Abstract
In digital holography holograms are recorded by a CCD camera and images are reconstructed by a computer. Resolution of CCD is much lower than photographic materials to limit object size and image quality. This issue has been overcome by phaseshifting digital holography that derives the complex amplitude of object wave is directly derived by the phase shifting technique in inline setup which reduces the spatial frequency of the interference patterns on the CCD. This technique enables to record and reconstruct larger objects than in the conventional technique using off-axis setup. After image formation is explained, applications to interferometry are discussed. Since phase distribution at the object surface is directly derived in reconstruction, we only have to carry out phase-unwrapping to obtain distribution of surface height or displacement. For surface contouring we calculate the difference of the reconstructed phases before and after small tilt of the object illuminating beam. We attained an accuracy of 30μm using a wavelength of 633nm. Object size is limited by the ratio of wavelength to pixel pitch in the case of free space setup. We eliminated this limit by introducing a lens to image an object on to a CCD and could measure objects with the size of more than 10 centimeters.
