Hybrid solid-state laser radar for increasing signal dynamic range and control method

Abstract

The invention discloses a mixed solid state laser radar capable of increasing a signal dynamic range and a control method, the mixed solid state laser radar comprises a laser emitting unit, a laser receiving unit, an emitting reflector, a receiving reflector and a polyhedral rotating mirror, the laser emitting unit comprises a plurality of vertical cavity surface emitting lasers with adjustable power pulse width, the laser receiving unit is a single photon avalanche diode array sensor; the laser emission unit performs at least one emission cycle in one measurement. According to the invention, the transmission parameters are dynamically adjusted in a single distance measurement period, the signal dynamic range is expanded in the time correlation accumulation method process, and the measurement accuracy of the laser radar in long and short distance measurement is improved.

Description

Technical Field

[0001] The present invention relates to the field of laser radar technology, and in particular to a hybrid solid-state laser radar and a control method for increasing the signal dynamic range. Background Art

[0002] As the core sensor for high-precision three-dimensional environmental perception, LiDAR is widely used in autonomous driving, robot navigation, surveying and mapping and other fields. Its core technology relies on the precise measurement of the flight time of laser pulses, and obtains target distance information by calculating the time difference between emission and reception. The current mainstream solution is based on the pulse ranging method, which emits short pulses of laser (pulse width of a few nanoseconds to tens of nanoseconds, peak power of tens of watts to several kilowatts), uses an optical system to collimate and illuminate the target, and the reflected signal is focused to the photodetector through the receiving optical system, and the photodetector completes the echo capture. However, in the process of achieving high-precision ranging from meters to kilometers, the LiDAR system needs to meet the requirements of high detection sensitivity and wide dynamic range at the same time, which poses severe challenges to the design of the receiving circuit.

[0003] Currently, lidar receiving systems rely primarily on three types of photodetectors: avalanche photodiodes (APDs), silicon photomultipliers (SiPMs), and single-photon avalanche diodes (SPADs). While APDs have linear response characteristics, their sensitivity is limited, making them difficult to detect weak signals at long distances. While SiPMs have single-photon sensitivity, their output is an analog signal, requiring high-speed analog-to-digital converters and time-to-digital converters for signal processing, resulting in high system complexity. While SPADs have single-photon detection capabilities and output digital pulses that can be directly time-stamped, making them suitable for high-resolution array designs, they have a limited inherent dynamic range. For close-range measurement targets such as road signs and vehicles, the number of photons received by the SPADs exceeds the limit, resulting in close-range reflectivity distortion. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a hybrid solid-state laser radar and a control method for increasing the signal dynamic range, so as to solve the problem of missing reflectivity signal in close-range ranging in the existing laser radar based on single-photon avalanche diode technology, thereby achieving the technical effect of increasing the signal dynamic range of a single measurement and improving the measurement accuracy of the laser radar.

[0005] In a first aspect, the present invention provides a hybrid solid-state laser radar with increased signal dynamic range, comprising:

[0006] A laser emitting unit, a laser receiving unit, a transmitting reflector, a receiving reflector and a polyhedron rotating mirror, wherein the laser emitting unit includes N vertical cavity surface emitting lasers with modulated power pulse width, and the laser receiving unit is a single photon avalanche diode array sensor;

[0007] The laser emitting unit and the emitting reflective mirror are arranged on one side of the polygonal rotating mirror, and together with the polygonal rotating mirror, form a laser emission optical path structure. The laser receiving unit and the receiving reflective mirror are also arranged on the same side of the polygonal rotating mirror, and the laser receiving unit, the receiving reflective mirror and the polygonal rotating mirror form a laser incident optical path structure.

[0008] The laser emitting unit performs at least one emission cycle in one measurement. In each emission cycle, each of M vertical cavity surface emitting lasers with modulated power pulse width emits Y detection lasers, where N>1, M≤N, M is a positive integer, Y≥3, and the total number of vertical cavity surface emitting lasers that emit detection lasers in the cumulative emission cycle is equal to N;

[0009] Among the Y detection lasers emitted in each emission cycle, the emission parameters of at least one detection laser are selected from the low power short pulse width range, the emission parameters of at least one detection laser are selected from the high power short pulse width range, and the emission parameters of at least one detection laser are selected from the high power long pulse width range.

[0010] Furthermore, the N vertical cavity surface emitting lasers are arranged in a vertical linear array.

[0011] Furthermore, the plurality of reflecting surfaces of the polyhedron rotating mirror are arranged in a manner that the circumference of the circumscribed circle of the cross section of the polyhedron rotating mirror is equally divided.

[0012] Furthermore, the N value is determined by the preset line number of the laser radar and the number of pixels covered by the vertical cavity surface emitting laser.

