1.
Lens (optics)
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A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a piece of transparent material, while a compound lens consists of several simple lenses. Lenses are made from such as glass or plastic, and are ground. A lens can focus light to form an image, unlike a prism, devices that similarly focus or disperse waves and radiation other than visible light are also called lenses, such as microwave lenses, electron lenses, acoustic lenses, or explosive lenses. The word lens comes from the Latin name of the lentil, the genus of the lentil plant is Lens, and the most commonly eaten species is Lens culinaris. The lentil plant also gives its name to a geometric figure, the variant spelling lense is sometimes seen. While it is listed as a spelling in some dictionaries. The oldest lens artifact is the Nimrud lens, dating back 2700 years to ancient Assyria, david Brewster proposed that it may have been used as a magnifying glass, or as a burning-glass to start fires by concentrating sunlight. Another early reference to magnification dates back to ancient Egyptian hieroglyphs in the 8th century BC, the earliest written records of lenses date to Ancient Greece, with Aristophanes play The Clouds mentioning a burning-glass. Some scholars argue that the evidence indicates that there was widespread use of lenses in antiquity. Such lenses were used by artisans for fine work, and for authenticating seal impressions, both Pliny and Seneca the Younger described the magnifying effect of a glass globe filled with water. The Viking lenses were capable of concentrating enough sunlight to ignite fires, between the 11th and 13th century reading stones were invented. Often used by monks to assist in illuminating manuscripts, these were primitive plano-convex lenses initially made by cutting a sphere in half. As the stones were experimented with, it was understood that shallower lenses magnified more effectively. Lenses came into use in Europe with the invention of spectacles. Spectacle makers created improved types of lenses for the correction of vision based more on knowledge gained from observing the effects of the lenses. With the invention of the telescope and microscope there was a deal of experimentation with lens shapes in the 17th. Opticians tried to construct lenses of varying forms of curvature, wrongly assuming errors arose from defects in the figure of their surfaces
2.
Mirror
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This is different from other light-reflecting objects that do not preserve much of the original wave signal other than color and diffuse reflected light. The most familiar type of mirror is the mirror, which has a flat screen surface. Curved mirrors are used, to produce magnified or diminished images or focus light or simply distort the reflected image. Mirrors are commonly used for personal grooming or admiring oneself, decoration, Mirrors are also used in scientific apparatus such as telescopes and lasers, cameras, and industrial machinery. Most mirrors are designed for light, however, mirrors designed for other wavelengths of electromagnetic radiation are also used. The first mirrors used by people were most likely pools of dark, still water, the requirements for making a good mirror are a surface with a very high degree of flatness, and a surface roughness smaller than the wavelength of the light. The earliest manufactured mirrors were pieces of polished stone such as obsidian, examples of obsidian mirrors found in Anatolia have been dated to around 6000 BC. Mirrors of polished copper were crafted in Mesopotamia from 4000 BC, polished stone mirrors from Central and South America date from around 2000 BC onwards. In China, bronze mirrors were manufactured from around 2000 BC, some of the earliest bronze, Mirrors made of other metal mixtures such as copper and tin speculum metal may have also been produced in China and India. Mirrors of speculum metal or any precious metal were hard to produce and were owned by the wealthy. Stone mirrors often had poor reflectivity compared to metals, yet metals scratch or tarnish easily, depending upon the color, both often yielded reflections with poor color rendering. The poor image quality of ancient mirrors explains 1 Corinthians 13s reference to seeing as in a mirror, glass was a desirable material for mirrors. Because the surface of glass is smooth, it produces reflections with very little blur. In addition, glass is very hard and scratch resistant, however, glass by itself has little reflectivity, so people began coating it with metals to increase the reflectivity. According to Pliny, the people of Sidon developed a technique for creating crude mirrors by coating glass with molten lead. Glass mirrors backed with gold leaf are mentioned by Pliny in his Natural History and these circular mirrors were typically small, from only a fraction of an inch to as much as eight inches in diameter. These small mirrors produced distorted images, yet were prized objects of high value and these ancient glass mirrors were very thin, thus very fragile, because the glass needed to be extremely thin to prevent cracking when coated with a hot, molten metal. Due to the quality, high cost, and small size of these ancient glass mirrors
3.
