Measurement of rabbit eardrum vibration through stroboscopic digital holography

Journal Article · Tue May 27 00:00:00 EDT 2014 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.4879598· OSTI ID:22311321

De Greef, Daniël; Dirckx, Joris J. J. ^[1]

---

1. University of Antwerp, Laboratory of BioMedical Physics, Groenenborgerlaan 171, B-2020 Antwerp (Belgium)

In this work, we present a setup for high-power single shot stroboscopic digital holography and demonstrate it in an application on rabbit eardrum vibration measurement. The setup is able to make full-field time-resolved measurements of vibrating surfaces with a precision in the nanometer range in a broad frequency range. The height displacement of the measured object is visualized over the entire surface as a function of time. Vibration magnitude and phase maps can be extracted from these data, the latter proving to be very useful to reveal phase delays across the surface. Such deviations from modal motion indicate energy losses due to internal damping, in contrast to purely elastic mechanics. This is of great interest in middle ear mechanics and finite element modelling. In our setup, short laser pulses are fired at selected instants within the surface vibration period and are recorded by a CCD camera. The timing of the pulses and the exposure of the camera are synchronized to the vibration phase by a microprocessor. The high-power frequency-doubled Nd:YAG laser produces pulses containing up to 5 mJ of energy, which is amply sufficient to record single-shot holograms. As the laser pulse length is 8 ns and the smallest time step of the trigger electronics is 1 μs, vibration measurements of frequencies up to 250 kHz are achievable through this method, provided that the maximum vibration amplitude exceeds a few nanometers. In our application, middle ear mechanics, measuring frequencies extend from 5 Hz to 20 kHz. The experimental setup will be presented, as well as results of measurements on a stretched circular rubber membrane and a rabbit's eardrum. Two of the challenges when measuring biological tissues, such as the eardrum, are low reflectivity and fast dehydration. To increase reflectivity, a coating is applied and to counteract the undesirable effects of tissue dehydration, the measurement setup and software have been optimized for speed without compromising on the quality. Results of a repeatability test will be presented as well. Since the method measures the membrane motion as a function of time in small time steps, we do not only measure vibration amplitude like in time-average holography, but we can also measure non-linear elastic and transient behaviour. In conclusion, the combination of good spatial, depth and time resolution with the fast data acquisition and very wide frequency range make our technique applicable in a number of fields, including biological tissue vibrations.

• OSTI ID: 22311321
• Journal Information: AIP Conference Proceedings, Vol. 1600, Issue 1; Conference: AIVELA 2014: 11. international conference on vibration measurements by laser and noncontact techniques, Ancona (Italy), 25-27 Jun 2014; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANIMAL TISSUES
AUDITORY ORGANS
CAMERAS
CHARGE-COUPLED DEVICES
DATA ACQUISITION
ENERGY LOSSES
HOLOGRAPHY
KHZ RANGE
MECHANICAL VIBRATIONS
MEMBRANES
MICROPROCESSORS
NEODYMIUM LASERS
NONLINEAR PROBLEMS
PULSES
RABBITS
REFLECTIVITY
TIME DEPENDENCE
TIME RESOLUTION