| 摘要 |
Plural light emitting device groups are arranged in the direction perpendicular to the center line of a runway and each of them comprises plural light emitting devices different in light emitting angle from one another. A first controller controls said plural light emitting device groups so that light emitting devices having the same light emitting angle may emit light at the same time and light emitting devices having different light emitting angles may emit light one after another. Plural light receiving device groups are arranged, respectively, so as to correspond to the plural light emitting devices and which receive reflected light from a flying object passing a monitoring space. A second controller controls said plural light receiving device groups so that light receiving devices which receive the reflected lights corresponding to the lights emitted from said light emitting devices having the same light emitting angle as each other may be operated at the same time and light receiving devices which receive the reflected light corresponding to the lights emitted from said light emitting devices having different light emitting angles from each other may be operated one after another. A detector outputs a passing detection signal to show that said flying object has passed said monitoring space when at least one of said plural light receiving devices has received a reflected light from said flying object.
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