A laser radar

Abstract

The present invention discloses a laser radar, including a laser, a telescope and a four-quadrant shading mechanism; the four-quadrant shading mechanism includes a four-quadrant shading plate, a rotating mechanism and a control system; the four-quadrant shading plate is installed on the lens barrel of the telescope, located above the receiving light window of the telescope, and includes four shading plates, which are respectively used to block the four partitions of the receiving light window, and the four partitions are divided by two mutually perpendicular diameters of the receiving light window to form four quadrants; the rotating mechanism connects the four-quadrant shading plates, and controls the rotation of the four shading plates respectively, and opens and closes independently; the control system is used to control the operating state of the rotating mechanism to realize the alignment of the receiving and transmitting light axis. The laser radar of the present invention can use the uniformity detection of the received signals of the four quadrants of the telescope to complete the calibration task of its transmitting light axis and the receiving light axis, and can realize the automatic alignment of the receiving and transmitting light axis of the laser radar in an unattended situation.

Description

Technical Field

[0001] The invention belongs to the technical field of detection equipment, and in particular, relates to a laser radar. Background Art

[0002] Lidar is an active remote sensing monitoring device with advantages such as high temporal and spatial resolution and high measurement accuracy. In the Lidar system, the alignment of the transmitting and receiving optical axes is the key to ensuring the efficiency of Lidar signal reception. In the actual operation of Lidar, temperature changes, environmental vibrations, laser jitter and other reasons may cause the transmitting optical axis of the laser to deviate from the receiving optical axis of the telescope, resulting in a decrease in the efficiency of the received signal and signal distortion. Therefore, it is necessary to calibrate the receiving and receiving optical axes of the Lidar regularly. The so-called alignment of the transmitting and receiving optical axes, for rangefinder Lidar, is to make the transmitting optical axis parallel to the receiving optical axis; for coaxial Lidar, it is to make the transmitting optical axis coaxial with the receiving optical axis.

[0003] There are two main methods for calibrating the laser radar’s receiving and transmitting light axis: manual calibration and automatic calibration. Among them, manual calibration is the most common alignment method, but it requires the operator to have a certain professional background and experience in optical path adjustment, and the adjustment process is cumbersome and time-consuming. The alignment accuracy adjusted by visual inspection data is also difficult to guarantee.

[0004] The automatic calibration method currently basically uses a two-dimensional electrically controlled reflector to adjust the direction of the emitted light beam. There are two main commonly used methods:

[0005] One is that when the transmitting optical axis is aligned with the receiving optical axis, the laser beam is first passed through a beam splitter with a high transmission-reflection ratio (transmission: reflection) before being emitted into the atmosphere, and a small portion of the light is reflected as the reference light; then, the reference light is incident on a fixed photodetector, and the detector marks this position as the position of the optical axis alignment. When the transmitting optical axis deviates, the position of the reference light on the photodetector will also deviate. At this time, the angle of the reflector can be adjusted by the electrically controlled reflector frame, and then the direction of the emitted light can be adjusted so that the position of the reference light on the photodetector is just adjusted to the marked alignment position, thereby completing the calibration operation. However, this method has the problem of misjudgment of the misalignment of the optical axis due to the deviation of the beam splitter.

[0006] Another method is to adjust the emission laser through the two-dimensional electric-controlled reflector frame to scan along the two mutually perpendicular diameter directions of the telescope, select a certain height as the reference height, observe the change of the reference height signal during the scanning process, and take the position with the largest reference height receiving signal as the best position in the two directions to determine the alignment of the emission optical axis and the receiving optical axis. However, this method is greatly affected by the laser motion trajectory and the reference height. Summary of the invention

[0007] It has been found through experiments that the calibration of the receiving and transmitting light axis of the laser radar can also be achieved by detecting the uniformity of the received signals in the four quadrants of the laser radar telescope. For this purpose, the present invention proposes a laser radar with an improved structure. By designing a four-quadrant shading mechanism on the laser radar telescope, the telescope can be controlled to independently receive atmospheric echo signals in the four quadrants, and the direction of the transmitting light axis can be adjusted by comparing the signals in the centrally symmetrical quadrants, thereby achieving automatic calibration of the receiving and transmitting light axis.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0009] A laser radar comprises a laser for emitting a laser beam, a reflector for emitting the laser beam into the atmosphere, an adjustable electrically controlled mirror frame on which the reflector is mounted, a telescope, a receiving optical path system and a four-quadrant shading mechanism; the adjustable electrically controlled mirror frame is used to adjust the angle or position of the reflector to change the emission direction of the laser beam into the atmosphere, wherein the emission direction is the direction of the laser radar emission optical axis; the telescope comprises a lens barrel, in which a receiving light window is arranged, for receiving an echo signal after the laser beam is emitted into the atmosphere; the receiving optical path system converts the echo signal received by the telescope into an electrical signal; the four-quadrant shading mechanism comprises a four-quadrant shading plate, a rotating mechanism and a control system; wherein the four-quadrant shading plate is mounted at the On the lens barrel of the telescope, located above the receiving light window, it includes four shading plates, which are respectively used to block the four partitions of the receiving light window, and the four partitions are divided by two mutually perpendicular diameters of the receiving light window to form four quadrants; the rotating mechanism is connected to the four quadrant shading plates, and controls the rotation of the four shading plates respectively, and opens and closes independently; when calibrating the transmitting optical axis and the receiving optical axis, the control system controls the rotating mechanism to drive the four shading plates to open only in different time periods, and receives the electrical signals of the four quadrants of the telescope through the receiving optical path system, and controls the adjustable electrically controlled mirror frame to adjust the reflector according to the electrical signal, thereby adjusting the emission direction of the laser light beam, so that the receiving and transmitting light axis of the laser radar is collimated.

