A CONJUGATE OPTICAL CONFOCAL FABRY-PEROT-INTERFEROMETER FOR ENHANCED ULTRASOUND DETECTION

To detect ultrasound remotely, an optical detection scheme is describe d which uses a confocal Fabry-Perot interferometer and conjugate detec tion. A conjugate signal is derived from the interferometer by making simultaneous use of signals derived from optical back reflection, and optical transmission, through the interferometer. Theoretical analysis and experimental results have demonstrated that the new scheme has a higher sensitivity than those described previously. Sensitivity enhanc ements between 2 and 17 times can be expected. Depending on mirror ref lectivity, the frequency response is approximately flat in the range o f 10 MHz and above, limited only by the free spectral range of the int erferometer device.