A double-refractig interference system with variable wavefront shear has been adapted to wave-
lengthmetry ot nochromatic light. The interfrixige spacing is directly measured while the wavelength
is read out frog a calibration plot or a data table stored in the computer mery. The proposed technique is especially suitable or aauring the peak wavelength o nocbroatic intererence
filters. The measuring accuracy as good as Al =
m is easily achievable.