The experimental procedure and the underlying theory of several methods of calibration are given. The best method has been found to be one in which observation is made on a channeled spectrum, where the channeling is the result of multiple reflexions in a plane parallel plate. The wavelength for which the plate is a λ/4 plate can be found easily to within 10A. Photographs are given to illustrate the channeled spectrum method, and the results of a detailed analysis of the accuracy of this method are shown graphically. A method to get higher precision is indicated. The effect of multiple reflexions on the phase difference of the plate to be calibrated is discussed. Some theoretical and practical details of construction, with particular reference to mica plates, are mentioned.
H. G. JERRARD, "The Calibration of Quarter-Wave Plates," J. Opt. Soc. Am. 42, 159-165 (1952)