Page 379 - Sensors and Control Systems in Manufacturing

LED Industrial Sensors and Contr ol 333
Spectrum IF1 IF2

Luminescence
from the sensor
(at three different
temperatures)
Wavelength

FIGURE 7.4 Operating principle of optical-fi ber thermometer based on
temperature-dependent photoluminescence from a GaAs epitaxial fi lm.

FIGURE 7.5 Semiconductor
Sensing element of Sensing element
Optical fiber
an optical-fi ber
thermometer based
on temperature- Input
dependent
photoluminescence. Output

GaAs
AlxGai–xAs
Energy

E g

Sensor

GRIN-
lens IF1 IF2

Photodiode 1
Photodiode 2

Glass block

LED
FIGURE 7.6 Optical system of an optical-fi ber thermometer based on
temperature-dependent photoluminescence.