A measurement of direct photon production in 208 Pb+ 208 Pb collisions at 158 A GeV has been carried out in the CERN WA98 experiment. The invariant yield of direct photons in central collisions is extracted as a function of transverse momentum in the interval 0.5 < pT < 4 GeV/c. A significant direct photon signal, compared to statistical and systematical errors, is seen at pT > 1.5 GeV/c. The results constitute the first observation of direct photons in ultrarelativistic heavy-ion collisions which could be significant for diagnosis of quark gluon plasma formation. 25.75.+r,13.40.-f,24.90.+p 1

Three-particle correlations have been measured for identified pi(-) from central 158A GeV Pb+Pb collisions by the WA98 experiment at CERN. A substantial contribution of the genuine three-body correlation has been found as expected for a mainly chaotic and symmetric source.

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A two-wavelength method for endoscopic topography reconstruction is introduced that can be applied to out-of-plane sensitive electronic-speckle-pattern interferometry systems based on rigid endoscope imaging systems. The surface measurement is performed by detection of the phase-difference distribution affected by a change in the applied laser wavelength. Furthermore, the off-axis endoscopic illumination geometry is taken into account by an approximation. Experimental results of the characterization of the endoscopic surface reconstruction technique and the measurement accuracy obtained are described and discussed. Finally, the applicability of the method is demonstrated with results from the topographic reconstruction of a free-form surface.

Holographic interferometric metrology allows a fast, non destructive and quantitative high resolution full field detection of optical path length changes. Furthermore, by utilization of modern CCD sensor technology and digital image processing algorithms an on-line application of these methods even on biological specimens is possible. In combination with a microscopic resolution this offers new possibilities for the detection of variations of shape, micro movements or refractive index changes e. g. for the marker free analysis of cellular samples. Three holographic interferometric systems for microscopy applications based on digital holography, (speckle) interferometry and photorefractive crystals as holographic recording medium are introduced. Results of investigations on test charts and biological samples to characterize and optimize the lateral resolution as well as the resolution of the detected phase difference changes are presented and discussed. Finally, the applicability of the developed measurement techniques on living cells is demonstrated. INTRODUCTIONHolographic and speckle interferometry are well-established and frequently applied tools for non destructive testing (NDT) and the analysis of displacements, movements and vibrations. With a measurement accuracy in sub-micrometer range this methods have already been applied in many fields of industry [1] as well as for biomedical applications [2]. Furthermore, by utilization of modern CCD sensor technology and fast digital image processing an on-line application of these methods even in vivo [3] is possible. Holographic interferometric metrology allows a fast, non-contact and quantitative high resolution full field detection of optical path length changes. This offers in combination with a microscopic resolution new possibilities for the analysis of cellular tissues and cells. In the upcoming fields of life sciences and biophotonics there is a requirement for an optical instrumentation of timely and spatially high resolution analysis, measurement and documentation in microscopic dimensions. Here, applications are of particular interest to get enhanced information about cellular tissues and single cells e. g. the detection of shape variations and refractive index changes as well as the full field analysis of parameters like micro movements or the local distribution of elasticity. Up to the present, such parameters are in general not considered in cellular and sub cellular dimensions although they are already routinely used e. g. for defect detection and tumor diagnostics in the macroscopic scale. In that view, holographic interferometric microscopy tools open up new facilities for a marker free monitoring of life processes and cell manipulation as well as for an automated cell differentiation and feedback systems for growing processes in tissue engineering.For such applications of holographic interferometric metrology, the specific requirements for the analysis of cellular tissues and living cells have to be considered and a lateral resolution in microscop...