Imaging and Measurement of Microscopic Object by Digital Holographic Microscopy

Digital holography is a new three-dimensional imaging technology. Quantitative phase reconstruction is the unique advantage of digital holography. Phase reconstruction of microstructure object based on digital holography and digital lateral shearing interferometry was analyzed and simulated. A method to eliminate the linear term of the sheared phase map was proposed. The results show that the standard one-dimensional phase unwrapping must be applied to the original phase map before lateral shearing. It is also shown that when the small amount of shearing is applied the two-dimensional unwrapping process can be avoided even in case of a large phase change. Moreover, the autofocus method for pure phase object was discussed. The weighted Fourier spectral function, the gradient square function and the modified standard deviation correlation function, which get the minimum value at the focus plane, are available in digital holographic autofocus.