Active-pixel image sensors
AssigneeSTMicroelectronics S.r.l.
InventorsRobert Henderson, Jonathan Ephriam David Hurwitz
Life of this patent
Estimating the term…
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.
Claims17
A method of operating an image sensor comprising an array of active pixel elements, each column of pixels having an output circuit including a pair of sample capacitors and associated switches for applying pixel voltages to the sample capacitors, the method comprising:
- operating the switches to apply a readout value to both sample capacitors;
- applying a reset voltage for changing a state of the pixel;
- operating the switches to apply a reset value to one of the capacitors;
- and
- utilizing a difference of resulting voltages on the capacitors as the image value for the pixel.
A method of operating an image sensor comprising an array of active pixels and output circuits each including a pair of sample capacitors, the method comprising:
- applying a readout value to both sample capacitors;
- applying a reset voltage for changing a state of the pixel;
- applying a reset value to one of the capacitors;
- and
- generating an image value for the pixel by differencing resulting voltages on the sample capacitors.
An image sensor comprising:
- an array of active three transistor pixels, each column of three transistor pixels including a column output line and an output circuit comprising a pair of sample capacitors and a respective pair of switches connecting the sample capacitors to the column output line;
- and
- timing means for operating the switches to apply a readout value to both sample capacitors, to apply a reset voltage which changes the state of the three transistor pixel, and to operate one of the switches to apply a reset value to one of the sample capacitors.
An image sensor comprising:
- an array of active three transistor pixels, each column of three transistor pixels including a column output line and an output circuit comprising a pair of sample capacitors selectively connected to the column output line;
- and
- a timing circuit to apply a readout value to both sample capacitors, to apply a reset voltage which changes the state of the three transistor pixel, and to apply a reset value to one of the sample capacitors.
A method of operating an image sensor comprising an array of pixels and output circuits each including a pair of sample capacitors, the method comprising:
- applying a reset value to both sample capacitors;
- changing a state of the pixel by at least applying a transfer gate voltage to the pixel;
- applying a readout value to one of the capacitors, and
- generating an image value for the pixel by differencing resulting voltages on the sample capacitors.
An image sensor comprising:
- an array of four transistor pinned photodiode pixels having a transfer gate, each column of four transistor pinned photodiode pixels including a column output line and an output circuit comprising a pair of sample capacitors selectively connected to the column output line;
- and
- a timing circuit to apply a reset value to both sample capacitors, to apply a transfer voltage to the transfer gate which changes a state of the four transistor pinned photodiode pixel, and to apply a readout value to one of the sample capacitors.
Dependencies are inferred from the claim text.