Method of and apparatus for optically detecting anomalous subsurface structure in translucent articles

An apparatus for detecting and determining the presence and relative degree of anomalous subsurface structure in a solid translucent article, said apparatus comprising:

• means for illuminating a surface area of said article with a beam of incident light of predetermined intensity;
• means for detecting and quantifying the intensity of a portion of said light which is being internally diverted and emerging outwardly from subjacent said surface area of said article;
• means for inferring from said intensity of said internally diverted light the relative degree of subsurface anomalous structure subjacent said illuminated area through the use of an empirical relation between such intensity and the relative degree of subsurface anomalous structure which relation has been derived by making corresponding intensity determinations on a plurality of graded standards covering a predetermined range of degrees of anomalous subsurface structure;
• and,
• means for imposing a shadow pattern image on said beam of incident light and for focusing said image on said surface area to provide at least one directly illuminated portion of said surface area and at least one shaded portion of said surface area, and wherein said means for detecting and quantifying comprises optical viewing means for viewing said surface area and means for scanning said surface area along a scan line which extends across at least one said directly illuminated portion of said surface area and at least one said shaded portion of said surface area, said means for detecting and quantifying further comprising computing means for determining the intensity difference between outwardly directed internally diverted light emerging from said article along the portion of said scan line extending across said directly illuminated portion and the outwardly directed internally diverted light emerging from said article along the portion of said scan line extending across said shaded portion and means for comparing said intensity difference with said empirical relation whereby the relative degree of anomalous subsurface structure in the article can be inferred.

An optical probe for use in an optical instrumentation system comprising a remote light source, a flexible fiber optic cable for transmitting light from said source to said probe, a closed circuit video sub-system, and a flexible coherent fiber optic cable for conducting an image from said probe to said closed circuit video sub-system, said probe comprising means for being coupled to said fiber optic cables, means for projecting an image-carrying incident light beam from said probe and for focusing said beam to form said image on a solid surface of interest, and means for focusing light received from the direction of said surface of interest on the end of the flexible coherent fiber optic cable coupled to said probe whereby said video sub-system can view said surface of interest, and enlarge and remotely display a video image of said view of said surface of interest, said means for focusing said incident light beam comprising means for providing a fixed focal length for said beam so that said image is focused in an image plane, and means for spacing said probe so that said surface of interest is substantially coincident with said image plane, and said means for spacing comprises a resilient member disposed on the projection end of said probe which member has a length greater than the distance between the projection end of the probe and said image plane whereby said projection end of said probe can be pressed against said surface of interest to sufficiently deform said resilient member to cause said surface of interest and said image plane to be substantially coextensive.