| 摘要 |
PROBLEM TO BE SOLVED: To obtain a liquid-level detector by which a liquid level is detected with high sensitivity by arranging optical elements which have a condensing function at tip parts of optical fibers, for light-projecting and -receiving, which are installed side by side. SOLUTION: Optical elements 4, 5 of cylindrical lenses are installed at tip parts of optical fibers 1, 2, for light-projecting and -receiving, which are held by a holding member 3 and which are installed side by side, both optical fibers and the member 3 are housed in a space 6a at a protective member 6, and a conical prism 6b is formed at the tip part. At a lower level at which a liquid level 7 does not come into contact with the prism 6b, radiant light A from the fiber 1 is condensed in one point of the prism 6b, and its reflected light B is incident on the fiber 2 so as to be detected. On the other hand, at a higher level at which the level 7 comes into contact with the prism 6b, parts A1 , A2 of the radiant light A are transmitted through the prism 6b, and a quantity of light which is incident on the fiber 2 is lowered. Consequently, when a drop in the quantity of light is detected, whether the level 7 is in a prescribed position or not is detected. At this time, the overlap of a light-projecting spot S1 and a light-receiving spot S2 is eliminated in order to condense the radiant light A on the prism 6b, a malfunction is prevented, and the liquid level can be detected with high sensitivity. |
