Infrared Sensing by Intelligent Functional Fibers

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Investigation was carried otit iii order to develop fiber materials and devises for IR sensors with intelligent functions, such as a high-speed response and stable sensing of immobile targets. In addition, feasibility for practical tise was examined with the fiber IR sensor.1. Electrical properties were measured for two kinds of carbon fibers with different raw materials and SiC fiber. The semiconducting fiber with a higher resistivity showed a larger thermistor constant, and the output voltage increased with increasing thermistor constant. A PAN (polyacrylonitrile)-based carbon fiber showed a higher thermistor constant than Pitch-based carbon and SiC fibers at a same electrical resistivity.2. IR sensing properties were examined ori sensor elements using monofiber of SiC and PAN-based carbon fibers with different diameters (7 to 130 micrometers). Response time was improved (thermal time constant was decreased) with decreasing fiber ifiameter. The otitpijt voltage increased with increasing radiation energy of IR source and with decreasing surrounding temperature.3. PAN-based carbon fiber, liaviiig a resistivity above 200 ohm. cm and a thermistor constant above 2100 K, detected an IR radiation from htimaii hand wit. 1i a steady output voltage at room temperature. PAN-based carbon fibers distinguished two kinds of lit source, whose body-temperattire was higher or lower than room temperature, by representing a positive or negative otitput. voltage, respectively.4. Stability of sensing property was improved by applying a metal plate with a large heat-capacity and a thermal insulating cover-film to a seristing cleineiit. 1--tifictioiis of recognition of IR-source position and IR-source shape were discussed on a sensor element using a long, contijitious fiber provided with many electrodes.