| 摘要 |
A holographic system particularly for holographic interferometry which minimizes the effect of laser speckle yet permits viewing of the holographic image over a wide angular range at discrete angles. The scene beam passes a periodic grating structure, such as a wire mesh screen, a phase grating, or an amplitude grating for breaking up the scene beam into a number of discrete beams corresponding to different orders. The subject is interposed between the grating structure and the hologram. A lens may be arranged between the subject and the hologram for focusing the various discrete scene beams so that a desired number may be selected by an aperture plate. Alternatively, a pair of mirrors may be used for bringing together the discrete scene beams created by the grating structure. A further refinement consists of a second periodic grating structure disposed between the lens and the subject; again, the discrete scene beams may be focused by a lens. The two diffraction gratings preferably have different grating constants. Also, each of the discrete scene beams may be recorded on a separate hologram on which a reference beam is also directed. This may be effected by an additional periodic grating structure for also diffracting a discrete reference beam into the plane of each of the various holograms.
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