| 1. |
- Huntley, J.M., et al.
(författare)
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Error-reduction methods for shape measurement by temporal phase unwrapping
- 1997
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Ingår i: Optical Society of America. Journal A. - 1084-7529 .- 1520-8532. ; 14:12, s. 3188-3196
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Tidskriftsartikel (refereegranskat)abstract
- Temporal phase unwrapping is a method of analyzing fringe patterns in which the fringe phase at each pixel is measured and unwrapped as a function of time t. We propose two methods for improving the signal-to-noise ratio of the total phase change by incorporating data from the intermediate phase values. The first involves fitting the expected curve to the measured phase history; the second involves Fourier transformation of the corresponding phasors. The performance of these methods is compared both experimentally, with data from a fringe projector based on a spatial-light modulator, and numerically. It is shown that the optimum performance is given by the Fourier transform method. The best way to use the first method is with decreasing exponentially with time from its maximum value to zero; this provides significant improvements in reliability, accuracy, and computation time compared with the original temporal unwrapping algorithm
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| 2. |
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| 3. |
- Marklund, Olov
(författare)
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Noise-insensitive two-dimensional phase unwrapping method
- 1998
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Ingår i: Optical Society of America. Journal A. - 1084-7529 .- 1520-8532. ; 15:1, s. 42-60
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Tidskriftsartikel (refereegranskat)abstract
- A new two-dimensional phase unwrapping method, based on an iterative computational procedure, is proposed. The method, which is derived with the use of a global cost function to minimize the phase discontinuities in the unwrapped phase map, has shown to produce robust and reliable results on very noisy phase data. Preprocessing operations, such as noise cleaning or segmentation, will in many cases be superfluous but may be included
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| 4. |
- Egorov, Igor, et al.
(författare)
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Forerunners in bi-gyrotropic materials
- 1998
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Ingår i: Journal of the Optical Society of America A. - 1084-7529. ; 15:9, s. 2391-2403
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Tidskriftsartikel (refereegranskat)abstract
- Forerunners (precursors) in linear, temporally dispersive, bigyrotropic materials are investigated with time-domain techniques. Bigyrotropic materials are characterized by 12 constitutive parameters (integral kernels). Specifically, the four susceptibility dyadics are all gyrotropic with a common gyrotropic axis. Pulse propagation along this axis is analyzed with dispersive (noncoupling) wave splitting and complex, time-dependent field vectors. Two numerical examples illustrating the method are presented.
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| 5. |
- Karlsson, Anders, et al.
(författare)
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Time-Domain Theory of Forerunners
- 1998
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Ingår i: Journal of the Optical Society of America A. - 1084-7529. ; 15:2, s. 487-502
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Tidskriftsartikel (refereegranskat)abstract
- The time-domain theory of forerunners (precursors) in temporally dispersive, nonmagnetic, isotropic materials is developed with the propagator technique. Specifically, the impulse response at a (comparatively) large propagation depth is expanded in two different ways: (a) with respect to the wave front and (b) with respect to slowly varying field components. A few numerical examples illustrating the theory are given.
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| 6. |
- Karlsson, Anders, et al.
(författare)
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Wave propagators for transient waves in periodic media
- 1995
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Ingår i: Journal of the Optical Society of America A. - 1084-7529. ; 12:7, s. 1513-1521
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Tidskriftsartikel (refereegranskat)abstract
- One-dimensional propagation of transient EM-waves in periodic media is studied. The media are periodic in the direction of propagation and can be of finite or infinite length. Wave propagators, that map a transient field from one point in the medium to another, are introduced. A number of useful relations for the propagators are presented. Some of these relations are used in the determination of explicit expressions for the short time behavior of a transient wave as it propagates in a periodic medium. The theory is exemplified by several numerical examples.
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| 7. |
- Kristensson, Gerhard, et al.
(författare)
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Mixing formulas in time domain
- 1998
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Ingår i: Journal of the Optical Society of America A. - 1084-7529. ; 15:5, s. 1411-1422
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Tidskriftsartikel (refereegranskat)abstract
- The dispersive properties of dielectric materials in both the time and the frequency domains are discussed. Special emphasis is placed on the treatment of heterogeneous materials, particularly two-phase mixtures. A time-domain Maxwell-Garnett rule is derived that differs from the corresponding frequency-domain formula in that it is expressed in terms of convolutions and inverse operators of the susceptibility kernels of the materials. Much of the analysis deals with the question of how the temporal dispersion of the dielectric responses of various physical materials is affected by the mixing process. Debye, Lorentz, Drude, and modified Debye susceptibility models are treated in detail.
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| 8. |
- Ochs, Robert L., et al.
(författare)
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Using local differential operators to model dispersion in dielectric media
- 1998
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Ingår i: Journal of the Optical Society of America A. - 1084-7529. ; 15:8, s. 2208-2215
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Tidskriftsartikel (refereegranskat)abstract
- Dispersion of electromagnetic waves is usually described in terms of an integrodifferential equation. We show that whenever a differential operator can be found that annihilates the susceptibility kernel of the medium, dispersion can be modeled by a partial differential equation without nonlocal operators
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