Abstract: A penetrant apparatus for controlling the depth that a penetrant device penetrates a material relative to its outer surface, where the cross-sectional thickness of the material is not susceptible to caliper-type measurement because its inner surface is inaccessible except by intrusive means, and a method for penetrating the material utilizing the apparatus. The apparatus comprises a penetrant device connected to and driven by driving apparatus, depth sensing apparatus, thickness sensing apparatus, and comparator apparatus. The depth sensing apparatus determines the depth of penetration of the penetrant device into the material while the thickness sensing apparatus determines the thickness of the material between its inner and outer surfaces.

Abstract: A lens system for variable refraction comprising a solid housing having a single internal chamber completely filled with a plurality of imiscible liquids of preselected densities and refractive indices. The chamber is of a form such that the amount and distribution of each liquid in the optical portion of the system is altered when the system is tilted, producing a change in refractive power. The system may be incorporated into spectacle lenses or contact lenses to provide a continuous spectrum of refractive power, or into contact lenses to provide bifocal capability.