Patent ID: 8089541

Claim:
A solid-state image-pickup device characterized by 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; row scanning means for selectively controlling the respective unit pixels of the pixel-array section on a row-by-row basis; and analog-to-digital conversion means for converting, 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 means via a corresponding one of the column signal lines, wherein the analog-to-digital conversion means includes first comparison means for comparing the analog signal with any one of a plurality of first reference voltages having slopes with the same gradient, second comparison means for comparing, with the one of the plurality of first reference voltages that is used by the first comparison means, 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 counting means for performing a counting operation using a counting amount according to comparison results of the first and second comparison means, and for providing a counter value that is obtained by the counting operation as the digital signal.