| 摘要 |
PROBLEM TO BE SOLVED: To provide a three-lens range finder in which erroneous detection of distance due to the finite diameter of a spot light projected from a projecting means is prevented. SOLUTION: A light projection element 11 projects a spot light into a space being monitored. A projected light spot formed on an object 3 by the spot light produces a receiving light spot on a light receiving element 21a, 21b through a light receiving optical system 22a, 22b. A signal processing circuit 23a, 23b corresponding to the light receiving element 21a, 21b produces an active output when a decision is made that the object 3 exists within a specified distance range based on the position of the receiving light spot on the light receiving element 21a, 21b. When both circuits 23a, 23b produce active outputs, an AND circuit 24 produces an active output thus determining presence of the object 3 within a specified distance range.
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