Despite the advantages of being highly sensitive and nondestructive, the digital speckle correlation method (DSCM) may have difficulties in detecting tiny defects such as delaminations in multilayer ceramic capacitors. This is because the presence of background noise always complicates the data processing. We present a new algorithm, which employs the wavelet-packet noise-reduction process together with the improved DSCM, to improve data processing. Both the computational error and the noise are shown to be reduced successfully by this new algorithm. The accuracy (or precision) of the improved DSCM is increased after operation of the wavelet-packet noise-reduction process. The most important feature of this new algorithm is that it can extract a small hillock signal from a large noisy background in a DSCM deformation result. This helps to save time in the detection of tiny defects, such as delamination, in a miniaturized electronic component.
© 1999 Optical Society of America
(120.4290) Instrumentation, measurement, and metrology : Nondestructive testing
(120.4630) Instrumentation, measurement, and metrology : Optical inspection
(120.6150) Instrumentation, measurement, and metrology : Speckle imaging
Xing Dai, Yan Cheong Chan, and Alex Chun Kwan So, "Digital Speckle Correlation Method Based on Wavelet-Packet Noise-Reduction Processing," Appl. Opt. 38, 3474-3482 (1999)