Optical microscopy fundamentals

Fig. 8. Concentration dependence of ultrasound backscatter signal by plates coated with a layer of targeted microbubbles. Surface concentrations of microbubbles (as observed by bright-field optical microscopy, bottom) increase from left to right. Imaging performed using a fundamental frequency scheme. Samples placed on top of an ultrasound tissue phantom. Reprinted from Advanced Drug Delivery Reviews v. 37, A.L. Klibanov, Targeted delivery of gas-filled microspheres, contrast agents for ultrasound imaging, p. 145. Copyright, 1999, with permission from Elsevier Science...

Optical microscopes have one serious drawback, their resolution, resulting from the fundamental physics of lenses. Lord Rayleigh, over 100 years ago, defined the currently accepted maximum optical lens resolution to be one-half of the wavelength of the imaging radiation. In truth, conventional optical microscopy did not achieve this level of definition mainly because of out-of-focus light. This prevented the observation of atoms and single molecules. 

Techniques of optical microscopy (OM) are well known and often used for the examination of fibers and yams from archaeological textiles. Many texts provide the fundamentals of the technique (e.g. 40-43). Some manuscripts describe the methods that may be employed in the study of archaeological materials in particular (44, 45), while others report the results of optical microscopic examination in identification and characterization of archaeological fibers (e.g., 12, 46). 

Three major advancements in resolution have occurred since Hookes s discovery of the optical microscope in 1665 [46]. In 1873, Ernst Abbe established fundamental criteria for the resolution limit in optical microscopy [47], which did not exceed the range of a couple of 100 nanometers even after the introduction of the confocal optical microscope [43,48]. The invention of the transmission electron microscope by Ernst Ruska in 1933 extended the resolution of microscopes to the nanometer scale [49]. Finally, scanning tunnelling microscopy introduced, by Binnig and Rohrer in 1981, made a breakthrough when atomic... 

B. Hecht, B. Sick, U. P. Wild, V. Deckert, R. Zenobi, O. J. F. Martin and D. W. Pohl, Scanning near-field optical microscopy with aperture probes Fundamentals and applications, J. Chem,. Phys. 112, 7761 (2000). 

Hot-stage microscopy not only benefits from the features of the hot stage but also the quality and accessories of the microscope. It is obvious that this technique also needs some fundamental knowledge of chemical and optical microscopy. In this context, it should be noted that the advantage of hot stages that combine the features of differential thermal analysis (DTA) and optical microscopy are questionable since both the sensitivity of the DTA signal and the microscopic preparation features suffer much from this combination. 

Light microscopy is one of the discipline s primary characterization techniques. It allows the forensic scientist to quickly address that most fundamental question, what does the sample look like before proceeding with more extensive, often destructive, analyses. At all levels of sophistication (from hand lenses to compound microscopes), optical microscopy reveals... 

In this thesis Johanna Bruckner reports the discovery of the lyotropic counterpart of the thermotropic SmC phase. By means of polarizing optical microscopy. X-ray diflfraction and electro-optic experiments she firmly establishes aspects of its stmcture and elucidates its fascinating properties, among them a pronounced polar electro-optic effect, analogous to the ferroelectric switching of its thermotropic counterpart. The helical ground state of this new lyotropic phase raises the fundamental question of how chiral interactions are communicated across layers of disordered and achiral solvent molecules which are located between adjacent... 

The methods of specimen preparation for optical microscopy are various. In fundamental polymer studies, thin films of polymers can be crystallized between a slide and cover slip. In an apparatus such as a hot stage attached to a microscope, the crystallization process can be followed as it occurs. However, two features must be taken into account, firstly that in specimens where large spherulites form, their centres are confined to a narrow plane and are not distributed in depth as they would in a bulk specimen. Also, nucleation of crystal growth may be enhanced on the surface of the slide and cover slip, and transcrystalline layers, rather than the spherulitic structure of the bulk material, may form. 

Hecht B, Sick B, Wild UP, Deckert V, Zenobi R, Martin OJF, Dieter DW (2000) Scanning near-field optical microscopy with aperture probes fundamentals and application. J Chem Phys 18 112... 

This section describes the principals and practical application of Raman scanning nearfield optical microscopy (RSNOM). The fundamental aim of this technique is to obtain Raman spectroscopic data with a spatial resolution much greater than is possible with conventional micro-Raman techniques. 

The fundamental principals underlying the scanning near-field optical microscopy technique (variously referred to as SNOM or NSOM in the literature) are described. The key features of the practical application of RSNOM are discussed, an example RSNOM system is described, and an example application is presented. 

In Fig. 9.1 we sketch the fundamental configuration of the optical antenna used in near-field optical microscopy, i.e. a sharp noble-metal tip approaching the sample surface down to a few... 

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