![Vladimir Zworykin and historic TV tubes](https://upload.wikimedia.org/wikipedia/commons/2/28/Vladimir_Zworykin_and_historic_TV_tubes.jpg)
Video camera tubes were devices based on the
cathode ray tube that were used in
television camera
A professional video camera (often called a television camera even though its use has spread beyond television) is a high-end device for creating electronic moving images (as opposed to a movie camera, that earlier recorded the images on film). ...
s to capture
television
Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of television transmission. Television is a mass medium for advertisin ...
images, prior to the introduction of
charge-coupled device
A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...
(CCD)
image sensors in the 1980s. Several different types of tubes were in use from the early 1930s, and as late as the 1990s.
In these tubes, an
electron beam was scanned across an image of the scene to be broadcast focused on a target. This generated a current that was dependent on the brightness of the image on the target at the scan point. The size of the striking ray was tiny compared to the size of the target, allowing 483 horizontal
scan line
A scan line (also scanline) is one line, or row, in a raster scanning pattern, such as a line of video on a cathode ray tube (CRT) display of a television set or computer monitor.
On CRT screens the horizontal scan lines are visually discernible ...
s per image in the
NTSC
The first American standard for analog television broadcast was developed by National Television System Committee (NTSC)National Television System Committee (1951–1953), Report and Reports of Panel No. 11, 11-A, 12–19, with Some supplement ...
format, 576 lines in
PAL
Phase Alternating Line (PAL) is a colour encoding system for analogue television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (25 ...
, and as many as 1035 lines in
Hi-Vision
MUSE (Multiple sub-Nyquist Sampling Encoding), commercially known as Hi-Vision (a contraction of HIgh-definition teleVISION) was a Japanese analog HDTV system, with design efforts going back to 1979.
It used dot-interlacing and digital video co ...
.
Cathode ray tube
Any vacuum tube which operates using a focused beam of electrons, originally called
cathode ray
Cathode rays or electron beam (e-beam) are streams of electrons observed in discharge tubes. If an evacuated glass tube is equipped with two electrodes and a voltage is applied, glass behind the positive electrode is observed to glow, due to el ...
s, is known as a cathode ray tube (CRT). These are usually seen as display devices as used in older (i.e., non-
flat panel
A flat-panel display (FPD) is an electronic display used to display visual content such as text or images. It is present in consumer, medical, transportation, and industrial equipment.
Flat-panel displays are thin, lightweight, provide better l ...
) television receivers and computer displays. The camera pickup tubes described in this article are also CRTs, but they display no image.
["Cathode-ray tube." ''McGraw-Hill Concise Encyclopedia of Science & Technology.'' Third Ed., Sybil P. Parker, ed., McGraw-Hill, Inc., 1992, pp. 332-333.]
Early research
In June 1908, the scientific journal ''
Nature
Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are ...
'' published a letter in which
Alan Archibald Campbell-Swinton
Alan Archibald Campbell-Swinton FRS (18 October 1863 – 19 February 1930) was a Scottish consulting electrical engineer, who provided the theoretical basis for the electronic television, two decades before the technology existed to implement ...
, fellow of the
Royal Society
The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...
(
UK), discussed how a fully electronic television system could be realized by using
cathode ray tubes (or "Braun" tubes, after their inventor,
Karl Braun) as both imaging and display devices.
[
] He noted that the "real difficulties lie in devising an efficient transmitter", and that it was possible that "no photoelectric phenomenon at present known will provide what is required".
[
] A cathode ray tube was successfully demonstrated as a displaying device by the
German
German(s) may refer to:
* Germany (of or related to)
** Germania (historical use)
* Germans, citizens of Germany, people of German ancestry, or native speakers of the German language
** For citizens of Germany, see also German nationality law
**Ge ...
Professor Max Dieckmann in 1906; his experimental results were published by the journal ''
Scientific American
''Scientific American'', informally abbreviated ''SciAm'' or sometimes ''SA'', is an American popular science magazine. Many famous scientists, including Albert Einstein and Nikola Tesla, have contributed articles to it. In print since 1845, it ...
'' in 1909.
[
] Campbell-Swinton later expanded on his vision in a presidential address given to the Röntgen Society in November 1911. The photoelectric screen in the proposed transmitting device was a mosaic of isolated rubidium cubes.
[
][
] His concept for a fully electronic television system was later popularized as the ''"Campbell-Swinton Electronic Scanning System"'' by
Hugo Gernsback
Hugo Gernsback (; born Hugo Gernsbacher, August 16, 1884 – August 19, 1967) was a Luxembourgish–American editor and magazine publisher, whose publications including the first science fiction magazine. His contributions to the genre as pub ...
and H. Winfield Secor in the August 1915 issue of the popular magazine ''Electrical Experimenter''
[
][
] and by Marcus J. Martin in the 1921 book ''The electrical transmission of photographs''.
[
][
]
In a letter to ''
Nature
Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans are ...
'' published in October 1926, Campbell-Swinton also announced the results of some "not very successful experiments" he had conducted with G. M. Minchin and J. C. M. Stanton. They had attempted to generate an electrical signal by projecting an image onto a selenium-coated metal plate that was simultaneously scanned by a
cathode ray
Cathode rays or electron beam (e-beam) are streams of electrons observed in discharge tubes. If an evacuated glass tube is equipped with two electrodes and a voltage is applied, glass behind the positive electrode is observed to glow, due to el ...
beam.
[
] These experiments were conducted before March 1914, when Minchin died,
[
] but they were later repeated by two different teams in 1937, by H. Miller and J. W. Strange from
EMI
EMI Group Limited (originally an initialism for Electric and Musical Industries, also referred to as EMI Records Ltd. or simply EMI) was a British Transnational corporation, transnational Conglomerate (company), conglomerate founded in March 1 ...
,
[
] and by H. Iams and A. Rose from
RCA
The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Comp ...
.
[
] Both teams succeeded in transmitting "very faint" images with the original Campbell-Swinton's selenium-coated plate, but much better images were obtained when the metal plate was covered with zinc sulphide or selenide,
or with aluminum or zirconium oxide treated with caesium.
These experiments would form the base of the future
vidicon
Video camera tubes were devices based on the cathode ray tube that were used in television cameras to capture television images, prior to the introduction of charge-coupled device (CCD) image sensors in the 1980s. Several different types of tubes ...
. A description of a CRT imaging device also appeared in a patent application filed by
Edvard-Gustav Schoultz in
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...
in August 1921, and published in 1922,
[
] although a working device was not demonstrated until some years later.
Image dissector
![Farnsworth image dissector tube](https://upload.wikimedia.org/wikipedia/commons/a/a5/Farnsworth_image_dissector_tube.jpg)
An image dissector is a camera tube that creates an "electron image" of a scene from
photocathode
A photocathode is a surface engineered to convert light ( photons) into electrons using the photoelectric effect. Photocathodes are important in accelerator physics where they are utilised in a photoinjector to generate high brightness electron ...
emissions (electrons) which pass through a scanning aperture to an
anode
An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic ...
, which serves as an electron detector.
[Horowitz, Paul and Winfield Hill, ''The Art of Electronics'', Second Edition](_blank)
Cambridge University Press, 1989, pp. 1000-1001. . Among the first to design such a device were
German
German(s) may refer to:
* Germany (of or related to)
** Germania (historical use)
* Germans, citizens of Germany, people of German ancestry, or native speakers of the German language
** For citizens of Germany, see also German nationality law
**Ge ...
inventors
Max Dieckmann
Max or MAX may refer to:
Animals
* Max (dog) (1983–2013), at one time purported to be the world's oldest living dog
* Max (English Springer Spaniel), the first pet dog to win the PDSA Order of Merit (animal equivalent of OBE)
* Max (gorilla) ...
and
Rudolf Hell
Rudolf Hell (19 December 1901 – 11 March 2002) was a German inventor and engineer.
