TV holography and shearography in experimental mechanics

Sammanfattning: TV holography is an optical non-contacting whole field technique to measure deformation. Names as ESPI or Electronic speckle pattern interferometry, Electro-optic holography and Electronic holography are commonly used for this real-time video based interferometric technique. Shearography has become an important tool in non destructive testing. It is a TV holography technique that measures spatial derivatives of deformations. The introduction chapter of this thesis includes examples of applications and gives a brief description of the techniques. The following chapters contain scientific papers which describe the further development and new applications of TV holography and shearography. First, a new algorithm called temporal phase unwrapping is described for use in step loaded interferornetric measurements. Spatial unwrapping that can cause problem is avoided. Main advantages are; it is inherent simple, errors are constrained within the high-noise regions and real discontinuities are automatically unwrapped correctly. The algorithm has been applied to shape measurements using projected fringes and phase stepping. This technique easily measures the shape of three dimensional discontinuous objects. Then, a technique is developed aimed to simplify pulsed laser holographic experiments. It is a TV holographic technique that allows quantitative measurements from only two recorded single exposure frames. It can be applied to sequences of recorded frames for time resolved experiments. Furthermore, the alignment of the set-up is simple compared to other similar techniques. Thirdly, a new optical design is presented which makes two simultaneous experiments on one camera possible. The design has been used for combined out-of-plane sensitive TV holography and shearography experiments as well as for comparative applications. The two quantities can be measured precisely from one single experiment. The comparative configuration offers simultaneous visualisation of both the test object and its difference with respect to a master in real-time. It might become a useful tool in production quality control. In the last part, reciprocal principles are combined with TV holography techniques. Hidden forces and sound distributions are measured, and non-contacting vibration exciters are calibrated. The methods are fast and easy to use and can also be used with other measurement techniques and even with point techniques. The sound distribution measurements are applied to vibration modes of a violin.