[0013] Furthermore, M≤N / 2.

[0014] Furthermore, the Y value is determined by calculating the preset radar detection conditions according to the laser radar equation.

[0015] Furthermore, an emission focusing and collimating unit is provided between the laser emission unit and the emission reflector, and a reception focusing and collimating unit and a filtering unit are provided in sequence between the laser receiving unit and the reception reflector.

[0016] In a second aspect, the present invention provides a control method for a hybrid solid-state laser radar for increasing a signal dynamic range, the method comprising:

[0017] The laser emitting unit performs at least one emission cycle in one measurement, and in each emission cycle, each of M vertical cavity surface emitting lasers with modulated power and pulse width emits Y detection lasers, wherein the laser emitting unit includes N vertical cavity surface emitting lasers with modulated power and pulse width, N>1, M≤N, M is a positive integer, Y≥3, and the total number of vertical cavity surface emitting lasers that emit detection lasers in a cumulative emission cycle is equal to N, and among the Y detection lasers emitted in each emission cycle, the emission parameters of at least one detection laser are selected from a low-power short-pulse-width range, the emission parameters of at least one detection laser are selected from a high-power short-pulse-width range, and the emission parameters of at least one detection laser are selected from a high-power long-pulse-width range;

[0018] Reflecting the detection laser to the polygonal rotating mirror through the transmitting reflector, and reflecting the detection laser through the polygonal rotating mirror to form a detection scanning light;

[0019] The echo signal generated by the detection scanning light scanning the target object is received by the polygonal rotating mirror, and the echo signal is reflected to the receiving reflector, and the echo signal is reflected to the laser receiving unit by the receiving reflector to complete a measurement.

[0020] Furthermore, the method further comprises:

[0021] Determining a measurement sequence type of the one measurement, where the measurement sequence type includes an initial measurement and a non-initial measurement;

[0022] In response to the measurement sequence type being an initial measurement, among the Y detection lasers emitted in each emission cycle, emission parameters of at least one detection laser are selected from a low-power short-pulse-width range, emission parameters of at least one detection laser are selected from a high-power short-pulse-width range, and emission parameters of at least one detection laser are selected from a high-power long-pulse-width range;

[0023] In response to the measurement sequence type being non-initial measurement, the emission parameters of the Y detection lasers emitted in each emission cycle are determined based on a preset step gain, where the step gain is the correspondence between the emission parameters of the vertical cavity surface emitting laser and the ranging distance, and the ranging distance is obtained by calculating the echo signal of the initial measurement by the laser receiving unit.

[0024] The present invention provides a hybrid solid-state laser radar (LiDAR) and control method for increasing signal dynamic range. By dynamically adjusting emission parameters within a single ranging cycle and expanding the signal dynamic range during the time-correlated accumulation method, this method simultaneously suppresses near-range saturation and enhances long-range sensitivity without increasing hardware complexity or the number of accumulations. This overcomes the problem of missing near-range reflectivity signals caused by parameter rigidity in conventional hybrid solid-state LiDARs based on single-photon avalanche diode technology. This enables the hybrid solid-state LiDAR to achieve high accuracy in long-range ranging while also maintaining measurement precision in close-range ranging, providing a new technical path for highly reliable sensing in complex scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic structural diagram of a hybrid solid-state laser radar for increasing signal dynamic range in an embodiment of the present invention;

[0026] Figure 2 is another structural schematic diagram of a hybrid solid-state laser radar for increasing signal dynamic range in an embodiment of the present invention;

[0027] Figure 3 is a schematic diagram of the field of view splicing of multiple transmitting lasers in an embodiment of the present invention;

[0028] Figure 4 3 is a schematic diagram of a third structure of a hybrid solid-state laser radar for increasing signal dynamic range in an embodiment of the present invention;

[0029] Figure 5 1 is a schematic diagram of pulses of a detection laser emitted multiple times in one measurement according to an embodiment of the present invention;

[0030] Figure 6 The laser receiving unit in the embodiment of the present invention is Figure 5 Schematic diagram of the response of the echo signal corresponding to the detection laser;

[0031] Figure 7 Schematic diagram of the response of the laser receiving unit to the echo signal during close-range distance measurement in an embodiment of the present invention;

[0032] Figure 8 Schematic diagram of the response of the laser receiving unit to the echo signal during long-distance ranging in an embodiment of the present invention;

[0033] Figure 9 It is a flow chart of the control method of the hybrid solid-state laser radar in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0035] See also Figure 1 The first embodiment of the present invention proposes a hybrid solid-state laser radar for increasing the signal dynamic range. The hybrid solid-state laser radar 1 includes a laser emitting unit 10, a laser receiving unit 20, a transmitting reflector 30, a receiving reflector 40 and a polyhedron rotating mirror 50.

