Lewin P A, Mu C, Umchid S, Daryoush A, El-Sherif M
School of Biomedical Engineering Science and Health Systems and Department of Electrical and Computer Engineering, Drexel University, Philadelphia, PA 19014, USA.
Ultrasonics. 2005 Dec;43(10):815-21. doi: 10.1016/j.ultras.2005.05.003. Epub 2005 Jul 5.
This work describes the results of initial evaluation of a wideband acousto-optic hydrophone probe designed to operate as point receiver in the frequency range up to 100 MHz. The hydrophone was implemented as a tapered fiber optic (FO) probe sensor with a tip diameter of approximately 7 microm. Such small physical dimensions of the sensor eliminate the need for spatial averaging corrections so that true pressure-time (p-t) waveforms can be faithfully recorded. The theoretical considerations that predicted the FO probe sensitivity to be equal to 4.3 mV/MPa are presented along with a brief description of the manufacturing process. The calibration results that verified the theoretically predicted sensitivity are also presented along with a brief description of the improvements being currently implemented to increase this sensitivity level by approximately 20 dB. The results of preliminary measurements indicate that the fiber optic probes will exhibit a uniform frequency response and a zero phase shift in the frequency range considered. These features might be very useful in rapid complex calibration i.e. determining both magnitude and phase response of other hydrophones by the substitution method. Also, because of their robust design and linearity, these fiber optic hydrophones could also meet the challenges posed by high intensity focused ultrasound (HIFU) and other therapeutic applications. Overall, the outcome of this work shows that when fully developed, the FO probes will be well suited for high frequency measurements of ultrasound fields and will be able to complement the data collected by the current finite aperture piezoelectric PVDF hydrophones.
这项工作描述了一种宽带声光水听器探头的初步评估结果，该探头设计用于在高达100 MHz的频率范围内作为点接收器运行。该水听器被实现为一种锥形光纤（FO）探头传感器，尖端直径约为7微米。传感器如此小的物理尺寸消除了空间平均校正的需要，从而可以忠实地记录真实的压力-时间（p-t）波形。给出了预测FO探头灵敏度等于4.3 mV/MPa的理论考量，并简要描述了制造过程。还给出了验证理论预测灵敏度的校准结果，以及目前正在实施的将该灵敏度水平提高约20 dB的改进措施的简要描述。初步测量结果表明，光纤探头在考虑的频率范围内将呈现均匀的频率响应和零相位偏移。这些特性在快速复杂校准中可能非常有用，即通过替代法确定其他水听器的幅度和相位响应。此外，由于其坚固的设计和线性度，这些光纤水听器也可以应对高强度聚焦超声（HIFU）和其他治疗应用带来的挑战。总体而言，这项工作的结果表明，当完全开发出来后，FO探头将非常适合于超声场的高频测量，并能够补充当前有限孔径压电聚偏氟乙烯水听器收集的数据。
