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Dark Field Microscopy
Dark-field microscopy, also called dark-ground microscopy, describes microscopy methods, in both light microscopy, light and electron microscopy, which exclude the unscattered beam from the image. Consequently, the field around the specimen (i.e., where there is no specimen to scattering, scatter the beam) is generally dark. In optical microscopes a darkfield Condenser (optics), condenser lens must be used, which directs a cone of light away from the objective lens. To maximize the scattered light-gathering power of the objective lens, oil immersion is used and the numerical aperture (NA) of the objective lens must be less than 1.0. Objective lenses with a higher NA can be used but only if they have an adjustable diaphragm, which reduces the NA. Often these objective lenses have a NA that is variable from 0.7 to 1.25. Light microscopy applications In optical microscopy, dark-field describes an lighting, illumination technique used to enhance the contrast (vision), contrast in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Red Blood Cells By Darkfield Microscopy
Red is the color at the long wavelength end of the visible spectrum of light, next to Orange (colour), orange and opposite Violet (color), violet. It has a dominant wavelength of approximately 625–750 nanometres. It is a primary color in the RGB color model and a secondary color (made from magenta and yellow) in the CMYK color model, and is the complementary color of cyan. Reds range from the brilliant yellow-tinged Scarlet (color), scarlet and Vermilion, vermillion to bluish-red crimson, and vary in shade from the pale red pink to the dark red burgundy (color), burgundy. Red pigment made from ochre was one of the first colors used in prehistoric art. The Ancient Egyptians and Mayan civilization, Mayans colored their faces red in ceremonies; Roman Empire, Roman generals had their bodies colored red to celebrate victories. It was also an important color in China, where it was used to color early pottery and later the gates and walls of palaces. In the Renaissance, the brillian ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Condenser Lens
A condenser is an optical lens that renders a divergent light beam from a point light source into a parallel or converging beam to illuminate an object to be imaged. Condensers are an essential part of any imaging device, such as microscopes, enlargers, slide projectors, and telescopes. The concept is applicable to all kinds of radiation undergoing optical transformation, such as electrons in electron microscopy, neutron radiation, and synchrotron radiation optics. Microscope condenser Condensers are located above the light source and under the sample in an upright microscope, and above the stage and below the light source in an inverted microscope. They act to gather light from the microscope's light source and concentrate it into a cone of light that illuminates the specimen. The aperture and angle of the light cone must be adjusted (via the size of the diaphragm) for each different objective lens with different numerical apertures. Condensers typically consist of a variabl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polarization (waves)
, 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 el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polarized Light 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 H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Attenuation Coefficient
The linear attenuation coefficient, attenuation coefficient, or narrow-beam attenuation coefficient characterizes how easily a volume of material can be penetrated by a beam of light, sound, particles, or other energy or matter. A coefficient value that is large represents a beam becoming 'attenuated' as it passes through a given medium, while a small value represents that the medium had little effect on loss. The (derived) SI unit of attenuation coefficient is the reciprocal metre (m−1). Extinction coefficient is another term for this quantity, often used in meteorology and climatology. Most commonly, the quantity measures the exponential decay of intensity, that is, the value of downward ''e''-folding distance of the original intensity as the energy of the intensity passes through a unit (''e.g.'' one meter) thickness of material, so that an attenuation coefficient of 1 m−1 means that after passing through 1 metre, the radiation will be reduced by a factor of '' e'', and fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bright-field Microscopy
Bright-field microscopy (BF) is the simplest of all the optical microscopy illumination techniques. Sample illumination is transmitted (i.e., illuminated from below and observed from above) white light, and contrast in the sample is caused by attenuation of the transmitted light in dense areas of the sample. Bright-field microscopy is the simplest of a range of techniques used for illumination of samples in light microscopes, and its simplicity makes it a popular technique. The typical appearance of a bright-field microscopy image is a dark sample on a bright background, hence the name. History of microscopy Compound microscopes first appeared in Europe around 1620. The actual inventor of the compound microscope is unknown although many claims have been made over the years. These include a dubious claim that Dutch spectacle-maker Zacharias Janssen invented the compound microscope and the telescope as early as 1590. Another claim is that Janssen's competitor Hans Lippersh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scattered Radiation
