| 摘要 |
PCT No. PCT/GB96/00450 Sec. 371 Date Sep. 3, 1997 Sec. 102(e) Date Sep. 3, 1997 PCT Filed Feb. 29, 1996 PCT Pub. No. WO96/28001 PCT Pub. Date Sep. 12, 1996A passive acousto-optic modulator for the modulation of a light beam as a function of a variation in air pressure comprising a beam splitter arranged relative to the beam so as to produce a signal beam and reference beam, the beam splitter ideally comprising a flat interface located between two optically transparent mediums such as the end of an optic fiber located within air, the interface being arranged relative to the light modulator such that when the light beam travels through the interface, some of the light beam is able to pass through the interface to form the signal beam, the rest of the light beam being reflected back off the interface to form the reflected reference beam; a light modulator which modulates the signal beam, the light modulator comprising an approximately flat optically reflective surface capable of movement, the reflective surface being located in a position which, at rest is a predetermined distance from the beam splitter and is approximately parallel to and facing the beam splitter and a piezoelectric element, the piezoelectric element being connected to the reflective surface in such a way that when an electric potential is applied across the piezoelectric element, it causes the reflective surface to move; and conversion means to convert variations in air pressure into corresponding variations in a signal for driving the light modulator; the arrangement being such that the modulated signal beam is combined with the reference beam to produce constructive or destructive interference. |
