Compensator transducer increases ease, accuracy, and rapidity of measuring changes in specimen birefringence with polarization microscopy

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Abstract
An instrument has been designed to improve substantially the efficiency and convenience of measuring specimen birefringence retardation (BR) with a conventional Brace-Köhler compensator. The design is based on the precise transduction of the angular position of the compensator's vernier dial to an easily visible red-illuminated display on a digital voltmeter. The instrument display is accurate to within 0.1° over a range of ± 25° in the compensator vernier dial position which is similar to the precision obtainable with an ordinary vernier and the Brace-Köhler method of measuring BR of biological specimens. For convenience in data reduction the display can also be read directly in nanometre units, with a similar precision for specimen BR in the range of 5 nm or less which is typical of birefringent fine structures in living cells.