Patent ID: 8547476
Filing Date: 2013-10-01
Classification: H04N

Abstract:
1. An image sensor comprising: an array of pixels comprising a plurality of rows and columns; a plurality of comparison circuits, each comparison circuit receiving a reference signal value and being coupled to a respective column, each comparison circuit comparing a pixel signal value to the reference signal value and having an output that indicates if the pixel signal value is greater than the reference signal value; a first circuit connected to and counting a number of outputs from the comparison circuits that indicate the pixel signal value is greater than the reference signal value, said first circuit outputting the number of outputs; and a logic circuit that receives the number of outputs from the first circuit, wherein during an exposure period said logic circuit compares the number received from the first circuit to a predetermined number of pixels that may have a pixel signal value greater than the reference signal value and, if the number received from the first circuit is greater than the predetermined number of pixels and a current exposure time is less than a maximum exposure time, the logic circuit adjusts automatic exposure control parameters for a remaining portion of the exposure period by setting a readout gain of the image sensor to a minimum gain value and adjusting the reference signal value to a value of a full scale pixel signal.