Patent ID: 7601945

Claim:
A position detecting device for detecting an absolute position of a movable member adapted to be moved along a predetermined direction, the position detecting device comprising: a scale having a plurality of light emitting elements located at spacings therebetween along the direction; a sensor, mounted on the movable member, for detecting light radiated from at least one of the light emitting elements within a predetermined detection range that is longer than a largest one of the spacings and for outputting a light reception signal according to a position where the light is received within the detection range; and a control section for driving the light emitting elements individually and receiving the light reception signal from the sensor, the control section having a storage section for storing information on respective located positions of the light emitting elements in the scale, wherein, upon receipt of the light reception signal, the control section retrieves from the storage section information on a located position of at least one of the light emitting elements that is being driven, and calculates a position of the movable member based on the retrieved information and the light reception signal.