Improving Numerical Aperture in DH Microscopy by 2D Diffraction Grating

In this chapter an approach using a 2D phase grating to enhance the resolution in digital holographic microscopy exploiting the electro-optic effect is proposed. We show that, by means of a tunable lithium niobate 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 enhancement of the numerical aperture of the optical system is obtained by recording spatially multiplexed digital holograms. Furthermore, thanks to the flexibility of the numerical reconstruction process, it is possible to selectively use the diffraction orders carrying useful information for optimizing the diffraction efficiency and to increase the final spatial resolution.