighted centroid abscissa and ordinate of the target on the array image plane are calculated.

[0027] Step 3.2: After obtaining the target's imaging position on the array image plane, a geometric mapping relationship between the image plane and space is established by combining imaging parameters such as the focal length, optical axis direction, and image plane center position of the receiving optical system. Based on the imaging geometric model, the target image plane coordinates are transformed. This provides the corresponding field of view information, and further calculates the spatial direction vector of the target in the detection coordinate system.

[0028] Furthermore, in step 4, a Time-to-Digital Converter (TDC) based on a 12-bit binary counting structure is used to measure the laser echo time. Simultaneously with the laser pulse emission, a start trigger signal is sent to the TDC. Upon receiving the echo photon signal, the avalanche photodiode (APD) array pixels generate a stop trigger signal. The TDC counts the time interval between the two triggers and outputs a digital value. Combining this with the Time of Flight (TOF) ranging principle, the one-way propagation distance of the laser is calculated. :

[0029]

[0030] in, For time resolution, 400MHz is typically chosen; The speed of light is chosen to be 3 × 10⁸ m / s.

[0031] This allows us to determine the actual distance between the target and the system:

[0032]

[0033] The system reads the TDC count value corresponding to each pixel of the APD array, and combines it with the array spatial arrangement and receiving optical geometry model to map the distance information into three-dimensional spatial coordinates, thereby generating a three-dimensional point cloud of the target. Furthermore, the echo intensity data of different wavelengths obtained in step 3 are registered with the distance information according to a unified timestamp to achieve high-precision spatiotemporal synchronous acquisition of target spatial structure information and multispectral characteristic information.

[0034] Beneficial Effects: The multispectral laser imaging radar system based on APD array and supercontinuum laser provided by this invention possesses high imaging efficiency, high spatial-spectral synchronization accuracy, and strong engineering applicability. By utilizing a supercontinuum laser source with a spectral coverage of 450–2400 nm to generate broadband multi-wavelength pulsed laser signals, and combining this with the multi-pixel parallel detection capability of the APD array, high-precision spatiotemporal synchronous acquisition of target point cloud data and multispectral reflectance information is achieved. This significantly improves imaging efficiency and spatial resolution while ensuring high spectral resolution. The system eliminates the dependence on complex mechanical structures in traditional single-point scanning modes, enabling stable, high-precision, and multi-dimensional information acquisition. It meets the high-precision, multispectral sensing requirements of various application scenarios such as UAV remote sensing, ground object classification, target recognition, and disaster monitoring, and has good engineering application prospects and promotional value. Attached Figure Description

[0035] Figure 1 A diagram of a multispectral laser imaging radar system based on an APD array and supercontinuum laser provided by this invention;

[0036] Figure 2 This is a schematic diagram of the working principle of the APD array system provided by the present invention;

[0037] Figure 3 This is a schematic diagram of the multi-lens zoom emission optical system provided by the present invention;

[0038] Figure 4 The images show the target detection imaging results at different wavelengths provided by this invention. Detailed Implementation

[0039] The invention will now be further described with reference to the accompanying drawings.

[0040] The technical solution provided by this invention is a multispectral laser imaging radar system based on an APD array and a supercontinuum laser: First, a broadband continuous spectrum laser signal is generated using a supercontinuum laser with a spectral coverage range of 450–2400 nm as the light source, and the laser beam is collimated and shaped. AOTF (Optical Aperture Tolerance) is used to achieve rapid selection and filtering of the required wavelength. Second, a variable-focus laser emission system is constructed using a variable-focus lens structure, and the laser divergence angle and spot size are adjusted to ensure that the laser illuminates the target scene uniformly and stably. Then, a multi-pixel parallel detection of the target echo signal is performed using an APD array-based detector to obtain echo intensity information corresponding to different wavelengths. Finally, the laser emission time and the APD array reception time are precisely synchronized, and target point cloud data is obtained by combining the time-of-flight (TOF) ranging principle. The point cloud data and multispectral information are then time- and spatially registered to achieve high-precision spatiotemporal synchronous acquisition of target spatial structure information and spectral characteristic information.

[0041] Furthermore, this application provides a multispectral laser imaging radar system based on an APD array and supercontinuum laser:

[0042] Step 1: A supercontinuum laser with a spectral range of 450–2400 nm is used as the light source. After the output laser is collimated by a collimation system, it is introduced into an acousto-optic tunable filter (AOTF) through an optical fiber to select and filter the wavelength or band of the laser.

