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US-20260126549-A1 - DISTANCE MEASUREMENT METHOD AND SYSTEM FOR LIDAR

US20260126549A1US 20260126549 A1US20260126549 A1US 20260126549A1US-20260126549-A1

Abstract

A distance measurement method and system for LIDAR are provided, which includes: generating a frequency-swept light beam; splitting the frequency-swept light beam into a signal light beam and a local-oscillator light beam, where each of the signal light beam and the local-oscillator light beam includes first and second frequency-up phases, first and second frequency-down phases, slope of the first frequency-up phase is different from that of the second frequency-up phase, slope of the first frequency-down phase is different from that of the second frequency-down phase; emitting a signal light beam; receiving a reflected light beam; detecting beat frequencies of the frequency-up phases and the frequency-down phases between the local-oscillator light beam and the reflected light beam; and using two of beat frequencies of the frequency-up phases and frequency-down phases to measure the speed of the target object and/or the distance between the target object and the LIDAR.

Inventors

  • Pingjie XIA
  • CHUNLIN YANG
  • Jie Sun
  • Tianbo Sun

Assignees

  • BEIJING MORELITE TECHNOLOGY CO. LTD.

Dates

Publication Date
20260507
Application Date
20251104
Priority Date
20241106

Claims (10)

  1. 1 . A distance measurement method for LIDAR, comprising: generating a frequency-swept light beam; splitting the frequency-swept light beam into a signal light beam and a local-oscillator light beam, where each of the signal light beam and the local-oscillator light beam includes a first frequency-up phase, a second frequency-up phase, a first frequency-down phase, and a second frequency-down phase, the slope of the first frequency-up phase is different from that of the second frequency-up phase, and the slope of the first frequency-down phase is different from that of the second frequency-down phase; emitting the signal light beam; receiving the reflected light beam generated by the reflection of the signal light beam when it encounters a target object; detecting the beat frequencies of the first frequency-up phase, the second frequency-up phase, the first frequency-down phase, and the second frequency-down phase between the local-oscillator light beam and the reflected light beam; and using the beat frequencies of the first frequency-up phase and the second frequency-up phase to measure the speed of the target object and/or the distance between the target object and the LIDAR; or using the beat frequencies of the first frequency-down phase and the second frequency-down phase to measure the speed of the target object and/or the distance between the target object and the LIDAR.
  2. 2 . The distance measurement method according to claim 1 , wherein using the beat frequencies of the first frequency-up phase and the second frequency-up phase to measure the distance between the target object and the LIDAR comprises: obtaining the distance D between the target object and the LIDAR using the following formula: D=k 0 ×(f bu2 −f bu1 )/(k f −1), where k 0 is a preset value related to the LIDAR, k f is a parameter related to the ratio of the slope of the first frequency-up phase to the slope of the second frequency-up phase, f bu1 is the beat frequency of the first frequency-up phase, and f bu2 is the beat frequency of the second frequency-up phase.
  3. 3 . The distance measurement method according to claim 1 , wherein using the beat frequencies of the first frequency-down phase and the second frequency-down phase to measure the distance between the target object and the LIDAR comprises: obtaining the distance D between the target object and the LIDAR using the following formula: D=k 0 ×(f bd2 −f bd1 )/(k f −1), where k 0 is a preset value related to the LIDAR, k f is a parameter related to the ratio of the slope of the first frequency-down phase to the slope of the second frequency-down phase, f bd1 is the beat frequency of the first frequency-down phase, and f bd2 is the beat frequency of the second frequency-down phase.
  4. 4 . The distance measurement method according to claim 1 , wherein using the beat frequencies of the first frequency-up phase and the second frequency-up phase to measure the speed of the target object comprises: obtaining the speed V of the target object using the following formula: V=k 1 ×(k f ×f bu1 −f bu2 )/(k f −1), where k 1 is a preset value related to the LIDAR, k f is a parameter related to the ratio of the slope of the first frequency-up phase to the slope of the second frequency-up phase, f bu1 is the beat frequency of the first frequency-up phase, and f bu2 is the beat frequency of the second frequency-up phase.
  5. 5 . The distance measurement method according to claim 1 , wherein using the beat frequencies of the first frequency-down phase and the second frequency-down phase to measure the speed of the target object comprises: obtaining the speed V of the target object using the following formula: V=k 1 ×(k f ×f bd1 −f bd2 )/(k f −1), where k 1 is a preset value related to the LIDAR, k f is a parameter related to the ratio of the slope of the first frequency-down phase to the slope of the second frequency-down phase, f bd1 is the beat frequency of the first frequency-down phase, and f bd2 is the beat frequency of the second frequency-down phase.
  6. 6 . A distance measurement system for LIDAR, comprising: a laser source configured to generate a frequency-swept light beam; a beam splitter configured to split the frequency-swept light beam into a signal light beam and a local-oscillator light beam, where each of the signal light beam and the local-oscillator light beam includes a first frequency-up phase, a second frequency-up phase, a first frequency-down phase, and a second frequency-down phase, the slope of the first frequency-up phase is different from that of the second frequency-up phase, and the slope of the first frequency-down phase is different from that of the second frequency-down phase; an optical transceiver configured to emit the signal light beam and receive the reflected light beam generated by the reflection of the signal light beam when it encounters a target object; a frequency mixer configured to perform optical frequency mixing between the local-oscillator light beam and the reflected light beam; a balanced detector configured to obtain the beat frequency electrical signal between the local-oscillator light beam and the reflected light beam; a detector configured to obtain the beat frequency electrical signal from the balanced detector, and detect the beat frequencies of the first frequency-up phase, the second frequency-up phase, the first frequency-down phase, and the second frequency-down phase between the local-oscillator light beam and the reflected light beam according to the beat frequency electrical signal; and a measuring device configured to use the beat frequencies of the first frequency-up phase and the second frequency-up phase to measure the speed of the target object and/or the distance between the target object and the LIDAR; or use the beat frequencies of the first frequency-down phase and the second frequency-down phase to measure the speed of the target object and/or the distance between the target object and the LIDAR.
  7. 7 . The distance measurement system according to claim 6 , wherein the measuring device is specifically configured to: obtain the distance D between the target object and the LIDAR using the following formula: D=k 0 ×(f bu2 −f bu1 )/(k f −1), where k 0 is a preset value related to the LIDAR, k f is a parameter related to the ratio of the slope of the first frequency-up phase to the slope of the second frequency-up phase, f bu1 is the beat frequency of the first frequency-up phase, and f bu2 is the beat frequency of the second frequency-up phase.
  8. 8 . The distance measurement system according to claim 6 , wherein the measuring device is specifically configured to: obtain the distance D between the target object and the LIDAR using the following formula: D=k 0 ×(f bd2 −f bd1 )/(k f −1), where k 0 is a preset value related to the LIDAR, k f is a parameter related to the ratio of the slope of the first frequency-down phase to the slope of the second frequency-down phase, f bd1 is the beat frequency of the first frequency-down phase, and f bd2 is the beat frequency of the second frequency-down phase.
  9. 9 . The distance measurement system according to claim 6 , wherein the measuring device is specifically configured to: obtain the speed V of the target object using the following formula: V=k 1 ×(k f ×f bu1 −f bu2 )/(k f −1), where k 1 is a preset value related to the LIDAR, k f is a parameter related to the ratio of the slope of the first frequency-up phase to the slope of the second frequency-up phase, f bu1 is the beat frequency of the first frequency-up phase, and f bu2 is the beat frequency of the second frequency-up phase.
  10. 10 . The distance measurement system according to claim 6 , wherein the measuring device is specifically configured to: obtain the speed V of the target object using the following formula: V=k 1 ×(k f ×f bd1 −f bd2 )/(k f −1), where k 1 is a preset value related to the LIDAR, k f is a parameter related to the ratio of the slope of the first frequency-down phase to the slope of the second frequency-down phase, f bd1 is the beat frequency of the first frequency-down phase, and f bd2 is the beat frequency of the second frequency-down phase.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present application claims a priority to Chinese Patent Application No. 202411571739.8 filed on Nov. 6, 2024, the disclosures of which are incorporated in their entirety by reference herein. TECHNICAL FIELD The present application relates to the technical field of LIDAR, and specifically to a distance measurement method and system for LIDAR. BACKGROUND Light Detection And Ranging (LIDAR) can accurately measure the position (distance and angle), motion state (speed, vibration, and attitude) and shape of a target object, as well as detect, identify, distinguish, and track the target object. Lidar can be divided into pulse LIDAR and frequency-modulated continuous-wave (FMCW) LIDAR according to its working mode. A typical FMCW LIDAR emits a laser beam and uses a detector to receive the reflected beam of the target object from the surrounding environment, thereby calculating information such as the distance and speed of the target object. However, the reflected beam used to calculate distance and speed includes an optical Doppler frequency shift introduced by the movement of the target object. When the speed of the target object is relatively high, the frequency shift caused by the Doppler effect is greater than the frequency shift caused by the flight time of the reflected beam. This leads to errors in the calculation of short-distance information and thus results in a measurement blind area. SUMMARY In view of the problems of the related LIDAR, the present application provides a distance measurement method and system for LIDAR. In a first aspect, the distance measurement method for LIDAR includes: generating a frequency-swept light beam; splitting the frequency-swept light beam into a signal light beam and a local-oscillator light beam, where each of the signal light beam and the local-oscillator light beam includes a first frequency-up phase, a second frequency-up phase, a first frequency-down phase, and a second frequency-down phase, the slope of the first frequency-up phase is different from that of the second frequency-up phase, and the slope of the first frequency-down phase is different from that of the second frequency-down phase; emitting the signal light beam; receiving the reflected light beam generated by the reflection of the signal light beam when it encounters a target object; detecting the beat frequencies of the first frequency-up phase, the second frequency-up phase, the first frequency-down phase, and the second frequency-down phase between the local-oscillator light beam and the reflected light beam; and using two of the beat frequencies of the first frequency-up phase, the second frequency-up phase, the first frequency-down phase, and the second frequency-down phase to measure the speed of the target object and/or the distance between the target object and the LIDAR. Optionally, using two of the beat frequencies of the first frequency-up phase, the second frequency-up phase, the first frequency-down phase, and the second frequency-down phase to measure the speed of the target object and/or the distance between the target object and the LIDAR includes: using the beat frequencies of the first frequency-up phase and the second frequency-up phase to measure the speed of the target object and/or the distance between the target object and the LIDAR; or using the beat frequencies of the first frequency-down phase and the second frequency-down phase to measure the speed of the target object and/or the distance between the target object and the LIDAR. Optionally, using the beat frequencies of the first frequency-up phase and the second frequency-up phase to measure the distance between the target object and the LIDAR includes: obtaining the distance D between the target object and the LIDAR using the following formula: D=k0×(fbu2−fbu1)/(kf−1), where k0 is a preset value related to the LIDAR, kf is a parameter related to the ratio of the slope of the first frequency-up phase to the slope of the second frequency-up phase, fbu1 is the beat frequency of the first frequency-up phase, and fbu2 is the beat frequency of the second frequency-up phase. Optionally, k0=T×c4×fB⁢1,kf=fB⁢2fB⁢1 where fB1 is the frequency-sweeping bandwidth of the linear frequency modulation of the first triangular wave, fB2 is the frequency-sweeping bandwidth of the linear frequency modulation of the second triangular wave, T is the period of the frequency-up and frequency-down sweeps, and c is the speed of light in a vacuum. Optionally, using the beat frequencies of the first frequency-down phase and the second frequency-down phase to measure the distance between the target object and the LIDAR includes: obtaining the distance D between the target object and the LIDAR using the following formula: D=k0×(fbd2−fbd1)/(kf−1), where k0 is a preset value related to the LIDAR, kf is a parameter related to the ratio of the slope of the first frequency-down phase to the slope of the second frequenc