Microscope
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A microscope is an instrument used to see objects that are too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy, microscopic means invisible to the eye unless aided by a microscope. There are many types of microscopes, the most common is the optical microscope, which uses light to image the sample. Other major types of microscopes are the microscope, the ultramicroscope. The earliest microscopes were single lens magnifying glasses with limited magnification which date at least as far back as the wide use of lenses in eyeglasses in the 13th century. Compound microscopes, which combine an objective lens with an eyepiece to view a real image, the actual inventor of the compound microscope is unknown although many claims have been made over the years. These include what may be a claim by the son of Zacharias Janssen that his father invented the microscope and telescope as early as 1590. Historians note the compound microscope did not appear in the Netherlands until the 1620s, giovanni Faber coined the name microscope for the compound microscope Galileo submitted to the Accademia dei Lincei in 1625. The first detailed account of the construction of living tissue based on the use of a microscope did not appear until 1644, in Giambattista Odiernas Locchio della mosca. It was not until the 1660s and 1670s that the microscope was used extensively for research in Italy, marcello Malpighi in Italy began the analysis of biological structures, beginning with the lungs. Robert Hookes Micrographia had an impact, largely because of its impressive illustrations. A significant contribution came from Antonie van Leeuwenhoek who achieved up to 300 times magnification using a single lens microscope. He sandwiched a very small glass ball lens between the holes in two metal plates riveted together, and with a needle attached to mount the specimen. Then, Van Leeuwenhoek re-discovered red blood cells and spermatozoa, on 9 October 1676, he reported the discovery of micro-organisms. The performance of light microscopy depends as much on how the sample is illuminated as on how it is observed, early instruments were limited until this principle was fully appreciated and developed, and until electric lamps were available as light sources. In 1893 August Köhler developed a key principle of sample illumination, Köhler illumination and this method of sample illumination produces even lighting and overcomes the limited contrast and resolution imposed by early techniques of sample illumination. In the early 20th century a significant alternative to light microscopy was developed, ernst Ruska started development of the first electron microscope in 1931 which was the transmission electron microscope. The transmission electron microscope works on the principle as an optical microscope but uses electrons in the place of light
4.
Telescope
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A telescope is an optical instrument that aids in the observation of remote objects by collecting electromagnetic radiation. The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s and they found use in both terrestrial applications and astronomy. Within a few decades, the telescope was invented, which used mirrors to collect. In the 20th century many new types of telescopes were invented, including radio telescopes in the 1930s, the word telescope now refers to a wide range of instruments capable of detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors. The word telescope was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galileis instruments presented at a banquet at the Accademia dei Lincei, in the Starry Messenger, Galileo had used the term perspicillum. The earliest recorded working telescopes were the telescopes that appeared in the Netherlands in 1608. Their development is credited to three individuals, Hans Lippershey and Zacharias Janssen, who were spectacle makers in Middelburg, Galileo heard about the Dutch telescope in June 1609, built his own within a month, and improved upon the design in the following year. Also in 1609, Thomas Harriot became the first person known to point a telescope skyward in order to make observations of a celestial object. The idea that the objective, or light-gathering element, could be a mirror instead of a lens was being investigated soon after the invention of the refracting telescope. The potential advantages of using parabolic mirrors—reduction of spherical aberration and no chromatic aberration—led to many proposed designs, in 1668, Isaac Newton built the first practical reflecting telescope, of a design which now bears his name, the Newtonian reflector. The invention of the lens in 1733 partially corrected color aberrations present in the simple lens and enabled the construction of shorter. The largest reflecting telescopes currently have objectives larger than 10 m, the 20th century also saw the development of telescopes that worked in a wide range of wavelengths from radio to gamma-rays. The first purpose built radio telescope went into operation in 1937, since then, a tremendous variety of complex astronomical instruments have been developed. The name telescope covers a range of instruments. Most detect electromagnetic radiation, but there are differences in how astronomers must go about collecting light in different frequency bands. The near-infrared can be collected much like light, however in the far-infrared and submillimetre range. For example, the James Clerk Maxwell Telescope observes from wavelengths from 3 μm to 2000 μm, on the other hand, the Spitzer Space Telescope, observing from about 3 μm to 180 μm uses a mirror. Also using reflecting optics, the Hubble Space Telescope with Wide Field Camera 3 can observe in the range from about 0.2 μm to 1.7 μm
5.
