Rajshekhar G, Gorthi Sai Siva, Rastogi Pramod
Applied Computing and Mechanics Laboratory, IMAC IS ENAC EPFL, Swiss Federal Institute of Technology, 1015 Lausanne, Switzerland.
Rev Sci Instrum. 2009 Sep;80(9):093107. doi: 10.1063/1.3234260.
Measurement of strain, curvature, and twist of a deformed object play an important role in deformation analysis. Strain depends on the first order displacement derivative, whereas curvature and twist are determined by second order displacement derivatives. This paper proposes a pseudo-Wigner-Ville distribution based method for measurement of strain, curvature, and twist in digital holographic interferometry where the object deformation or displacement is encoded as interference phase. In the proposed method, the phase derivative is estimated by peak detection of pseudo-Wigner-Ville distribution evaluated along each row/column of the reconstructed interference field. A complex exponential signal with unit amplitude and the phase derivative estimate as the argument is then generated and the pseudo-Wigner-Ville distribution along each row/column of this signal is evaluated. The curvature is estimated by using peak tracking strategy for the new distribution. For estimation of twist, the pseudo-Wigner-Ville distribution is evaluated along each column/row (i.e., in alternate direction with respect to the previous one) for the generated complex exponential signal and the corresponding peak detection gives the twist estimate.
测量变形物体的应变、曲率和扭转在变形分析中起着重要作用。应变取决于一阶位移导数，而曲率和扭转则由二阶位移导数确定。本文提出了一种基于伪维格纳-威利分布的方法，用于在数字全息干涉测量中测量应变、曲率和扭转，其中物体的变形或位移被编码为干涉相位。在所提出的方法中，通过对沿着重建干涉场的每一行/列评估的伪维格纳-威利分布进行峰值检测来估计相位导数。然后生成一个幅度为单位值且以相位导数估计值为自变量的复指数信号，并评估该信号沿每一行/列的伪维格纳-威利分布。通过对新分布使用峰值跟踪策略来估计曲率。为了估计扭转，对生成的复指数信号沿每一列/行（即相对于前一个方向交替）评估伪维格纳-威利分布，相应的峰值检测给出扭转估计值。
