Abstract
A composite quarter wave plate has been made from two sheets of transparent polymers. The condition in which two phase plates satisfy as a quarter wave plate is discussed using the Poincare sphere. The relation between azimuth angle and retardation of each plate is calculated and shown on the Tables. Retardations of two plates must be measured for each wavelenght. The composite quarter plate is used as a circular polarizer for all visible region of light by changing azimuth angles of phase plates. A trial composite quarter plate is tested for several wave lengths. It is confirmed that the composite quarter plate can be used as a quarter plate even if the wavelength of light changes.
