Distance measuring based on caustics.

A distance measuring technique based on caustics formed by illuminating an ellipsoid reflector with a point light source was developed. A study of the influence of the ellipticity of the mirror and the relative positions of the screen where the caustic is formed, the point source, and the mirror on the limits and accuracy of the range measured was undertaken. It was found that the accuracy in measuring a distance may be greater than the accuracy obtained by a direct measurement of the same distance by any conventional method used in measuring the diameter of the caustic on the screen.