Expansion of digital holography measurement area in particle field

Digital holography shows great potential in flow field diagnostics due to its non-intrusive and instant three-dimensional and multi-parameter measurement. However, the low spatial resolution of the existing CCD, leading to small measurable area, is one of the limitations. Based on angular distribution of light scattering intensity, expansion of the measurement cross section of digital in-line holography was investigated at the condition of the existing CCD-resolution. Airy disk of forward light scattering of a particle limits the recording of interference pattern with high frequency, reducing the spatial resolution requirement of CCD. The measurement section of a flow field can be expanded by pre-amplification of CCD using imaging. The bigger the particle is, the larger the measurement section can be extended to. Effect of the CCD pixel size on particle measurement with different size was numerically studied, and coal particle flow was measured by digital in-line holography experimentally. Results show that the analysis is reasonable, and that the proposed method expanding the measurement cross-section is feasible.