Birefringence measurement of the cellophane film

In this work we describe an experimental technique to measure the birefringence of the cellophane film that has good behavior as half wave retarder. This technique is achieved when the film is placed in a polariscope that consists of a light source and properly arranged polarizing elements and a system of fringes is observed. Using Jones formalism for the system the birefringence appears in the phase term of harmonic functions. Some experimental results are shown.