Multipoint heterodyne vibrometry for measurements on unstable biomedical objects
Joris Dirckx, H.J. van Elburg, Willem F. S. Decraemer · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2005
In unstable objects, such as biological specimens, vibrational patterns can change quickly with time. To determine phase relationships between several vibrating points in such an object, it is therefore necessary to measure those points simultaneously. We describe a dual channel heterodyne interferometer capable to acquire vibrational data at two arbitrary spatial points simultaneouly over the entire acoustic frequency range. The design allows extension to four or even eight independent channels. Channel cross-talk is measured to be about -30 dB, below the S/N ratio within the signal channel. Velocity resolution is estimated to be 10 μm/s, corresponding to an amplitude resolution of 1.5 nm at 1 kHz.