[0036] The hybrid solid-state laser radar 1 of this embodiment adopts a conventional radar architecture, wherein the laser emitting unit 10 and the emitting reflector 30 are arranged on one side of the polygonal rotating mirror 50. The laser emitting unit 10, the emitting reflector 30 and the polygonal rotating mirror 50 together constitute a laser emission optical path structure. Under the laser emission optical path structure, the detection laser emitted by the laser emitting unit 10 passes through the emitting reflector 30 and is reflected to the polygonal rotating mirror 50, and the polygonal rotating mirror 50 forms a detection scanning light through rotation reflection.

[0037] On the same side of the polygonal rotating mirror 50, a laser receiving unit 20 and a receiving reflector 40 are also arranged. The laser receiving unit 20, the receiving reflector 40 and the polygonal rotating mirror 50 together constitute a laser incident optical path structure. Under the laser incident optical path structure, when the detection scanning light encounters the target object Object, the echo signal generated by it is reflected to the polygonal rotating mirror 50, reflected to the receiving reflector 40 through the polygonal rotating mirror 50, and the echo signal is reflected to the laser receiving unit 20 through the receiving reflector 40.

[0038] In this embodiment, the polyhedron rotating mirror 50 is driven by a motor to rotate around the central axis, and its reflecting surface is arranged in a manner that the circumference of the circumscribed circle of the cross-section of the polyhedron rotating mirror is equally divided. The detection laser is reflected in different directions by rotation to achieve scanning coverage. In order to make the radar structure compact and reduce the overall volume, suitable for vehicle-mounted front-end integration, while reducing mechanical complexity and improving reliability, the laser emitting unit 10 and the laser receiving unit 20 are arranged on the same side of the polyhedron rotating mirror 50, and physical isolation or multiplexing of the light receiving and light transmission paths are achieved through optical design. There is no specific limitation on the spatial position of the laser emitting unit 10, the laser receiving unit 20 and the polyhedron rotating mirror 50. The laser emitting unit 10 and the laser receiving unit 20 can be arranged on the same horizontal plane of the polyhedron rotating mirror 50, or on different horizontal planes.

[0039] When the laser emitting unit 10 and the laser receiving unit 20 are arranged on the same horizontal plane of the polygon mirror 50, refer to Figure 2 An emission focusing and collimating unit 60 is provided between the laser emitting unit 10 and the emission reflector 30, and a receiving focusing and collimating unit 70 and a filtering unit 80 are provided in sequence between the laser receiving unit 20 and the receiving reflector 40. Optionally, the emission focusing and collimating unit 60 and the receiving focusing and collimating unit 70 are respectively composed of one or more focusing and collimating lenses, and the filtering unit 80 is composed of one or more filters. The detection laser emitted by the laser emitting unit 10 passes through the focusing and collimating unit 60, is incident on the emission reflector 30, and is reflected by the emission reflector 30 to the polygonal rotating mirror 50, and finally scanned by the rotation of the polygonal rotating mirror 50. When the detection scanning light scans the target object and generates an echo signal, the echo signal is diffusely reflected and returns to the polygonal rotating mirror 50 along the optical path. The polygonal rotating mirror 50 reflects the echo signal to the transmitting reflector 30. In order to achieve optical path multiplexing, the transmitting reflector 30 uses a polarization splitter to transmit the echo signal to the receiving reflector 40. The receiving reflector 40 reflects the echo signal. The reflected echo signal passes through the filtering unit 80 and the receiving focusing and collimating unit 70 and is received by the laser receiving unit 20.

[0040] When the laser emitting unit 10 and the laser receiving unit 20 are not on the same horizontal plane as the polygonal rotating mirror 50, the emitting reflector 30 and the receiving reflector 40 can respectively use lens groups to adjust the optical paths of the detection laser and the echo signal to ensure that the detection laser can achieve target scanning detection through the emitting lens group and the polygonal rotating mirror 50, and ensure that the echo signal can return to the laser receiving unit 20 through the polygonal rotating mirror 50 and the reflecting lens group. The specific structure can refer to the structure of a conventional laser radar with a lens group, and will not be repeated here.

[0041] In this embodiment, the laser emitting unit 10 includes N vertical cavity surface emitting lasers (VCSELs) 101, where N is greater than 1, and the N VCSELs 101 are arranged in a vertical linear array to form an emitting array. The laser receiving unit 20 uses a single photon avalanche diode (SPAD) array sensor.

