Dorney T D, Baraniuk R G, Mittleman D M
Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77251-1892, USA.
J Opt Soc Am A Opt Image Sci Vis. 2001 Jul;18(7):1562-71. doi: 10.1364/josaa.18.001562.
Imaging systems based on terahertz (THz) time-domain spectroscopy offer a range of unique modalities owing to the broad bandwidth, subpicosecond duration, and phase-sensitive detection of the THz pulses. Furthermore, the possibility exists for combining spectroscopic characterization or identification with imaging because the radiation is broadband in nature. To achieve this, we require novel methods for real-time analysis of THz waveforms. This paper describes a robust algorithm for extracting material parameters from measured THz waveforms. Our algorithm simultaneously obtains both the thickness and the complex refractive index of an unknown sample under certain conditions. In contrast, most spectroscopic transmission measurements require knowledge of the sample's thickness for an accurate determination of its optical parameters. Our approach relies on a model-based estimation, a gradient descent search, and the total variation measure. We explore the limits of this technique and compare the results with literature data for optical parameters of several different materials.
基于太赫兹（THz）时域光谱的成像系统，由于太赫兹脉冲具有宽带宽、亚皮秒持续时间以及相敏检测等特性，提供了一系列独特的模态。此外，由于这种辐射本质上是宽带的，所以存在将光谱表征或识别与成像相结合的可能性。为实现这一点，我们需要用于太赫兹波形实时分析的新方法。本文描述了一种从测量的太赫兹波形中提取材料参数的稳健算法。我们的算法在特定条件下能同时获得未知样品的厚度和复折射率。相比之下，大多数光谱透射测量需要知道样品的厚度才能准确确定其光学参数。我们的方法依赖于基于模型的估计、梯度下降搜索和全变差测度。我们探索了该技术的局限性，并将结果与几种不同材料光学参数的文献数据进行了比较。
