Patent ID: 7957008

Claim:
An optical-type rotational body position detection apparatus comprising: a light emitting unit which is configured to emit light; a light detecting unit which is configured to detect light; a fixing support member which supports the light emitting unit and the light detecting unit such that the light emitting unit and the light detecting unit are mutually opposed to and spaced apart from each other, and that light from the light emitting unit is detected by the light detecting unit; a rotational body which rotates in a predetermined angle at each of predetermined time intervals to cross an optical axis connecting the light emitting unit and the light detecting unit, which includes a standard position light transmission hole disposed on a rotational locus crossing the optical axis, and which is configured such that after the rotational body takes one rotational movement over the predetermined angle within the predetermined time interval from a standard position at which a center of the standard position light transmission hole coincides with the optical axis, a peripheral edge of the standard position light transmission hole is positioned outside the peripheral edge of the standard position light transmission hole positioned at the standard position; and a light transmission restriction unit which is integrally provided on the fixing support member, which is disposed at a position crossing the optical axis, which permits passing of light, and which restricts a diameter of the passing light, wherein the light transmission restriction unit restricts the diameter of the light passing therethrough in such a manner that the diameter of the passing light is restricted to a diameter which is smaller than a minimum distance from the peripheral edge of the standard position light transmission hole to the optical axis within a range of a tolerable error of a positional displacement caused in the standard position light, transmission hole by the one rotational movement over the predetermined angle with the predetermined time interval of the rotational body.