Multi-wavelength, handheld laser speckle imaging for skin evaluation.

Objective: A handheld device was developed and qualified for in vivo human skin evaluation using laser speckle imaging technology.

Methods: Each laser speckle device prototype allows the choice of up to three different laser wavelengths in the range of 400 nm to 800 nm in total. Speckle pattern analysis gives various speckle parameters, for example, speckle contrast, speckle size, speckle modulation or fractal dimension.

Spectral imaging based on 2D diffraction patterns and a regularization model.

We present a variational approach to reconstruct a multispectral image from an array of diffraction patterns captured in one monochromatic image. The mathematical model relies on the superposition of wavelength dependent calibration diffraction patterns and a spectral regularization with second order differences. The necessary preprocessing steps which influence the mathematical setting are discussed in detail.

A compact microscope setup for multimodal nonlinear imaging in clinics and its application to disease diagnostics.

The past years have seen increasing interest in nonlinear optical microscopic imaging approaches for the investigation of diseases due to the method's unique capabilities of deep tissue penetration, 3D sectioning and molecular contrast. Its application in clinical routine diagnostics, however, is hampered by large and costly equipment requiring trained staff and regular maintenance, hence it has not yet matured to a reliable tool for application in clinics. In this contribution implementing a novel compact fiber laser system into a tailored designed laser scanning microscope results in a small footprint easy to use multimodal imaging platform enabling simultaneously highly efficient generation and acquisition of second harmonic generation (SHG), two-photon excited fluorescence (TPEF) as well as coherent anti-Stokes Raman scattering (CARS) signals with optimized CARS contrast for lipid imaging for label-free investigation of tissue samples.

Packed domain Rayleigh-Sommerfeld wavefield propagation for large targets.

For applications in the domain of digital holographic microscopy, we present a fast algorithm to propagate scalar wave fields from a small source area to an extended, parallel target area of coarser sampling pitch, using the first Rayleigh-Sommerfeld diffraction formula. Our algorithm can take full advantage of the fast Fourier transform by decomposing the convolution kernel of the propagation into several convolution kernel patches. Using partial overlapping of the patches together with a soft blending function, the Fourier spectrum of these patches can be reduced to a low number of significant components, which can be stored in a compact sparse array structure.

Optimal transformations for optical multiplex measurements in the presence of photon noise.

Hadamard multiplexing is a measurement strategy that yields best sensitivity improvements over scanning measurements for signal-independent detector noise. The presence of photon noise degrades the performance of Hadamard multiplexing because of the increase of photon noise by the superposition of multiple signals. I derive the reduction of the sensitivity gain of a Hadamard measurement and an upper limit for the gain of any cyclic multiplexing strategy in the presence of photon noise.