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Theo Lasser

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Publications associées (125)

Direct Observation of Transitions between Surface-Dominated and Bulk Diffusion Regimes in Nanochannels

Philippe Renaud, Arnaud Bertsch, Theo Lasser, Nicolas Durand, Claudio Dellagiacoma, Raphaël Goetschmann

The diffusion of charged proteins in liquid-filled nanometer-sized apertures with charged surfaces has been investigated with fluorescence correlation spectroscopy (FCS). Based on a two-dimensional (2D) multicomponent diffusion model, key parameters such a ...

2009

Method for recording color images and laser direct imaging signals of object, involves generating colored images, where common complementary metal-oxide semiconductor sensor has multiple sensor elements

Theo Lasser

NOVELTY - The method involves generating colored images, where a common complementary metal-oxide semiconductor sensor (7) has multiple sensor elements. A light with different wavelengths is supplied separately for recording color images. A radiation with ...

2009

Laser Doppler imaging for intraoperative human brain mapping

Marcel Leutenegger, Michaël Unser, Theo Lasser, Dimitri Nestor Alice Van De Ville, Rainer Leitgeb, Erica Martin-Williams

The identification and accurate location of centers of brain activity are vital both in neuro-surgery and brain research. This study aimed to provide a non-invasive, non-contact, accurate, rapid and user-friendly means of producing functional images intrao ...

Elsevier2009

Information Limits of Optical Coherence Imaging Through Scattering Media

Theo Lasser, Rainer Leitgeb

We develop an information-theoretic framework for the quantitative assessment of the maximum amount of information provided by optical coherence imaging through scattering media. We use our approach to investigate the fundamental dependence of the extracta ...

2009

Optical apparatus for dual beam heterodyne Fourier domain optical coherence tomography, has detector that synchronizes phase shift such that sample signal or sample interface moving at arbitrary velocity is detected by phase change

Adrian Bachmann, Theo Lasser, Roland Michaely, Martin Villiger, Rainer Leitgeb

NOVELTY - The apparatus has an optical unit for splitting a source field to produce and combine reference and biomedical sample light fields. An optical and electronic unit records a spectral interference pattern between combined light fields. A controlled ...

2008

Method for displaying field of brain of patient during brain surgery involves determining output image from analysis image values and displaying output image

Marcel Leutenegger, Theo Lasser, Antonio Lopez, Erica Martin-Williams

NOVELTY - The display method involves evaluating the sequence of images by: associating a first analysis image value to pixels in the first sequence of images to which pixels of same locations of the field (11) are imaged, respectively; associating a secon ...

2008

Frequency encoded assessment of retinal physiology

Adrian Bachmann, Theo Lasser, Roland Michaely, Cédric Blatter, Rainer Leitgeb

We demonstrate in-vivo functional imaging of the human retina with Fourier domain optical coherence tomography employing frequency encoding of an excitation pattern. The principle is based on projecting a modulated rectangular pattern across the foveal reg ...

Spie-Int Soc Optical Engineering, Po Box 10, Bellingham, Wa 98227-0010 Usa2008

Detection efficiency in total internal reflection fluorescence microscopy

Marcel Leutenegger, Theo Lasser

We present a rapid and flexible framework for the accurate calculation of the detection efficiency of fluorescence emission in isotropic media as well as in the vicinity of dielectric or metallic interfaces. The framework accounts for the dipole characteri ...

2008

Dynamic disorder in horseradish peroxidase observed with total internal reflection fluorescence correlation spectroscopy

Theo Lasser, Kai Hassler

This paper discusses the application of objective-type total internal reflection fluorescence correlation spectroscopy (TIR-FCS) to the study of the kinetics of immobilized horseradish peroxidase on a single molecule level. Objective-type TIR-FCS combines ...

2007

Dual-beam heterodyne Fourier domain optical coherence tomography

Adrian Bachmann, Theo Lasser, Roland Michaely, Rainer Leitgeb

We report on a novel method combining achromatic complex FDOCT signal reconstruction with a common path and dual beam configuration. The complex signal reconstruction allows resolving the complex ambiguity of the Fourier transform and to enhance the achiev ...

