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

Spiral interferogram analysis

Author(s): Alexander Jesacher, Severin Fürhapter, Stefan Bernet, and Monika Ritsch-Marte

Abstract:

“Interference microscopy using spatial Fourier filtering with a vortex phase element leads to interference fringes that are spirals rather than closed rings. Depressions and elevations in the optical thickness of the sample can be distinguished immediately by the sense of rotation of the spirals. This property allows an unambiguous reconstruction of the object’s phase profile from one single interferogram. We investigate the theoretical background of “spiral interferometry” and suggest various demodulation techniques based on the processing of one single interferogram or multiple interferograms.”

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Publication: Journal of the Optical Society of America A
Issue/Year: JOSA A, Vol. 23, Issue 6, pp. 1400-1409 (2006)
DOI: 10.1364/JOSAA.23.001400

Quantitative imaging of complex samples by spiral phase contrast microscopy

Author(s): Stefan Bernet, Alexander Jesacher, Severin Fürhapter, Christian Maurer, and Monika Ritsch-Marte

Abstract:

“Recently a spatial spiral phase filter in a Fourier plane of a microscopic imaging setup has been demonstrated to produce edge enhancement and relief-like shadow formation of amplitude and phase samples. Here we demonstrate that a sequence of at least 3 spatially filtered images, which are recorded with different rotational orientations of the spiral phase plate, can be used to obtain a quantitative reconstruction of both, amplitude and phase information of a complex microscopic sample, i.e. an object consisting of mixed absorptive and refractive components. The method is demonstrated using a calibrated phase sample, and an epithelial cheek cell.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 14, Issue 9, pp. 3792-3805, 2006
DOI: 10.1364/OE.14.003792

Synthesis of multiple collinear helical modes generated by a phase-only element

Author(s): Jiao Lin, Xiaocong Yuan, Shaohua H. Tao, and Ronald E. Burge

Abstract:

“Phase-only elements are generally more desirable than complex-amplitude-modulated elements not only because of the higher diffraction efficiency but the readier implementation and fabrication. A novel iterative algorithm is proposed for generating multiple helical modes by a single phase-only element. A superposition of four helical modes is demonstrated experimentally by using a spatial light modulator.”

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Publication: Journal of the Optical Society of America A
Issue/Year: JOSA A, Vol. 23, Issue 5, pp. 1214-1218, 2006
DOI: 10.1364/JOSAA.23.001214

Aberration correction in holographic optical tweezers

Author(s): Kurt D. Wulff, Daniel G. Cole, Robert L. Clark, Roberto DiLeonardo, Jonathan Leach, Jon Cooper, Graham Gibson, and Miles J. Padgett

Abstract:

“Holographic or diffractive optical components are widely implemented using spatial light modulators within optical tweezers to form multiple, and/or modified traps. We show that by further modifying the hologram design to account for residual aberrations, the fidelity of the focused beams can be significantly improved, quantified by a spot sharpness metric. However, the impact this improvement has on the quality of the optical trap depends upon the particle size. For particle diameters on the order of 1 µm, aberration correction can improve the trap performance metric, which is the ratio of the mean square displacement of a corrected trap to an uncorrected trap, in excess of 25%, but for larger particles the trap performance is not unduly affected by the aberrations typically encountered in commercial spatial light modulators.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 14, Issue 9, pp. 4169-4174, 2006
DOI: 10.1364/OE.14.004169

Holographic optical trapping of aerosol droplets

Author(s): D. R. Burnham and D. McGloin

Abstract:

“We demonstrate the use of holographic optical tweezers for trapping particles in air, specifically aerosol droplets. We show the trapping and manipulation of arrays of liquid aerosols as well as the controlled coagulation of two or more droplets. We discuss the ability of spatial light modulators to manipulate airborne droplets in real time as well as highlight the difficulties associated with loading and trapping particles in such an environment. We conclude with a discussion of some of the applications of such a technique.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 14, Issue 9, pp. 4175-4181, 2006
DOI: 10.1364/OE.14.004175

Fast generation of holographic optical tweezers by random mask encoding of Fourier components

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

Abstract:

“The random mask encoding technique of multiplexing phase-only filters can be easily adapted to the generation of holographic optical tweezers. The result is a direct, non-iterative and extremely fast algorithm that can be used for computing arbitrary arrays of optical traps. Additional benefits include the possibility of modifying any existing hologram to quickly add more trapping sites and the inexistence of ghost traps or replicas.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 14, Issue 6, pp. 2101-2107, 2006
DOI: 10.1364/OE.14.002101

Highly efficient phase-conjugation of a 1 µm pico-second Laguerre-Gaussian beam

Author(s): Gyeong Bok Jung, Keiichiro Kanaya, and Takashige Omatsu

Abstract:

“We have demonstrated highly efficient Laguerre Gaussian beam generation by using a ring self-pumped phase conjugate mirror in the pico-second regime for the first time. The phase conjugate reflectivity was typically ~55%. We have also investigated the conservation of optical angular momentum.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol. 14, Issue 6, pp. 2250-2255, 2006
DOI: 10.1364/OE.14.002250

Fast digital hologram generation and adaptive force measurement in liquid-crystal-display-based holographic tweezers

Author(s): Marcus Reicherter, Susanne Zwick, Tobias Haist, Christian Kohler, Hans Tiziani, and Wolfgang Osten

Abstract:

“Computer-generated holograms in conjunction with spatial light modulators (SLMs) offer a way to dynamically generate holograms that are adapted to specific tasks. To use the full dynamic capability of the SLM, the hologram computation should be very fast. We present a method that uses the highly parallel architecture of a consumer graphics board to compute analytical holograms in video real time. A precice characterization of the SLM (Holoeye LC-R-2500) and the adaption of its settings to our near-infrared application is necessary to guarantee an efficient hologram reconstruction. The benefits of a fast computation of adapted holograms and the application of an efficient SLM are demonstrated by measuring the trapping forces of holographic tweezers.”

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Publication: Applied Optics
Issue/Year: Applied Optics, Vol. 45, Issue 5, pp. 888-896, 2006
DOI: 10.1364/AO.45.000888

Interactive approach to optical tweezers control

Author(s): Jonathan Leach, Kurt Wulff, Gavin Sinclair, Pamela Jordan, Johannes Courtial, Laura Thomson, Graham Gibson, Kayode Karunwi, Jon Cooper, Zsolt John Laczik, and Miles Padgett

Abstract:

“We have developed software with an interactive user interface that can be used to generate phase holograms for use with spatial light modulators. The program utilizes different hologram design techniques, allowing the user to select an appropriate algorithm. The program can be used to generate multiple beams and can be used for beam steering. We see a major application of the program to be in optical tweezers to control the position, number, and type of optical traps.”

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Publication: Applied Optics
Issue/Year: Applied Optics, Vol. 45, Issue 5, pp. 897-903, 2006
DOI: 10.1364/AO.45.000897