A microscope (from the Ancient Greek "small" "to look" or "see") 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 calledmicroscopy. Microscopic means invisible to the eye unless aided by a microscope.
There are many types of microscopes. The most common (and the first to be invented) is the optical microscope, which uses light to image the sample. Other major types of microscopes are theelectron microscope (both the transmission electron microscopeand the scanning electron microscope), the ultramicroscope, and the various types of scanning probe microscope.

The first microscope to be developed was the optical microscope, although the original inventor is not easy to identify. Evidence points to the first compound microscope appearing in the Netherlands in the late 1500s, probably an invention of eyeglassmakers there:[1] Hans Lippershey (who developed an early telescope) and Zacharias Janssen (also claimed as the inventor of the telescope). There are other claims that the microscope and the telescope were invented by Roger Bacon in the 1200s,[2] but this is not substantiated. Giovanni Faber coined the name microscope forGalileo Galilei's compound microscope in 1625 [3] (Galileo had called it the "occhiolino" or "little eye").

2nd Century BC - Claudius Ptolemy described a stick appearing to bend in a pool of water, and accurately recorded the angles to within half a degree.

1st Century - Romans were experimenting with glass and found objects appeared larger when viewed through this new material.
1590 - Two Dutch spectacle makers, Zacharias Jansen and his father Hans started experimenting by mounting two lenses in a tube, the first compound microscope.
12th Century - Salvino D'Armate from Italy made the first eye glass, providing the wearer with an element of magnification to one eye.
1609 - Galileo Galilei develops a compound microscope with a convex and a concave lens
1665 - Robert Hooke's book called Micrographia officially documented a wide range of observations through the microscope.
1674 - Anton van Leeuwenhoek used his knowledge of grinding lenses to achieve greater magnification which he utilised to make a microscope, enabling detailed observations to be made of bacteria.
1860s - Ernst Abbe discovers the Abbe sine condition (a condition that must be fulfilled by a lens or other optical system in order for it to produce sharp images), a breakthrough in microscope design, which was until then largely based on trial and error.
1931 - Ernst Ruska starts to build the first electron microscope.

A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light). The first known practical telescopes were invented in the Netherlands at the beginning of the 17th century, using glass lenses. They found use in terrestrial applications and astronomy.
Within a few decades, the reflecting telescope was invented, which used mirrors. In the 20th century many new types of telescopes were invented, including radio telescopes in the 1930s and infrared telescopes in the 1960s. The wordtelescope now refers to a wide range of instruments detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors.
The word "telescope" (from the Greek τῆλε, tele "far" and σκοπεῖν, skopein "to look or see"; τηλεσκόπος, teleskopos "far-seeing") was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galilei's instruments presented at a banquet at the Accademia dei Lincei.[1][2][3] In the Starry Messenger, Galileo had used the term "perspicillum".

The name "telescope" covers a wide range of instruments. Most detect electromagnetic radiation, but there are major differences in how astronomers must go about collecting light (electromagnetic radiation) in different frequency bands.
Telescopes may be classified by the wavelengths of light they detect: * X-ray telescopes, using shorter wavelengths than ultraviolet light * Ultraviolet telescopes, using shorter wavelengths than visible light * Optical telescopes, using visible light * Infrared telescopes, using longer wavelengths than visible light * Submillimetre telescopes, using longer wavelengths than infrared light
An optical telescope gathers and focuses light mainly from the visible part of theelectromagnetic spectrum (although some work in the infrared and ultraviolet).[12]Optical telescopes increase the apparent angular size of distant objects as well as their apparent brightness. In order for the image to be observed, photographed, studied, and sent to a computer, telescopes work by employing one or more curved optical elements, usually made from glass lenses and/or mirrors, to gather light and other electromagnetic radiation to bring that light or radiation to a focal point. Optical telescopes are used for astronomy and in many non-astronomical instruments, including: theodolites (including transits), spotting scopes,monoculars, binoculars, camera lenses, and spyglasses. There are three main optical types: * The refracting telescope which uses lenses to form an image. * The reflecting telescope which uses an arrangement of mirrors to form an image. * The catadioptric telescope which uses mirrors combined with lenses to form an image.
Beyond these basic optical types there are many sub-types of varying optical design classified by the task they perform such as Astrographs, Comet seekers, Solar telescope, etc.

