| 摘要 |
PROBLEM TO BE SOLVED: To easily specify a generation point of falling-in in a narrow range, in a measuring range of the falling-in in a wide sloped face by a falling-in detecting system. SOLUTION: A plurality of mirror reflectors MR1-MR5 combined with a plane reflecting mirror R and a recursion reflecting mirror Q is set in the sloped face of a mountain to make a laser beam transmitted from a laser beam source 1s reflected after going round the plurality of mirror reflectors, and received by a photoreceiver 1rr, so as to measure a time till receiving a recursion reflection beam of the laser beam transmitted from the laser beam source 1s. When no reflection signal from the recursion reflecting mirrors Q is able to be received, the falling-in is determined to be generated at least in a set position of the mirror reflector MR attached with the recursion mirror corresponding to the the shortest reflection time. COPYRIGHT: (C)2005,JPO&NCIPI
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