Apparatus for detecting edge of semitransparent plane substance

摘要

An apparatus for detecting an edge of a semitransparent plane substance provided with a light source array including a plurality of light sources and a photosensor array including a plurality of photosensors. A selection circuit selects a pair of one of the light sources and one of the photosensors, respectively, and a comparator circuit compares the outputs of each of the photosensors in each pair when no detected substance exists between the light source array and the photosensor array, and the corresponding outputs when a substance exists between the light source array and the photosensor array, so that the edge portion of the substance can be detected.