Radio telescopes are directional radio antennas used for radio astronomy. The dishes are sometimes constructed of a conductive wire mesh whose openings are smaller than the wavelength being observed. Multi-elementRadio telescopes are constructed from pairs or larger groups of these dishes to synthesize large 'virtual' apertures that are similar in size to the separation between the telescopes; this process is known as aperture synthesis. As of 2005, the current record array size is many times the width of the Earth—utilizing space-based Very Long Baseline Interferometry (VLBI) telescopes such as the Japanese HALCA (Highly Advanced Laboratory for Communications and Astronomy) VSOP (VLBI Space Observatory Program) satellite. Aperture synthesis is now also being applied to optical telescopes using optical interferometers (arrays of optical telescopes) and aperture masking interferometry at single reflecting telescopes. Radio telescopes are also used to collect microwave radiation, which is used to collect radiation when any visible light is obstructed or faint, such as from quasars. Some radio telescopes are used by programs such as SETI and the Arecibo Observatory to search for extraterrestrial life.

X-ray telescopes can use X-ray optics, such as a Wolter telescopescomposed of ring-shaped 'glancing' mirrors made of heavy metals that are able to reflect the rays just a few degrees. The mirrors are usually a section of a rotated parabola and a hyperbola, or ellipse. In 1952, Hans Wolteroutlined 3 ways a telescope could be built using only this kind of mirror.[14][15] Examples of an observatory using this type of telescope are the Einstein Observatory, ROSAT, and the Chandra X-Ray Observatory. By 2010, Wolter focusing X-ray telescopes are possible up to 79 keV.[13]

Higher energy X-ray and Gamma-ray telescopes refrain from focusing completely and use coded aperture masks: the patterns of the shadow the mask creates can be reconstructed to form an image.
X-ray and Gamma-ray telescopes are usually on Earth-orbiting satellites or high-flying balloons since the Earth's atmosphere is opaque to this part of the electromagnetic spectrum. However, high energy X-rays and gamma-rays do not form an image in the same way as telescopes at visible wavelengths. An example of this type of telescope is the Fermi Gamma-ray Space Telescope.
The detection of very high energy gamma rays, with shorter wavelength and higher frequency than regular gamma rays, requires further specialization. An example of this type of observatory is VERITAS. Very high energy gamma-rays are still photons, like visible light, whereas cosmic rays includes particles like electrons, protons, and heavier nuclei.
A discovery in 2012 may allow focusing gamma-ray telescopes.[16] At photon energies greater than 700 keV, the index of refraction starts to increase again.[16]

High-energy astronomy requires specialized telescopes to make observations since most of these particles go through most metals and glasses.
In other types of high energy particle telescopes there is no image-forming optical system. Cosmic-ray telescopesusually consist of an array of different detector types spread out over a large area. A Neutrino telescope consists of a large mass of water or ice, surrounded by an array of sensitive light detectors known as photomultiplier tubes.Energetic neutral atom observatories like Interstellar Boundary Explorer detect particles traveling at certain energies.
Other types of telescopes[edit]
Astronomy is not limited to using electromagnetic radiation. Additional information can be obtained using other media. The detectors used to observe the Universe are analogous to telescopes, these are: * Gravitational-wave detector, the equivalent of a gravitational wave telescope, used for gravitational-wave astronomy. * Neutrino detector, the equivalent of a neutrino telescope, used for neutrino astronomy.

