Development of an optical multi-purpose sensor using filtered scattered light

Abstract

We present the development of an optical sensor head which consists of a confocal backscatter arrangement of lenses and light guiding fibers. Using a molecular absorption cell which contains iodine vapor different scatter techniques are employed to obtain multiple flow field parameters in different media like gas and liquids. For velocity measurements filtered Mie scattering is used and validation experiments with a free jet yield an absolute error of 2m/s. In gaseous flows the sensor applies filtered Rayleigh scattering to determine temperature values with an accuracy of +/-3K and pressure values which show a systematic deviation of -2% from reference measurements. Finally filtered Brillouin scattering is introduced for measuring the temperature in liquids like tap water. This technique agrees within 1K when compared to a conventional thermo element measurement.