[0042] Conventional hybrid solid-state lidars using single-photon avalanche diode technology require multiple measurements when measuring the distance to a target. SPADs use time-correlated accumulation (TCSPC) to store and time the number of photons measured each time, thereby achieving high-precision ranging. The number of measurements ranges from a few to thousands, and the specific number can be determined based on the usage scenario. When SPADs detect a photon, they determine the detection time of the photon. Each time such an event (photon) is recorded, 1 is added to the corresponding storage unit, and the address of the storage unit corresponds to the detection time. After recording many photons, the distribution of detection times, that is, the waveform of the light pulse, can be obtained based on the number of photons in each unit in the memory. The peak point of the waveform can be used to determine the flight time, and the product of the flight time and the speed of light can be used to achieve single-shot ranging of the lidar.

[0043] To obtain a more stable echo signal and improve measurement accuracy, conventional hybrid solid-state lidars using single-photon avalanche diode (SPAD) technology use a single power and pulse width for each measurement. That is, each vertical cavity surface emitting laser (VCSEL) in the laser emitting unit emits a probe laser once during a measurement, and the probe laser emitted during each measurement has a single fixed frequency and fixed pulse width. The problem with this single-parameter emission mode is that when multiple VCSELs emit simultaneously at a fixed high power, the number of echo photons at close range far exceeds the capacity of the SPADs unit, resulting in loss of reflectivity information. While reducing the emission power can reduce the loss of reflectivity information, the number of long-range signal photons is further reduced, requiring more accumulation times, which reduces the response speed of the lidar system. Therefore, this single-parameter emission mode cannot balance the requirements of high dynamics at close range and high sensitivity at long range, thereby limiting the adaptability of hybrid solid-state lidars using single-photon avalanche diode (SPAD) technology in complex scenarios, such as those on urban roads with multiple reflectivity targets such as lane lines, vehicles, and road signs.

[0044] In order to solve the above problems, the hybrid solid-state laser radar 1 of this embodiment adopts multiple power pulse width modulated vertical cavity surface emitting lasers 101 as the laser emitting unit 10 on the basis of the architecture of the conventional SPADs laser radar. Since the number of pixels of the SPADs determines the number of lines of the laser radar, under the specified size, the number of pixels covered by each vertical cavity surface emitting laser 101 is fixed. Therefore, the number of vertical cavity surface emitting lasers 101 in the laser emitting unit 10 can be determined by the line number requirement of the laser radar. For example, in order to achieve a laser radar with 256 lines, SPADs need to have 256 pixels. Assuming that each vertical cavity surface emitting laser 101 covers 32 pixels, 8 vertical cavity surface emitting lasers 101 are required to splice the emission field of view, that is, Figure 3 As shown. Since the aspect ratio of the VCSEL affects the yield of the laser, and each VCSEL illuminates multiple pixels during the emission process, an overly long VCSEL will cause difficult-to-control crosstalk. Therefore, the crosstalk can be reduced by reducing the size of the VCSEL and increasing the number of VCSELs. In this embodiment, preferably, VCSELs with an aspect ratio not exceeding 5:1 are selected, and the laser emission unit 10 is formed in the form of a vertical linear array.

[0045] In this embodiment, the hybrid solid-state laser radar 1 includes multiple emission cycles in one measurement. In each emission cycle, each of the M power pulse width modulated vertical cavity surface emitting lasers 101 emits Y detection lasers, where M≤N and M is a positive integer, and N is a positive integer greater than 1. It can be understood that the laser emitting unit 10 activates each vertical cavity surface emitting laser 101 in a time-sharing manner, and each time any one vertical cavity surface emitting laser 101 or multiple vertical cavity surface emitting lasers 101 in the N vertical cavity surface emitting lasers 101 is activated, see Figure 4 , time-sharing activation control can be performed through the control circuit 102 built into the laser emitting unit 10, such as a circuit based on a multi-channel selection signal. And in order to achieve complete splicing of the emission field of view, the total number of vertical cavity surface emitting lasers 101 that emit detection lasers in all emission cycles should be equal to the number of vertical cavity surface emitting lasers 101 contained in the laser emitting unit 10. Assuming that a measurement includes three emission cycles, and the number of vertical cavity surface emitting lasers 101 activated in the three emission cycles are M1, M2 and M3 respectively, then M1+M2+M3=N. If only one vertical cavity surface emitting laser 101 is activated to perform Y detection laser emissions in each emission cycle, then N emission cycles are required in a measurement. That is, there are S emission cycles in a measurement, S≥1, and the number of vertical cavity surface emitting lasers 101 activated in each emission cycle is Mi ,but

[0046]

