| 摘要 |
PURPOSE:To measure refractive index on an object at a high accuracy in a short time with a high S/N ratio free from background light, by inserting a phase modulation element into an optical path to a sample to control an angle of incidence into the sample with the regulation of the bearing of a linearly polarizing element or an analyzer. CONSTITUTION:A mechanism 18 is provided to control an angle phi0 of incidence into the surface of the sample 1 and a linearly polarizing element 12 is placed in an incidence optical path so that the polarization bearing of incident linearly polarized light is + or -45 deg. in the initial state. A bearing control mechanism 21 is provided to turn the bearing of the element 12 by theta deg. from + or -45 deg. and a phase modulation element 13 with the amplitude delta0 and the modulation angle frequency omega is arranged in a reflection optical path so that the delay axis bearing thereof is + or -45 deg.. An analyzer 14 is provided on the incident side of the element 13 so that the transmission axis thereof is 0 deg. (90 deg.) and moreover, a photo detector 15 is provided while a separation circuit 16 is provided to extract omega and 2omega and DC components of a detection signal independently. The polarization bearing of the element 12 is turned to zero the 2omega component and fixed at an angle theta of rotation from + or -45 deg.. Under a condition, the angle phi0 of incidence is controlled to max the component and then, refractive index of the sample surface and the thickness of a thin film are determined from angles theta and phi0.
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