Calculation for correction in the measurement of the optic axial angle with the universal stage.

Abstract

Because of the difference in index between crystal and hemisphere, corrections for rotations must be made in measuring the optic axial angle with the universal stage. The conventional methods require to use correction diagrams for the inclination angle and to evaluate the corrected value of the optic axial angle graphically by means of stereographic projection. Such graphical procedures, however, are troublesome and time-consuming as well as lower in accuracy, and many workers wish to make the collection more conveniently. The present author recommends the correction of the optic axial angle by calculation when the points of emergence of both optic axes can be determined directly with the five-axes universal stage. The method proposed here is of a mathematical treatment of the Emmons' graphical method and remarkably facilitates the procedure for correction by using a computer. It is also applicable to the correction in the measurement of the optic axial angle with the four-axes universal stage. Programs in the BASIC language are exemplified for both the five- and fouraxes universal stages.