# US 12,120,435 B2 · Reducing a flicker effect of multiple light sources in an image > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,120,435 B2 - Document ID: US12120435B2 - Status: Granted - Kind: B2 - Application number: 18/062,387 - Filed: 2022-12-06 - Published: 2023-03-30 - Granted: 2024-10-15 - Earliest claimed: 2019-10-11 - Assignees: Google Inc. - Applicants: Google LLC - Inventors: Gang Sun; Jinglun Gao; Ruben Manuel Velarde; Szepo Robert Hung - Web page: https://patentgrep.com/patent/US12120435B2 ## CPC - H04N 23/745: Detection of flicker frequency or suppression of flicker wherein the flicker is caused by illumination, e.g. due to fluorescent tube illumination or pulsed LED illumination - H04N 23/71: Circuitry for evaluating the brightness variation - H04N 23/73: by influencing the exposure time - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract Techniques and apparatuses are described for reducing a flicker effect of multiple light sources in an image captured with an imaging device. A lighting frequency associated with each of the multiple light sources is detected and prioritized relative to a flicker effect upon the image to identify at least a first-prioritized lighting frequency and a second-prioritized lighting frequency. A first exposure-time factorization set is determined for the first-prioritized lighting frequency, and a second exposure-time factorization set is determined for the second-prioritized lighting frequency. An exposure time of the imaging device is adjusted to an exposure time identified in the first exposure-time factorization set that matches, or aligns near-to-matching, an exposure time identified in the second exposure-time factorization set. ## Claims ### Claim 1 A method comprising: detecting a lighting frequency associated with each of at least two of a plurality of light sources; prioritizing the lighting frequency of each of the at least two of the plurality of light sources to identify at least a first-prioritized lighting frequency and a second-prioritized lighting frequency; determining, based on exposure limits of an imaging device, a first exposure-time factorization set for the first-prioritized lighting frequency and a second exposure-time factorization set for the second-prioritized lighting frequency; and directing the imaging device to capture at an adjusted exposure time, the adjusted exposure time being an exposure time in the first exposure-time factorization set that aligns to at least one of a matching or near-to-matching exposure time in the second exposure-time factorization set. ### Claim 2 (depends on 1) The method of claim 1, further comprising: identifying, prior to detecting the lighting frequency associated with each of the at least two of the plurality of light sources, exposure limits of the imaging device. ### Claim 3 (depends on 1) The method of claim 1, wherein the prioritizing of the lighting frequency of each of the at least two of the plurality of light sources is based on a flicker effect upon an image captured with the imaging device. ### Claim 4 (depends on 1) The method of claim 1, further comprising: determining, prior to the determination of the first exposure-time factorization set for the first-prioritized lighting frequency and a second exposure-time factorization set for the second-prioritized lighting frequency, a current exposure time of the imaging device for capturing the image. ### Claim 5 (depends on 1) The method of claim 1, wherein detecting the lighting frequency comprises at least one of counting an occurrence of a brightness change pattern in a known exposure time, using a dedicated light-frequency sensor, leveraging fast Fourier processing, using a temporal filter, or a combination thereof. ### Claim 6 (depends on 1) The method of claim 1, further comprising capturing at the adjust exposure time, the capturing using a rolling-shutter technology. ### Claim 7 (depends on 1) The method of claim 1, wherein prioritizing the lighting frequency is based on metric functions of at least one of a strength of the lighting frequency, a power-cycle function of the lighting frequency, a rolling-shutter effect of the imaging device, a frame rate of capture of the imaging device, or a combination thereof. ### Claim 8 (depends on 1) The method of claim 1, the method further comprising: identifying one or more product specifications associated with the imaging device, the one or more product specifications regarding at least one of image capture functionality, limits, or capabilities of the imaging device, and wherein adjusting the current exposure time of the imaging device comprises adjusting, based on the one or more product specifications, the current exposure time of the imaging device. ### Claim 9 (depends on 8) The method of claim 8, wherein the one or more product specifications comprises frame-rate limits or sensor hardware limits of the imaging device. ### Claim 10 (depends on 1) The method of claim 1, wherein identifying the exposure limits of the imaging device comprises reading the exposure limits from an internal memory of the imaging device. ### Claim 11 (depends on 10) The method of claim 10, the method further comprising: outputting the exposure limits of the imaging device for subsequent reference in determining the first exposure-time factorization set and the second exposure-time factorization set. ### Claim 12 (depends on 1) The method of claim 1, wherein the first exposure-time factorization set and the second exposure-time factorization set are limited by the exposure limits of the imaging device. ### Claim 13 (depends on 1) The method of claim 1, the method further comprising: determining a current gain of the imaging device for capturing the image, wherein the first exposure-time factorization set and the second exposure-time factorization set are determined based on the exposure limits of the imaging device, a current exposure time of the imaging device, and the current gain of the imaging device. ### Claim 14 An imaging device comprising: at least one processor; and computer-readable media comprising instructions that when executed by the at least one processor cause the at least one processor to: detect a lighting frequency associated with each of at least two of a plurality of light sources; prioritize the lighting frequency of each of the at least two of the plurality of light sources to identify at least a first-prioritized lighting frequency and a second-prioritized lighting frequency; determine, based on exposure limits of the imaging device, a first exposure-time factorization set for the first-prioritized lighting frequency and a second exposure-time factorization set the second-prioritized lighting frequency; and adjust a current exposure time of the imaging device to an adjusted exposure time, the adjusted exposure time being an exposure time in the first exposure-time factorization set that aligns to at least one of a matching or near-to-matching exposure time in the second exposure-time factorization set. ### Claim 15 (depends on 14) The imaging device of claim 14, wherein the instructions further cause the at least one processor to: identify, prior to detecting the lighting frequency associated with each of the at least two of the plurality of light sources, exposure limits of the imaging device. ### Claim 16 (depends on 14) The imaging device of claim 14, wherein the prioritization of the light frequency of each of the at least two of the plurality of lights sources is relative to a flicker effect upon an image captured with the imaging device. ### Claim 17 (depends on 14) The imaging device of claim 14, wherein the instructions further cause the at least one processor to: determine, prior to the determination of the first exposure-time factorization set for the first-prioritized lighting frequency and a second exposure-time factorization set for the second-prioritized lighting frequency, the current exposure time of the imaging device for capturing the image. ### Claim 18 (depends on 14) The imaging device of claim 14, wherein the imaging device uses rolling-shutter technology to capture an image. ### Claim 19 (depends on 14) The imaging device of claim 14, the imaging device comprising further instructions that when executed by the processor cause the processor to: identify one or more product specifications associated with the imaging device, the one or more product specifications regarding at least one of image-capture functionality, limits, or capabilities of the imaging device, wherein adjustment of the current exposure time of the imaging device comprises adjustment, based on the one or more product specifications, of the current exposure time of the imaging device. ### Claim 20 (depends on 14) The imaging device of claim 14, wherein the first exposure-time factorization set and the second exposure-time factorization set are limited by the exposure limits of the imaging device. ### Claim 21 (depends on 14) The imaging device of claim 14, wherein the imaging device comprises at least one of a digital camera, a digital video camera, or combination thereof. ### Claim 22 A machine-readable non-transitory storage medium storing instructions that when executed by at least one processor cause the at least one processor to: detect a lighting frequency associated with each of at least two of a plurality of light sources; prioritize the lighting frequency of each of the at least two of the plurality of light sources to identify at least a first-prioritized lighting frequency and a second-prioritized lighting frequency; determine, based on exposure limits of an imaging device, a first exposure-time factorization set for the first-prioritized lighting frequency and a second exposure-time factorization set the second-prioritized lighting frequency; and adjust a current exposure time of the imaging device to an adjusted exposure time, the adjusted exposure time being an exposure time in the first exposure-time factorization set that aligns to at least one of a matching or near-to-matching exposure time in the second exposure-time factorization set. ### Claim 23 (depends on 22) The machine-readable non-transitory storage medium of claim 22, wherein the prioritization of the lighting frequency of each of the at least two of the plurality of lights sources is relative to a flicker effect upon an image captured with the imaging device. ### Claim 24 (depends on 22) The machine-readable non-transitory storage medium of claim 22, the machine-readable non-transitory storage medium further comprising instructions that when executed by the at least one processor cause the at least one processor to: determine, prior to the determination of the first exposure-time factorization set for the first-prioritized lighting frequency and a second exposure-time factorization set for the second-prioritized lighting frequency, the current exposure time of the imaging device for capturing the image. ### Claim 25 (depends on 22) The machine-readable non-transitory storage medium of claim 22, the machine-readable non-transitory storage medium further comprising instructions that when executed by the at least one processor cause the at least one processor to: identify one or more product specifications associated with the imaging device, the one or more product specifications regarding at least one of image capture functionality, limits, or capabilities of the imaging device, and wherein adjustment of the current exposure time of the imaging device comprises adjustment, based on the one or more product specifications, of the current exposure time of the imaging device. ### Claim 26 (depends on 22) The machine-readable non-transitory storage medium of claim 22, the machine-readable non-transitory storage medium further comprising instructions that when executed by the at least one processor cause the at least one processor to: output the exposure limits of the imaging device for subsequent reference in determining the first exposure-time factorization set and the second exposure-time factorization set. ### Claim 27 (depends on 22) The machine-readable non-transitory storage medium of claim 22, wherein the first exposure-time factorization set and the second exposure-time factorization set are limited by the exposure limits of the imaging device. ### Claim 28 (depends on 22) The machine-readable non-transitory storage medium of claim 22, the machine-readable non-transitory storage medium further comprising instructions that when executed by the at least one processor cause the at least one processor to: determine a current gain of the imaging device for capturing the image, and wherein the first exposure-time factorization set and the second exposure-time factorization set are determined based on the exposure limits of the imaging device, the current exposure time of the imaging device, and the current gain of the imaging device.