| 摘要 |
PURPOSE:To detect the state of dew condensation surely by preventing errors owing to fluctuations in a light source and a photodetector by such constitution wherein the light transmitted through an object to be inspected is kept cut on the optical axis during normal time and the output of the photodetector is obtained by the scattered light of dew condensation when dew condenses. CONSTITUTION:Light is irradiated to the surface of a transmittable object to be inspected, for example, window glass 12, from a spot light source constituted of a light source 10 and a pinhole 11, and the light transmitted through the same is kept shut off with a mask 13 at all times, so that the output of a photodetector 14 is kept zero. When dew condenses on the glass 12, the light scattered by the dew is detected with the photodetector 14, and the state of dew condensation is measured with a measuring device 15. Since the output of the photodetector 14 is kept zero in the non-condensation state, errors owing to the level fluctuations of the light source, etc. are prevented and the dew condensation state is detected surely. |
