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U.S.
Patent No. 6,496,268, Dec. 17, 2002, Laser-Based Glass
Thickness Measurement System and Method, A. D. W.
McKie, M. B. Klein, B. Pouet, and F. J. Shih, inventors.
Laser-Based
Glass Thickness Measurement System and Method
ABSTRACT
A
laser-based technique to determine glass thickness
employs a pulsed laser to induce an ultrasonic wave
between the surfaces of a region of glass, causing
the surfaces to move in and out at a characteristic
frequency. The surface motion is monitored to determine
the characteristic frequency, which is proportional
to the thickness of the glass in the region of the
ultrasonic wave. The pulsed laser produces a short
duration pulse that illuminates a surface of the glass,
which is absorbed within the glass to cause a rapid
thermal expansion that generates the ultrasonic wave.
The surface motion induced by the ultrasonic wave
is preferably detected with a laser interferometer
system, the output of which is analyzed to determine
the surface motion's characteristic frequency.
(Full
detail at USPTO database)
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