FOURIER TRANSFORMATION INFRARED SPECTRAL TYPE FILM THICKNESS METER

摘要

PURPOSE:To improve the measurement accuracy by converting one of two light beams which is split in the optical system of a laser interferometer from linear polarized light to circular polarized light and extracting out-of-phase interference signals from the interference light between the linear polarized light and circular polarized light. CONSTITUTION:In the luminous flux splitting optical system for laser light, a 1/8-wavelength plate 23 is provided as a means which converts the linear polarized light into the circular polarized light on the optical axis between a fixed-side plane mirror 3 and a cube half-mirrors 13. Cube samplers 24-26 as cube half-mirrors forming a means which extract the mutually out-of-phase interference signals from the interference light between the linear polarized light and circular polarized light are provided in series on the optical axis behind the cube half-mirror 13. Analyzers 27-30 are arranged on the output sides of the cube samplers 24-26 and attached laser detectors 31-34 are pro vided to the analyzers 27-30. Consequently, when one wavelength of laser light is denoted as lambda, a sample signal can be extracted optically at intervals of lambda/n (n1) and the measurement accuracy is increased up to Xn.