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Collimator
A collimator is a device which narrows a beam of particles or waves. To narrow can mean either to cause the directions of motion to become more aligned in a specific direction (i.e., make collimated light or parallel rays), or to cause the spatial cross section of the beam to become smaller (beam limiting device). History The English physicist Henry Kater was the inventor of the floating collimator, which rendered a great service to practical astronomy. He reported about his invention in January 1825. In his report, Kater mentioned previous work in this area by Carl Friedrich Gauss and Friedrich Bessel. Optical collimators In optics, a collimator may consist of a curved mirror or lens with some type of light source and/or an image at its focus. This can be used to replicate a target focused at infinity with little or no parallax. In lighting, collimators are typically designed using the principles of nonimaging optics. Optical collimators can be used to calibrate other ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Reflector Sight
A reflector sight or reflex sight is an optical sight that allows the user to look through a partially reflecting glass element and see an aiming point or some image (helping to aim the device, to which the sight is attached, on the target) superimposed on the field of view. These sights work on the simple optical principle that anything (such as an illuminated reticle) at the focus of a lens or curved mirror will appear to be sitting in front of the viewer at infinity. Reflector sights employ some form of "reflector" to allow the viewer to see the infinity image and the field of view at the same time, either by bouncing the image created by lens off a slanted glass plate, or by using a mostly clear curved glass reflector that images the reticle while the viewer looks through the reflector. Since the reticle image is at infinity, it stays in alignment with the device to which the sight is attached regardless of the viewer's eye position to the sight, removing most of the parallax ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Collimator Sight
A collimator sight is a type of optical sight that allows the user looking into it to see an illuminated aiming point aligned with the device the sight is attached to, regardless of eye position (with little parallax). They are also referred to as collimating sights or "occluded eye gunsight" (OEG). Description The basic layout of a collimator sight is a closed tube with a lens at its open end and a luminous reticle mounted near the closed end at the focus of the lens, creating an optical collimator. The reticle is illuminated by an electronic light source (an incandescent light bulb or, more recently, a light-emitting diode) or by ambient light gathered behind the reticle via an opalescent window or fiber optic light pipe. Collimator sights are a relatively old idea, being used in many forms for almost 100 years. Usage Collimator sights, also known as occluded eye gunsights (OEGs), are designed for use with both eyes open. The user aligns one eye with the sight while the o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Floating Collimator
A Floating collimator was an early collimator widely used in astronomical observations. It was invented by the English physicist and astronomer Captain Henry Kater about 1825. His collimator was meant to replace a level, or plumb-line, in astronomical observations, and to provide a ready and perfectly exact method of determining the position of the horizontal or zenith point on the limb of a circle or zenith sector. Its principle is the invariability, with respect to the horizon, of the position assumed by any object of constant shape and mass floating on a fluid. A floating collimator consists of a rectangular box containing mercury, with a piece of cast iron floating on top. The cast-iron is about twelve inches long, four broad, and half an inch thick, having two short uprights or Y's of equal height on top. The uprights hold a small telescope sighted with crossed wires, or crossed portions of a fine balance-spring (very thin flat metal), set flat-ways, and adjusted very exactl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Collimated Light
A collimated beam of light or other electromagnetic radiation has parallel ray (optics), rays, and therefore will spread minimally as it propagates. A laser beam is an archetypical example. A perfectly collimated light beam, with no beam divergence, divergence, would not disperse with distance. However, diffraction prevents the creation of any such beam. Light can be approximately collimated by a number of processes, for instance by means of a collimator. Perfectly collimated light is sometimes said to be ''focused at infinity''. Thus, as the distance from a point source increases, the spherical wavefronts become flatter and closer to plane waves, which are perfectly collimated. Other forms of electromagnetic radiation can also be collimated. In radiology, X-rays are collimated to reduce the volume of the patient's tissue that is irradiated, and to remove stray photons that reduce the quality of the x-ray image ("film fog"). In scintigraphy, a gamma ray collimator is used in fron ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Reticle
