| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a water content sensor capable of widening a measurement range. SOLUTION: The water content sensor comprises a transmission hologram 5 which allows a light from a light source (LED) 7 to combine with a light-guide layer 1 while a light from the light-guide layer 1 to split, and a detector 9 which detects the split light. In the light-guide layer 1, the light is totally reflected on a border surface 11 if an ambient medium contains a water content by less than a threshold value while it is not totally reflected if the water content of the medium exceeds the threshold value. A reflection hologram 3 is provided in a part of the region on the light-guide layer 1. The reflection hologram 3 reproduces a light beam advancing in the direction almost opposite to an incident light beam 17 when a light beam 15 enters the light-guide layer 1 at a propagation angleα. A windowpane, especially windshields of an aircraft and automobile, is used as the light-guide layer.</p> |
