Use of moire patterns to measure defect depth on a convex spherical surface

Abstract

A simple optical system was devised, using the projection method, to produce, observe, and photograph moire patterns on a sphere approximating the size of the cornea. Measurements of moire fringe deflections were taken off the photograph and used to calculate the depth of the defect that caused the deflection. Calculation of defect depth was within .025 mm (15 percent) of depth as physically measured with a micrometer.