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[[Image:Trinitron-bars-detail-enlarged.jpg|right|thumb|250px|Primo piano dei fosfori di un 14" Sony Trinitron.]]
==Storia==
[[File:Trinitron.jpg|thumb|right|250px|Un modello Trinitron anni '70]]
{{vedi anche|Storia della televisione}}
{{main|Televisione a colori}}
{{main|===[[Shadow mask }}]]===▼Color television had been studied even before commercial broadcasting became common, but it was only in the late 1940s that the problem was seriously considered. At the time, a number of systems were being proposed that used separate red, green and blue signals (RGB), broadcast in succession. Most systems broadcast entire frames in sequence, with a colored filter (or "[[Color gel|gel]]") that rotated in front of an otherwise conventional black and white television tube. Because they broadcast separate signals for the different colors, all of these systems were incompatible with existing black and white sets. Another problem was that the mechanical filter made them flicker unless very high refresh rates were used. In spite of these problems, the United States Federal Communication Commission selected a sequential-frame 144 frame/s standard from [[CBS]] as their color broadcast in 1950.<ref>Ed Reitan, [http://novia.net/~ereitan/Color_Sys_CBS.html "CBS Field Sequential Color System"], 24 August 1997</ref>
{{vedi anche|Shadow mask}}
[[RCA]] worked along different lines entirely, using the luminance-chrominance system. This system did not directly encode or transmit the RGB signals; instead it combined these colors into one overall brightness figure, the "[[luminance]]". Luminance closely matched the black and white signal of existing broadcasts, allowing it to be displayed on existing televisions. This was a major advantage over the mechanical systems being proposed by other groups. Color information was then separately encoded and folded into the signal as a high-frequency modification to produce a [[composite video]] signal – on a black and white television this extra information would be seen as a slight randomization of the image intensity, but the limited resolution of existing sets made this invisible in practice. On color sets the signal would be extracted, decoded back into RGB, and displayed.
RCA sviluppò uno schermo a colori introducendo la [[shadow mask]], un sottile foglio di materiale metallico con piccoli fori creati mediante [[fotolitografia]] posto dietro la superficie frontale del CRT. Tre cannoni, messi a triangolo, colpivano solo una porzione dedicata dello schermo con depositato i fosfori con angolazioni diverse.
Although RCA's system had enormous benefits, it had not been successfully developed because it was difficult to produce the display tubes. Black and white TVs used a continuous signal and the tube could be coated with an even deposit of phosphor. With Valensi's system, the color was changing continually along the line, which was far too fast for any sort of mechanical filter to follow. Instead, the phosphor had to be broken down into a discrete pattern of colored spots. Focusing the right signal on each of these tiny spots was beyond the capability of [[electron gun]]s of the era, and RCA's early experiments used three-tube projectors, or mirror-based systems known as "[[Triniscope]]".<ref name=rca>Ed Reitan, [http://novia.net/~ereitan/Color_Sys_RCA.html "RCA Dot Sequential Color System"], 28 August 1997</ref>
Lo svantaggio era che il 25% dell'energia degli alettroni sparati dai cannoni era assorbita dalla maschera. La superiorità del sistema inventato dalla RCA, rispetto a quello della CBS, lo fece diventare standard nel 1953<ref>Jack Gould, "Television in Review: NBC Color", ''The New York Times'', 4 January 1954</ref>.
Negli Stati Uniti nel 1960, solo uno era TV color su 50 televisori venduti<ref name=s42>''Sony'', pg. 42</ref>.
