GB856185A - Digital pattern producing equipment - Google Patents

Abstract

856,185. Optical and electrical sensing. BALDWIN PIANO CO. Dec. 19, 1956, No. 38711/56. Class 40 (2). [Also in Groups XXXV and XL (b)] Disc records, carrying concentric rings of periodically-related digital patterns are produced on photographic plates 45 by means associated with photo-electrically sensed master patterns on a reference disc 15 and frequency. dividing circuits comprising flip-flops 21 ... 37. Opaque and transparent tracks on the revolving disc 15 when aligned with the pattern of a grating 18 are detected by light from a lamp 17 falling on the photo-cell 16, pulses from which control flip-flop circuits 21 ... 37. To maintain spaced phase relationship between successively recorded tracks, another photo-cell 38 initiates reset signals at every revolution of the disc 15 to throw switches 82-S16 in accordance with the pattern to be produced on the plate 45. The flip-flop circuits are selected by a switch S17 to control a waveshaper and amplifier 46 which causes " Duralumin " (Registered Trade Mark) ribbons A and B in the field of a permanent magnet to move when a current is passed through them so as to modulate the light from a source 51 falling on to the photographic plate 45. A prism 53 provides a visual check. The speed of the turntable 12 is controlled retroactively by supplying part of the output of the photo-cell 16 to a discriminator 56 which regulates the speed of the motor 14. For the generation of sine function codes the grating 18 (indicated as 68 in Fig. 5, not shown) is mounted on ballbearings and revolved by gear chain in the same direction and relative speed as the plate 15. To obtain a reference pulse at two positions during each revolution a reflector is fitted to the underside of the disc and two lamps and photo-cells arranged to co-operate with it at two positions (Fig. 8, not shown, refers). The combined photo-cell output may be fed to a single limiter to produce steep fronted waves and the accuracy of the plate improved by making a plate using two photo-cells spaced 180 degrees apart, then making a further plate therefrom with the photo-cells at half the previous angle and so on.