Real-time phase measurement with a photorefractive novelty filter microscope

Abstract

A photorefractive two-beam-coupling based novelty filter is sensitive to amplitude and phase changes. However, the phase sensitivity of this device has remained unexploited until now. In this paper we develop and demonstrate a method to overcome the effects of contour formation in novelty filter output and consequently employ the novelty filter as a quantitative real-time transient phase-measuring instrument. A microscope based on a two-beam-coupling novelty filter is implemented and is used for detecting as well as measuring phase changes introduced by moving homogeneous phase objects. The two-dimensional output from the microscope is analysed, and a method based on the intensity dependence of the photorefractive time constant is proposed to overcome the effects of contour formation in the context of real-time transient phase measurement. The phase transfer function of the novelty filter system is experimentally determined and a phase measurement resolution of at least λ/20 at 532 nm is achieved.