The Thermopile for an Infra-red Spectrometer and its Application to a Vacuum Gauge

(1) The thermopiles have been constructed by depositing Bi-Te and Bi-Sb on thin colodion films by vacuum evaporation. (2) Thermoelectromotive force of the Bi-Te junction was measured as 450μV/℃ while that of the Bi-Sb, 120μV/℃. (3) Owing to the small heat capacity, the thermopiles were found to produce an oscillating thermoelectric power by the irradiation of the chopped infra-red ray. (4) The time constant was measured by observing the oscillating thermoelectric power in various chopping frequencies, and was given as 3/100 sec. (5) By evacuating the tube of the junction, the saturated thermoelectric power increased about 20 times. (6) The time constant also increased with equal proportion except a small discrepancy in high chopping frequency. (7) The change of characteristics due to the blackening was investigated. (8) Using the Bi-Sb junction, a convenient vacuum gauge has been constructed. In conclusion, the writers wish to their sincere appreciation to Dr. J. Okubo, the ex-superintendent professor of this institute, for his kind interest through the whole course of this work

Test of an Optical Flat by the Fabry Perot Etalon

To test the flatness of an optical fiat, a simple optical system, combined with the Fabry Perot etalon, has been [1evise[1, which affords sharp contour lines of elevation (or depression) in the image of the flat. When the fiat to be tested is held oblique to that to be referred, the elevation is indicated by the deviation of contour lines which are to be straight, parallel and equidistant if the flat is perfect, Analyzing the contour lines, the flatness has been measured with the accuracy of 1/200λ When the flats are held in parallel, only one contour line appears and in order to displace the line, the pressure of air in the etalon has been varied. In this case, the flatness can be surveyed without any analysis. This optical system is available to measure a minute displacement or a small change of an angle. In conclusion, the writers wish to express their best thanks to Dr. J. Okubo, ex-super-intendent professor of this institute, for his continued interest and encouragement in this work