Optical Methods of Measuring the Birefringence of Muscle Fibers

摘要

An optical method has been developed to measure the birefringence of muscle fibers using an automated Linnik interference microscope with a laser light source. This method has a number of advantages over the previously used methods based on measurement of the intensity of the light that has passed through crossed polarizer,analyzer, and fiber (polarization microscopy). The method proposed involves direct phase measurements of the optical path length at the parallel and perpendicular orientations of the polarization plane of the probing radiation. Interference patterns are automatically interpreted by the phase-step method. Phase images of the same central region of the fiber at different orientations of the polarization plane of the probing radiation are reproduced as two-dimensional digital maps of the optical path length. Subtractive superposition of these two images yields a two-dimensional map of the phase difference which contains information on the fiber birefringence. An expression for the birefringence has been derived; this expression differs from those used before by the fact that it involves no unknown fiber thickness, which depends on the measurement point. The birefringence is normalized to the half-sum of the phases, which are measured separated during the experiment.