CN-116381710-B - Three-dimensional positioning laser radar and three-dimensional detection method thereof

CN116381710BCN 116381710 BCN116381710 BCN 116381710BCN-116381710-B

Abstract

The invention discloses a three-dimensional positioning laser radar and a three-dimensional detection method thereof, wherein a pulse laser emits laser beams to a target object, a polarization beam splitter emits the laser beams to a first lens and an avalanche photodiode respectively, the laser beams are emitted to a second lens after passing through the first lens, the laser beams are emitted to the target object after passing through the second lens, the avalanche photodiode converts received pulse light signals into electric signals and transmits the electric signals to a time-dependent single photon counter, the light field signals of the target object are collected through a lens and are transmitted to the first beam splitter, the first beam splitter and the second beam splitter generate first beams and second beams after splitting, the first beams and the second beams are split by the corresponding beam splitters to obtain four paths of beams, the four paths of beams are transmitted through respective corresponding light paths to generate electric signals and are transmitted to four receiving ports of the time-dependent single photon counter, and three-dimensional spatial position prediction of the target object is realized according to the received four paths of signals.

Inventors

SUN BAOQING
ZHANG CHENG
YIN YONGKAI
ZHANG YU
WANG HONGJIE

Assignees

山东大学

Dates

Publication Date: 20260512
Application Date: 20230411

Claims (10)

1. A three-dimensional positioning laser radar is characterized by comprising a pulse laser; The pulse laser emits laser beams to a target object, the laser beams are emitted to the polarization beam splitter through the half-wave plate, the polarization beam splitter emits the laser beams to the first lens and the avalanche photodiode respectively, the laser beams are emitted to the second lens after passing through the first lens, and are emitted to the target object after passing through the second lens, and the avalanche photodiode converts received pulse light signals into electric signals and transmits the electric signals to the time-related single photon counter; The optical field signal of the target object is collected through a lens and sent to a first beam splitter, and a first light beam and a second light beam are generated after the light beam is split by the first beam splitter, wherein the first light beam is input into the second beam splitter, and the first light beam is processed by the second beam splitter to obtain a third light beam and a fourth light beam; the third, fourth, fifth and sixth light beams are respectively transmitted through respective corresponding light paths, wherein the light paths comprise a mask, an optical filter, a lens, an optical fiber and a single photon detector which are sequentially connected, and after the single photon detector of each light path detects photons, an electric signal is generated and transmitted to four receiving ports of a time-related single photon counter; the time-dependent single photon counter transmits the received signals to a computer, and the computer predicts the three-dimensional space position of the target object according to the received four paths of signals, and specifically comprises the following steps: the first, second, third and fourth masks are used for realizing the modulation process of the reflected light of the scene, and the corresponding mask modulation functions are respectively used , , And A representation; Moreover, as the four masks are symmetrically arranged in pairs, the transmittance of the two masks which are symmetrically arranged is superposed to be 1; Therefore, the barycenter coordinates of the lateral space of the target object in the scene ) Expressed as: Wherein, the Representing the total light intensity value of the scene, And Representing the integrated intensity value of the scene with a particular reticle function, Is that The number of signal photons detected on the optical path, A two-dimensional density function of the detection area; And correcting the obtained barycenter coordinates through a mapping table to finally obtain the accurate transverse space coordinates of the target object.
2. The three-dimensional positioning lidar of claim 1, wherein the polarizing beam splitter, the first beam splitter, the second beam splitter, and the third beam splitter are configured to disperse the laser beam, and wherein the polarizing beam splitter is further configured to transmit a portion of the pulsed laser energy to an avalanche photodiode configured to detect the pulsed light reflected by the polarizing beam splitter and generate an electrical signal, and further configured to provide a synchronization signal for the emission of the laser pulses to an associated single photon counter.
3. A three-dimensional positioning lidar as defined in claim 1 wherein the first, second and third beam splitters are implemented with 50:50 beam splitters, the first, second and third beam splitters equally dividing the received signal into four paths.
4. A three-dimensional positioning lidar as defined in claim 1 wherein the first and second lenses have different focal lengths, the first and second lenses being configured to adjust the divergence angle of the laser beam.
5. The three-dimensional positioning laser radar according to claim 1, wherein the third, fourth, fifth and sixth light beams are respectively transmitted through corresponding light paths, the light paths comprise a mask, an optical filter, a lens, an optical fiber and a single photon detector which are sequentially connected, the single photon detector of each light path generates an electric signal after detecting photons and transmits the electric signal to four receiving ports of a time-related single photon counter, and the third light beam is transmitted to the first single photon detector through a first mask, a first optical filter, a third lens and a first optical fiber, and the generated signal is transmitted to a first stop channel of the time-related single photon counter; the fourth light beam is transmitted to a second single photon detector through a second mask plate, a second optical filter, a fourth lens and a second optical fiber, and the generated signal is transmitted to a second stop channel of the time-dependent single photon counter; the fifth light beam is transmitted to a third single photon detector through a third mask plate, a third optical filter, a fifth lens and a third optical fiber, and the generated signal is transmitted to a third stop channel of the time-dependent single photon counter; The sixth light beam is transmitted to a fourth single photon detector through a fourth mask plate, a fourth optical filter, a sixth lens and a fourth optical fiber, and the generated signal is transmitted to a fourth stop channel of the time-dependent single photon counter; The preparation processes of the first mask, the second mask, the third mask and the fourth mask are consistent, and differences exist in the placement directions of the four masks, wherein the gray scales of the first mask and the second mask are symmetrically distributed relative to the vertical direction, and the gray scales of the third mask and the fourth mask are symmetrically distributed relative to the horizontal direction.
6. The three-dimensional detection method using the three-dimensional positioning lidar according to claim 1, comprising: The pulse laser emits laser beams to a target object, the laser beams are emitted to the polarization beam splitter through the half-wave plate, the polarization beam splitter emits the laser beams to the first lens and the avalanche photodiode respectively, the laser beams are emitted to the second lens after passing through the first lens, and are emitted to the target object after passing through the second lens, and the avalanche photodiode converts received pulse light signals into electric signals and transmits the electric signals to the time-related single photon counter; The optical field signal of the target object is collected through a lens and sent to a first beam splitter, and a first light beam and a second light beam are generated after the light beam is split by the first beam splitter, wherein the first light beam is input into the second beam splitter, and the first light beam is processed by the second beam splitter to obtain a third light beam and a fourth light beam; The third, fourth, fifth and sixth light beams are respectively transmitted through respective corresponding light paths, the light paths comprise a mask, an optical filter, a lens, an optical fiber and a single photon detector which are sequentially connected, after the single photon detector of each light path detects photons, electric signals are generated and transmitted to four receiving port time-related single photon counters of the time-related single photon counter, the receiving signals are transmitted to a computer, and the computer predicts the three-dimensional space position of a target object according to the received four paths of signals.
7. The three-dimensional detection method of a three-dimensional positioning lidar of claim 6, wherein the method further comprises: Transmitting laser beams to a sample target object with a known three-dimensional space actual position by using the three-dimensional positioning laser radar to obtain a three-dimensional space prediction position of the sample target object by a computer, and further obtaining a mapping table of the three-dimensional space actual position of the sample target object and the three-dimensional space prediction position of the sample target object; Transmitting laser beams to a target object to be detected with unknown three-dimensional space position by using the three-dimensional positioning laser radar to obtain a three-dimensional space prediction position of the target object to be detected by a computer; Based on the mapping relation table, searching a three-dimensional space actual position corresponding to the three-dimensional space predicted position of the target object to be detected from the table, and correcting the three-dimensional space predicted position of the target object to be detected according to the searched three-dimensional space actual position to obtain a corrected three-dimensional space predicted position.
8. The three-dimensional detection method of the three-dimensional positioning laser radar according to claim 6, wherein the time-dependent single photon counter transmits the received signal to a computer, and the computer predicts the three-dimensional spatial position of the target object according to the received four paths of signals, and specifically comprises: Firstly, performing transverse space position positioning based on mask modulation, namely establishing a two-dimensional Cartesian coordinate system according to the coordinates of pixels for a gray level image, and further using a two-dimensional density function To express gray scale, to use mask with uniform change of transmittance to modulate the collected photons, and finally, to detect the number of signal photons through the mask single photon detector Expressed as: Wherein, the As a function of the two-dimensional density of the detection zone, Is a modulation function of the mask plate, The abscissa of the pixel point is indicated, Representing the ordinate of the pixel point, Is a constant of planck, which is set to be the planck's constant, For the wavelength of the active light source used, Is a pattern index; Then, after the centroid coordinates of the transverse space of the target object are obtained through the signal photon counting and the transverse space centroid algorithm, determining the depth position of the target object according to the flight time of the selected signal photons: Selecting a signal light subset from the integrated photon time distribution histogram by a time window with a set size, and calculating the depth position of the target object by a time centroid method according to the time labels of the selected signal photons and the photon count on each label : Wherein, the In order to achieve the light velocity, the light beam is, As a time stamp of the time distribution histogram, - Is a time interval selected within the time distribution histogram, Is the first Photon count values on the individual time tags; And finally, combining the corrected transverse space position and depth position to finish the three-dimensional detection of the target object with high transverse space resolution and high frame rate.
9. The method for three-dimensional detection of a three-dimensional positioning lidar of claim 8, wherein the selecting a subset of signal light within the integrated photon time distribution histogram through the sized time window comprises: Aiming at a target object without environmental background, overlapping respective time distribution histograms of the four-beam light paths into an integrated time distribution histogram, selecting a time window with a set size, selecting a time region with the highest photon count in the integrated time distribution histogram by using the time window, recognizing that the time region with the highest photon count is a signal photon count, and then extracting signal photons received by the four-beam light paths by using the current time window to obtain a signal light subset.
10. A three-dimensional positioning lidar three-dimensional detection method according to claim 9, wherein the time distribution histograms of the four beam paths are each shown, wherein the abscissa represents the time of flight of the signal photons and the ordinate represents the count of signal photons having the same time of flight.

Description

Three-dimensional positioning laser radar and three-dimensional detection method thereof Technical Field The invention relates to the technical field of laser radar three-dimensional detection, in particular to a three-dimensional positioning laser radar and a three-dimensional detection method thereof. Background The statements in this section merely relate to the background of the present disclosure and may not necessarily constitute prior art. The laser radar is a mature three-dimensional detection technology at present, and has the advantages of high precision, long detection distance and the like. Therefore, the laser radar has been widely used in the fields of automatic navigation, environmental monitoring, military safety, and the like. Currently, the existing lidars can be roughly classified into three types of mechanical rotary lidars, semi-solid lidars and solid lidars. Scanning devices are arranged in the systems of the mechanical rotary laser radar and the semi-solid laser radar, so that scanning imaging is performed. Scanning imaging inevitably results in lower imaging frame rates, which cannot meet the needs of some real-time detected scenes. Furthermore, the scanning device may cause the lifetime of the lidar to be limited by the scanning device. The solid-state lidar can realize high frame rate imaging, which is a laser radar system for flash imaging, and the transverse resolution of the solid-state lidar system for flash imaging is determined by the size of a detector array, and the detector array of the solid-state lidar for flash imaging has small scale and high cost due to the limitation of technology. In some fields, for example, three-dimensional detection and positioning of a fast moving object are performed, three-dimensional imaging of the object is not required, and only the object is detected to obtain a three-dimensional space position of the object. Therefore, for scenes and fields that do not require imaging of targets but require real-time three-dimensional detection of fast moving targets, there is a need to design and invent a solid-state lidar with high lateral spatial resolution and high frame rate. Disclosure of Invention In order to solve the problems of low imaging frame rate and short service life of a scanning laser radar and the problem that the transverse resolution of a solid-state laser radar is limited by the size of a detector array, the invention provides a three-dimensional positioning laser radar and a three-dimensional detection method thereof, which realize the three-dimensional detection of a fast moving target with high transverse resolution and high frame rate on the basis of not imaging the target. In a first aspect, the present invention provides a three-dimensional positioning lidar; A three-dimensional positioning laser radar comprises a pulse laser; The pulse laser emits laser beams to a target object, the laser beams are emitted to the polarization beam splitter through the half-wave plate, the polarization beam splitter emits the laser beams to the first lens and the avalanche photodiode respectively, the laser beams are emitted to the second lens after passing through the first lens, and are emitted to the target object after passing through the second lens, and the avalanche photodiode converts received pulse light signals into electric signals and transmits the electric signals to the time-related single photon counter; The optical field signal of the target object is collected through a lens and sent to a first beam splitter, and a first light beam and a second light beam are generated after the light beam is split by the first beam splitter, wherein the first light beam is input into the second beam splitter, and the first light beam is processed by the second beam splitter to obtain a third light beam and a fourth light beam; the third, fourth, fifth and sixth light beams are respectively transmitted through respective corresponding light paths, wherein the light paths comprise a mask, an optical filter, a lens, an optical fiber and a single photon detector which are sequentially connected, and after the single photon detector of each light path detects photons, an electric signal is generated and transmitted to four receiving ports of a time-related single photon counter; The time-dependent single photon counter transmits the received signals to a computer, and the computer predicts the three-dimensional space position of the target object according to the received four paths of signals. In a second aspect, the invention provides a three-dimensional detection method of a three-dimensional positioning laser radar; A three-dimensional detection method of a three-dimensional positioning laser radar comprises the following steps: The pulse laser emits laser beams to a target object, the laser beams are emitted to the polarization beam splitter through the half-wave plate, the polarization beam splitter emits the laser beams to the first lens an