GB730177A - Improvements in or relating to apparatus for detecting variation of surface characteristics of objects - Google Patents

Abstract

730,177. Sorting photo - electrically. BAIGENT, G. M. July 21, 1952 [July 19, 1951], No. 17196/51. Class 40 (3). In sorting objects in response to light reflected from defective spots on their surface, a number of light-receiving means are directed at an illuminated object viewing position so that each means views a small area of the object and then conducts the light received separately to a light-responsive device through apparatus which so masks the beams successively that a constant amount of light is received by the sensitive device at any one time. As shown, objects to be sorted fall one at a time through an aperture in a housing of the type described in Specification 712,113, in which light reflected from three parts of the object is directed by lens housings 4 through light guides 5 to a " mixing " block 6 which spreads the illumination evenly over the sensitive surface of a photo-electric cell 7. Between the ends of the light guides and the block passes a perforated rotating plate 11, the apertures in which are of such a size and so spaced that unless a defect appears on the object under examination the total cell illumination remains constant as the plate rotates. Thus a small defect on the object under examination reduces the total cell illumination appreciably. The rotating plate may be replaced by a mirror drum or a Kerr cell or other device in which variation of an applied field causes variation of the transformer of a substance. Specifications 492,035 and 662,685 also are referred to.