Abstract

Speckle shearing interferometry (shearography) is a full-field strain measurement technique that can be used in vibration analysis. In our case, we apply a method that combines the time-averaging and phase-shifting techniques. It produces binary phase patterns, where the phase changes are related to the zeroes of a Bessel $J_0$ function, typical of time-averaging. However, the contrast and resolution are better compared to traditional time-averaging. In a previous paper, we have shown that this is particularly useful in vibration testing performed under industrial conditions, because fringe patterns are noisier than in quiet laboratory environments. This paper goes a step further in proposing a processing method for estimating the vibration amplitude, for helping non-experts to identify vibration modes. Since shearography measures the spatial derivative of displacement, spatial integration is required. Prior to that, different processes like denoising, binarization, automated nodal line detection, and amplitude assignment are applied. We analyze the performance of the method on synthetic and experimental data, in the function of noise level and fringes density. Results on data acquired in an industrial environment illustrate the good performances of the proposed method.

© 2018 Optical Society of America

Identification of antinodes and zero-surface-strain contours of flexural vibration with time-averaged speckle pattern shearing interferometry

W. O. Wong, K. T. Chan, and T. P. Leung
Appl. Opt. 36(16) 3776-3784 (1997)

Quantitative vibration analysis using a single fringe pattern in time-average speckle interferometry

B. Deepan, C. Quan, and C. J. Tay
Appl. Opt. 55(22) 5876-5883 (2016)

Vibration measurement using phase-shifting time-average holographic interferometry

Suezou Nakadate
Appl. Opt. 25(22) 4155-4161 (1986)

Vibration measurement by the time-averaged electronic speckle pattern interferometry methods

Wei-Chung Wang, Chi-Hung Hwang, and Shu-Yu Lin
Appl. Opt. 35(22) 4502-4509 (1996)

Digital speckle pattern shearing interferometry: limitations and prospects

Mette Owner-Petersen
Appl. Opt. 30(19) 2730-2738 (1991)