Light microscopy image interpretation

The replication methods described have a basic limitation in that they are all negative impressions of the specimen, which is a major factor in image interpretation. Wood [434] developed a method to provide positive replicas of polymer fiber surfaces. Polymer fibers often have surface coatings, such as finishes in textile fibers, that aid handling but may be volatile in the SEM. However, reflected light microscopy, at high magnifications, reveals only a portion of the curved surface at any one level of focus. Therefore, the depth of focus of the SEM is required. 

As to the near future of HREM and the imaging of light elements in electron microscopy, we can announce that we have just installed a new CM30-FEG-Ultra twin microscope at the EMAT laboratory in Antwerp, which is able to produce structural information down to the 1.1 A level. The interpretation of such images in terms of the projected crystal potential is certainly not straightforward, but with the help of CCD recording and computer treatment of the data, we are starting real quantitative HREM [7.84]. 

Fluorescence microscopy offers a number of advantages over other forms of microscopy (c/r. Tables 5.16 and 5.17). Its high sensitivity allows very low concentrations of specific substances to be localised. Because fiuorescence is observed as luminosity on a dark background, fluorescent constituents of the specimen can be seen even in extremely small amounts. Fluorescence microscopy can also be applied to detect particles below the resolution of a light microscope. Since fluorescence involves two wavelength bands (excitation and emission), optical specificity can substantially be increased. Fluorescence microscopy, because of its complexity, gives more difficulty than usual in interpretation of the image. 

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