FIELD: optics. SUBSTANCE: two-beam interferometer is excited by the emission whose wave length is measured. The path difference is inserted. The wave length is calculated by the path difference. The new feature of this method is that the desired optical path difference is inserted in it, the phase difference of the interferometer beams corresponding to the path difference is measured by the frequency-independent method. The wave length is calculated both by the known path difference and by the measured phase difference. EFFECT: enhanced accuracy of measurements. 3 cl
