# US 7,612,813 B2 · Auto exposure for digital imagers > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,612,813 B2 - Document ID: US7612813B2 - Status: Granted - Kind: B2 - Application number: 11/346,346 - Filed: 2006-02-03 - Published: 2007-08-09 - Granted: 2009-11-03 - Earliest claimed: 2006-02-03 - Assignees: Aptina Imaging Corporation - Inventors: Kevin Hunter - Web page: https://patentgrep.com/patent/US7612813B2 ## CPC - H04N 23/73: by influencing the exposure time - H04N 23/71: Circuitry for evaluating the brightness variation - H04N 23/84: for processing colour signals - H04N 25/70: SSIS architectures; Circuits associated therewith - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract An apparatus and method for performing automatic exposure control based on current measured luminance of an image and dynamic/modifiable target luminance levels. Exposure adjustments and/or adjustments to the dynamic/modifiable target luminance windows are based on the measured luminance and threshold settings to improve image quality while avoiding oscillations and other problems typically associated with automatic exposure. ## Claims ### Claim 1 A processor implemented method of performing automatic exposure control for an imager, said method comprising the steps of: inputting into the processor a current luminance of an image captured by the imager; comparing in the processor the current luminance to an adjustable target luminance level; measuring a maximum color saturation; determining if the maximum color saturation is greater than a maximum saturation limit; and adjusting via the processor one of an image exposure setting and the target luminance level based on results of the comparing and determining steps, wherein said adjusting step increases the target luminance level if it is determined that the maximum color saturation is not greater than the maximum saturation limit. ### Claim 2 (depends on 1) The method of claim 1, wherein said comparing step comprises determining if the current luminance is less than the target luminance level and said adjusting step comprises increasing the exposure setting if it is determined that the current luminance is less than the target luminance level. ### Claim 3 (depends on 1) The method of claim 1, wherein said comparing step comprises determining if the current luminance is greater than the target luminance level plus a predetermined threshold and said adjusting step comprises decreasing the exposure setting if it is determined that the current luminance is greater than the target luminance level plus the threshold. ### Claim 4 (depends on 1) The method of claim 1, wherein said comparing step further comprises the act of determining if a black alarm condition has occurred and said adjusting step comprises increasing the target luminance level if it is determined that if the black alarm condition has occurred. ### Claim 5 (depends on 1) The method of claim 1, further comprising the acts of: inputting into the processor a new current luminance of the image; comparing in the processor the new current luminance to the adjustable target luminance level; measuring the maximum color saturation; determining if the maximum color saturation is greater than the maximum saturation limit; and adjusting via the processor one of the image exposure setting and the target luminance level. ### Claim 6 (depends on 5) The method of claim 5, wherein said step of comparing the new current luminance to the adjustable target luminance level comprises determining if the new current luminance is greater than the target luminance level and said second adjusting step comprises decreasing the exposure setting if it is determined that the new current luminance is greater than the target luminance level. ### Claim 7 (depends on 5) The method of claim 5, wherein said step of comparing the new current luminance to the adjustable target luminance level comprises determining if the new current luminance is less than the target luminance level minus a predetermined threshold and said second adjusting step comprises increasing the exposure setting if it is determined that the new current luminance is less than the target luminance level minus the threshold. ### Claim 8 (depends on 5) The method of claim 5, wherein said step of comparing the new current luminance to the adjustable target luminance level further comprises determining if the maximum color saturation is less than or equal to a maximum saturation limit and said second adjusting step further comprises the act of decreasing the target luminance level if it is determined that the maximum color saturation is greater than the maximum saturation limit. ### Claim 9 (depends on 5) The method of claim 5, wherein said step of comparing the new current luminance to the adjustable target luminance level further comprises determining if the maximum color saturation is less than or equal to a maximum saturation limit or if a black alarm condition has occurred, and said second adjusting step further comprises the act of decreasing the target luminance level if it is determined that the maximum color saturation is greater than the maximum saturation limit and the black alarm condition has not occurred. ### Claim 10 An imaging device comprising: an array of pixels for capturing an image; image processing circuitry for obtaining current luminance of the image; and an automatic exposure control block connected to said image processing circuit, said automatic exposure control block compares the current luminance to an adjustable target luminance level, measures a maximum color saturation, determines if the maximum color saturation is greater than a maximum saturation limit, and adjusts one of an image exposure setting and the target luminance level based on results of the comparison and maximum color determination, said automatic exposure block increasing the target luminance level if it is determined that the maximum color saturation is not greater than the maximum saturation limit. ### Claim 11 (depends on 10) The device of claim 10, wherein said automatic exposure control block determines if the current luminance is less than the target luminance level and increases the exposure setting if it is determined that the current luminance is less than the target luminance level. ### Claim 12 (depends on 10) The device of claim 10, wherein said automatic exposure control block determines if the current luminance is greater than the target luminance level plus a predetermined threshold and decreases the exposure setting if it is determined that the current luminance is greater than the target luminance level plus the threshold. ### Claim 13 (depends on 10) The device of claim 10, wherein said automatic exposure control block further determines if a black alarm condition has occurred and increases the target luminance level if it is determined that if the black alarm condition has occurred. ### Claim 14 (depends on 10) The device of claim 10, wherein said image processing circuitry obtains a new current luminance of the image, measures the maximum color saturation, determines if the maximum color saturation is greater than the maximum saturation limit, compares the new current luminance to the adjustable target luminance level and adjusts one of the image exposure setting and the target luminance level. ### Claim 15 (depends on 14) The device of claim 14, wherein said automatic exposure control block determines if the new current luminance is greater than the target luminance level and decreases the exposure setting if it is determined that the new current luminance is greater than the target luminance level. ### Claim 16 (depends on 14) The device of claim 14, wherein said automatic exposure control block determines if the new current luminance is less than the target luminance level minus a predetermined threshold and increases the exposure setting if it is determined that the new current luminance is less than the target luminance level minus the threshold. ### Claim 17 (depends on 14) The device of claim 14, wherein said automatic exposure control block determines if the maximum color saturation is less than or equal to a maximum saturation limit and decreases the target luminance level if it is determined that the maximum color saturation is greater than the maximum saturation limit. ### Claim 18 (depends on 14) The device of claim 14, wherein said automatic exposure control block determines if the maximum color saturation is less than or equal to a maximum saturation limit or if a black alarm condition has occurred, and decreases the target luminance level if it is determined that the maximum color saturation is greater than the maximum saturation limit and the black alarm condition has not occurred. ### Claim 19 (depends on 10) The device of claim 10 further comprising registers, said registers storing said exposure setting and target luminance level. ### Claim 20 A system comprising: a processor; and and an imaging device coupled to said processor, said imaging device comprising: an array of pixels for capturing an image, image processing circuitry for obtaining current luminance of the image, and an automatic exposure control block connected to said image processing circuit, said automatic exposure control block compares the current luminance to an adjustable target luminance level, measures a maximum color saturation, determines if the maximum color saturation is greater than a maximum saturation limit, and adjusts one of an image exposure setting and the target luminance level based on results of the comparison and maximum color determination, said automatic exposure block increasing the target luminance level if it is determined that the maximum color saturation is not greater than the maximum saturation limit. ### Claim 21 (depends on 20) The system of claim 20, wherein said automatic exposure control block determines if the current luminance is less than the target luminance level and increases the exposure setting if it is determined that the current luminance is less than the target luminance level. ### Claim 22 (depends on 20) The system of claim 20, wherein said automatic exposure control block determines if the current luminance is greater than the target luminance level plus a predetermined threshold and decreases the exposure setting if it is determined that the current luminance is greater than the target luminance level plus the threshold. ### Claim 23 (depends on 20) The system of claim 20, wherein said automatic exposure control block further determines if a black alarm condition has occurred and increases the target luminance level if it is determined that if the black alarm condition has occurred. ### Claim 24 (depends on 20) The system of claim 20, wherein said image processing circuitry obtains a new current luminance of the image, measures the maximum color saturation, determines if the maximum color saturation is greater than the maximum saturation limit, compares the new current luminance to the adjustable target luminance level and adjusts one of the image exposure setting and the target luminance level. ### Claim 25 (depends on 24) The system of claim 24, wherein said automatic exposure control block determines if the new current luminance is greater than the target luminance level and decreases the exposure setting if it is determined that the new current luminance is greater than the target luminance level. ### Claim 26 (depends on 24) The system of claim 24, wherein said automatic exposure control block determines if the new current luminance is less than the target luminance level minus a predetermined threshold and increases the exposure setting if it is determined that the new current luminance is less than the target luminance level minus the threshold. ### Claim 27 (depends on 24) The system of claim 24, wherein said automatic exposure control block determines if the maximum color saturation is less than or equal to a maximum saturation limit and decreases the target luminance level if it is determined that the maximum color saturation is greater than the maximum saturation limit. ### Claim 28 (depends on 24) The system of claim 24, wherein said automatic exposure control block determines if the maximum color saturation is less than or equal to a maximum saturation limit or if a black alarm condition has occurred, and decreases the target luminance level if it is determined that the maximum color saturation is greater than the maximum saturation limit and the black alarm condition has not occurred. ### Claim 29 (depends on 20) The system of claim 20, wherein said imaging device further comprises registers, said registers storing said exposure setting and target luminance level.