Abstract: A scanning spot (54) moves over a pair of masks (50, 58) provided with respective arrays of transverse slits (52) of varying widths along the path of the spot or of transverse windows (60) at varying positions along a line (62) at an angle (.alpha.) to the path. Pulses of light passing through the slits and windows are detected (56.sub.W, 56.sub.L) and corresponding signals compared (102, 122) to predetermined values to produce digital pulses which are directed to counters (92, 94) to provide digital displays (126, 128) of spot width and length. Corresponding analog signals also may be provided (130-136).

Abstract: The present invention is an all digital timing and address generator which automatically adjusts its output pulse intervals to fit within the duration of periodic input pulses. The intervals are alway synchronous with the leading edges of the input pulses, and their number within the duration of a periodic input pulse is selectable in increments of one. The generator uses direct digital feedback to control its output timing for changes in input pulse width, and employs an integer time mark to prevent "unlocking" on non-integer width input pulses.