Diffraction-based determination of the phase modulation for general spatial light modulators

Author(s): David Engström, Gabriel Milewski, Jörgen Bengtsson, and Sheila Galt

Abstract:

“We describe a characterization method based on diffraction for obtaining the phase response of spatial light modulators (SLMs), which in general exhibit both amplitude and phase modulation. Compared with the conventional interferometer-based approach, the method is characterized by a simple setup that enables in situ measurements, allows for substantial mechanical vibration, and permits the use of a light source with a fairly low temporal coherence. The phase determination is possible even for a SLM with a full amplitude modulation depth, i.e., even if there are nulls in the amplitude transmission characteristic of the SLM. The method successfully determines phase modulation values in the full 2π rad range with high accuracy. The experimental work includes comparisons with interferometer measurements as well as a SLM characterization with a light-emitting diode (LED).”

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Publication: Applied Optics
Issue/Year: Applied Optics, Vol. 45, Issue 28, pp. 7195-7204 (2006)
DOI: 10.1364/AO.45.007195

Algorithm for computing holographic optical tweezers at video rates

Author(s): Mario Montes-Usategui, Encarnación Pleguezuelos, Jordi Andilla, Estela Martín-Badosa, and Ignacio Juvells

Abstract:

“Digital holography enables the creation of multiple optical traps at arbitrary three-dimensional locations and spatial light modulators permit updating those holograms at video rates. However, the time required for computing the holograms makes interactive optical manipulation of several samples difficult to achieve. We introduce an algorithm for computing holographic optical tweezers that is both easy to implement and capable of speeds in excess of 10 Hz when running on a Pentium IV computer. A discussion of the pros and cons of the algorithm, a mathematical analysis of the efficiency of the resulting traps, as well as results of the three-dimensional manipulation of polystyrene micro spheres are included.”

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Publication: SPIE Digital Library
Issue/Year: Proceedings Volume 6326, Optical Trapping and Optical Micromanipulation III; 63262X (2006)
DOI: 10.1117/12.680504

Design of a low-cost interactive holographic optical tweezers system

Author(s): E. Pleguezuelos, J. Andilla, A. Carnicer, E. Martín-Badosa, S. Vallmitjana, and M. Montes-Usategui.

Abstract:

“The paper describes the design of an inexpensive holographic optical tweezers setup. The setup is accompanied by software that allows real-time manipulation of the sample and takes into account the experimental features of the setup, such as aberration correction and LCD modulation. The LCD, a HoloEye LCR-2500, is the physical support of the holograms, which are calculated using the fast random binary mask algorithm. The real-time software achieves 12 fps at full LCD resolution (including aberration correction and modulation) when run on a Pentium IV HT, 3.2 GHz computer.”

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Publication: SPIE Proceedings
Issue/Year: Proc. SPIE 6326, 63262Q (2006)
DOI: 10.1117/12.680593

Direct observation of Gouy phase shift in a propagating optical vortex

Author(s): Junichi Hamazaki, Yuriya Mineta, Kazuhiro Oka, and Ryuji Morita

Abstract:

“Direct observation of Gouy phase shift on an optical vortex was presented through investigating the intensity profiles of a modified LGpm beam with an asymmetric defect, around at the focal point. It was quantitatively found that the rotation profile of a modified LGpm beam manifests the Gouy phase effect where the rotation direction depends on only the sign of topological charge m. This profile measurement method by introducing an asymmetric defect is a simple and useful technique for obtaining the information of the Gouy phase shift, without need of a conventional interference method. In addition, the 3-dimernsional trajectory of the defect was found to describe a uniform straight line.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 14, Issue 18, pp. 8382-8392, 2006
DOI: 10.1364/OE.14.008382

An adaptive optics imaging system based on a high-resolution liquid crystal on silicon device

Author(s): Quanquan Mu, Zhaoliang Cao, Lifa Hu, Dayu Li, and Li Xuan

Abstract:

