GB854657A - Inspection process and inspection device for detecting differences in two objects - Google Patents

Abstract

854,657. Photo-electric comparison apparatus. ROBOTRON CORPORATION. April 23, 1959, No. 13869/59. Class 40(3). An object A, Fig. 1, is examined and compared with a standard object S (or a photographic reproduction thereof) by means of photo-electric cells 17 and 18 which are exposed through a mechanism 10-12 arranged to effect simultaneous and identical scanning of the two objects. The outputs of the two photo-electric cells are applied to a comparator circuit 19 (illustrated in detail in Fig. 7, not shown), any difference between the object and standard causing operation of a load circuit 20 which may comprise a signalling device or a mechanism to cause removal of an improper object from, say, a conveyer belt. The two objects are illuminated by sources 62 and 63, and optical systems 14 and 15 form images on ground glass plates 8-9 immediately adjacent the scanning mechanism. In the arrangement shown in Fig. 1, the scanning mechanism comprises an assembly of overlapping, radially apertured discs arranged as illustrated more fully in Fig. 2. The discs are rotated in the same direction, disc 11 being rotated 10-50 times more rapidly than discs 10 and 12, and over the areas 39 and 40, where the images of the two objects are located, expose through passages 41 and 43 (where the radial apertures intersect) which effect scanning over the image areas in a series of overlapping lines. In a simplified arrangement one of the outer discs is omitted and the scanning is effected by through passages 41, 42 or 43, 44. Fig. 6 shows a modification employing two rotating discs 152, 153 and a slowly reciprocating plate 150 driven via rod 160 by wheel 161. Fig. 10 shows a further modification employing a single rotating disc 179 with two plates 170, 171 which are reciprocated in opposite directions by linkage mechanism 172-177 driven by wheel 178. The scanning mechanism together with the standard or a reproduction may be mounted on a support so that it may move along in step with a moving conveyer belt in order to inspect objects carried by the belt. In one arrangement, Fig. 8 (not shown), for use where the objects are spaced at equal distances on the belt, the support engages one of series of notches in the belt (spaced apart at the same distance as the objects) and travels with belt until it meets a stop when it returns under spring action until it engages the next preceding notch and repeats the operation. In another arrangement, Figs. 9 and 11 (not shown), for use where the objects are spaced apart on the belt at unequal distances, the support carries a photo-electric cell (additional to those used for examination) which is exposed to a light beam from a source on the opposite side of the conveyer belt and causes the support to be clutched to the belt so as to travel with it whenever an object interrupts the beam. A further photoelectric cell is employed to disengage the clutch and allow the return of the support under spring action to await the next object.