An electro-optical 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