# US 9,521,351 B1 · Fractional-readout oversampled image sensor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,521,351 B1 - Document ID: US9521351B1 - Status: Granted - Kind: B1 - Application number: 14/995,138 - Filed: 2016-01-13 - Granted: 2016-12-13 - Earliest claimed: 2015-09-21 - Assignees: Rambus Inc. - Applicants: Rambus Inc. - Inventors: Jay Endsley; Thomas Vogelsang; Craig M. Smith; Michael Guidash; Alexander C. Schneider - Web page: https://patentgrep.com/patent/US9521351B1 ## CPC - H04N 25/531: by controlling rolling shutters in CMOS SSIS - H04N 23/741: by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors - H04N 25/58: involving two or more exposures - H04N 25/583: with different integration times - H04N 25/77: Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components - H04N 25/78: Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract Signals representative of total photocharge integrated within respective image-sensor pixels are read out of the pixels after a first exposure interval that constitutes a first fraction of a frame interval. Signals in excess of a threshold level are read out of the pixels after an ensuing second exposure interval that constitutes a second fraction of the frame interval, leaving residual photocharge within the pixels. After a third exposure interval that constitutes a third fraction of the frame interval, signals representative of a combination of at least the residual photocharge and photocharge integrated within the pixels during the third exposure interval are read out of the pixels. ## Claims ### Claim 1 A method of operation within an integrated-circuit image sensor having a pixel array, the method comprising: after a first exposure interval that constitutes a first fraction of a frame interval, reading out of the pixel array first signals representative of total photocharge integrated within respective pixels during the first exposure interval; after a second exposure interval that constitutes a second fraction of the frame interval, reading out of the pixel array second signals representative of photocharge integrated within the pixels in excess of a threshold level, including removing the photocharge in excess of the threshold level from the pixels and leaving residual photocharge within the pixels; and after a third exposure interval that constitutes a third fraction of the frame interval and transpires after the second exposure interval, reading out of the pixel array third signals representative of a combination of at least the residual photocharge and photocharge integrated within the pixels during the third exposure interval. ### Claim 2 (depends on 1) The method of claim 1 wherein the residual photocharge within the pixels after reading out the second signals comprises a level of photocharge up to but not in excess of the threshold level. ### Claim 3 (depends on 1) The method of claim 1 further comprising storing subframe image data corresponding to the second signals and adding thereto subframe image data corresponding to the third signals to yield image data representative of photocharge integrated during at least the second and third exposure intervals. ### Claim 4 (depends on 1) The method of claim 1 further comprising digitizing the second signals to yield first subframe image data, digitizing the third signals to yield second subframe image data and conditionally adding individual digital pixel values within the first subframe image data to individual digital pixel values within the second subframe image data to produce image data representative of photocharge integrated within the pixel array during at least the second and third exposure intervals. ### Claim 5 (depends on 4) The method of claim 4 wherein conditionally adding the individual digital pixel values within the first subframe image data to the individual digital pixel values within the second subframe image data comprises comparing the individual digital pixel values within the second subframe image data to a digital threshold to validate corresponding individual digital pixels within the first subframe image data. ### Claim 6 (depends on 1) The method of claim 1 further comprising generating, from the second signals, subframe image data corresponding to the second exposure interval, including: digitizing a plurality of the second signals to yield respective digital pixel values; comparing each of the digital pixel values against a digital threshold; and setting each of the digital pixel values that does not exceed the digital threshold to a predetermined value. ### Claim 7 (depends on 1) The method of claim 1 wherein a ratio of the third exposure interval to the second exposure interval corresponds to a ratio of a maximum valid level of the second signals to a maximum valid level of the third signals. ### Claim 8 An integrated-circuit image sensor comprising: a pixel array; and readout circuitry to: read out of the pixel array, after a first exposure interval that constitutes a first fraction of a frame interval, first signals representative of total photocharge integrated within respective pixels during the first exposure interval; read out of the pixel array, after a second exposure interval that constitutes a second fraction of the frame interval, second signals representative of photocharge integrated within the pixels in excess of a threshold level, including removing the photocharge in excess of the threshold level from the pixels and leaving residual photocharge within the pixels; and read out of the pixel array, after a third exposure interval that constitutes a third fraction of the frame interval and transpires after the second exposure interval, third signals representative of a combination of at least the residual photocharge and photocharge integrated within the pixels during the third exposure interval. ### Claim 9 (depends on 8) The integrated-circuit image sensor of claim 8 wherein the residual photocharge within the pixels after reading out the second signals comprises a level of photocharge up to but not in excess of the threshold level. ### Claim 10 (depends on 8) The integrated-circuit image sensor of claim 8 further comprising reconstruction circuitry to store subframe image data corresponding to the second signals and add thereto subframe image data corresponding to the third signals to yield image data representative of photocharge integrated during at least the second and third exposure intervals. ### Claim 11 (depends on 8) The integrated-circuit image sensor of claim 8 wherein the readout circuitry further comprises digital logic to digitize the second signals to yield first subframe image data, digitize the third signals to yield second subframe image data and conditionally add individual digital pixel values within the first subframe image data to individual digital pixel values within the second subframe image data to produce image data representative of photocharge integrated within the pixel array during at least the second and third exposure intervals. ### Claim 12 (depends on 11) The integrated-circuit image sensor of claim 11 wherein the digital logic to conditionally add the individual digital pixel values within the first subframe image data to the individual digital pixel values within the second subframe image data comprises logic to compare the individual digital pixel values within the second subframe image data to a digital threshold to validate corresponding individual digital pixels within the first subframe image data. ### Claim 13 (depends on 8) The integrated-circuit image sensor of claim 8 wherein the readout circuitry further comprises digital logic to generate, from the second signals, subframe image data corresponding to the second exposure interval, including logic to: digitize a plurality of the second signals to yield respective digital pixel values; compare each of the digital pixel values against a digital threshold; and set each of the digital pixel values that does not exceed the digital threshold to a predetermined value. ### Claim 14 (depends on 8) The integrated-circuit image sensor of claim 8 wherein a ratio of the third exposure interval to the second exposure interval corresponds to a ratio of a maximum valid level of the second signals to a maximum valid level of the third signals.