Career
Hell was born in Eggmühl. From 1919 to 1923, he studied electrical engineering in Munich. He worked there from 1923 to 1929 as assistant of Prof. ...
,
who had titled their 1925 patent application ''Lichtelektrische Bildzerlegerröhre für Fernseher'' (''Photoelectric Image Dissector Tube for Television'').
[
] The term may apply specifically to a dissector tube employing magnetic fields to keep the
electron image in focus,
an element lacking in Dieckmann and Hell's design, and in the early dissector tubes built by American inventor
Philo Farnsworth
Philo Taylor Farnsworth (August 19, 1906 – March 11, 1971) was an American inventor and television pioneer. He made many crucial contributions to the early development of all-electronic television. He is best known for his 1927 invention of t ...
.
[
]
Dieckmann and Hell submitted their application to the German patent office in April 1925, and a patent was issued in October 1927.
Their experiments on the image dissector were announced in the volume 8 (September 1927) of the popular magazine ''Discovery''
[
] and in the May 1928 issue of the magazine ''Popular Radio''.
[
] However, they never transmitted a clear and well focused image with such a tube.
In January 1927, American inventor and television pioneer
Philo T. Farnsworth
Philo Taylor Farnsworth (August 19, 1906 – March 11, 1971) was an American inventor and television pioneer. He made many crucial contributions to the early development of all-electronic television. He is best known for his 1927 invention of t ...
applied for a patent for his ''Television System'' that included a device for "the conversion and dissecting of light".
Its first moving image was successfully transmitted on September 7 of 1927,
[
]
and a patent was issued in 1930.
Farnsworth quickly made improvements to the device, among them introducing an
electron multiplier
An electron multiplier is a vacuum-tube structure that multiplies incident charges. In a process called secondary emission, a single electron can, when bombarded on secondary-emissive material, induce emission of roughly 1 to 3 electrons. If an el ...
made of nickel
[
][
] and using a "longitudinal magnetic field" in order to sharply
focus the electron image.
[
]
The improved device was demonstrated to the press in early September 1928.
[Farnsworth, Elma, ''Distant Vision: Romance and Discovery on an Invisible Frontier'', Salt Lake City, PemberlyKent, 1989, pp. 108-109.]
The introduction of a
multipactor The multipactor effect is a phenomenon in radio-frequency (RF) amplifier vacuum tubes and waveguides, where, under certain conditions, secondary electron emission in resonance with an alternating electric field leads to exponential electron multipli ...
in October 1933
[
][
] and a multi-
dynode
A dynode is an electrode in a vacuum tube
A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential diff ...
"electron multiplier" in 1937
[
][
] made Farnsworth's image dissector the first practical version of a fully electronic imaging device for television.
[Abramson, Albert (1987), ''The History of Television, 1880 to 1941''. Jefferson, NC: Albert Abramson. p. 159. .] Unfortunately, it had very poor
light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...
sensitivity, and was therefore primarily useful only where illumination was exceptionally high (typically over 685
cd/m
2).
[
][
][
] However, it was ideal for industrial applications, such as monitoring the bright interior of an industrial furnace. Due to their poor light sensitivity, image dissectors were rarely used in television broadcasting, except to scan film and other transparencies.
In April 1933, Farnsworth submitted a patent application also entitled ''Image Dissector'', but which actually detailed a
CRT-type camera tube.
This is among the first patents to propose the use of a "low-velocity" scanning beam and RCA had to buy it in order to sell image orthicon tubes to the general public.
[
] However, Farnsworth never transmitted a clear and well focused image with such a tube.
[
]
Operation
The
optical
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...
system of the image dissector focuses an image onto a photocathode mounted inside a high vacuum. As light strikes the photocathode, electrons are emitted in proportion to the intensity of the light (see
photoelectric effect
The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and solid sta ...
). The entire electron image is deflected and a scanning aperture permits only those electrons emanating from a very small area of the photocathode to be captured by the detector at any given time. The output from the detector is an electric current whose magnitude is a measure of the brightness of the corresponding area of the image. The electron image is
periodically deflected horizontally and vertically ("
raster scan
A raster scan, or raster scanning, is the rectangular pattern of image capture and reconstruction in television. By analogy, the term is used for raster graphics, the pattern of image storage and transmission used in most computer bitmap image ...
ning") such that the entire image is read by the detector many times per second, producing an electrical signal that can be conveyed to a
display device, such as a CRT monitor, to reproduce the image.
The image dissector has no "
charge storage" characteristic; the vast majority of electrons emitted by the photocathode are excluded by the scanning aperture,
and thus wasted rather than being stored on a photo-sensitive target, as in the iconoscope or image orthicon (see below), which largely accounts for its low light sensitivity.
Iconoscope
![Zworykin1931iconoscope](https://upload.wikimedia.org/wikipedia/commons/1/1b/Zworykin1931iconoscope.png)
An iconoscope is a camera tube that projects an image on a special
charge storage plate containing a mosaic of electrically isolated photosensitive granules separated from a common plate by a thin layer of isolating material, somewhat analogous to the
human eye's
retina
The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then ...
and its arrangement of
photoreceptors. Each photosensitive granule constitutes a tiny capacitor that accumulates and stores electrical charge in response to the light striking it. An
electron beam periodically sweeps across the plate, effectively scanning the stored image and discharging each capacitor in turn such that the electrical output from each capacitor is proportional to the average intensity of the light striking it between each discharge event.
[
]
After Hungarian engineer
Kálmán Tihanyi
Kálmán Tihanyi or in English language technical literature often mentioned as Coloman Tihanyi or Koloman Tihanyi (28 April 1897 – 26 February 1947) was a Hungarian physicist, electrical engineer and inventor. One of the early pioneers ...
studied
Maxwell's equations
Maxwell's equations, or Maxwell–Heaviside equations, are a set of coupled partial differential equations that, together with the Lorentz force law, form the foundation of classical electromagnetism, classical optics, and electric circuits.
...
, he discovered a new hitherto unknown physical phenomenon, which led to a break-through in the development of electronic imaging devices. He named the new phenomenon as charge-storage principle. (further information:
Charge-storage principle)
The problem of low sensitivity to light resulting in low electrical output from transmitting or camera tubes would be solved with the introduction of charge-storage technology by the Hungarian engineer
Kálmán Tihanyi
Kálmán Tihanyi or in English language technical literature often mentioned as Coloman Tihanyi or Koloman Tihanyi (28 April 1897 – 26 February 1947) was a Hungarian physicist, electrical engineer and inventor. One of the early pioneers ...
in the beginning of 1925.
["Kálmán Tihanyi (1897–1947)", ''IEC Techline''](_blank)
International Electrotechnical Commission (IEC), 2009-07-15. His solution was a camera tube that accumulated and stored electrical charges (
photoelectrons) within the tube throughout each scanning cycle. The device was first described in a patent application he filed in
Hungary
Hungary ( hu, Magyarország ) is a landlocked country in Central Europe. Spanning of the Pannonian Basin, Carpathian Basin, it is bordered by Slovakia to the north, Ukraine to the northeast, Romania to the east and southeast, Serbia to the ...
in March 1926 for a television system he dubbed Radioskop.
