Abstract: This paper presents advanced time average digital holography by means of frequency shift and phase modulation. This technique can measure amplitudes of vibrations at ultimate dynamic range while the amplitude distribution evaluation is done independently in every pixel. The main focus of the paper is to gain insight into behavior of the method at low amplitudes of vibrations. In order to reach that, a set of experiments was performed. Results of the experiments together with novel noise suppression show the limit of the method to be below 0.1 nm.
Abstract: The presented paper shows the possibility of using
holographic interferometry for measurement of temperature field in
moving fluids. There are a few methods for identification of velocity
fields in fluids, such us LDA, PIV, hot wire anemometry. It is very
difficult to measure the temperature field in moving fluids. One of the
often used methods is Constant Current Anemometry (CCA), which
is a point temperature measurement method. Data are possibly
acquired at frequencies up to 1000Hz. This frequency should be
limiting factor for using of CCA in fluid when fast change of
temperature occurs. This shortcoming of CCA measurements should
be overcome by using of optical methods such as holographic
interferometry. It is necessary to employ a special holographic setup
with double sensitivity instead of the commonly used Mach-Zehnder
type of holographic interferometer in order to attain the parameters
sufficient for the studied case. This setup is not light efficient like the
Mach-Zehnder type but has double sensitivity. The special technique
of acquiring and phase averaging of results from holographic
interferometry is also presented. The results from the holographic
interferometry experiments will be compared with the temperature
field achieved by methods CCA method.