By contrast, the minimum aperture does not depend on the focal length – it is limited by how narrowly the aperture closes, not the lens design – and is instead generally chosen based on practicality: very small apertures have lower sharpness due to diffraction at aperture edges, while the added depth of field is not generally useful, and thus there is generally little benefit in using such apertures. Accordingly, DSLR lens typically have minimum aperture of f/16, f/22, or f/32, while large format may go down to f/64, as reflected in the name of Group f/64. Depth of field is a significant concern in macro photography, however, and there one sees smaller apertures. For example, the Canon MP-E 65mm can have effective aperture (due to magnification) as small as f/96. The pinhole optic for Lensbaby creative lenses has an aperture of just f/177.[13]

Doctors Roth and Reuss, of Vienna, used bent glass rods to illuminate body cavities in 1888. French engineer Henry Saint-Rene designed a system of bent glass rods for guiding light images seven years later in an early attempt at television. In 1898, American David Smith applied for a patent on a dental illuminator using a curved glass rod.

Though as early as 1933 Torkel Korling had invented and patented for the Graflex large format reflex camera an automatic aperture control,[14] not all early 35mm single lens reflex cameras had the feature. With a small aperture, this darkened the viewfinder, making viewing, focusing, and composition difficult.[15] Korling's design enabled full-aperture viewing for accurate focus, closing to the pre-selected aperture opening when the shutter was fired and simultaneously synchronising the firing of a flash unit. From 1956 SLR camera manufacturers separately developed automatic aperture control (the Miranda T 'Pressure Automatic Diaphragm', and other solutions on the Exakta Varex IIa and Praktica FX2) allowing viewing at the lens's maximum aperture, stopping the lens down to the working aperture at the moment of exposure, and returning the lens to maximum aperture afterward.[16] The first SLR cameras with internal ("through-the-lens" or "TTL") meters (e.g., the Pentax Spotmatic) required that the lens be stopped down to the working aperture when taking a meter reading. Subsequent models soon incorporated mechanical coupling between the lens and the camera body, indicating the working aperture to the camera for exposure while allowing the lens to be at its maximum aperture for composition and focusing;[16] this feature became known as open-aperture metering.

The first all-optic fiber cable, TPC-5, that uses optical amplifiers was laid across the Pacific Ocean in 1996. The following year the Fiber Optic Link Around the Globe (FLAG) became the longest single-cable network in the world and provided the infrastructure for the next generation of Internet applications.

Zoom lenses typically have a maximum relative aperture (minimum f-number) of f/2.8 to f/6.3 through their range. High-end lenses will have a constant aperture, such as f/2.8 or f/4, which means that the relative aperture will stay the same throughout the zoom range. A more typical consumer zoom will have a variable maximum relative aperture since it is harder and more expensive to keep the maximum relative aperture proportional to the focal length at long focal lengths; f/3.5 to f/5.6 is an example of a common variable aperture range in a consumer zoom lens.

For some lenses, including a few long telephotos, lenses mounted on bellows, and perspective-control and tilt/shift lenses, the mechanical linkage was impractical,[16] and automatic aperture control was not provided. Many such lenses incorporated a feature known as a "preset" aperture,[16][17] which allows the lens to be set to working aperture and then quickly switched between working aperture and full aperture without looking at the aperture control. A typical operation might be to establish rough composition, set the working aperture for metering, return to full aperture for a final check of focus and composition, and focusing, and finally, return to working aperture just before exposure. Although slightly easier than stopped-down metering, operation is less convenient than automatic operation. Preset aperture controls have taken several forms; the most common has been the use of essentially two lens aperture rings, with one ring setting the aperture and the other serving as a limit stop when switching to working aperture. Examples of lenses with this type of preset aperture control are the Nikon PC Nikkor 28 mm f/3.5 and the SMC Pentax Shift 6×7 75 mm f/4.5. The Nikon PC Micro-Nikkor 85 mm f/2.8D lens incorporates a mechanical pushbutton that sets working aperture when pressed and restores full aperture when pressed a second time.

