An optical sensor for detecting the dew point of an atmosphere is disclosed for use with an optical measurement system. The optical measurement system includes a source of light energy, a light detector, and a light energy conduction arrangement for directing light energy from the source of light energy to the optical sensor. The light energy conduction arrangement also returns light energy from the optical sensor to the light detector. The optical sensor of the present invention includes a substrate located within the atmosphere and a first waveguide located on a surface of the substrate. The first waveguide includes a first end optically connected to the light energy conduction arrangement arranged to receive thereat light energy from the source of light energy and to direct thereat light energy to the light detector. A second waveguide is located on the substrate first surface parallel to and in a spaced relationship to the first waveguide. The second waveguide includes an end that is prepared as a reflecting surface. A means for cooling is attached to the substrate and is arranged to cool the optical sensor to a temperature below the ambient temperature of the atmosphere, to cause water vapor that may be contained in the atmosphere to condense and form deposits of water between the first and second waveguides. The water deposits form an evanescent region in the area of the condensate, coupling the light energy from the first waveguide to the second waveguide. The light energy entering the second waveguide is reflected off of the second waveguide's reflecting surface and is directed back to the evanescent region, where the light energy is coupled back to the first waveguide and the light energy conduction arrangement for transmission to the light detector.

Patent Information

Number	US  6084665
Country	US
Status	Issued
Date	07/04/2000