[0047] The number of times the detection laser is emitted in each emission cycle, Y, is calculated and determined based on the preset radar detection conditions according to the lidar equation. Taking the SPADs detection capability reaching the single-photon level, the photon detection efficiency close to 40% @ 905nm (905nm wavelength, 40% photon detection efficiency), the false alarm rate of 1%, and the detection probability of 90% as an example, a single measurement needs to achieve a signal-to-noise ratio of 23. Taking into account the influence of dark counts and other noise, each detection requires 30 photons to be detected. Then, under the detection conditions of 200m @ 10% @ 100kLux (200-meter distance, 10% reflectivity, 100kLux ambient light), substituting it into the lidar equation for solution, it is determined that a 120W 10ns laser is required, covering 32 pixels, and the number of integrations must reach more than 3 times to meet the radar detection conditions. The number of integrations calculated will vary depending on the different radar detection requirements. Since the lidar equation is a conventional equation, its solution steps will not be repeated here.

[0048] At the same time, in order to increase the signal dynamic range in a TCSPC and improve the problem of missing short-range reflectivity signals in long-distance ranging, multiple emission parameter ranges are preset in this embodiment. Each emission parameter range limits the range of emission power and emission pulse width of the detection laser emitted by the vertical cavity surface emitting laser 101, including a low-power short pulse width range, a high-power short pulse width range and a high-power long pulse width range. Optionally, the low-power short pulse width range is a power belonging to [5W, 25W] and a pulse width belonging to [1ns, 3ns], the high-power short pulse width range is a power belonging to [60W, 180W] and a pulse width belonging to [1ns, 3ns], and the high-power long pulse width range is a power belonging to [60W, 180W] and a pulse width belonging to [9ns, 11ns]. Of the Y probe lasers emitted in each emission cycle, at least one has emission parameters selected from the low-power, short-pulse-width range, at least one has emission parameters selected from the high-power, short-pulse-width range, and at least one has emission parameters selected from the high-power, long-pulse-width range. Therefore, Y cannot be less than 3. Taking into account the aforementioned radar detection requirements for the number of integrations and the emission parameter range, in this embodiment, the value of Y should be greater than or equal to 3.

[0049] From the above description, it can be seen that when all the VCSELs 101 are activated, that is, M=N, the high reflectivity of the target object at a close distance will cause the number of photons received by the SPADs to exceed the limit, but when the M value is too large, that is, M>N / 2, M VCSELs 101 simultaneously emit detection lasers, and their echo signals may overlap in the laser receiving unit 20 due to lens distortion or scattering, resulting in signal interference between the pixels of the SPADs. Therefore, in a preferred embodiment, the number of lasers activated each time is set to be less than or equal to half of the number of VCSELs 101 in the laser emitting unit 10, that is, M≤N / 2.

[0050] Taking the number of emission times Y=5 as an example, in one emission cycle, the laser emission unit 10 will emit five detection lasers. In order to meet the requirements of the emission parameter range, please refer to Figure 5 During the first emission, (20W peak power, 2ns pulse width) were selected from the low-power short pulse width range as the emission parameters of the vertical cavity surface emitting laser 101. During the second emission, (120W peak power, 2ns pulse width) were selected from the high-power short pulse width range as the emission parameters of the vertical cavity surface emitting laser 101. For the third, fourth and fifth emissions, a probe laser with (180W peak power, 10ns pulse width) was used, that is, the emission parameters were selected from the high-power long pulse width range.

[0051] There is a time interval between multiple emissions of the vertical cavity surface emitting laser 101, and the time interval between each pulse emission differs by 1us to 3us. The SPADs of the laser receiving unit 20 is a nonlinear device and has a dead time. After responding to the echo signal, the SPADs will no longer respond to other echo signals within the dead time, and the responses of the SPADs to signals with different pulse widths and power are also different. If the SPADs work in the linear region for each echo, the rising edge of the SPADs signal is approximately equal to the pulse width of the emitted laser, and the falling edge is approximately the sum of the dead times of all activated SPADs. After each laser emission is completed, the number of photons received by each pixel of the SPADs is counted, and the results are recorded in the memory unit and accumulated. Taking the above-mentioned number of emissions and emission power pulse width as an example, the statistical results of the number of SPADs photons corresponding to five different pulse widths and different powers are as follows: Figure 6 shown.

[0052] Assume that the target is at a close distance, such as about 5 meters. At this time, the first low-power short-pulse detection laser emitted has an echo signal. The second to fifth detection lasers are saturated and close to a rectangular shape. The several pulses in a measurement are correlated and accumulated. The echo signal received by SPADs is as follows: Figure 7As shown in the figure, the flight time is determined based on the peak value of the echo signal, and thus the distance can be calculated. It can be seen that the echo signal has a linear region at the top, that is, there is a linear energy echo. Assuming that the target is at a long distance, such as about 100m, the first and second emission detection lasers have insufficient pulse width and power, and the SPADs have difficulty receiving the echo signal. Only the emission signal (180W peak power, 10ns pulse width) has an echo signal, as shown in the figure. Figure 8 As shown in the figure, the third, fourth and fifth echo signals are all small, that is, the echo signals received by SPADs also have a linear relationship. Therefore, the distance can be measured based on the echo signal, and the reflectivity information can also be inferred from the pulse width information.

