Abstract
In this study, an optical system capable of simultaneously grabbing three phase-shifted interferometric images was developed for dynamic temperature field measurements of a thin flame. The polarization phase-shifting technique and a Michelson interferometer that is coupled to a 4-f system with a Ronchi grating placed at the frequency plane are used. This configuration permits the phase-shifted interferograms to be grabbed simultaneously by one CCD. The temperature field measurement is based on measuring the refraction index difference by solving the inverse Abel transform, which requires information obtained by the fringe order localization. The phase map is retrieved by a three-step algorithm. Experimental results of a dynamic thin flame are presented.
Highlights
In phase-shifting techniques, a stepping motor or piezoelectric transducers are normally used to move a reference surface to get the interference fringe images with a relative phase shift
The system presented is based on polarization phase-shifting techniques presented previously,[1,2,3] with the addition of calibration procedures and digital fringe processing techniques in order to accurately measure temperature fields varying in time
The optical setup presented for the optical phase calculation consists of a polarization Michelson interferometer (PMI) that is coupled to a 4-f system with an amplitude grating placed at the Fourier plane (Fig. 1)
Summary
In phase-shifting techniques, a stepping motor or piezoelectric transducers are normally used to move a reference surface to get the interference fringe images with a relative phase shift This takes a period of time, making it susceptible to environmental effects such as ambient vibration or air turbulence, which results in measurement errors. A measurement system that is capable of grabbing three phase-shifted interferometric images instantaneously (or simultaneously) was developed for dynamic temperature measurement over a period of time. The system presented is based on polarization phase-shifting techniques presented previously,[1,2,3] with the addition of calibration procedures and digital fringe processing techniques in order to accurately measure temperature fields varying in time.
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