# US 11,994,586 B2 · Using time-of-flight and pseudo-random bit sequences to measure distance to object > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,994,586 B2 - Document ID: US11994586B2 - Status: Granted - Kind: B2 - Application number: 16/973,662 - Filed: 2019-06-04 - Published: 2021-07-01 - Granted: 2024-05-28 - Earliest claimed: 2018-06-22 - Assignees: Ams AG - Applicants: ams AG - Inventors: Christian Mautner; Daniel Furrer; Daniele Perenzoni; Robert Kappel - Web page: https://patentgrep.com/patent/US11994586B2 ## CPC - G01S 17/08: for measuring distance only (indirect measurement G01S17/46; active triangulation systems G01S17/48) - G01S 7/4808: {Evaluating distance, position or velocity data} - 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 7/487: Extracting wanted echo signals {, e.g. pulse 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 17/89: for mapping or imaging - 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 The present disclosure describes a method and apparatus for enabling an imaging sensor to perform Time-of-Flight measurements while requiring less histogram memory and in many cases less power consumption. A light source is operated to cause multiple light emissions and a coarse/estimated distance is determined based on a first echo received based on the first light emission. A histogram is saved and a fine distance is calculated from the coarse distance and data derived from the echo of a second light emission. ## Claims ### Claim 1 An apparatus comprising: an imaging sensor configured to perform a distance measurement; a camera configured to obtain a 2-D image of an environment; a memory; a light source; and control circuitry coupled to the imaging sensor, the camera, the memory and the light source, the control circuitry configured to cause a first light emission from the light source and a second light emission from the light source; wherein the imaging sensor is configured to detect a first echo resulting from the first light emission being reflected by an object and to detect a second echo resulting from the second light emission being reflected by the object; wherein the control circuitry is further configured to: determine, based on the first echo, an estimated distance to the object; identify, within the second echo, data corresponding to the estimated distance; generate a histogram using the identified data that corresponds to the estimated distance in combination with the 2-D image of the environment obtained from the camera; and store the histogram in the memory. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the control circuitry is further configured to calculate, based on the histogram a distance to the object. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the control circuitry is configured to: retrieve a non-ambiguity period associated with the first light emission; determine that the non-ambiguity period from the first light emission has been reached; and cause the second light emission after the non-ambiguity period has been reached. ### Claim 4 (depends on 1) The apparatus of claim 1, wherein the first light emission is a first light pulse and the second light emission is a second light pulse, and wherein the first light pulse is longer than the second light pulse. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the first light emission is modulated at a lower frequency than the second light emission. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the control circuitry is operable to store the histogram in the memory by performing one or more of: discarding data associated with light of the second echo that does not correspond to the estimated distance; and discarding data associated with light of the first echo. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the control circuitry is further configured to: retrieve a time period corresponding to maximum time between the first light emission and receiving any echo for the first light emission; cause, during the time period, a plurality of light emissions from the light source; and cause the light source to stop further light emissions after the time period has ended. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein the control circuitry is further configured to cause the second light emission and the plurality of light emissions in a sequence, wherein the sequence instructs the control circuitry to split the time period into a plurality of time periods and wherein the sequence instructs the control circuitry to cause emissions during some of the plurality of time periods without causing the emissions during other of the plurality of time periods. ### Claim 9 (depends on 8) The apparatus of claim 8, wherein: the image sensor is further operable to detect light comprising echoes for the plurality of light emissions and light from other light sources; and the control circuitry is further configured to: identify, based on the sequence of light emissions, echoes for the plurality of light emissions; and subtract, based on the sequence of light emissions, data values associated with signals representing the light from the other light sources. ### Claim 10 (depends on 8) The apparatus of claim 8, wherein the control circuitry is further configured to: store data corresponding to echoes for the plurality of light emissions in a histogram memory; and generate a measurement of distance to the object based on the data in the histogram memory. ### Claim 11 A method comprising: causing, using a light source, a first light emission and a second light emission; detecting using, an imaging sensor, a first echo resulting from the first light emission being reflected by an object and a second echo resulting from the second light emission being reflected by the object; obtaining a 2-D image of an environment using a camera; determining, based on the first echo, an estimated distance to the object; identifying, within the second echo, data corresponding to the estimated distance; generating a histogram using the identified data that corresponds to the estimated distance in combination with the 2-D image of the environment obtained from the camera; and storing the histogram in a memory. ### Claim 12 (depends on 11) The method of claim 11, further comprising calculating, based on the histogram, a distance to the object. ### Claim 13 (depends on 11) The apparatus of claim 11, further comprising: retrieving a non-ambiguity period associated with the first light emission; determining that the non-ambiguity period from the first light emission has been reached; and causing the second light emission after the non-ambiguity period has been reached. ### Claim 14 (depends on 11) The method of claim 11, wherein the first light emission is a first light pulse and the second light emission is a second light pulse, and wherein the first light pulse is longer than the second light pulse. ### Claim 15 (depends on 11) The method of claim 11, wherein the first light emission is modulated at a lower frequency than the second light emission. ### Claim 16 (depends on 11) The method of claim 11, wherein storing the histogram in the memory comprises: discarding data associated with light of the second echo that does not correspond to the estimated distance; and discarding data associated with light of the first echo. ### Claim 17 (depends on 11) The method of claim 11, further comprising: retrieving a time period corresponding to maximum time between the first light emission and receiving any echo for the first light emission; causing, during the time period, a plurality of light emissions from the light source; and causing the light source to stop further light emissions after the time period has ended. ### Claim 18 (depends on 17) The method of claim 17, further comprising causing the second light emission and the plurality of light emissions in a sequence, wherein the sequence instructs control circuitry to split the time period into a plurality of time periods and wherein the sequence instructs the control circuitry to cause emissions during some of the plurality of time periods without causing the emissions during other of the plurality of time periods. ### Claim 19 (depends on 18) The method of claim 18, further comprising: detecting, using the imaging sensor, light comprising echoes for the plurality of light emissions and light from other light sources; identifying, based on the sequence of light emissions, echoes for the plurality of light emissions; and subtract, based on the sequence of light emissions, data values associated with signals representing the light from the other light sources. ### Claim 20 (depends on 18) The method of claim 18, further comprising: storing data corresponding to echoes for the plurality of light emissions in a histogram memory; and generating a measurement of distance to the object based on the data in the histogram memory.