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.”

Link to Publications Page

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

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.”

Link to Publications Page

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.”

Link to Publications Page

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.”

Link to Publications Page

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.”

Link to Publications Page

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.”

Link to Publications Page

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

Numerical analysis of systematic errors in an optical encryption system

Author(s): David S. Monaghan, Unnikrishnan Gopinathan, Damien P. Kelly, Thomas J. Naughton, John T. Sheridan

Abstract:

“We consider a double random phase encoding Encryption/Decryption system in which the image encryption/decryption process is performed numerically. In this paper we look at the effect of quantisation in the decryption process due to the discrete values which a spatial light modulator can display. We look at the characterisation of a transmissive spatial light modulator and we present results from simulations of the system.”

Link to Publications Page

Publication: SPIE Proceedings
Issue/Year: Proc. SPIE, Vol. 6187, 61870X (2006)
DOI: 10.1117/12.663063

Multipoint Holographic Optical Velocimetry in Microfluidic Systems

Author(s): R. Di Leonardo, J. Leach, H. Mushfique, J. M. Cooper, G. Ruocco, and M. J. Padgett

Abstract:

“We show how holographic optical trapping can be used for the multipoint measurement of fluid flow in microscopic geometries. An array of microprobes can be simultaneously trapped and used to map out the fluid flow in a microfluidic device. The optical traps are alternately turned on and off such that the probe particles are displaced by the flow of the surrounding fluid and then retrapped. The particles’ displacements are monitored by digital video microscopy and directly converted into velocity field values. This technique enables the measurement of a two-dimensional flow field at points arbitrarily distributed in a three-dimensional volume. The validity of the technique is demonstrated for the case of the flow around a spinning sphere and the flow at the outlet of a microchannel.”

Link to Publications Page

Publication: Physical Review Letters
Issue/Year: Phys. Rev. Lett. 96, 134502 (2006)
DOI: 10.1103/PhysRevLett.96.134502

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.”

Link to Publications Page

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.”

Link to Publications Page

Publication: Optics Express
Issue/Year: Optics Express, Vol. 14, Issue 6, pp. 2250-2255, 2006
DOI: 10.1364/OE.14.002250
1 12 13 14 15 16 18