Image projector
Encyclopedia
An image projector is an optical device that projects an image (or moving images) onto a surface, commonly a projection screen
.
Most projectors creates an image by shining a light through a small transparent image, but some newer types of projectors can project the image directly, by using lasers. A virtual retinal display
, or retinal projector, is a projector that projects an image directly on the retina
instead of using an external projection screen.
The most common type of projector used today is called a video projector
. Video projectors are digital replacements for earlier types of projectors such as slide projector
s and overhead projector
s. These earlier types of projectors were mostly replaced with digital video projectors throughout the 1990s and early 2000s, but old analog projectors are still used some places. The newest types of projectors are handheld projector
s that use laser
s or LED
s to project images.
Movie theater
s use a type of projector called a movie projector
.
Another type of projector is the enlarger
, a device used to produce photographic prints from negatives.
s. As far back as the 4th century BC, Greeks
such as Aristotle
and Euclid
wrote on naturally-occurring rudimentary pinhole camera
s. For example, light may travel through the slits of wicker baskets or the crossing of tree leaves. (The circular dapples on a forest floor, actually pinhole images of the sun, can be seen to have a bite taken out of them during partial solar eclipses opposite to the position of the moon's actual occultation of the sun because of the inverting effect of pinhole lenses.)
It was the 10th-century Ibn al-Haytham (Alhazen), who published this idea in the Book of Optics
in 1021 AD. When Ibn al-Haytham began experiment
ing with the camera obscura, he himself stated, Et nos non inventimus ita, "we did not invent this". He improved on the camera after realizing that the smaller the pinhole, the sharper the image (though the less light). He provides the first clear description for construction of a camera obscura
(Lat. dark chamber). As a side benefit of his invention, he was credited with being first man to shift physics from a philosophical to an experimental basis.
In the 5th century BC, the Mohist philosopher Mo Jing
(墨經) in ancient China mentioned the effect of an inverted image forming through a pinhole. The image of an inverted Chinese pagoda
is mentioned in Duan Chengshi
's (d. 863) book Miscellaneous Morsels from Youyang
written during the Tang Dynasty
(618–907). Along with experimenting with the pinhole camera and the burning mirror
of the ancient Mohists, the Song Dynasty
(960–1279 AD) Chinese
scientist Shen Kuo
(1031–1095) experimented with camera obscura and was the first to establish geometrical and quantitative
attributes for it.
In the 13th century, Robert Grosseteste
and Roger Bacon
commented on the pinhole camera. Between 1000 and 1600, men such as Ibn al-Haytham, Gemma Frisius
, and Giambattista della Porta
wrote on the pinhole camera, explaining why the images are upside down. Pinhole devices provide safety for the eyes when viewing solar eclipses because the event is observed indirectly, the diminished intensity of the pinhole image being harmless compared with the full glare of the Sun
itself.
. The lantern had a small translucent window that contained an image of a devil holding a lance http://www.precinemahistory.net/fontana.htm. Leonardo da Vinci
also made a similar sketch in 1515. These drawings are likely to have inspired the creation of the earliest image projector, a device called a magic lantern
.
In the 17th century, a the first magic lantern
was developed. With pinhole cameras and camera obscura it was only possible to project an image of actual scene, such as an image of the sun, on a surface. The magic lantern on the other hand could project a painted image on a surface, and marks the point where cameras and projectors became two different kinds of devices. There has been some debate about who the original inventor of the magic lantern is, but the most widely accepted theory is that Christiaan Huygens developed the original device in the late 1650s. However, other sources give credit to the German priest Athanasius Kircher
. He describes a device such as the magic lantern in his book Ars Magna Lucis et Umbrae. There are possible mentions of this device associated with Kircher as early as 1646. Even in its earliest use, it was demonstrated with monstrous images such as the Devil. Huygen’s device was even referred to as the “lantern of fright” because it was able to project spooky images that looked like apparitions. In its early development, it was mostly used by magicians and conjurers to project images, making them appear or disappear, transform from one scene into a different scene, animate normally inanimate objects, or even create the belief of bringing the dead back to life.
