A New Technique of Minute Birefringence Measurement by using Simple Polarimetry

This paper introduces the principles and execution of a new technique for minute birefringence measurements based on simple polarimetry. The technique requires only three stepped photoelastic images although conventional phase-stepping methods require four images. To verify the new technique experimentally, a precise crystal wave plate of having 10.0+4.7 nanometers in retardation was used as a specimen. The measurements of the retardation with standard deviation were found to be 10.1+0.467 nanometers, which agreed well and narrowed the deviation in spite of minute amount of retardation. To estimate the measurements accuracy of the angular orientation of the birefringence, the angular position of the rotation stage for the specimen was rotated intermittently 10.0 degrees at a time during the experiment. As a result, the measured offsets of the angular orientation were found to be 10.0+0.792 degrees with standard deviation. It is concluded that the new technique is effective for minute birefringence measurements.