动态散斑相位的希尔伯特变换分析方法

Phase analysis method based on Hilbert transform in dynamic speckle pattern interferometry

为了精确地测量物体表面的动态形变过程,提出了一种基于希尔伯特变换的相位分析方法。形变过程通过连续采集的散斑干涉图序列来记录和分析,动态散斑的二维相位分布通过逐点希尔伯特变换和整幅干涉图的相位展开相结合的方法获得。在时域中,将成像器件的各个像素点视为独立的探测单元,得到了包含形变信息的一维时域干涉信号,在去除干涉信号的背景强度之后,利用希尔伯特变换和三角变换相结合的方法提取相位差以避免干涉信号调制强度波动所带来的影响。在空域中,使用傅里叶相位滤波器进行去噪处理,并通过基于离散余弦变换(DCT)的相位展开得到连续相位分布场。对橡胶板的动态形变进行了实时测量,获得了不同形变时刻的相位分布图,其中单幅可分辨的最大条纹数为26,对应的形变测量最大值为6.92μm。实验结果显示:本文方法计算简单,易于实现,适用于动态散斑的相位分析。

To measure the dynamic deformation of the obieet accurately, a phase analysis memoa baseu on Hilbert transform is proposed. A sequence of speckle interfograms is recorded throughout the entire process of out-of-plane deformation. The 2D phase distribution of the dynamic speckle pattern is acquired by temporal Hilbert transform and spatial phase unwrapping. In time domain, each pixel of the image sensor probes the surface as an independent unit and the deformation information coded with the time-intensity modulation is obtained. After the bias intensity is removed, the wrapped phase difference between the initial and current states is directly determined by using Hilbert transform and triangular transform. In space domain,a Fourier phase filter is employed to obtain a low noisy phase map. And the continuous phase distribution is acquired by the phase unwrapping algorithm based on discrete cosine transform （DCT）. Finally, the experiment is carried out to study the dynamic deformation of a rubber plate. High quality BD phase distribution maps with different fringe densities are obtained, which can represent different deformation states. Under the experimental conditions ,the maximum number of fringes resolvable in one frame is 26 ,which indicates the largest measurable deformation in the experiment is 6.92μm. The experimental results demonstrate that this method simplifies the algorithm, thus suitable for the real time detection of the dynamic deformation.