Management of the axial modulation of the illumination pattern in structured illumination microscopy using an extended illumination source.

We have designed and implemented an approach for three-dimensional (3D) structured illumination (SI) microscopy (SIM) based on a quasi-monochromatic extended source illuminating a Wollaston prism to improve robustness, light efficiency and flexibility over our previous design. We show through analytical and experimental verification of the presented theoretical framework for our proposed tunable structured illumination microscopy (TSIM) system, that a simple and accurate determination of the axial modulation of the SI pattern is achieved, enabling a realistic characterization of the system's effective optical transfer function (OTF). System performance as a function of the extended source size is investigated with simulations. Results from a comparative performance analysis of the proposed TSIM system and traditional SIM systems show some advantages over the traditional two-wave and three-wave interference SIM systems. We show that by controlling the source size and thereby the axial modulation of the 3D SI pattern, the TSIM scheme offers increased OTF compact support and improved optical sectioning capability, quantified by the integrated intensity, under certain conditions, which may be desirable when imaging optically thick samples. The additional tunability of the 3D SI pattern, provides a unique opportunity for OTF engineering in our TSIM system.

Resolution enhancement in integral microscopy by physical interpolation.

Integral-imaging technology has demonstrated its capability for computing depth images from the microimages recorded after a single shot. This capability has been shown in macroscopic imaging and also in microscopy. Despite the possibility of refocusing different planes from one snap-shot is crucial for the study of some biological processes, the main drawback in integral imaging is the substantial reduction of the spatial resolution. In this contribution we report a technique, which permits to increase the two-dimensional spatial resolution of the computed depth images in integral microscopy by a factor of √2. This is made by a double-shot approach, carried out by means of a rotating glass plate, which shifts the microimages in the sensor plane. We experimentally validate the resolution enhancement as well as we show the benefit of applying the technique to biological specimens.