| 摘要 |
A method for detecting a period of a periodically varying signal and/or an inclination of a specimen utilizing an exposure apparatus wherein a coherent light is divided into first and second lights and the first light is irradiated onto the specimen at a predetermined angle, and a reflected light thereof and a reference light as the second light interfere with each other so as to form interference fringes, the interference fringes are detected, and the inclination of the specimen is detected from a pitch representing a period of the interference fringes. The method includes detecting a spectrum of a signal intensity obtained from the detected interference fringes or the periodically varying signal, subjecting the detected spectrum data to a fast complex Fourier transformation, calculating a true spectrum peak position jR in accordance with a relationship jR=j0+ DELTA , where j0 is a detected spectrum peak position and DELTA is a correcting value estimated from the Fourier transformed spectrum data adjacent to j0, and calculating the pitch P of the period of the signal intensity information in accordance with a relationship P=N/jR, where N is the number of sample data points for the complex Fourier transformation. Further, the method includes calculating the inclination of the specimen from the pitch P.
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