An Automatic TV Tracking Theodolite for Range Instrumentation

Abstract

The factors affecting the design of a gated Automatic TV Tracking System are discussed, and a system mechanization to achieve the design objectives is outlined. Only the composite video of a closed-circuit TV system is required as an input. A study of the dynamic performance of typical targets indicates that the unpredictable target motion in a frame period of 1/30 sec must be an extremely small fraction of the field of view required for initial target acquisition. This permits the use of a small tracking gate in the larger acquisition field, since the target coordinates of the previous frame may be used to position the gate. This small gate permits a signal-to-noise enhancement and effectively rejects extraneous targets outside the tracking gate. The tracking is effected by subdividing the tracking area into equal early and late video gates in each coordinate. The differential video between these gates is applied to an electronic integrator in such a manner that the integrator output voltage, which is also the reference for the generation of the early-to-late gate transition, changes to place this gate transition on the target. The integrator voltages are, therefore, a measure of the target coordinates in the TV field. The operation of an experimental system fabricated to determine the feasibility of applying this technique to a range-instrumentation system has produced tracking accuracies of better than 0.05 milliradian in an acquisition field of 10×10 milliradians. Current developments and additional applications of the technique are discussed briefly.