Abstract
The PISTIL interferometry has been recently developed for the wavefront sensing of phase delays (pistons) and tilts of segmented surfaces, used in many domains such as astronomy, high-power lasers or ophthalmology. In this paper, we propose a two-wavelength version of this interferometer developed to bypass the dynamic range limitation of the ambiguous 2π phase wrapping. Principle of the technique is presented, along with experimental results obtained with a demonstration deformable mirror PTT-111 from Iris AO. Above wavelength pistons are measured with a precision and accuracy below λ/100, making the two-wavelength PISTIL interferometry a high-dynamic range technique. To prove these performances, we successfully compare the results in terms of precision and accuracy with those of a reference phase-shifting Interferometer, from a blind experimentation.
Highlights
Today, there exists a large panel of projects relying on segmented wavefronts tailoring, either in coherent combination of elementary fiber lasers [1,2,3], astronomy [4], or ophthalmology [5].In those domains, innovative phase analyzers have been developed to provide a solution to measure accurately and / or co-phase the segmented wavefronts [6,7,8,9,10,11]
PISTIL concentrates on the differential phase between each segment, meaning it is sensitive to variations of relative piston, tip and tilt, with high-dynamic range in the case of Two-Wavelength PISTIL
Once the two-wavelength PISTIL setup is demonstrated at the metrology laboratory, we compare its performance with respect to the Phase-shifting interferometry (PSI) reference analysis
Summary
There exists a large panel of projects relying on segmented wavefronts tailoring, either in coherent combination of elementary fiber lasers [1,2,3], astronomy [4], or ophthalmology [5] In those domains, innovative phase analyzers have been developed to provide a solution to measure accurately and / or co-phase the segmented wavefronts [6,7,8,9,10,11]. It is a member of lateral-shearing interferometers family and evolution of the recent PISTIL concept [12] This phase analyzer is very handy because it consists of few optical elements packable and does not require an external reference wavefront. This quality makes it suitable for on-site measurements (outside the laboratory). Experimental setup for the two-wavelength PISTIL is presented in Section 4, along with a first experimental demonstration of the method, and a comparison with the independent analysis made by PSI
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