Patent ID: 6688449
Filing Date: 2004-02-10
Classification: G07D

Abstract:
An image pickup device comprising an area sensor composed of a two-dimensional matrix of photoelectric pixels, wherein:each of the photoelectric pixels has a photoelectric converter for forming an optical image, a signal comparator for comparing a charge representative signal from the photoelectric converter with a reference signal and providing a resultant signal, and a signal holder for holding the resultant signal; the photoelectric pixels are connected to address lines, respectively; the photoelectric pixels are arranged in a two-dimensional matrix over a path along which disk objects are moved at a constant speed; whenever a disk object moving along the path comes to the area sensor a position on the area sensor is estimated according to a moving speed of the disk object, a position of a first one of the photoelectric pixels that first provides an image of an outermost circumferential edge of the disk object, and a radius of an outermost circumferential edge of a reference disk stored in advance, the estimated position on the area sensor being on a line extended from the first photoelectric pixel along the path and being expected to meet the center of the disk object; at least one concentric circle is defined around the estimated position on the area sensor and address lines corresponding to the defined concentric circle are determined; when the center of the disk object meets the estimated position on the area sensor while the disk object continuously moving along the path, signals from the photoelectric pixels passed through the signal comparators are stored in the signal holders; and the signals stored in the signal holders are read to a data line only from the signal holders of the photoelectric pixels that are specified by addressing signals passed through the determined address lines corresponding to the defined concentric circle.