A reticle or reticule, also known as a graticule or crosshair, is a pattern of fine lines or markings built into the eyepiece of an optical device such as a telescopic sight, spotting scope, theodolite, optical microscope or the electronic visual display, screen of an oscilloscope, to provide frame of reference, measurement references during visual inspections. Today, engraved lines or embedded fibers may be replaced by a digital image superimposed on a screen or eyepiece. Both terms may be used to describe any set of patterns used for aiding visual measurements and calibrations, but in modern use ''reticle'' is most commonly used for weapon sight (device), sights, while ''graticule'' is more widely used for non-weapon measuring instruments such as oscilloscope#Graticule, oscilloscope display, astronomic telescopes, microscopes and microscope slide, slides, surveying instruments and other similar devices. There are many variations of reticle pattern; this article concerns its ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Henry Kater
Henry Kater FRS, FRAS (16 April 1777 – 26 April 1835) was a British physicist of German descent. Early life He was born at Bristol. At first he intended to study law; but he gave up the idea on his father's death in 1794. He entered the army, obtaining a commission in the 12th Regiment of Foot, then stationed in India, where he assisted William Lambton in the Great Trigonometric Survey. Failing health obliged him to return to England; and in 1808, then a lieutenant, he entered on a student career at the Senior Division of the new Royal Military College at High Wycombe. Shortly afterwards he was promoted to the rank of captain. In 1814 he retired on half-pay, and devoted the remainder of his life to scientific research. Scientist His first major contribution to science was the comparison of the merits of the Cassegrainian and Gregorian telescopes; Kater determined the latter to be an inferior design. His most substantial work was the invention of Kater's pendulum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphical), foreshortening, nearby objects show a larger parallax than farther objects, so parallax can be used to determine distances. To measure large distances, such as the distance of a planet or a star from Earth, astronomers use the principle of parallax. Here, the term ''Stellar parallax, parallax'' is the semi-angle of inclination between two sight-lines to the star, as observed when Earth is on opposite sides of the Sun in its orbit. These distances form the lowest rung of what is called "the cosmic distance ladder", the first in a succession of methods by which astronomers determine the distances to celestial objects, serving as a basis for other distance measurements in astronomy forming the higher rungs of the ladder. Because parallax ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Photogrammetry
Photogrammetry is the science and technology of obtaining reliable information about physical objects and the environment through the process of recording, measuring and interpreting photographic images and patterns of electromagnetic radiant imagery and other phenomena. While the invention of the method is attributed to Aimé Laussedat, the term "photogrammetry" was coined by the German architect , which appeared in his 1867 article "Die Photometrographie." There are many variants of photogrammetry. One example is the extraction of three-dimensional measurements from two-dimensional data (i.e. images); for example, the distance between two points that lie on a plane parallel to the photographic image plane can be determined by measuring their distance on the image, if the scale (map), scale of the image is known. Another is the extraction of accurate color ranges and values representing such quantities as albedo, specular reflection, Metallicity#Photometric colors, metallicity ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Sight (device)
A sight or sighting device is any gadget, device used to assist in precise visual perception, visual alignment (i.e. ''aiming'') of weapons, surveying instruments, aircraft equipment, optical illumination equipment or larger optical instruments with the intended target. Sights can be a simple set or system of physical markers that serve as visual references for directly aligning the user's line of sight with the target (such as iron sights on firearms), or optical instruments that provide an optically enhanced—often magnification, magnified—target image aligned in the same focus (optics), focus with an aiming point (e.g. telescopic sight, telescopic, reflector sight, reflector and holographic sights). There are also sights that actively project an illuminated point of aim (a.k.a. "hot spot") onto the target itself so it can be observed by anyone with a direct view, such as laser sight (firearms), laser sights and infrared illuminators on some night vision devices, as well as a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Fiduciary Marker
A fiducial marker or fiducial is an object placed in the field of view of an image for use as a point of reference or a measure. It may be either something placed into or on the imaging subject, or a mark or set of marks in the reticle of an optical instrument. Applications Microscopy In high-resolution optical microscopy, fiducials can be used to actively stabilize the field of view. Stabilization to better than 0.1 nm is achievable. Physics In physics, 3D computer graphics, and photography, fiducials are reference points: fixed points or lines within a scene to which other objects can be related or against which objects can be measured. Cameras outfitted with Réseau plates produce these reference marks (also called Réseau crosses) and are commonly used by NASA. Such marks are closely related to the timing marks used in optical mark recognition. Geographical survey Airborne geophysical surveys also use the term "fiducial" as a sequential reference number in the mea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |