Abstract
This paper is related to an optical measurement as a means of noncontact detection of a certain phenomenon observed in a birefringence change.
Here the matter of great concern is whether or not the measurement is eventually practical for use under given conditions.
The example presented here is the case of detecting a nerve excitation through a very small and relatively rapid change in phase-difference, say 10-5 rad in a few milliseconds, occurring in the small area of a nerve membrane during its activity.
First, an equation was derived to give a limiting condition among such parameters as the size of phase-difference, the bandwidth, the number of iterations and the output level of photodiode.
Then, measurements were carried out on a crab nerve through the polarizing microscope. And, an investigation was made on the dependence of signal detectability on the area under measurement.
