A note on trace-to-trace correlation in visual displays: elementary pattern recognition

In intensity-modulated visual displays used for the detection of pulse signals in noise, e.g., the P.P.I., the B-scan cathode-ray display, or the chemical recorder display, a normal requirement is to recognize the signal not only by its amplitude but also by the fact that it extends across two or more scans or traces. This means, in effect, that detection is partly a matter of recognizing the correlation of signal pulse from one trace to the next. In this note, subjective measurements of the effect of this correlation on the threshold signal/noise ratio are given and discussed. It is shown that over the range of input signal/noise ratio from ¿10 to 0 db, the reduction of threshold is about 2.2 db per doubling of the number of traces, as compared with the 1.5 db theoretically obtained from "integration" of successive traces.