| 摘要 |
PURPOSE:To enhance detection sensitivity, by providing a light guide pipe on a light receiving part to prevent the incidence of external light to be measured to the cold junction part of a thermocouple. CONSTITUTION:The incident window for infrared rays being external light to be measured is provided to the upper surface part of a package and a filter 6 of a cut-on wavelength lambdac for allowing only infrared rays of a definite wavelength or more to be incident to a light receiving hot junction part 2 is mounted to said incident window. A light guide pipe 7 for preventing the incidence of the external light to be measured to a cold junction part 3 is arranged on the light receiving part 2. The light guide pipe 7 is mounted to the part of the upper inner wall surface of the package so as to surround the filter 6 and the lower edge part thereof is set so that gap (d) becoming the relation of 0<d<=lambdac is provided between said lower edge and the surface of the light receiving part 2. As mentioned above, by providing the light guide pipe 7 so as to separate the lower end edge thereof from the surface of the light receiving part 2, heat insulation is achieved and the leakage of the external light to be measured to the cold junction part 3 is prevented. By this method, the temperature difference between the hot/cold junction parts becomes large in proportion to the radiant energy of the external light and detection sensitivity is enhanced. |
