CN111708031A

CN111708031A - Laser radar

Info

Publication number: CN111708031A
Application number: CN202010637496.9A
Authority: CN
Inventors: 陈超; 王章军; 李辉; 潘新; 段依然; 庄全风; 李先欣; 王秀芬; 张锋; 赵阳
Original assignee: Oceanographic Instrumentation Research Institute Shandong Academy of Sciences
Current assignee: Oceanographic Instrumentation Research Institute Shandong Academy of Sciences; Institute of Oceanographic Instrumentation Shandong Academy of Sciences
Priority date: 2020-07-03
Filing date: 2020-07-03
Publication date: 2020-09-25

Abstract

The invention discloses a laser radar, which comprises a laser, a telescope and a four-quadrant shading mechanism, wherein the laser is arranged on the telescope; the four-quadrant shading mechanism comprises a four-quadrant shading plate, a rotating mechanism and a control system; the four-quadrant shading plate is arranged on a lens barrel of the telescope, is positioned above a receiving light window of the telescope, and comprises four shading plates which are respectively used for correspondingly shading four subareas of the receiving light window, and the four subareas are formed by dividing two mutually vertical diameters of the receiving light window to form four quadrants; the rotating mechanism is connected with the four-quadrant light shading plates and respectively controls the four light shading plates to rotate and independently open and close; the control system is used for controlling the running state of the rotating mechanism so as to realize the collimation of the receiving and transmitting optical axis. The laser radar can finish the calibration task of the transmitting optical axis and the receiving optical axis by detecting the uniformity of the received signals of the four quadrants of the telescope, and can realize the automatic collimation of the receiving and transmitting optical axes of the laser radar under the unattended condition.

Description

Laser radar

Technical Field

The invention belongs to the technical field of detection equipment, and particularly relates to a laser radar.

Background

The laser radar is an active remote sensing monitoring device and has the advantages of high space-time resolution, high measurement accuracy and the like. In a laser radar system, the collimation of a receiving and transmitting optical axis is the key for ensuring the receiving efficiency of a laser radar signal. In actual operation of the laser radar, a transmission optical axis of the laser and a reception optical axis of the telescope are deviated due to temperature change, environmental vibration, laser jitter, and the like, which causes a decrease in received signal efficiency and signal distortion, and thus, it is necessary to periodically calibrate a transmission/reception optical axis of the laser radar. The so-called collimation of the transmitting and receiving optical axes means that the transmitting optical axis is parallel to the receiving optical axis for paraxial laser radars; for a coaxial lidar, the transmit and receive optical axes are coaxial.

The laser radar transmitting and receiving optical axis calibration method mainly comprises two methods, namely manual calibration and automatic calibration. The manual calibration is the most common collimation method, but the manual calibration requires that an operator has certain professional background and light path adjustment experience, the adjustment process is complicated and time-consuming, and the collimation precision adjusted by visual inspection data is difficult to ensure.

The automatic calibration method is mainly to adjust the direction of the emitted light beam by using a two-dimensional electronic control mirror bracket at present, and the common methods mainly include two methods:

one is that when the emitting optical axis and the receiving optical axis are aligned, before the laser beam is emitted to the atmosphere, a beam splitter with high transmission-reflection ratio (transmission: reflection) is firstly used for reflecting a small part of light as reference light; the reference light is then incident on a fixed photodetector, which marks this position as the position where the optical axis is collimated. When the emission optical axis deviates, the position of the reference light on the photoelectric detector also deviates, the angle of the reflector can be adjusted through the electric control reflector frame at the moment, the direction of the emission light is further adjusted, the position of the reference light on the photoelectric detector is just adjusted to the alignment position of the mark, and therefore the calibration operation is completed. However, this method has a problem that misjudgment of the optical axis misalignment is caused by the deviation of the spectroscope.

And the other method is that the two-dimensional electric control reflector frame is used for adjusting the emitted laser to scan along two mutually vertical diameter directions of the telescope respectively, a certain height is selected as a reference height, the change of a reference height signal in the scanning process is observed, and the position with the maximum received signal of the reference height is taken as the optimal position in two directions to determine the collimation 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.

Disclosure of Invention

According to the laser radar with the improved structure, the four-quadrant shading mechanism is designed on the telescope of the laser radar, so that the telescope can be controlled to independently receive the atmospheric echo signals on the four quadrants respectively, the direction of the transmitting optical axis is adjusted by comparing the signals of the centrosymmetric quadrants, and the automatic calibration of the transmitting optical axis is further realized.

In order to solve the technical problems, the invention adopts the following technical scheme:

a laser radar comprises a laser used for emitting a laser beam, a reflector used for emitting the laser beam into the atmosphere, an adjustable electric control mirror bracket used for installing the reflector on the reflector, a telescope, a receiving light path system and a four-quadrant shading mechanism; the adjustable electric control mirror frame is used for adjusting the angle or the position of the reflector so as to change the emergent direction of the laser beam to the atmosphere, and the emergent direction is the direction of the laser radar emission optical axis; the telescope comprises a lens barrel, wherein a receiving optical window is arranged in the lens barrel and used for receiving an echo signal emitted by a laser beam to the atmosphere; the receiving optical path system converts the echo signal received by the telescope into an electric signal; the four-quadrant shading mechanism comprises a four-quadrant shading plate, a rotating mechanism and a control system; the four-quadrant shading plate is arranged on a lens barrel of the telescope, is positioned above the light receiving window, and comprises four shading plates which are respectively used for correspondingly shading four subareas of the light receiving window, and the four subareas are formed by dividing two mutually-perpendicular diameters of the light receiving window to form four quadrants; the rotating mechanism is connected with the four-quadrant light shading plates and respectively controls the four light shading plates to rotate and independently open and close; when the control system is used for calibrating the transmitting optical axis and the receiving optical axis, the rotating mechanism is controlled to drive the four light shielding plates to be uniquely opened in different time periods, electric signals of four quadrants of the telescope are received through the receiving optical path system, the adjustable electric control mirror frame is controlled according to the electric signals to adjust the reflecting mirror, and then the emitting direction of laser beams is adjusted, so that the transmitting and receiving optical axes of the laser radar are calibrated.

In some embodiments of the present application, among the four quadrants, it is preferable to define a first quadrant in a centrosymmetric relationship with a second quadrant, and a third quadrant in a centrosymmetric relationship with a fourth quadrant; when the laser radar calibrates a transmitting optical axis and a receiving optical axis, the control system takes the shielding plates corresponding to the first quadrant and the second quadrant as a group, controls the two shielding plates to be opened in a time-sharing and unique mode through the rotating mechanism, enables the telescope to receive echo signals independently through the first quadrant and the second quadrant of the telescope 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 adjustable electric control lens frame to act according to the receiving signals of the first quadrant and the second quadrant so as to adjust the inclination of the transmitting light axis of the laser radar to the quadrant direction with small receiving signals 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, controls the two shielding plates to be opened in a time-sharing and unique mode through the rotating mechanism, enables the telescope to receive echo signals independently through the third quadrant and the fourth quadrant of the telescope respectively, and collects the receiving signals of the third quadrant and the fourth quadrant through the receiving optical path system; and the control system controls the action of the adjustable electric control lens frame according to the receiving signals of the third quadrant and the fourth quadrant so as to adjust the inclination of the transmitting light axis of the laser radar to the quadrant direction with small receiving signals until the receiving signal of the third quadrant is equivalent to the receiving signal of the fourth quadrant. Thereby completing the calibration process of the transmitting and receiving optical axis.

In some embodiments of the present application, when the lidar is a paraxial lidar, the four quadrants are further defined to satisfy the following relationships in a virtual rectangular coordinate system: the virtual rectangular coordinate system is established in a plane where a 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 a laser beam emitted to the atmosphere by the laser radar under the condition that the receiving and transmitting optical axes are collimated; the first quadrant and the second quadrant respectively present axisymmetrical areas relative to the x axis of the virtual rectangular coordinate system; and the third quadrant and the fourth quadrant respectively present axisymmetrical areas relative to the y axis of the virtual rectangular coordinate system.

In some embodiments of the present application, when the calibration of the transmitting optical axis and the receiving optical axis is completed and the laser radar enters into normal operation, the control system controls the rotating mechanism to drive the four light shielding plates to be fully opened, and the whole receiving optical window of the telescope is utilized to receive the echo signal.

In some embodiments of the present application, the lidar further has a capability of acquiring a background signal of the lidar, that is, when the lidar acquires the background signal, the lidar controls the rotating mechanism to drive all the four light shielding plates to be closed; the receiving optical path system collects optical signals received by the telescope and generates corresponding electric signals as the background signals. The background signal may be used as an indicator to evaluate the performance of the lidar.

In some embodiments of the present application, the four-quadrant shading mechanism further includes a supporting plate installed on the lens barrel of the telescope, a bearing surface is formed above the lens barrel, and the rotating mechanism is installed on the bearing surface of the supporting plate. Through the design the layer board can make things convenient for slewing mechanism lays and wholly dismantles in the installation on the telescope.

In some embodiments of the present application, the rotating mechanism is preferably provided with four groups, and the four groups of rotating mechanisms are respectively and correspondingly connected with the four light shielding plates, and each group of rotating mechanism comprises a rotating shaft, a positioning seat, a motor, a driving wheel and a driven wheel; wherein, the rotating shaft is connected with one of the shielding plates; the positioning seat is arranged on the bearing surface of the supporting plate, a bearing is arranged on the positioning seat, and the rotating shaft is arranged in the bearing; the motor is arranged on the supporting plate, and the running state of the motor is controlled by the control system; the driving wheel is in shaft connection with the motor and is driven by the motor to rotate; the driven wheel is meshed with the driving wheel and is in shaft connection with the rotating shaft, and when the motor drives the driving wheel to rotate, the driving wheel drives the driven wheel to rotate so as to drive the shielding plate to open and close.

In some embodiments of the present application, the motor is preferably installed below the bearing surface of the supporting plate, the driving shaft of the motor passes through the bearing surface, extends to above the bearing surface, and is coupled to the driving wheel, and 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 light receiving window of the telescope, thereby realizing large-area connection between the rotating shaft and the light shielding plate, which is helpful to improve the stability of the opening and closing process of the light shielding plate.

In some embodiments of the present application, four sets of the rotating mechanisms are respectively disposed on four sides of the carrying surface of the supporting plate; in each group of rotating mechanisms, the rotating shaft is parallel to the bearing surface of the supporting plate; the positioning seats are respectively arranged at two ends of the rotating shaft, and the stability of the opening and closing processes of the light screen is further guaranteed by improving the supporting force of the positioning seats on the rotating shaft and the light screen.

In some embodiments of the present application, the lidar further comprises a beam expander and a transmit system carrier; the beam expander is used for compressing the divergence angle of the laser beam emitted by the laser and then emitting the laser beam to the reflector; the transmitting system support plate is arranged on a lens barrel of the telescope and is positioned at one side of the telescope; the laser, the beam expanding lens, the reflecting mirror and the adjustable electric control mirror bracket can be arranged on the transmitting system support plate, so that the overall design of the laser radar is convenient to realize, and the overall movement and the carrying of the laser radar are further convenient. The lidar may be configured as a coaxial lidar or a paraxial lidar by adjusting the adjustable electrically controlled mirror mount.

In some embodiments of the present application, the control system preferably includes an acquisition card, an industrial personal computer, and a driving circuit; the acquisition card is used for acquiring the electric signal output by the receiving optical path system and converting the electric signal into a digital signal; the industrial personal computer receives the digital signals output by the acquisition card and respectively generates control signals for controlling the actions of the rotating mechanism and the adjustable electric control spectacle frame; and the driving circuit receives a control signal output by the industrial personal computer so as to drive the rotating mechanism or the adjustable electric control mirror bracket to act. Therefore, the laser radar has the function of automatically calibrating the receiving optical axis and the transmitting optical axis.

Compared with the prior art, the invention has the advantages and positive effects that: according to the laser radar, the telescope is provided with the four-quadrant shading mechanism, so that the receiving optical window of the telescope can respectively receive the atmosphere echo signals in four quadrant areas of the telescope. When the four quadrant light-shielding plates of the telescope are all opened, the laser radar can normally work; when the light shielding plates of the four quadrants are completely closed, the laser radar can collect background signals; when the laser radar carries out transmitting optical axis and receiving optical axis calibration, the atmosphere echo signals of four quadrants can be utilized to provide adjusting basis for the direction of the transmitting optical axis of the laser radar, and when the atmosphere echo signals of two groups of quadrants with symmetrical centers are basically the same, the collimation of the transmitting and receiving optical axes of the laser radar can be realized. The laser radar realizes the calibration of the transmitting optical axis and the receiving optical axis of the laser radar by utilizing the uniformity detection of the signals received by the four quadrants of the telescope, has simple method and convenient use, is beneficial to improving the working efficiency and the operation convenience of the laser radar, can realize the automatic collimation of the transmitting and receiving optical axes under the unattended condition, can realize the acquisition of background signals of the laser radar, and provides a basis for the performance evaluation of the laser radar.

Other features and advantages of the present invention will become more apparent from the detailed description of the embodiments of the present invention when taken in conjunction with the accompanying drawings.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic overall structure diagram of an embodiment of a laser radar according to the present invention;

FIG. 2 is a schematic structural diagram of one embodiment of the four-quadrant shutter mechanism of FIG. 1;

FIG. 3 is a diagram illustrating an exemplary correspondence between quadrant divisions of a telescope of the paraxial lidar and the location of the laser beam exiting to the atmosphere;

fig. 4 is a flowchart of an embodiment of a lidar transceiver optical axis calibration process.

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings.

It should be noted that in the description of the present invention, the terms "upper", "lower", "inside", "outside", and the like, which indicate directions or positional relationships, are based on the directions or positional relationships shown in the drawings, which are for convenience of description only, 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 thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

As shown in fig. 1, the laser radar of the present embodiment mainly includes two parts, a laser emitting 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 electronic control frame 14, and the like. The optical receiving system is mainly composed of a telescope 20 and a subsequent receiving optical path system 23.

In order to facilitate the integration and assembly of the laser emitting system 10 and the optical receiving system together, so that the laser radar can be easily moved or carried as a whole, the present embodiment preferably mounts the laser emitting system 10 on a emitting system carrier plate 15, as shown in fig. 1. Wherein the laser 11 is preferably mounted in a downwardly biased position on the launch system carrier plate 15 for launching the laser beam. The beam expander 12 is located above the laser 11, and is configured to compress a divergence angle of the laser beam emitted from the laser 11 to form a laser beam having a certain diameter, and is incident on the reflector 13. One or more reflectors 13 may be mounted on the adjustable electronic control frame 14, and are configured to reflect the laser beam incident thereon and emit the reflected laser beam to the atmosphere. The angle or position of the mirror 13 can be adjusted by the adjustable electronic control frame 14, and then the emitting direction of the laser beam to the atmosphere is changed.

The transmitting system carrier plate 15 is mounted on the telescope 20, preferably on the barrel 21 of the telescope 20, and is located at one side of the telescope 20, as shown in fig. 1. The adjustable electric control mirror bracket 14 is controlled to properly adjust the angle or position of the reflector 13, so that the emitting direction of the laser beam (i.e. the emitting optical axis direction of the laser radar) is parallel to the receiving optical axis of the telescope 20, and then the paraxial laser radar can be formed; if the emitting direction of the laser beam is adjusted to be coaxial with the receiving optical axis of the telescope 20, a coaxial lidar can be formed. For the lidar structure shown in fig. 1, if a coaxial lidar is formed, a set of reflector may be added on the basis of the lidar structure shown in fig. 1.

A lens barrel 21 of the telescope 20 is provided with a light receiving window 22, as shown in fig. 1 and 3. In a normal case, the receiving optical window 22 is circular, receives an echo signal after the laser beam 16 is incident into the atmosphere, and converges the echo signal to the subsequent receiving optical path system 23 to convert the optical signal into an electrical signal. The magnitude of the electrical signal can reflect the intensity of the received optical signal, and the target with the preset height can be detected by using the existing radar signal detection method according to the electrical signal output by the receiving optical path system 23.

In a laser radar system, the collimation of the transmitting and receiving optical axes is the key for ensuring the receiving efficiency of the laser radar signal, and the transmitting optical axis and the receiving optical axis of the laser radar need to be calibrated. Tests prove that the uniformity detection of four quadrant received signals of a telescope of the laser radar is a mode for realizing the calibration of a receiving and transmitting optical axis of the laser radar. In order to apply the calibration method to the laser radar of this embodiment, in this embodiment, a structure of the existing laser radar is first improved, and a four-quadrant shading mechanism 30 is additionally provided to divide the receiving optical window 22 of the telescope 20 into four regions to form four quadrants, so as to independently receive the atmospheric echo signal, and further meet the requirement of uniformity detection of the four quadrant receiving signals.

Referring to fig. 1 and 2, the four-quadrant light-shielding mechanism 30 of the present embodiment mainly includes a four-quadrant light-shielding plate, a rotating mechanism, and a control system.

In the present embodiment, the four-quadrant light-blocking plate is preferably mounted on the lens barrel 21 of the telescope 20 and located above the light-receiving window 22, and preferably includes four light-blocking

plates

31, 32, 33, 34, as shown in fig. 2. The four

light baffles

31, 32, 33, 34 can be designed in the same shape, for example, in a triangle-like shape, and the light receiving window 22 of the telescope 20 is covered completely after being spliced.

Four shielding areas formed on the reception light window 22 of the telescope 20 by four light-shielding

plates

31, 32, 33, 34 are arranged to coincide with four divisions divided by two mutually perpendicular diameters of the reception light window 22 as shown in fig. 3, and then the reception light window 22 is divided into four quadrants. Wherein, 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 a shielding plate 33; the fourth quadrant iv is shielded by the shield plate 34. The first quadrant I and the second quadrant II are arranged to be in a centrosymmetric relation, and the third quadrant III and the fourth quadrant IV are arranged to be in a centrosymmetric relation.

For the coaxial lidar, the positional relationship of the four quadrants is only required to satisfy the above configuration requirements.

For paraxial lidar, the positional relationship of the four quadrants needs to be further limited in addition to meeting the configuration requirements, specifically: a virtual rectangular coordinate system may be established on the plane where the receiving optical window 22 of the telescope is located, as shown in fig. 3, the origin of the virtual rectangular coordinate system is the center O of the receiving optical window 22, and the y-axis passes through the center O' of the laser beam 16 emitted to the atmosphere by the laser radar under the condition of collimation of the transmitting and receiving optical axes. According to the principle of determining a straight line from two points, the direction of the y-axis and thus the direction of the x-axis can be determined by using the center O of the receiving light window 22 and the center O' of the laser beam 16. When the area division is performed, the first quadrant i and the second quadrant ii are configured to be axisymmetric areas respectively about the x-axis of the virtual rectangular coordinate system (for the circular light receiving window 22, that is, the sectors corresponding to the first quadrant i and the second quadrant ii are axisymmetric patterns respectively about the x-axis); the third quadrant iii and the fourth quadrant iv are configured to be axisymmetric regions with respect to the y-axis of the virtual rectangular coordinate system, respectively (for the circular light receiving window 22, that is, the sectors corresponding to the third quadrant iii and the fourth quadrant iv are axisymmetric patterns with respect to the y-axis, respectively).

In order to facilitate the installation and fixation of the four-quadrant light-shielding plate on the barrel 21 of the telescope 20, the present embodiment preferably installs the four-quadrant light-shielding plate on a supporting plate 35 first, as shown in fig. 2. The support plate 35 is preferably designed in the form of a ring, the central opening area of which faces the light receiving window 22 of the telescope 20. The four

light shading plates

31, 32, 33 and 34 are sequentially arranged on the bearing surface formed by the supporting plate 35 in the circumferential direction, and the middle opening area of the supporting plate 35 is shielded after being spliced.

Preferably, a lower flange 36 is formed on the supporting plate 35, and two lower flanges 36 may be formed on two opposite sides of the supporting plate 35; four may be provided and formed around the pallet 35.

When the telescopic bracket is installed, the supporting plate 35 is placed on the upper edge of the lens barrel 21 of the telescope 20, and the downward flange 36 of the supporting plate 35 is at least partially attached to the side wall of the lens barrel 21, as shown in fig. 1. The downward flange 36 is screwed with the side wall of the lens barrel 21 by the fastening bolt 37, and then the mounting and fixing of the supporting plate 35 on the lens barrel 21 are realized.

In this embodiment, the transmission mechanism may be composed of a main portion such as a rotating shaft 41, a positioning seat 42, a driving wheel 44, a driven wheel 43, and a motor 45, as shown in fig. 2, and is used for controlling the opening and closing of the four

shielding plates

31, 32, 33, and 34.

As a preferred embodiment, a set of conventional mechanisms can be separately configured for each shielding plate, that is, a set of conventional mechanisms only controls the opening and closing of one shielding plate. Four sets of transmission mechanisms are respectively arranged on four sides of the supporting plate 35 and correspond to the positions of the four

shielding plates

31, 32, 33 and 34 one by one.

In each set of drives, the axis of rotation 41 is preferably arranged parallel to the bearing surface of the pallet 35, as shown in fig. 2. The outer side edge of the shielding plate 31/32/33/34 is fixed on the rotating shaft 41, and the rotation of the rotating shaft 41 in different directions drives the shielding plate 31/32/33/34 to open or close.

In each set of transmission mechanism, two positioning seats 42 are preferably provided, and are installed on the bearing surface of the supporting plate 35 and located at two ends of the rotating shaft 41. A bearing is respectively installed in each positioning seat 42, and 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.

In each set of transmission, the motor 45, the driving pulley 44 and the driven pulley 43 are preferably arranged in one set. Wherein the motor 45 is preferably mounted at the bottom of the pallet 35, and the driving shaft 46 of the motor 45 extends through the pallet 35 to above the carrying surface of the pallet 35. A driving pulley 44 is mounted on a driving shaft 46 of the motor 45, and the driving pulley 44 and the driven pulley 43 are disposed such that the axis of the driving pulley 44 and the axis of the driven pulley 43 are perpendicular to each other, and the driven pulley 43 and the rotating shaft 41 are coupled to each other by meshing the driving pulley 44 with the driven pulley 43. When the motor 45 rotates, the driving wheel 44 rotates along with the driving shaft 46 of the motor 45 to drive the driven wheel 43 to rotate, so as to drive the rotating shaft 41 to rotate, and the shutter 31/32/33/34 is controlled to open and close.

In this embodiment, the control system is configured to control the operation state of the motor 45, including start-stop control, steering control, rotation angle control, and the like.

As a preferred embodiment, the control system preferably comprises a collection card, an industrial personal computer, a driving circuit, and the like, which are not shown in the figure. The acquisition card can be connected to the receiving optical path system 23, and is configured to acquire the electrical signal output by the receiving optical path system 23, convert the electrical signal into a corresponding digital signal, and send the digital signal to the industrial personal computer.

The industrial personal computer is used as a control core of the whole laser radar, on one hand, a control signal is generated and sent to the driving circuit to drive the motor 45 to operate, and then the opening and closing control of the shielding

plates

31, 32, 33 and 34 is realized; on the other hand, the adjustment direction and angle of the transmitting optical axis of the laser radar are determined according to the digital signals output by the acquisition card, so that corresponding control signals are generated, the drive circuit controls the action of the adjustable electric control mirror bracket 14, the angle or position of the reflector 13 is adjusted, and the adjustment of the transmitting optical axis is realized; and in the third aspect, after the collimation operation of the receiving and transmitting optical axes of the laser radar is finished and the laser radar is put into normal use, the digital signals output by the acquisition card are stored, and the detection result is generated by utilizing the existing radar signal detection method according to the digital signals and is stored and displayed.

The following describes a calibration process of the transmitting optical axis and the receiving optical axis in detail with reference to the laser radar having the structure shown in fig. 1 to 3. As shown in fig. 4, the following process is included:

s401, starting a laser emitting system to emit laser beams to the atmosphere.

S402, selecting a contrast height interval H1 aiming at a first quadrant I and a second quadrant II;

in this embodiment, according to the four-quadrant division method of this embodiment, no matter coaxial laser radar or paraxial laser radar, when selecting the contrast height interval H1 for the first quadrant i and the second quadrant ii, only the height with a good signal-to-noise ratio and without clouds needs to be selected. For example, 1km to 4km may be selected as the comparison height section H1, that is, the starting position m of the comparison height is 1km and the ending position n of the comparison height is 4 km. Of course, other intervals may be selected, only satisfying: n-m is more than or equal to 2 km.

The comparison height interval of the signals can be selected according to the actual weather condition, and the signal-to-noise ratio is high and the height is suitable for the height without clouds.

S403, controlling the shielding plate 31 to rotate upwards by 90 degrees and open, receiving the atmosphere echo signal through the receiving optical window of the telescope 20 in the first quadrant I, collecting the receiving signal of each distance point i in the contrast height interval H1, and forming received data S₁(i)；

In the present embodiment, the shutter 31 may be controlled to be opened first, and the remaining shutters 32 to 34 may be closed. At this time, the atmospheric echo signal is received by the receiving optical window of the telescope 20 in the first quadrant i, transmitted to the receiving optical path system 23, generated as an electrical signal corresponding to the intensity of the received optical signal, collected by the acquisition card, and then generated as receiving data, and sent to the industrial personal computer for recording.

As a preferred embodiment, the industrial personal computer presets a set time T (for example, T is 1 minute), collects the received data for each distance point i in the contrast height interval H1 for multiple times within the set time T, and then generates the received data S of the distance point i after accumulating, averaging and background removing the received data collected within the set time T₁(i) In that respect And the distance difference between two adjacent distance points can be determined according to the distance resolution of the data acquired by the laser radar.

The background removing process is the prior art, and the removed signals comprise radar background noise, light signals in the atmosphere and the like. The radar noise floor can be obtained by adopting the following modes:

the industrial personal computer drives the motor 45 to operate through the driving circuit, the four light shielding plates 31-34 are all closed, the light signals collected by the telescope 20 are received through the receiving light path system 23 and are converted into corresponding electric signals, and the corresponding electric signals are collected and converted by the collecting card to form background signals of the laser radar, namely radar bottom noise.

Receiving data S₁(i) After the collection is finished, the shielding plate 31 is controlled to rotate downwards by 90 degrees and is closed.

S404, controlling the shielding plate 32 to rotate upwards by 90 degrees and open, receiving the atmosphere echo signal through the receiving optical window of the telescope 20 in the second quadrant II, collecting the receiving signal of each distance point i in the contrast height interval H1, and forming received data S₂(i)；

In the present embodiment, the shutter 32 can be controlled to rotate upward by 90 ° to open, and the remaining

shutters

31, 33, 34 are closed. At this time, the atmospheric echo signal is received by the receiving optical window of the telescope 20 in the second quadrant ii, transmitted to the receiving optical path system 23, generated as an electrical signal corresponding to the intensity of the received optical signal, collected by the acquisition card, and then generated as receiving data, and sent to the industrial personal computer for recording.

The industrial personal computer collects the received data for each distance point i within a set time T for multiple times within a contrast height interval H1, then accumulates, averages and removes the background of the received data collected within the set time T to generate the received data S of the distance point i₂(i)。

Receiving data S₂(i) After the collection is finished, the shielding plate 32 is controlled to rotate downwards by 90 degrees and is closed.

S405, calculating S₁(i) And S₂(i) Root mean square difference σ of₁₂；

Will receive data S₁(i) And S₂(i) Substituting the following root mean square deviation calculation formula to calculate the root mean square deviation sigma₁₂：

S406, if σ₁₂If the collimation threshold value is less than or equal to the set collimation threshold value, the emission optical axis does not need to be adjusted in the direction of the first quadrant I and the second quadrant II, and the process S409 is skipped;

in this embodiment, the collimation threshold should ideally be 0. In the practical process, the alignment precision of the optical axis can be specifically determined according to the requirement of a user.

S407, if σ₁₂If the value is larger than the set collimation threshold value, S is calculated₁(i) And S₂(i) Are each designated as S'₁、S'₂；

In this embodiment, the received data S of all the distance points i in the contrast height interval H1 can be compared₁(i) Adding and averaging to generate S'₁. Similarly, the received data S of all distance points i in the height interval H1 will be compared₂(i) Adding and averaging to generate S'₂。

S408, comparison of S'₁And S'₂(ii) a If S'₁>S'₂Adjusting the adjustable electric control lens frame 14 to enable the emitting light axis to incline towards the direction of the second quadrant II; if S'₁<S'₂Then the electronic control frame 14 is adjusted to enable the adjusting emitting light axis to incline towards the direction of the first quadrant I;

in this embodiment, the action of the adjustable electric control lens frame 14 can be adjusted by the industrial personal computer in cooperation with a driving circuit, so that the emitted light axis of the laser radar is inclined towards the first quadrant i or the second quadrant ii.

In order to improve the adjustment speed and accuracy, the present embodiment sets the adjustment step number B1, adjusts the emission optical axis stepwise in accordance with the adjustment step number B1, and repeatedly performs the processes S403 to S408 until σ after each adjustment₁₂And when the collimation threshold is less than or equal to the set collimation threshold, the adjustment process of the emission optical axis in the direction of the first quadrant I and the second quadrant II is finished.

In the present embodiment, the setting of the adjustment step number B1 is preferably equal to | S₁'-S'₂And | is in a direct proportional relation to shorten the calibration time of the transmitting and receiving optical axis.

S409, selecting a contrast height interval H2 for the third quadrant III and the fourth quadrant IV;

in this embodiment, according to the four-quadrant division method of this embodiment, if the paraxial lidar is a paraxial lidar, since the paraxial lidar has a blind area Overlap in the contrast height, the received signals of the two quadrants iii and iv in the y-axis direction may be different in the Overlap area. Since the third quadrant iii is closer to the emitted laser beam 16, the received signal in the Overlap region is higher than the received signal in the Overlap region in the fourth quadrant iv, and therefore, when comparing the signals in the two quadrants in the y-axis direction, the Overlap region is avoided.

Assuming that the height of the Overlap region is RO, a distance above RO may be selected to form the contrast height interval H2. For example, RO +1km to RO +3km may be selected as the comparison altitude range H2, that is, the start position M of the comparison altitude is RO +1km, and the end position N of the comparison altitude is RO +3 km. Of course, other intervals may be selected, only satisfying: n is more than M and RO, and N-M is more than or equal to 2 km.

If the height interval H2 is selected for the third quadrant III and the fourth quadrant IV, only the height with better signal-to-noise ratio is selected, and the influence of a blind area Overlap is not considered.

S410, controlling the shielding plate 33 to rotate upwards by 90 degrees and open, receiving the atmosphere echo signal through the receiving light window of the telescope 20 in the third quadrant III, collecting the receiving signal of each distance point i in the contrast height interval H2, and forming received data S₃(i)；

In the present embodiment, the shutter 33 can be controlled to rotate upward by 90 ° to be opened, and the remaining

shutters

31, 32, 34 are closed. At this time, the atmospheric echo signal is received by the receiving optical window of the telescope 20 in the third quadrant iii, transmitted to the receiving optical path system 23, generated as an electrical signal corresponding to the intensity of the received optical signal, collected by the acquisition card, and then generated as receiving data, and sent to the industrial personal computer for recording.

The industrial personal computer collects the received data for each distance point i within a set time T for multiple times within a contrast height interval H2, then accumulates, averages and removes the background of the received data collected within the set time T to generate the received data S of the distance point i₃(i)。

Receiving data S₃(i) After the collection is finished, the shielding plate 33 is controlled to rotate downwards by 90 degrees and is closed.

S411, controlling the shielding plate 34 to rotate upwards by 90 degrees and open, and passing through the telescope20, receiving the atmospheric echo signal by the receiving optical window in the fourth quadrant iv, and collecting the received signal of each distance point i in the contrast height interval H2 to form received data S₄(i)；

In the present embodiment, the shutter 34 may be controlled to rotate upward by 90 ° to be opened, and the remaining

shutters

31, 32, 33 may be closed. At this time, the atmospheric echo signal is received by the receiving optical window of the telescope 20 in the fourth quadrant iv, transmitted to the receiving optical path system 23, generated as an electrical signal corresponding to the intensity of the received optical signal, collected by the acquisition card, and generated as receiving data, and sent to the industrial personal computer for recording.

The industrial personal computer collects the received data for each distance point i within a set time T for multiple times within a contrast height interval H2, then accumulates, averages and removes the background of the received data collected within the set time T to generate the received data S of the distance point i₄(i)。

Receiving data S₄(i) After the collection is finished, the shielding plate 34 is controlled to rotate downwards by 90 degrees and is closed.

S412, calculating S₃(i) And S₄(i) Root mean square difference σ of₃₄；

Will receive data S₃(i) And S₄(i) Substituting the following root mean square deviation calculation formula to calculate the root mean square deviation sigma₃₄：

S413, if σ₃₄If the collimation threshold value is less than or equal to the set collimation threshold value, the emission optical axis does not need to be adjusted in the direction of the third quadrant III and the fourth quadrant IV, and the process jumps to the step S416;

in this embodiment, the collimation threshold should ideally be 0. In the practical process, the alignment precision of the optical axis can be specifically determined according to the requirement of a user. The collimation threshold may be set to be the same as or different from the collimation threshold in the process S406.

S414, if σ₃₄If the value is larger than the set collimation threshold value, S is calculated₃(i) And S₄(i) Are each designated as S'₃、S'₄；

In this embodiment, the received data S of all the distance points i in the contrast height interval H2 can be compared₃(i) Adding and averaging to generate S'₃. Similarly, the received data S of all distance points i in the height interval H2 will be compared₄(i) Adding and averaging to generate S'₄。

S415, comparison of S'₃And S'₄If S'₃>S'₄Adjusting the adjustable electric control lens frame 14 to enable the emitting light axis to incline towards the direction of the fourth quadrant IV; if S'₃<S'₄Adjusting the adjustable electric control lens frame 14 to enable the emitting light axis to incline towards the third quadrant III;

in this embodiment, the motion of the adjustable electric control frame 14 can be adjusted by the industrial personal computer in cooperation with a driving circuit, so that the emitted light axis of the laser radar can be inclined towards the third quadrant iii or the fourth quadrant iv.

In order to improve the adjustment speed and accuracy, the present embodiment sets the adjustment step number B2, adjusts the emission optical axis stepwise in accordance with the adjustment step number B2, and repeats the processes S410 to S415 until σ after each adjustment₃₄And when the collimation threshold value is less than or equal to the set collimation threshold value, the adjustment process of the emission optical axis in the direction of the third quadrant III and the fourth quadrant IV is finished.

In this embodiment, the setting of the adjustment step number B2 is preferably equal to | S'₃-S'₄And | is in a direct proportional relation to shorten the calibration time of the transmitting and receiving optical axis.

And S416, finishing the calibration process of the transmitting optical axis and the receiving optical axis of the laser radar.

The calibration orders of the two directions can be interchanged in the whole calibration process of the transmitting and receiving optical axis.

The laser radar of this embodiment simple structure, convenient to use, degree of automation is high, and the optical axis calibration precision is good and the calibration is efficient, can play important impetus on laser radar's business ization is used.

Of course, the above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, it is possible to make various modifications and decorations without departing from the principle of the present invention, and these modifications and decorations should be regarded as the protection scope of the present invention.

Claims

1. A lidar comprising:

a laser for emitting a laser beam;

a mirror for emitting the laser beam into the atmosphere;

the adjustable electric control mirror frame is provided with the reflector and is used for adjusting the angle or the position of the reflector so as to change the emergent direction of the laser beam to the atmosphere, wherein the emergent direction is the direction of a laser radar emission optical axis;

the telescope comprises a lens cone, wherein a receiving optical window is arranged in the lens cone and is used for receiving an echo signal emitted by a laser beam to the atmosphere;

a receiving optical path system that converts an echo signal received by the telescope into an electric signal;

its characterized in that still includes four-quadrant shading mechanism, and it includes:

the four-quadrant shading plate is arranged on the lens cone of the telescope, is positioned above the light receiving window, and comprises four shading plates which are respectively used for correspondingly shading four subareas of the light receiving window, and the four subareas are formed by dividing two mutually vertical diameters of the light receiving window to form four quadrants;

the rotating mechanism is connected with the four-quadrant light shading plates, and respectively controls the four light shading plates to rotate and independently open and close;

and the control system controls the rotating mechanism to drive the four light shielding plates to be uniquely opened at different time periods when the transmitting optical axis and the receiving optical axis are calibrated, receives electric signals of four quadrants of the telescope through the receiving optical path system, controls the adjustable electric control mirror bracket to adjust the reflector according to the electric signals, and further adjusts the emitting direction of laser beams so as to collimate the transmitting and receiving optical axes of the laser radar.

2. Lidar according to claim 1,

in the four quadrants, a first quadrant and a second quadrant are in central symmetry, and a third quadrant and a fourth quadrant are in central symmetry;

when the laser radar is used for 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, controls the two shielding plates to be opened in a time-sharing and unique mode through the rotating mechanism, enables the telescope to receive echo signals independently through the first quadrant and the second quadrant of the telescope 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 adjustable electric control lens frame to act according to the receiving signals of the first quadrant and the second quadrant so as to adjust the inclination of the transmitting light axis of the laser radar to the quadrant direction with small receiving signals 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, controls the two shielding plates to be opened in a time-sharing and unique mode through the rotating mechanism, enables the telescope to receive echo signals independently through the third quadrant and the fourth quadrant of the telescope respectively, and collects the receiving signals of the third quadrant and the fourth quadrant through the receiving optical path system; and the control system controls the action of the adjustable electric control lens frame according to the receiving signals of the third quadrant and the fourth quadrant so as to adjust the inclination of the transmitting light axis of the laser radar to the quadrant direction with small receiving signals until the receiving signal of the third quadrant is equivalent to the receiving signal of the fourth quadrant.

3. The lidar of claim 2, wherein when the lidar is a paraxial lidar, the four quadrants satisfy the following relationships in a virtual rectangular coordinate system:

the virtual rectangular coordinate system is established in a plane where a 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 a laser beam emitted to the atmosphere by the laser radar under the condition that the receiving and transmitting optical axes are collimated;

the first quadrant and the second quadrant respectively present axisymmetrical areas relative to the x axis of the virtual rectangular coordinate system;

and the third quadrant and the fourth quadrant respectively present axisymmetrical areas relative to the y axis of the virtual rectangular coordinate system.

4. Lidar according to claim 1,

when the calibration of the transmitting optical axis and the receiving optical axis is finished and the laser radar enters normal work, the control system controls the rotating mechanism to drive the four light shielding plates to be completely opened, and the whole receiving optical window of the telescope is utilized to receive echo signals;

when the laser radar acquires a background signal, the rotating mechanism is controlled to drive the four light shielding plates to be completely closed; the receiving optical path system collects optical signals received by the telescope and generates corresponding electric signals as the background signals.

5. The lidar of any of claims 1 to 4, wherein the four-quadrant shutter mechanism further comprises:

the supporting plate is arranged on a lens barrel of the telescope, a bearing surface is formed above the lens barrel, and the rotating mechanism is arranged on the bearing surface of the supporting plate.

6. The lidar of claim 5, wherein the rotating mechanism comprises four sets, each set of rotating mechanism is correspondingly connected with the four light shielding plates, and each set of rotating mechanism comprises:

the rotating shaft is connected with one of the shielding plates;

the positioning seat is arranged on the bearing surface of the supporting plate, a bearing is arranged on the positioning seat, and the rotating shaft is arranged in the bearing;

the motor is arranged on the supporting plate, and the running state of the motor is controlled by the control system;

the driving wheel is coupled with the motor shaft and driven by the motor to rotate;

and the driven wheel is meshed with the driving wheel and is in shaft connection with the rotating shaft, and when the motor drives the driving wheel to rotate, the driving wheel drives the driven wheel to rotate so as to drive the shielding plate to open and close.

7. The lidar of claim 6, wherein the motor is mounted below the bearing surface of the support plate, and a driving shaft of the motor extends above the bearing surface through the bearing surface and is coupled to the driving wheel, and an axis of the driving wheel is perpendicular to an axis of the driven wheel.

8. The lidar of claim 6, wherein four sets of the rotating mechanisms are disposed on four sides of the carrying surface of the support plate; in each group of rotating mechanisms, the rotating shaft is parallel to the bearing surface of the supporting plate; the positioning seats comprise two positioning seats which are respectively arranged at two ends of the rotating shaft.

9. The lidar of any of claims 1 to 4, further comprising:

the beam expander is used for compressing the divergence angle of the laser beam emitted by the laser and then emitting the compressed laser beam to the reflector;

the transmitting system support plate is arranged on the lens cone of the telescope and is positioned at one side of the telescope; the laser, the beam expanding lens, the reflecting mirror and the adjustable electric control lens frame are all arranged on the transmitting system carrier plate; and configuring the laser radar into a coaxial laser radar or a paraxial laser radar by adjusting the adjustable electric control lens frame.

10. Lidar according to any of claims 1 to 4, wherein the control system comprises:

the acquisition card is used for acquiring the electric signal output by the receiving optical path system and converting the electric signal into a digital signal;

the industrial personal computer receives the digital signals output by the acquisition card and respectively generates control signals for controlling the actions of the rotating mechanism and the adjustable electric control mirror bracket;

and the driving circuit receives the control signal output by the industrial personal computer so as to drive the rotating mechanism or the adjustable electric control mirror bracket to act.