Patent ID: 8400557

Claim:
An apparatus for detecting an in-focus state, comprising: a plurality of line sensors arranged on a projection area of an optical image-forming system; and an image signal output processor that outputs image signals of an object on the basis of electric charges accumulated in the plurality of line sensors, each line sensor comprising a plurality of pairs of photoelectric converters arrayed along a longitudinal direction of the line sensor and a plurality of image-pixel signal-reading circuits, each image-pixel signal-reading circuit reading electric charges from a corresponding pair of photoelectric converters, each image-pixel signal-reading circuit comprising a first circuit that reads electric charges accumulated in one photoelectric converter of the pair of photoelectric converters and a second circuit that reads electric charges accumulated in the other photoelectric converter of the pair of photoelectric converters, each image-pixel signal-reading circuit being positioned between the corresponding pair of photoelectric converters, each of the first and second circuits including a common circuit portion that is shared by both said first and second circuits.