Two-wavelength laser diode interferometer with time-sharing sinusoidal phase modulation |
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Authors: | Suzuki Takamasa Yazawa Takayuki Sasaki Osami |
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Affiliation: | Faculty of Engineering, Niigata University, Japan. takamasa@eng.niigata-u.ac.jp |
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Abstract: | We describe an interferometer system that uses two separate wavelengths to measure step height. The overlapping interference images detected by a CCD camera are easily separated by an ordinary integrating-bucket method and time-sharing sinusoidal phase modulation, in which two laser diodes are alternately modulated with a sinusoidal signal. A phase map is obtained only for the laser diode into which the modulation signal is injected. In this instance, a 1-microm step height was accurately detected. |
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