Patent ID: 7279695

Claim:
An edge position detecting apparatus, comprising: a reflective optical sensor that outputs light to a supporting surface of a supporting member to support a target detection object, and that receives a reflected light; a moving unit that moves the reflective optical sensor along the supporting surface of the supporting member in a specified direction; a reflected light data generating unit that generates a reflected light data when one of the supporting member and the target detection object on the supporting member is optically scanned in the specified direction by obtaining a light-receiving signal from the reflective optical sensor while moving the reflective optical sensor via the moving unit in the specified direction; and a detecting unit that detects an edge position of the target detection object in the specified direction based on the reflected light data generated by the reflected light data generating unit, wherein the reflected light data generating unit generates the reflected light data respectively when the target detection object is supported by the supporting member and when the target detection object is not supported by the supporting member, wherein the detecting unit detects the edge position based on a relative change between a first reflected light data and a second reflected light data, where the first reflected light data is generated by the reflected light data generating unit when the target detection object is supported by the supporting member, and the second reflected light data is generated by the reflected light data generating unit when the target detection object is not supported by the supporting member, wherein the detecting unit determines a deviation between a data value of the first reflected light data and a data value of the second reflected light data at each detection position that changes in accordance with movement of the reflective optical sensor, and wherein the detecting unit detects one of a position at which a data value related to the deviation exceeds a predetermined threshold value and a position at which the data value related to the deviation falls below a predetermined threshold value as an edge position of the target detection object.