A camera is an optical instrument that records images that can be stored directly, transmitted to another location, or both. These images may be still photographs or moving images such as videos or movies. The termcamera comes from the word camera obscura (Latin for "dark chamber"), an early mechanism for projecting images. The modern camera evolved from the camera obscura. The functioning of camera is very similar to the functioning of the human eye.
A camera may work with the light of the visible spectrum or with other portions of the electromagnetic spectrum[1] A still camera is an optical device which creates a single image of an object or scene, and records it on an electronic sensor or photographic film. All cameras use the same basic design: light enters an enclosed box through a converging lens and an image is recorded on a light-sensitive medium. A shutter mechanism controls the length of time that light can enter the camera.[2] Most photographic cameras have functions that allow a person to view the scene to be recorded, allow for a desired part of the scene to be in focus, and to control the exposure so that it is not too bright or too dim.[3] A data display, often a liquid crystal display (LCD), permits the user to view settings such as film speed, exposure, and shutter speed.[4][5]
A film or video camera operates similarly to a still camera, except it records a series of static images in rapid succession, commonly at a rate of 24 frames per second. When the images are combined and displayed in order, the illusion of motion is achieved.[6]
The forerunner to the photographic camera was the camera obscura.[8] In the fifth century B.C., the Chinese philosopher Mo Ti noted that a pinholecan form an inverted and focused image, when light passes through the hole and into a dark area.[9] Mo Ti is the first recorded person to have exploited this phenomenon to trace the inverted image to create a picture.[10] Writing in the fourth century B.C., Aristotle also mentioned this principle.[11] He described observing a partial solar eclipse in 330 B.C. by seeing the image of the Sun projected through the small spaces between the leaves of a tree.[12] In the tenth century, the Arabic scholar Ibn al-Haytham (Alhazen) also wrote about observing a solar eclipse through a pinhole,[13] and he described how a sharper image could be produced by making the opening of the pinhole smaller.[12] English philosopher Roger Bacon wrote about these optical principles in his 1267 treatise Perspectiva.[12] By the fifteenth century, artists and scientists were using this phenomenon to make observations. Originally, an observer had to enter an actual room, in which a pinhole was made on one wall. On the opposite wall, the observer would view the inverted image of the outside.[14] The name camera obscura, Latin for "dark room", derives from this early implementation of the optical phenomenon.[15] The term was first coined by mathematician and astronomer Johannes Kepler in his Ad Vitellionem paralipomena of 1604.[16]
The Italian scientist Giambattista della Porta described the camera obscura in detail in his 1558 work Magia Naturalis, and specifically suggested that an artist could project a camera obscura's images onto paper, and trace the outlines.[17] The camera obscura was popular as an aid for drawing and painting from the 1600s to the 1800s.[18] Portable set-ups were devised in the 17th century. For example, Kepler had built a portable tent, and outfitted the camera obscura with a lens by 1620.[19][20] This set-up remained popular up to the early 1800s.[21]The scientist Robert Hooke presented a paper in 1694 to the Royal Society, in which he described a portable camera obscura. It was a cone-shaped box which fit onto the head and shoulders of its user.[22] A hand-held device with a mirror reflex mechanism was first proposed by Johann Zahn in 1685, a design that would later be used in photographic cameras.[23]
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.[24] In a series of experiments, published in 1727, the German scientist Johann Heinrich Schulze demonstrated that the darkening of the salts was due to light alone, and not influenced by heat or exposure to air.[25] The Swedish chemist Carl Wilhelm Scheele showed in 1777 that silver chloride was especially susceptible to darkening from light exposure, and that once darkened, it becomes insoluble in an ammonia solution.[25] The first person to use this chemistry to create images wasThomas Wedgwood.[24] 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 weren't permanent, however, as Wedgwood didn't employ a fixing mechanism. He ultimately failed at his goal of using the process to create fixed images created by a camera obscura.[26]

The Giroux daguerreotype camera, the first to be commercially produced.

