METHOD OF AND APPARATUS FOR THE INVESTIGATION OF INACCESSIBLE SUBTERRANEAN SPACES SUCH AS BOREHOLES

摘要

ABSTRACT OF THE DISCLOSUREA method of and an apparatus for investigatingsubterranean boreholes especially in bituminous coalmining. Optical fiber cables carry light for illuminatingthe hole into the latter and an image of the wall of theborehole from the latter to an evaluating means externalof the borehole.