| 1. |
- Andersson, Angelica, et al.
(författare)
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Digital speckle-pattern interferometry: fringe retrieval for large in-plane deformations with digital speckle photography
- 1999
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Ingår i: Applied Optics. - : Optical Society of America. - 1559-128X .- 2155-3165. ; 38:25, s. 5408-5412
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Tidskriftsartikel (refereegranskat)abstract
- The compensation of large in-plane motions in digital speckle-pattern interferometry (DSPI) with the use of digital speckle photography (DSP) is demonstrated. Ordinary recordings of DSPI are recombined and analyzed with DSP. The DSP result is used to compensate for the bulk speckle motion prior to calculation of the phase map. This results in a high fringe contrast even for deformations of several speckle diameters. In addition, for the case of an in-plane deformation, it is shown that the absolute phase change in each pixel may be unwrapped by use of the DSP result as an initial guess. The principles of this method and experiments showing the in-plane rotation of a plate and the encounter of two rounded plates are presented
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| 2. |
- Gren, Per, et al.
(författare)
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Tomographic reconstruction of transient acoustic fields recorded by pulsed TV holography
- 1998
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 37:5, s. 834-840
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Tidskriftsartikel (refereegranskat)abstract
- Pulsed TV holography together with CT reconstruction were used to measure the three-dimensional distribution of transient acoustic fields in air. Holograms from several directions were directly recorded onto a CCD detector. From the recorded holograms, phase maps were quantitatively evaluated
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| 3. |
- Pasiskevicius, Valdas, et al.
(författare)
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Efficient Nd : YAG laser frequency doubling with periodically poled KTP
- 1998
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Ingår i: Applied Optics. - : Optical Society of America. - 1559-128X .- 2155-3165. ; 37:30, s. 7116-7119
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Tidskriftsartikel (refereegranskat)abstract
- Periodically poled flux-grown KTiOPO4 was used for efficient extracavity 1064-nm Nd:YAG laser frequency doubling. A conversion efficiency exceeding 65% was obtained in Q-switched operation, and 1.34 W of average frequency-doubled power was generated with 2.2 W of mode-locked laser output. The conversion efficiency is approximately two times higher for periodically poled KTP than for conventional type II phase-matched KTP. The measurements indicate that periodically poled KTP is less susceptible to optical damage than type II KTP.
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| 4. |
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| 5. |
- Saldner, Henrik O., et al.
(författare)
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Fourier-transform evaluation of phase data in spatially phase-biased TV holograms
- 1996
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 35:2, s. 332-336
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Tidskriftsartikel (refereegranskat)abstract
- TV holograms for spatial phase stepping are formed with a small angular offset between the object and the reference beams to give a spatial frequency bias to the pattern recorded by the TV camera. It is common to set the bias so that there is a 90° or 120° phase shift between adjacent pixels and to use the irradiance of three or more adjacent pixels to evaluate the phase of the interference. We report the Fourier-transform evaluation of such recordings to obtain their phase data. We also demonstrate the direct calculation of the phase difference between successive recordings without intermediate calculation of the random phase of each hologram. This technique is proposed as an approach to pulsed TV holography.
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| 6. |
- Saldner, Henrik O.
(författare)
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Phase-stepped television holographic technique for measuring phase and amplitude maps of small vibrations
- 1996
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 35:20, s. 3791-3798
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Tidskriftsartikel (refereegranskat)abstract
- Phase stepping between frames in TV holography is combined with sinusoidal phase modulation to determine phase and amplitude distributions of objects vibrating with small amplitudes 1,l@20, where l is the wavelength of the laser light used2. This technique has applications in, for example, optical modal analysis and the determination of harmonic sound fields in air and water. The noise reductionthat is obtained with the phase-stepping technique reduces the number of interferograms needed by one-half, which can shorten experimental time. The technique is robust, easy to use, and illustrated bymodes of vibration in a simple plate and in a more complicated structure 1a violin2.
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| 7. |
- Saldner, Henrik O., et al.
(författare)
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Temporal phase unwrapping : application to surface profiling of discontinuous objects
- 1997
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 36:13, s. 2770-2775
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Tidskriftsartikel (refereegranskat)abstract
- The recently proposed technique of temporal phase unwrapping has been used to analyze the phase maps from a projected-fringe phase-shifting surface profilometer. A sequence of maps is acquired while the fringe pitch is changed; the phase at each pixel is then unwrapped over time independently of the other pixels in the image to provide an absolute measure of surface height. The main advantage is that objects containing height discontinuities are profiled as easily as smooth ones. This contrasts with the conventional spatial phase-unwrapping approach for which the phase jump across a height discontinuity is indeterminate to an integral multiple of 2 . The error in height is shown to decrease inversely with the number of phase maps used.
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| 8. |
- Schedin, Staffan, et al.
(författare)
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Phase evaluation and speckle averaging in pulsed television holography
- 1997
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 36:17, s. 3941-3947
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Tidskriftsartikel (refereegranskat)abstract
- Double-pulsed (image-plane) TV holograms of transient bending waves in plates are recorded on separate frames in a CCD camera. A small angular offset between the reference and object beams, giving a spatial-frequency bias to the recorded pattern, permits quantitative evaluation of the phase of the interference. The Fourier spectrum of the image exhibits distinct parts that can be filtered out and inverse transformed to yield the phase information. Three different apertures of the imaging system are tested: a single slit, a double slit, and a three-hole aperture. Spatial speckle averaging is possible in the cases of the double-slit and three-hole apertures
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| 10. |
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