The first permanent photograph of a camera image was made in 1826 by Joseph Nicéphore Niépce using a sliding wooden box camera made by Charles and Vincent Chevalier in Paris.[29] 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. It was made using an 8-hour exposure on pewter coated with bitumen.[30] Niépce called his process "heliography".[31] Niépce corresponded with the inventor Louis-Jacques-Mande Daguerre, and the pair entered into a partnership to improve the heliographic process. Niépce had experimented further with other chemicals, to improve contrast in his heliographs. Daguerre contributed an improved camera obscura design, but the partnership ended when Niépce died in 1833.[32] Daguerre succeeded in developing a high-contrast and extremely sharp image by exposing on a plate coated with silver iodide, and exposing this plate again to mercury vapor.[33] By 1837, he was able to fix the images with a common salt solution. He called this processDaguerreotypie, and tried unsuccessfully for a couple years to commercialize it. Eventually, with help of the scientist and politician François Arago, the French government acquired Daguerre's process for public release. In exchange, pensions were provided to Daguerre and Niépce's son, Isidore.[34]
The first photographic camera developed for commercial manufacture was a daguerreotype camera, built byAlphonse Giroux. Giroux signed a contract with Daguerre and Isidore Niépce to produce the cameras in France,[35] which each device and accessories costing 400 francs.[36] The camera was a double-box design, with a landscape lens fitted to the outer box, and a holder for a ground glass focusing screen and image plate on the inner box. By sliding the inner box, objects at various distances could be brought to as sharp a focus as desired. After a satisfactory image had been focused on the screen, the screen was replaced with a sensitized plate. Aknurled wheel controlled a copper flap in front of the lens, which functioned as a shutter. The early daguerreotype cameras required long exposure times, which in 1839 could be from 5 to 30 minutes.[35][37]
Similar cameras were used for exposing the silver-surfaced copper plates, commercially introduced in 1839, which were the first practical photographic medium. The collodion wet plate process that gradually replaced the daguerreotype during the 1850s required photographers to coat and sensitize thin glass or iron plates shortly before use and expose them in the camera while still wet. Early wet plate cameras were very simple and little different from Daguerreotype cameras, but more sophisticated designs eventually appeared. The Dubroni of 1864 allowed the sensitizing and developing of the plates to be carried out inside the camera itself rather than in a separate darkroom. Other cameras were fitted with multiple lenses for photographing several small portraits on a single larger plate, useful when making cartes de visite. It was during the wet plate era that the use of bellows for focusing became widespread, making the bulkier and less easily adjusted nested box design obsolete.
For many years, exposure times were long enough that the photographer simply removed the lens cap, counted off the number of seconds (or minutes) estimated to be required by the lighting conditions, then replaced the cap. As more sensitive photographic materials became available, cameras began to incorporate mechanical shutter mechanisms that allowed very short and accurately timed exposures to be made.
The first camera utilizing digital technologies to capture and store images was developed by Kodak engineerSteven Sasson in 1975. He used a charge-coupled device (CCD) provided by Fairchild Semiconductor, which provided only 0.01 megapixels to capture images. Sasson combined the CCD device with movie camera parts to create a digital camera that saved black and white images onto a cassette tape.[38] The images were then read from the cassette and viewed on a TV monitor.

Traditional cameras capture light onto photographic film or photographic plate. Video and digital cameras use an electronic image sensor, usually a charge coupled device (CCD) or a CMOS sensor to capture images which can be transferred or stored in a memory card or other storage inside the camera for later playback or processing.
Cameras that capture many images in sequence are known as movie cameras or as ciné cameras in Europe; those designed for single images are still cameras.
However these categories overlap as still cameras are often used to capture moving images in special effects work and many modern cameras can quickly switch between still and motion recording modes.
A video camera is a category of movie camera that captures images electronically (either using analog or digital technology).
The lens of a camera captures the light from the subject and brings it to a focus on the film or detector. The design and manufacture of the lens is critical to the quality of the photograph being taken. The technological revolution in camera design in the 19th century revolutionized optical glass manufacture and lens design with great benefits for modern lens manufacture in a wide range of optical instruments from reading glasses to microscopes. Pioneers included Zeiss and Leitz.

Camera lenses are made in a wide range of focal lengths. They range from extreme wide angle, wide angle, standard, medium telephoto andtelephoto. Each lens is best suited to a certain type of photography. The extreme wide angle may be preferred for architecture because it has the capacity to capture a wide view of a building. The normal lens, because it often has a wide aperture, is often used for street and documentary photography. The telephoto lens is useful for sports and wildlife but it is more susceptible to camera shake.[40]

Due to the optical properties of photographic lenses, only objects within a limited range of distances from the camera will be reproduced clearly. The process of adjusting this range is known as changing the camera's focus. There are various ways of focusing a camera accurately. The simplest cameras have fixed focus and use a small aperture and wide-angle lens to ensure that everything within a certain range of distance from the lens, usually around 3 metres (10 ft) to infinity, is in reasonable focus. Fixed focus cameras are usually inexpensive types, such as single-use cameras. The camera can also have a limited focusing range or scale-focus that is indicated on the camera body. The user will guess or calculate the distance to the subject and adjust the focus accordingly. On some cameras this is indicated by symbols (head-and-shoulders; two people standing upright; one tree; mountains).

