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Closed-loop phase-shifting homodyne interferometry using heterodyne phase detection.
1National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Central 3, Tsukuba, Ibaraki, Japan. y-bitou@aist.go.jp
Applied Optics
|November 22, 2008
Summary
A novel homodyne interferometer uses heterodyne phase detection for precise feedback control. This system successfully stabilizes interference fringes and achieves accurate phase shifts despite micrometer-level vibrations.
Area of Science:
- Optical interferometry
- Precision measurement systems
Background:
- Homodyne interferometers are susceptible to environmental disturbances like vibrations.
- Maintaining stable interference fringes and accurate phase shifts is crucial for high-precision measurements.
Purpose of the Study:
- To develop a phase-shifting homodyne interferometer with enhanced stability and accuracy.
- To implement a feedback control system using heterodyne phase detection.
Main Methods:
- Utilized a backreflected beam from a reference flat with a wedge angle.
- Integrated an internal heterodyne detection system to generate feedback error signals.
- Employed a digital high-speed lock-in amplifier for signal processing.
Main Results:
- Successfully demonstrated interference fringe stabilization in a homodyne interferometer.
- Achieved accurate pi/2 phase shifts even under micrometer-order vibrations.
- Validated the effectiveness of the heterodyne phase detection feedback control.
Conclusions:
- The developed phase-shifting homodyne interferometer offers robust performance against vibrations.
- The feedback control system significantly improves the stability and accuracy of homodyne interferometry.
- This technique is applicable to general nonpolarizing homodyne interferometer configurations.
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