| 摘要 |
PROBLEM TO BE SOLVED: To control the temperature of the contact surface with a subject to a prescribed value or lower without mounting a temperature sensor or without setting the ultrasonic output excessively low. SOLUTION: The reflection time t1 of ultrasonic waves, passing an oil 6, reflected on the inner face of a window 5 and returning via the oil, and the reflection time t2 of ultrasonic waves passing the window, reflected on the outer surface of the window and returning via the window and the oil, are detected. Then, the acoustic velocity of the window, expressed by formula (thickness of the window×2)/(t2-t1), is measured, and the surface temperature of the window is detected on the basis of the measured acoustic velocity. COPYRIGHT: (C)2005,JPO&NCIPI
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