Phase compensation in Digital Holography Microscopy

Digital Holography Microscopy (DHM) is a powerful tool for three-dimensional imaging of micro-objects, since it yields an intensity image, called hologram. This is interference pattern, records the intensity information and allow reconstruction of the phase shift introduced by objects. With the development of computer and fast Fourier transformation technology, DHM has been widely used in biological and material tissues, etc.. In this paper, DHM is used to measure the abrupt edges and surface of reflect objects which are calibrated. Phase compensation uses the physical configuration to compensate the phase aberration, such as Microscope Objective (MO), spherical aberration and other curvature introduced by specimen or instruments in set-up. We apply this method to obtain the pure holograms of objects. The holograms produce more accurate phase-contrast imaging and three-dimensional imaging. Angular Spectrum Propagation (ASP) approach is a strict diffraction integration, and widely used for many applications, such as short-distance propagation, and the off-axis system and tilted plane. Here, we achieve numerical reconstruction of the hologram with ASP under phase compensation condition in an off-axis system.First, we use the fast Fourier transformation for the hologram and get the frequency image. Then, filter out the spectrum about the image which we need. Finally, inverse Fourier transform of the filtered spectrum and get the complex amplitude information. The phase image and intensity image of specimen is obtained after calculating the reconstruction distance.