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Holographic common-path interferometer for angular displacement measurements with spatial phase stepping and extended
Steven Richard Kitchen1, Carsten Dam-Hansen
1Optics and Fluid Dynamics Department, Risø National Laboratory, DK-4000 Roskilde, Denmark. steven.kitchen@risoe.dk
Applied Optics
|January 10, 2003
Summary
A new common-path interferometer technique uses a holographic optical element (HOE) to precisely measure angular deflections. This robust and compact system offers a wide dynamic range, making it ideal for industrial applications like vibrometers.
Area of Science:
- Optical Engineering
- Metrology
- Interferometry
Background:
- Differential measurements of angular deflections require extended unambiguous ranges.
- Existing techniques may involve complex optical setups or active components for phase stepping.
Purpose of the Study:
- To present a novel technique for extending the unambiguous measurement range in differential angular deflection measurements.
- To develop a compact, robust, and potentially low-cost system for industrial metrology.
Main Methods:
- Utilizes a common-path interferometer with a dedicated holographic optical element (HOE).
- The HOE integrates all optical functions, including automatic spatial phase stepping for real-time measurements.
- Probes out-of-plane displacement of three points on an object surface simultaneously.
Main Results:
- Demonstrated a system for measuring angular deflections of a plane mirror with a sensitivity of 2.5 x 10(-7) rad.
- Achieved an unambiguous measurement range of approximately 3.5 x 10(-3) rad, yielding a dynamic range of ~1:14,000.
- The system is inherently stable due to the common-path design and HOE functionality.
Conclusions:
- The novel HOE-based common-path interferometer technique effectively extends measurement ranges for angular deflections.
- The system's compactness, robustness, and potential for low-cost mass production make it suitable for industrial applications, including commercial vibrometers.
- The technique is versatile and can be adapted for measuring various surface displacements beyond angular deflections.