Simultaneous measurement of phase retardation and optic axis of wave plates

A simple method used for simultaneous measurement of phase retardation and optic axis of wave plate by employing 1/4 wave plate is demonstrated. The theoretical analysis of the measuring principle is presented in detail. In the measurement, after adjusting a standard 1/4 wave plate and the fast （slow） axis of the plate to be measured parallel to the pass axis of the polarizer, the plate to be measured is rotated by 45^0 counterclockwisly. A stepping motor is used to rotate the analyzer. The experimental data are collected by a photodetector and then sent to a computer. According to the output data curve, the phase retardation and optic axis of the plate to be measured can be obtained simultaneously. To test the feasibility of the method, a λ/2 and a λ/8 wave plates are used as examples to demonstrate the measurement procedures. The phase retardation measurement accuracy is better than 0.5×10^-2. This method can be used to measure the arbitrary phase retardation conveniently.