Detection of opaque foreign articles from among transparent bodies

Abstract

Abstract To detect an opaque foreign body (2) such as a piece of stone, from amongst transparent bodies (1) such as of glass, the pieces (1,2) on a moving belt (3) are allowed to drop over a chute (4) where each is separately scanned a plurality of times by a linearly polarized lazer beam (L) transversely to their path of movement, the lazer beam from a light source (6) being reflected by a polygon scanner (7) rotated at constant speed for a period so that each object is scanned two or more times whilst it drops; the reflected light is introduced into a charge-coupled-device camera (9) after passing through a polarizing filter (8) and is detected as an electrical signal; the scanning light is also detected by a sensor (10) and the signal therefrom is divided into pulses by a divider (11) and fed to the camera (9) to control the scanning speed; an analog signal from the camera is also taken by a control circuit and is binary digitized and checked to determine whether the object is opaque or transparent. Opaque objects may be removed by an air blow removing device (12). Most of the polarized beam passes through a transparent piece while only a small fraction thereof is reflected whilst most of the beam is scattered irregularly from an opaque article. The invention provides satisfactory discrimination between the different bodies.

Inventors

• 👤 Masaki C/O Toyo Garasu Kabushiki Kaisha Sawamura

Bibliographic Details