Patent ID: 8345077

Claim:
A write device comprising: an opening that is arranged on a casing that houses a light source that emits irradiation light to expose a photoreceptor, the opening allowing passage of the irradiation light; a shutter unit that is movably mounted on the casing and is moved to open and close the opening; a rotator that moves the shutter unit in accordance with rotation; a drive unit that rotates the rotator; a plurality of wall-like sections, each wall-like section having a different width and being arranged in a standing manner on a side intersecting with a rotary shaft of the rotator; a detecting unit that detects each of the wall-like sections that are moved in accordance with the rotation of the rotator; a measuring unit that measures a detection time period from when a wall-like section of the plurality of wall-like sections is detected until when the wall-like section is no longer detected; a position detecting unit that determines which one of the wall-like sections is the detected wall-like section by using the measured detection time period and the width of each of the wall-like sections and detects a position of the shutter unit on the casing by using the determined wall-like section; and an exposure control unit that controls exposure in accordance with the position of the shutter unit.