GB1445189A - Circular scanning optical pattern tracer - Google Patents

Abstract

1445189 Pattern following WESTINGHOUSE CANADA Ltd 13 Dec 1973 [4 Jan 1973] 57728/73 Heading G3N In an optical line or edge tracer of the circular scanning type, in which a scanner 10 provides pulses at 13 for front and rear crossings of the line, sine and cosine waves, indicating the rotational position of the scanner also being provided, at 11 and 12, the latter two, sampled at the forward pulse timings, providing Y and X drive signals, the sine and cosine waveforms, and the drive waveforms are combined to provide a sinusoid whose phase represents the direction of the scanned line, the sinusoid being clipped to provide gating pulses to be generated during an enabling interval encompassing the expected timing of the next forward crossing pulse. As shown, the sample pulses are produced only in the absence of a blanking signal, present for more than 180 degrees of the scan, from unit 34 provided a gating pulse is present. A set of nor gates (45-47) Fig. 2 (not shown) ensure that the gating pulses are provided if the scanner is on the line, an end-of-line detector 35 including monostable (51) Fig. 2 being provided, and if the scanner is on a pattern, an off-pattern detector 33 comprising monostables (55, 54) Fig. 2 being provided. With switch (53) closed, the gating pulses may be provided for a pre-set time, which may be proportional to the tracer speed, after the offpattern state is detected. Should the switch (53) be open, the scanner will respond to a back pulse, the drive reversing. Assuming the angular direction of the line to be #, multipliers 16, 20 produce sin (wt + α) sin #, cos (wt + α) cos # respectively the summer 28 producing the sinusoid cos (wt + α-#), which is clipped at a level related to its amplitude to produce the gating pulses. A light emitting diode diode (52) Fig. 2 indicates the presence of a line being scanned. The controlled machine may be a cutting torch.