Method and circuit for performing correlated double sub-sampling (CDSS) of pixels in an active pixel sensor (APS) array
First Claim
1. An image sensor comprising a plurality of pixels arranged in rows and columns, each column of pixels being switchably connected to at least two reset charge storage capacitors for storing at least two reset charges and to at least two image signal charge storage capacitors for storing at least two image signal charges, wherein at least one of the at least two reset charge storage capacitors in each column is configured to be connected at a node in series to at least one of the at least two image signal charge storage capacitors in the same column,wherein at least two reset charge storage capacitors are switchably connected to each other to generate an averaged reset charge for at least two pixels in the same column.
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Abstract
A method and circuit for performing Correlated Double Sub-Sampling (CDSS) of pixels in an active pixel sensor (APS) array. The method and the apparatus subsamples a plurality (L2) of pixels by: storing L2 analog reset charges output from the L2 pixels into a first set of (N2) storage capacitors, and combining the (L2) reset charges; storing L2 analog image signal charges output from the L2 pixels into a second set of (N2) storage capacitors, and combining the (L2) image charges; and then obtaining a differential voltage (VS-VR) by subtracting (in the analog-domain) the voltage (VR) represented by the combined (L2) reset charges from the voltage (VS) represented by the combined (L2) image signal charges. When L equals one, the circuit performs conventional Correlated Double Sampling CDS upon the one pixel.
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Citations
46 Claims
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1. An image sensor comprising a plurality of pixels arranged in rows and columns, each column of pixels being switchably connected to at least two reset charge storage capacitors for storing at least two reset charges and to at least two image signal charge storage capacitors for storing at least two image signal charges, wherein at least one of the at least two reset charge storage capacitors in each column is configured to be connected at a node in series to at least one of the at least two image signal charge storage capacitors in the same column,
wherein at least two reset charge storage capacitors are switchably connected to each other to generate an averaged reset charge for at least two pixels in the same column.
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15. A method of subsampling N2 pixels in an active pixel sensor (APS) array, the method comprising:
- sequentially storing into N reset charge storage capacitors N pixel reset charges received from N pixels in the same first column of the APS array, wherein the N reset charge storage capacitors are switchably connected to each other in parallel between a first node and a second node; and
closing no more than N−
1 reset charge-holding switches connected to the N reset charge storage capacitors between the first node and the second node; andclosing a row-direction averaging switch disposed between the first node and a second set of N reset charge storage capacitors N corresponding to a second column of the APS array, wherein the N reset charge storage capacitors are connected to each other in parallel when the N−
1 reset charge-holding switches are closed, such that an averaged reset charge for N pixels in the first column in generated. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
- sequentially storing into N reset charge storage capacitors N pixel reset charges received from N pixels in the same first column of the APS array, wherein the N reset charge storage capacitors are switchably connected to each other in parallel between a first node and a second node; and
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30. An image sensor comprising:
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an array of pixels arranged in a plurality of rows and a plurality of columns, every pixel in each column of pixels is operatively connected to an averaging unit, wherein each averaging unit includes a first and second storage capacitors for storing reset charges from a first pixel and from a second pixel, and further includes third and fourth storage capacitors for storing analog image signal charges from the first pixel and from the second pixel, wherein at least one of the at least two reset charge storage capacitors in each column is configured to be connected at a node in series to at least one of the at least two image signal charge storage capacitors in the same column, wherein the first and second storage capacitors are switchably connected to each other to generate an averaged reset charge for the first and second pixels in the same column. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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41. A method of subsampling N2 pixels in an array of pixels arranged in a plurality of rows and a plurality of columns, each pixel being adapted to output a reset voltage and an image signal voltage, the method comprising the steps of:
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storing the plurality of reset voltages output from the N2 pixels into a first set of storage capacitors and combining the plurality of reset voltages stored in the first set of storage capacitors; storing a plurality of image signal voltages output from the plurality of N2 pixels into a second set of storage capacitors and combining the plurality of image signal voltages stored in the second set of storage capacitors; and connecting at least one storage capacitor among the first set of storage capacitors in-series with at least one storage capacitor among the second set of storage capacitors, wherein the storage capacitors in the first set are switchably connected to each other to generate an averaged reset charge for the plurality of pixels in the same column. - View Dependent Claims (42, 43, 44)
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45. A method of subsampling N2 pixels arrayed in N columns and N rows of an active pixel sensor (APS) array, each pixel being adapted to output a reset voltage and an image signal voltage, the method comprising the steps of:
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storing the reset voltage of the first pixel in the first row as a first charge in a first capacitor and storing the reset voltage of the second pixel in the first row as a second charge in a second capacitor; and
then immediately combining the first and second charges into a first row-averaged reset charge; and
afterwardsstoring the reset voltage of the first pixel in the second row as a fifth charge in a fifth capacitor and storing the reset voltage of the second pixel in the second row as a sixth charge in a sixth capacitor; and
then immediately combining the fifth and sixth charges into a second row-averaged reset charge; andcombining the first row-averaged reset charge and the second row-averaged reset charge into a subsampled reset charge, wherein the first and fifth capacitors are switchably connected to each other to generate an averaged reset charge for the pixels of the first and second rows in the same column. - View Dependent Claims (46)
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Specification