Apparatus for checking the proper operation of a laser telemeter

Claim 1

In a laser telemeter system comprising a laser transmitter including a laser, a discharge source and an energy source for supplying energy to said discharge source wherein said discharge source triggers said laser; a receiver including a photomultiplier, a chronometer, having a maximum capacity and a gate coupled between said photomultiplier and said chronometer, said gate being rendered conductive the transmission of a laser pulse and noncoductive by the reception of the echo of said laser pulse from a target, whereby the chronometer measures the time interval between the transmission of said laser pulse and the reception of said echo; the improvement comprising: a. an AND circuit having at least two inputs and one output wherein the presence of a signal at said output indicates proper operation of said system; b. first measuring means for measuring the luminous energy of said laser pulse and for producing an output in accordance therewith; c. means, coupled to said first measuring means, for applying a first signal to one input of said AND circuit when the output of said first measuring means is above a predetermined threshold; and d. comparator means coupled to the output of said chronometer for applying a second signal to a second input of said AND circuit if the output of said chronometer has not reached said maximum capacity when said echo of said laser pulse is received.