Micropolarizers in real time polariscope

Abstract

This contribution deals with a polariscope, an instrument for determining internal strain in a transparent medium by exploiting its polarization transmission: When a sample of birefringent material is inserted in a polarized beam of light a fringe pattern is observed. The pattern is captured by a camera and processed to reveal internal stresses in the probe. However, in order to completely specify stresses, four patterns obtained under different optical conditions are used. These can be achieved either by using a rotating analyzer in the optical setup or by applying the so called “Multispec Imager” approach where the output beam is divided into several parallel beams which can then be directed to separate sections of a single camera or to several individual cameras. Disadvantages of the former solution is the requirement of a mechanically rotated component (necessitating a driving motor and longer measurement time whence this concept is far from being suitable for real-time use) and of the latter is its price and higher complexity of the optical layout. The use of micropolarizers in a digital polariscope removes all stated disadvantages, hence such a polariscope processes a single beam (no need of beam-splitting) and one fringe pattern (no need of a rotating analyzer).