[0053] This embodiment increases the signal dynamic range in a TCSPC by modulating the transmission power and pulse width of the laser radar pulse at each transmission, thereby ensuring that there is a linear energy echo within the full dynamic range. The linear energy echo represents the intensity of the echo signal. Since the reflectivity of the radar is proportional to the echo power, the linear energy echo is directly related to the radar reflectivity. Therefore, the reflectivity signal at close range can be inferred based on the pulse width signal in the linear region. It can be seen that the SPADs laser radar provided by the present invention overcomes the problem of missing reflectivity signal in conventional SPADs laser radars during short-range ranging, thereby enabling the SPADs laser radar to have higher accuracy in ranging at both long and short distances.

[0054] In a preferred embodiment, in order to further improve the accuracy of laser radar measurement, during a measurement process, the laser emitting unit 10 can also adjust the power and pulse width of the detection laser emitted each time through a step gain. Specifically, the multiple measurements included in a ranging process can be divided into initial measurement and non-initial measurement according to the measurement order. When a measurement is an initial measurement, multiple laser emissions are performed according to the emission parameter range of the above embodiment. The SPADs perform preliminary calculations based on the response waveform of the echo signal to obtain a preliminary ranging distance to the target. Although the accuracy of the ranging distance is not high, the distance of the target can be determined based on the ranging distance, such as whether it is at a long distance or a short distance. Based on the ranging distance measured initially, in subsequent non-initial measurements, the emission parameters of the detection laser emitted in each emission cycle are determined based on a preset step gain. The step gain is a correspondence between the emission power and emission pulse width of the preset vertical cavity surface emitting laser and the ranging distance: the power and pulse width of the VCSEL are divided into S steps, each step corresponding to a different power and a different pulse width.

[0055] Taking S=3 as an example, it is divided into short-range, medium-range and long-range gears. Among them, low power (such as 10W) ​​and short pulse width (such as 2ns) are used for short-range (such as 0-20m) to suppress signal overload; medium-range power (such as 30W) and medium pulse width (such as 8ns) are used for medium-range (such as 20-50m) to balance signal strength and noise; high power (such as 100W) and long pulse width (such as 10ns) are used for long-range (such as 50m and above) to improve detection capability. According to the ranging distance during the initial measurement, the power and pulse width emitted during the next measurement are determined according to the graded gain. During the non-initial measurement process, the power and pulse width of the detection laser emitted multiple times can be emitted according to the graded gain, fixed power and fixed pulse width, so as to obtain a more stable echo signal and achieve high-precision measurement.

[0056] The hybrid solid-state lidar provided by the present invention designs the number of transmissions, transmission power, and transmission pulse width for a single measurement. On this basis, when the SPADs superimpose the echo signals of multiple measurements, they still use the conventional time-correlated accumulation method to achieve high-precision ranging of the lidar. It should be noted that in the present invention, the number of transmissions in a single measurement process, as well as the power and pulse width of each transmission, can be flexibly set based on the radar ranging requirements and detection conditions, as well as different application scenarios. The above embodiment is only intended as a preference and not a specific limitation.

[0057] This embodiment provides a hybrid solid-state laser radar with increased signal dynamic range. Based on the architecture of a conventional SPADs laser radar, the present invention dynamically adjusts the emission parameters within a single ranging cycle, expands the signal dynamic range in the TCSPC process, and simultaneously suppresses close-range saturation and improves long-range sensitivity without increasing hardware complexity and accumulation times. This ensures that the SPADs laser radar can receive relatively linear energy echoes within the full dynamic range, overcomes the problem of missing close-range reflectivity signals caused by parameter fixation of traditional SPADs laser radars, and enables the SPADs laser radar to not only have higher accuracy in long-range ranging, but also maintain measurement accuracy in close-range ranging, providing a new technical path for high-reliability perception in complex scenarios.

