Digital data-page holograms consisting of 1024 x 1024 arrays of binary pixels have been stored and subsequently retrieved with an optical exposure consistent with a data rate 1 Gbit /s. Each input pixel was precisely registered with a single detector pixel, and a raw bit-error rate as low as 2.4 x 10(-6) was demonstrated with global-threshold detection. To our knowledge, this is the first demonstration of the often-cited goal of holographic data storage of megabit data pages and a gigabit-per-second data rate.
By means of 157 nm VUV short-wavelength laserirradiation the wood layer of damaged cells near the surface as well as deeper wood regions can be removed. As this is a nonthermal laser ablation-process, oxidation of the wood surface exposed to 157 nm under N 2 -atmosphere is avoided even with high power densities. By applying a mechanical pre-treatment process the wood structure is compressed and can then be removed with almost no damage. Four types of wood -spruce, pine, beech and oak -were ablated in all three main cutting directions prescribed for an anisotropic material such as wood. Several microscopic techniques were used. To measure the ablation depth LSM was applied. The surface roughness as well as the quality of the laser ablation was determined by using LV-SEM. CAM was used to measure the contact angle and thereby calculate the surface energy. Ablation can be carried out regardless of the cutting direction used to obtain clean and open surfaces free of artefacts.VUV laser-irradiated surface in contrast to an untreated reference area showing the morphology of the exposed wood structure and thus the quality of the ablation
Schlagwörter: Rauheitsbeurteilung, Speckle-Interferometrie, On-line-Messung, Mikrotopologie, glänzende Oberflächen Bei der Qualitätskontrolle glänzender technischer Oberflächen treten Probleme auf, sobald die Objektgröße ein Mindestmaß unterschreitet oder die Oberfläche gekrümmt ist. Insbesondere die Glanzgradmessung als standardisiertes Verfahren (DIN 67530) setzt einen absolut ebenen und optisch homogenen Oberflächenbereich mit einer Mindestgröße von ca. 5x10 mm voraus. Die vorgestellte Lösung nutzt das Interferenzmuster (Speckies) zweier Laserstrahlen, um den Glanz der Oberfläche zu erfassen. Da Größe und Verteilung der Speckies unmittelbar von der Mikrotopologie der Oberfläche abhängen, lassen sich charakteristische Zusammenhänge eines solchen Interferenzmusters mit verschiedenen optischen Oberflächeneigenschaften (Glanz, Vorzugsrichtung, Reflexionsverhalten) herstellen. Obwohl das Verfahren bildgebend arbeitet, liefert es integrale Kenngrößen über den betrachteten Oberflächenbereich. Es werden das Funktionsprinzip dieser Methode vorgestellt und die damit erreichbaren Vorteile im Vergleich zu herkömmlichen Methoden gezeigt.
Fast Characterization of Glossy Surfaces by Means of Coherent RadiationFast quality control of glossy surfaces causes problems if the objects are too small or the surface is curved. Especially the gloss measuring method corresponding to DIN 67530 assumes a plane and homogeneous surface part with a minimum size of 5x10 mm. The presented solution uses the interference pattern (speckle) of two coherent illumination beams for recognition of surface gloss. As the speckle density depends directly on the microstructure of the surface, the interference pattern is connected with different surface characteristics such as gloss, reflections, and groove directions. Although the method is image-based, it derives statistical values for the interesting surface part in short time. This paper describes the principle of the method and shows the main advantages in comparsion with conventional surface characterization and gloss merasurement techniques.
2881 Einleitung
The wave guiding feature of the optical fibre optical fibres is specifically exploited to construct a novel type of electron gun to realize single-shot low-energy electron diffraction experiments with the sub-picosecond resolution for studying irreversible samples.
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