Abstract

A long-standing problem in polarized light microscopy has been the inability to achieve simultaneously high spatial resolution and high contrast due to the rotation of the plane of polarization at oblique interfaces between crossed polars. In such cases, the system is highly astigmatic and produces severely degraded images. The theory of polarization aberrations is applied to the analysis of three solutions to this problem: (1) reducing the system aperture to block troublesome high-aperture rays; (2) the AVEC-POL method, in which high bias compensation introduces counterbalancing aberrations; and (3) the polarization rectifier, an optical element designed to introduce equal and opposite rotations of the electric vector. It is shown that a strong linear retarder (e.g., a quarter-wave plate) following the objective lens contributes a set of circular retardance polarization aberrations which balance linear polarization aberrations from the lens. Reducing the system aperture does not make effective use of these balancing aberrations. In the AVEC-POL method, the retarder-induced aberrations act to correct the system by bringing the pupil closer to radial symmetry and uniform brightness. The polarization rectifier operates in a different fashion, although it too relies on circular retardance aberrations and possesses residual errors in its pupil function similar to AVECPOL.

© 1988 Optical Society of America