Dobrev I, Furlong C, Cheng J T, Rosowski J J
Center for Holographic Studies and Laser micro-mechaTronics - CHSLT Department of Mechanical Engineering, Worcester Polytechnic Institute, Worcester MA 01609.
Center for Holographic Studies and Laser micro-mechaTronics - CHSLT Department of Mechanical Engineering, Worcester Polytechnic Institute, Worcester MA 01609 ; Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston MA 02114 ; Department of Otology and Laryngology, Harvard Medical School, Boston, MA USA.
Exp Mech. 2015 Feb 1;55(2):459-470. doi: 10.1007/s11340-014-9945-4.
In this paper, we propose a multi-pulsed double exposure (MPDE) acquisition method to quantify in full-field-of-view the transient (i.e., >10 kHz) acoustically induced nanometer scale displacements of the human tympanic membrane (TM or eardrum). The method takes advantage of the geometrical linearity and repeatability of the TM displacements to enable high-speed measurements with a conventional camera (i.e., <20 fps). The MPDE is implemented on a previously developed digital holographic system (DHS) to enhance its measurement capabilities, at a minimum cost, while avoiding constraints imposed by the spatial resolutions and dimensions of high-speed (i.e., >50 kfps) cameras. To our knowledge, there is currently no existing system to provide such capabilities for the study of the human TM. The combination of high temporal (i.e., >50 kHz) and spatial (i.e., >500k data points) resolutions enables measurements of the temporal and frequency response of all points across the surface of the TM simultaneously. The repeatability and accuracy of the MPDE method are verified against a Laser Doppler Vibrometer (LDV) on both artificial membranes and ex-vivo human TMs that are acoustically excited with a sharp (i.e., <100 μs duration) click. The measuring capabilities of the DHS, enhanced by the MPDE acquisition method, allow for quantification of spatially dependent motion parameters of the TM, such as modal frequencies, time constants, as well as inferring local material properties.
在本文中，我们提出了一种多脉冲双曝光（MPDE）采集方法，用于在全视野范围内量化人鼓膜（TM或耳膜）由声学诱导产生的瞬态（即>10 kHz）纳米级位移。该方法利用了鼓膜位移的几何线性和可重复性，从而能够使用传统相机（即<20帧/秒）进行高速测量。MPDE是在先前开发的数字全息系统（DHS）上实现的，以在最小成本的情况下增强其测量能力，同时避免高速（即>50千帧/秒）相机的空间分辨率和尺寸所带来的限制。据我们所知，目前尚无现有系统能为研究人类鼓膜提供此类功能。高时间分辨率（即>50 kHz）和空间分辨率（即>500k数据点）的结合，使得能够同时测量鼓膜表面所有点的时间和频率响应。通过在人工膜和离体人鼓膜上使用尖锐（即<100微秒持续时间）咔嗒声进行声学激发，并与激光多普勒振动计（LDV）对比，验证了MPDE方法的可重复性和准确性。由MPDE采集方法增强的DHS测量能力，能够量化鼓膜的空间相关运动参数，如模态频率、时间常数，以及推断局部材料特性。
