Accurate quantitative decoding of the 3D information encoded in in-line holograms, at best difficult optically, may be achieved by A/D sampling of the hologram followed by digital reconstruction. Using standard reconstruction technique, the resulting image bandwidth is limited by the size of the hologram. In addition, the phase ambiguity inherent in magnitude-only hologram recording yields, along with the desired object reconstruction, an out-of-focus conjugate artifact called the twin image. Both limited bandwidth and twin image restrict the available resolution well below the theoretical diffraction limit. In this paper an algorithm is presented which addresses both problems by iteratively combining phase retrieval and spectrum continuation to produce estimates of the phase of the recorded hologram, and both magnitude and phase of the hologram beyond its physically recorded boundaries.Since algorithms based on spectral continuation are sensitive to the constraints imposed on the extent of the objects being imaged (which must be space limited), a method for selecting these constraints adaptively was developed. Effective use of adaptive constraints greatly accelerates convergence of the algorithm compared to fixed constraints. The chosen adaptive constraint selection rule is shown to have an error-cmecting property in which over-constraint is naturally corrected and the constraint set boundaries stably relax toward the actual object boundaries. Examples demonstrate the degree of improvement in resolution over conventional reconstruction, and over reconstruction with phase retrieval only. This algorithm suggests the possibility of super-resolution holography, in which the diffraction limit is exceeded. While difficult to achieve in practice, super-resolution has been demonstrated for other kinds of imaging but not heretofore considered for holography.
A special class of planar and spatial linkage mechanisms is presented in which for a continuous full rotation or continuous rocking motion of the input link, the output link undergoes two continuous rocking motions.In a special case of such mechanisms, for periodic motions of the input link with a fundamental frequency ω, the output motion is periodic but with a fundamental frequency of 2ω. In this paper, the above class of linkage mechanisms are referred to as speed-doubling linkage mechanisms. Such mechanisms can be cascaded to provide further doubling of the fundamental frequency (rocking motion) of the output motion. They can also be cascaded with other appropriate linkage mechanisms to obtain crank-rocker or crank-crank type of mechanisms. The conditions for the existence of speed-doubling linkage mechanisms are provided and their mode of operation is described in detail. Such speed-doubling mechanisms have practical applications, particularly when higher output speeds are desired, since higher output motions can be achieved with lower input speeds. Such mechanisms also appear to generally have force transmission and dynamics advantages over regular mechanisms designed to achieve similar output speeds.
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