Simulation analysis of in-line digital holography for particles measurement

In particle measurement, in-line holography is widely used. The main advantage is that the setup is very simple, and the reconstruction process is convenient. The process of particle measurement using digital holography was numerically simulated. Two different numerical methods, direct Fourier transform algorithm and convolution algorithm, were analyzed and compared. It is shown that the convolution algorithm tallies with the practice requirement. The spatial spectra of the recorded image and its requirement for sampling frequency of the image are analyzed, from which the smallest recording distance under certain wavelength and sampling interval is obained. For an image with 512×512 pixels, if the size of one pixel is 6.7 μm and the wavelength is 532 nm, the minimum distance is 43.2 mm.