# US 10,768,282 B2 · Method and system for laser phase tracking for internal reflection subtraction in phase-encoded LIDAR > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,768,282 B2 - Document ID: US10768282B2 - Status: Granted - Kind: B2 - Application number: 16/681,663 - Filed: 2019-11-12 - Published: 2020-05-14 - Granted: 2020-09-08 - Earliest claimed: 2018-11-13 - Assignees: Blackmore Sensors & Analytics, LLC - Applicants: Blackmore Sensors & Analytics, LLC - Inventors: Stephen C. Crouch; Emil Kadlec; Krishna Rupavatharam - Web page: https://patentgrep.com/patent/US10768282B2 ## CPC - G01S 7/4817: {relating to scanning} - G01S 7/4915: Time delay measurement, e.g. operational details for pixel components (signal extraction and conditioning G01S7/493); Phase measurement - G01S 7/4814: {of transmitters alone} - G01S 7/4816: {of receivers alone} - G01S 7/4876: {by removing unwanted signals (G01S7/495 takes precedence)} - G01S 7/4914: of detector arrays, e.g. charge-transfer gates - G01S 7/4917: {superposing optical signals in a photodetector, e.g. optical heterodyne detection} - G01S 17/26: wherein the transmitted pulses use a frequency-modulated or phase-modulated carrier wave, e.g. for pulse compression of received signals - G01S 17/34: using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal - G01S 17/36: with phase comparison between the received signal and the contemporaneously transmitted signal - G01S 17/931: of land vehicles - G01S 7/4812: {transmitted and received beams following a coaxial path} - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES ## Abstract A system and method for optical detection in autonomous vehicles includes modulating an optical signal from a laser to generate a modulated optical signal and transmitting the modulated optical signal toward an object. The system and method include receiving, responsive to transmitting the modulated optical signal, a returned optical signal and mixing the returned optical signal with a reference optical signal associated with the optical signal from the laser to generate a mixed optical signal and detecting the mixed optical signal to generate an electrical signal. Based on the electrical signal and the modulated optical signal, a parameter of an internal reflection of the returned optical signal from one or more optical components is determined, which may be used to operate a vehicle. ## Claims ### Claim 1 A system comprising: a laser that provides a plurality of optical signals; a modulator that modulates the plurality of optical signals from the laser to generate a plurality of modulated optical signals; an optical coupler that generates a plurality of reference optical signals, each associated with a respective optical signal of the plurality of optical signals from the laser, transmits the plurality of modulated optical signals into free space, and receives a plurality of returned optical signals responsive to transmitting the plurality of modulated optical signals into the free space; an optical mixer that mixes each of the plurality of returned optical signals with a respective reference optical signal of the plurality of reference optical signals to generate a respective mixed optical signal of a plurality of mixed optical signals; an optical detector that detects each mixed optical signal of the plurality of mixed optical signals to generate a respective electrical signal of a plurality of electrical signals; and a processor that: determines a first signal by adjusting a parameter of a first electrical signal of the plurality of electrical signals; determines a second signal by adjusting a parameter of a second electrical signal of the plurality of electrical signals; determines an internal reflection signal indicative of an internal reflection of one or more optical components based on the first signal and the second signal; determines a third signal by adjusting a third electrical signal of the plurality of electrical signals using the internal reflection signal; and operates a vehicle based on the third signal. ### Claim 2 (depends on 1) The system of claim 1, wherein the parameter of the first electrical signal and the parameter of the second electrical signal are each selected from at least one of a phase, an amplitude, a frequency, or an angular frequency. ### Claim 3 (depends on 1) The system of claim 1, wherein the modulator modulates the plurality of reference optical signals prior to mixing each of the returned optical signals with the respective reference optical signal of the plurality of reference optical signals. ### Claim 4 (depends on 1) The system of claim 1, wherein the plurality of optical signals are modulated based on a sequence of phases of each respective optical signal. ### Claim 5 (depends on 4) The system of claim 4, wherein the optical coupler transmits the plurality of modulated optical signals into free space for each of a first plurality of measurements, and receives each of the returned optical signals for each of the first plurality of measurements. ### Claim 6 (depends on 5) The system of claim 5, wherein the optical mixer generates the plurality of mixed optical signals for each of the first plurality of measurements, wherein the optical detector generates the respective electrical signal of the plurality of electrical signals for each of the first plurality of measurements. ### Claim 7 (depends on 6) The system of claim 6, wherein the parameter of the first electrical signal and the second electrical signal each comprise a phase of the internal reflection signal for each of the first plurality of measurements. ### Claim 8 (depends on 7) The system of claim 7, wherein the processor determines a parameter of the internal reflection signal based on a dot product measurement. ### Claim 9 (depends on 7) The system of claim 7, wherein the processor determines the parameter of the internal reflection signal by: determining an average over a second plurality of measurements including one or more measurements of the first plurality of measurements of the electrical signal, wherein the average is determined based at least in part on the phase of the internal reflection signal for each of the second plurality of measurements; and determining a corrected return signal based at least in part on (i) the average over the second plurality of measurements and (ii) the electrical signal for at least one of the first plurality of measurements. ### Claim 10 (depends on 9) The system of claim 9, wherein the processor operates the vehicle based on the corrected return signal. ### Claim 11 (depends on 1) The method of claim 1, wherein the plurality of optical signals are modulated based on a sequence of phases of each respective optical signal. ### Claim 12 (depends on 11) The method of claim 11, wherein transmitting the modulated optical signal toward the object comprises transmitting the plurality of modulated optical signals for each of a first plurality of measurements, wherein receiving the plurality of returned optical signals comprises receiving each of the returned optical signals for each of the first plurality of measurements. ### Claim 13 (depends on 12) The method of claim 12, wherein the plurality of mixed optical signals are generated for each of the first plurality of measurements, wherein the respective electrical signal of the plurality of electrical signals is generated for each of the first plurality of measurements. ### Claim 14 (depends on 13) The method of claim 13, wherein the parameter of the first electrical signal and the second electrical signal each comprises a phase of the internal reflection signal for each of the first plurality of measurements. ### Claim 15 (depends on 14) The method of claim 14, wherein determining a parameter of the internal reflection signal further comprises determining the parameter of the internal reflection signal based on a dot product measurement. ### Claim 16 (depends on 14) The method of claim 14, wherein determining the parameter of the internal reflection signal comprises: determining an average over a second plurality of including one or more measurements of the first plurality of measurements of the electrical signal, wherein the average is determined based at least in part on the phase of the internal reflection for each of the second plurality of measurements; and determining a corrected return signal based at least in part on (i) the average over the second plurality of measurements and (ii) the electrical signal for at least one of the first plurality of measurements. ### Claim 17 (depends on 16) The method of claim 16, wherein operating the vehicle comprises operating the vehicle based on the corrected return signal. ### Claim 18 A method comprising: modulating a plurality of optical signals from a laser to generate a plurality of modulated optical signals; transmitting the plurality of modulated optical signals into free space; receiving, responsive to transmitting the plurality of modulated optical signals, a plurality of returned optical signals; mixing each of the returned optical signals with a respective reference optical signal of the plurality of reference optical signals to generate a respective mixed optical signal of a plurality of mixed optical signals; detecting each mixed optical signal of the plurality of mixed optical signals to generate a respective electrical signal of the plurality of electrical signals; determining a first signal by adjusting a parameter of a first electrical signal of the plurality of electrical signals; determining a second signal by adjusting a parameter of a second electrical signal of the plurality of electrical signals; determining an internal reflection signal indicative of an internal reflection of one or more optical components based on the first signal and the second signal; determining a third signal by adjusting a third electrical signal of the plurality of electrical signals using the internal reflection signal; and operating, based on the third signal, a vehicle. ### Claim 19 (depends on 1) The method of claim 1, wherein the parameter of the first electrical signal and the parameter of the second electrical signal are each selected from at least one of a phase, an amplitude, a frequency, or an angular frequency. ### Claim 20 (depends on 1) The method of claim 1, further comprising modulating the plurality of reference optical signals prior to mixing each of the returned optical signals with the respective reference optical signal of the plurality of reference optical signals.