Camera
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Thumb|A2016 Nikon D810 A camera is an optical instrument for recording or capturing images, which may be stored locally, transmitted to another location, or both. The images may be individual still photographs or sequences of images constituting videos or movies, the camera is a remote sensing device as it senses subjects without physical contact. The word camera comes from camera obscura, which means dark chamber and is the Latin name of the device for projecting an image of external reality onto a flat surface. The modern photographic camera evolved from the camera obscura, the functioning of the camera is very similar to the functioning of the human eye. A camera may work with the light of the spectrum or with other portions of the electromagnetic spectrum. A still camera is a device which creates a single image of an object or scene. All cameras use the basic design, light enters an enclosed box through a converging lens/convex lens. A shutter mechanism controls the length of time that light can enter the camera, a display, often a liquid crystal display, permits the user to view scene to be recorded and settings such as ISO speed, exposure, and shutter speed. A movie camera or a video camera operates similarly to a camera, except it records a series of static images in rapid succession. When the images are combined and displayed in order, the illusion of motion is achieved, the forerunner to the photographic camera was the camera obscura. The oldest known record of this principle is a description by Han Chinese philosopher Mozi, Mozi correctly asserted that the camera obscura image is inverted because light travels in straight lines from its source. In the 11th century Arab physicist Ibn al-Haytham s wrote very influential essays about experiments with light through an opening in a darkened room. The use of a lens in the opening of a wall or closed window shutter of a room to project images used as a drawing aid has been traced back to circa 1550. Since the late 17th century portable camera obscura devices in tents, before the development of the photographic camera, it had been known for hundreds of years that some substances, such as silver salts, darkened when exposed to sunlight. The first person to use this chemistry to create images was Thomas Wedgwood, to create images, Wedgwood placed items, such as leaves and insect wings, on ceramic pots coated with silver nitrate, and exposed the set-up to light. These images werent permanent, however, as Wedgwood didnt employ a fixing mechanism and he ultimately failed at his goal of using the process to create fixed images created by a camera obscura. The first permanent photograph of an image was made in 1826 by Joseph Nicéphore Niépce using a sliding wooden box camera made by Charles. Niépce had been experimenting with ways to fix the images of a camera obscura since 1816, the photograph Niépce succeeded in creating shows the view from his window
6.
Focal length
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The focal length of an optical system is a measure of how strongly the system converges or diverges light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus. A system with a focal length has greater optical power than one with a long focal length. For a thin lens in air, the length is the distance from the center of the lens to the principal foci of the lens. For a converging lens, the length is positive, and is the distance at which a beam of collimated light will be focused to a single spot. For a diverging lens, the length is negative, and is the distance to the point from which a collimated beam appears to be diverging after passing through the lens. The focal length of a lens can be easily measured by using it to form an image of a distant light source on a screen. The lens is moved until an image is formed on the screen. In this case 1/u is negligible, and the length is then given by f ≈ v. Back focal length or back focal distance is the distance from the vertex of the last optical surface of the system to the focal point. For an optical system in air, the focal length gives the distance from the front. If the surrounding medium is not air, then the distance is multiplied by the index of the medium. Some authors call these distances the front/rear focal lengths, distinguishing them from the front/rear focal distances, defined above. In general, the length or EFL is the value that describes the ability of the optical system to focus light. The other parameters are used in determining where an image will be formed for an object position. The quantity 1/f is also known as the power of the lens. The corresponding front focal distance is, FFD = f, in the sign convention used here, the value of R1 will be positive if the first lens surface is convex, and negative if it is concave. The value of R2 is negative if the surface is convex
7.
