| 摘要 |
<p>An ultrasonic sensor comprising a polarisation maintaining fibre (4) having two orthogonal linear principal axes and a straight sensing portion (5). A laser source (1) directs a beam through a quarter wave plate (2) to provide a circularly polarised beam to the input end (3) of the fibre. The beam emerging from the output end (8) of the fibre (4) is directed to a linear polariser (9) and the intensity of the beam is detected by a photodetector (10). A signal processor (11) thereafter generates a suitable driving signal for a display unit (12) indicative of mode coupling induced in fibre (4) by incident ultrasonic waves.</p> |
