The principles for measuring the extinction ratio and
transmittance of a polarizer are formulated by use of the principal
Mueller matrix, which includes both polarization and
depolarization. The extinction ratio is about half of the
depolarization, and the contrast is the inverse of the extinction
ratio. Errors in the extinction ratio caused by partially polarized
incident light and the misalignment of polarizers can be corrected by
the devised zone average method and the null method. Used with a
laser source, the null method can measure contrasts for very good
polarizers. Correct algorithms are established to deduce the
depolarization for three comparable polarizers calibrated
mutually. These methods are tested with wire-grid polarizers used
in the 3–5-μm wavelength region with a laser source and also a lamp
source. The contrasts obtained from both methods agree.
© 1998 Optical Society of America
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