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

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 degrees over a range of +/-25 degrees 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.