To highly precisely detect the presence or absence of a mobile object without having any adverse influence on a general passer-by or worker on a general road or an airport road or the like.
This system is provided with an active detecting means 6 for emitting a laser beam from a laser projecting part 13 in a prescribed direction, and receiving the reflected signal of the laser beam by a laser receiving part 14 for detecting whether or not a mobile object is present as an obstacle in the emitting direction, and a passive detecting means 5 for making the active detecting means 6 perform the direction of the mobile object by the laser beam emission when it is judged that a signal level increased accompanied with the approach of the mobile object is beyond a set level by an approach judging part 9. In this case, the signal level when a person approaches does not reach the set level. Thus, even when the person approaches, the laser beam can be prevented from being emitted, and any adverse influence of the laser beam on the human body can be prevented.
ARITA SETSUO
ATSUMI JUICHIRO
