In this paper, we consider a simple object-independent diffuser for digital holography that is characterized by a constant absolute value of the phase difference between its samples. In order to have desirable charact...
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ISBN:
(纸本)0819437581
In this paper, we consider a simple object-independent diffuser for digital holography that is characterized by a constant absolute value of the phase difference between its samples. In order to have desirable characteristics, the distribution of the signs of phase difference of it must be sufficiently randomized. We thus propose an effective algorithm for this purpose. Finally, we show that this diffuser can be used to initialize the phase of an intensity object for successfully calculating its complex amplitude, which is band-limited and at the same time possesses a smooth spectrum, and which fulfills the basic requirement for efficiently encoding it into a hologram and reconstructing it with reduced speckles.
An iterative fourier transform algorithm (IFTA) is applied for multilevel image quantization. A spatial operator is introduced. based on local signal adaptation, which allows a flexible handling of the quantization no...
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An iterative fourier transform algorithm (IFTA) is applied for multilevel image quantization. A spatial operator is introduced. based on local signal adaptation, which allows a flexible handling of the quantization noise, especially near the medium quantization level. Examples are shown and comparisons with other iterative fourier transform algorithms are performed. (C) 1998 Elsevier Science B.V. All rights reserved.
For five selected diffraction patterns, the combing effect of phase and spatial quantization to diffraction efficiency is evaluated by checking the effectiveness of the proposed efficiency limit sinc(2)(1/Z)eta(slim),...
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ISBN:
(纸本)0819428736
For five selected diffraction patterns, the combing effect of phase and spatial quantization to diffraction efficiency is evaluated by checking the effectiveness of the proposed efficiency limit sinc(2)(1/Z)eta(slim), where Z is the number of uniformly distributed phase levels and eta(slim) is the efficiency limit due to spatial quantization only. The simulation results show that the effectiveness of the above efficiency limit depends on the number of phase levels, diffraction pattern and the initial random phase. For some patterns, the above efficiency limit approximately holds for both Z = 4 and Z = 8.
We propose a new multicriteria method for the determination of computer-generated holograms (CGH's). For this purpose, the direct binary search (DBS) algorithm for computing CGH's has been modified to converge...
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We propose a new multicriteria method for the determination of computer-generated holograms (CGH's). For this purpose, the direct binary search (DBS) algorithm for computing CGH's has been modified to converge on a new error function that defines the optimal trade-off among different criteria. This approach allows us to control the trade-off between the amplitude error and the diffraction efficiency and to provide a rigorous figure of merit. Comparisons among different encoding methods show that the best results are obtained with a modified version of the DBS method combined with the iterative fourier transform algorithm. (C) 1997 Optical Society of America.
We describe a new approach to suppress undesired diffraction orders in the signal area of a fourier plane diffractive optical element (DOE). We implement this new approach for the DOE design by a two-stage iterative F...
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We describe a new approach to suppress undesired diffraction orders in the signal area of a fourier plane diffractive optical element (DOE). We implement this new approach for the DOE design by a two-stage iterative fourier transform algorithm that incorporates an adaptive optimization of the signal-to-noise ratio and does not require the introduction of a dummy output area outside the field of view. A comparison among this approach and three other approaches are presented on the basis of numerical results from several sample diffraction patterns. (C) 1997 Optical Society of America.
A design method is presented for computing the transmittance of computer-generated holograms dedicated to geometric transformations. The procedure is based on an iterative fourier transform algorithm and allows both t...
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A design method is presented for computing the transmittance of computer-generated holograms dedicated to geometric transformations. The procedure is based on an iterative fourier transform algorithm and allows both the quantization of the hologram levels and the accuracy of the transformed output to be taken into account, Computer simulations and experimental results are presented, confirming this flexible design approach.
A paraxial diffractive element is defined by a signal wave which is specified in a window of finite extent. The iterative fourier transform algorithm is a well-known method to iteratively encode paraxial diffractive e...
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ISBN:
(纸本)0819417513
A paraxial diffractive element is defined by a signal wave which is specified in a window of finite extent. The iterative fourier transform algorithm is a well-known method to iteratively encode paraxial diffractive elements by making use of parameters of freedom. However, the algorithm suffers from a slow convergence if the parameters of freedom are limited. Thus, there is a demand for more efficient encoding strategies. Fienup considered to use descent methods for solving phase-retrieval problems which turned out to be very efficient. In this paper, we modify his theory that it can be applied for the design of diffractive phase elements. Computer simulations document that descent methods have a clearly better performance than the iterative fourier transform algorithm.
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