[0010] In some embodiments of the present application, among the four quadrants, it is preferred to define that the first quadrant is centrally symmetrical with the second quadrant, and the third quadrant is centrally symmetrical with the fourth quadrant; when the laser radar is calibrating the transmitting optical axis and the receiving optical axis, the control system takes the shielding plates corresponding to the first quadrant and the second quadrant as a group, and controls the two shielding plates to be opened in a time-sharing and unique manner through the rotating mechanism, so that the telescope receives the echo signal separately through its first quadrant and the second quadrant respectively, and collects the receiving signals of the first quadrant and the second quadrant through the receiving optical path system; the control system controls the movement of the adjustable electrically controlled mirror frame according to the receiving signals of the first quadrant and the second quadrant, so as to adjust the transmitting and receiving optical axes of the laser radar. The transmitting optical axis is tilted toward the quadrant with a small receiving signal until the receiving signal in the first quadrant is equivalent to the receiving signal in the second quadrant; the control system takes the shielding plates corresponding to the third and fourth quadrants as a group, and controls the two shielding plates to be opened in a time-sharing and unique manner through the rotating mechanism, so that the telescope receives echo signals through its third and fourth quadrants respectively, and collects the receiving signals of the third and fourth quadrants through the receiving optical path system; the control system controls the movement of the adjustable electric-controlled mirror frame according to the receiving signals of the third and fourth quadrants, so as to adjust the transmitting optical axis of the laser radar to tilt toward the quadrant with a small receiving signal until the receiving signal in the third quadrant is equivalent to the receiving signal in the fourth quadrant. Thus, the calibration process of the receiving and receiving optical axis is completed.

[0011] In some embodiments of the present application, when the laser radar is a rangefinder laser radar, the four quadrants are further defined to satisfy the following relationship in a virtual rectangular coordinate system: the virtual rectangular coordinate system is established in the plane where the receiving light window of the telescope is located, wherein the origin of the virtual rectangular coordinate system is the center of the receiving light window, and the y-axis passes through the center of the laser beam emitted by the laser radar to the atmosphere when the receiving and receiving light axes are collimated; the first quadrant and the second quadrant are respectively axially symmetric regions with respect to the x-axis of the virtual rectangular coordinate system; the third quadrant and the fourth quadrant are respectively axially symmetric regions with respect to the y-axis of the virtual rectangular coordinate system.

[0012] In some embodiments of the present application, when the transmitting optical axis and the receiving optical axis are calibrated and the laser radar enters normal operation, the control system controls the rotating mechanism to drive all four shading plates to open, and uses the entire receiving light window of the telescope to receive the echo signal.

[0013] In some embodiments of the present application, the laser radar also has the ability to collect its own background signal, that is, when the laser radar obtains the background signal, it controls the rotation mechanism to drive the four shading plates to close; the receiving optical path system collects the optical signal received by the telescope and generates a corresponding electrical signal as the background signal. The background signal can be used as an indicator for evaluating the performance of the laser radar.

[0014] In some embodiments of the present application, the four-quadrant shading mechanism further includes a support plate, which is mounted on the lens barrel of the telescope, forming a bearing surface above the lens barrel, and the rotating mechanism is mounted on the bearing surface of the support plate. By designing the support plate, the installation and overall disassembly of the rotating mechanism on the telescope can be facilitated.

[0015] In some embodiments of the present application, the rotating mechanism is preferably arranged in four groups, which are respectively connected to the four sunshade panels, and each group of the rotating mechanism includes a rotating shaft, a positioning seat, a motor, a driving wheel and a driven wheel; wherein the rotating shaft is connected to one of the sunshade panels; the positioning seat is installed on the bearing surface of the support plate, on which a bearing is installed, and the rotating shaft is installed in the bearing; the motor is installed on the support plate, and its operating state is controlled by the control system; the driving wheel is connected to the motor shaft and driven to rotate by the motor; the driven wheel is meshed with the driving wheel and connected to the rotating shaft, and when the motor drives the driving wheel to rotate, the driving wheel drives the driven wheel to rotate, thereby driving the sunshade panels to open and close.

[0016] In some embodiments of the present application, the motor is preferably installed below the bearing surface of the support plate, and the driving shaft of the motor extends through the bearing surface to above the bearing surface and is connected to the driving wheel shaft. The axis of the driving wheel is preferably designed to be perpendicular to the axis of the driven wheel so that the rotating shaft can be arranged parallel to the receiving light window of the telescope, thereby realizing a large-area connection between the rotating shaft and the sunshade, which helps to improve the smoothness of the opening and closing process of the sunshade.

[0017] In some embodiments of the present application, the four groups of rotating mechanisms are disposed on the four sides of the bearing surface of the support plate; in each group of rotating mechanisms, the rotating shaft is parallel to the bearing surface of the support plate; the positioning seats each include two, which are disposed at both ends of the rotating shaft, and the supporting force of the positioning seats on the rotating shaft and the sunshade is increased to further ensure the stability of the opening and closing process of the sunshade.

