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Pulsed Digital Holography and Shearography


Holographic interferometry has been used for years in the mechanical and non-destructive testing domains. Classical systems have proved their ability to provide both qualitative and quantitative information on part deformation. Being a global technique and having a high sensitivity, holography is well suited for the analysis of part behaviour under mechanical or vibration loading. The applications were however restricted by the laser and recording media characteristics. PDHS project has developed a holography system that uses pulsed laser illumination (not sensitive to environment perturbations, fitted for dynamic measurements) and CCD recording (digital data enable quick quantitative analysis). Two systems have been provided throughout the project. The first one is a "1D measuring head" system which has been validated on the applications provided by the industrial end-users. It has been turned into a commercial system that is already available on the market. Based on these first promising results, it has been possible to develop a second system with the aim to achieve 3D measurement. This system was ready for validation a few months before the project end. Having proven high performances, it should be available as a commercial system by mid 99. Global performances of both systems can be illustrated by: - the field of view ranging up to 3 m² - the sensitivity (0,06 µm) and the measuring range (1 to 10 µm per image) - the adjustable working distance (adapted with glass fibre) (the range of applications; recording of the mode shape for harmonic vibrations; visualization of the vibration modes for steady vibrations with multiple modes; recording of transient events) - the adaptation to industrial environment