Patent ID: 7633539

Claim:
An image pickup device comprising: sensing elements arranged in a matrix; a digital counter; and an A/D converter provided for each column of said sensing elements, wherein each A/D converter first retains in a memory unit as an initial value an electric signal corresponding to a signal of a corresponding sensing element, which is an analog signal, and said A/D converter then initiates charge or discharge of said memory unit at a rate corresponding to a magnitude of an input fixed signal, measures a time period from either a charge start time or a discharge start time until said electric signal of said memory unit becomes equal to a reference signal, and recognizes said measured time period as a digital value, wherein each A/D converter includes an integrator, a comparator, and a digital memory, wherein an output of said integrator is connected to an input of said comparator, an output of said comparator is connected to a loading trigger terminal of said digital memory, and wherein said digital counter is connected to an input terminal of said digital memory, and output from said digital counter is stored in said digital memory is the digital value.