**5. Conclusion**

In this chapter, an alternative methodology for image reconstruction and object analysis in digital holographic microscopy is discussed. The model we use for image reconstruction is specific for digital holographic microscopy; it includes a first propagation from the hologram plane to obtain the Fourier Transform plane of the object at the back focal plane of the microscope objective lens and then a second propagation is applied to find out the image wave field at the reconstruction plane. Using digital hologram reconstruction as a method for calculating the amplitude and intensities distributions of the optical field on the Fourier Transform plane microscopic objects with regular forms are studied. Random and periodical distributions of objects are considered. The lineal dimensions of the objects are determined by manipulating the diffraction pattern in a simple and accurate way. The advantages of this methodology are summarized as follows: (a) using a single hologram the phase image is calculated with simple operation for phase curvature correction, (b) there are no limitations in the minimum reconstruction distance, (c) capability to maintain the size of a reconstructed image, independent of the reconstruction distance and wavelength for objects larger than a CCD, and (d) the spectral analysis of the radial intensity curve of the Fraunhofer diffraction pattern allows the determination of the lineal dimensions of the objects.
