Patent GB-1338329-A (GB)
Title: Optical comparator and inspection apparatus
IPC: G01B9/08
Filed: 1971-08-09
Abstract: 1338329 Optical projection apparatus P S KEMPF 9 Aug 1971 [12 Aug 1970] 37245/71 Heading G2A A comparator and inspection apparatus includes a carriage 28 sliding on tracks 26 and carrying a frame 34 designed to hold a master 84 and a sample component 88 and being movable perpendicularly to the tracks 26. Above this carriage 28 and frame 34 (see Fig.11) is a lamp housing 120 directing light through its openings 136 on to corresponding selected areas of the components 84, 88. Lenses 152, 156 and mirrors 154, 158, 160 direct the reflected light from the components on to rear projection screen 14. As shown the lamp housing 120 includes a tubular source 134 (a second source 138 can also be provided) a first reflector 122, secondary reflectors 130, 220 and a chamber 142 supplied by a forced draught cooling system via duct 140. The lamp housing 120 is positioned for the episcopic projection of the components 84, 88, which may be printed circuit boards, however the master 84 may be replaced by a transparent replica in which case one of the openings 136 is closed by door 220 (which doubles as part of the secondary reflector) and light source 216 and diffuser 218 used. As shown in Fig.4 the carriage 28 is moved along tracks 26 by motor 42 and drive 42 and the frame 34 on the carriage 28 by means of a handle 50 held by the operator. Knob 64 when rotated moves strips 74, 76 together/apart by means of the opposite threading of rods 52, 54, rotatably connected by parts 36, 60, 62. A similar control operated by knob 118 moves clamps 96 which with clamps 90, 92 grip component 88; clamps 78, 80 grip the component 84. In Fig.11, the folded optical path project an inverted image of the master component 84. However an extra mirror can be used, Fig.14 (not shown) to give two non-inverted images. Movement of the carriage 28 and frame 34 and plates 162, 164 permit corresponding selected areas of the components 84, 88 to be projected side by side on the screen 14. To obtain such corresponding areas mirror 154 is provided with a spring adjustment. Lenses 152, 156 are provided with a focusing device as shown in Fig.8 in which the pulley 192 is connected by belt(s) to a manual control knob whose rotation pivots the plate about the screw 182. Both lenses 152, 156 as therefore adjusted equally and simultaneously individual lens adjustment is provided by nut 186 on the focus of lens 15 only so that both lenses are identically focused prior to adjustment by means of pulley 192. For lens 152 the nut 186 is replaced by a conventional nut. The casing 12 has reference numerals, Fig.15 (not shown) extending across the base of the screen 14 as viewed in Fig.11. These in conjunction with the letters on the frame 34 provide a grid system by which faulty points of the sample component 84 can be located. A marking pen,Fig. 3 (not shown), can be inserted through trap door 240 in the casing 12 to mask such components and a display device, Fig.19 (not shown), is provided on which the now-marked faulty component 88 is placed with an inspection card listing its faults. The card (258) is so designed that the card and component 88 may be viewed relatively superimposed on the display device when the markings on the card (258) indicate the faulty parts of the component 88.