Photodiode-type pixel for global electronic shutter and reduced lag
First Claim
Patent Images
1. An active pixel sensor, comprising:
- a photodiode part located at least partially in a substrate and constructed to accumulate a signal indicative of incoming light during an integration period;
a floating diffusion part located at a first side of said photodiode part, selectively connected to receive said signal from said photodiode part;
a transfer barrier gate, having a bias level which allows said signal to pass from said photodiode part to said floating diffusion part;
a buffer, connected to sample a signal on said floating diffusion part;
a storage region located at a second side of said photodiode part in said substrate for receiving excess charge from said photodiode part at an end of said integration period; and
at least one flood and spill control part, connected to at least said photodiode part and controlling flooding of at least said photodiode part to provide a known initial condition on said photodiode part.
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Abstract
Operation for global electronic shutter photodiode-type pixels. In a first mode of operation, lag is reduced through global reset of the photodiode array and fixed pattern noise is eliminated through comparison of the photosignal level and the reset level of the floating drain. In a second mode of operation, simultaneous integration and readout processes are achieved through cessation of spill charges over the transfer gate. In a third mode of operation, regulation of the reset photodiode and transfer gate enables voltage gain between the photodiode and the sense node.
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Citations
20 Claims
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1. An active pixel sensor, comprising:
- a photodiode part located at least partially in a substrate and constructed to accumulate a signal indicative of incoming light during an integration period;
a floating diffusion part located at a first side of said photodiode part, selectively connected to receive said signal from said photodiode part;
a transfer barrier gate, having a bias level which allows said signal to pass from said photodiode part to said floating diffusion part;
a buffer, connected to sample a signal on said floating diffusion part;
a storage region located at a second side of said photodiode part in said substrate for receiving excess charge from said photodiode part at an end of said integration period; and
at least one flood and spill control part, connected to at least said photodiode part and controlling flooding of at least said photodiode part to provide a known initial condition on said photodiode part. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- a photodiode part located at least partially in a substrate and constructed to accumulate a signal indicative of incoming light during an integration period;
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8. A method of operating an active pixel sensor comprising:
- flooding at least one photosensitive part which at least includes a photodiode with excess charge;
allowing said at least one part to spill to a first drain region on a first side of said photodiode so that said photodiode has a predetermined level of charge to begin an integration period;
accumulating photoconductors in the photodiode;
transferring said photoconductors to a floating diffusion region;
draining excess charge into a second drain region at a second side of said photodiode; and
sampling at least two levels from the floating diffusion representing sample and reset levels, to determine an amount of light incident on the photodiode. - View Dependent Claims (9, 10, 11, 12, 13, 14)
- flooding at least one photosensitive part which at least includes a photodiode with excess charge;
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15. An active pixel sensor, having a plurality of pixels each comprising:
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a photodiode, constructed in a substrate to receive incoming light and generate charge; first and second charge storage regions located in the substrate at respective first and second sides of said photodiode; a reset transistor for setting a charge level at said photodiode and said first charge storage region to a predetermined level; a first transfer transistor gate located between the photodiode and the first charge storage region and adapted to receive a first bias level for allowing charge to transfer from said photodiode to said first charge storage region; and a second transfer transistor gate located between the photodiode and the second charge storage region and adapted to receive a second bias level for allowing charge to transfer from said photodiode to said second charge storage region, wherein the second bias creates a lower potential barrier between the photodiode and the second charge storage region than exists between the photodiode and the first charge storage region. - View Dependent Claims (16)
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17. A method of operating an active pixel device, comprising:
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causing a plurality of photodiode regions to reach an initial predetermined level of charge by; applying light to said photodiode regions to generate charge; and lowering a potential barrier to a first level between said photodiode regions and respective first drain regions to cause a predetermined amount of charge to drain into the first drain regions; integrating charge at the photodiode regions during an integration period; transferring charge from the photodiode regions to respective floating diffusion regions; ending said integration period by lowering a second potential barrier, to a level less than said first level, between said photodiode regions and respective second drain regions; and reading out a plurality of signals representing amounts of charge transferred respectively to said floating diffusion regions. - View Dependent Claims (18, 19, 20)
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Specification