Influence of some recording parameters on digital holography particle image velocimetry

Abstract

Digital holographic particle image velocimetry (DHPIV) is a promising technique for the measurement of the instantaneous flow velocity within a volume of the flow. Besides problems at illumination and recording which need to be solved, one major issue is, is how to extract the information about the location of the particles within the flow and their displacement between two illuminations out of the storage medium, i.e. the digital hologram. Some recording parameters such as the recording distance z₀, particle size d_p, wavelength λ, the size of the CCD chip H, the pixel size d_pixel and the particle concentration c_p etc, will considerably affect the results of the reconstruction, and may even determine the success or failure of a measurement. This paper discusses the influence of these parameters and presents a formula for the critical recording distance. The numerical simulations indicate that when the recording distance is near to the critical recording distance, the results of the reconstruction are much better than those obtained far away from the critical recording distance, especially for high particle concentration. Also an experiment is made to validate the corresponding analysis.