New photodetector array based optical measurement systems

摘要

A method and apparatus are provided for analyzing the light pattern produced on a photodetector array. The signal produced by the array is filtered with a low pass filter and the output of the filter is differentiated to obtain either the first or second derivative of the filtered signal for one or more points in the pattern. The zero crossing of the differentiated signal is detected and the zero crossing point is timed relative to a further point, e.g., the start of the scan of the array, so as to obtain an output related to the position of the corresponding point or points in the pattern.