Ultrasonic sensor using a polarization maintaining fibre
First Claim
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1. An apparatus for use in an ultrasonic sensor comprising:
- a polarisation maintaining fibre for being disposed in the path of an ultrasonic wave, the fibre having two orthogonal principal axes, an input end, and an output end;
input means to launch into the input end of the fibre a light beam aligned with at least one of the principal axes; and
output means for receiving the light beam from the output end of the fibre and for determining mode coupling induced in the fibre by the ultrasonic wave and thereby provide a first signal indicative of the magnitude of the ultrasonic wave.
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Abstract
An ultrasonic sensor having a polarization maintaining fibre including two orthogonal linear principal axes and a straight sensing portion. A laser source directs a beam through a quarter wave plate to provide a circularly polarized beam to an input end of the fibre. The beam emerging from an output end of the fibre is directed to a linear polarizer and the intensity of the beam is detected by a photodetector. A signal processor thereafter generates suitable driving signals for a display unit indicative of mode coupling induced in the fibre by incident ultrasonic waves.
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11 Claims
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1. An apparatus for use in an ultrasonic sensor comprising:
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a polarisation maintaining fibre for being disposed in the path of an ultrasonic wave, the fibre having two orthogonal principal axes, an input end, and an output end; input means to launch into the input end of the fibre a light beam aligned with at least one of the principal axes; and output means for receiving the light beam from the output end of the fibre and for determining mode coupling induced in the fibre by the ultrasonic wave and thereby provide a first signal indicative of the magnitude of the ultrasonic wave. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification