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Firstly, an approach is proposed for eliminating the tilt phase aberration introduced by the tilt reference wave. It is based on the argument distribution of the hologram spectrum to locate exactly the position of the carrier frequency of the virtual image. This tilt aberration will be corrected by shifting the filtered hologram spectrum to the coordinate origin of the frequency domain, without knowledge of the focal length of the imaging lens or distances in the setup. Then the subsequent quadratic phase aberration compensation is performed only by adjusting a single parameter. The method is demonstrated by the phase contrast imaging of the cervical carcinoma cells.

A key problem for the digital holography is to improve the resolution of digital holographic system. We present a system for long-range digital holographic imaging with improved resolution using synthetic aperture method. Imaging system is formed by three sub-apertures, and each sub-aperture receiver contains independently telescope lenses and a CCD device. Through every sub-aperture system, a hologram is obtained. Subsequently, we numerically reconstruct the intensity image and get a synthetic image with the resolution improved. The theoretical analysis and simulated experiment show that the method is reasonable and efficient.

The single wavelength off-axis reflection digital holographic microscopy (DHM) can be applied in micron optical tomography measurement through the pre-magnification method. The pre-magnifying surface profile of the object is imaged by the lens placed in front of the object to be measured, and then is recorded by the CCD camera. The Reconstructed image can be got through Fresnel Diffraction calculation, the 3D surface shape information of the object was shown after the phase filtering and unwrapping process to the reconstruction image. The result in this experiment proves that off-axis reflection digital holographic microscopy can be applied to actual measurement of micron object, to achieve the tomography without touching or breaking the object.

The lensless Fourier transform digital holography has been widely employed in microscopic imaging. It enables quantitative phase analysis for both reflection and transmission objects. The phase image is obtained in the numerical reconstruction procedure. The in-focus reconstruction distance could be determined according to the extremum of the autofocusing criterion function, which is commonly applied in finding the in-focus amplitude image of the object. Then the reconstruction distance for the phase image is considered to be equal to the one for the amplitude image. When the object is a pure phase sample, such as the living cell, the minimum value of the autofocusing criterion function should be found to determine the in-focus reconstruction distance. However, in the experiment, the in-focus amplitude image is often not an ideal uniform bright field, so this method will result in some deviation. In this contribution, two derivatives-based criterion functions are applied to the phase image directly to accomplish the in-focus phase contrast imaging, which is more intuitive and precise. In our experiments, the set-up of the lensless Fourier transform digital holography is established firstly. Then the living cervical carcinoma cells are detected. The phase aberration is corrected by two-step algorithm. The final autofocusing results verify the algorithm proposed in this paper.

As the lensless Fourier transform digital holography is applied into the microscopic phase-contrast imaging on the live cells, the motion of the cells will lead to the non-coplanarity phenomena between the object and the reference source. This could result in the imaging aberration. An effective and robust autofocus procedure based on the phase distribution is presented in the paper. With the initial measurement of the distance between the reference source and the hologram, the optimum parameters corresponding to the phase-contrast image can be achieved by a single hologram, combined with the linearity fitting. The lensless Fourier transform digital holographic system is built and the experiments on the phase-contrast imaging of the live cervical carcinoma cells are performed. Finally, the good experiment results are demonstrated. Both the theoretical analysis and the experimental investigation verify the feasibility and validity of the automatic procedure for the non-coplanar aberration compensation.