In physics, scattering is a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including particles and radiation) in the medium through which they pass. In conventional use, this also includes deviation of reflected radiation from the angle predicted by the law of reflection. Reflections of radiation that undergo scattering are often called ''diffuse reflections'' and unscattered reflections are called '' specular'' (mirror-like) reflections. Originally, the term was confined to light scattering (going back at least as far as Isaac Newton in the 17th century). As more "ray"-like phenomena were discovered, the idea of scattering was extended to them, so that William Herschel could refer to the scattering of "heat rays" (not then recognized as electromagnetic in nature) in 1800. John Tyndall, a pioneer in light scattering research, noted the connec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tissue Paper
Tissue paper, or simply tissue, is a lightweight paper or light crêpe paper. Tissue can be made from recycled pulp (paper), paper pulp on a paper machine. Tissue paper is very versatile, and different kinds are made to best serve these purposes, which are hygienic tissue paper, facial tissues, paper towels, as packing material, among other (sometimes creative) uses. The use of tissue paper is common in developed nations, around 21 million tonnes in North America and 6 million in Europe, and is growing due to urbanization. As a result, the industry has often been scrutinized for deforestation. However, more companies are presently using more recycled fibres in tissue paper. Properties The key properties of tissues are absorbency, basis weight, thickness, bulk (specific volume), brightness, stretch, appearance and comfort. Production Tissue paper is produced on a Fourdrinier machine, paper machine that has a single large steam heated drying cylinder (Yankee dryer) fitted with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High-pass Filter
A high-pass filter (HPF) is an electronic filter that passes signals with a frequency higher than a certain cutoff frequency and attenuates signals with frequencies lower than the cutoff frequency. The amount of attenuation for each frequency depends on the filter design. A high-pass filter is usually modeled as a linear time-invariant system. It is sometimes called a low-cut filter or bass-cut filter in the context of audio engineering. High-pass filters have many uses, such as blocking DC from circuitry sensitive to non-zero average voltages or radio frequency devices. They can also be used in conjunction with a low-pass filter to produce a band-pass filter. In the optical domain filters are often characterised by wavelength rather than frequency. High-pass and low-pass have the opposite meanings, with a "high-pass" filter (more commonly "short-pass") passing only ''shorter'' wavelengths (higher frequencies), and vice versa for "low-pass" (more commonly "long-pass"). De ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spatial Frequency
In mathematics, physics, and engineering, spatial frequency is a characteristic of any structure that is periodic across position in space. The spatial frequency is a measure of how often sinusoidal components (as determined by the Fourier transform) of the structure repeat per unit of distance. The SI unit of spatial frequency is the reciprocal metre (m−1), (11 pages) although cycle (rotational unit), cycles per (c/m) is also common. In image-processing applications, spatial freque ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bright-field Microscopy
Bright-field microscopy (BF) is the simplest of all the optical microscopy illumination techniques. Sample illumination is transmitted (i.e., illuminated from below and observed from above) white light, and contrast in the sample is caused by attenuation of the transmitted light in dense areas of the sample. Bright-field microscopy is the simplest of a range of techniques used for illumination of samples in light microscopes, and its simplicity makes it a popular technique. The typical appearance of a bright-field microscopy image is a dark sample on a bright background, hence the name. History of microscopy Compound microscopes first appeared in Europe around 1620. The actual inventor of the compound microscope is unknown although many claims have been made over the years. These include a dubious claim that Dutch spectacle-maker Zacharias Janssen invented the compound microscope and the telescope as early as 1590. Another claim is that Janssen's competitor Hans Lippersh ... [...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] |
