| 摘要 |
PURPOSE:To obtain a device which has a small error in measurement by passing a quantized reflection factor through a digital filter and correcting a phase according to its frequency. CONSTITUTION:Detectors 11A and 11B outputs the quantity of projection light and reflected light as electrical signals, which are amplified by amplifiers 12A and 12B and then inputted to A/D converters 14A and 14B. A wave number scanner 13 scans a preset number of waves to irradiate a sample with homogeneous light and data sequences which are quantized and digitized according to the pulses are inputted to the CPU of a computer. A reflection factor calculation part 15 calculates a reflection factor and a digital filter part 16 removes high- order components. Then, a frequency and phase detection part 17 detects the frequency of data roughly and a phase correction part 18 corrects the phase delay of the data according to the detected frequency. A film thickness calculation part 19 calculates film thickness by using the data.
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