| 摘要 |
PURPOSE:To make it possible to always efficiently detect the flowing direction of gas, by providing a light path change-over mirror to work interlocking with a wind direction detector and making it possible to deflect laser beam to plural light paths by a wind direction. CONSTITUTION:Laser beam transmitting receiving apparatuses 21, 22, changeover mirrors 23, 24, retroreflectors 25-28 and a wind direction detector 29 are provided to two apexes of a triangle with respect to an area region 20 to be detected. The gas flowing to a wind direction from a generation source is detected by the wind direction detector 29 and the directions of the change-over mirrors 25-28 are rapidly controlled by the detection signal while laser beam is pro jected to a direction flowing the gas by the wind direction to make it possible to detect gas with high certainly. |
