On the theory of simultaneous retardance measurement of two phase plates

One of the serious problems in polarization metrology is that of calibrating phase plates. These plates are essential components in most polarization systems and incorrect values of their retardances may introduce serious errors in experimental results. The simplest method for retardance measurement is the modified Sénarmont arrangement which allows for determining the retardances of two plates simultaneously with a single adjustment of the optical system and using simple mathematical expressions. However, a drawback of the method arises from the trigonometric functions in the mathematical expressions giving two possible values for the retardance of each plate. This requires knowing in advance whether each plate introduces retardance smaller or greater than π at the working wavelength. In this work, this restriction is removed. The Poincaré sphere representation is employed in the treatment and experimental results are presented.