Optical interferometry using liquid crystal phase shifter

Abstract

The need for ultra-high precision components with sub nanometer surface roughness is now indispensable in areas such as optics, biomedical and other industries. The urgent needs of these industries have promoted the development of several techniques with the ability to produce ultra high precision surfaces and hence the necessity to test them. This present manufacturing trend, along with the need to use materials with complex characteristics and the need for speed, has made the development of new surface profiling techniques essential. While using interferometric techniques in surface profiling, the quantity measured is a wavefront reflected from a surface or transmitted through the object. It involves the interference of two beams, one known as a reference beam and the other, an unknown test beam. The reference beam in an interferometer is usually moved by a fraction of the beam wavelength for a number of times to capture interferograms. These interferograms are further processed using phase shift algorithms to analyze the surface profile.