Automatic ranging in an active television system

Claim 1

An automatically ranged active television system comprising, in combination: a. a pulsed transmitter; b. a gated television camera providing a video output; c. an optical display means coupled to the output of said gated television camera and having a raster scan having upper and lower halves; d. timing circuitry coupled to synchronize the raster scan of said optical display; e. a switching circuit having an input coupled to the output of said gated television camera, and having first and second outputs, said switching circuitry being coupled to and synchronized by said timing circuitry such that a signal indicative of the video output of said gated television camera during the upper half of the raster scan is provided at said first output and a signal indicative of the video output of said gated television camera during the lower half of the raster scan is provided at said second output; f. differential integrating means connected to said first and second outputs of said switching circuit and having an output comprising an error signal indicative of the difference in the video signals provided respectively during the upper and lower halves of the raster scan; g. a pulse width modulator coupled to the output of said differential integrating means providing an output comprising a range delay signal having a pulse width determined by the error signal; h. gating means having an input coupled to the output of said pulse width modulator and providing a first gate pulse to said pulse transmitter and a second gate pulse to said gated television camera, said gating means being synchronized by said pulse width modulator such that the second gate pulse is initiated at a time after the initiation of the first gate pulse equal to the width of the range delay signal, whereby the closed loop control of ranging of said active television system is provided.