Abstract

Placido ring-based topographic measurement of the cornea is used extensively to determine the shape of this surface. The technique offers a relatively quick and accurate way of measuring the height (or curvature) of transparent optical surfaces which are typically aspheric and not rotationally symmetric. In this study, the smoothly varying, but irregularly shaped optical surface of a progressive addition lens (PAL) is measured using the Placido target concept and existing image processing and topographic reconstruction algorithms. A topographer has been built to handle the scale of the progressive lenses, and software has been written to reconstruct a surface. This research is preliminary, and meant only to examine the feasibility on implementing such a system. The measurement accuracy of the system has not been examined. The layout of the topographer is shown in Figure 1 below

© 2000 Optical Society of America