Full-field measurement of the phase retardation for birefringent elements by using common path heterodyne interferometry

A collimated heterodyne light passes through the tested material and an analyzer, full-field interference signals are taken by a fast CMOS camera. The series of interference intensities recorded at any pixel are the sampling points of a sinusoidal signal. From those points, the associated argument of that pixel can be derived by a least-square sine fitting algorithm on IEEE 1241 Standards. Subtracting the average argument of the reference signal, the phase retardation of that pixel can be obtained. The phase retardations of other pixels can be obtained similarly. Its validity is demonstrated.