# US 2025/0085162 A1 · Single photon avalanche diode based optical sensor and event-based vision sensor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2025/0085162 A1 - Document ID: US20250085162A1 - Status: Published application - Kind: A1 - Application number: 18/885,774 - Filed: 2024-09-16 - Published: 2025-03-13 - Earliest claimed: 2023-09-11 - Assignees: Pixart Imaging Inc. - Applicants: PixArt Imaging Inc. - Inventors: TSO-SHENG TSAI; KUEI-YANG TSENG; YUEH-LIN CHUNG - Web page: https://patentgrep.com/patent/US20250085162A1 ## CPC - G01J 1/44: Electric circuits {(for command of an exposure part G03B7/02)} - G01J 2001/4466: {Avalanche} - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) ## Abstract There is provided an optical sensor including an SPAD pixel array, multiple counters and a processor. The multiple counters count photon events of the SPAD pixel array to output an event-based vision sensor (EVS) frame per EVS period. The processor determines an index state of each pixel of the SPAD pixel array by comparing a counting value of each pixel respectively at a predetermined number of checking points with two predetermined thresholds, and calculates an index change of the index state associated with each pixel between adjacent EVS frames. The processor further changes the EVS period and/or adds a count offset to the counting value of each pixel to improve sensitivity of the event-based vision sensor. ## Claims ### Claim 1 An event-based vision sensor (EVS), comprising: a plurality of single photon avalanche diode (SPAD) pixels; a plurality of counters, each coupled to an SPAD pixel column and configured to count a number of photons received by every SPAD pixel of the SPAD pixel column within every exposure time; and a processor, coupled to the plurality of counters, and configured to determine an index state of each SPAD pixel among the plurality of SPAD pixels according to a number of counted photons in an exposure time, and generate an image frame according to the number of counted photons of the plurality of SPAD pixels in a predetermined number of exposure times. ### Claim 2 (depends on 1) The event-based vision sensor as claimed in claim 1, wherein pixel data of each pixel of the image frame is a summation of the number of counted photons in the predetermined number of exposure times of a corresponding SPAD pixel. ### Claim 3 (depends on 1) The event-based vision sensor as claimed in claim 1, wherein the processor is configured to determine the index state of one SPAD pixel in the exposure time by comparing the number of counted photons associated with said one SPAD pixel respectively at a predetermined number of temporal checkpoints within the exposure time with two thresholds, and determining the index state according to a temporal checkpoint at which the number of counted photons associated with said one SPAD is between the two thresholds. ### Claim 4 (depends on 3) The event-based vision sensor as claimed in claim 3, wherein one of the two thresholds is a saturation count of the counters, and the other one of the two thresholds is the saturation count divided by an exponent between the predetermined number of temporal checkpoints. ### Claim 5 (depends on 3) The event-based vision sensor as claimed in claim 3, wherein the predetermined number of temporal checkpoints has an exponential relationship. ### Claim 6 (depends on 1) The event-based vision sensor as claimed in claim 1, wherein the processor is further configured to calculate an index change of said each SPAD pixel between two exposure times, and the index change is indicated by +1 or −1. ### Claim 7 (depends on 6) The event-based vision sensor as claimed in claim 6, wherein the processor is further configured to indicate the index change of one SPAD pixel by 1 upon the index state of said one SPAD pixel increasing to be larger than or equal to a changing step, indicate the index change of one SPAD pixel by −1 upon the index state of said one SPAD pixel decreasing to be smaller than or equal to the changing step, and indicate no index change of one SPAD pixel by 0 upon the index state of said one SPAD pixel not increasing to be larger than or equal to the changing step nor decreasing to be smaller than or equal the changing step. ### Claim 8 (depends on 6) The event-based vision sensor as claimed in claim 6, wherein the processor is further configured to adjust the exposure time when a number of SPAD pixels having the index change is not within a predetermined percentage range of a total number of the plurality of SPAD pixels. ### Claim 9 (depends on 6) The event-based vision sensor as claimed in claim 6, wherein the processor is further configured to adjust a count offset to the number of counted photons when a number of SPAD pixels having the index change is not within a predetermined percentage range of a total number of the plurality of SPAD pixels. ### Claim 10 An event-based vision sensor (EVS), comprising: a plurality of single photon avalanche diode (SPAD) pixels; a plurality of counters, each coupled to an SPAD pixel column and configured to count a number of photons received by every SPAD pixel of the SPAD pixel column within every exposure time; and a processor, coupled to the plurality of counters, and configured to output an index change of said every SPAD pixel calculated according to counted photons between two exposure times. ### Claim 11 (depends on 10) The event-based vision sensor as claimed in claim 10, wherein the processor is further configured to respectively sum up a number of counted photons in a predetermined number of exposure times of each SPAD pixel of the plurality of SPAD pixels to generate an image frame. ### Claim 12 (depends on 10) The event-based vision sensor as claimed in claim 10, wherein the processor is further configured to determine an index state of one SPAD pixel in one exposure time by comparing a number of counted photons associated with said one SPAD pixel respectively at a predetermined number of temporal checkpoints within the one exposure time with two thresholds, and determining the index state according to a temporal checkpoint at which the number of counted photons associated with said one SPAD is between the two thresholds. ### Claim 13 (depends on 12) The event-based vision sensor as claimed in claim 12, wherein one of the two thresholds is a saturation count of the counters, and the other one of the two thresholds is the saturation count divided by an exponent between the predetermined number of temporal checkpoints. ### Claim 14 (depends on 12) The event-based vision sensor as claimed in claim 12, wherein the predetermined number of temporal checkpoints has an exponential relationship. ### Claim 15 (depends on 12) The event-based vision sensor as claimed in claim 12, wherein the index change is indicated by +1 or −1. ### Claim 16 (depends on 15) The event-based vision sensor as claimed in claim 15, wherein the processor is further configured to indicate the index change of one SPAD pixel by 1 upon the index state of said one SPAD pixel increasing to be larger than or equal to a changing step, indicate the index change of one SPAD pixel by −1 upon the index state of said one SPAD pixel decreasing to be smaller than or equal to the changing step, and indicate no index change of one SPAD pixel by 0 upon the index state of said one SPAD pixel not increasing to be larger than or equal to the changing step nor decreasing to be smaller than or equal the changing step. ### Claim 17 (depends on 10) The event-based vision sensor as claimed in claim 10, wherein the processor is further configured to adjust the exposure time when a number of SPAD pixels having the index change is not within a predetermined percentage range of a total number of the plurality of SPAD pixels. ### Claim 18 (depends on 10) The event-based vision sensor as claimed in claim 10, wherein the processor is further configured to adjust a count offset to the number of photons when a number of SPAD pixels having the index change is not within a predetermined percentage range of a total number of the plurality of SPAD pixels. ### Claim 19 An optical sensor, comprising: a plurality of single photon avalanche diode (SPAD) pixels; a plurality of counters, each coupled to an SPAD pixel column and configured to count a number of photons received by every SPAD pixel of the SPAD pixel column within every exposure time; and a processor, coupled to the plurality of counters, and configured to output an index change of each SPAD pixel among the plurality of SPAD pixels to indicate an illumination change detected by said each SPAD pixel between two exposure times, and output an image frame according to the number of photons of the plurality of SPAD pixels counted within a predetermined number of exposure times. ### Claim 20 (depends on 19) The optical sensor as claimed in claim 19, wherein the index change is indicated by +1 or −1.