Department of Phoniatrics and Pediatric Audiology, University Hospital Erlangen Medical School, 91054 Erlangen, Germany.
IEEE Trans Med Imaging. 2010 Dec;29(12):1979-91. doi: 10.1109/TMI.2010.2055578.
The ability to communicate with our voice can be regarded as the concatenation of the two processes "phonation" and "modulation." These take place in the larynx and palatal and oral region, respectively. During phonation the audible primary voice signal is created by mutual reaction of vocal folds with the exhaled air stream of the lungs. The underlying interactions of masses, fluids and acoustics have yet to be identified and understood. One part of the primary signal's acoustical source are vortex induced vibrations, as e.g., created by the Coandăeffect in the air stream. The development of these vorteces is determined by the shape and 3-D movements of the vocal folds in the larynx. Current clinical in vivo research methods for vocal folds do not deliver data of satisfactory quality for fundamental research, e.g., an endoscope is limited to 2-D image information. Based hereupon, a few improved methods have been presented, however delivering only selective 3-D information, either for a single point or a line. This stands in contrast to the 3-D motions of the entire vocal fold surface. More complex imaging methods, such as MRI, do not deliver information in real-time. Thus, it is necessary to develop an easily applicable, more improved examination method, which allows for 3-D data of the vocal folds surfaces to be obtained. We present a method to calibrate a 3-D reconstruction setup including a laser projection system and a high-speed camera. The setup is designed with miniaturization and an in vivo application in mind. The laser projection system generates a divergent grid of 196 laser dots by diffraction gratings. It is calibrated with a planar calibration target through planar homography. In general, the setup allows to reconstruct the topology of a surface at high frame rates (up to 4000 frames per second) and in uncontrollable environments, as e.g., given by the lighting situation (little to no ambient light) and varying texture (e.g., varying grade of reflection) in the human larynx. In particular, this system measures the 3-D vocal fold surface dynamics during phonation. Applied to synthetic data, the calibration is shown to be robust (error approximately 0.5 μm) regarding noise and systematic errors. Experimental data gained with a linear z -stage proved that the system reconstructs the 3-D coordinates of points with an error at approximately 15 μm. The method was applied exemplarily to reconstruct porcine and artificial vocal folds' surfaces during phonation. Local differences such as asymmetry between left and right fold dynamics, as well as global parameters, such as opening and closing speed and maximum displacements, were identified and quantified.
我们可以将声音的产生视为“发声”和“调制”这两个过程的串联。这两个过程分别发生在喉部和腭部及口腔区域。在发声过程中，可听的原始声音信号是由声带与肺部呼出的气流相互作用产生的。相互作用的质量、流体和声学仍有待确定和理解。原始信号的声学源的一部分是涡流诱导振动，例如，在气流中由科恩达效应产生。这些涡旋的发展取决于喉部声带的形状和 3D 运动。目前，用于声带的临床体内研究方法无法为基础研究提供质量令人满意的数据，例如，内窥镜仅限于 2D 图像信息。在此基础上，已经提出了一些改进的方法，但仅提供了单点或线的选择性 3D 信息。这与整个声带表面的 3D 运动形成对比。更复杂的成像方法，如 MRI，无法实时提供信息。因此，有必要开发一种易于应用的、更先进的检查方法，该方法可以获取声带表面的 3D 数据。我们提出了一种校准 3D 重建设置的方法，该设置包括激光投影系统和高速摄像机。该设置的设计考虑了小型化和体内应用。激光投影系统通过衍射光栅生成 196 个激光点的发散网格。它通过平面单应标定平面标定靶。一般来说，该设置允许在高帧率（高达每秒 4000 帧）和不可控环境中重建表面的拓扑结构，例如，由照明情况（几乎没有环境光）和人喉内不断变化的纹理（例如，反射程度不同）给出。特别是，该系统在发声过程中测量声带的 3D 表面动力学。应用于合成数据，标定结果表明该系统对噪声和系统误差具有鲁棒性（误差约为 0.5μm）。通过线性 z 台获得的实验数据证明，该系统可以以约 15μm 的误差重建点的 3D 坐标。该方法被示例性地应用于在发声过程中重建猪和人工声带的表面。识别并量化了局部差异，例如左、右褶皱动力学之间的不对称性，以及全局参数，例如张开和闭合速度以及最大位移。