["Kálmán Tihanyi's 1926 Patent Application 'Radioskop'"](_blank)
''Memory of the World'', United Nations Educational, Scientific and Cultural Organization (UNESCO
The United Nations Educational, Scientific and Cultural Organization is a specialized agency of the United Nations (UN) aimed at promoting world peace and security through international cooperation in education, arts, sciences and culture. It ...
), 2005, retrieved 2009-01-29. After further refinements included in a 1928 patent application,
Tihanyi's patent was declared void in Great Britain in 1930,
[Tihanyi, Koloman, ''Improvements in television apparatus''](_blank)
European Patent Office, Patent No. GB313456. Convention date UK application: 1928-06-11, declared void and published: 1930-11-11, retrieved: 2013-04-25. and so he applied for patents in the United States. Tihanyi's charge storage idea remains a basic principle in the design of imaging devices for television to the present day.
In 1923, while employed by the
Westinghouse Electric Corporation
The Westinghouse Electric Corporation was an American manufacturing company founded in 1886 by George Westinghouse. It was originally named "Westinghouse Electric & Manufacturing Company" and was renamed "Westinghouse Electric Corporation" in ...
in Pittsburgh, Pennsylvania, Russian-born American engineer
Vladimir Zworykin
Vladimir Kosma Zworykin; or with the patronymic as ''Kosmich''; or russian: Кузьмич, translit=Kuz'mich, label=none. Zworykin anglicized his name to ''Vladimir Kosma Zworykin'', replacing the patronymic with the name ''Kosma'' as a middle ...
presented a project for a totally electronic television system to the company's general manager. In July 1925, Zworykin submitted a patent application titled ''Television System'' that included a charge storage plate constructed of a thin layer of isolating material (aluminum oxide) sandwiched between a screen (300 mesh) and a colloidal deposit of photoelectric material (potassium hydride) consisting of isolated globules.
[
] The following description can be read between lines 1 and 9 in page 2: "The photoelectric material, such as potassium hydride, is evaporated on the aluminum oxide, or other insulating medium, and treated so as to form a colloidal deposit of potassium hydride consisting of minute globules. Each globule is very active photoelectrically and constitutes, to all intents and purposes, a minute individual photoelectric cell". Its first image was transmitted in late summer of 1925,
and a patent was issued in 1928.
However the quality of the transmitted image failed to impress H.P. Davis, the general manager of
Westinghouse, and Zworykin was asked "to work on something useful".
A patent for a television system was also filed by
Zworykin
Vladimir Kosma Zworykin; or with the patronymic as ''Kosmich''; or russian: Кузьмич, translit=Kuz'mich, label=none. Zworykin anglicized his name to ''Vladimir Kosma Zworykin'', replacing the patronymic with the name ''Kosma'' as a middle na ...
in 1923, but this filing is not a definitive reference because extensive revisions were done before a patent was issued fifteen years later
and the file itself was divided into two patents in 1931.
[
][
]
The first practical iconoscope was constructed in 1931 by Sanford Essig, when he accidentally left a silvered mica sheet in the oven too long. Upon examination with a microscope, he noticed that the silver layer had broken up into a myriad of tiny isolated silver globules.
He also noticed that, "the tiny dimension of the silver droplets would enhance the image resolution of the iconoscope by a quantum leap".
[
] As head of television development at
Radio Corporation of America (RCA), Zworykin submitted a patent application in November 1931, and it was issued in 1935.
Nevertheless, Zworykin's team was not the only engineering group working on devices that used a charge storage plate. In 1932, the
EMI
EMI Group Limited (originally an initialism for Electric and Musical Industries, also referred to as EMI Records Ltd. or simply EMI) was a British Transnational corporation, transnational Conglomerate (company), conglomerate founded in March 1 ...
engineers Tedham and McGee under the supervision of
Isaac Shoenberg
Sir Isaac Shoenberg (1 March 1880 – 25 January 1963) was a British electronic engineer born in Belarus who was best known for his role in the history of television. He was the head of the EMI research team that developed the 405-line (Marconi-EM ...
applied for a patent for a new device they dubbed the "Emitron".
[
] A
405-line broadcasting service employing the Emitron began at studios in
Alexandra Palace in 1936, and patents were issued in the United Kingdom in 1934 and in the US in 1937.
[
]
The iconoscope was presented to the general public at a press conference in June 1933,
[
] and two detailed technical papers were published in September and October of the same year.
[
][
] Unlike the Farnsworth image dissector, the Zworykin iconoscope was much more sensitive, useful with an illumination on the target between 4
ft-c (43
lx) and 20
ft-c (215
lx). It was also easier to manufacture and produced a very clear image. The iconoscope was the primary camera tube used by RCA broadcasting from 1936 until 1946, when it was replaced by the image orthicon tube.
[
]
Super-Emitron and image iconoscope
The original iconoscope was noisy, had a high ratio of interference to signal, and ultimately gave disappointing results, especially when compared to the high definition mechanical scanning systems then becoming available.
The
EMI
EMI Group Limited (originally an initialism for Electric and Musical Industries, also referred to as EMI Records Ltd. or simply EMI) was a British Transnational corporation, transnational Conglomerate (company), conglomerate founded in March 1 ...
team under the supervision of
Isaac Shoenberg
Sir Isaac Shoenberg (1 March 1880 – 25 January 1963) was a British electronic engineer born in Belarus who was best known for his role in the history of television. He was the head of the EMI research team that developed the 405-line (Marconi-EM ...
analyzed how the Emitron (or iconoscope) produces an electronic signal and concluded that its real efficiency was only about 5% of the theoretical maximum. This is because
secondary electrons released from the mosaic of the charge storage plate when the scanning beam sweeps across it may be attracted back to the positively charged mosaic, thus neutralizing many of the stored charges.
[
] Lubszynski, Rodda, and McGee realized that the best solution was to separate the photo-emission function from the charge storage one, and so communicated their results to Zworykin.
The new video camera tube developed by Lubszynski, Rodda and McGee in 1934 was dubbed "the super-Emitron". This tube is a combination of the image dissector and the Emitron. It has an efficient
photocathode
A photocathode is a surface engineered to convert light ( photons) into electrons using the photoelectric effect. Photocathodes are important in accelerator physics where they are utilised in a photoinjector to generate high brightness electron ...
that transforms the scene light into an electron image; the latter is then accelerated towards a target specially prepared for the emission of
secondary electrons. Each individual electron from the electron image produces several secondary electrons after reaching the target, so that an amplification effect is produced. The target is constructed of a mosaic of electrically isolated metallic granules separated from a common plate by a thin layer of isolating material, so that the positive charge resulting from the
secondary emission is stored in the granules. Finally, an electron beam periodically sweeps across the target, effectively scanning the stored image, discharging each granule, and producing an electronic signal like in the iconoscope.
[
][
][
]
The super-Emitron was between ten and fifteen times more sensitive than the original Emitron and iconoscope tubes and, in some cases, this ratio was considerably greater.
It was used for an
outside broadcast
Outside broadcasting (OB) is the electronic field production (EFP) of television or radio programmes (typically to cover television news and sports television events) from a mobile remote broadcast television studio. Professional video camera a ...
by the BBC, for the first time, on Armistice Day 1937, when the general public could watch in a television set how the King laid a wreath at the Cenotaph. This was the first time that anyone could broadcast a live street scene from cameras installed on the roof of neighboring buildings.
[
]
On the other hand, in 1934, Zworykin shared some patent rights with the German licensee company Telefunken.
The image iconoscope (Superikonoskop in Germany) was produced as a result of the collaboration. This tube is essentially identical to the super-Emitron, but the target is constructed of a thin layer of isolating material placed on top of a conductive base, the mosaic of metallic granules is missing. The production and commercialization of the super-Emitron and image iconoscope in Europe were not affected by the
patent war
A patent war is a "battle" between corporations or individuals to secure patents for litigation, whether offensively or defensively. There are ongoing patent wars between the world's largest technology and software corporations. Contemporary pat ...
between Zworykin and Farnsworth, because Dieckmann and Hell had priority in Germany for the invention of the image dissector, having submitted a patent application for their ''Lichtelektrische Bildzerlegerröhre für Fernseher'' (''Photoelectric Image Dissector Tube for Television'') in Germany in 1925,
two years before Farnsworth did the same in the United States.
The image iconoscope (Superikonoskop) became the industrial standard for public broadcasting in Europe from 1936 until 1960, when it was replaced by the vidicon and plumbicon tubes. Indeed, it was the representative of the European tradition in electronic tubes competing against the American tradition represented by the image orthicon.
[
] The German company Heimann produced the Superikonoskop for the 1936 Berlin Olympic Games,
[
][
] later Heimann also produced and commercialized it from 1940 to 1955,
[
] finally the Dutch company
Philips
Koninklijke Philips N.V. (), commonly shortened to Philips, is a Dutch multinational conglomerate corporation that was founded in Eindhoven in 1891. Since 1997, it has been mostly headquartered in Amsterdam, though the Benelux headquarters i ...
produced and commercialized the image iconoscope and multicon from 1952 to 1963,
[
] when it was replaced by the much better
Plumbicon
Video camera tubes were devices based on the cathode ray tube that were used in television cameras to capture television images, prior to the introduction of charge-coupled device (CCD) image sensors in the 1980s. Several different types of tubes ...
.
[
][
]
Operation
The super-Emitron is a combination of the image dissector and the Emitron. The scene image is projected onto an efficient continuous-film semitransparent
photocathode
A photocathode is a surface engineered to convert light ( photons) into electrons using the photoelectric effect. Photocathodes are important in accelerator physics where they are utilised in a photoinjector to generate high brightness electron ...
that transforms the scene light into a light-emitted electron image, the latter is then accelerated (and
focused) via electromagnetic fields towards a target specially prepared for the emission of
secondary electrons. Each individual electron from the electron image produces several secondary electrons after reaching the target, so that an amplification effect is produced, and the resulting positive charge is proportional to the integrated intensity of the scene light. The target is constructed of a mosaic of electrically isolated metallic granules separated from a common plate by a thin layer of isolating material, so that the positive charge resulting from the
secondary emission is stored in the capacitor formed by the metallic granule and the common plate. Finally, an electron beam periodically sweeps across the target, effectively scanning the stored image and discharging each capacitor in turn such that the electrical output from each capacitor is proportional to the average intensity of the scene light between each discharge event (as in the iconoscope).
The image iconoscope is essentially identical to the super-Emitron, but the target is constructed of a thin layer of isolating material placed on top of a conductive base, the mosaic of metallic granules is missing. Therefore, secondary electrons are emitted from the surface of the isolating material when the electron image reaches the target, and the resulting positive charges are stored directly onto the surface of the isolated material.
Orthicon and CPS Emitron
The original iconoscope was very noisy
due to the secondary electrons released from the photoelectric mosaic of the charge storage plate when the scanning beam swept it across.
An obvious solution was to scan the mosaic with a low-velocity electron beam which produced less energy in the neighborhood of the plate such that no secondary electrons were emitted at all. That is, an image is projected onto the photoelectric mosaic of a charge storage plate, so that positive charges are produced and stored there due to
photo-emission and
capacitance
Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized ar ...
, respectively. These stored charges are then gently discharged by a ''low-velocity electron scanning beam'', preventing the emission of secondary electrons.
[
][
] Not all the electrons in the scanning beam may be absorbed in the mosaic, because the stored positive charges are proportional to the integrated intensity of the scene light. The remaining electrons are then deflected back into the anode,
captured by a special
grid
Grid, The Grid, or GRID may refer to:
Common usage
* Cattle grid or stock grid, a type of obstacle is used to prevent livestock from crossing the road
* Grid reference, used to define a location on a map
Arts, entertainment, and media
* News ...
,
[
][
][
] or deflected back into an
electron multiplier
An electron multiplier is a vacuum-tube structure that multiplies incident charges. In a process called secondary emission, a single electron can, when bombarded on secondary-emissive material, induce emission of roughly 1 to 3 electrons. If an el ...
.
[
]
''Low-velocity scanning beam'' tubes have several advantages; there are low levels of spurious signals and high efficiency of conversion of light into signal, so that the signal output is maximum. However, there are serious problems as well, because the electron beam spreads and accelerates in a direction parallel to the target when it scans the image's borders and corners, so that it produces secondary electrons and one gets an image that is well focused in the center but blurry in the borders.
[
] Henroteau was among the first inventors to propose in 1929 the use of ''low-velocity electrons'' for stabilizing the potential of a charge storage plate,
[
] but Lubszynski and the
EMI
EMI Group Limited (originally an initialism for Electric and Musical Industries, also referred to as EMI Records Ltd. or simply EMI) was a British Transnational corporation, transnational Conglomerate (company), conglomerate founded in March 1 ...
team were the first engineers in transmitting a clear and well focused image with such a tube.
Another improvement is the use of a semitransparent charge storage plate. The scene image is then projected onto the back side of the plate, while the low-velocity electron beam scans the photoelectric mosaic at the front side. This configurations allows the use of a straight camera tube, because the scene to be transmitted, the charge storage plate, and the electron gun can be aligned one after the other.
![EMI CPS Emitron Camera Head, 1950 (7649950230)](https://upload.wikimedia.org/wikipedia/commons/f/f2/EMI_CPS_Emitron_Camera_Head%2C_1950_%287649950230%29.jpg)
The first fully functional low-velocity scanning beam tube, the CPS Emitron, was invented and demonstrated by the
EMI
EMI Group Limited (originally an initialism for Electric and Musical Industries, also referred to as EMI Records Ltd. or simply EMI) was a British Transnational corporation, transnational Conglomerate (company), conglomerate founded in March 1 ...
team under the supervision of Sir
Isaac Shoenberg
Sir Isaac Shoenberg (1 March 1880 – 25 January 1963) was a British electronic engineer born in Belarus who was best known for his role in the history of television. He was the head of the EMI research team that developed the 405-line (Marconi-EM ...
. In 1934, the EMI engineers Blumlein and McGee filed for patents for ''television transmitting systems'' where a charge storage plate was shielded by a pair of special
grids, a negative (or slightly positive) grid lay very close to the plate, and a positive one was placed further away.
The velocity and energy of the electrons in the scanning beam were reduced to zero by the decelerating electric field generated by this pair of grids, and so a low-velocity scanning beam tube was obtained.
[
] The
EMI
EMI Group Limited (originally an initialism for Electric and Musical Industries, also referred to as EMI Records Ltd. or simply EMI) was a British Transnational corporation, transnational Conglomerate (company), conglomerate founded in March 1 ...
team kept working on these devices, and Lubszynski discovered in 1936 that a clear image could be produced if the trajectory of the low-velocity scanning beam was nearly perpendicular (orthogonal) to the charge storage plate in a neighborhood of it.
[
] The resulting device was dubbed the cathode potential stabilized Emitron, or CPS Emitron.
[
] The industrial production and commercialization of the CPS Emitron had to wait until the end of the
second world war
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposi ...
;
[
] it was widely used in the UK until 1963, when it was replaced by the much better
Plumbicon
Video camera tubes were devices based on the cathode ray tube that were used in television cameras to capture television images, prior to the introduction of charge-coupled device (CCD) image sensors in the 1980s. Several different types of tubes ...
.
On the other side of the
Atlantic
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...
, the
RCA
The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Comp ...
team led by
Albert Rose began working in 1937 on a low-velocity scanning beam device they dubbed the orthicon.
[
] Iams and Rose solved the problem of guiding the beam and keeping it in focus by installing specially designed deflection plates and deflection coils near the charge storage plate to provide a
uniform axial magnetic field.
[
] The orthicon was the tube used in RCA's television demonstration at the
1939 New York World's Fair,
its performance was similar to the image iconoscope's one,
[
] but it was also unstable under sudden flashes of bright light, producing "the appearance of a large drop of water evaporating slowly over part of the scene".
Image orthicon
![Orthicon](https://upload.wikimedia.org/wikipedia/commons/b/b0/Orthicon.svg)
The image orthicon (sometimes abbreviated IO), was common in American broadcasting from 1946 until 1968. A combination of the
image dissector
An image dissector, also called a dissector tube, is a video camera tube in which photocathode emissions create an "electron image" which is then swept up, down and across an anode to produce an electrical signal representing the visual image. It e ...
and the orthicon technologies, it replaced the
iconoscope in the United States, which required a great deal of
light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...
to work adequately.
The image orthicon tube was developed at RCA by Albert Rose, Paul K. Weimer, and Harold B. Law. It represented a considerable advance in the television field, and after further development work, RCA created original models between 1939 and 1940. The
National Defense Research Committee
The National Defense Research Committee (NDRC) was an organization created "to coordinate, supervise, and conduct scientific research on the problems underlying the development, production, and use of mechanisms and devices of warfare" in the Un ...
entered into a contract with RCA where the NDRC paid for its further development. Upon RCA's development of the more sensitive image orthicon tube in 1943, RCA entered into a production contract with the
U.S. Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage o ...
, the first tubes being delivered in January 1944. RCA began production of image orthicons for civilian use in the second quarter of 1946.
While the
iconoscope and the intermediate orthicon used capacitance between a multitude of small but discrete light sensitive collectors and an isolated signal plate for reading video information, the image orthicon employed direct charge readings from a continuous electronically charged collector. The resultant signal was immune to most extraneous signal
crosstalk from other parts of the target, and could yield extremely detailed images. For instance, image orthicon cameras were still being used by
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the US federal government responsible for the civil List of government space agencies, space program ...
for capturing Apollo/Saturn rockets nearing orbit, although the television networks had phased the cameras out. Only they could provide sufficient detail.
An image orthicon camera can take television pictures by candlelight because of the more ordered light-sensitive area and the presence of an electron multiplier at the base of the tube, which operated as a high-efficiency amplifier. It also has a
logarithmic light sensitivity curve similar to the
human eye. However, it tends to
flare
A flare, also sometimes called a fusée, fusee, or bengala in some Latin-speaking countries, is a type of pyrotechnic that produces a bright light or intense heat without an explosion. Flares are used for distress signaling, illumination, ...
in bright light, causing a dark halo to be seen around the object; this anomaly was referred to as
blooming
Bloom or blooming may refer to:
Science and technology Biology
* Bloom, one or more flowers on a flowering plant
* Algal bloom, a rapid increase or accumulation in the population of algae in an aquatic system
* Jellyfish bloom, a collective n ...
in the broadcast industry when image orthicon tubes were in operation.
[dtic.mil](_blank)
Westinghouse Non-blooming Image Orthicon. Image orthicons were used extensively in the early color television cameras, where the increased sensitivity of the tube was essential to overcome the very inefficient optical system of the camera.
The image orthicon tube was at one point colloquially referred to as an Immy.
Harry Lubcke, the then-President of the
Academy of Television Arts & Sciences, decided to have their award named after this nickname. Since the
statuette was female, it was
feminized into
Emmy.
Operation
An image orthicon consists of three parts: a
photocathode
A photocathode is a surface engineered to convert light ( photons) into electrons using the photoelectric effect. Photocathodes are important in accelerator physics where they are utilised in a photoinjector to generate high brightness electron ...
with an image store (target), a scanner that reads this image (an
electron gun
An electron gun (also called electron emitter) is an electrical component in some vacuum tubes that produces a narrow, collimated electron beam that has a precise kinetic energy. The largest use is in cathode-ray tubes (CRTs), used in nearly ...
), and a multistage electron multiplier.
In the image store, light falls upon the photocathode which is a photosensitive plate at a very negative potential (approx. -600 V), and is converted into an electron image (a principle borrowed from the image dissector). This electron rain is then accelerated towards the target (a very thin glass plate acting as a semi-isolator) at ground potential (0 V), and passes through a very fine wire mesh (nearly 200 wires per cm), very near (a few hundredths of a cm) and parallel to the target, acting as a
screen grid
A tetrode is a vacuum tube (called ''valve'' in British English) having four active electrodes. The four electrodes in order from the centre are: a thermionic cathode, first and second grids and a plate (called ''anode'' in British English). T ...
at a slightly positive voltage (approx +2 V). Once the image electrons reach the target, they cause a splash of electrons by the effect of
secondary emission. On average, each image electron ejects several splash electrons (thus adding amplification by secondary emission), and these excess electrons are soaked up by the positive mesh effectively removing electrons from the target and causing a positive charge on it in relation to the incident light in the photocathode. The result is an image painted in positive charge, with the brightest portions having the largest positive charge.
A sharply focused beam of electrons (a cathode ray) is generated by the
electron gun
An electron gun (also called electron emitter) is an electrical component in some vacuum tubes that produces a narrow, collimated electron beam that has a precise kinetic energy. The largest use is in cathode-ray tubes (CRTs), used in nearly ...
at ground potential and accelerated by the anode (the first
dynode
A dynode is an electrode in a vacuum tube
A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential diff ...
of the
electron multiplier
An electron multiplier is a vacuum-tube structure that multiplies incident charges. In a process called secondary emission, a single electron can, when bombarded on secondary-emissive material, induce emission of roughly 1 to 3 electrons. If an el ...
) around the gun at a high positive voltage (approx. +1500 V). Once it exits the electron gun, its inertia makes the beam move away from the dynode towards the back side of the target. At this point the electrons lose speed and get deflected by the horizontal and vertical deflection coils, effectively scanning the target. Thanks to the
axial magnetic field of the focusing coil, this deflection is not in a straight line, thus when the electrons reach the target they do so perpendicularly avoiding a sideways component. The target is nearly at ground potential with a small positive charge, thus when the electrons reach the target at low speed they are absorbed without ejecting more electrons. This adds negative charge to the positive charge until the region being scanned reaches some threshold negative charge, at which point the scanning electrons are reflected by the negative potential rather than absorbed (in this process the target recovers the electrons needed for the next scan). These reflected electrons return down the cathode ray tube toward the first dynode of the electron multiplier surrounding the electron gun which is at high potential. The number of reflected electrons is a linear measure of the target's original positive charge, which, in turn, is a measure of brightness.
Dark halo
The mysterious dark "orthicon halo" around bright objects in an orthicon-captured image (also known as "blooming") is based on the fact that the IO relies on the emission of photoelectrons, but very bright illumination can produce more of them locally than the device can successfully deal with. At a very bright point on a captured image, a great preponderance of electrons is ejected from the photosensitive plate. So many may be ejected that the corresponding point on the collection mesh can no longer soak them up, and thus they fall back to nearby spots on the target instead, much as water splashes in a ring when a rock is thrown into it. Since the resultant splashed electrons do not contain sufficient energy to eject further electrons where they land, they will instead neutralize any positive charge that has been built-up in that region. Since darker images produce less positive charge on the target, the excess electrons deposited by the splash will be read as a dark region by the scanning electron beam.
This effect was actually cultivated by tube manufacturers to a certain extent, as a
small, carefully controlled amount of the dark halo has the effect of crispening the visual image due to the
contrast effect
A contrast effect is the enhancement or diminishment, relative to normal, of perception, cognition or related performance as a result of successive (immediately previous) or simultaneous exposure to a stimulus of lesser or greater value in the sa ...
. (That is, giving the illusion of being more sharply focused than it actually is). The later vidicon tube and its descendants (see below) do not exhibit this effect, and so could not be used for broadcast purposes until special detail correction circuitry could be developed.
Vidicon
A vidicon tube is a video camera tube design in which the target material is a photoconductor. The vidicon was developed in the 1950s at RCA by P. K. Weimer, S. V. Forgue and R. R. Goodrich as a simple alternative to the structurally and electrically complex image orthicon. While the initial photoconductor used was selenium, other targets—including silicon diode arrays—have been used.
The vidicon is a storage-type camera tube in which a charge-density pattern is formed by the imaged scene radiation on a
photoconductive
Photoconductivity is an optical and electrical phenomenon in which a material becomes more electrically conductive due to the absorption of electromagnetic radiation such as visible light, ultraviolet light, infrared light, or gamma radiation.
Whe ...
surface which is then scanned by a beam of low-velocity
electron
The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary particles because they have no ...
s. The fluctuating voltage coupled out to a video
amplifier
An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost t ...
can be used to reproduce the scene being imaged. The electrical charge produced by an image will remain in the face plate until it is scanned or until the charge dissipates. By using a
pyroelectric
Pyroelectricity (from the two Greek words ''pyr'' meaning fire, and electricity) is a property of certain crystals which are naturally electrically polarized and as a result contain large electric fields. Pyroelectricity can be described as the a ...
material such as
triglycine sulfate
Triglycine sulfate (TGS) is a chemical compound with a formula (NH2CH2COOH)3·H2SO4. The empirical formula of TGS does not represent the molecular structure, which contains protonated glycine moieties and sulfate ions. TGS with protons replaced by ...
(TGS) as the target, a vidicon sensitive over a broad portion of the
infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
spectrum is possible. This technology was a precursor to modern microbolometer technology, and mainly used in firefighting thermal cameras.
Prior to the design and construction of the
Galileo probe to
Jupiter
Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth t ...
, in the late 1970s to early 1980s
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the US federal government responsible for the civil List of government space agencies, space program ...
used vidicon cameras on nearly all the unmanned deep space probes equipped with the remote sensing ability. Vidicon tubes were also used aboard the first three
Landsat
The Landsat program is the longest-running enterprise for acquisition of satellite imagery of Earth. It is a joint NASA / USGS program. On 23 July 1972, the Earth Resources Technology Satellite was launched. This was eventually renamed to La ...
earth imaging satellites launched in 1972, as part of each spacecraft's
Return Beam Vidicon
Return may refer to:
In business, economics, and finance
* Return on investment (ROI), the financial gain after an expense.
* Rate of return, the financial term for the profit or loss derived from an investment
* Tax return, a blank document or t ...
(RBV) imaging system.
The
Uvicon
The Orbiting Astronomical Observatory 2 (OAO-2, nicknamed ''Stargazer'') was the first successful space telescope (first space telescope being OAO-1, which failed to operate once in orbit), launched on December 7, 1968. An Atlas-Centaur rocket lau ...
, a UV-variant Vidicon was also used by NASA for UV duties.
Vidicon tubes were popular in 1970s and 1980s, after which they were rendered obsolete by
solid-state
Solid state, or solid matter, is one of the four fundamental states of matter.
Solid state may also refer to:
Electronics
* Solid-state electronics, circuits built of solid materials
* Solid state ionics, study of ionic conductors and their use ...
image sensors, with the
charge-coupled device
A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...
(CCD) and then the
CMOS sensor
An active-pixel sensor (APS) is an image sensor where each pixel sensor unit cell has a photodetector (typically a pinned photodiode) and one or more active transistors. In a metal–oxide–semiconductor (MOS) active-pixel sensor, MOS field-effec ...
.
All vidicon and similar tubes are prone to image lag, better known as ghosting, smearing, burn-in, comet tails, luma trails and luminance blooming. Image lag is visible as noticeable (usually white or colored) trails that appear after a bright object (such as a light or reflection) has moved, leaving a trail that eventually fades into the image. The trail itself does not move, rather it progressively fades as time passes, so areas that were exposed first fade before areas that were later exposed fade. It cannot be avoided or eliminated, as it is inherent to the technology. To what degree the image generated by the vidicon is affected will depend on the properties of the target material used on the vidicon, and the capacitance of the target material (known as the storage effect) as well as the resistance of the electron beam used to scan the target. The higher the capacitance of the target, the higher the charge it can hold and the longer it will take for the trail to disappear. The remmanant charges on the target eventually dissipate making the trail disappear.
Plumbicon (1963)
Plumbicon is a registered trademark of
Philips
Koninklijke Philips N.V. (), commonly shortened to Philips, is a Dutch multinational conglomerate corporation that was founded in Eindhoven in 1891. Since 1997, it has been mostly headquartered in Amsterdam, though the Benelux headquarters i ...
from 1963, for its
lead(II) oxide
Lead(II) oxide, also called lead monoxide, is the inorganic compound with the molecular formula Pb O. PbO occurs in two polymorphs: litharge having a tetragonal crystal structure, and massicot having an orthorhombic crystal structure. Modern ap ...
(PbO) target vidicons. Used frequently in broadcast camera applications, these tubes have low output, but a high
signal-to-noise ratio. They have excellent resolution compared to image orthicons, but lack the artificially sharp edges of IO tubes, which cause some of the viewing audience to perceive them as softer. CBS Labs invented the first outboard edge enhancement circuits to sharpen the edges of Plumbicon generated images.
Philips received the 1966
Technology & Engineering Emmy Award
The Technology and Engineering Emmy Awards, or Technology and Engineering Emmys, are one of two sets of Emmy Awards that are presented for outstanding achievement in engineering development in the television industry. The Technology and Enginee ...
for the Plumbicon.
![Plumbicon](https://upload.wikimedia.org/wikipedia/commons/c/ce/Plumbicon.jpg)
Compared to Saticons, Plumbicons have much higher resistance to burn-in, and comet and trailing artifacts from bright lights in the shot. Saticons though, usually have slightly higher resolution. After 1980, and the introduction of the diode-gun Plumbicon tube, the resolution of both types was so high, compared to the maximum limits of the broadcasting standard, that the Saticon's resolution advantage became moot. While broadcast cameras migrated to solid-state charge-coupled devices, Plumbicon tubes remained a staple imaging device in the medical field.
High resolution Plumbicons were made for the
HD-MAC
HD-MAC (High Definition Multiplexed Analogue Components) was a broadcast television standard proposed by the European Commission in 1986, as part of Eureka 95 project. It belongs to the MAC - Multiplexed Analogue Components standard family. It is ...
standard.
