Feedthrough-compensated image sensor

Patent metadata

Field	Value
Publication number	US-9264639-B2
Application number	US-201514616546-A
Country	US
Kind code	B2
Filing date	Feb 6, 2015
Priority date	Feb 7, 2014
Publication date	Feb 16, 2016
Grant date	Feb 16, 2016

Abstract

A control pulse is generated a first control signal line coupled to a transfer gate of a pixel to enable photocharge accumulated within a photosensitive element of the pixel to be transferred to a floating diffusion node, the first control signal line having a capacitive coupling to the floating diffusion node. A feedthrough compensation pulse is generated on a second signal line of the pixel array that also has a capacitive coupling to the floating diffusion node. The feedthrough compensation pulse is generated with a pulse polarity opposite the pulse polarity of the control pulse and is timed to coincide with the control pulse such that capacitive feedthrough of the control pulse to the floating diffusion node is reduced.

First claim

What is claimed is:

1. A method of operation within an integrated-circuit image sensor having a pixel array, the method comprising:
generating, on a first signal line of the pixel array that is connected to a transfer gate of a first pixel within the pixel array, a control pulse that enables photocharge accumulated within a photosensitive element of the first pixel to be transferred to a floating diffusion node, the first signal line having a capacitive coupling to the floating diffusion node;
generating, on a second signal line of the pixel array that also has a capacitive coupling to the floating diffusion node, a first feedthrough compensation pulse having a pulse polarity opposite a pulse polarity of the control pulse and that is timed to coincide with the control pulse such that capacitive feedthrough of the control pulse to the floating diffusion node is reduced; and
wherein the pixel array comprises a first pixel row constituted by a first plurality of pixels, including the first pixel, connected to the first signal line, and a second pixel row constituted by a second plurality of pixels connected to the second signal line, and wherein the second signal line is coupled to a respective transfer gate within each pixel of the second plurality of pixels.

2. A method of operation within an integrated-circuit image sensor having a pixel array, the method comprising:
generating, on a first signal line of the pixel array that is connected to a transfer gate of a first pixel within the pixel array, a control pulse that enables photocharge accumulated within a photosensitive element of the first pixel to be transferred to a floating diffusion node, the first signal line having a capacitive coupling to the floating diffusion node;
generating, on a second signal line of the pixel array that also has a capacitive coupling to the floating diffusion node, a first feedthrough compensation pulse having a pulse polarity opposite a pulse polarity of the control pulse and that is timed to coincide with the control pulse such that capacitive feedthrough of the control pulse to the floating diffusion node is reduced; and
wherein the pixel array comprises a first pixel row constituted by a first plurality of pixels, including the first pixel, connected to the first signal line, and a second pixel row constituted by a second plurality of pixels connected to the second signal line, and wherein the second signal line is coupled to a respective reset transistor within each pixel of the second plurality of pixels.

3. A method of operation within an integrated-circuit image sensor having a pixel array, the method comprising:
generating, on a first signal line of the pixel array that is connected to a transfer gate of a first pixel within the pixel array, a control pulse that enables photocharge accumulated within a photosensitive element of the first pixel to be transferred to a floating diffusion node, the first signal line having a capacitive coupling to the floating diffusion node;
generating, on a second signal line of the pixel array that also has a capacitive coupling to the floating diffusion node, a first feedthrough compensation pulse having a pulse polarity opposite a pulse polarity of the control pulse and that is timed to coincide with the control pulse such that capacitive feedthrough of the control pulse to the floating diffusion node is reduced; and
wherein the first pixel comprises a row-select transistor to switchably couple the first pixel to an output line of the pixel array such that a signal corresponding to a charge level of the floating diffusion node is generated on the output line, and wherein the second signal line is coupled to the row-select transistor.

4. The method of claim 3 further comprising raising the second signal line to a first predetermined voltage level to switch the row-select transistor from a non-conducting state to a conducting state, and wherein generating the first feedthrough compensation pulse having a polarity opposite the polarity of the control pulse comprises lowering the second signal line from the first predetermined voltage level to a second predetermined voltage level and then restoring the second signal line to the first predetermined voltage level, the second predetermined voltage level being sufficiently high to maintain the row-select transistor in the conducting state.

5. A method of operation within an integrated-circuit image sensor having a pixel array, the method comprising:
generating, on a first signal line of the pixel array that is connected to a transfer gate of a first pixel within the pixel array, a control pulse that enables photocharge accumulated within a photosensitive element of the first pixel to be transferred to a floating diffusion node, the first signal line having a capacitive coupling to the floating diffusion node;
generating, on a second signal line of the pixel array that also has a capacitive coupling to the floating diffusion node, a first feedthrough compensation pulse having a pulse polarity opposite a pulse polarity of the control pulse and that is timed to coincide with the control pulse such that capacitive feedthrough of the control pulse to the floating diffusion node is reduced; and
generating, on a third signal line of the pixel array that also has a capacitive coupling to the floating diffusion node, a second feedthrough compensation pulse having a pulse polarity opposite the pulse polarity of the control pulse and that is timed to coincide with the first feedthrough compensation pulse such that the first and second feedthrough compensation pulses act jointly to reduce capacitive feedthrough of the control pulse to the floating diffusion node.

6. A method of operation within an integrated-circuit image sensor having a pixel array, the method comprising:
generating, on a first signal line of the pixel array that is connected to a transfer gate of a first pixel within the pixel array, a control pulse that enables photocharge accumulated within a photosensitive element of the first pixel to be transferred to a floating diffusion node, the first signal line having a capacitive coupling to the floating diffusion node;
generating, on a second signal line of the pixel array that also has a capacitive coupling to the floating diffusion node, a first feedthrough compensation pulse having a pulse polarity opposite a pulse polarity of the control pulse and that is timed to coincide with the control pulse such that capacitive feedthrough of the control pulse to the floating diffusion node is reduced; and
generating one or more other feedthrough compensation pulses on one or more other signal lines of the pixel array, respectively, each of the one or more other feedthrough compensation pulses having a pulse polarity opposite the pulse polarity of the control pulse and being timed to coincide with the first feedthrough compensation pulse such that (i) the first feedthrough compensation pulse and the one or more other feedthrough compensation pulses act in combination to reduce capacitive feedthrough of the control pulse to the floating diffusion node, and (ii) amplitudes of each of the first and one or more other feedthrough compensation pulses are substantially uniform, wherein the amplitudes of each of the first and one or more other feedthrough compensation pulses is less than an amplitude required to eliminate feedthrough compensation from the control pulse to the floating diffusion in absence of the one or more other feedthrough compensation pulses.

7. An integrated-circuit image sensor comprising:
a first pixel having a photosensitive element, floating diffusion node and transfer gate disposed between the photosensitive element and floating diffusion node;
a first signal line connected to the transfer gate an

Assignees

• Rambus Inc

Inventors

• Guidash Michael
• Endsley Jay
• Ladd John
• Vogelsang Thomas
• Smith Craig M

Classifications

• H04N25/583 Primary

  with different integration times · CPC title

• H04N25/617 Primary

  for reducing electromagnetic interference, e.g. clocking noise · CPC title

• H04N25/76 Primary

  Addressed sensors, e.g. MOS or CMOS sensors · CPC title

• H04N25/78

  Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters · CPC title

• H04N25/671

  for non-uniformity detection or correction · CPC title