In the 1660s, a man named Thomas Walgensten used his so-called “lantern of fear” to summon ghosts. These misuses of this early machine were not uncommon. In fact, a common setup of the machine was to keep parts of the projector in a separate, adjoining room with only the aperture visible, to make it seem more magical and scare people. By the 18th century, use by charlatans was common for religious reasons. For example, Count Cagliostro used it to ‘raise dead spirits’ in Egyptian masonry. Johann Georg Schröpfer
used the magic lantern to conjure up images of dead people on smoke. He staged routines doing this at his coffee shop in Leipzig. He did this to scare people and make them think he was a good actor. Schröpfer ended up going crazy and thinking he himself was pursued by real devils, and shot himself after promising an audience he would later resurrect himself.
s were produced and marketed as toys for children. The opaque projector is a predecessor to the overhead projector
. The light source in early opaque projectors was often limelight
. Incandescent light bulb
s with halogen lamp
s taking over later.
In the late 1950s and early 1960s, overhead projectors began to be widely used in schools and businesses. The first overhead projector was used for police identification work. It used a cellophane roll over a 9-inch stage allowing facial characteristics to be rolled across the stage. The U.S. Army in 1945 was the first to use it in quantity for training as World War II
wound down.
Another type of projector called slide projector
s were common in the 1950s to the 1970s as a form of entertainment; family members and friends would gather to view slideshows.
Late in the 20th century, slides and transparencies were replaced with digital images.
Projection screen
A projection screen is an installation consisting of a surface and a support structure used for displaying a projected image for the view of an audience. Projection screens may be permanently installed, as in a movie theater; painted on the wall; or semi-permanent or mobile, as in a conference room...
.
Most projectors creates an image by shining a light through a small transparent image, but some newer types of projectors can project the image directly, by using lasers. A virtual retinal display
Virtual retinal display
A virtual retinal display , also known as a retinal scan display or retinal projector , is a display technology that draws a raster display directly onto the retina of the eye. The user sees what appears to be a conventional display floating in space in front of them...
, or retinal projector, is a projector that projects an image directly on the retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
instead of using an external projection screen.
The most common type of projector used today is called a video projector
Video projector
A video projector is an image projector that receives a video signal and projects the corresponding image on a projection screen using a lens system. All video projectors use a very bright light to project the image, and most modern ones can correct any curves, blurriness, and other...
. Video projectors are digital replacements for earlier types of projectors such as slide projector
Slide projector
A slide projector is an opto-mechanical device to view photographic slides. Slide projectors were common in the 1950s to the 1970s as a form of entertainment; family members and friends would gather to view slide shows...
s and overhead projector
Overhead projector
An overhead projector is a variant of slide projector that is used to display images to an audience.-Mechanism:An overhead projector typically consists of a large box containing a very bright lamp and a fan to cool it. On top of the box is a large fresnel lens that collimates the light...
s. These earlier types of projectors were mostly replaced with digital video projectors throughout the 1990s and early 2000s, but old analog projectors are still used some places. The newest types of projectors are handheld projector
Handheld projector
A Handheld projector is an emerging technology that applies the use of an image projector in a handheld device...
s that use laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
s or LED
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....
s to project images.
Movie theater
Movie theater
A movie theater, cinema, movie house, picture theater, film theater is a venue, usually a building, for viewing motion pictures ....
s use a type of projector called a movie projector
Movie projector
A movie projector is an opto-mechanical device for displaying moving pictures by projecting them on a projection screen. Most of the optical and mechanical elements, except for the illumination and sound devices, are present in movie cameras.-Physiology:...
.
Another type of projector is the enlarger
Enlarger
An enlarger is a specialized transparency projector used to produce photographic prints from film or glass negatives using the gelatin silver process, or from transparencies.-Construction:...
, a device used to produce photographic prints from negatives.
