Bioquartz:
Instead of a half shade plate, a bioquartz plate is also used in polarimeters. It consists of two semi-circular plates of quartz each of thickness 3.75 mm. One half consists of right-handed optically active quartz, while the other is left-handed optically active quartz. If white light is used, yellow light is quenched by the bioquartz plate and both the halves will have the tint of passage. This can be adjusted by rotating the analyzer N2 to a particular position. When the analyzer is rotated to one side from this position, one-half of the field of view appears blue, while the other half appears red. If the analyzer is rotated in the opposite direction the first half which was blue earlier appears red and the second half which was red earlier appears blue. Therefore, by adjusting the particular position of the analyzer, the field of view appears equally bright with tint of passage.