Eyepiece
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An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is so named because it is usually the lens that is closest to the eye when someone looks through the device, the objective lens or mirror collects light and brings it to focus creating an image. The eyepiece is placed near the point of the objective to magnify this image. The amount of magnification depends on the length of the eyepiece. An eyepiece consists of several elements in a housing, with a barrel on one end. The barrel is shaped to fit in an opening of the instrument to which it is attached. The image can be focused by moving the eyepiece nearer and further from the objective, most instruments have a focusing mechanism to allow movement of the shaft in which the eyepiece is mounted, without needing to manipulate the eyepiece directly. The eyepieces of binoculars are usually mounted in the binoculars, causing them to have a pre-determined magnification. With telescopes and microscopes, however, eyepieces are usually interchangeable, by switching the eyepiece, the user can adjust what is viewed. For instance, eyepieces will often be interchanged to increase or decrease the magnification of a telescope, eyepieces also offer varying fields of view, and differing degrees of eye relief for the person who looks through them. Several properties of an eyepiece are likely to be of interest to a user of an optical instrument, eyepieces are optical systems where the entrance pupil is invariably located outside of the system. They must be designed for optimal performance for a distance to this entrance pupil. In a refracting astronomical telescope the entrance pupil is identical with the objective and this may be several feet distant from the eyepiece, whereas with a microscope eyepiece the entrance pupil is close to the back focal plane of the objective, mere inches from the eyepiece. Microscope eyepieces may be corrected differently from telescope eyepieces, however, elements are the individual lenses, which may come as simple lenses or singlets and cemented doublets or triplets. When lenses are cemented together in pairs or triples, the elements are called groups. The first eyepieces had only a lens element, which delivered highly distorted images. Two and three-element designs were invented soon after, and quickly became standard due to the image quality. Today, engineers assisted by computer-aided drafting software have designed eyepieces with seven or eight elements that deliver exceptionally large, internal reflections, sometimes called scatter, cause the light passing through an eyepiece to disperse and reduce the contrast of the image projected by the eyepiece
8.
Camera lens
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A lens might be permanently fixed to a camera, or it might be interchangeable with lenses of different focal lengths, apertures, and other properties. While in principle a simple convex lens will suffice, in practice a compound made up of a number of optical lens elements is required to correct the many optical aberrations that arise. Some aberrations will be present in any lens system and it is the job of the lens designer to balance these and produce a design that is suitable for photographic use and possibly mass production. Typical rectilinear lenses can be thought of as improved pinhole lenses, as shown, a pinhole lens is simply a small aperture that blocks most rays of light, ideally selecting one ray to the object for each point on the image sensor. Here a pixel is the area of the detector exposed to light from a point on the object, making the pinhole smaller improves resolution, but reduces the amount of light captured. At a certain point, shrinking the hole does not improve the resolution because of the diffraction limit, beyond this limit, making the hole smaller makes the image blurrier as well as darker. Practical lenses can be thought of as an answer to the question how can a pinhole lens be modified to more light. A first step is to put a simple convex lens at the pinhole with a length equal to the distance to the film plane. The geometry is almost the same as with a pinhole lens. From the front of the camera, the hole, would be seen. If one were inside the camera, one would see the acting as a projector. The virtual image of the aperture from inside the camera is the exit pupil. Practical photographic lenses include more lens elements, a camera lens may be made from a number of elements, from one, as in the Box Brownies meniscus lens, to over 20 in the more complex zooms. These elements may themselves comprise a group of lenses cemented together, the front element is critical to the performance of the whole assembly. In all modern lenses the surface is coated to reduce abrasion, flare, and surface reflectance, to minimize aberration, the curvature is usually set so that the angle of incidence and the angle of refraction are equal. In a prime lens this is easy, but in a zoom there is always a compromise, the lens usually is focused by adjusting the distance from the lens assembly to the image plane, or by moving elements of the lens assembly. To improve performance, some lenses have a cam system that adjusts the distance between the groups as the lens is focused, manufacturers call this different things, Nikon calls it CRC, Canon calls it a floating system, and Hasselblad and Mamiya call it FLE. Glass is the most common used to construct lens elements, due to its good optical properties
9.
