FLOW RATE DETECTION DEVICE AND FLOW RATE DETECTION METHOD

To provide a flow detecting device and a flow rate detecting method having robustness for positioning light projecting means even when detecting the number of rotations of a rotating body rotating on a plane according to the flow of a fluid.SOLUTION: It is a flow rate detecting device 1 that solves the above problem and detects the number of rotations of a rotating body 11 that rotates on a plane according to the flow of fluid. The flow rate detecting device 1 includes: a light projecting unit 3 that emits parallel light toward the rotating body 11; a light receiving unit 4 that detects changes in an optical path in parallel light reflected by the rotating body 11; an optical path changing unit 5 that is arranged between the light projecting unit 3 and the rotating body 11, and refracts the parallel light so that the incident angle with respect to the plane is a positive angle smaller than 90 degrees while making the light receiving unit 4 to receive the reflected parallel light.SELECTED DRAWING: Figure 1 【課題】流体の流れに応じて平面上で回転する回転体の回転数を検出する場合でも、投光手段の位置合わせについてロバスト性を有する流量検出装置及び流量検出方法を提供する。【解決手段】上記課題を解決するため、流体の流れに応じて平面上で回転する回転体１１の回転数を検出する流量検出装置１であって、上記回転体１１へ向けて平行光を発する投光部３と、回転体１１で反射された平行光における光路の変化を検知する受光部４と、投光部３と回転体１１との間に配置され、上記平面に対する入射角が９０度より小さな正の角度となるよう上記平行光を屈折させると共に、上記反射された平行光を受光部４へ受光させる光路変更部５とを備えた流量検出装置１を提供する。【選択図】図１