[0058] See also Figure 9 Based on the same inventive concept, a second embodiment of the present invention proposes a control method for a hybrid solid-state laser radar with increased signal dynamic range. Optionally, the control method is used to control the hybrid solid-state laser radar with increased signal dynamic range in the above embodiment. The control method includes steps S10 to S30:

[0059] Step S10, the laser emitting unit performs at least one emission cycle in one measurement, and in each emission cycle, each vertical cavity surface emitting laser of M power pulse width modulated vertical cavity surface emitting lasers emits Y detection lasers, wherein the laser emitting unit includes N power pulse width modulated vertical cavity surface emitting lasers, N>1, M≤N, M is a positive integer, Y≥3, and the total number of vertical cavity surface emitting lasers that emit detection lasers in the cumulative emission cycle is equal to N, and among the Y detection lasers emitted in each emission cycle, the emission parameters of at least one detection laser are selected from the low power short pulse width range, the emission parameters of at least one detection laser are selected from the high power short pulse width range, and the emission parameters of at least one detection laser are selected from the high power long pulse width range;

[0060] Step S20, reflecting the detection laser to the polygonal rotating mirror through the transmitting reflector, and reflecting the detection laser through the polygonal rotating mirror to form a detection scanning light;

[0061] Step S30: receiving the echo signal generated by the detection scanning light scanning the target object through the polygonal rotating mirror, and reflecting the echo signal to the receiving reflector, and reflecting the echo signal to the laser receiving unit through the receiving reflector to complete one measurement.

[0062] In a preferred embodiment, the control method further includes:

[0063] Determining a measurement sequence type of the one measurement, where the measurement sequence type includes an initial measurement and a non-initial measurement;

[0064] In response to the measurement sequence type being an initial measurement, among the Y detection lasers emitted in each emission cycle, emission parameters of at least one detection laser are selected from a low-power short-pulse-width range, emission parameters of at least one detection laser are selected from a high-power short-pulse-width range, and emission parameters of at least one detection laser are selected from a high-power long-pulse-width range;

[0065] In response to the measurement sequence type being non-initial measurement, the emission parameters of the Y detection lasers emitted in each emission cycle are determined based on a preset step gain, where the step gain is the correspondence between the emission parameters of the vertical cavity surface emitting laser and the ranging distance, and the ranging distance is obtained by calculating the echo signal of the initial measurement by the laser receiving unit.

[0066] The technical features and technical effects of the control method of the hybrid solid-state laser radar for increasing the signal dynamic range proposed in the embodiment of the present invention are the same as those of the hybrid solid-state laser radar proposed in the embodiment of the present invention, and will not be repeated here.

[0067] In summary, an embodiment of the present invention proposes a hybrid solid-state laser radar and a control method for increasing the dynamic range of a signal. The hybrid solid-state laser radar includes: a laser emitting unit, a laser receiving unit, a transmitting reflector, a receiving reflector and a polygonal rotating mirror. The laser emitting unit includes N vertical cavity surface emitting lasers with modulated power pulse width, and the laser receiving unit is a single photon avalanche diode array sensor; the laser emitting unit and the transmitting reflector are arranged on one side of the polygonal rotating mirror, and form a laser output optical path structure with the polygonal rotating mirror. A laser receiving unit and a receiving reflector are also arranged on the same side of the polygonal rotating mirror, and the laser receiving unit, the receiving reflector and the polygonal rotating mirror form a laser incident optical path. Structure; the laser emitting unit performs at least one emission cycle in one measurement, and in each emission cycle, each vertical cavity surface emitting laser of M power pulse width modulated vertical cavity surface emitting lasers emits Y detection lasers, wherein N>1, M≤N, M is a positive integer, Y≥3, and the total number of vertical cavity surface emitting lasers emitting detection lasers in the cumulative emission cycle is equal to N; among the Y detection lasers emitted in each emission cycle, the emission parameters of at least one detection laser are selected from the low power short pulse width range, the emission parameters of at least one detection laser are selected from the high power short pulse width range, and the emission parameters of at least one detection laser are selected from the high power long pulse width range. Based on the architecture of a conventional hybrid solid-state lidar using single-photon avalanche diode technology, the present invention dynamically adjusts the emission parameters within a single ranging cycle, expands the signal dynamic range in the TCSPC process, and simultaneously suppresses close-range saturation and improves long-range sensitivity without increasing hardware complexity and accumulation times. This ensures that the SPADs lidar can receive relatively linear energy echoes within the full dynamic range, overcomes the problem of missing close-range reflectivity signals caused by parameter fixation of traditional SPADs lidar, and enables the SPADs lidar to not only have higher accuracy in long-range ranging, but also maintain measurement accuracy in close-range ranging, providing a new technical path for high-reliability perception in complex scenarios.

[0068] Each embodiment in this specification is described in a progressive manner, and the same or similar parts of each embodiment can be directly referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment. It should be noted that the various technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] The above-described embodiments merely represent several preferred implementations of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art could make several improvements and substitutions without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be based on the scope of protection of the claims.

