A multifrequency laser oscillator which generates coherent light of two closely adjacent optical frequencies in rapid succession for recording contour holograms by the double exposure technique. The two light frequencies are selected by a pair of frequency selecting reflectors at one end of the oscillator resonator cavity. At least one of these reflectors is movable between an active position where it reflects the laser beam to select one light frequency and an inactive position where the other reflector reflects the beam to select the other light frequency. The described laser oscillators have a ruby lasing medium and generate coherent light at the R1 and R2 wave lengths of the ruby resonant fluorescence.
Holographic contouring with a multifrequency laser