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GUO Dongmei
WANG Ming
School of Physical Science and
Technology,
Nanjing Normal University,
Nanjing 210000, China
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NEW SELF-MIXING MICRO-
INTERFEROMETER BASED ON
EXTERNAL PHASE MODULATION*
Abstract: A new self-mixing
micro-interferometer based on external phase modulation is
presented. Self-mixing interference occurs in a laser diode (LD)
by reflecting the light from a mirror-like target in front of
the laser. Sinusoidal phase modulation of the beam is obtained
by an electro-optic crystal (EOC) in the external cavity. The
phase of the interference signal is demodulated by Fourier
analysis method. The combination of the modulation and
demodulation decreases the sensitivity of the instrument to
fluctuations of the laser power and the noise induced by
environment. Experimentally, the new micro-interferometer is
applied to measure the micro-displacement of a high precision
commercial PZT with an accuracy of <10 nm.
Key words:
Micro-interferometer Self-mixing interference Displacement
measurement |