Optical wavefront measurement using a novel phase-shifting point-diffraction interferometer | SPIE Newsroom: SPIE

Optical wavefront measurement using a novel phase-shifting point-diffraction interferometer Pietro Ferraro, Melania Paturzo and Simonetta Grilli A simple point-diffraction interferometer with phase-shifting capability has been designed using a pinhole fabricated from a lithium niobate crystal. 1 March 2007, SPIE Newsroom. DOI: 10.1117/2.1200702.0621 Optical wavefront testing is an important issue in several different fields ranging from astronomy to any application with optical testing requirements. A variety of techniques are currently applied in such diverse fields as optical component testing and wavefront sensing that require the qualitative or quantitative analysis of optical phase disturbances. And since these cannot be directly observed, a method must be used to extract the desired information indirectly, for example, through generation of fringe patterns in an interferometer. The use of a point-diffraction interferometer (PDI) has several advantages when compared with other methods, the most important being its common path design (see Figure 1). In a PDI, an interferogram can be produced with only a single laser path rather than with the two paths required by Mach–Zehnder or Michelson interferometers. This is especially important in the measurement of large objects such as wind tunnel flows, in which the optical paths are very long and air turbulence must be minimized along the paths. The simple common path design requires relatively few optical elements, thereby reducing the cost, size, and weight of the instrument while also simplifying alignment. The PDI has been used to test a variety of optical elements, and its simple alignment makes it useful for optical testing in the IR, UV, and X-ray spectral regions even in astronomy applications. SEARCH THE SITE