Until 2016, Narragansett Imaging was the last company making Plumbicons, using factories Philips built in
Rhode Island, USA. While still a part of Philips, the company purchased EEV's (
English Electric Valve
Teledyne e2v (previously known as e2v) is a manufacturer with its headquarters in England, that designs, develops and manufactures systems and components in healthcare, life sciences, space, transportation, defence and security and industrial mar ...
) lead oxide camera tube business, and gained a monopoly in lead-oxide tube production.
Saticon (1973)
Saticon is a registered trademark of
Hitachi from 1973, also produced by
Thomson and
Sony
, commonly stylized as SONY, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan. As a major technology company, it operates as one of the world's largest manufacturers of consumer and professiona ...
. It was developed in a joint effort by Hitachi and
NHK Science & Technology Research Laboratories
NHK Science & Technology Research Laboratories (STRL, ja, NHK放送技術研究所, NHK Hōsō Gijutsu Kenkyūjo), headquartered in Setagaya, Tokyo, Japan, is responsible for technical research at NHK, Japan's public broadcaster.
Work done by t ...
(
NHK
, also known as NHK, is a Japanese public broadcaster. NHK, which has always been known by this romanized initialism in Japanese, is a statutory corporation funded by viewers' payments of a television license fee.
NHK operates two terrestr ...
is The Japan Broadcasting Corporation). Its surface consists of selenium with trace amounts of arsenic and tellurium added (SeAsTe) to make the signal more stable. SAT in the name is derived from (SeAsTe).
Saticon tubes have an average light sensitivity equivalent to that of 64
ASA film
ASA Filmudlejning is a noted Danish film studio founded in 1936 and based in Hellerup, Copenhagen. It produced approximately 90 films between 1936 and 1988 although the bulk of its production was in the 1940s and 1950s. During this period, amo ...
.
A high-gain avalanche rushing amorphous photoconductor (HARP) can be used to increase light sensitivity to up to 10 times that of conventional saticons. Saticons were made for the
Sony HDVS
Sony HDVS is a range of high-definition video equipment developed in the 1980s to support an early analog high-definition television system (used in multiple sub-Nyquist sampling encoding (MUSE) broadcasts) thought to be the broadcast television ...
system, used to produce early
analog high-definition television using
Multiple sub-Nyquist sampling encoding.
Pasecon (1972)
Originally developed by
Toshiba
, commonly known as Toshiba and stylized as TOSHIBA, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan. Its diversified products and services include power, industrial and social infrastructure systems, ...
in 1972 as chalnicon, Pasecon is a registered trademark of Heimann GmbH from 1977. Its surface consists of
cadmium selenide trioxide (CdSeO
3). Due to its wide
spectral response, it is labelled as ''panchromatic selenium vidicon'', hence the acronym 'pasecon'.
Newvicon (1973)
Newvicon is a registered trademark of
Matsushita from 1973. The Newvicon tubes were characterized by high light sensitivity. Its surface consists of a combination of
zinc selenide
Zinc selenide (ZnSe) is a light-yellow, solid compound comprising zinc (Zn) and selenium (Se). It is an intrinsic semiconductor with a band gap of about 2.70 eV at . ZnSe rarely occurs in nature, and is found in the mineral that was named af ...
(ZnSe) and
zinc cadmium Telluride (ZnCdTe).
Trinicon (1971)
Trinicon is a registered trademark of
Sony
, commonly stylized as SONY, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan. As a major technology company, it operates as one of the world's largest manufacturers of consumer and professiona ...
from 1971. It uses a vertically striped RGB color filter over the faceplate of an otherwise standard vidicon imaging tube to segment the scan into corresponding red, green and blue segments. Only one tube was used in the camera, instead of a tube for each color, as was standard for color cameras used in television broadcasting. It is used mostly in low-end consumer cameras, such as the HVC-2200 and HVC-2400 models, though Sony also used it in some moderate cost professional cameras in the 1980s, such as the DXC-1800 and BVP-1 models.
["Sony DXC-1600"](_blank)
LabGuysWorld.com.
Although the idea of using color stripe filters over the target was not new, the Trinicon was the only tube to use the primary RGB colors. This necessitated an additional electrode buried in the target to detect where the scanning electron beam was relative to the stripe filter. Previous color stripe systems had used colors where the color circuitry was able to separate the colors purely from the relative amplitudes of the signals. As a result, the Trinicon featured a larger dynamic range of operation.
Sony later combined the Saticon tube with the Trinicon's RGB color filter, providing low-light sensitivity and superior color. This type of tube was known as the SMF Trinicon tube, or Saticon Mixed Field. SMF Trinicon tubes were used in the HVC-2800 and HVC-2500 consumer cameras, as well as the first
Betamovie
Betamovie is the brand name for a range of consumer grade camcorders developed by Sony for the Betamax format. By "camcorder" is understood a single unit comprising a video camera and a video recorder.
Betamovie records analog video on a standard ...
camcorders.
Light biasing
All the vidicon type tubes except the vidicon itself were able to use a light biasing technique to improve the sensitivity and contrast. The photosensitive target in these tubes suffered from the limitation that the light level had to rise to a particular level before any video output resulted. Light biasing was a method whereby the photosensitive target was illuminated from a light source just enough that no appreciable output was obtained, but such that a slight increase in light level from the scene was enough to provide discernible output. The light came from either an illuminator mounted around the target, or in more professional cameras from a light source on the base of the tube and guided to the target by light piping. The technique would not work with the baseline vidicon tube because it suffered from the limitation that as the target was fundamentally an insulator, the constant low light level built up a charge which would manifest itself as a form of
fogging. The other types had semiconducting targets which did not have this problem.
Color cameras
Early color cameras used the obvious technique of using separate red, green and blue image tubes in conjunction with a
color separator, a technique still in use with
3CCD solid state cameras today. It was also possible to construct a color camera that used a single image tube. One technique has already been described (Trinicon above). A more common technique and a simpler one from the tube construction standpoint was to overlay the photosensitive target with a color striped filter having a fine pattern of vertical stripes of green, cyan and clear filters (i.e. green; green and blue; and green, blue and red) repeating across the target. The advantage of this arrangement was that for virtually every color, the video level of the green component was always less than the cyan, and similarly the cyan was always less than the white. Thus the contributing images could be separated without any reference electrodes in the tube. If the three levels were the same, then that part of the scene was green. This method suffered from the disadvantage that the light levels under the three filters were almost certain to be different, with the green filter passing not more than one third of the available light.
Variations on this scheme exist, the principal one being to use two filters with color stripes overlaid such that the colors form vertically oriented lozenge shapes overlaying the target. The method of extracting the color is similar however.
Field-sequential color system
During the 1930s and 1940s,
field-sequential color system
A field-sequential color system (FSC) is a color television system in which the primary color information is transmitted in successive images and which relies on the human vision system to fuse the successive images into a color picture. One field ...
s were developed which used synchronized motor-driven color-filter disks at the camera's image tube and at the television receiver. Each disk consisted of red, blue, and green transparent color filters. In the camera, the disk was in the optical path, and in the receiver, it was in front of the CRT. Disk rotation was synchronized with vertical scanning so that each vertical scan in sequence was for a different primary color. This method allowed regular black-and-white image tubes and CRTs to generate and display color images. A field-sequential system developed by
Peter Goldmark for
CBS
CBS Broadcasting Inc., commonly shortened to CBS, the abbreviation of its former legal name Columbia Broadcasting System, is an American commercial broadcast television and radio network serving as the flagship property of the CBS Entertainm ...
was demonstrated to the press on September 4, 1940, and was first shown to the general public on January 12, 1950.
Guillermo González Camarena
Guillermo González Camarena (17 February 1917 – 18 April 1965) was a Mexican electrical engineer who was the inventor of a color-wheel type of color television.
Early life
González Camarena was born in Guadalajara, Mexico. He was the younge ...
independently developed a field-sequential color disk system in Mexico in the early 1940s, for which he requested a patent in Mexico on August 19 of 1940 and in the US in 1941.
[
] Gonzalez Camarena produced his color television system in his laboratory Gon-Cam for the Mexican market and exported it to the Columbia College of Chicago, who regarded it as the best system in the world.
[
][
]
Magnetic focusing in typical camera tubes
The phenomenon known as ''magnetic focusing'' was discovered by A. A. Campbell-Swinton in 1896,
he found that a longitudinal magnetic field generated by an axial coil can focus an electron beam.
[
] This phenomenon was immediately corroborated by
J. A. Fleming, and Hans Busch gave a complete mathematical interpretation in 1926.
[
]
Diagrams in this article show that the focus coil surrounds the camera tube; it is much longer than the focus coils for earlier TV CRTs. Camera-tube focus coils, by themselves, have essentially parallel lines of force, very different from the localized semi-
toroid
In mathematics, a toroid is a surface of revolution with a hole in the middle. The axis of revolution passes through the hole and so does not intersect the surface. For example, when a rectangle is rotated around an axis parallel to one of its ...
al magnetic field geometry inside a TV receiver CRT focus coil. The latter is essentially a
magnetic lens
thumb
thumb
A subtype of a magnetic lens ( quadrupole magnet) in the Maier-Leibnitz laboratory, Munich
A magnetic lens is a device for the focusing or deflection of moving charged particles, such as electrons or ions, by use of the magnetic ...
; it focuses the "crossover" (between the CRT's cathode and G1 electrode, where the electrons pinch together and diverge again) onto the screen.
The electron optics of camera tubes differ considerably. Electrons inside these long focus coils take
helical
Helical may refer to:
* Helix, the mathematical concept for the shape
* Helical engine, a proposed spacecraft propulsion drive
* Helical spring, a coilspring
* Helical plc, a British property company, once a maker of steel bar stock
* Helicoil
A t ...
paths as they travel along the length of the tube. The center (think local axis) of one of those helices is like a line of force of the magnetic field. While the electrons are traveling, the helices essentially don't matter. Assuming that they start from a point, the electrons will focus to a point again at a distance determined by the strength of the field. Focusing a tube with this kind of coil is simply a matter of trimming the coil's current. In effect, the electrons travel along the lines of force, although helically, in detail.
These focus coils are essentially as long as the tubes themselves, and surround the deflection yoke (coils). Deflection fields bend the lines of force (with negligible defocusing), and the electrons follow the lines of force.
In a conventional magnetically deflected CRT, such as in a TV receiver or computer monitor, basically the vertical deflection coils are equivalent to coils wound around an horizontal axis. That axis is perpendicular to the neck of the tube; lines of force are basically horizontal. (In detail, coils in a deflection yoke extend some distance beyond the neck of the tube, and lie close to the flare of the bulb; they have a truly distinctive appearance.)
In a magnetically focused camera tube (there are electrostatically focused vidicons), the vertical deflection coils are above and below the tube, instead of being on both sides of it. One might say that this sort of deflection starts to create S-bends in the lines of force, but doesn't become anywhere near to that extreme.
Size
The size of video camera tubes is simply the overall outside diameter of the glass envelope. This differs from the size of the sensitive area of the target which is typically two thirds of the size of the overall diameter. Tube sizes are always expressed in inches for historical reasons. A one-inch camera tube has a sensitive area of approximately two thirds of an inch on the diagonal or about 16 mm.
Although the video camera tube is now
technologically obsolete
Obsolescence is the state of being which occurs when an object, service, or practice is no longer maintained or required even though it may still be in good working order. It usually happens when something that is more efficient or less risky r ...
, the size of
solid-state
Solid state, or solid matter, is one of the four fundamental states of matter.
Solid state may also refer to:
Electronics
* Solid-state electronics, circuits built of solid materials
* Solid state ionics, study of ionic conductors and their use ...
image sensors is still expressed as the equivalent size of a camera tube. For this purpose a new term was coined and it is known as the
optical format Optical format is a hypothetical measurement approximately 50% larger than the true diagonal size of a solid-state photo sensor. The use of the optical format means that a lens used with a particular size sensor will have approximately the same ang ...
. The optical format is approximately the true diagonal of the sensor multiplied by 3/2. The result is expressed in inches and is usually (though not always) rounded to a convenient fraction - hence the approximation. For instance, a has a diagonal of and therefore an optical format of 8.0*3/2=, which is rounded to the convenient imperial fraction of . The parameter is also the source of the "Four Thirds" in the
Four Thirds system
The Four Thirds System is a standard created by Olympus and Eastman Kodak for digital single-lens reflex camera (DSLR) and mirrorless camera design and development.
The system provides a standard that, with digital cameras and lenses availabl ...
and its
Micro Four Thirds extension—the imaging area of the sensor in these cameras is approximately that of a video-camera tube at approximately .
Although the optical format size bears no relationship to any physical parameter of the sensor, its use means that a lens that would have been used with (say) a four thirds inch camera tube will give roughly the same angle of view when used with a solid-state sensor with an optical format of four thirds of an inch.
Late use and decline
The lifespan of videotube technology reached as far as the 90s, when high definition, 1035-line videotubes were used in the early
MUSE
In ancient Greek religion and mythology, the Muses ( grc, Μοῦσαι, Moûsai, el, Μούσες, Múses) are the inspirational goddesses of literature, science, and the arts. They were considered the source of the knowledge embodied in the ...
HD broadcasting system. While CCDs were tested for this application, as of 1993 broadcasters still found them inadequate due to issues achieving the necessary high resolution without compromising image quality with undesirable side-effects.
Modern
charge-coupled device
A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...
(CCD) and
CMOS-based sensors offer many advantages over their tube counterparts. These include a lack of image lag, high overall picture quality, high light sensitivity and dynamic range, a better
signal-to-noise ratio and significantly higher reliability and ruggedness. Other advantages include the elimination of the respective high and low-voltage power supplies required for the electron beam and
heater filament, elimination of the drive circuitry for the focusing coils, no warm-up time and a significantly lower overall power consumption. Despite these advantages, acceptance and incorporation of solid-state sensors into television and video cameras was not immediate. Early sensors were of lower resolution and performance than picture tubes, and were initially relegated to consumer-grade video recording equipment.
Also, video tubes had progressed to a high standard of quality and were standard issue equipment to networks and production entities. Those entities had a substantial investment in not only tube cameras, but also in the ancillary equipment needed to correctly process tube-derived video. A switch-over to
solid-state
Solid state, or solid matter, is one of the four fundamental states of matter.
Solid state may also refer to:
Electronics
* Solid-state electronics, circuits built of solid materials
* Solid state ionics, study of ionic conductors and their use ...
image sensors rendered much of that equipment (and the investments behind it) obsolete and required new equipment optimized to work well with solid-state sensors, just as the old equipment was optimized for tube-sourced video.
See also
*
Monoscope
*
Professional video camera
A professional video camera (often called a television camera even though its use has spread beyond television) is a high-end device for creating electronic moving images (as opposed to a movie camera, that earlier recorded the images on film). ...
References
External links
Orthicon: Brief history, description and diagram.The German TV museum with a lot of knowledge(in German)
(in German)
{{Electronic components
History of television
Television technology
Vacuum tubes