PROBLEM TO BE SOLVED: To enhance detection sensitivity of dew point by projecting light into an optical waveguide core layer to cause multiple reflection and measuring optical scattering characteristics caused by a dew adhering to the surface of the optical waveguide core layer. SOLUTION: The dew point measuring apparatus comprises an optical waveguide core layer 11, a substrate 12, a cooler 18 and a precise thermometer 19. When multiple reflection takes place in the optical waveguide core layer 11, evanescent light is generated in the vicinity of a pole on the order of wavelength of light on the surface 14 of the optical waveguide core layer 11. When a dew 16 is present on the surface 14 of the optical waveguide core layer 11, the evanescent light is scattered to the outside of the optical waveguide core layer and the incident light is weakened to decrease the intensity of outgoing light. When the surface 14 of the optical waveguide core layer 11 is cooled gradually while blowing a sample gas, intensity of outgoing light from the surface 14 of the optical waveguide core layer 11 is decreased at a moment of time when a dew 16 begins to be formed. Dew point can be determined by measuring the temperature on the surface 14 of the optical waveguide core layer 11 at a moment of time when the intensity of outgoing light is decreased.

Title
Method for measuring dew point and apparatus for measuring dew point utilizing slab optical waveguide
Application Number
09-291912
Publication Number
1998-082738
Application Date
October 24, 1997
Publication Date
March 31, 1998
Inventor
Matsuda Naoki
Monno Akiko
Kato Kenji
Assignee
Agency Of Ind Science &Amp Technol
IPC
G01N 21/47