Projector
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A projector or image projector is an optical device that projects an image onto a surface, commonly a projection screen. Most projectors create an image by shining a light through a transparent lens. A virtual retinal display, or retinal projector, is a projector that projects an image directly on the retina instead of using a projection screen. The most common type of projector used today is called a video projector. Video projectors are digital replacements for earlier types of such as slide projectors. These earlier types of projectors were replaced with digital video projectors throughout the 1990s and early 2000s. The newest types of projectors are handheld projectors that use lasers or LEDs to project images and their projections are hard to see if there is too much ambient light. Movie theaters used a type of projector called a movie projector, spectators not always provided the details needed to differentiate between for instance a shadow play and a lantern projection. Many did not understand the nature of what they had seen, projections were often presented or perceived as magic or even as religious experiences, with most projectionists unwilling to share their secrets. Shadow play usually does not involve a projection device, but can be seen as a first step in the development of projectors. It evolved into more refined forms of puppetry in Asia. Projectors share a history with cameras in the camera obscura. The oldest known record of this principle is a description by Han Chinese philosopher Mozi, Mozi correctly asserted that the camera obscura image is inverted because light travels in straight lines from its source. In the 11th century Arab physicist Ibn al-Haytham described experiments with light through an opening in a darkened room. The use of a lens in the opening of a wall or closed window shutter of a room has been traced back to circa 1550. The shared history of camera and projector basically split with the introduction of the lantern in the later half of the 17th century. The camera obscura device would mostly live on as an aid in the form of tents. The oldest known objects that can project images are Chinese magic mirrors, the origins of these mirrors have been traced back to the Chinese Han dynasty and are also found in Japan. The mirrors were cast in bronze with a pattern embossed at the back, the pattern seen on the back of the mirror is seen in a projection when light is reflected from the polished front onto a wall or other surface
10.
Refracting telescope
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A refracting telescope is a type of optical telescope that uses a lens as its objective to form an image. The refracting telescope design was used in spy glasses and astronomical telescopes but is also used for long focus camera lenses. A refractors magnification is calculated by dividing the length of the objective lens by that of the eyepiece. Refractors were the earliest type of optical telescope, Galileo Galilei, happening to be in Venice in about the month of May 1609, heard of the invention and constructed a version of his own. Galileo then communicated the details of his invention to the public, all refracting telescopes use the same principles. The objective in a refracting telescope refracts or bends light and this refraction causes parallel light rays to converge at a focal point, while those not parallel converge upon a focal plane. The telescope converts a bundle of rays to make an angle α. The ratio β/α is called the angular magnification and it equals the ratio between the retinal image sizes obtained with and without the telescope. Refracting telescopes can come in different configurations to correct for image orientation. Because the image was formed by the bending of light, or refraction, the design Galileo Galilei used in 1609 is commonly called a Galilean telescope. It used a convergent objective lens and a divergent eyepiece lens, a Galilean telescope, because the design has no intermediary focus, results in a non-inverted and upright image. Galileo’s best telescope magnified objects about 30 times, because of flaws in its design, such as the shape of the lens and the narrow field of view, the images were blurry and distorted. Despite these flaws, the telescope was still enough for Galileo to explore the sky. The Galilean telescope could view the phases of Venus, and was able to see craters on the Moon, parallel rays of light from a distant object would be brought to a focus in the focal plane of the objective lens. The eyepiece lens intercepts these rays and renders them parallel once more, non-parallel rays of light from the object traveling at an angle α1 to the optical axis travel at a larger angle after they passed through the eyepiece. This leads to an increase in the apparent angular size and is responsible for the perceived magnification, the final image is a virtual image, located at infinity and is the same way up as the object. The Keplerian telescope, invented by Johannes Kepler in 1611, is an improvement on Galileos design and it uses a convex lens as the eyepiece instead of Galileos concave one. The advantage of this arrangement is that the rays of light emerging from the eyepiece are converging and this allows for a much wider field of view and greater eye relief, but the image for the viewer is inverted
11.