Rangefinder cameras allow the distance to objects to be measured by means of a coupled parallax unit on top of the camera, allowing the focus to be set with accuracy. Single-lens reflex cameras allow the photographer to determine the focus and composition visually using the objective lens and a moving mirror to project the image onto a ground glass or plastic micro-prism screen. Twin-lens reflex cameras use an objective lens and a focusing lens unit (usually identical to the objective lens.) in a parallel body for composition and focusing. View cameras use a ground glass screen which is removed and replaced by either a photographic plate or a reusable holder containing sheet film before exposure. Modern cameras often offerautofocus systems to focus the camera automatically by a variety of methods.[41]

Some experimental cameras, for example the planar Fourier capture array (PFCA), do not require focusing to allow them to take pictures. In conventional digital photography, lenses or mirrors map all of the light originating from a single point of an in-focus object to a single point at the sensor plane. Each pixel thus relates an independent piece of information about the far-away scene. In contrast, a PFCA does not have a lens or mirror, but each pixel has an idiosyncratic pair of diffraction gratings above it, allowing each pixel to likewise relate an independent piece of information (specifically, one component of the 2D Fourier transform) about the far-away scene. Together, complete scene information is captured and images can be reconstructed by computation.
Some cameras have post focusing. Post focusing means take the pictures first and then focusing later at thepersonal computer. The camera uses many tiny lenses on the sensor to capture light from every camera angle of a scene and is called plenoptics technology. A current plenoptic camera design has 40,000 lenses working together to grab the optimal picture.

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Camera accessories
Accessories for cameras are mainly for care, protection, special effects and functions. * Lens hood: used on the end of a lens to block the sun or other light source to prevent glare and lens flare (see also matte box). * Lens cap: covers and protects the lens during storage. * Lens adapter: sometimes called a step-ring, adapts the lens to other size filters. * Lens filters: allow artificial colors or change light density. * Lens extension tubes allow close focus in macro photography. * Flash equipment: including light diffuser, mount and stand, reflector, soft box, trigger and cord. * Care and protection: including camera case and cover, maintenance tools, and screen protector. * Large format cameras use special equipment which includes magnifier loupe, view finder, angle finder, focusing rail /truck. * Battery and sometimes a charger. * Some professional SLR could be provided with interchangeable finders for eye-level or waist-level focusing,focusing screens, eye-cup, data backs, motor-drives for film transportation or external battery packs. * Tripod, microscope adapter, cable release, electric wire release.

Shutters[edit]
Main article: Shutter (photography)
Although a range of different shutter devices have been used during the development of the camera only two types have been widely used and remain in use today.
The Leaf shutter or more precisely the in-lens shutter is a shutter contained within the lens structure, often close to the diaphragm consisting of a number of metal leaves which are maintained under spring tension and which are opened and then closed when the shutter is released. The exposure time is determined by the interval between opening and closing. In this shutter design, the whole film frame is exposed at one time. This makes flash synchronisation much simpler as the flash only needs to fire once the shutter is fully open. Disadvantages of such shutters are their inability to reliably produce very fast shutter speeds ( faster than 1/500th second or so) and the additional cost and weight of having to include a shutter mechanism for every lens.
The focal-plane shutter operates as close to the film plane as possible and consists of cloth curtains that are pulled across the film plane with a carefully determined gap between the two curtains (typically running horizontally) or consisting of a series of metal plates (typically moving vertically) just in front of the film plane. The focal-plane shutter is primarily associated with the single lens reflex type of cameras, since covering the film rather than blocking light passing through the lens allows the photographer to view through the lens at all timesexcept during the exposure itself. Covering the film also facilitates removing the lens from a loaded camera (many SLRs have interchangeable lenses).

Eyes are the organs of vision. They detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptor cells in conscious vision connect light to movement. In higher organisms the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through adiaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortexand other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system.[1] Image-resolving eyes are present in molluscs, chordates and arthropods.[2]
The simplest "eyes", such as those in microorganisms, do nothing but detect whether the surroundings are light or dark, which is sufficient for the entrainment of circadian rhythms.[citation needed] From more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment.