| 摘要 |
PURPOSE:To sense liquid over a wide range by covering even a substrate surface other than the exposed part of an optical waveguide with a coating layer. CONSTITUTION:When liquid with a larger refractive index sticks on a coating layer 13 and infiltrates into it, light capable of traveling in the optical waveguide 12 is determined not by the critical angle theta1 of the interface between the optical waveguide 12 and substrate 11, but the critical angle theta2 of the interface between the waveguide 12 and layer 13. The angle theta1, however, is larger than the angle theta2, so the rate of total reflection decreases and the quantity of propagating light also decreases, so that a liquid leak is sensed. Further, the layer 13 covers not only the exposed part 12D, but also the surface 11A connecting with the exposed part 12D. Therefore, oil sticking on the layer 13 except at the exposed part 12D infiltrates in the layer up to the exposed part 12D. Further, the waveguide 12 is branched into two branch lines 12C, so the liquid leak is sensed in a plane shape over a wide range much wider than the diameter of the waveguide 12. |
