Multiple conversion gain image sensor
An image sensor including an array of pixels, each having: a storage node coupled to a capacitive sense node by a transfer transistor; and a connection transistor coupling the pixel sense node to an intermediate node of the pixel, wherein each pixel has its intermediate node coupled to a node of application of a reset voltage by a reset transistor, and different pixels have their respective intermediate nodes interconnected by a conductive connection track.
1. An image sensor comprising:
an array of pixels, each pixel having:
a storage node;
a capacitive sense node
a transfer transistor coupling the storage node to the capacitive sense node;
an intermediate node;
a reset voltage node configured to receive a reset voltage; and
a connection transistor coupling the sense node to the intermediate node of the pixel;
a first conductive connection track coupling the intermediate nodes of first and second pixels of the array to each other; and
a control circuit configured to cause the connection transistor of the first pixel to electrically couple the capacitive sense node of the first pixel to the intermediate node of the second pixel via the first conductive connection track during a voltage conversion phase in which the transfer transistor of the first pixel converts photogenerated charges from the storage node of the first pixel to a voltage on the capacitive sense node of the first pixel.
2. The sensor of claim 1 , wherein each pixel further comprises a source follower transistor connected as a source follower, having a gate coupled to the sense node of the pixel.
3. The sensor of claim 2 , wherein each pixel further comprises an output transistor coupling a source of the source follower transistor of the pixel to an output line.
4. The sensor of claim 1 , wherein the pixels of the array are distributed into at least first and second groups of pixels, the first and second pixels being part of the first group of pixels, the sensor comprising:
a second conductive connection track coupling the respective intermediate nodes of the pixels of the second group to each other, the first and second conductive connection tracks being unconnected to one another.
5. The sensor of claim 4 , wherein the pixels of the first group are located on a same column of the array.
6. The sensor of claim 4 , wherein the pixels of the first group are juxtaposed two by two in the array.
7. The sensor of claim 4 , further comprising a track connection transistor coupling the first and second connection tracks to each other.
8. The sensor of claim 1 , wherein each pixel comprises a photodiode having a cathode connected to the storage node of the pixel.
9. The sensor of claim 1 , wherein each pixel comprises a reset transistor coupled between a reset voltage terminal and the intermediate node of the pixel.
10. The sensor of claim 9 , wherein the reset transistor of the second pixel is coupled with the first conductive connection track between the intermediate nodes of the first and second pixels.
11. A method, comprising:
capturing an image using the sensor of claim 1 , the capturing including reading the first pixel of the sensor during a reading cycle of the first pixel, and
electrically coupling the capacitive sense node of the first pixel to the capacitive sense node of the second pixel during the reading cycle of the first pixel.
12. The method of claim 11 , wherein each pixel further comprises a source follower transistor connected as a source follower, having a gate coupled to the sense node of the pixel, the source follower transistor of the first pixel outputting a voltage corresponding to the photogenerated charges from the storage node of the first pixel.
13. The method of claim 12 , wherein each pixel further comprises an output transistor that outputs to an output line and output voltage corresponding to the voltage output by the source follower transistor.
14. An image sensor comprising:
an array of pixels, each pixel having:
a storage node;
a capacitive sense node
a transfer transistor coupling the storage node to the capacitive sense node;
an intermediate node;
a reset voltage node configured to receive a reset voltage; and
a connection transistor coupling the sense node to the intermediate node of the pixel; and
means for electrically coupling the capacitive sense node of the first pixel to the intermediate node of the second pixel during a voltage conversion phase in which the transfer transistor of the first pixel converts photogenerated charges from the storage node of the first pixel to a voltage on the capacitive sense node of the first pixel.
15. The sensor of claim 14 , wherein each pixel further comprises:
a source follower transistor connected as a source follower, having a gate coupled to the sense node of the pixel; and
an output transistor coupling a source of the source follower transistor of the pixel to an output line.
16. The sensor of claim 14 , wherein the pixels of the array are distributed into at least first and second groups of pixels, the first and second pixels being part of the first group of pixels, the sensor comprising:
means for coupling the respective intermediate nodes of the pixels of the second group to each other.
17. The sensor of claim 14 , wherein each pixel comprises a photodiode having a cathode connected to the storage node of the pixel.
18. The sensor of claim 14 , wherein each pixel comprises a reset transistor coupled between a reset voltage terminal and the intermediate node of the pixel.
19. The sensor of claim 18 , wherein the reset transistor of the second pixel is part of the means for electrically coupling the capacitive sense node of the first pixel to the intermediate node of the second pixel.