Early history of projectors and cameras
Projectors share a common history with cameraCamera
A camera is a device that records and stores images. These images may be still photographs or moving images such as videos or movies. The term camera comes from the camera obscura , an early mechanism for projecting images...
s. As far back as the 4th century BC, Greeks
Ancient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...
such as Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...
and Euclid
Euclid
Euclid , fl. 300 BC, also known as Euclid of Alexandria, was a Greek mathematician, often referred to as the "Father of Geometry". He was active in Alexandria during the reign of Ptolemy I...
wrote on naturally-occurring rudimentary pinhole camera
Pinhole camera
A pinhole camera is a simple camera without a lens and with a single small aperture – effectively a light-proof box with a small hole in one side. Light from a scene passes through this single point and projects an inverted image on the opposite side of the box...
s. For example, light may travel through the slits of wicker baskets or the crossing of tree leaves. (The circular dapples on a forest floor, actually pinhole images of the sun, can be seen to have a bite taken out of them during partial solar eclipses opposite to the position of the moon's actual occultation of the sun because of the inverting effect of pinhole lenses.)
It was the 10th-century Ibn al-Haytham (Alhazen), who published this idea in the Book of Optics
Book of Optics
The Book of Optics ; ; Latin: De Aspectibus or Opticae Thesaurus: Alhazeni Arabis; Italian: Deli Aspecti) is a seven-volume treatise on optics and other fields of study composed by the medieval Muslim scholar Alhazen .-See also:* Science in medieval Islam...
in 1021 AD. When Ibn al-Haytham began experiment
Experiment
An experiment is a methodical procedure carried out with the goal of verifying, falsifying, or establishing the validity of a hypothesis. Experiments vary greatly in their goal and scale, but always rely on repeatable procedure and logical analysis of the results...
ing with the camera obscura, he himself stated, Et nos non inventimus ita, "we did not invent this". He improved on the camera after realizing that the smaller the pinhole, the sharper the image (though the less light). He provides the first clear description for construction of a camera obscura
Camera obscura
The camera obscura is an optical device that projects an image of its surroundings on a screen. It is used in drawing and for entertainment, and was one of the inventions that led to photography. The device consists of a box or room with a hole in one side...
(Lat. dark chamber). As a side benefit of his invention, he was credited with being first man to shift physics from a philosophical to an experimental basis.
In the 5th century BC, the Mohist philosopher Mo Jing
Mozi
Mozi |Lat.]] as Micius, ca. 470 BC – ca. 391 BC), original name Mo Di , was a Chinese philosopher during the Hundred Schools of Thought period . Born in Tengzhou, Shandong Province, China, he founded the school of Mohism, and argued strongly against Confucianism and Daoism...
(墨經) in ancient China mentioned the effect of an inverted image forming through a pinhole. The image of an inverted Chinese pagoda
Chinese pagoda
Chinese Pagodas are a traditional part of Chinese architecture. In addition to religious use, since ancient times Chinese pagodas have been praised for the spectacular views which they offer, and many famous poems in Chinese history attest to the joy of scaling pagodas.-History:The pagoda is...
is mentioned in Duan Chengshi
Duan Chengshi
Duan Chengshi was an author and scholar of the Tang Dynasty in China. He was born to a wealthy family in present day Zibo, Shandong. A descendant of the early Tang official Duan Zhixuan 段志玄 , and the son of Duan Wenchang 段文昌, a high official under Tang Xuanzong, his family background enabled him...
's (d. 863) book Miscellaneous Morsels from Youyang
Miscellaneous Morsels from Youyang
The Miscellaneous Morsels from Youyang is a miscellany of Chinese and foreign legends and hearsay, reports on natural phenomena, short anecdotes, and tales of the wondrous and mundane, as well as notes on such topics as medicinal herbs and tattoos....
written during the Tang Dynasty
Tang Dynasty
The Tang Dynasty was an imperial dynasty of China preceded by the Sui Dynasty and followed by the Five Dynasties and Ten Kingdoms Period. It was founded by the Li family, who seized power during the decline and collapse of the Sui Empire...
