Abstract: The present invention provides a hydraulic test system, by which it is possible to select a proper position and to select a reliable measurement interval corresponding to said position, to obtain information for preventing retention or leaving of the equipment in the borehole, and to observe the conditions in front and lateral directions by a single BTV at the same time and at wide angle of view without adjusting focal point. On the tip of a measurement pipe to be inserted into a borehole, a waterproofing cylinder with a transparent window oriented for simultaneously observing in both the front and lateral directions is mounted, and there are provided illumination units for illuminating in front direction and side walls and a borehole television set equipped with a ball lens, spherical mirror lens or matched convex pair of lens system in said cylinder, which forms a virtual image of an object in front direction and a reflected virtual image of an object in lateral direction on almost the same plane.

Abstract: This invention provides a three dimensional image acquisition and processing method and system that enable three dimensional viewing of an underground borehole wall. Also provided are a cylindrical straight prism and a counter cylindrical straight prism that are used in this method and system of three dimensional viewing of a borehole wall.

Abstract: A compound type cone mirror installed inside a sonde moving up and down in a borehole for observing the whole circumference of the hole wall at an arbitrary depth at a time, a combined mirror for locally observing the hole wall in detail, and an elevating sonde equipped with these mirrors are provided for observing the wall surface of a borehole In the ground. In the compound type cone mirror, a transparent truncated cone block the surface of which is finished by polishing is inserted into a concave portion or pierced hole having the same shape as said truncated cone block and formed coaxially in the axial direction in a transparent column block the surface of which is finished by polishing, and said inserting face is a mirror finished face. Moreover, in the combined mirror, a plane mirror slanted upward at 45.degree. to the axial direction is mounted onto the top face of the truncated cone block or column block of the compound type cone mirror.