Petra Dancová, Pavel Psota, Tomáš Vít
Limits of Digital Holographic Interferometry used for Measurement of Temperature Fields
Holographic interferometry (HI) is an optical measurement method that combines the principles of holography and classical interferometry. Compared to classical interferometry, two significant benefits are achieved. The first advantage is the ability to measure diffuse reflecting surfaces of objects, but this is not a matter of phase measurement. The second advantage is the fact that this is a differential technique. In principle, holographic interferometry, similar to classical interferometry, measures the change in the optical path of two waves. However, in classical interferometry, both optical paths of the interferometer must be optically equivalent, which means minimal difference in optical paths at each point. The resulting interferometric pattern is a combination of the measured deviation and variance introduced by the interferometer. Both deviations cannot be distinguished from one another. For this reason, the interferometer must be composed of highly accurate optical components and adjusted with high precision. In the case of HI, an initial reference state is recorded at first, than it is compared to the changed (in the optical point of view) state of the object. The optical inequality of both paths does not play a role and does not affect the measurement result. Digital holographic interferometry, compared with HI, uses numerical reconstruction of a hologram which is recorded on a digital camera. The presented paper shows an overview of different modes and configurations of digital holographic interferometry (DHI) for precise measurement of temperature fields in fluids. It shows basic equations used for evaluation of achieved results and for the reconstruction of temperature fields. The paper shows basic configuration of interferometers (Mach-Zehnder and Twyman-Green) used for DHI. Paper also brings analysis of physical limits of the experimental method.
Temperature measurement, digital holographic interferometry, limits
Cite this paper
Petra Dancová, Pavel Psota, Tomáš Vít. (2018) Limits of Digital Holographic Interferometry used for Measurement of Temperature Fields. International Journal of Applied Physics, 3, 55-60