Two-wavelength laser diode interferometer with time-sharing sinusoidal phase modulation.
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.
Suzuki
Takamasa
T
Faculty of Engineering, Niigata University, Japan. takamasa@eng.niigata-u.ac.jp
Yazawa
Takayuki
T
Sasaki
Osami
O