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Infinity Focus
In optics and photography, infinity focus is the state where a lens or other optical system forms an image of an object an infinite distance away. This corresponds to the point of focus for parallel rays. The image is formed at the focal point of the lens. In simple two lens systems such as a refractor telescope, the object at infinity forms an image at the focal point of the objective lens, which is subsequently magnified by the eyepiece. The magnification is equal to the focal length of the objective lens divided by the focal length of the eyepiece. In practice, not all photographic lenses are capable of achieving infinity focus by design. A lens used with an adapter for close-up focusing, for example, may not be able to focus to infinity. Failure of the human eye to achieve infinity focus is diagnosed as myopia. All optics are subject to manufacturing tolerances; even with perfect manufacture, optical trains experience thermal expansion. Focus mechanisms must accommodat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Objective Lens
In optical engineering, an objective is an optical element that gathers light from an object being observed and focuses the light rays from it to produce a real image of the object. Objectives can be a single lens or mirror, or combinations of several optical elements. They are used in microscopes, binoculars, telescopes, cameras, slide projectors, CD players and many other optical instruments. Objectives are also called object lenses, object glasses, or objective glasses. Microscope objectives The objective lens of a microscope is the one at the bottom near the sample. At its simplest, it is a very high-powered magnifying glass, with very short focal length. This is brought very close to the specimen being examined so that the light from the specimen comes to a focus inside the microscope tube. The objective itself is usually a cylinder containing one or more lenses that are typically made of glass; its function is to collect light from the sample. Magnification One of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Hyperfocal Distance
In optics and photography, hyperfocal distance is a distance from a lens beyond which all objects can be brought into an "acceptable" focus. As the hyperfocal distance is the focus distance giving the maximum depth of field, it is the most desirable distance to set the focus of a fixed-focus camera. The hyperfocal distance is entirely dependent upon what level of sharpness is considered to be acceptable. The hyperfocal distance has a property called "consecutive depths of field", where a lens focused at an object whose distance from the lens is at the hyperfocal distance will hold a depth of field from to infinity, if the lens is focused to , the depth of field will be from to ; if the lens is then focused to , the depth of field will be from to , etc. Thomas Sutton and George Dawson first wrote about hyperfocal distance (or "focal range") in 1867. Louis Derr in 1906 may have been the first to derive a formula for hyperfocal distance. Rudolf Kingslake wrote in 1951 about ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Operating Temperature
An operating temperature is the allowable temperature range of the local ambient environment at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the maximum operating temperature (or peak operating temperature). Outside this range of safe operating temperatures the device may fail. It is one component of reliability engineering. Similarly, biological systems have a viable temperature range, which might be referred to as an "operating temperature". Ranges Most semiconductor devices are manufactured in several temperature grades. Broadly accepted grades are: *Commercial: 0 °C to 70 °C () *Industrial: −40 °C to 85 °C () *Military: −55 °C to 125 °C () Nevertheless, each manufacturer defines its own temperature grades so designers must pay attention to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Mars Orbiter Camera
The Mars Orbiter Camera and Mars Observer Camera (MOC) were scientific instruments on board the Mars Observer and Mars Global Surveyor spacecraft. The camera was built by Malin Space Science Systems (MSSS) for NASA and the cost of the whole MOC scientific investigation project was about US$44 million, higher than anticipated in the budget. Design Originally named Mars Observer Camera, it was selected by NASA in 1986 for the Mars Observer mission, but it returned only three images of planet Mars before the loss of the spacecraft in 1993. A second camera of the same specifications, renamed to Mars Orbiter Camera (MOC), was built (with assistance by California Institute of Technology) and launched on board the Mars Global Surveyor (MGS) spacecraft in 1996. The camera returned 243,668 images while in orbit around Mars, before the loss of the MGS spacecraft in 2006. Mars Orbiter Camera was operated by its manufacturer, Malin Space Science Systems, from its facilities in San Diego, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Thermal Expansion
Thermal expansion is the tendency of matter to increase in length, area, or volume, changing its size and density, in response to an increase in temperature (usually excluding phase transitions). Substances usually contract with decreasing temperature (thermal contraction), with rare exceptions within limited temperature ranges ('' negative thermal expansion''). Temperature is a monotonic function of the average molecular kinetic energy of a substance. As energy in particles increases, they start moving faster and faster, weakening the intermolecular forces between them and therefore expanding the substance. When a substance is heated, molecules begin to vibrate and move more, usually creating more distance between themselves. The relative expansion (also called strain) divided by the change in temperature is called the material's coefficient of linear thermal expansion and generally varies with temperature. Prediction If an equation of state is available, it can be used t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Myopia
