Exposure control for image sensors
First Claim
Patent Images
1. A method of operating an image sensor, comprising:
- selectively storing, responsive to a first control signal, charge accumulated in a photodiode during a first sub-exposure in a storage node;
selectively discarding, responsive a second control signal, charge accumulated in the photodiode during a first reset period, wherein a first duration of the first sub-exposure is less than a second duration of the first reset period;
selectively storing, responsive to the first control signal, charge accumulated in the photodiode during a second sub-exposure in the storage node; and
transferring, responsive to a third control signal, charge stored in the storage node from the first and second sub-exposures to a floating diffusion node.
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Abstract
A method of operating an image sensor. Charge accumulated in a photodiode during a first sub-exposure may be selectively stored in a storage node responsive to a first control signal. Charge accumulated in the photodiode during a first reset period may be selectively discarded responsive to a second control signal. Charge accumulated in the photodiode during a second sub-exposure may be selectively stored responsive to the first control signal. Charge stored in the storage node from the first and second sub-exposures may be transferred to a floating diffusion node responsive to a third control signal.
141 Citations
39 Claims
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1. A method of operating an image sensor, comprising:
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selectively storing, responsive to a first control signal, charge accumulated in a photodiode during a first sub-exposure in a storage node; selectively discarding, responsive a second control signal, charge accumulated in the photodiode during a first reset period, wherein a first duration of the first sub-exposure is less than a second duration of the first reset period; selectively storing, responsive to the first control signal, charge accumulated in the photodiode during a second sub-exposure in the storage node; and transferring, responsive to a third control signal, charge stored in the storage node from the first and second sub-exposures to a floating diffusion node. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An image sensor pixel, comprising:
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a photodiode; a storage node; a storage gate coupled between the photodiode and storage node, the storage gate selectively receiving an exposure control signal and being responsive thereto; a floating diffusion node; an anti-blooming gate coupled to the photodiode, the anti-blooming gate selectively receiving an anti-blooming control signal and being responsive thereto; a transfer gate coupled between the storage node and floating diffusion node, the transfer gate selectively receiving a transfer control signal and being responsive thereto; and control circuitry configured to provide the anti-blooming control signal to the anti-blooming gate such that charge accumulated in the photodiode is discarded, the control circuitry configured to provide the exposure control signal to the storage gate such that the charge accumulated in the photodiode during a plurality of sub-exposures is transferred to the storage node after or during each sub-exposure, the control circuitry further configured to provide the transfer control signal to the transfer gate following the a plurality of sub-exposures such that charge stored in the storage node is transferred to the floating diffusion node, wherein a duration of at least one sub-exposure is less than a duration of at least one charge discard period. - View Dependent Claims (12, 13)
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14. A method of operating an image sensor, comprising:
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selectively accumulating charge in a first photodiode associated with a first color channel during a first period of time responsive to a first exposure control signal; and selectively accumulating charge in a second photodiode associated with a second color channel during a second period of time responsive to a second exposure control signal; wherein charge is drained away from the first photodiode before the first period of time begins but after the second period of time has started, and wherein the first color channel is different than the second color channel and the first period of time is shorter than the second period of time, the first and second periods of time being at least partially contemporaneous with each other. - View Dependent Claims (15, 16, 17, 18)
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19. An image sensor, comprising:
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a first pixel associated with a first color channel and configured to accumulate charge for a first period of time responsive to a first control signal; a second pixel associated with a second color channel and configured to accumulate charge for a second period of time responsive to a second control signal; and a transfer gate configured to drain charge away from the first pixel responsive to an anti-blooming signal, wherein the anti-blooming signal is applied to the transfer gate to drain charge away from the first pixel before the first period of time begins and after the second period of time has started, and wherein the first color channel is different than the second color channel and the first period of time is shorter than the second period of time. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26)
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27. A method of operating an image sensor, comprising:
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selectively accumulating charge in a first photodiode associated with a first color channel during a first plurality of sub-exposures; selectively transferring, responsive to a first control signal, charge accumulated in the first photodiode during each of the first plurality of sub-exposures to a first node; selectively accumulating charge in a second photodiode associated with a second color channel during a second plurality of sub-exposures; selectively transferring, responsive to a second control signal, charge accumulated in the first photodiode during each of the second plurality of sub-exposures to a second node; and selectively discarding, responsive a third control signal, charge accumulated in the first photodiode during a plurality of reset periods, a reset period occurring after each sub-exposure in the first plurality of sub-exposures, wherein a duration of at least one sub-exposure in the first plurality of sub-exposures is less than a duration of at least one reset period in the plurality of reset periods, and wherein the first color channel is different than the second color channel and at least one of the first plurality of sub-exposures is shorter than at least one of the second plurality of sub-exposures, the first and second plurality of exposures being at least partially contemporaneous. - View Dependent Claims (28, 29, 30, 31, 32)
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33. A method of operating an image sensor, comprising:
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partitioning a first exposure of a first pixel associated with a first color channel into a first plurality of sub-exposures, each of the first plurality of sub-exposures having a respective duration; and partitioning a second exposure of a second pixel associated with a second color channel into a second plurality of sub-exposures, each of the second plurality of sub-exposures having a respective duration; discarding charge accumulated in the first pixel in a plurality of reset periods, a reset period occurring after each sub-exposure in the first plurality of sub-exposures, wherein a duration of at least one sub-exposure in the first plurality of sub-exposures is less than a duration of at least one reset period in the plurality of reset periods, and wherein the duration of at least one of the first plurality of sub-exposures is shorter than at least one of the second plurality of sub-exposures. - View Dependent Claims (34, 35, 36, 37, 38, 39)
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Specification