Patent ID: 8027516
Filing Date: 2011-09-27
Classification: H04N

Abstract:
1. An image forming apparatus, comprising: an electrophotographic image forming element configured to move cyclically and to convey toner to a recording sheet; a movable member configured to move cyclically in synchronization with the electrophotographic image forming element and to convey the recording sheet to the electrophotographic image forming element; and a position detector comprising: a scale attached to the movable member and including a plurality of optical marks formed in line at a substantially constant interval, an image sensor configured to capture an image of at least two of the plurality of optical marks and the interval between the at least two optical marks at a time, the image sensor further configured to be larger than the width of two of the plurality of optical marks and the interval between the two optical marks, a signal processor configured to determine a coordinate of an optical mark with respect to a reference position using the data captured by the image sensor, and a position computing unit configured to compute a distance traveled by at least one of the optical marks based on a number of the optical marks that pass the reference position and the coordinate of the at least one optical mark with respect to the reference position and to determine the value of the interval between the at least two optical marks based on the image of the at least two optical marks.