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Proceedings Paper

Single Fiber Shutter Type Sensor Using A Self Detecting LED
Author(s): Mark Johnson
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Paper Abstract

A reflective encoder disc is illuminated by the light from a continuously forward biased light emitting diode (LED). As the disk rotates so the level of light coupled back into the LED itself is modulated. By monitoring the LED terminal voltage, the modulation, and hence the motion of the disc itself may be detected. Measurements of optical detection sensitivity in forward biased LEDs and also in silicon photodiodes are presented to illustrate the competing photo-and thermal-detection effects. At low bias currents incident light and voltage change are in phase. at high currents in antiphase. A fiber-connected self-detecting opto-coupler and tachometer based on these effects is described with a signal to noise ratio of 56dB in 10kHz bandwidth.

Paper Details

Date Published: 23 February 1989
PDF: 5 pages
Proc. SPIE 1011, Fiber Optic Sensors III, (23 February 1989); doi: 10.1117/12.949299
Show Author Affiliations
Mark Johnson, York Harburg Sensor GmbH (Germany)

Published in SPIE Proceedings Vol. 1011:
Fiber Optic Sensors III
Ralf Th. Kersten, Editor(s)

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