Holographic Interferometry with Fringe Control and On-Line Digital Phase Measurement

Holographic interferometry has developed into a powerful and sensitive tool in industry and research for investigating surface deformation resulting from mechanical, thermal and vibrational stress. However, despite the vast amount of research, it has not yet resulted in a practical quantitative tool, and it remains often limited to the laboratory. In contrast to classical interferometry, the interpretation and quantification of holographic interferograms remains a complex and tedious task. This is essentially due to the fact that holographic interferometers are very sensitive to rigid body motion which can overshadow or even obliterate the deformation fringes, and that commonly used double exposure interferometers are inflexible since the interfering wavefronts are locked together.