PURPOSE: To take a measurement in a short time by providing a prism where light from a light source is made incident and light diffracted spectrally by the contacting surface of liquid to be measured is guided out and a photodetector which detects and converts said spectrally diffracted light into an electric signal.
CONSTITUTION: The light emitted by the light source 1 is guided in by an optical fiber 2A and entered into the prism 3. The incident light travels toward the liquid contacting surface of the prism 3 and split by the contacting surface into light which is transmitted toward the liquid as an isotropic medium, i.e. refracted light and reflected light. The quantity of the light diffracted spectrally by the liquid contacting surface of the prism 3, on the other hand, varies with the refractive index of the liquid in constant correlation with the liquid medium. Namely, the quantity of the reflected light which is reduced by said quantity of transmitted light from the incident light is in constant correlation with the refractive index of the liquid. For the purpose, the output signal of the light source 1 and the output signal of the photodetector 4 are inputted to a processor 6 and the ratio of both signals is computed to know the refractive index of the liquid.
TAKAHASHI KATSUNORI
SHINODA TAKASHI
SHIMIZU MOTOO
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