Typical ranges of apertures used in photography are about f/2.8 – f/22 or f/2 – f/16,[7] covering six stops, which may be divided into wide, middle, and narrow of two stops each, roughly (using round numbers) f/2 – f/4, f/4 – f/8, and f/8 – f/16 or (for a slower lens) f/2.8 – f/5.6, f/5.6 – f/11, and f/11 – f/22. These are not sharp divisions, and ranges for specific lenses vary.

Professional lenses for some movie cameras have f-numbers as small as f/0.75. Stanley Kubrick's film Barry Lyndon has scenes shot by candlelight with a NASA/Zeiss 50mm f/0.7,[12] the fastest lens in film history. Beyond the expense, these lenses have limited application due to the correspondingly shallower depth of field (DOF) – the scene must either be shallow, shot from a distance, or will be significantly defocused, though this may be the desired effect.

Some individuals are also able to directly exert manual and conscious control over their iris muscles and hence are able to voluntarily constrict and dilate their pupils on command.[28] However, this ability is rare and potential use or advantages are unclear.

Shallow depth of field is achieved by shooting photographs with a low f-number to let in more light. Learn more about shallow depth of field today.

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Where the two equivalent forms are related via the f-number N = f / D, with focal length f and entrance pupil diameter D.

The laser was introduced in 1958 as a efficient source of light. The concept was introduced by Charles Townes and Arthur Schawlow to show that masers could be made to operate in optical and infrared regions. Basically, light is reflected back and forth in an energized medium to generate amplified light as opposed to excited molecules of gas amplified to generate radio waves, as is the case with the maser. Laser stands for “light amplification by stimulated emission of radiation.”

The iris controls the size of the pupil via two complementary sets muscles, the sphincter and dilator muscles, which are innervated by the parasympathetic and sympathetic nervous systems respectively, and act to induce pupillary constriction and dilation respectively. The state of the pupil is closely influenced by various factors, primarily light (or absence of light), but also by emotional state, interest in the subject of attention, arousal, sexual stimulation,[24] physical activity,[25] accommodation state,[26] and cognitive load.[27] The field of view is not affected by the size of the pupil.

The terms scanning aperture and sampling aperture are often used to refer to the opening through which an image is sampled, or scanned, for example in a Drum scanner, an image sensor, or a television pickup apparatus. The sampling aperture can be a literal optical aperture, that is, a small opening in space, or it can be a time-domain aperture for sampling a signal waveform.

Today, a variety of industries including the medical, military, telecommunication, industrial, data storage, networking, and broadcast industries are able to apply and use fiber optic technology in a variety of applications.

In 1961, Elias Snitzer of American Optical published a theoretical description of single mode fibers whose core would be so small it could carry light with only one wave-guide mode. Snitzer was able to demonstrate a laser directed through a thin glass fiber which was sufficient for medical applications, but for communication applications the light loss became too great.

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Alexander Graham Bell patented an optical telephone system called the photophone in 1880. His earlier invention, the telephone, proved to be more realistic however. That same year, William Wheeler invented a system of light pipes lined with a highly reflective coating that illuminated homes by using light from an electric arc lamp placed in the basement and directing the light around the home with the pipes.

Fiberoptic connector

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Also in 1954, the “maser” was developed by Charles Townes and his colleagues at Columbia University. Maser stands for “microwave amplification by stimulated emission of radiation.”

Aperture Science, a fictional company in the Portal fictional universe, is named after the optical system. The company's logo heavily features an aperture in its logo, and has come to symbolize the series, fictional company, and the Aperture Science Laboratories Computer-Aided Enrichment Center that the game series takes place in.[33]

In 1960, the first continuously operating helium-neon gas laser is invented and tested. That same year an operable laser was invented which used a synthetic pink ruby crystal as the medium and produced a pulse of light.

