# US 2021/0239806 A1 · Selecting lidar pulse detector depending on pulse type > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0239806 A1 - Document ID: US20210239806A1 - Status: Published application - Kind: A1 - Application number: 17/092,162 - Filed: 2020-11-06 - Published: 2021-08-05 - Earliest claimed: 2018-03-20 - Assignees: Zoox, Inc. - Applicants: Zoox, Inc. - Inventors: Subasingha Shaminda Subasingha; Riley Andrews; Turhan Karadeniz; Ravi Sankar Mahankali - Web page: https://patentgrep.com/patent/US20210239806A1 ## CPC - G01S 7/484: Transmitters - G01S 7/4866: {by fitting a model or function to the received signal} - G01S 7/4865: Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak (peak detection in noise, signal conditioning G01S7/487) - G01S 7/4868: {Controlling received signal intensity or exposure of sensor} - G01S 7/4873: {by deriving and controlling a threshold value} - G01S 17/10: using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32) - G01S 7/4863: Detector arrays, e.g. charge-transfer gates - G01S 7/497: Means for monitoring or calibrating - 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 time delay of arrival (TDOA) between a time that a light pulse was emitted to a time that a pulse reflected off an object was received at a light sensor may be determined for saturated signals by using an edge of the saturated signal, rather than a peak of the signal, for the TDOA calculation. The edge of the saturated signal may be accurately estimated by fitting a first polynomial curve to data points of the saturated signal, defining an intermediate magnitude threshold based on the polynomial curve, fitting a second polynomial curve to data points near an intersection of the first polynomial curve and the intermediate threshold, and identifying an intersection of the second polynomial curve and the intermediate threshold as the rising edge of the saturated signal. ## Claims ### Claim 1 One or more non-transitory computer-readable media storing instructions that, when executed, cause one or more processors to perform operations comprising: receiving, from a light sensor, a signal indicating light reflected from an object in an environment, the signal defined by a series of samples; determining a distance to the object based, at least in part, on a time delay of arrival (TDOA) between emitting a light pulse and a time associated with a rising edge of the signal, wherein determining the TDOA includes: identifying, from among the series of samples, a maximum sample, wherein the maximum sample comprises an earliest received sample associated with a maximum magnitude of the signal; fitting a first polynomial curve to at least the maximum sample; defining an intermediate threshold magnitude based, at least in part, on the first polynomial curve; fitting a second polynomial curve to at least two intermediate samples proximate to the intermediate threshold magnitude; and determining, based at least in part on a sample index associated with an intersection of the second polynomial curve with the intermediate threshold magnitude, the TDOA. ### Claim 2 (depends on 1) The one or more non-transitory computer-readable media of claim 1, wherein fitting the first polynomial curve to the maximum sample comprises fitting the first polynomial curve to the maximum sample and to at least a sample proximate the maximum sample in the series. ### Claim 3 (depends on 1) The one or more non-transitory computer-readable media of claim 1, wherein fitting the first polynomial curve to the maximum sample comprises fitting the first polynomial curve to the maximum sample and to at least a sample preceding the maximum sample in the series and a sample following the maximum sample in the series. ### Claim 4 (depends on 1) The one or more non-transitory computer-readable media of claim 1, wherein the at least two intermediate samples are along the rising edge of the signal. ### Claim 5 (depends on 1) The one or more non-transitory computer-readable media of claim 1, wherein the sample index includes a fractional sample index. ### Claim 6 (depends on 1) The one or more non-transitory computer-readable media of claim 1, wherein the intermediate threshold magnitude is a percentage between 40 and 80% of a maximum value of the first polynomial curve. ### Claim 7 (depends on 1) The one or more non-transitory computer-readable media of claim 1, wherein the first polynomial curve is associated with a second-degree or third-degree polynomial function and the second polynomial curve is associated with a different second-degree or different third-degree polynomial function. ### Claim 8 (depends on 1) The one or more non-transitory computer-readable media of claim 1, the operations further comprising: determining that the signal is saturated based, at least in part, on a magnitude associated with the series of samples meeting or exceeding a threshold magnitude. ### Claim 9 A method comprising: receiving a signal indicative of light received by a light sensor, the signal comprising a series of samples; determining a maximum magnitude of the signal and a first sample in the series associated with the maximum magnitude; fitting a first polynomial curve to the first sample and a sample proximate the first sample; defining an intermediate threshold magnitude based, at least in part, on the first polynomial curve; fitting a second polynomial curve to at least two intermediate samples proximate to the intermediate threshold magnitude; determining a sample index that corresponds to an intersection of the second polynomial curve with the intermediate threshold magnitude; and determining a distance based, at least in part, on the sample index. ### Claim 10 (depends on 9) The method of claim 9, wherein the at least two intermediate samples are along a rising edge of the signal. ### Claim 11 (depends on 9) The method of claim 9, wherein the sample index includes a fractional sample index. ### Claim 12 (depends on 9) The method of claim 9, wherein the intermediate threshold magnitude is a percentage between 40 and 80% of a maximum value of the first polynomial curve. ### Claim 13 (depends on 9) The method of claim 9, wherein the first polynomial curve is associated with a second-degree or third-degree polynomial function and the second polynomial curve is associated with a different second-degree or different third-degree polynomial function. ### Claim 14 (depends on 9) The method of claim 9, further comprising: determining that the signal is saturated based, at least in part, on a magnitude associated with the series of samples meeting or exceeding a threshold magnitude. ### Claim 15 A system comprising: a light sensor; control circuitry communicatively coupled to the light sensor, the control circuitry being configured to perform operations comprising: receive a signal indicative of light received at the light sensor, the signal being discretized into a series of samples; determine a first sample of the series of samples having a maximum magnitude; fit a first polynomial curve to the first sample and a sample proximate the first sample in the series; define an intermediate threshold magnitude based, at least in part, on the first polynomial curve; and determine a time delay of arrival (TDOA) based on the intermediate threshold magnitude. ### Claim 16 (depends on 15) The system of claim 15, wherein the intermediate threshold magnitude is a percentage between 40 and 80% of a maximum value of the first polynomial curve. ### Claim 17 (depends on 15) The system of claim 15, wherein the operations further comprise: determine that the signal is saturated based, at least in part, on a magnitude associated with the series of samples meeting or exceeding a threshold magnitude. ### Claim 18 (depends on 15) The system of claim 15, wherein the operations further comprise: identify three or more intermediate samples of the signal that are proximate to a first intersection of the signal and the intermediate threshold magnitude; fit a second polynomial curve to the three or more intermediate samples; and determine a second intersection of the second polynomial curve and the intermediate threshold magnitude and a time corresponding to the intersection, wherein the TDOA is based on the time. ### Claim 19 (depends on 18) The system of claim 18, wherein the three or more intermediate samples are along a rising edge of the signal. ### Claim 20 (depends on 18) The system of claim 18, wherein the first polynomial curve is associated with a second-degree or third-degree polynomial function and the second polynomial curve is associated with a different second-degree or different third-degree polynomial function.