| 摘要 |
A method and an apparatus, for measuring an optical heterodyne interference, comprising the following steps of: generating a reference light and a measurement light, differing from each other in frequency thereof; irradiating the measurement light on a target to be measured through a beam splitter; reflecting the reference light upon a mirror; obtaining an interference light of a reflection light from the target to be measured and the reference light reflected on the mirror, thereby measuring a surface condition or detecting a surface defect on a target to be measured, wherein the reference light is either one of S-polarization light and P-polarization light, while the measurement light is the other one of S-polarization light and P-polarization light, an electric signal of the interference light is obtained upon a light receiving element by obtaining the reflection light from the target to be measured and the reference light reflected upon the reference mirror from the beam splitter through a polarizing plate, wherein an axis of the polarizing plate is so set by rotating the polarization plate that the electric signal obtained from the light receiving element goes down to minimum under condition of shutting off a light transmitting through the beam splitter among the reference light and the measurement light, thereby measuring the surface condition or detecting the surface defect on the target to be measured.
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