Development of automatic birefringence evaluation system

Birefringence mapping is useful for research, development and quality control of rubbed polymer films in LCD as well as stress and strain in optical materials. We developed for this purpose an optical heterodyne method which enables fast measurement with high sensitivity. The automatic birefringence evaluation system utilizes a frequency-stabilized transverse Zeeman laser (STZL) which generates simultaneously two orthogonally frequency polarized beams with slightly different frequencies. The phase difference between two beat signals detected by photodiodes is equal to the retardation of the sample. It is not necessary to rotate samples because the azimuth angle of polarization of STZL can be rotated by a half-wave plate. Main performances of this system are shown