Patent ID: 8687097

Claim:
A solid-state image-pickup device comprising: a pixel-array section in which unit pixels including photoelectric conversion elements are two-dimensionally disposed in a matrix form, and in which each of column signal lines is disposed in a corresponding one of columns for a disposition of the unit pixels in the matrix form; a row scanning unit configured to selectively control the respective unit pixels of the pixel-array section on a row-by-row basis; and an analog-to-digital conversion unit configured to convert, to a digital signal, an analog signal that is output from a corresponding one of the unit pixels of a row which is selectively controlled by the row scanning unit via a corresponding one of the column signal lines, wherein, the analog-to-digital conversion unit includes (a) a first comparison unit configured to compare the analog signal with any one of a plurality of first reference voltages having slopes with the same gradient, (b) a second comparison unit configured to compare, with the one of the plurality of first reference voltages that is used by the first comparison unit, a second reference voltage having a slope with a gradient that is different from the gradient of the slopes of the first reference voltages, and (c) a counting unit configured to perform a counting operation using a counting amount according to comparison results of the first and second comparison units, and for providing a counter value that is obtained by the counting operation as the digital signal.