The lens aperture is usually specified as an f-number, the ratio of focal length to effective aperture diameter (the diameter of the entrance pupil). A lens typically has a set of marked "f-stops" that the f-number can be set to. A lower f-number denotes a greater aperture which allows more light to reach the film or image sensor. The photography term "one f-stop" refers to a factor of √2 (approx. 1.41) change in f-number which corresponds to a √2 change in aperture diameter, which in turn corresponds to a factor of 2 change in light intensity (by a factor 2 change in the aperture area).

fiberoptic中文

In light microscopy, the word aperture may be used with reference to either the condenser (that changes the angle of light onto the specimen field), field iris (that changes the area of illumination on specimens) or possibly objective lens (forms primary images). See Optical microscope.

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In digital photography, the 35mm-equivalent aperture range is sometimes considered to be more important than the actual f-number. Equivalent aperture is the f-number adjusted to correspond to the f-number of the same size absolute aperture diameter on a lens with a 35mm equivalent focal length. Smaller equivalent f-numbers are expected to lead to higher image quality based on more total light from the subject, as well as lead to reduced depth of field. For example, a Sony Cyber-shot DSC-RX10 uses a 1" sensor, 24 – 200 mm with maximum aperture constant along the zoom range; f/2.8 has equivalent aperture range f/7.6, which is a lower equivalent f-number than some other f/2.8 cameras with smaller sensors.[29]

Jun 21, 2023 — 1 Answer 1 ... If we send a single photon at a beam splitter, and then put sensors on the outputs, we always observe a single photon, never two.

A usual expectation is that the term aperture refers to the opening of the aperture stop, but in reality, the term aperture and the aperture stop are mixed in use. Sometimes even stops that are not the aperture stop of an optical system are also called apertures. Contexts need to clarify these terms.

Fiberoptic sensor

The first non-experimental fiber-optic link was installed by the Dorset (UK) police in 1975. Two years later, the first live telephone traffic through fiber optics occurs in Long Beach, California.

Aperture priority is a semi-automatic shooting mode used in cameras. It permits the photographer to select an aperture setting and let the camera decide the shutter speed and sometimes also ISO sensitivity for the correct exposure. This is also referred to as Aperture Priority Auto Exposure, A mode, AV mode (aperture-value mode), or semi-auto mode.[6]

In 1973, Bell Laboratories developed a modified chemical vapor deposition process that heats chemical vapors and oxygen to form ultra-transparent glass that can be mass-produced into low-loss optical fiber. This process still remains the standard for fiber-optic cable manufacturing.

Charles Kao and George Hockham, of Standard Communications Laboratories in England, published a paper in 1964 demonstrating, theoretically, that light loss in existing glass fibers could be decreased dramatically by removing impurities.

In the 1840s, physicists Daniel Collodon and Jacques Babinet showed that light could be directed along jets of water for fountain displays. In 1854, John Tyndall, a British physicist, demonstrated that light could travel through a curved stream of water thereby proving that a light signal could be bent. He proved this by setting up a tank of water with a pipe that ran out of one side. As water flowed from the pipe, he shone a light into the tank into the stream of water. As the water fell, an arc of light followed the water down.

What isfiber optics

In 1970, the goal of making single mode fibers with attenuation less then 20dB/km was reached by scientists at Corning Glass Works. This was achieved through doping silica glass with titanium. Also in 1970, Morton Panish and Izuo Hayashi of Bell Laboratories, along with a group from the Ioffe Physical Institute in Leningrad, demonstrated a semiconductor diode laser capable of emitting continuous waves at room temperature.

The focal length value is not required when comparing two lenses of the same focal length; a value of 1 can be used instead, and the other factors can be dropped as well, leaving area proportion to the reciprocal square of the f-number N.

The aperture stop is an important element in most optical designs. Its most obvious feature is that it limits the amount of light that can reach the image/film plane. This can be either unavoidable due to the practical limit of the aperture stop size, or deliberate to prevent saturation of a detector or overexposure of film. In both cases, the size of the aperture stop determines the amount of light admitted by an optical system. The aperture stop also affects other optical system properties:

If two cameras of different format sizes and focal lengths have the same angle of view, and the same aperture area, they gather the same amount of light from the scene. In that case, the relative focal-plane illuminance, however, would depend only on the f-number N, so it is less in the camera with the larger format, longer focal length, and higher f-number. This assumes both lenses have identical transmissivity.

