We present an optical card reader optimised for robustness in portable applications. Parallel readout and minimal mechanical movement are key ingredients of this system.
KEYWORDS: Skin, Two photon excitation microscopy, In vivo imaging, Collagen, Confocal laser scanning microscopy, 3D image processing, Microscopy, Confocal microscopy, Image analysis, 3D acquisition
We present results from 2D Fourier analysis on 3D stacks of images obtained by confocal laser scanning reflectance microscopy (CLSM) and two-photon fluorescence microscopy (2PM) on human skin in vivo. CLSM images were obtained with a modified commercial system (Vivascope1000, Lucid Inc, excitation wavelength 830 nm) equipped with a piezo-focusing element (350 μm range) for depth positioning of the objective lens. 2PM was performed with a specially designed set-up with excitation wavelength 730 nm. Mean cell size in the epidermal layer and structural orientation in the dermal layer have been determined as a function of depth by 2D Fourier analysis. Fourier analysis on microscopic images enables automatic non-invasive quantitative structural analysis (mean cell size and orientation) of living human skin.
We present a system for in-vivo skin imaging consisting of a two-photon fluorescence and a confocal reflectance video microscope. The two devices share one microscope objective, but have separate light sources, detectors, scan-units and control electronics. This makes it possible to image a region of the skin using the two different modalities, while exploiting the specific advantages of each method.
In the images we clearly distinguish several skin layers, i.e., stratum corneum, viable epidermis, basal layer and upper dermis. Close to the skin surface individual keratinocytes in the stratum corneum are visible with the two-photon microscope, while in reflectance images the texture is much more uniform. Slightly deeper in the skin the smooth cellular structure of the epidermis becomes visible for both imaging modalities. Below the basal layer, which marks the boundary between epidermis and the dermis, fibrous structure appears which can be attributed to capillary vessels and dermal collagen.
We use the combined imaging device for studying the effect of occlusion on human skin. From the fluorescence images we observe swelling of the stratum corneum, while the reflectance microscope shows changes in the scattering properties due to hydration. We show that by combining two microscopes in one we can obtain images that contain complementary information, thereby enhancing the potential for each individual modality.
KEYWORDS: Skin, Luminescence, Microscopes, In vivo imaging, 3D image processing, Two photon excitation microscopy, Confocal microscopy, Reflectivity, Absorption, Collagen
We present images of human skin obtained by a two-photon fluorescence microscope, which has been optimized for in- vivo imaging. Using autofluorescence as a contrast mechanism various layers of the skin, e.g., stratum corneum, viable epidermis, basal layer and upper dermis could be clearly distinguished. A comparison between two-photon fluorescence images and reflectance images shows that there is a clear difference in the information content provided by both techniques. In particular, the fluorescence images of the dermis show detail that is absent in the reflectance images.
We present a detailed device characterization of a series of optically pumped VCSELs, emphasizing in particular a comparison with electrically pumped devices. We conclude that fundamental device parameters such as threshold pump power, input-output efficiency and polarization behavior do not depend on the pumping scheme.
Vertical-cavity surface-emitting lasers (VCSELs) are a new type of semiconductor laser with intriguing properties. As the small cavity ensures single longitudinal mode operation, the VCSEL mode structure is fully determined by the transverse spatial profile combined with the polarization behavior. After discussing some general ideas behind mode formation in VCSELs, we present a number of experiments performed to obtain the relevant numbers for practical AlGaAs-GaAs devices. These include measurements of: the (polarization-resolved) light output-versus-current characteristic, far-field patterns, the wavefront curvature inside a VCSEL, a spectral analysis of spontaneous emission below and above threshold, and a study of the influence of an axial magnetic field. This article contains a relatively large number of equations and experimental and literature values to make it more useful for later reference. Of course it is difficult to tell how specific some of these numbers are related to the particular planar VCSELs we have investigated.
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