Enhancement of moire interferometry by digital image processing

The main objective of this work is the enhancement of the whole field displacement monitoring technique of moire interferometry by the introduction of a new approach combining fractional fringe analysis and digital image processing. Targeted improvements include pushing moire interferometry into the ultra-high sensitivity domain and broadening its applicability to include cases of low fringe densities.; Although moire interferometry is considered one of the most sensitive techniques for displacement measurements, the methods used for data collection severely limited the capabilities of the technique. A better approach to determine displacements from moire fields may be based on the use of the relations between light intensity distribution in the field and the corresponding displacements. Taking this as the starting point, this thesis reviews briefly the different methods for displacement measurements with emphasis on moire methods. Moire interferometry and the governing equations for light intensity distributions in a general moire field are presented. The concept of fractional fringe analysis is then introduced and employing digital image processing as an automated, efficient, and accurate experimental means for that analysis is assessed. The development of a digital moire-fringe analyzer is explained and evaluation of the approach is conducted. This included an experimental validation of fractional fringe analysis, a numerical investigation of the effects introduced by digital filtering of optical noise, and a detailed uncertainty analysis.; The introduced approach increased the sensitivity of moire interferometry by up to two orders of magnitude. Random errors associated with data collection were greatly reduced. Cases of low fringe densities became valid for accurate strain analysis due to the large amount of data rendered. Initial null fields were properly handled. Applications including transient and steady state strain analysis of electronic packages, calibration of piezo-resistive stress-chips, investigation of the thermal expansion of composite sheets used in circuit boards, and determination of stress intensity factors in mode I, mode II and mixed mode, are also presented.; The features of the introduced enhanced moire interferometry, make the technique an excellent reliable, sensitive, and convenient tool for accurate strain analysis.