A phase-triggering technique to extend the phase-measurement range of a photorefractive novelty filter microscope

A photorefractive-based novelty filter microscope can be used for real-time phase measurement of phase changes, introduced by moving objects or microorganisms, from 0 to π radians. In this article, we propose a method to extend the phase-measurement range over the entire 2π radians and demonstrate its validity both experimentally and numerically. Our method makes use of the fact that the slopes of the calibration curve of the novelty filter microscope in the positive- and the negative-phase regions have opposite signs. By applying a known external phase trigger to the novelty filter system, the positive- and negative-phase regions can be differentiated.