25 April 1990 Speckle Interferometry Using Fiber Optic Phase Stepping
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A system employing closed-loop phase-stepping is used to measure the out-of-plane deformation of a diffusely reflecting object. Optical fibers are used to provide reference and object beam illumination for a standard two-beam speckle interferom-eter, providing set-up flexibility and ease of alignment. Piezoelectric fiber-stretchers and a phase-measurement/servo system are used to provide highly accurate phase steps. Intensity data is captured with a charge-injection-device camera, and is converted into a phase map using a desktop computer. The closed-loop phase-stepping system provides 90° phase steps which are accurate to 0.02°, greatly improving this system relative to open-loop interferometers. The sys-tem is demonstrated on a speckle interferometer, measuring the rigid-body translation of a diffusely reflecting object with an accuracy of -±100, or roughly ±15 nm. This accuracy is achieved without the use of a pneumatically mounted optics table.
© (1990) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Carolyn R. Mercer, Glenn Beheim, "Speckle Interferometry Using Fiber Optic Phase Stepping", Proc. SPIE 1162, Laser Interferometry: Quantitative Analysis of Interferograms: Third in a Series, (25 April 1990); doi: 10.1117/12.962745; https://doi.org/10.1117/12.962745

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