Abstract: The reflected light from the inner surface of the posterior side will interfere with the incidence light,when the white light irradiate to the mica plate.A fluted spectrum with different colors can be observed by using spectrometer.Changing the polarization direction of incident light,the difference of index at orthogonal optical axis of the mica plate can be rapidly determined upon the moving direction of the grooves since the birefringence,and then the fast and slow axis can be deduced.

Key words: mica plate, polarized light, spectrometer, fast and slow axis