19 July 1996 Scanning laser speckle photography for temperature field measurement in fluid flows
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This paper describes a scanning laser speckle photography (SLSP) measurement system which is an advancement of a standard laser speckle photography (LSP) technique. The new SLSP set-up enlarges the measuring area of a conventional LSP which is restricted to the used optical expansion/collimation system. This is done by a mechanical movement of a set of mirrors in the beam path of a small expanded laser beam by a precise computer-controlled XY- positioner. Thus the magnitude of the measuring area is enlarged from the relative small cross section of the expanded/collimated laser beam to the movement distance of the positioner. Furthermore an additional advantage of the SLSP is the decrease of the exposure time for a specklegram due to the increased laser light intensity of a small expanded laser beam. The established SLSP measurement set-up is used to investigate the temperature field in a thermal boundary layer of a natural convection flow of air around a slender heated vertical cylindrical tube. Therefore the axis-symmetrical temperature field of the heated tube is vertically scanned by the moved laser beam and a specklegram is fixed on a holographic film by a double-exposure. The optical SLSP arrangement is described in detail and first experimental results of temperature measurements with the SLSP are presented.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Rudi Kulenovic, Yaozu Song, Manfred Groll, "Scanning laser speckle photography for temperature field measurement in fluid flows", Proc. SPIE 2861, Laser Interferometry VIII: Applications, (19 July 1996); doi: 10.1117/12.245160; https://doi.org/10.1117/12.245160

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