(618–907). Along with experimenting with the pinhole camera and the burning mirror
Burning-glass
A burning glass or burning lens is a large convex lens that can concentrate the sun's rays onto a small area, heating up the area and thus resulting in ignition of the exposed surface. Burning mirrors achieve a similar effect by using reflecting surfaces to focus the light...
of the ancient Mohists, the Song Dynasty
Song Dynasty
The Song Dynasty was a ruling dynasty in China between 960 and 1279; it succeeded the Five Dynasties and Ten Kingdoms Period, and was followed by the Yuan Dynasty. It was the first government in world history to issue banknotes or paper money, and the first Chinese government to establish a...
(960–1279 AD) Chinese
Chinese people
The term Chinese people may refer to any of the following:*People with Han Chinese ethnicity ....
scientist Shen Kuo
Shen Kuo
Shen Kuo or Shen Gua , style name Cunzhong and pseudonym Mengqi Weng , was a polymathic Chinese scientist and statesman of the Song Dynasty...
(1031–1095) experimented with camera obscura and was the first to establish geometrical and quantitative
Quantitative property
A quantitative property is one that exists in a range of magnitudes, and can therefore be measured with a number. Measurements of any particular quantitative property are expressed as a specific quantity, referred to as a unit, multiplied by a number. Examples of physical quantities are distance,...
attributes for it.
In the 13th century, Robert Grosseteste
Robert Grosseteste
Robert Grosseteste or Grossetete was an English statesman, scholastic philosopher, theologian and Bishop of Lincoln. He was born of humble parents at Stradbroke in Suffolk. A.C...
and Roger Bacon
Roger Bacon
Roger Bacon, O.F.M. , also known as Doctor Mirabilis , was an English philosopher and Franciscan friar who placed considerable emphasis on the study of nature through empirical methods...
commented on the pinhole camera. Between 1000 and 1600, men such as Ibn al-Haytham, Gemma Frisius
Gemma Frisius
Gemma Frisius , was a physician, mathematician, cartographer, philosopher, and instrument maker...
, and Giambattista della Porta
Giambattista della Porta
Giambattista della Porta , also known as Giovanni Battista Della Porta and John Baptist Porta, was an Italian scholar, polymath and playwright who lived in Naples at the time of the Scientific Revolution and Reformation....
wrote on the pinhole camera, explaining why the images are upside down. Pinhole devices provide safety for the eyes when viewing solar eclipses because the event is observed indirectly, the diminished intensity of the pinhole image being harmless compared with the full glare of the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
itself.
The first image projectors
The first known record of what might portray the idea of projecting an image on a surface is a drawing by Johannes de Fontana from 1420. The drawing was of a nun holding something that might be a lanternLantern
A lantern is a portable lighting device or mounted light fixture used to illuminate broad areas. Lanterns may also be used for signaling, as 'torches', or as general light sources outdoors . Low light level varieties are used for decoration. The term "lantern" is also used more generically to...
. The lantern had a small translucent window that contained an image of a devil holding a lance http://www.precinemahistory.net/fontana.htm. Leonardo da Vinci
Leonardo da Vinci
Leonardo di ser Piero da Vinci was an Italian Renaissance polymath: painter, sculptor, architect, musician, scientist, mathematician, engineer, inventor, anatomist, geologist, cartographer, botanist and writer whose genius, perhaps more than that of any other figure, epitomized the Renaissance...
also made a similar sketch in 1515. These drawings are likely to have inspired the creation of the earliest image projector, a device called a magic lantern
Magic lantern
The magic lantern or Laterna Magica is an early type of image projector developed in the 17th century.-Operation:The magic lantern has a concave mirror in front of a light source that gathers light and projects it through a slide with an image scanned onto it. The light rays cross an aperture , and...
.
In the 17th century, a the first magic lantern
Magic lantern
The magic lantern or Laterna Magica is an early type of image projector developed in the 17th century.-Operation:The magic lantern has a concave mirror in front of a light source that gathers light and projects it through a slide with an image scanned onto it. The light rays cross an aperture , and...
was developed. With pinhole cameras and camera obscura it was only possible to project an image of actual scene, such as an image of the sun, on a surface. The magic lantern on the other hand could project a painted image on a surface, and marks the point where cameras and projectors became two different kinds of devices. There has been some debate about who the original inventor of the magic lantern is, but the most widely accepted theory is that Christiaan Huygens developed the original device in the late 1650s. However, other sources give credit to the German priest Athanasius Kircher
Athanasius Kircher
Athanasius Kircher was a 17th century German Jesuit scholar who published around 40 works, most notably in the fields of oriental studies, geology, and medicine...
