Digital ultrasonic speckle phase-shifting method

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• 作者：Hongmao Zhu^a ; Yanyang Wu^b ; ^{yanwu027hust@163.com" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Ultrasonic speckle ; Phase-shifting technique ; Inner surface ; Small displacement ; Underwater measurement
• 刊名：Applied Acoustics
• 出版年：2016
• 出版时间：February 2016
• 年：2016
• 卷：103
• 期：part_PB
• 页码：221-225
• 全文大小：1287 K

文摘

The digital ultrasonic speckle phase-shifting method (USPM), which is introduced in this paper, can be applied to the measurement of small displacement that is smaller than speckle size at the test point compared to traditional ultrasonic speckle correlation method (USCM). Using USPM, a digital ultrasonic reference signal is introduced to interfere with the ultrasonic speckle signal, which is picked up at the test point on an object surface and is referred to as the object signal. As the phase of the reference signal is shifted several times using the software and then they superimpose with the object signal respectively, the phase of the object signal can be calculated according to the intensities of the superimposed signals. If the object surface moves a small distance, the phase variation of the object speckle can be detected by the same process. As a result, the displacement of the object surface can be measured. Based on the feature of ultrasonic speckles, inner surface displacement of an object can be measured using this proposed method. In this case, the effect of outer surface roughness to the measurement accuracy of USPM is examined experimentally. The experimental results show that the measurement is successful when the displacement is smaller than half of the speckle size at the test point and the roughness parameter R_a of the outer surface of the specimen is less than about 5.47 μm.