Digital holographic microscopy (DHM), is a combination of digital holography and microscopy. It is capable of tracking transparent objects, such as organelles of living cells, without the use of fluorescent markers. The main problem of DHM is to increase an image spatial resolution while maintaining a wide field of view. The main approaches to solving this problem are: increasing of the numerical aperture of lighting and recording systems, as well as using deep learning methods. Increasing the numerical aperture of lighting systems is achieved by using oblique, structured or speckle illumination. For recording systems it is achieved by using hologram extrapolation, synthesis or super-resolution. Deep learning is usually used in conjunction with other methods to shorten the compute time. This article is dedicated to describe the basic principles and features of the above approaches.

Keywords: digital holographic microscopy, spatial resolution, field of view, numerical aperture, sample, light beam, CCD camera, diffraction, imaging system, super-resolution