Photodiode-type pixel for global electronic shutter and reduced lag
First Claim
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1. An active pixel sensor, comprising:
- a photodiode part operating to accumulate a signal indicative of incoming light;
a floating diffusion part, selectively connected to receive said signal from said photodiode;
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; and
at least one flood and spill control part, connected to at least said photodiode and controlling flooding at least said at least one part to provide a known initial condition on said at least one 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.
87 Citations
11 Claims
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1. An active pixel sensor, comprising:
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a photodiode part operating to accumulate a signal indicative of incoming light;
a floating diffusion part, selectively connected to receive said signal from said photodiode;
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; and
at least one flood and spill control part, connected to at least said photodiode and controlling flooding at least said at least one part to provide a known initial condition on said at least one part. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of operating an active pixel sensor comprising:
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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 predetermined level of charge;
accumulating photoconductors in the photodiode;
transferring said photoconductors to the floating diffusion; and
sampling at least two levels from the floating diffusion representing sample and reset levels, to determine an amount of light. - View Dependent Claims (9, 10)
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11. An active pixel sensor, having a plurality of pixels, each pixel comprising:
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a photodiode, located to receive incoming light;
a photodiode precharge transistor, connected between the photodiode, and a source of precharge;
a floating diffusion, which, in operation, is isolated to allow said floating diffusion to accumulate charge;
a transfer gate, coupled between said photodiode and said floating diffusion;
a floating diffusion precharge transistor, selectively controlled to precharge said floating diffusion to a level of a source of precharge; and
an in-pixel buffer, connected as a follower, and having its input node connected to said floating diffusion and its output node connected to an output line.
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Specification