[0018] In some embodiments of the present application, the laser radar further includes a beam expander and a launch system carrier; wherein the beam expander is used to compress the divergence angle of the laser beam emitted by the laser and then emit it to the reflector; the launch system carrier is installed on the barrel of the telescope, located on one side of the telescope; the laser, beam expander, reflector and adjustable electrically controlled mirror frame can all be installed on the launch system carrier to facilitate the overall structural design of the laser radar, thereby facilitating the overall movement and handling of the laser radar. By adjusting the adjustable electrically controlled mirror frame, the laser radar can be configured as a coaxial laser radar or a paraxial laser radar.

[0019] In some embodiments of the present application, the control system preferably includes an acquisition card, an industrial computer and a drive circuit; wherein the acquisition card is used to acquire the electrical signal output by the receiving optical path system and convert it to generate a digital signal; the industrial computer receives the digital signal output by the acquisition card and generates control signals for controlling the rotation mechanism and the adjustable electric-controlled mirror frame respectively; the drive circuit receives the control signal output by the industrial computer to drive the rotation mechanism or the adjustable electric-controlled mirror frame to move. Thus, the laser radar has the function of automatically calibrating the receiving optical axis and the transmitting optical axis.

[0020] Compared with the prior art, the advantages and positive effects of the present invention are as follows: the laser radar of the present invention designs a four-quadrant shading mechanism on its telescope, so that the receiving light window of the telescope can receive the atmospheric echo signal in its four quadrant areas respectively. When the four quadrant shading plates of the telescope are all opened, the laser radar can work normally; when the four quadrant shading plates are all closed, the laser radar can collect background signals; when the laser radar calibrates the transmitting optical axis and the receiving optical axis, the atmospheric echo signals of the four quadrants can be used to provide an adjustment basis for the direction of the laser radar transmitting optical axis. When the atmospheric echo signals of the two groups of quadrants with central symmetry are basically the same, the alignment of the laser radar receiving and transmitting optical axis is achieved. The laser radar of the present invention uses the uniformity detection of the receiving signals of the four quadrants of the telescope to realize the calibration of the laser radar transmitting optical axis and the receiving optical axis. The method is simple and easy to use, which helps to improve the working efficiency and convenience of the laser radar. It can realize the automatic alignment of the receiving and transmitting optical axis in an unattended situation, and can realize the collection of the laser radar background signal, providing a basis for its performance evaluation.

[0021] Other features and advantages of the present invention will become more apparent after reading the detailed description of the embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 A schematic diagram of the overall structure of an embodiment of the laser radar proposed by the present invention;

[0024] Figure 2 for Figure 1 A structural schematic diagram of an embodiment of a four-quadrant shading mechanism;

[0025] Figure 3A schematic diagram of a corresponding relationship between the four-quadrant division of a telescope of a rangefinder laser radar and the position of a laser beam emitted into the atmosphere in one embodiment;

[0026] Figure 4 A flowchart of an embodiment of a laser radar receiving and transmitting light axis calibration process. DETAILED DESCRIPTION

[0027] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0028] It should be noted that in the description of the present invention, the terms "upper", "lower", "inner", "outer" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings, which are only for the convenience of description, and do not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore, cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third" and "fourth" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0029] like Figure 1 As shown, the laser radar of this embodiment mainly includes two parts: a laser emission system 10 and an optical receiving system. The laser emission system 10 mainly includes a laser 11, a beam expander 12, a reflector 13, an adjustable electrically controlled mirror frame 14 and other parts. The optical receiving system mainly consists of a telescope 20 and a subsequent receiving optical path system 23.

[0030] In order to facilitate the integration of the laser emitting system 10 and the optical receiving system so that the laser radar can be easily moved or transported as a whole, the laser emitting system 10 is preferably installed on a emitting system carrier board 15 in this embodiment. Figure 1 As shown. Among them, the laser 11 is preferably installed in a downward position of the launch system carrier 15, for emitting a laser beam. The beam expander 12 is located above the laser 11, and is used to compress the divergence angle of the laser beam emitted by the laser 11 to form a laser beam with a certain diameter, and to be incident on the reflector 13. The reflector 13 can be one or more, and is installed on an adjustable electrically-controlled mirror frame 14, and is used to reflect the laser beam incident thereon and emit it into the atmosphere. The angle or position of the reflector 13 can be adjusted by using the adjustable electrically-controlled mirror frame 14, thereby changing the emission direction of the laser beam into the atmosphere.

[0031] The launch system carrier 15 is mounted on the telescope 20, preferably on the lens barrel 21 of the telescope 20, and is located on one side of the telescope 20, such as Figure 1By controlling the adjustable electrically controlled mirror frame 14 to appropriately adjust the angle or position of the reflector 13, the emission direction of the laser beam (i.e., the emission optical axis direction of the laser radar) is parallel to the receiving optical axis of the telescope 20, and a side-axis laser radar can be formed; if the emission direction of the laser beam is adjusted to be coaxial with the receiving optical axis of the telescope 20, a coaxial laser radar can be formed. Figure 1 If the laser radar structure shown in the figure forms a coaxial laser radar, it can be Figure 1 A set of reflectors is added to the laser radar structure shown.

[0032] A light receiving window 22 is provided in the lens barrel 21 of the telescope 20. Figure 1 , Figure 3 As shown. Under normal circumstances, the receiving light window 22 is circular, receives the echo signal after the laser beam 16 enters the atmosphere, and collects it to the subsequent receiving optical path system 23 to convert the optical signal into an electrical signal. The size of the electrical signal can reflect the intensity of the received optical signal. According to the electrical signal output by the receiving optical path system 23, the target at a predetermined height can be detected using the existing radar signal detection method.

[0033] Considering that in the laser radar system, the alignment of the transmitting and receiving optical axes is the key to ensuring the efficiency of laser radar signal reception, it is necessary to calibrate the transmitting and receiving optical axes of the laser radar. Experiments have shown that uniformity detection of the received signals in the four quadrants of the laser radar telescope is a way to achieve calibration of the receiving and receiving optical axes of the laser radar. In order to apply this calibration method to the laser radar of this embodiment, this embodiment first improves the structure of the existing laser radar and adds a four-quadrant shading mechanism 30 to divide the receiving light window 22 of the telescope 20 into four areas to form four quadrants for independently receiving atmospheric echo signals, thereby meeting the uniformity detection requirements of the received signals in the four quadrants.

[0034] Combination Figure 1 , Figure 2 As shown, the four-quadrant shading mechanism 30 of this embodiment is mainly composed of a four-quadrant shading plate, a rotating mechanism and a control system.

[0035] In this embodiment, the four-quadrant shading plate is preferably installed on the lens barrel 21 of the telescope 20 and is located above the receiving light window 22, and preferably includes four shading plates 31, 32, 33, and 34. Figure 2 The four shading plates 31, 32, 33, 34 can be designed to be in the same shape, such as a triangle-like shape, and can completely cover the receiving light window 22 of the telescope 20 after being assembled.

[0036] The four shielding areas formed by configuring four shading plates 31, 32, 33, 34 on the receiving light window 22 of the telescope 20 coincide with the four partitions formed by two mutually perpendicular diameters of the receiving light window 22. Figure 3 As shown, the light receiving window 22 is then divided into four quadrants. The first quadrant I is shielded by the shielding plate 31; the second quadrant II is shielded by the shielding plate 32; the third quadrant III is shielded by the shielding plate 33; and the fourth quadrant IV is shielded by the shielding plate 34. The first quadrant I is configured to be centrally symmetrical with the second quadrant II, and the third quadrant III is configured to be centrally symmetrical with the fourth quadrant IV.

[0037] For coaxial laser radar, the positional relationship of the four quadrants only needs to meet the above configuration requirements.

[0038] For the rangefinder laser radar, the positional relationship of the four quadrants needs to be further restricted in addition to meeting the above configuration requirements. Specifically, a virtual rectangular coordinate system can be established on the plane where the receiving light window 22 of the telescope is located, such as Figure 3 As shown, the origin of the virtual rectangular coordinate system is the center O of the receiving light window 22, and the y-axis passes through the center O' of the laser beam 16 emitted to the atmosphere by the laser radar when the receiving and receiving light axes are aligned. According to the principle of two points determining a straight line, the direction of the y-axis can be determined by using the center O of the receiving light window 22 and the center O' of the laser beam 16, and then the direction of the x-axis can be determined. When performing area division, the first quadrant I and the second quadrant II are configured to be axisymmetric areas about the x-axis of the virtual rectangular coordinate system (for the circular receiving light window 22, that is, the sectors corresponding to the first quadrant I and the second quadrant II are axisymmetric figures about the x-axis); the third quadrant III and the fourth quadrant IV are configured to be axisymmetric areas about the y-axis of the virtual rectangular coordinate system (for the circular receiving light window 22, that is, the sectors corresponding to the third quadrant III and the fourth quadrant IV are axisymmetric figures about the y-axis).

[0039] In order to facilitate the installation and fixation of the four-quadrant shading plate on the lens barrel 21 of the telescope 20, in this embodiment, the four-quadrant shading plate is preferably first installed on a support plate 35, such as Figure 2 The support plate 35 is preferably designed in a ring shape, and the middle opening area faces the receiving light window 22 of the telescope 20. Four light shielding plates 31, 32, 33, and 34 are sequentially arranged circumferentially on the bearing surface formed by the support plate 35, and after being assembled, they shield the middle opening area of ​​the support plate 35.

[0040] Preferably, a lower flange 36 is formed on the support plate 35 . Two lower flanges 36 may be provided, formed on two opposite sides of the support plate 35 ; or four lower flanges 36 may be provided, formed around the support plate 35 .

[0041] During installation, the support plate 35 is placed on the upper edge of the lens barrel 21 of the telescope 20, and the lower flange 36 of the support plate 35 is at least partially in contact with the side wall of the lens barrel 21. Figure 1 The lower flange 36 is threadedly connected to the side wall of the lens barrel 21 by means of the fastening bolts 37 , thereby achieving the installation and fixation of the support plate 35 on the lens barrel 21 .

[0042] In this embodiment, the transmission mechanism can be composed of a rotating shaft 41, a positioning seat 42, a driving wheel 44, a driven wheel 43, a motor 45 and other main parts. Figure 2 As shown, it is used to control the opening and closing of four shielding plates 31, 32, 33, and 34.

[0043] As a preferred embodiment, a set of traditional mechanisms can be configured for each shielding plate, that is, a set of traditional mechanisms can only control the opening and closing of one shielding plate. Four sets of transmission mechanisms are arranged on the four sides of the support plate 35, and correspond to the positions of the four shielding plates 31, 32, 33, and 34 one by one.