. He describes a device such as the magic lantern in his book Ars Magna Lucis et Umbrae. There are possible mentions of this device associated with Kircher as early as 1646. Even in its earliest use, it was demonstrated with monstrous images such as the Devil. Huygen’s device was even referred to as the “lantern of fright” because it was able to project spooky images that looked like apparitions. In its early development, it was mostly used by magicians and conjurers to project images, making them appear or disappear, transform from one scene into a different scene, animate normally inanimate objects, or even create the belief of bringing the dead back to life.
In the 1660s, a man named Thomas Walgensten used his so-called “lantern of fear” to summon ghosts. These misuses of this early machine were not uncommon. In fact, a common setup of the machine was to keep parts of the projector in a separate, adjoining room with only the aperture visible, to make it seem more magical and scare people. By the 18th century, use by charlatans was common for religious reasons. For example, Count Cagliostro used it to ‘raise dead spirits’ in Egyptian masonry. Johann Georg Schröpfer
Johann Georg Schröpfer
Johann Georg Schröpfer was a German illusionist, freemason, and occultist. He was a pioneer of entertainment séances, being one of the first people to use a magic lantern to project the appearance of ghosts...
used the magic lantern to conjure up images of dead people on smoke. He staged routines doing this at his coffee shop in Leipzig. He did this to scare people and make them think he was a good actor. Schröpfer ended up going crazy and thinking he himself was pursued by real devils, and shot himself after promising an audience he would later resurrect himself.
The 20th century to present day
In the early and middle parts of the 20th century, a new type of low-cost projectors called opaque projectorOpaque projector
The opaque projector, epidioscope, epidiascope or episcope is a device which displays opaque materials by shining a bright lamp onto the object from above. A system of mirrors, prisms and/or imaging lenses is used to focus an image of the material onto a viewing screen...
s were produced and marketed as toys for children. The opaque projector is a predecessor to the overhead projector
Overhead projector
An overhead projector is a variant of slide projector that is used to display images to an audience.-Mechanism:An overhead projector typically consists of a large box containing a very bright lamp and a fan to cool it. On top of the box is a large fresnel lens that collimates the light...
. The light source in early opaque projectors was often limelight
Limelight
Limelight is a type of stage lighting once used in theatres and music halls. An intense illumination is created when an oxyhydrogen flame is directed at a cylinder of quicklime , which can be heated to 2572 °C before melting. The light is produced by a combination of incandescence and...
. Incandescent light bulb
Incandescent light bulb
The incandescent light bulb, incandescent lamp or incandescent light globe makes light by heating a metal filament wire to a high temperature until it glows. The hot filament is protected from air by a glass bulb that is filled with inert gas or evacuated. In a halogen lamp, a chemical process...
s with halogen lamp
Halogen lamp
A halogen lamp, also known as a tungsten halogen lamp, is an incandescent lamp with a tungsten filament contained within an inert gas and a small amount of a halogen such as iodine or bromine. The chemical halogen cycle redeposits evaporated tungsten back on to the filament, extending the life of...
s taking over later.
In the late 1950s and early 1960s, overhead projectors began to be widely used in schools and businesses. The first overhead projector was used for police identification work. It used a cellophane roll over a 9-inch stage allowing facial characteristics to be rolled across the stage. The U.S. Army in 1945 was the first to use it in quantity for training as World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
wound down.
Another type of projector called slide projector
Slide projector
A slide projector is an opto-mechanical device to view photographic slides. Slide projectors were common in the 1950s to the 1970s as a form of entertainment; family members and friends would gather to view slide shows...
s were common in the 1950s to the 1970s as a form of entertainment; family members and friends would gather to view slideshows.
Late in the 20th century, slides and transparencies were replaced with digital images.