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Dissertation
Development of a fiberoptic ultrasonic sensor using light diffraction technique
Doctor of Philosophy (Ph.D.), Drexel University
Sep 1993
DOI:
https://doi.org/10.17918/00004039
Abstract
Precise ultrasonic field measurements are desirable to determine the acoustic output of medical ultrasonic equipments, and study potential bioeffects caused by ultrasound, etc. A PVDF hydrophone, which is the most commonly used device to measure the characteristics of ultrasonic fields, suffers from a number of drawbacks. It perturbs the field distribution and leads to spatial averaging effects due to its finite aperture. In addition, it is very delicate and susceptible to damage. The goals of this research were to develop a fiberoptic ultrasonic sensor to overcome these problems, and to evaluate its potential capability in biomedical applications. The probe developed is based on the mechanism of acoustooptic interaction. An optical fiber acts as an extrinsic sensor to carry a coherent light beam into the ultrasonic field and another optical fiber collects the diffracted beams. A photodetector is used to measure the optical signal. By analyzing this signal, both the amplitude and the frequency information of the acoustic field can be retrieved. Initial efforts have been focused on the choices of the individual components, the implementation of the fiberoptic ultrasonic sensor, and the optimization of the experimental setup. A series of experiments have been conducted using the fiberoptic ultrasonic sensor and a calibrated PVDF needle hydrophone to evaluate the sensor's performance in terms of its sensitivity, linearity, frequency response, as well as the temporal and spatial responses to the focused and unfocused transducers with resonant frequencies from 2.25 to 20 MHz. Experimental results presented clearly demonstrate the sensor's ability in measuring the temporal responses and beam profiles of a variety of transducers and its applicability in high frequency and high intensity measurements. No other probe currently available is able to measure the high frequency ultrasound, in a simple fashion, without affecting the field distribution. In addition, the developed sensor is immune to electromagnetic interference and can withstand hazardous environment. It has immediate applications in biomedical and industrial areas. The work presented in this thesis is part of a major effort toward the ultimate goal of designing a fiberoptic ultrasonic sensor that can characterize the ultrasonic field in vivo.
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Details
- Title
- Development of a fiberoptic ultrasonic sensor using light diffraction technique
- Creators
- Yunqiu Wu
- Contributors
- Peter Andreas Lewin (Advisor) - Drexel University, Drexel University (1970-)P. Mohana Shankar (Advisor) - Drexel University, Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xv, 103 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Drexel University
- Other Identifier
- 991021889056904721