parallel light grating device

A parallel light grating device comprising a plurality of emitters each for emitting a radiation for detecting a presence of an item, a plurality of detectors each for receiving the radiation from one of the emitters so as to determine whether an item has passed a path of the radiation or not, and a plurality of lenses wherein:

• the lenses are disposed between the emitters and the detectors;
• the emitters, the detectors, and the lenses are disposed in a corresponding relationship;
• the radiation from each emitter is diffracted;
• the diffracted radiation is collimated by the lenses to form a grating;
• a distance between any two adjacent ones of the detectors is less than a length of a longitudinal section of the item;
• and
• the detectors are capable of detecting the passing of the item using the grating.