Color Contrast from Birefringent Arrays of Edge Dislocations Using a Full-Wave Plate*

Color contrast between regions of opposite retardation, such as the two sides of an array of edge dislocations, is possible only for orientations of the tint plate for which the violet intensity from the advanced regions and the red intensity from the retarded regions are greater than their opposite colors and vice versa. The effect of retardation on the orientation range is described and it is shown that the orientation for optimum color contrast in low retardation specimens corresponds to a rather low intensity (<0.01) and varies linearly with retardation.