In the late 1970s and early 1980s, telephone companies began to use fibers extensively to rebuild their communications infrastructure.

As a matter of performance, lenses often do not perform optimally when fully opened, and thus generally have better sharpness when stopped down some – this is sharpness in the plane of critical focus, setting aside issues of depth of field. Beyond a certain point, there is no further sharpness benefit to stopping down, and the diffraction occurred at the edges of the aperture begins to become significant for imaging quality. There is accordingly a sweet spot, generally in the f/4 – f/8 range, depending on lens, where sharpness is optimal, though some lenses are designed to perform optimally when wide open. How significant this varies between lenses, and opinions differ on how much practical impact this has.

fiberoptic cable中文

A device called a diaphragm usually serves as the aperture stop and controls the aperture (the opening of the aperture stop). The diaphragm functions much like the iris of the eye – it controls the effective diameter of the lens opening (called pupil in the eyes). Reducing the aperture size (increasing the f-number) provides less light to sensor and also increases the depth of field (by limiting the angle of cone of image light reaching the sensor), which describes the extent to which subject matter lying closer than or farther from the actual plane of focus appears to be in focus. In general, the smaller the aperture (the larger the f-number), the greater the distance from the plane of focus the subject matter may be while still appearing in focus.

Opticalfibercommunication

However, modern optical research concludes that sensor size does not actually play a part in the depth of field in an image.[30] An aperture's f-number is not modified by the camera's sensor size because it is a ratio that only pertains to the attributes of the lens. Instead, the higher crop factor that comes as a result of a smaller sensor size means that, in order to get an equal framing of the subject, the photo must be taken from further away, which results in a less blurry background, changing the perceived depth of field. Similarly, a smaller sensor size with an equivalent aperture will result in a darker image because of the pixel density of smaller sensors with equivalent megapixels. Every photosite on a camera's sensor requires a certain amount of surface area that is not sensitive to light, a factor that results in differences in pixel pitch and changes in the signal-noise ratio. However, neither the changed depth of field,[31] nor the perceived change in light sensitivity [32] are a result of the aperture. Instead, equivalent aperture can be seen as a rule of thumb to judge how changes in sensor size might affect an image, even if qualities like pixel density and distance from the subject are the actual causes of changes in the image.

In the 1920s, John Logie Baird patented the idea of using arrays of transparent rods to transmit images for television and Clarence W. Hansell did the same for facsimiles. Heinrich Lamm, however, was the first person to transmit an image through a bundle of optical fibers in 1930. It was an image of a light bulb filament. His intent was to look inside inaccessible parts of the body, but the rise of the Nazis forced Lamm, a Jew, to move to America and abandon his dream of becoming a professor of medicine. His effort to file a patent was denied because of Hansell’s British patent.

The specifications for a given lens typically include the maximum and minimum aperture (opening) sizes, for example, f/0.95 – f/22. In this case, f/0.95 is currently the maximum aperture (the widest opening on a full-frame format for practical use[8]), and f/22 is the minimum aperture (the smallest opening). The maximum aperture tends to be of most interest and is always included when describing a lens. This value is also known as the lens "speed", as it affects the exposure time. As the aperture area is proportional to the light admitted by a lens or an optical system, the aperture diameter is proportional to the square root of the light admitted, and thus inversely proportional to the square root of required exposure time, such that an aperture of f/2 allows for exposure times one quarter that of f/4. (f/2 is 4 times larger than f/4 in the aperture area.)