[0044] In each transmission mechanism, the rotating shaft 41 is preferably arranged parallel to the bearing surface of the support plate 35, such as Figure 2 The outer side of the shielding plate 31 / 32 / 33 / 34 is fixed on the rotating shaft 41, and the shielding plate 31 / 32 / 33 / 34 is driven to open or close by rotating the rotating shaft 41 in different directions.

[0045] In each transmission mechanism, two positioning seats 42 are preferably provided, which are installed on the bearing surface of the support plate 35 and are located at both ends of the rotating shaft 41. A bearing is installed in each positioning seat 42, and the two ends of the rotating shaft 41 are correspondingly installed in the bearings of the two positioning seats 42, so that a rotating connection relationship is formed between the rotating shaft 41 and the positioning seats 42.

[0046] In each transmission mechanism, a motor 45, a driving wheel 44 and a driven wheel 43 are preferably provided in a group. Among them, the motor 45 is preferably installed at the bottom of the support plate 35, and the driving shaft 46 of the motor 45 is extended through the support plate 35 to the top of the bearing surface of the support plate 35. The driving wheel 44 is installed on the driving shaft 46 of the motor 45, and the axis of the driving wheel 44 and the axis of the driven wheel 43 are configured to be perpendicular to each other, and the driving wheel 44 is meshed with the driven wheel 43, and the driven wheel 43 is connected to the shaft 41. When the motor 45 rotates, the driving wheel 44 rotates with the driving shaft 46 of the motor 45, drives the driven wheel 43 to rotate, and then drives the shaft 41 to rotate, and controls the opening and closing of the shielding plate 31 / 32 / 33 / 34.

[0047] In this embodiment, the control system is used to control the operating state of the motor 45, including start-stop control, steering control, rotation angle control, etc.

[0048] As a preferred embodiment, the control system is preferably composed of a collection card, an industrial computer and a drive circuit, etc., which are not shown in the figure. Among them, the collection card can be connected to the receiving optical path system 23 to collect the electrical signal output by the receiving optical path system 23, and convert it into a corresponding digital signal and send it to the industrial computer.

[0049] As the control core of the entire laser radar, the industrial computer, on the one hand, generates a control signal and sends it to the drive circuit to drive the motor 45 to operate, thereby realizing the opening and closing control of the shielding plates 31, 32, 33, and 34; on the other hand, it determines the adjustment direction and angle of the laser radar's transmitting optical axis according to the digital signal output by the acquisition card, and then generates a corresponding control signal, and controls the movement of the adjustable electric-controlled mirror frame 14 through the drive circuit to adjust the angle or position of the reflector 13, thereby realizing the adjustment of the transmitting optical axis; thirdly, after the laser radar's receiving and transmitting optical axis alignment operation is completed and put into normal use, the digital signal output by the acquisition card is stored, and based on the digital signal, the detection result is generated by the existing radar signal detection method, and stored and displayed.

[0050] Combine the following Figure 1-Figure 3 The laser radar with the structure shown in the figure specifically describes the calibration process of the transmitting optical axis and the receiving optical axis. Figure 4 As shown, the following process is included:

[0051] S401, start the laser emission system to emit a laser beam into the atmosphere.

[0052] S402, selecting a comparison height interval H1 for the first quadrant I and the second quadrant II;

[0053] In this embodiment, according to the four-quadrant division method of this embodiment, whether it is a coaxial laser radar or a side-axis laser radar, when selecting the comparison height interval H1 for the first quadrant I and the second quadrant II, it is only necessary to select a height with a good signal-to-noise ratio and no clouds. For example, 1km to 4km can be selected as the comparison height interval H1, that is, the starting position of the comparison height m = 1km, and the ending position of the comparison height n = 4km. Of course, other intervals can also be selected, as long as the requirement of nm ≥ 2km is met.

[0054] The signal comparison height range can be selected according to the actual weather conditions, preferably at a height with a high signal-to-noise ratio and no clouds.

[0055] S403, control the shielding plate 31 to rotate 90 degrees upward to open, receive the atmospheric echo signal through the receiving light window of the telescope 20 in the first quadrant I, and collect and compare the receiving signal of each distance point i in the height interval H1 to form the receiving data S1(i);

[0056] In this embodiment, the shielding plate 31 can be controlled to open first, and the other shielding plates 32-34 can be closed. At this time, the atmospheric echo signal is received by the receiving light window of the telescope 20 in the first quadrant I, transmitted to the receiving optical path system 23, and an electrical signal corresponding to the intensity of the received optical signal is generated. After being collected by the acquisition card, the received data is generated and sent to the industrial computer for recording.

[0057] As a preferred embodiment, the industrial computer presets a set time T (for example, T=1 minute), collects received data for each distance point i in the comparison height interval H1 multiple times within the set time T, and then accumulates, averages, and removes background processing on the received data collected within the set time T to generate the received data S1(i) of the distance point i. The distance difference between two adjacent distance points can be determined according to the distance resolution of the laser radar collection data.

[0058] The background removal process is an existing technology, and the removed signals include radar background noise, light signals in the atmosphere, etc. Among them, the radar background noise can be obtained in the following way:

[0059] The industrial computer drives the motor 45 through the driving circuit to close all four shading plates 31-34, and receives the optical signal collected by the telescope 20 through the receiving optical path system 23, and converts it into a corresponding electrical signal. After being collected and converted by the acquisition card, the background signal of the laser radar is formed, that is, the radar noise floor.

[0060] After the collection of the received data S1 (i) is completed, the shielding plate 31 is controlled to rotate downward by 90 degrees and close.

[0061] S404, control the shielding plate 32 to rotate 90 degrees upward to open, receive the atmospheric echo signal through the receiving light window of the telescope 20 in the second quadrant II, and collect and compare the receiving signal of each distance point i in the height interval H1 to form the receiving data S2(i);

[0062] In this embodiment, the shielding plate 32 can be controlled to rotate upward 90 degrees to open, and the other shielding plates 31, 33, and 34 can be closed. At this time, the atmospheric echo signal is received by the receiving light window of the telescope 20 in the second quadrant II, transmitted to the receiving optical path system 23, and an electrical signal corresponding to the intensity of the received optical signal is generated. After being collected by the acquisition card, the received data is generated and sent to the industrial computer for recording.

[0063] The industrial computer collects received data for each distance point i multiple times within the set time T in the comparison height interval H1, and then accumulates, averages and removes the background of the received data collected within the set time T to generate the received data S2(i) of the distance point i.

[0064] After the acquisition of the received data S2(i) is completed, control the shutter 32 to rotate downward by 90° to close.

[0065] S405. Calculate the root mean square difference σ between S1(i) and S2(i) 12 ;

[0066] Substitute the received data S1(i) and S2(i) into the following root mean square difference calculation formula to calculate the root mean square difference σ 12 :

[0067]

[0068] S406. If σ 12 is less than or equal to the set collimation threshold, there is no need to adjust the emission optical axis in the directions of the first quadrant Ⅰ and the second quadrant Ⅱ, and jump to process S409;

[0069] In this embodiment, the collimation threshold should be 0 under ideal conditions. In the actual process, it can be specifically determined according to the optical axis collimation accuracy required by the user.

[0070] S407. If σ 12 is greater than the set collimation threshold, calculate the average values of S1(i) and S2(i), denoted as S′1 and S'2 respectively;

[0071] In this embodiment, the received data S1(i) of all distance points i within the comparison height interval H1 can be accumulated and averaged to generate S′1. Similarly, the received data S2(i) of all distance points i within the comparison height interval H1 can be accumulated and averaged to generate S'2.

[0072] S408. Compare S′1 and S'2; if S′1 > S'2, adjust the adjustable electro-optic mirror frame 14 to tilt the emission optical axis in the direction of the second quadrant Ⅱ; if S′1 < S'2, adjust the adjustable electro-optic mirror frame 14 to tilt the emission optical axis in the direction of the first quadrant Ⅰ;

[0073] In this embodiment, the adjustable electro-optic mirror frame 14 can be adjusted to act by cooperating the industrial control computer with the drive circuit to tilt the emission optical axis of the lidar in the direction of the first quadrant Ⅰ or the second quadrant Ⅱ.

[0074] To improve the adjustment speed and accuracy, this embodiment sets the adjustment step number B1, adjusts the emission optical axis step by step according to the adjustment step number B1, and after each adjustment, repeat the execution of processes S403 to S408 until σ 12 is less than or equal to the set collimation threshold, and the adjustment process of the emission optical axis in the directions of the first quadrant Ⅰ and the second quadrant Ⅱ ends.

[0075] In this embodiment, the setting of the adjustment step number B1 is preferably in direct proportion to |S1′-S′2|, so as to shorten the calibration time of the light receiving and transmitting axis.

[0076] S409, selecting a comparison height interval H2 for the third quadrant III and the fourth quadrant IV;

[0077] In this embodiment, according to the four-quadrant division method of this embodiment, if it is a side-axis laser radar, since the side-axis laser radar has a blind area overlap in the comparison height, the receiving signals of the two quadrants III and IV in the y-axis direction will be different in the overlap area. Since the third quadrant III is closer to the emitted laser beam 16, its receiving signal in the overlap area will be higher than the receiving signal of the fourth quadrant IV in the overlap area. Therefore, when comparing the two quadrant signals in the y-axis direction, the overlap area should be avoided.

[0078] Assuming that the height of the Overlap area is RO, a distance higher than RO can be selected to form the comparison height interval H2. For example, RO+1km to RO+3km can be selected as the comparison height interval H2, that is, the starting position of the comparison height M = RO+1km, and the ending position of the comparison height N = RO+3km. Of course, other intervals can also be selected as long as they meet the requirements of N>M>RO and NM≥2km.

[0079] If it is a coaxial laser radar, when selecting the comparison height interval H2 for the third quadrant III and the fourth quadrant IV, it is only necessary to select the height with a better signal-to-noise ratio without considering the impact of the blind area overlap.

[0080] S410, control the shielding plate 33 to rotate 90 degrees upward to open, receive the atmospheric echo signal through the receiving light window of the telescope 20 in the third quadrant III, and collect and compare the receiving signal of each distance point i in the height interval H2 to form receiving data S3(i);

[0081] In this embodiment, the shielding plate 33 can be controlled to rotate 90 degrees upward to open, and the other shielding plates 31, 32, and 34 can be closed. At this time, the atmospheric echo signal is received by the receiving light window of the telescope 20 in the third quadrant III, transmitted to the receiving optical path system 23, and an electrical signal corresponding to the intensity of the received optical signal is generated. After being collected by the acquisition card, the received data is generated and sent to the industrial computer for recording.

[0082] The industrial computer collects received data for each distance point i multiple times within the set time T in the comparison height interval H2, and then accumulates, averages and removes the background of the received data collected within the set time T to generate the received data S3(i) of the distance point i.

[0083] After the collection of the received data S3 (i) is completed, the shielding plate 33 is controlled to rotate downward by 90 degrees and close.

[0084] S411, control the shielding plate 34 to rotate 90 degrees upward to open, receive the atmospheric echo signal through the receiving light window of the telescope 20 in the fourth quadrant IV, and collect and compare the receiving signal of each distance point i in the height interval H2 to form the receiving data S4(i);

[0085] In this embodiment, the shielding plate 34 can be controlled to rotate upward 90 degrees to open, and the other shielding plates 31, 32, and 33 can be closed. At this time, the atmospheric echo signal is received by the receiving light window of the telescope 20 in the fourth quadrant IV, transmitted to the receiving optical path system 23, and an electrical signal corresponding to the intensity of the received optical signal is generated. After being collected by the acquisition card, the received data is generated and sent to the industrial computer for recording.

[0086] The industrial computer collects received data for each distance point i multiple times within the set time T in the comparison height interval H2, and then accumulates, averages and removes the background of the received data collected within the set time T to generate the received data S4(i) of the distance point i.

[0087] After the collection of the received data S4(i) is completed, the shielding plate 34 is controlled to rotate downward by 90 degrees and close.

[0088] S412, calculate the root mean square difference σ between S3(i) and S4(i) 34 ;

[0089] Substitute the received data S3(i) and S4(i) into the following RMS error calculation formula to calculate the RMS error σ 34 :

[0090]

[0091] S413, if σ 34 If the value is less than or equal to the set collimation threshold, there is no need to adjust the emission optical axis in the direction of the third quadrant III and the fourth quadrant IV, and the process jumps to process S416;

[0092] In this embodiment, the collimation threshold should ideally be 0. In practice, it can be specifically determined according to the optical axis collimation accuracy required by the user. The collimation threshold here can be set to be the same as the collimation threshold in process S406, or it can be different.

[0093] S414, if σ 34 If it is greater than the set collimation threshold, the average values ​​of S3(i) and S4(i) are calculated and recorded as S′3 and S′4 respectively;

[0094] In this embodiment, the received data S3(i) of all distance points i within the comparison height range H2 can be accumulated and then averaged to generate S′3. Similarly, the received data S4(i) of all distance points i within the comparison height range H2 can be accumulated and then averaged to generate S'4.

[0095] S415. Compare S′3 and S'4. If S′3 > S'4, adjust the adjustable electro-optical mirror mount 14 to tilt the emission optical axis in the direction of the fourth quadrant Ⅳ; if S′3 < S'4, adjust the adjustable electro-optical mirror mount 14 to tilt the emission optical axis in the direction of the third quadrant Ⅲ.

[0096] In this embodiment, the action of the adjustable electro-optical mirror mount 14 can be adjusted through an industrial control computer cooperating with a drive circuit to tilt the emission optical axis of the lidar in the direction of the third quadrant Ⅲ or the fourth quadrant Ⅳ.

[0097] To improve the adjustment speed and accuracy, this embodiment sets the adjustment step number B2, gradually adjusts the emission optical axis according to the adjustment step number B2, and after each adjustment, repeats the processes S410 to S415 until σ 34 is less than or equal to the set collimation threshold value, and the adjustment process of the emission optical axis in the directions of the third quadrant Ⅲ and the fourth quadrant Ⅳ ends.

[0098] In this embodiment, the setting of the adjustment step number B2 is preferably in a proportional relationship with |S′3 - S'4| to shorten the calibration time of the emission and reception optical axes.

[0099] S416. The calibration process of the emission optical axis and the reception optical axis of the lidar ends.

[0100] During the entire calibration process of the emission and reception optical axes, the calibration orders of the two directions can be interchanged.

[0101] The lidar of this embodiment has a simple structure, is convenient to use, has a high degree of automation, good optical axis calibration accuracy and high calibration efficiency, and can play an important role in the commercial application of lidars.

[0102] Certainly, the above description is only a preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and retouches can be made, and these improvements and retouches should also be regarded as the protection scope of the present invention.

Claims

1. A laser radar, comprising: A laser for emitting a laser beam; A reflector, which is used to direct the laser beam into the atmosphere; An adjustable electrically controlled mirror frame, on which the reflector is mounted, for adjusting the angle or position of the reflector to change the emission direction of the laser beam into the atmosphere, wherein the emission direction is the direction of the laser radar emission optical axis; The telescope comprises a lens barrel, in which a receiving light window is arranged for receiving an echo signal after the laser beam is emitted into the atmosphere; A receiving optical path system, which converts the echo signal received by the telescope into an electrical signal; It is characterized in that it also includes a four-quadrant shading mechanism, which includes: A four-quadrant shading plate, which is installed on the lens barrel of the telescope and is located above the receiving light window, and includes four shading plates, which are respectively used to block four partitions of the receiving light window, and the four partitions are divided by two mutually perpendicular diameters of the receiving light window to form four quadrants; A rotating mechanism connected to the four-quadrant shading plates to control the rotation of the four shading plates respectively and to open and close them independently; A control system, which controls the rotating mechanism to drive the four shading plates to be opened only in different time periods when calibrating the transmitting optical axis and the receiving optical axis, receives electrical signals from the four quadrants of the telescope through the receiving optical path system, controls the adjustable electrically controlled mirror frame to adjust the reflector according to the electrical signal, and further adjusts the emission direction of the laser beam to align the receiving and transmitting optical axis of the laser radar; Among the four quadrants, the first quadrant is centrally symmetrical with the second quadrant, and the third quadrant is centrally symmetrical with the fourth quadrant; When the laser radar is calibrating the transmitting optical axis and the receiving optical axis, The control system takes the shielding plates corresponding to the first quadrant and the second quadrant as a group, and controls the two shielding plates to be opened in a time-sharing and unique manner through the rotating mechanism, so that the telescope receives echo signals through its first quadrant and the second quadrant respectively, and collects the receiving signals of the first quadrant and the second quadrant through the receiving optical path system; the control system controls the movement of the adjustable electrically controlled mirror frame according to the receiving signals of the first quadrant and the second quadrant, so as to adjust the transmission optical axis of the laser radar to tilt toward the quadrant with a smaller receiving signal, until the receiving signal of the first quadrant is equivalent to the receiving signal of the second quadrant; The control system takes the shielding plates corresponding to the third quadrant and the fourth quadrant as a group, and controls the two shielding plates to open in a time-sharing and unique manner through the rotating mechanism, so that the telescope receives echo signals through its third quadrant and fourth quadrant respectively, and collects the receiving signals of the third quadrant and the fourth quadrant through the receiving optical path system; the control system controls the movement of the adjustable electrically-controlled mirror frame according to the receiving signals of the third quadrant and the fourth quadrant, so as to adjust the transmitting optical axis of the laser radar to tilt toward the quadrant with a smaller receiving signal, until the receiving signal of the third quadrant is equivalent to the receiving signal of the fourth quadrant.

2. The laser radar according to claim 1, characterized in that: When the laser radar is a side-axis laser radar, the four quadrants satisfy the following relationship in a virtual rectangular coordinate system: The virtual rectangular coordinate system is established in the plane where the receiving light window of the telescope is located, wherein the origin of the virtual rectangular coordinate system is the center of the receiving light window, and the y-axis passes through the center of the laser beam emitted to the atmosphere by the laser radar when the receiving and receiving light axes are collimated; The first quadrant and the second quadrant are respectively axisymmetric regions about the x-axis of the virtual rectangular coordinate system; The third quadrant and the fourth quadrant are respectively axisymmetric regions about the y-axis of the virtual rectangular coordinate system.

3. The laser radar according to claim 1, characterized in that: When the emission optical axis and the receiving optical axis are calibrated and the laser radar enters normal operation, the control system controls the rotating mechanism to drive all four shading plates to open, and uses the entire receiving optical window of the telescope to receive the echo signal; When the laser radar acquires the background signal, it controls the rotating mechanism to drive all four shading plates to close; the receiving optical path system collects the optical signal received by the telescope and generates a corresponding electrical signal as the background signal.

4. The laser radar according to any one of claims 1 to 3, characterized in that: The four-quadrant shading mechanism also includes: A support plate is mounted on the lens barrel of the telescope, and a bearing surface is formed above the lens barrel. The rotating mechanism is mounted on the bearing surface of the support plate.

5. The laser radar according to claim 4, characterized in that: The rotating mechanism includes four groups, which are respectively connected to the four shading plates, and each group of the rotating mechanism includes: A rotating shaft connected to one of the shielding plates; A positioning seat, which is installed on the bearing surface of the support plate, and a bearing is installed on the positioning seat, and the rotating shaft is installed in the bearing; A motor, which is mounted on the support plate and whose operating state is controlled by the control system; A driving wheel, which is connected to the motor shaft and driven to rotate by the motor; The driven wheel is meshed with the driving wheel and connected to the rotating shaft. When the motor drives the driving wheel to rotate, the driving wheel drives the driven wheel to rotate, thereby driving the shielding plate to open and close.

6. The laser radar according to claim 5, characterized in that: The motor is installed below the bearing surface of the support plate, and the driving shaft of the motor passes through the bearing surface and extends to the top of the bearing surface and is connected to the driving wheel shaft, and the axis of the driving wheel is perpendicular to the axis of the driven wheel.

7. The laser radar according to claim 5, characterized in that: The four groups of rotating mechanisms are disposed on four sides of the bearing surface of the support plate; in each group of rotating mechanisms, the rotating shaft is parallel to the bearing surface of the support plate; and the positioning seats each include two, which are disposed at both ends of the rotating shaft.

8. The laser radar according to any one of claims 1 to 3, characterized in that: Also includes: A beam expander, used for compressing the divergence angle of the laser beam emitted by the laser and then emitting it to the reflector; The launch system carrier is installed on the barrel of the telescope and is located on one side of the telescope; the laser, beam expander, reflector and adjustable electrically controlled mirror frame are all installed on the launch system carrier; the laser radar is configured as a coaxial laser radar or a side-axis laser radar by adjusting the adjustable electrically controlled mirror frame.

9. The laser radar according to any one of claims 1 to 3, characterized in that: The control system comprises: An acquisition card, which acquires the electrical signal output by the receiving optical path system and converts it into a digital signal; An industrial computer receives the digital signal output by the acquisition card and generates control signals for controlling the movement of the rotating mechanism and the adjustable electrically controlled mirror frame; The driving circuit receives the control signal output by the industrial computer to drive the rotating mechanism or the adjustable electric-controlled mirror frame to move.

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