Reflection optical microscopy

Figure 5.14 The microstructure of the set cement is clearly revealed by Nomarski reflectance optical microscopy. Glass particles are distinguished from the matrix by the presence of etched circular areas at the site of the phase-separated droplets (Barry, Clinton Wilson, 1979).

The reflection technique is more limited in resolution and magnification than is transmission. Reflection optical microscopy of adhered surfaces is often revealing, but the very limited depth of field is a severe handicap. Nevertheless, examination of surfaces after testing or failure is a simple, but important, first step in determining locus of failure (see Stress distribution mode of failure). Surface reflectivity of specimens is often improved by deposition of a layer or metal. The reflection microscope is especially useful when operated in dark-field mode, where topographical differences are accentuated. 

The technique of reflectance optical microscopy has proven to be invaluable in the analyses and characterization of fossil fuels, in particular coal materials and petroleum-containing source rocks. The technique involves the measurement of the percentage of white polarized light reflected from a polished surface of a coal specimen using oil immersion and analyzed within the microscope. This percentage value gives a measure of the aromaticity of the carbonaceous matter which constitutes coal and rock materials. Table 2.1 contains specific... 

Fischer U Ch, Durig U T and Pohl D W 1988 Near-field scanning microscopy in reflection Appl. Phys. Lett. 52 249 Cline J A, Barshatzky FI and Isaacson M 1991 Scanned-tip reflection-mode near-field scanning optical microscopy Ultramicroscopy 38 299... 

We use optical microscopy to examine samples at magnifications from about 5x up to approximately l,000x. Samples may be examined using either transmitted or reflected light, depending on the nature of the sample and the information that we are seeking. 

The compensation birefringence measurement is very easily coupled to optical microscopy in the transmission and reflection modes, thus allowing characterizing orientation with a spatial resolution of a few hundreds of nanometers [14]. Polarizing microscopes are widely available and are often used for birefringence studies even if spatial resolution is not required. Objectives specifically designed for cross-polarized microscopy are necessary to avoid artifacts. 

Antiblock additives can be seen on the surface of films using optical microscopy or SEM. Identification can normally be achieved with internal reflection IR spectroscopy (e.g., with a germanium crystal to minimise sampling depth) or using an X-ray attachment with the electron microscope. 

One of the key experimental results leading to the elucidation of this overall structural puzzle involved depolarized reflected light microscopy (DRLM) studies on NOBOW freely suspended films in the high-temperature SmCP phase.48 In the freely suspended films it appears that only one phase is observed, which is assumed to be the phase forming the majority domains in the EO cells. The DRLM experiment provides two key results. First, thin films of any layer number have a uniformly tilted optic axis, suggesting all of the layer interfaces are synclinic. Second, films of even-layer number are nonpolar, while films of odd-layer number are polar, with the polar axis oriented normal to the plane of the director tilt (lateral polarization). 

Optical methods are eminently suitable for imaging, the attractive property of photons being that they do not require vacuum. Hence, imaging under reaction conditions becomes possible. Among the successfully applied methods are infrared imaging (IRI) and reflection anisotropy microscopy (RAM) [72]. We will discuss ellipsomicroscopy for surface imaging (EMSI) in some detail here [74],... 

Figure 1. Pitch coke 500°C., 75% l.t., optical microscopy by reflection on block from microtome X 900 photomontage (a) polarized light without analyzer (b) optical photos taken between crossed nicols...

Optical Microscopy. The reflectance of an anisotropic surface in normal incidence depends on die degree of polarization of the light and the crystalline orientation of the surface in relation to the light vibrations. In polarized light and in the case of an opaque birefracdve crystal, whose absorption coefficients... 

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