Holography Using an Extended Spatially Incoherent Source
When a light source other than a laser is employed for making a hologram, a considerable reduction of the image quality results, owing to the small spatial and time coherence of the source. In 1967, Leith and Upatnieks made a hologram of very excellent quality with their achromatic fringe system (ref.1). They placed a photographic plate at the image plane of a grating and recorded a hologram between two beams of different orders of diffraction, in either of which was inserted the transparent object to be recorded. They introduced the time coherence requirement which made possible the application of a high-pressure mercury arc, but did not deal with the spatial coherence. Kato and Suzuki later extended their method to the spatial coherence problem and obtained some qualitative results which related the source size to the resolution limit of the reconstructed image(ref.2). These studies, however, were concerned mainly with their particular arrangements and no attempts were made to derive a general theory of the image formation for a hologram made by using a thermal source.
KeywordsReference Beam Path Difference Time Coherence Source Size Photographic Plate
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