In many living optical systems, the eye consists of an iris which adjusts the size of the pupil, through which light enters. The iris is analogous to the diaphragm, and the pupil (which is the adjustable opening in the iris) the aperture. Refraction in the cornea causes the effective aperture (the entrance pupil in optics parlance) to differ slightly from the physical pupil diameter. The entrance pupil is typically about 4 mm in diameter, although it can range from as narrow as 2 mm (f/8.3) in diameter in a brightly lit place to 8 mm (f/2.1) in the dark as part of adaptation. In rare cases in some individuals are able to dilate their pupils even beyond 8 mm (in scotopic lighting, close to the physical limit of the iris. In humans, the average iris diameter is about 11.5 mm,[23] which naturally influences the maximal size of the pupil as well, where larger iris diameters would typically have pupils which are able to dilate to a wider extreme than those with smaller irises. Maximum dilated pupil size also decreases with age.

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The amount of light captured by an optical system is proportional to the area of the entrance pupil that is the object space-side image of the aperture of the system, equal to:

In addition to an aperture stop, a photographic lens may have one or more field stops, which limit the system's field of view. When the field of view is limited by a field stop in the lens (rather than at the film or sensor) vignetting results; this is only a problem if the resulting field of view is less than was desired.

In optics, the aperture of an optical system (including a system consisted of a single lens) is a hole or an opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image of the aperture and focal length of an optical system determine the cone angle of a bundle of rays that comes to a focus in the image plane.

Apertures are also used in laser energy control, close aperture z-scan technique, diffractions/patterns, and beam cleaning.[5] Laser applications include spatial filters, Q-switching, high intensity x-ray control.

Fiberoptic cable

An optical system typically has many openings or structures that limit ray bundles (ray bundles are also known as pencils of light). These structures may be the edge of a lens or mirror, or a ring or other fixture that holds an optical element in place or may be a special element such as a diaphragm placed in the optical path to limit the light admitted by the system. In general, these structures are called stops,[2] and the aperture stop is the stop that primarily determines the cone of rays that an optical system accepts (see entrance pupil). As a result, it also determines the ray cone angle and brightness at the image point (see exit pupil). The aperture stop generally depends on the object point location; on-axis object points at different object planes may have different aperture stops, and even object points at different lateral locations at the same object plane may have different aperture stops (vignetted).[3] In practice, many object systems are designed to have a single aperture stop at designed working distance and field of view.

In astronomy, the opening diameter of the aperture stop (called the aperture) is a critical parameter in the design of a telescope. Generally, one would want the aperture to be as large as possible, to collect the maximum amount of light from the distant objects being imaged. The size of the aperture is limited, however, in practice by considerations of its manufacturing cost and time and its weight, as well as prevention of aberrations (as mentioned above).

While optimal aperture can be determined mechanically, how much sharpness is required depends on how the image will be used – if the final image is viewed under normal conditions (e.g., an 8″×10″ image viewed at 10″), it may suffice to determine the f-number using criteria for minimum required sharpness, and there may be no practical benefit from further reducing the size of the blur spot. But this may not be true if the final image is viewed under more demanding conditions, e.g., a very large final image viewed at normal distance, or a portion of an image enlarged to normal size (Hansma 1996). Hansma also suggests that the final-image size may not be known when a photograph is taken, and obtaining the maximum practicable sharpness allows the decision to make a large final image to be made at a later time; see also critical sharpness.

Optimal aperture depends both on optics (the depth of the scene versus diffraction), and on the performance of the lens.

Optically, as a lens is stopped down, the defocus blur at the Depth of Field (DOF) limits decreases but diffraction blur increases. The presence of these two opposing factors implies a point at which the combined blur spot is minimized (Gibson 1975, 64); at that point, the f-number is optimal for image sharpness, for this given depth of field[22] – a wider aperture (lower f-number) causes more defocus, while a narrower aperture (higher f-number) causes more diffraction.

Lenses with apertures opening f/2.8 or wider are referred to as "fast" lenses, although the specific point has changed over time (for example, in the early 20th century aperture openings wider than f/6 were considered fast.[9] The fastest lenses for the common 35 mm film format in general production have apertures of f/1.2 or f/1.4, with more at f/1.8 and f/2.0, and many at f/2.8 or slower; f/1.0 is unusual, though sees some use. When comparing "fast" lenses, the image format used must be considered. Lenses designed for a small format such as half frame or APS-C need to project a much smaller image circle than a lens used for large format photography. Thus the optical elements built into the lens can be far smaller and cheaper.