Primary mirror
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A primary mirror is the principal light-gathering surface of a reflecting telescope. The primary mirror of a telescope is a spherical or parabolic shaped disks of polished reflective metal, or in later telescopes. One of the first known reflecting telescopes, Newtons reflector of 1668, the next major change was to use silver on glass rather than metal, in the 19th century such was with the Crossley reflector. This was changed to vacuum deposited aluminum on glass, used on the 200-inch Hale telescope, solid primary mirrors have to sustain their own weight and not deform under gravity, which limits the maximum size for a single piece primary mirror. Segmented mirror configurations are used to get around the limitation on single primary mirrors. For example, the Giant Magellan Telescope will have seven 8.4 meter primary mirrors, with the resolving power equivalent to a 24.5 m optical aperture. The largest optical telescope in the world as of 2009 to use a non-segmented single-mirror as its mirror is the 8. S. /German/Italian Large Binocular Telescope has two 8.4 m mirrors. Both of these are smaller than the 10 m segmented primary mirrors on the two Keck telescope, the Hubble Space Telescope has a 2.4 m primary mirror. Radio and submillimeter telescopes use much larger dishes or antennae, which do not have to be made as precisely as the used in optical telescopes. The Arecibo Observatory uses a 305 m dish, which is the world largest single-dish radio telescope fixed to the ground, the Green Bank Telescope has the worlds largest steerable single radio dish with 100 m in diameter. There are largest radio arrays, composed of multiple dishes which have better image resolution, active optics Honeycomb mirror Liquid mirror List of largest optical reflecting telescopes List of telescope parts and construction Mirror mount Mirror support cell Secondary mirror
12.
Reflecting telescope
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A reflecting telescope is an optical telescope which uses a single or combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century as an alternative to the telescope which. Although reflecting telescopes produce other types of aberrations, it is a design that allows for very large diameter objectives. Almost all of the telescopes used in astronomy research are reflectors. Reflecting telescopes come in many variations and may employ extra optical elements to improve image quality or place the image in a mechanically advantageous position. Since reflecting telescopes use mirrors, the design is referred to as a catoptric telescope. The idea that curved mirrors behave like lenses dates back at least to Alhazens 11th century treatise on optics, the potential advantages of using parabolic mirrors, primarily reduction of spherical aberration with no chromatic aberration, led to many proposed designs for reflecting telescopes. The most notable being James Gregory, who published a design for a ‘reflecting’ telescope in 1663. It would be ten years, before the experimental scientist Robert Hooke was able to build this type of telescope, Isaac Newton has been generally credited with building the first reflecting telescope in 1668. It used a spherically ground metal primary mirror and a diagonal mirror in an optical configuration that has come to be known as the Newtonian telescope. A curved primary mirror is the reflector telescopes basic optical element that creates an image at the focal plane, the distance from the mirror to the focal plane is called the focal length. The primary mirror in most modern telescopes is composed of a glass cylinder whose front surface has been ground to a spherical or parabolic shape. A thin layer of aluminum is deposited onto the mirror. Some telescopes use primary mirrors which are made differently, molten glass is rotated to make its surface paraboloidal, and is kept rotating while it cools and solidifies. The resulting mirror shape approximates a desired paraboloid shape that requires grinding and polishing to reach the exact figure needed. Reflecting telescopes, just like any other system, do not produce perfect images. The use of mirrors avoids chromatic aberration but they produce other types of aberrations, to avoid this problem most reflecting telescopes use parabolic shaped mirrors, a shape that can focus all the light to a common focus. Field curvature - The best image plane is in general curved and it is sometimes corrected by a field flattening lens
