Label-free quantitative 3D tomographic imaging for partially coherent light microscopy

Crucial benefits provided by partially coherent light microscopy such as improved spatial resolution, optical sectioning and speckle-noise suppression are exploited here to achieve 3D quantitative imaging: reconstruction of the object refractive index (RI). We present a partially coherent optical diffraction tomography technique (PC-ODT) that can be easily implemented in commercially available bright-field microscopes. We show that the high numerical apertures of the objective and condenser lenses, together with optical refocusing, are main issues for achieving fast and successful 3D RI reconstruction of weak objects. In particular, the optical refocusing is performed by a high-speed focus tunable lens mounted in front of the digital camera enabling compatibility with commercial microscopes. The technique is experimentally demonstrated on different examples: diatom cells (biosilica shells), polystyrene micro-spheres and blood cells. The results confirm the straightforward 3D-RI reconstruction of the samples providing valuable quantitative information for their analysis. Thus, the PC-ODT can be considered as an efficient and affordable alternative to coherent ODT which requires specially designed holographic microscopes

IMAGING INTERFEROMETRIC MICROSCOPY TO THE LIMITS OF AVAILABLE FREQUENCY SPACE

Imaging interferometric microscopy (IIM) is a synthetic aperture approach offering the potential of optical resolution to the linear systems limit of optics (~lambda/4n). IIM allows one to resolve structures not accessible in a conventional illumination setup, while using a low NA microscope objective and thus keeping the large working distance, depth of focus and field of view associated with the lower NA. The goal of this dissertation is to reach ultimate resolution limits of non-fluorescent microscopy by using IIM in new optical configurations realizing a solid immersion technique with immersion materials employed in advanced regimes unsuitable in other systems. The immersion advantages of IIM can be realized if the object is in close proximity to a solid-immersion medium. Illumination through the substrate involves photons propagating at angles beyond total internal reflection, collection of high frequencies, and decoupling this radiation by a grating on the medium surface opposite to the object. The spatial resolution as a function of the medium thickness and refractive index as well as the field-of-view of the optical system is derived and applied to simulations. Structural illumination technique allows aliasing high spatial frequency into the low frequency range and using conventional microscopes at high resolution. This technique may be useful for broad swath of technical applications, biological and medical research

Angle-resolved cathodoluminescence imaging polarimetry

Cathodoluminescence spectroscopy (CL) allows characterizing light emission in bulk and nanostructured materials and is a key tool in fields ranging from materials science to nanophotonics. Previously, CL measurements focused on the spectral content and angular distribution of emission, while the polarization was not fully determined. Here we demonstrate a technique to access the full polarization state of the cathodoluminescence emission, that is the Stokes parameters as a function of the emission angle. Using this technique, we measure the emission of metallic bullseye nanostructures and show that the handedness of the structure as well as nanoscale changes in excitation position induce large changes in polarization ellipticity and helicity. Furthermore, by exploiting the ability of polarimetry to distinguish polarized from unpolarized light, we quantify the contributions of different types of coherent and incoherent radiation to the emission of a gold surface, silicon and gallium arsenide bulk semiconductors. This technique paves the way for in-depth analysis of the emission mechanisms of nanostructured devices as well as macroscopic media.Comment: 8 figures. Includes supplementary informatio

Imagen cuantitativa en microscopia 3D con iluminación parcialmente coherente

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Óptica, leída el 28/01/2021The main research objective of this work is to develop and implement a fast and high resolution technique for reconstructing the 3D refractive index (RI) of weakly absorbing samples. This technique is based on the generalization of optical diffraction tomography (ODT), developed for coherent sample illumination (C-ODT), to the partially coherent case (PC-ODT). In contrast to C-ODT, which involves a specially designed holographic microscope, the proposed PC-ODT technique is implemented in conventional wide-field microscope. The incorporation of the required refocusing module is easy and can be done by a final user unfamiliar with optics (i.e. clinicians and biologists). The low coherent illumination provided by high numerical aperture condenser results in high resolution and reduced speckle noise typical for laser sources used in C-ODT...El principal objetivo de esta tesis es desarrollar e implementar una técnica rápida y de alta resolución para la reconstrucción del índice de refracción (IR) 3D de muestras de absorción débil, basada en la generalización de la tomografía de difracción óptica (TDO), desarrollada para iluminación coherente (TDO-C), al caso parcialmente coherente (TDOPC), lo que evita el ruido coherente y otros artefactos de la iluminación coherente (láser). Al contrario que la TDO-C, que requiere microscopios holográficos (típicamente en configuraciones interferométricas fuera de eje), la técnica TDO-PC propuesta se implementa en un microscopio de campo amplio. La incorporación del módulo de reenfoque óptico es sencillo y puede ser realizado por un usuario no familiarizado con la óptica (como médicos y biólogos). La iluminación poco coherente proporcionada por un condensador de alta apertura numérica logra una alta resolución y reducción del ruido coherente (speckle) típico de las fuentes láser utilizadas en TDO-C...Fac. de Ciencias FísicasTRUEunpu

Roadmap on digital holography [Invited]

This Roadmap article on digital holography provides an overview of a vast array of research activities in the field of digital holography. The paper consists of a series of 25 sections from the prominent experts in digital holography presenting various aspects of the field on sensing, 3D imaging and displays, virtual and augmented reality, microscopy, cell identification, tomography, label-free live cell imaging, and other applications. Each section represents the vision of its author to describe the significant progress, potential impact, important developments, and challenging issues in the field of digital holography

Improving Range Estimation of a 3D FLASH LADAR via Blind Deconvolution

The purpose of this research effort is to improve and characterize range estimation in a three-dimensional FLASH LAser Detection And Ranging (3D FLASH LADAR) by investigating spatial dimension blurring effects. The myriad of emerging applications for 3D FLASH LADAR both as primary and supplemental sensor necessitate superior performance including accurate range estimates. Along with range information, this sensor also provides an imaging or laser vision capability. Consequently, accurate range estimates would also greatly aid in image quality of a target or remote scene under interrogation. Unlike previous efforts, this research accounts for pixel coupling by defining the range image mathematical model as a convolution between the system spatial impulse response and the object (target or remote scene) at a particular range slice. Using this model, improved range estimation is possible by object restoration from the data observations. Object estimation is principally performed by deriving a blind deconvolution Generalized Expectation Maximization (GEM) algorithm with the range determined from the estimated object by a normalized correlation method. Theoretical derivations and simulation results are verified with experimental data of a bar target taken from a 3D FLASH LADAR system in a laboratory environment. Additionally, among other factors, range separation estimation variance is a function of two LADAR design parameters (range sampling interval and transmitted pulse-width), which can be optimized using the expected range resolution between two point sources. Using both CRB theory and an unbiased estimator, an investigation is accomplished that finds the optimal pulse-width for several range sampling scenarios using a range resolution metric

Fourier ptychography: current applications and future promises

Traditional imaging systems exhibit a well-known trade-off between the resolution and the field of view of their captured images. Typical cameras and microscopes can either “zoom in” and image at high-resolution, or they can “zoom out” to see a larger area at lower resolution, but can rarely achieve both effects simultaneously. In this review, we present details about a relatively new procedure termed Fourier ptychography (FP), which addresses the above trade-off to produce gigapixel-scale images without requiring any moving parts. To accomplish this, FP captures multiple low-resolution, large field-of-view images and computationally combines them in the Fourier domain into a high-resolution, large field-of-view result. Here, we present details about the various implementations of FP and highlight its demonstrated advantages to date, such as aberration recovery, phase imaging, and 3D tomographic reconstruction, to name a few. After providing some basics about FP, we list important details for successful experimental implementation, discuss its relationship with other computational imaging techniques, and point to the latest advances in the field while highlighting persisting challenges

Simulation-based Planning of Machine Vision Inspection Systems with an Application to Laser Triangulation

Nowadays, vision systems play a central role in industrial inspection. The experts typically choose the configuration of measurements in such systems empirically. For complex inspections, however, automatic inspection planning is essential. This book proposes a simulation-based approach towards inspection planning by contributing to all components of this problem: simulation, evaluation, and optimization. As an application, inspection of a complex cylinder head by laser triangulation is studied

A Fringe Projection System for Measurement of Condensing Fluid Films in Reduced Gravity

The thesis describes the design of a fringe projection system to study the dynamics of condensation with potential application in a reduced gravity environment. The concept is that an optical system for imaging the condensation layer enables extraction of valuable data from the image because of the ability of the optical system to image the perturbations in the condensation films. By acquiring a sequence of images of the deformed fringe pattern, the change in the surface topology can be observed over time, giving greater understanding of condensation dynamics in reduced gravity