Active-pixel image sensors
First Claim
1. A method of operating an image sensor, which image sensor comprises an array of active pixel elements, each column of pixels having an output circuit which comprises a pair of sample capacitors and switching means operable in conjunction with pixel switches to apply pixel voltages to said sample capacitors;
- the method comprising;
(a) operating said switching means to apply a first pixel value to both sample capacitors;
(b) changing the state of the pixel;
(c) operating the switching means to apply a second pixel value to one of the capacitors; and
(d) utilizing the difference of the resulting voltages on the capacitors as the image value for the pixel.
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Accused Products
Abstract
An image sensor has an array of pixels read by column circuits to provide reset and read samples on a pair of sample capacitors. To alleviate the effects of parasitic capacitance in the region of the sample capacitors, a modified timing arrangement is used. Both sample switches are operated simultaneously to pre-charge both sample capacitors with a pixel signal value. One sample switch is operated after reset to apply a reset value to one of the pre-charged sample capacitors.
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Citations
10 Claims
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1. A method of operating an image sensor, which image sensor comprises an array of active pixel elements, each column of pixels having an output circuit which comprises a pair of sample capacitors and switching means operable in conjunction with pixel switches to apply pixel voltages to said sample capacitors;
- the method comprising;
(a) operating said switching means to apply a first pixel value to both sample capacitors;
(b) changing the state of the pixel;
(c) operating the switching means to apply a second pixel value to one of the capacitors; and
(d) utilizing the difference of the resulting voltages on the capacitors as the image value for the pixel. - View Dependent Claims (2, 3, 4, 5, 6)
- the method comprising;
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7. An image sensor comprising an array of active pixel elements, each column of pixels having an output circuit which comprises a pair of sample capacitors and a respective pair of switches connecting the sample capacitors to a column output line;
- the image sensor further comprising timing means arranged to operate said switches in unison to apply a first pixel value to both sample capacitors, to apply a voltage which changes the state of the pixel, and to operate one switch to apply a second pixel value to one of the sample capacitors.
- View Dependent Claims (8, 9, 10)
Specification