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Polarized Optical Microscopy
Polarized light microscopy can mean any of a number of optical microscopy techniques involving polarized light. Simple techniques include illumination of the sample with polarized light. Directly transmitted light can, optionally, be blocked with a polariser oriented at 90 degrees to the illumination. More complex microscopy techniques which take advantage of polarized light include differential interference contrast microscopy and interference reflection microscopy. Scientists will often use a device called a polarizing plate to convert natural light into polarized light. These illumination techniques are most commonly used on birefringent samples where the polarized light interacts strongly with the sample and so generating contrast with the background. Polarized light microscopy is used extensively in optical mineralogy. Although the invention of the polarizing microscope is typically attributed to David Brewster around 1815, Brewster clearly acknowledges the priority of Henr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polarizing Microscope
A petrographic microscope is a type of optical microscope used to identify rocks and minerals in thin sections. The microscope is used in optical mineralogy and petrography, a branch of petrology which focuses on detailed descriptions of rocks. The method includes aspects of polarized light microscopy (PLM). __TOC__ Description Depending on the grade of observation required, petrographic microscopes are derived from conventional brightfield microscopes of similar basic capabilities by: * Adding a Nicol prism polarizer filter to the light path beneath the sample slide * Replacing the normal stage with a circular rotating stage (typically graduated with vernier scales for reading orientations to better than 1 degree of arc) * Adding a second rotatable and removable Nicol prism filter, called the analyzer, to the light path between objective and eyepiece * Adding a phase telescope, also known as a Bertrand lens, which allows the viewer to see conoscopic interference pattern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Microscopy
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviolet, and infrared light. Light is a type of electromagnetic radiation, and other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties. Most optical phenomena can be accounted for by using the classical electromagnetic description of light, however complete electromagnetic descriptions of light are often difficult to apply in practice. Practical optics is usually done using simplified models. The most common of these, geometric optics, treats light as a collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces. Physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cann ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polarized Light
, or , is a property of transverse waves which specifies the geometrical orientation of the oscillations. In a transverse wave, the direction of the oscillation is perpendicular to the direction of motion of the wave. One example of a polarized transverse wave is vibrations traveling along a taut string, for example, in a musical instrument like a guitar string. Depending on how the string is plucked, the vibrations can be in a vertical direction, horizontal direction, or at any angle perpendicular to the string. In contrast, in longitudinal waves, such as sound waves in a liquid or gas, the displacement of the particles in the oscillation is always in the direction of propagation, so these waves do not exhibit polarization. Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, and transverse sound waves ( shear waves) in solids. An electromagnetic wave such as light consists of a coupled oscillating elec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Differential Interference Contrast Microscopy
Differential interference contrast (DIC) microscopy, also known as Nomarski interference contrast (NIC) or Nomarski microscopy, is an optical microscopy technique used to enhance the contrast in unstained, transparent samples. DIC works on the principle of interferometry to gain information about the optical path length of the sample, to see otherwise invisible features. A relatively complex optical system produces an image with the object appearing black to white on a grey background. This image is similar to that obtained by phase contrast microscopy but without the bright diffraction halo. The technique was invented by Francis Hughes Smith. The "Smith DIK" was produced by Ernst Leitz Wetzlar in Germany and was difficult to manufacture. DIC was then developed further by Polish physicist Georges Nomarski in 1952. DIC works by separating a polarized light source into two orthogonally polarized mutually coherent parts which are spatially displaced (sheared) at the sample plane ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interference Reflection Microscopy
Interference reflection microscopy (IRM), also called Reflection Interference Contrast Microscopy (RICM) or Reflection Contrast Microscopy (RCM) depending on the specific optical elements used, is an optical microscopy technique that leverages thin-film interference effects to form an image of an object on a glass surface. The intensity of the signal is a measure of proximity of the object to the glass surface. This technique can be used to study events at the cell membrane without the use of a (fluorescent) label as is the case for TIRF microscopy. History and name In 1964, Adam S. G. Curtis coined the term Interference Reflection Microscopy (IRM), using it in the field of cell biology to study embryonic chick heart fibroblasts. He used IRM to look at adhesion sites and distances of fibroblasts, noting that contact with the glass was mostly limited to the cell periphery and the pseudopodia. In 1975, Johan Sebastiaan Ploem introduced an improvement to IRM (published in a book ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Birefringent
Birefringence, also called double refraction, is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are described as birefringent or birefractive. The birefringence is often quantified as the maximum difference between refractive indices exhibited by the material. Crystals with non-cubic crystal structures are often birefringent, as are plastics under mechanical stress. Birefringence is responsible for the phenomenon of double refraction whereby a ray of light, when incident upon a birefringent material, is split by polarization into two rays taking slightly different paths. This effect was first described by Danish scientist Rasmus Bartholin in 1669, who observed it in Iceland spar (calcite) crystals which have one of the strongest birefringences. In the 19th century Augustin-Jean Fresnel described the phenomenon in terms of polarization, understanding li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Mineralogy
Optical mineralogy is the study of minerals and Rock (geology), rocks by measuring their optics, optical properties. Most commonly, rock and mineral samples are prepared as thin sections or grain mounts for study in the laboratory with a petrographic microscope. Optical mineralogy is used to identify the mineralogical composition of geological materials in order to help reveal their origin and evolution. Some of the properties and techniques used include: * Refractive index * Birefringence * Auguste Michel-Lévy, Michel-Lévy Interference colour chart * Pleochroism * Extinction angle * Conoscopic interference pattern (Interference figure) * Becke line test * Optical relief * Sign of elongation (Length fast vs. length slow) * Wave plate History William Nicol (inventor), William Nicol, whose name is associated with the creation of the Nicol prism, is likely the first to prepare thin slices of mineral substances, and his methods were applied by Henry Thronton Maire Witham (1831) t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
David Brewster
Sir David Brewster Knight of the Royal Guelphic Order, KH President of the Royal Society of Edinburgh, PRSE Fellow of the Royal Society of London, FRS Fellow of the Society of Antiquaries of Scotland, FSA Scot Fellow of the Scottish Society of Arts, FSSA Member of the Institution of Civil Engineers, MICE (11 December 178110 February 1868) was a British scientist, inventor, author, and academic administrator. In science he is principally remembered for his experimental work in physical optics, mostly concerned with the study of the Polarization (waves), polarization of light and including the discovery of Brewster's angle. He studied the birefringence of crystals under compression and discovered photoelasticity, thereby creating the field of optical mineralogy.A. D. Morrison-Low (2004) "Brewster, Sir David (1781–1868)" in ''Oxford Dictionary of National Biography'' For this work, William Whewell dubbed him the "father of modern experimental optics" and "the Johannes Kepler of o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Henry Fox Talbot
William Henry Fox Talbot (; 11 February 180017 September 1877) was an English scientist, inventor, and photography pioneer who invented the salted paper and calotype processes, precursors to photographic processes of the later 19th and 20th centuries. His work in the 1840s on photomechanical reproduction led to the creation of the photoglyphic engraving process, the precursor to photogravure. He was the holder of a controversial patent that affected the early development of commercial photography in Britain. He was also a noted photographer who contributed to the development of photography as an artistic medium. He published '' The Pencil of Nature'' (1844–1846), which was illustrated with original salted paper prints from his calotype negatives and made some important early photographs of Oxford, Paris, Reading, and York. A polymath, Talbot was elected to the Royal Society in 1831 for his work on the integral calculus, and researched in optics, chemistry, electricity and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interference Colour Chart
In optical mineralogy, an interference colour chart, also known as the Michel-Levy chart, is a tool first developed by Auguste Michel-Lévy to identify minerals in thin section using a petrographic microscope. With a known thickness of the thin section, minerals have specific and predictable colours in cross-polarized light, and this chart can help identify minerals. The colours are produced by the difference in speed in the fast and slow rays, also known as ''birefringence''. Usage When using the chart, it is important to remember these tips: *Isotropic and opaque (metallic) minerals cannot be identified this way. *The stage of the microscope should be rotated until maximum colour is found, and therefore, the maximum birefringence. *Each mineral, depending on the orientation, may not exhibit the maximum birefringence. It is important to sample a number of similar minerals in order to get the best value of birefringence. *Uniaxial minerals can look isotropic (always extinct) if ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Petrographic Microscope
A petrographic microscope is a type of optical microscope used to identify Rock (geology), rocks and minerals in thin sections. The microscope is used in optical mineralogy and petrography, a branch of petrology which focuses on detailed descriptions of rocks. The method includes aspects of polarized light microscopy (PLM). __TOC__ Description Depending on the grade of observation required, petrographic microscopes are derived from conventional Bright-field microscopy, brightfield microscopes of similar basic capabilities by: * Adding a Nicol prism polarizer filter to the light path beneath the sample slide * Replacing the normal stage with a circular rotating stage (typically graduated with vernier scales for reading orientations to better than 1 degree of arc) * Adding a second rotatable and removable Nicol prism filter, called the analyzer, to the light path between objective and eyepiece * Adding a phase telescope, also known as a Bertrand lens, which allows the viewer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
