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Theo Lasser

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Publications associées (125)

Stochastic Approach to Data Analysis in Fluorescence Correlation Spectroscopy

Theo Lasser, Ramachandra Rao, Rajesh Langoju

Fluorescence correlation spectroscopy (FCS) has emerged as a powerful technique for measuring low concentrations of fluorescent molecules and their diffusion constants. In FCS, the experimental data is conventionally fit using standard local search techniq ...

2006

Phase sensitive Fourier domain optical coherence tomography

Adrian Bachmann, Theo Lasser, Rainer Leitgeb

Optical Coherence Tomography (OCT) is an imaging technique with high axial resolution in the micro-meter-scale range combined with a high sensitivity allowing for example to probe weakly back-scattering structures beneath the surface of biological tissues ...

2006

Dual-color total internal reflection fluorescence cross- correlation spectroscopy

Marcel Leutenegger, Theo Lasser, Rainer Leitgeb

We present the development and first application of a novel dual-color total internal reflection (TIR) fluorescence system for single-molecule coincidence analysis and fluorescence cross-correlation spectroscopy (FCCS). As a performance analysis, we measur ...

SPIE Society of Photo-optical Instrumentation Engineers2006

Heterodyne Fourier domain optical coherence tomography for full range probing with high axial resolution

Adrian Bachmann, Theo Lasser, Rainer Leitgeb

One of the main drawbacks of Fourier domain optical coherence tomography (FDOCT) is the limited measurement depth range. Phase shifting techniques allow reconstructing the complex sample signal resulting in a doubled depth range. In current complex FDOCT r ...

2006

Simultaneous Multicolor Fluorescence Cross-Correlation Spectroscopy to Detect Higher Order Molecular Interactions Using Single Wavelength Laser Excitation

Theo Lasser

Fluorescence cross-correlation spectroscopy is a powerful method for the study of molecular interactions and dynamics in solution and even in living cells. Usually, in the optical setup, either two laser beams have to be superimposed in their respective co ...

2006

Extended focus depth for Fourier domain optical coherence microscopy

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

We report on a new detection scheme for Fourier domain optical coherence microscopy that exhibits high transverse resolution along an axially extended focal range. Nearly constant transverse resolution of ∼1.5 μm along a focal range of 200 μm is experiment ...

2006

Laser perfusion imaging system for acquiring flow-related images of object for medical diagnosis comprises coherent light source and image sensor(s) made by randomly addressed two-dimensional array of integrating photodetectors

Theo Lasser

An instrument for high-speed laser perfusion imaging comprises a laser source, a detector, a signal-processing unit, data memory, and a screen to display the results. A section of the sample surface is illuminated with laser light; the reemitted light from ...

2006

Prism-based multicolor fluorescence correlation spectrometer

Marcel Leutenegger, Theo Lasser

We report the design and application of a prism-based detection system for fluorescence (cross) correlation spectroscopy. The system utilizes a single laser wavelength for the simultaneous excitation of several dyes of different emission spectra. Fluoresce ...

2006

Confining the sampling volume for Fluorescence Correlation Spectroscopy using a sub-wavelength sized aperture

Patrik Willi Hoffmann, Marcel Leutenegger, Alexandre Perentes, Theo Lasser, Olivier Martin

For the observation of single molecule dynamics with fluorescence fluctuation spectroscopy (FFS) very low fluorophore concentrations are necessary. For in vitro measurements, this requirement is easy to fulfill. In biology however, micromolar concentration ...

2006

Continuous Wavelet Transform Ridge Extraction for Spectral Interferometry Imaging

Michael Stefan Daniel Liebling, Michaël Unser, Theo Lasser

The combination of wavelength multiplexing and spectral interferometry allows for the encoding of multidimensional information and its transmission over a mono-dimensional channel; for example, measurements of a surface's topography acquired through a mono ...

SPIE2005

Parallel broadband fluorescent light source for optical coherence tomography

Stéphane Bourquin, René Salathé, Theo Lasser

We present a new light source for parallel Optical Coherence Tomography (OCT) based on multiple waveguides written in Ti:sapphire. Each channel can generate a spectrum of 174 nm bandwidth centered at 772 nm, with an optical power on sample of 30 mu W. A sy ...

2005

Fabrication of arrays of sub-wavelength nano-apertures in an optically thick gold layer on glass slides for optical studies

Benjamin Dwir, Patrik Willi Hoffmann, Ivo Utke, Marcel Leutenegger, Alexandre Perentes, Theo Lasser

We report on the fabrication of two-dimensional arrays of nano-optical apertures in gold layers by electron beam lithography (EBL) on a transparent glass substrate. 30 x 30 μ m(2) large arrays of high aspect ratio sub-wavelength cylinders (400 nm diameter ...

2005

Identification of luminescent molecules comprises fluorescence correlation spectroscopy

Pierre-André Besse, Radivoje Popovic, Alexis Rochas, Theo Lasser

The invention relates to a method and device for identifying luminescent molecules according to the fluorescence correlation spectroscopy method. The inventive method comprising the following steps: a) preparing a sample (12) containing luminescent molecul ...

2005

Time-resolved Hadamard fluorescence imaging

Theo Lasser, Kai Hassler

We present a new concept for fluorescence lifetime imaging (FLIM) based on time-resolved Hadamard imaging (HI). HI allows image acquisition by use of one single-point detector without requiring a moving scanning stage. Moreover, it reduces the influence of ...

2005

UV-induced index changes in undoped fluoride glass

Marcel Zeller, Hans Georg Limberger, Theo Lasser

Undoped fluoride glass slides have been exposed to pulsed 193-nm ultraviolet (UV) irradiation. Their absorption changes have been measured to evaluate UV-induced index changes using Kramers-Kronig relation. A layer-peeling polishing technique was applied t ...

IEEE Institute of Electrical and Electronics Engineers2005

Total internal reflection fluorescence correlation spectroscopy (TIR-FCS) with low background and high count-rate per molecule

Marcel Leutenegger, Theo Lasser, Kai Hassler, Ramachandra Rao

We designed a fluorescence correlation spectroscopy (FCS) system for measurements on surfaces. The system consists of an objective-type total internal reflection fluorescence (TIRF) microscopy setup, adapted to measure FCS. Here, the fluorescence exciting ...

2005

High-speed laser Doppler perfusion imaging using an integrating CMOS image sensor

Theo Lasser

This paper describes the design and the performance of a new high-speed laser Doppler imaging system for monitoring blood flow over an area of tissue. The new imager delivers high-resolution flow images (256 x 256 pixels) every 2 to 10 seconds, depending o ...

2005

Full-field laser Doppler perfusion imaging and monitoring with an intelligent CMOS camera

Theo Lasser

A system for full-field laser Doppler blood flow imaging has been developed and tested on biomedical samples. The new imaging system allows 2D flow maps or monitoring flux signals to be obtained from a plurality of measured points simultaneously by using a ...

2005

Speckle statistics in optical coherence tomography

Boris Clément Karamata, Theo Lasser, Markus Laubscher, Kai Hassler

The two previously reported calculations of the amplitude distribution of speckles in optical coherence tomography, each based on a different mathematical formulation, yield different results. We show that a modification of an initial assumption in one of ...

2005

Parallel dual-color fluorescence cross-correlation spectroscopy using diffractive optical elements

Theo Lasser

Dual-color cross-correlation spectroscopy allows the detection and quantification of labeled biomolecules at ultra-low concentrations, whereby the sensitivity of the assay correlates with the measurement time. We now describe a parallel multifocal dual-col ...

SPIE Society of Photo-optical Instrumentation Engineers2005

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