[0043] Step 2: A variable-focus laser emission system is constructed using a variable-focus lens structure to adjust the laser divergence angle and spot size, so that the laser illuminates the target scene in a uniform and stable manner.

[0044] Step 3: Use an APD array to perform high-precision detection and array imaging of multi-band laser echo intensity, simultaneously obtain the precise imaging position of the target on the image plane and the corresponding multispectral intensity information, and combine the imaging geometric model to realize the spatial position and orientation calculation of the target.

[0045] Step 4: Accurately synchronize the laser emission time with the APD array reception time, calculate the target distance information based on the time of flight (TOF) to obtain point cloud data, and perform time and space registration with the multispectral information to achieve high-precision spatiotemporal synchronization of target point cloud and spectral data.

[0046] The embodiments of the present invention are described in detail below:

[0047] Step 1, as follows Figure 1As shown, this invention fully utilizes the advantages of supercontinuum lasers, such as wide spectral coverage, good continuity, and high temporal coherence. A supercontinuum laser with a spectral coverage of 450–2400 nm is selected as the system light source to generate a broadband continuous-spectrum laser signal. The output laser is first collimated and shaped by a collimating lens group, giving the emitted beam good spatial consistency, stable beam quality, and optical characteristics suitable for subsequent modulation and transmission. The collimated laser is then introduced into an acousto-optic tunable filter (AOTF) via fiber optic coupling, enabling rapid selection and narrowband filtering of the target wavelength within the supercontinuum laser. The AOTF operates based on the acousto-optic effect; under radio frequency (RF) signal excitation, it achieves diffraction and frequency modulation of the incident light signal through a periodic refractive index modulation structure formed by the acoustic wave in the crystal medium. By adjusting the frequency of the applied RF signal, rapid and dynamic selection of any target wavelength within the broadband supercontinuum laser can be achieved. As the frequency of the radio frequency signal applied to the AOTF changes continuously, the filter center wavelength becomes continuously adjustable in the time dimension, thereby forming a narrowband laser pulse output with high spectral resolution. This wavelength tuning process can typically be completed in tens of microseconds or even less, meeting the system's requirements for high-speed multispectral modulation. The selected wavelength satisfies the following relationship:

[0048]

[0049] in, Selected wavelength; The difference in refractive index is caused by birefringence; The frequency of the applied radio frequency signal; The velocity of sound waves in a crystalline material; The incident angle between the source laser beam and the crystal material to be modulated in the radio frequency.

[0050] Through the above structural design, the present invention achieves high-speed and precise wavelength modulation and multi-band laser output of broadband supercontinuum laser in step 1, providing a stable and controllable light source foundation for subsequent multispectral laser emission and parallel detection of APD array.

[0051] Step 2, as follows Figure 1 As shown, this invention employs a zoom-emitting optical system composed of multiple lens groups as the laser emitting lens. This emitting optical system uses a zoom lens structure, and by adjusting the relative positions of the lens groups, the system's focal length is continuously changed, thereby precisely controlling the laser divergence angle and spot size. Specifically, as... Figure 3As shown, the transmitting optical system includes a front lens group, a middle zoom lens group, and a rear compensation lens group. These lens groups are arranged along the optical axis and their displacement is controlled by a precision mechanical adjustment mechanism. When different lens groups undergo relative displacement along the optical axis, the overall focal length of the system changes accordingly, causing the output laser beam to form different divergence angles and spot sizes in the far field. Through this zoom adjustment mechanism, the laser divergence characteristics can be continuously adjusted while maintaining beam collimation and energy distribution stability.

[0052] Through the above structural design, the present invention can dynamically adjust the laser divergence angle and spot size according to the requirements of the detection mission, while ensuring the uniformity and stability of the beam energy, so that the laser illuminates the target scene in a uniform and stable manner, providing good transmission conditions for subsequent echo reception and multi-pixel parallel detection of the APD array.

