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, Carolyn R. Mercer, Glenn Beheim, 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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