Optical microscope | EPFL Graph Search

The optical microscope, also referred to as a light microscope, is a type of microscope that commonly uses visible light and a system of lenses to generate magnified images of small objects. Optical microscopes are the oldest design of microscope and were possibly invented in their present compound form in the 17th century. Basic optical microscopes can be very simple, although many complex designs aim to improve resolution and sample contrast. The object is placed on a stage and may be directly viewed through one or two eyepieces on the microscope. In high-power microscopes, both eyepieces typically show the same image, but with a stereo microscope, slightly different images are used to create a 3-D effect. A camera is typically used to capture the image (micrograph). The sample can be lit in a variety of ways. Transparent objects can be lit from below and solid objects can be lit with light coming through (bright field) or around (dark field) the objective lens. Polarised light m

Scanning Near-Field Optical Microscopy of Living Cells in Liquid, Elaboration of New SNOM Probes and Detection Methods

Kanat Dukenbayev

The aim of the present PhD thesis is the elaboration of new, home-made Scanning Near-field Optical Microscope (SNOM or NSOM), and the demonstration of its great potential for high-resolution topography and fluorescence investigations of soft and solid samples, as well as the possibility to work in air and liquid environments showing high-resolution topographical and fluorescence abilities to investigate soft and solid samples. The first chapter starts from with the description of the general idea of SNOM and with a brief introduction into to the history and theory of optical image formation, and leading to the resolution limits in conventional optical microscopy. The following section will discuss about the different state-of-the-art different SNOM configurations and theirs peculiarities. The second chapter discusses the SNOM instrumentation and its operation in liquid. The central idea of the proposed approach is the application of the "joint recipient principle" method. Then we will describe the double-resonance principle of the SNOM sensor, and the preparation of glass optical fibers by chemical etching. In addition, the description of the important technical components (lasers, filter and so on) for the SNOM experiment concludes this chapter. The third chapter focus is on the time-gated pulse excitation and optical signal detection of SNOM images. The technical configuration of the SNOM is presented in more details. The fourth chapter starts from with a broad overview of living bacteria Escherichia coli (E.coli) and of the Green Synechococcus – type of Picocyanobacteria cell lines, and presents the distinctive advantages for of the SNOM investigations working in native physiological conditions. The following sections emphasize our obtained high-resolution experimental SNOM result measurements, then followed a discussion of the results follows. The sample preparation and deposition procedures of the living cells for the scanning will are also discussed in this chapter. The chapter five introduces our recently developed SNOM sensor, based on polymethylmethacrylate (PMMA) plastic optical fiber. The chemical preparation of sharp (>100 nm) tips, and its significant advantages will be illustrated by experimental results.

EPFL2011

Experimental investigation on the moment-rotation performance of pultruded FRP web-flange junctions

Gisele Góes Cintra, Thomas Keller

This paper aims to present an experimental investigation on the behavior of web-flange junctions (WFJs) rotational stiffness of pultruded fiber-reinforced polymer composites (FRP). Channels and I-sections were tested using a simple set-up, which was developed in order to experimentally characterize the junctions in a direct manner. The Digital Image Correlation (DIC) technique was used, allowing overall deflections and relative rotations between web and flange to be monitored. The WFJs' imperfections were analyzed through an optical microscope and correlated with the cracks' formation. Further, damage thresholds are identified using available stress equations for curved composite members and lower bound functions are proposed to simulate the junction stiffness retention. Finally, two Equations are developed in order to analytically predict pultruded junctions' rotational stiffness per unit of width. In general, the theoretical and experimental results agreed fairly well, with a maximum difference of 24% for I-sections and 38% for channels.

ELSEVIER SCI LTD2021

Scanning Near-Field Optical Microscopy of Living Cells in Liquid, Elaboration of New SNOM Probes and Detection Methods

Kanat Dukenbayev

EPFL2011