Abstract

In the well-known light-section (Schmaltz) technique, a thin light beam is projected onto a surface at a 45° angle, and height variations are manifested as deviations from straightness of the intersection of the beam and the surface. This technique has become quite important in machine vision, since it is amenable to computer analysis. In the finest measurements, a slit is imaged onto the surface and the laws of resolution and depth of focus come into play. The height resolution of the technique is related to the narrowness of the slit image and thus to the resolving power of the slit projector. The height range is related to the depth of focus of the slit projector. Since depth of focus decreases with resolving power, height range and height resolution are opposed. Expressions showing the trade-offs are given, which depend on the numerical aperture and the angle of the apparatus. Another parameter of interest is the number of resolvable heights.

© 1985 Optical Society of America