Enhanced resolution methods in shearography and holography for time-average vibration measurement

D. N. Borza

doi:10.1117/12.814697

3 October 2008 Enhanced resolution methods in shearography and holography for time-average vibration measurement

D. N. Borza

Proceedings Volume 7155, Ninth International Symposium on Laser Metrology; 715508 (2008) https://doi.org/10.1117/12.814697
Event: Ninth International Symposium on Laser Metrology, 2008, Singapore, Singapore

Abstract

Vibration measurement by time-average methods of different full-field techniques like speckle interferometry, digital holography or analog, optical holography is a powerful technique, able to provide vibration amplitude maps of high spatial resolution. The essential characteristic of full-field techniques is the simultaneous acquisition of data for all object points. Quantitative data processing aiming to obtain the full-field amplitude map is affected by several difficulties. The most important are the weak contrast of Bessel-type fringes and the speckle noise. The greatest obstacle in achieving complete amplitude field estimation comes from the orthogonal components of time-averaged interferograms, where the multiplicative, high-frequency phase noise covers the deterministic, vibration-related phase. Several researchers studied these problems in relation with the double-exposure method. In the present paper, the author presents in a single, unifying approach, these methods, common to all full-field interferometric techniques. An important reduction of multiplicative high-frequency phase noise allows obtaining fringe-averaged patterns whose intensity noise is much lower than in classical methods. The analysis leads to lower noise of the fringe patterns and extended measurement range, and also to a method of vibration-related phase estimation based on the mathematical inversion of the Bessel function, which may include in some stages subpixel precision.

Citation Download Citation

D. N. Borza "Enhanced resolution methods in shearography and holography for time-average vibration measurement", Proc. SPIE 7155, Ninth International Symposium on Laser Metrology, 715508 (3 October 2008); https://doi.org/10.1117/12.814697

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