“An adaptive optics imaging system is introduced in this paper. A high resolution liquid crystal on silicon (LCOS) device was used as a phase only wave front corrector instead of a conversional deformable mirror. The wave front aberration was detected by a Shack-Hartmann (SH) wave front sensor, which has λ/100 rms wave front measurement accuracy. Under this construction 0.09λ (λ=0.6328µm) Peak to Valley correction precision was reached. Further more, some low frequency hot convection turbulence induced by an electric iron was compensated in real time at the same precision. The Modulation Transfer Function (MTF) of this system was also measured before and after wave front correction. Under the active correction of LCOS, the system reached the diffraction limited resolution approximately 65l p/mm on the horizontal direction. All of this showed the ability of using this device in high resolution, low temporal turbulence imaging system, such as retinal imaging, to improve the resolution performance.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 14, Issue 18, pp. 8013-8018, 2006
DOI: 10.1364/OE.14.008013

Laguerre-Gaussian supercontinuum

Author(s): H. I. Sztul, V. Kartazayev, and R. R. Alfano

Abstract:

“We show what is believed to be the first coherent white-light optical vortices generated from supercontinuum that have the azimuthally varying phase structure consistent with a monochromatic Laguerre-Gaussian beam. Two methods of Laguerre-Gaussian supercontinuum generation are discussed and contrasted. We use a computer-generated hologram to convert a Gaussian white-light supercontinuum source into Laguerre-Gaussian supercontinuum.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 31, Issue 18, pp. 2725-2727, 2006
DOI: 10.1364/OL.31.002725

Dynamic speckle illumination microscopy with translated versus randomized speckle patterns

Author(s): Cathie Ventalon and Jerome Mertz

Abstract:

“Dynamic speckle illumination (DSI) microscopy is a widefield fluorescence imaging technique that provides depth discrimination. The technique relies on the illumination of a sample with a sequence of speckle patterns. We consider an image processing algorithm based on a differential intensity variance between consecutive images, and demonstrate that DSI sectioning strength depends on the dynamics of the speckle pattern. Translated speckle patterns confer greater sectioning strength than randomized speckle patterns because they retain out-of-focus correlations that lead to better background rejection. We present a theory valid for arbitrary point-spread-functions, which we corroborate with experimental results.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 14, Issue 16, pp. 7198-7209, 2006
DOI: 10.1364/OE.14.007198

Polarization encoding and multiplexing of two-dimensional signals: application to image encryption

Author(s): Unnikrishnan Gopinathan, Thomas J. Naughton, and John T. Sheridan

Abstract:

“We discuss an optical system that encodes an input signal to a polarization state, using a spatial light modulator (SLM). Using two SLMs the optical system multiplexes two 2D signals in the polarization domain, and we demonstrate the multiplexing of two binary images. The encryption and decryption of two binary images using an xor operation is also presented.”

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Publication: Applied Optics
Issue/Year: Applied Optics, Vol. 45, Issue 22, pp. 5693-5700, 2006
DOI: 10.1364/AO.45.005693

Generation of achromatic Bessel beams using a compensated spatial light modulator

Author(s): Jonathan Leach, Graham M. Gibson, Miles J. Padgett, Elric Esposito, Gail McConnell, Amanda J. Wright, and John M. Girkin

Abstract:

“We report the creation of white-light, achromatic Bessel beams using a spatial light modulator and a prism to compensate for the dispersion. Unlike the Bessel beam created by a refractive axicon, this achromatic beam has a radial wavevector and hence an intensity cross-section which is independent of wavelength. The technique also lends itself to the generation of higher order Bessel beams with an on-axis optical vortex and associated orbital angular momentum.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 14, Issue 12, pp. 5581-5587, 2006
DOI: 10.1364/OE.14.005581

Dynamisches System für die Aufnahme und optische Rekonstruktion von digitalen Hologrammen

Author(s): G. Wernicke, J. Frank, C. Günther, S. Krüger

Abstract:

“Es wird ein Aufbau zur Aufnahme und optischen Rekonstruktion von digitalen Hologrammen unter Verwendung von reflektiven Flüssigkristalldisplays vorgestellt. Anwendungen mit einer speziell modulierten Beleuchtung bei der Aufnahme zur Darstellung von holographischen Interferogrammen und die optische Rekonstruktion von Röntgenhologrammen wird gezeigt.”

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Publication: DGaO Proceedings, (free download)
ISSN: 1614-8436
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