AN ELECTROOPTICAL FREQUENCY DOUBLING METHOD TO REMOVE ELECTRICAL NOISE IN LASER RANGEFINDERS

The main limitation of phase-shift laser rangefinders is the disturbance created by the current source used to modulate the intensity of the light beam. This source, of frequency f(o), generates an induced interference voltage which is vectorially added to the photoelectric signal measured. A method for modulating the light beam using the nonlinearity of an electro-optical crystal allows this disadvantage to be eliminated since the signal measured is a frequency multiple, nf(o). Experimental results obtained under unfavorable shielding conditions show the efficiency of the proposed method.