Claims

1. A hybrid solid-state laser radar with increased signal dynamic range, characterized in that: include: A laser emitting unit, a laser receiving unit, a transmitting reflector, a receiving reflector and a polyhedron rotating mirror, wherein the laser emitting unit includes N vertical cavity surface emitting lasers with modulated power pulse width, and the laser receiving unit is a single photon avalanche diode array sensor; The laser emitting unit and the emitting reflective mirror are arranged on one side of the polygonal rotating mirror, and together with the polygonal rotating mirror, form a laser emission optical path structure. The laser receiving unit and the receiving reflective mirror are also arranged on the same side of the polygonal rotating mirror, and the laser receiving unit, the receiving reflective mirror and the polygonal rotating mirror form a laser incident optical path structure. The laser emitting unit performs at least one emission cycle in one measurement. In each emission cycle, each of M vertical cavity surface emitting lasers with modulated power pulse width emits Y detection lasers, where N>1, M≤N, M is a positive integer, Y≥3, and the total number of vertical cavity surface emitting lasers that emit detection lasers in the cumulative emission cycle is equal to N; Among the Y detection lasers emitted in each emission cycle, the emission parameters of at least one detection laser are selected from the low power short pulse width range, the emission parameters of at least one detection laser are selected from the high power short pulse width range, and the emission parameters of at least one detection laser are selected from the high power long pulse width range.

2. The hybrid solid-state laser radar with increased signal dynamic range according to claim 1, characterized in that: The N vertical cavity surface emitting lasers are arranged in a vertical linear array.

3. The hybrid solid-state laser radar with increased signal dynamic range according to claim 1, characterized in that: The plurality of reflecting surfaces of the polyhedron rotating mirror are arranged in a manner that the circumference of the circumscribed circle of the cross section of the polyhedron rotating mirror is equally divided.

4. The hybrid solid-state laser radar with increased signal dynamic range according to claim 1, characterized in that: The N value is determined by the preset line number of the laser radar and the number of pixels covered by the vertical cavity surface emitting laser.

5. The hybrid solid-state laser radar with increased signal dynamic range according to claim 1, characterized in that: Said M≤N / 2.

6. The hybrid solid-state laser radar with increased signal dynamic range according to claim 1, characterized in that: The Y value is determined by calculating the preset radar detection conditions according to the laser radar equation.

7. The hybrid solid-state laser radar with increased signal dynamic range according to claim 1, characterized in that: An emission focusing and collimating unit is provided between the laser emission unit and the emission reflector, and a reception focusing and collimating unit and a filter unit are provided in sequence between the laser reception unit and the reception reflector.

8. A control method for a hybrid solid-state laser radar for increasing the signal dynamic range, characterized in that: include: The laser emitting unit performs at least one emission cycle in one measurement, and in each emission cycle, each of M vertical cavity surface emitting lasers with modulated power and pulse width emits Y detection lasers, wherein the laser emitting unit includes N vertical cavity surface emitting lasers with modulated power and pulse width, N>1, M≤N, M is a positive integer, Y≥3, and the total number of vertical cavity surface emitting lasers that emit detection lasers in a cumulative emission cycle is equal to N, and among the Y detection lasers emitted in each emission cycle, the emission parameters of at least one detection laser are selected from a low-power short-pulse-width range, the emission parameters of at least one detection laser are selected from a high-power short-pulse-width range, and the emission parameters of at least one detection laser are selected from a high-power long-pulse-width range; Reflecting the detection laser to the polygonal rotating mirror through the transmitting reflector, and reflecting the detection laser through the polygonal rotating mirror to form a detection scanning light; The echo signal generated by the detection scanning light scanning the target object is received by the polygonal rotating mirror, and the echo signal is reflected to the receiving reflector, and the echo signal is reflected to the laser receiving unit by the receiving reflector to complete a measurement.

9. The control method for a hybrid solid-state laser radar with increased signal dynamic range according to claim 8, characterized in that: The control method further includes: Determining a measurement sequence type of the one measurement, where the measurement sequence type includes an initial measurement and a non-initial measurement; In response to the measurement sequence type being an initial measurement, among the Y detection lasers emitted in each emission cycle, emission parameters of at least one detection laser are selected from a low-power short-pulse-width range, emission parameters of at least one detection laser are selected from a high-power short-pulse-width range, and emission parameters of at least one detection laser are selected from a high-power long-pulse-width range; In response to the measurement sequence type being non-initial measurement, the emission parameters of the Y detection lasers emitted in each emission cycle are determined based on a preset step gain, where the step gain is the correspondence between the emission parameters of the vertical cavity surface emitting laser and the ranging distance, and the ranging distance is obtained by calculating the echo signal of the initial measurement by the laser receiving unit.

Images