Elektronische Vorrichtung zum Erzeugen eines sinusfoermigen Wechselstroms

摘要

1329005 Holography PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 8 Sept 1970 [10 Sept 1969] 42940/70 Heading G2J In the production of phase holograms in the hologram plane there is superposed on the interference patterns produced by the interference of coherent object and reference beams at least one additional interference pattern produced by an additional beam such that the additional interference pattern has a phase surface which corresponds to the phase surface of the object beam multiplied by an integer which is greater than unity, the hologram being processed to give a phase hologram whereby in an image reconstructed from which undesired ghost images of the higher diffraction orders are attenuated. If desired two such additional patterns are superposed. It is preferred that the reference beams have non- planar wave-fronts. In one embodiment the additional interference pattern is formed by reconstruction of an additional hologram. The phase holograms may be made using an object wave field produced from at least one point source, the or each point source being located at f from the hologram plane, and the or each additional beam being derived from point sources located at distances f/2, f/3, f/4 from the hologram plane. Alternatively the additional beam(s) may be directed at the hologram plane at an angle which is the angle of the object beam multiplied by the integer. The object and additional beams may be derived from an intermediate hologram.