Patent attributes
A pixel circuit, and a method for operating a pixel circuit, to provide a multiple knee response characteristic. In one embodiment of the invention, one or more feed-through pulse (FTP) signals are transmitted to an integration node to end a first linear integration time period. The FTP signal allows electrons to drain from the integration node to a reset node through a transfer gate. After the first integration period, a second linear integration period is conducted on the pixel circuit, where the photo conversion gain of the pixel circuit becomes reduced under higher illumination conditions due to the drained node. Such operation creates a pixel with a photo response having multiple “knee” points, where each “knee” in the photo response curve will create separate regions whose photo sensitivities can be independently controlled with minimal thermal interference. By setting different voltage levels for the FTP signal and by controlling the integration time periods, the photo-response of the pixel circuit can be easily controlled.