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The word aperture is also used in other contexts to indicate a system which blocks off light outside a certain region. In astronomy, for example, a photometric aperture around a star usually corresponds to a circular window around the image of a star within which the light intensity is assumed.[4]

The aperture stop of a photographic lens can be adjusted to control the amount of light reaching the film or image sensor. In combination with variation of shutter speed, the aperture size will regulate the film's or image sensor's degree of exposure to light. Typically, a fast shutter will require a larger aperture to ensure sufficient light exposure, and a slow shutter will require a smaller aperture to avoid excessive exposure.

The erbium-doped fiber amplifier, which reduced the cost of long-distance fiber systems by eliminating the need for optical-electrical-optical repeaters, was invented in 1986 by David Payne of the University of Southampton and Emmanuel Desurvire at Bell Labratories. Based on Desurvire’s optimized laser amplification technology, the first transatlantic telephone cable went into operation in 1988.

Canon EF lenses, introduced in 1987,[18] have electromagnetic diaphragms,[19] eliminating the need for a mechanical linkage between the camera and the lens, and allowing automatic aperture control with the Canon TS-E tilt/shift lenses. Nikon PC-E perspective-control lenses,[20] introduced in 2008, also have electromagnetic diaphragms,[21] a feature extended to their E-type range in 2013.

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In some contexts, especially in photography and astronomy, aperture refers to the opening diameter of the aperture stop through which light can pass. For example, in a telescope, the aperture stop is typically the edges of the objective lens or mirror (or of the mount that holds it). One then speaks of a telescope as having, for example, a 100-centimetre (39 in) aperture. The aperture stop is not necessarily the smallest stop in the system. Magnification and demagnification by lenses and other elements can cause a relatively large stop to be the aperture stop for the system. In astrophotography, the aperture may be given as a linear measure (for example, in inches or millimetres) or as the dimensionless ratio between that measure and the focal length. In other photography, it is usually given as a ratio.

Opticalfiber

As far back as Roman times, glass has been drawn into fibers. Yet, it was not until the 1790s that the French Chappe brothers invented the first “optical telegraph.” It was a system comprised of a series of lights mounted on towers where operators would relay a message from one tower to the next. Over the course of the next century great strides were made in optical science.

For example, film grain is quantified as graininess via a measurement of film density fluctuations as seen through a 0.048 mm sampling aperture.

In exceptional circumstances lenses can have even wider apertures with f-numbers smaller than 1.0; see lens speed: fast lenses for a detailed list. For instance, both the current Leica Noctilux-M 50mm ASPH and a 1960s-era Canon 50mm rangefinder lens have a maximum aperture of f/0.95.[10] Cheaper alternatives began appearing in the early 2010s, such as the Cosina Voigtländer f/0.95 Nokton (several in the 10.5–60 mm range) and f/0.8 (29 mm) Super Nokton manual focus lenses in the for the Micro Four-Thirds System,[11] and the Venus Optics (Laowa) Argus 35 mm f/0.95.[8]

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In 1991, Desurvire and Payne demonstrated optical amplifiers that were built into the fiber-optic cable itself. The all-optic system could carry 100 times more information than cable with electronic amplifiers. Also in 1991, photonic crystal fiber was developed. This fiber guides light by means of diffraction from a periodic structure rather then total internal reflection which allows power to be carried more efficiently then with conventional fibers therefore improving performance.

In 1951, Holger Moeller applied for a Danish patent on fiber-optic imaging in which he proposed cladding glass or plastic fibers with a transparent low-index material, but was denied because of Baird and Hansell’s patents. Three years later, Abraham Van Heel and Harold H. Hopkins presented imaging bundles in the British journal Nature at separate times. Van Heel later produced a cladded fiber system that greatly reduced signal interference and crosstalk between fibers.