Inspection apparatus using optical interferometer

Abstract

According to an aspect of the present invention, there is provided an inspection apparatus using an optical interferometer including splitting and combining means ( ) for splitting light from a light source ( ) into incident light ( ) irradiated on a sample and reference light ( ) and combining signal light which is light scattered or reflected by the sample ( ) and the reference light, a modulator ( ) for subjecting the reference light to phase modulation and a photo detector ( ) for detecting light combined by the splitting and combining means ( ), the inspection apparatus further including first detecting means ( - ) for detecting amplitudes of first signal components having frequencies of multiples of odd numbers of a fundamental modulation frequency of the modulator in a signal from the photo detector ( ), second detecting means ( - ) for separating and detecting amplitudes of second signal components having frequencies of multiples of even numbers of the fundamental modulation frequency in the signal from the photo detector and means ( ) for calculating an intensity of the signal light by using the amplitudes of the first and the second signal components for providing high signal stability and signal-to-noise ratio and in measuring a sample of a biomedical tissue or the like having large scattering or attenuation of light, distributions of a refractive index and an extinction coefficient up to a portion having a large depth can be measured with high accuracy.