Myopia, also known as near-sightedness and short-sightedness, is an eye condition where light from distant objects focuses in front of, instead of on, the retina. As a result, distant objects appear blurry, while close objects appear normal. Other symptoms may include headaches and eye strain. Severe myopia is associated with an increased risk of macular degeneration, retinal detachment, cataracts, and glaucoma. Myopia results from the length of the eyeball growing too long or less commonly the lens being too strong. It is a type of refractive error. Diagnosis is by the use of cycloplegics during eye examination. Tentative evidence indicates that the risk of myopia can be decreased by having young children spend more time outside. This decrease in risk may be related to natural light exposure. Myopia can be corrected with eyeglasses, contact lenses, or by refractive surgery. Eyeglasses are the simplest and safest method of correction. Contact lenses can provide a rela ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Photographic Lens
A camera lens, photographic lens or photographic objective is an optical lens (optics), lens or assembly of lenses (compound lens) used in conjunction with a camera body and mechanism to Imaging, make images of objects either on photographic film or on other media capable of storing an image Photosensitivity, chemically or Image sensor, electronically. There is no major difference in principle between a lens used for a still camera, a video camera, a telescope, a microscope, or other apparatus, but the details of design and construction are different. A lens might be permanently fixed to a camera, or it might be interchangeable lens camera, interchangeable with lenses of different focal lengths, apertures, and other properties. While in principle a simple lens, simple convex lens will suffice, in practice a compound lens made up of a number of optical lens elements is required to correct (as much as possible) the many optical aberrations that arise. Some aberrations will be prese ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Refractor Telescope
A refracting telescope (also called a refractor) is a type of optical telescope that uses a lens (optics), lens as its objective (optics), objective to form an image (also referred to a dioptrics, dioptric telescope). The refracting telescope design was originally used in spyglasses and astronomy, astronomical telescopes but is also used for long-focus lens, long-focus camera lenses. Although large refracting telescopes were very popular in the second half of the 19th century, for most research purposes, the refracting telescope has been superseded by the reflecting telescope, which allows larger apertures. A refractor's magnification is calculated by dividing the focal length of the objective lens by that of the eyepiece. Refracting telescopes typically have a lens at the front, then a optical train, long tube, then an eyepiece or instrumentation at the rear, where the telescope view comes to focus. Originally, telescopes had an objective of one element, but a century later, tw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Optics
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of optical instruments, instruments that use or Photodetector, detect it. Optics usually describes the behaviour of visible light, 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 electromagnetism, 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 Ray (optics), rays that travel in straight lines and bend when they pass through or reflect from surfaces. Physical optics is a more comprehensive mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Focus (optics)
In geometrical optics, a focus, also called an image point, is a point where ray (optics), light rays originating from a point on the object vergence (optics), converge. Although the focus is conceptually a point, physically the focus has a spatial extent, called the circle of confusion, blur circle. This non-ideal focusing may be caused by optical aberration, aberrations of the imaging optics. Even in the absence of aberrations, the smallest possible blur circle is the Airy disc caused by diffraction from the optical system's aperture; diffraction is the ultimate limit to the light focusing ability of any optical system. Aberrations tend to worsen as the aperture diameter increases, while the Airy circle is smallest for large apertures. An image, or image point or region, is in focus if light from object points is converged almost as much as possible in the image, and defocus aberration, out of focus if light is not well converged. The border between these is sometimes define ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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Image
An image or picture is a visual representation. An image can be Two-dimensional space, two-dimensional, such as a drawing, painting, or photograph, or Three-dimensional space, three-dimensional, such as a carving or sculpture. Images may be displayed through other media, including a Projector, projection on a surface, activation of electronic signals, or Display device, digital displays; they can also be reproduced through mechanical means, such as photography, printmaking, or Photocopier, photocopying. Images can also be Animation, animated through digital or physical processes. In the context of signal processing, an image is a distributed amplitude of color(s). In optics, the term ''image'' (or ''optical image'') refers specifically to the reproduction of an object formed by light waves coming from the object. A ''volatile image'' exists or is perceived only for a short period. This may be a reflection of an object by a mirror, a projection of a camera obscura, or a scene d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |