A new branch of research, dedicated to lightfield, has recently seen an important growth in the microscopist community and it is called integral or lightfield microscopy. One recent implementation of a lightfield microscope is the Fourier integral Microscope (FiMic). In this setup a microlens array (MLA) is placed at the Fourier plane of the objective lens, therefore, the sensor behind each microlens is capturing the spatial information of a different perspective of the sample. The spatio-angular information captured can used to reconstruct the 3D volume. A very wide field of research among microscopists is for objects that have an extremely low contrast or that are completely transparent. In order to obtain a 3D reconstruction of a transparent sample our work has been focused on the combination of the FiMic with a dark-field illumination. In this way a 3D reconstruction of phase objects is achieved.
Lately, Integral-Imaging systems have shown very promising capabilities of capturing the 3D structure of micro- scopic and macroscopic scenes. The aim of this work is to provide an optimal design for 3D-integral microscopy with extended depth of field and enhanced lateral resolution. By placing an array of microlenses at the aperture stop of the objective, this setup provides a set of orthographic views of the 3D sample. Adopting well known integral imaging reconstruction algorithms it can be shown that the depth of field as well as spatial resolution are improved with respect to conventional integral microscopy imaging. Our claims are supported on theoretical basis and experimental images of a resolution test target, and biological samples.
Three-dimensional imaging is affected by depth-induced spherical aberration (SA) when imaging deep into an optically thick sample. In this work, we evaluate the impact of SA on the performance of incoherent grating-projection structured illumination microscopy (SIM). In particular, we analyze the reduction of the contrast in the structured pattern and compare the reconstructed SIM images for different amounts of SA. In order to mitigate the impact of SA, we implement and evaluate in SIM a wavefront encoded imaging system using a square cubic (SQUBIC) phase mask, an approach shown previously to be successful in conventional microscopy.
Integral Imaging is well known for its capability of recording both the spatial and the angular information of threedimensional (3D) scenes. Based on such an idea, the plenoptic concept has been developed in the past two decades, and therefore a new camera has been designed with the capacity of capturing the spatial-angular information with a single sensor and after a single shot. However, the classical plenoptic design presents two drawbacks, one is the oblique recording made by external microlenses. Other is loss of information due to diffraction effects. In this contribution report a change in the paradigm and propose the combination of telecentric architecture and Fourier-plane recording. This new capture geometry permits substantial improvements in resolution, depth of field and computation time
Integral imaging (InI) is a 3D auto-stereoscopic technique that captures and displays 3D images. We present a method for easily projecting the information recorded with this technique by transforming the integral image into a plenoptic image, as well as choosing, at will, the field of view (FOV) and the focused plane of the displayed plenoptic image. Furthermore, with this method we can generate a sequence of images that simulates a camera travelling through the scene from a single integral image. The application of this method permits to improve the quality of 3D display images and videos.
Usual problem in 3D integral-imaging monitors is flipping that happens when the microimages are seen from neighbor microlenses. This effect appears when, at high viewing angles, the light rays emitted by any elemental image are not passing through the corresponding microlens. A usual solution of this problem is to insert and a set of physical barriers to avoid this crosstalk. In this contribution we present a pure optical alternative of physical barriers. Our arrangement is based on Köhler illumination concept, and avoids that the rays emitted by one microimage to impinge the neighbor microlens. The proposed system does not use additional lenses to project the elemental images, so no optical aberrations are introduced.
In this contribution we propose the use of a liquid lens (LL) to perform three-dimensional (3D) imaging. Our proposed method consists on inserting the LL at the aperture stop of telecentric microscopes. The sequential depth images of 3D samples are obtained by tuning the focal length of LL. Our experimental results demonstrate that fast-axial scanning of microscopic images is obtained without varying neither the resolution capability nor the magnification of the imaging system. Furthermore, this non-mechanical approach can be easily implemented in any commercial optical microscope.