[0053] Step 3, as follows Figure 3 As shown, the laser echo signal first enters the complete optical receiving system, which consists of a receiving lens, a filter, an APD array, and a back-end processing circuit. Based on the high-precision detection and array imaging of multi-band laser echo intensity using the APD array, the precise imaging position of the target on the image plane and the corresponding multispectral intensity information are simultaneously acquired. Combined with the imaging geometry model, the spatial position and orientation of the target are calculated. Specifically, this includes the following two steps:

[0054] Step 3.1: After the laser pulse is emitted and reflected by the target, the echo light signals of different wavelengths are converged by the receiving optical system onto the APD array detection surface. After collimation, focusing, and aberration correction, a target array image is formed. Each pixel in the array performs photon counting and integral sampling processing on the echo intensity of each wavelength band. Within a preset time-gated window, a two-dimensional energy distribution image of the target echo on the array and its corresponding multi-band intensity data are acquired, thereby constructing the multispectral feature information of the target and extracting the precise imaging position of the target. Let the array size be... , No. The echo signal corresponding to each pixel is Integral processing is performed on each pixel within a preset time-gated window:

[0055]

[0056] This allows us to obtain the multi-band two-dimensional intensity distribution of the target on the array:

[0057]

[0058] This vector constitutes the multispectral feature information of the target. Based on this, using the fixed spatial positional relationship between array pixels, a weighted centroid calculation is performed on the echo energy distribution to determine the precise imaging position of the target on the array image plane.

[0059]

[0060] in, , These represent the first and second digits of the APD array, respectively. The horizontal and vertical coordinates of a pixel in the image plane coordinate system are used to characterize the spatial position of the pixel. , They respectively represent based on the first Band intensity distribution The weighted centroid abscissa and ordinate of the target on the array image plane are calculated.

[0061] Step 3.2: After obtaining the target's imaging position on the array image plane, a geometric mapping relationship between the image plane and space is established by combining imaging parameters such as the focal length, optical axis direction, and image plane center position of the receiving optical system. Based on the imaging geometric model, the target image plane coordinates are transformed. This provides the corresponding field of view information, and further calculates the spatial direction vector of the target in the detection coordinate system.

[0062] Step 4, as follows Figure 3 As shown, this invention employs a digital time converter (TDC) based on a 12-bit binary counting structure to perform high-precision measurement of laser echo time, with a counting range of 0–4095. The laser emits a pulse signal and simultaneously sends a start trigger signal to the TDC. When each pixel in the APD array receives the echo photon signal, it generates a stop trigger signal. The TDC counts the time interval between the two triggers and outputs the corresponding digital time value. By analyzing the time data collected by the TDC and combining it with the time-of-flight (TOF) ranging principle, the system can accurately calculate the propagation distance of the laser pulse in space. (Laser one-way propagation distance) Determined by the following formula:

[0063]

[0064] in, For time resolution, 400MHz is typically chosen; The speed of light is chosen to be 3 × 10⁸ m / s.

[0065] This allows us to determine the actual distance between the target and the system:

[0066]

[0067] After the laser echo signal acquisition is completed, the system reads the TDC count value corresponding to each pixel in the APD array and calculates the target distance information corresponding to each pixel according to the above relationship. Combining the spatial arrangement of the APD array and the geometric mapping model of the receiving optical system, the distance information measured by each pixel can be mapped into three-dimensional spatial coordinates, thereby constructing the three-dimensional point cloud data of the target.

[0068] Based on this, and combined with the echo intensity information at different wavelengths obtained in step 3, the distance information and the corresponding multispectral echo intensity data are registered according to a unified timestamp to achieve high-precision spatiotemporal synchronous acquisition of target spatial structure information and spectral characteristic information.

[0069] To verify the effectiveness of the multispectral laser imaging radar system based on an APD array and supercontinuum laser designed in this invention, the embodiment uses a supercontinuum laser (model: Anyang SC-5), with an operating wavelength of 400nm~2500nm and a repetition frequency of 2MHz. In the receiving optical system, a standard fixed-focus lens with a focal length of 16mm is used and mounted at the front end of the APD array. The readout circuit and driver of the APD array are implemented based on a SOC (ARM7), and the APD registers are configured through a Linux system running on the SOC to operate in ranging mode. Due to the requirements of the signal reception range, the lens uses a relatively small focal length design to obtain a large field of view exceeding 23°, enabling it to capture laser signals reflected from targets over a wide range. In the experiment, multispectral laser detection imaging was performed on yellow and green leaves. Figure 4 The results were compared with those obtained using laser instruments. The results showed that the correlation between the yellow leaves and the green leaves reached 82%, fully verifying the effectiveness and reliability of the system in multispectral target imaging and recognition.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Several improvements and refinements can be made without departing from the principle of the invention, and these improvements and refinements should also be considered within the scope of protection of the present invention.

