METHOD AND DEVICE FOR DETECTING LIQUID LAYER THICKNESS

To provide a method and device for non-contactly detecting the thickness of a liquid layer covering a substrate such as spring water on a pit face.SOLUTION: The present invention irradiates a plurality of lights R, B having different wavelengths λr, λb from the surface of a liquid layer (for example, spring water) 10 covering a substrate (for example, pit face) 2 toward the substrate 2 on the back surface, to detect the difference (tr-tb) between reflection times tr, tb of the lights R, B of the respective wavelengths from the substrate 2, and then measures a thickness of the liquid layer 10 based on the reflection time difference (tr-tb) of the lights R, B of the respective wavelengths and refractive indexes nr, nb of the lights R, B of the respective wavelengths in the liquid layer 10. The present invention may measure the thickness of the liquid layer 10 based on a reflection phase delay difference (φr-φb) of the lights R, B of the respective wavelengths or a displacement difference (Xr-Xb) of a reflection light receiving position, instead of the reflection time difference (tr-tb).SELECTED DRAWING: Figure 1 【課題】切羽上の湧水のように基盤を覆う液層の厚さを非接触で検出する方法及び装置を提供する。【解決手段】基盤（例えば切羽）２を覆う液層（例えば湧水）１０の表面から背面の基盤２に向けて波長λｒ，λｂの異なる複数の光Ｒ，Ｂを照射して各波長の光Ｒ，Ｂの基盤２からの反射時間ｔｒ，ｔｂの差（ｔｒ－ｔｂ）を検知し，各波長の光Ｒ，Ｂの反射時間差（ｔｒ－ｔｂ）と各波長の光Ｒ，Ｂの液層１０中の屈折率ｎｒ，ｎｂとに基づいて液層１０の厚さを測定する。反射時間差（ｔｒ－ｔｂ）に代えて，各波長の光Ｒ，Ｂの反射位相遅延差（φｒ－φｂ）或いは反射受光位置の変位差（Ｘｒ－Ｘｂ）に基づいて液層１０の厚さを測定してもよい。【選択図】 図１