2007

Vectorial reconstruction of retinal blood flow in three dimensions measured with high resolution resonant Doppler Fourier domain optical coherence tomography

Adrian Bachmann, Theo Lasser, Roland Michaely, Martin Villiger, Cédric Blatter, Rainer Leitgeb

Resonant Doppler Fourier domain optical coherence tomography (FDOCT) is a functional imaging tool for extracting tissue flow. The method is based on the effect of interference fringe blurring in spectrometer-based FDOCT, where the path difference between s ...

SPIE Society of Photo-optical Instrumentation Engineers2007

Complex Ambiguity-Free Fourier Domain Optical Coherence Tomography through Transverse Scanning

Theo Lasser, Roland Michaely, Rainer Leitgeb

We introduce a simple and cheap method for phase-shifting Fourier domain optical coherence tomography (FDOCT) that does not need additional devices and can easily be implemented. A small beam offset at the fast beam-scanning mirror introduces a causal phas ...

OSA2007

Vectorial retinal blood flow and optical vessel vivisection for 3D angiography with high resolution resonant Doppler OCT

Adrian Bachmann, Theo Lasser, Roland Michaely, Martin Villiger, Cédric Blatter, Rainer Leitgeb

PURPOSE: To perform high speed and completely non-invasive 3D angiography at the optic nerve head region and to reconstruct vectorial 3D blood flow from optically segmented blood vessel structure as a pre-requisite for testing retinal function and physiolo ...

2007

Field confinement with aberration correction for solid immersion lens based fluorescence correlation spectroscopy

Theo Lasser, Jelena Mitic, Ramachandra Rao, Rainer Leitgeb

The solid immersion lens (SIL) as a tool for increasing the field confinement as well as providing optimal performance by aberration compensation in a confocal fluorescence correlation spectroscopy (FCS) system is illustrated here. Using Zernike polynomial ...

2007

Intensity based quantification of fast retinal blood flow in 3D via high resolution resonant Doppler spectral OCT

Adrian Bachmann, Theo Lasser, Roland Michaely, Martin Villiger, Cédric Blatter, Rainer Leitgeb

Resonant Doppler Fourier Domain Optical Coherence Tomography is a functional imaging modality for quantifying fast tissue flow. The method profits from the effect of interference fringe blurring in spectrometer-based FDOCT in the presence of sample motion. ...

Spie-Int Soc Optical Engineering, Po Box 10, Bellingham, Wa 98227-0010 Usa2007

Optical imaging apparatus for sample imaging method e.g. in-vivo measurement of full three-dimensional tissue volume has at least one detector that detects resulting spectral interference pattern at exit of interferometer

Adrian Bachmann, Theo Lasser, Lukas Steinmann, Martin Villiger, Rainer Leitgeb

The invention concerns an optical imaging apparatus comprising (o) a light source (1) , (p) sample holding means, (q) an interferometer, (r) reference means, (s) an objective (8) which is adapted to have its sample side focal plane crossing a sample held i ...

2007

Image formation in fluorescence coherence-gated imaging through scattering media

Theo Lasser, Rainer Leitgeb

Recently, we have experimentally demonstrated a new form of cross-sectional, coherence-gated fluorescence imaging referred to as SD-FCT (‘spectral-domain fluorescence coherence tomography’). Imaging in SD-FCT is accomplished by spectrally detecting self-in ...

2007

Resonant Doppler flow imaging and optical vivisection of retinal blood vessels

Adrian Bachmann, Theo Lasser, Martin Villiger, Cédric Blatter, Rainer Leitgeb

For Fourier domain optical coherence tomography any sample movement during camera integration causes blurring of interference fringes and as such reduction of sensitivity for flow detection. The proposed method overcomes this problem by phase-matching a re ...

2007

Fast focus field calculations

Marcel Leutenegger, Theo Lasser, Ramachandra Rao, Rainer Leitgeb

We present a fast calculation of the electromagnetic field near the focus of an objective with a high numerical aperture (NA). Instead of direct integration, the vectorial Debye diffraction integral is evaluated with the fast Fourier transform for calculat ...

2006

An all-fiber Pr/Yb-doped up-conversion laser in different laser operation modes

Marcel Zeller, Hans Georg Limberger, Theo Lasser

Fiber laser systems have the potential to represent an interesting alternative to more conventional laser sources emitting in the visible spectral range. In this contribution we present new results based on fluoride Pr/Yb- doped fiber systems. This Pr/Yb-d ...

2006

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