Hitachi, Ltd.

Yasuo Minai

Minoru Maeda

Seiichi Onoda

Mitsuo Tanaka

Shoji Yamada

Shin Kita

An optical measurement system for eliminating the influences of time variations on light sources, transmission lines, photo detectors, etc. The system includes light sources which generate two pulse-shaped optical signals of different light wavelengths with a portion of the optical signals being transmitted to a measuring part in a distant place by a transmission line. In the measuring part, a change of a measured object is converted into a variation in the quantity of transmission of light, and the optical signal subjected to the variation is transmitted to a signal processing portion by a transmission line. The varied optical signal is converted into a first electric signal by a photo detector. Another portion of the optical signals from the light sources is converted into a second electric signal by another photo detector. A signal processing circuit provides a measurement output indicative of the quantity of change of the measured object as a function of at least one ratio of the first and second electric signals.

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Hinode-machi, Japan

Yasuo Minai