In this paper, we have investigated on the potentialities of digital holography for whole reconstruction of wavefields. We show that this technique can be efficiently used for obtaining quantitative information from the intensity and the phase distributions of the reconstructed field at different locations along the propagation direction. The basic concept and procedure of wavefield reconstruction for digital in-line holography is discussed. Numerical reconstructions of the wavefield from digitally recorded in-line hologram patterns and from simulated test patterns are presented. The potential of the method for analysing aberrated wave front has been exploited by applying the reconstruction procedure to astigmatic hologram patterns.

In microscopy, high magnifications are achievable for investigating micro-objects but the paradigm is that higher is the required magnification, lower is the depth of focus. For an object having a three-dimensional (3D) complex shape only a portion of it appears in good focus to the observer who is essentially looking at a single image plane. Actually, two approaches exist to obtain an extended focused image, both having severe limitations since the first requires mechanical scanning while the other one requires specially designed optics. We demonstrate that an extended focused image of an object can be obtained through digital holography without any mechanical scanning or special optical components. The conceptual novelty of the proposed approach lies in the fact that it is possible to completely exploit the unique feature of DH in extracting all the information content stored in hologram, amplitude and phase, to extend the depth of focus.

Digital holographic microscopy (DHM) can be described as a non-invasive metrological tool for inspection and characterization of microelectromechanical structures (MEMS). DHM is a quick, non-contact and non-invasive technique that can offer a high resolution in both lateral and vertical directions. It has been employed for the characterization of the undesired out-of-plane deformations due to the residual stresses introduced by technological processes. The characterization of these deformations is helpful in studying and understanding the effect of residual stress on the deformation of a single microstructure. To that end, MEMS with different geometries and shapes, such as cantilever beams, bridges and membranes, have been characterized. Moreover, DHM has been applied efficiently to evaluate variations of the structure profile due to some external effects. As an example, the characterization of a cantilever subjected to a thermal process has been described. The results reported show that DHM is a useful non-invasive method for characterizing and developing reliable MEMS.

An approach that uses an electro-optically tunable two dimensional phase grating to enhance the resolution in digital holographic microscopy is proposed. We show that, by means of a flexible hexagonal phase grating, it is possible to increase the numerical aperture of the imaging system, thus improving the spatial resolution of the images in two dimensions. The augment of the numerical aperture of the optical system is obtained by recording spatially multiplexed digital holograms. The grating tuneability allows one to adjust the intensity among the spatially multiplexed holograms maximizing the grating diffraction efficiency. Furthermore we demonstrate that the flexibility of the numerical reconstruction allows one to use selectively the diffraction orders carrying useful information for increasing the spatial resolution. The proposed approach can improve the capabilities of digital holography in three-dimensional imaging and microscopy.

Lens effect was obtained in an open microfluidic system by using a thin layer of liquid on a polar electric crystal like LiNbO3. An array of liquid micro-lenses was generated by electrowetting effect in pyroelectric periodically poled crystals. Compared to conventional electrowetting devices, the pyroelectric effect allowed to have an electrode-less and circuit-less configuration. An interferometric technique was used to characterize the curvature of the micro-lenses and the corresponding results are presented and discussed. The preliminary results concerning the imaging capability of the micro-lens array are also reported.