Claims

1. A multispectral laser imaging radar system based on APD array and supercontinuum laser, characterized in that: The non-multispectral laser imaging radar system includes the following steps: Step 1: Using supercontinuum laser as the light source, the output laser is collimated by a collimation system and then introduced into an acousto-optic tunable filter (AOTF) through an optical fiber to select the wavelength and filter the laser band. Step 2: A zoomable laser emission system is constructed using a zoom lens structure to adjust the laser divergence angle and spot size so that the laser illuminates the target scene in a uniform and stable manner. Step 3: Use an APD array to perform high-precision detection and array imaging of multi-band laser echo intensity, simultaneously acquire the imaging position of the target on the image plane and the corresponding multispectral intensity information, and combine the imaging geometric model to realize the spatial position and orientation calculation of the target. Step 4: Accurately synchronize the laser emission time with the avalanche photodiode (APD) array reception time, calculate the target distance information based on time-of-flight (TOF) to obtain point cloud data, and perform time and space registration with the multispectral information to achieve high-precision spatiotemporal synchronization of target point cloud and spectral data.

2. The multispectral laser imaging radar system based on APD array and supercontinuum laser according to claim 1, characterized in that: In step 1, a supercontinuum laser with a spectral coverage range of 450~2400nm is used to generate a broadband continuous spectrum laser signal. The output beam of the supercontinuum laser is collimated and shaped by a collimating lens group. The collimated laser is then introduced into an acousto-optic tunable filter (AOTF) via fiber optic coupling to achieve rapid selection and filtering of the required wavelength in the supercontinuum laser. The selected wavelength satisfies the following relationship: ； in, Selected wavelength; The difference in refractive index is caused by birefringence; The frequency of the applied radio frequency signal; The velocity of sound waves in a crystalline material; The incident angle between the source laser beam and the crystal material to be modulated in the radio frequency.

3. The multispectral laser imaging radar system based on APD array and supercontinuum laser according to claim 1, characterized in that: In step 2, the variable-focus laser emitting system consists of multiple lens groups. The emitting lens adopts a variable-focus structure, including a front lens group, a middle zoom lens group, and a rear compensation lens group arranged sequentially along the optical axis. Each lens group achieves linkage displacement control along the optical axis through a precision mechanical adjustment mechanism. By adjusting the relative position between each lens group, the overall focal length of the system is changed, thereby adjusting the divergence angle and spot size of the output laser.

4. The multispectral laser imaging radar system based on APD array and supercontinuum laser according to claim 1, characterized in that: In step 3, the laser echo signal first enters the complete optical receiving system, which includes a receiving lens, a filter, an APD array, and a back-end processing circuit. Based on the detection of multi-band laser echo intensity and array imaging by the APD array, the imaging position of the target on the image plane and the corresponding multispectral intensity information are obtained simultaneously. Combined with the imaging geometric model, the spatial position and orientation of the target are calculated. Let the size of the APD array be , No. The echo signal corresponding to each pixel is Integral processing is performed on each pixel within a preset time-gated window: ； Obtain the multi-band two-dimensional intensity distribution of the target on the array: ； vector This constitutes the multispectral feature information of the target; By utilizing the fixed spatial relationships between array pixels, a weighted centroid calculation is performed on the echo energy distribution to determine the precise imaging position of the target on the array image plane. ； in, , These represent the first and second digits of the APD array, respectively. The horizontal and vertical coordinates of a pixel in the image plane coordinate system are used to characterize the spatial position of the pixel. , They respectively represent based on the first Band intensity distribution The weighted centroid abscissa and ordinate of the target on the array image plane are calculated.

5. The multispectral laser imaging radar system based on APD array and supercontinuum laser according to claim 1, characterized in that: In step 4, a digital time converter (TDC) based on a 12-bit binary counting structure is used to measure the laser echo time. Simultaneously with the laser pulse emission, a start trigger signal is sent to the TDC. Upon receiving the echo photon signal, the avalanche photodiode (APD) array pixels generate a stop trigger signal. The TDC counts the time interval between the two triggers and outputs a digital value. Based on the time-of-flight ranging principle, the actual distance between the laser-detected target and the system for each pixel is calculated. ； in, This is the one-way propagation distance of the laser. For time resolution, The speed of light; By reading the time-to-digital converter (TDC) count values ​​of each pixel in the APD array, and combining the spatial arrangement of the APD array with the receiving optical geometry model, the actual distance information is mapped into three-dimensional spatial coordinates to generate a target three-dimensional point cloud; and the echo intensity data of different wavelengths are registered with the distance information according to a unified timestamp to achieve spatiotemporal synchronous acquisition of target spatial structure information and multispectral characteristic information.

Images