Detector and method for detecting plate-shaped or sheet-shaped body

摘要

A method of detecting a plate-shaped or sheet-shaped body includes the steps of: arranging a first optical sensor in parallel with one face of a body; arranging a second optical sensor in parallel with the other face of the body and also in parallel with the first optical sensor; turning on a light emitting section of the first optical sensor and a light emitting section of the second optical sensor alternately; monitoring the fluctuation of a detection level detected by a light receiving section of the first optical sensor and the fluctuation of a detection level detected by a light receiving section of the second optical sensor; and recognizing the body when the fluctuation of the detection level exceeds a predetermined value.