Quartz optical rotation (sinistral), birefringence image

A simulated birefringence image (taken with polarized light) through a section of a quartz crystal, showing left-handed (sinistral) optical rotation - the characteristic "Airy's spiral" curves in a clockwise direction. The simulation assumed the used of conoscopic illumination in a microscope equipped with a rotating polarizer-circular analyzer system and monochromatic light, the resulting interference pattern being separated into its consitituent parts. In crystals with more than one refractive index, the speed at which light passes through the crystal depends on the direction of its path through the crystal, so light emerging from the crystal shows a phase difference, d (delta). The color key shows the orientation of the slow axis.