Holographic interferometry in a disturbed environment

Digital holographic interferometry (DHI) is an optical measurement technique that can be used to measure very small deformations and/or movements of an object. When the changes of an object are slow the measurement time has to be increased and vibrations of the components in the setup together with motion of the surrounding air start to interfere with the measurement. This thesis investigates the possibility of improving the quality of long time DHI measurements in a disturbed environment by post processing of the data. The approach has been to use the spatial correlation that exists in the noise by measuring a reference noise on a small stationary surface that is introduced in the field of view of the camera. This reference noise is then used in an RLS noise reduction filter to remove some of the noise from the other points in the image. The method has proven successful in removing noise caused by vibration where the spatial correlation is high within the noise. With air disturbances, only noise in the neighbourhood of the reference point is significantly reduced. The size of this region depends on the spatial scales present in the air disturbance.Validerat; 20101217 (root