JPS5647723A - Rotation measuring method for light phase and plane of polarization - Google Patents

Abstract

PURPOSE:To lower applied voltage by a method wherein the half-wavelength voltage of a crystal as a sample is indirectly measured from a phase change which gives by the applied voltage of the crystal as the sample to the optical beams of modulation at 100% by the applied voltage of a crystal, which is easily modulated, except the crystal as the sample. CONSTITUTION:Laser rays from a laser light source L pass through a polarizer P, pass through a crystal M in substance, which has a great Pockels effect, such as lithium tantalate (LiTaO3) or lithium niobate (LiNbO3) or the like, and is branched by means of a beam splitter BS. Modulation at 100% is previously provided to passing light easily by applying voltage to the crystal M, whose half-wavelength voltage value is small, here, voltage, which largely differs from the applied voltage of the crystal M and has frequency which is easily discriminated, is slightly applied to a crystal S as a sample, a phase change of the light of modulation at 100% generated by application of the voltage is detected, and a half-wavelength is measured from the applied value and the quantity on the change.