===Shadow mask[[Chromatron]]===
Sony entrò nel mercato televisori nel 1960 con il modello in b/n [[TV8-301]], il primo a [[transitor]] e il primo portatile<ref>Edward Lucie-Smith, "A History of Industrial Design", Van Nostrand Reinhold, 1983, pg. 208</ref>. Nel 1961 i rivenditori chiesero alla Sony quando una TV a colori sarebbe stata disponibile, incitando la ricerca e sviluppo presso l'engineering. [[Masaru Ibuka]], presidente e cofondatore della Sony, rifiutò subito di basare i propri prodotti con il [[shadow mask]], tecnicamente deficiente. Volle un sistema nuovo, originale.<ref>''Sony'', pg. 43</ref>
Nel 1961 una delegazione Sony visitò la fiera della [[IEEE]] a [[New York City]], Ibuka, [[Akio Morita]] (cofondatore Sony) e [[Nobutoshi Kihara]], creatore del [[CV-2000]] ''home video tape recorder''. Videro il sistema [[Chromatron]], migliore di quello della RCA.<ref name=s44>''Sony'', pg. 44</ref>
Morita contrattò con la [[Paramount Pictures]], che finanziò lo sviluppo della Chromatic Labs', acquisendo il progetto. Nel 1963 [[Senri Miyaoka]] si recò a [[Manhattan]] per trasferire la tecnologia alla Sony dalla Chromatic Labs. Rimase impresso dello squallore dei laboratori senza finestre.<ref name=s44/> Nel settembre 1964, un prototipo di 17" fu costruito in Giappone, ma la produzione di massa non ebbe successo causa problemi tecnici irrisolvibili.<ref name=s44/>
RCA eventually solved the problem of displaying the color images with their introduction of the [[shadow mask]]. The shadow mask consists of a thin sheet of steel with tiny holes [[Photolithography|photo etched]] into it, placed just behind the front surface of the picture tube. Three guns, arranged in a triangle, were all aimed at the holes. Stray electrons at the edge of the beam were cut off by the mask, creating a sharply focused spot that was small enough to hit a single colored phosphor on the screen. Since each of the guns was aimed at the hole from a slightly different angle, the spots of phosphor on the tube could be separated slightly to prevent overlap.
Il costo del Chromatron era troppo elevato per produrlo (400.000 yen), rispetto al costo di un singolo TV sul mercato (198.000 yen - $550). [[Panasonic]] e [[Toshiba]] furono pronti a commercializzare TV basati sul sistema RCA. Nel 1966 il Chromatron fu un fallimento finanziario-commerciale.<ref>''Sony'', pg. 45</ref>
The disadvantage of this approach was that for any given amount of gun power, the shadow mask filtered out the majority of the energy. To ensure there was no overlap of the beam on the screen, the dots had to be separated and covered perhaps 25% of its surface. This led to very dim images, requiring much greater electron beam power in order to provide a useful picture. Moreover, the system was highly dependent on the relative angles of the beams between the three guns, which required constant adjustment by the user to ensure the guns hit the correct colors. In spite of this, the technical superiority of the RCA system was overwhelming compared to the CBS system, and was selected as the new NTSC standard in 1953. The first broadcast using the new standard occurred on New Year's Day in 1954, when NBC broadcast the [[Tournament of Roses Parade]].<ref>Jack Gould, "Television in Review: NBC Color", ''The New York Times'', 4 January 1954</ref>
In spite of this early start, only a few years after regularly scheduled television broadcasting had begun, consumer uptake of color televisions was very slow to start. The dim images, constant adjustments and high costs had kept them in a niche of their own. Low consumer acceptance led to a lack of color programming, further reducing the demand for the sets in a [[chicken or the egg]] situation. In the United States in 1960, only 1 color set was sold for every 50 sets sold in total.<ref name=s42>''Sony'', pg. 42</ref>
===Chromatron===
Sony had entered the television market in 1960 with the black and white [[TV8-301]], the first transistorized television and the first portable design.<ref>Edward Lucie-Smith, "A History of Industrial Design", Van Nostrand Reinhold, 1983, pg. 208</ref> A combination of factors, including its small screen size, limited its sales to niche markets. Sony engineers had been studying the color market, but the situation in Japan was even worse than the U.S.; they accounted for only 300 of the 9 million sets sold that year.<ref name=s42/> But by 1961 dealers were asking the Sony sales department when a color set would be available, and the sales department put pressure on engineering in turn. [[Masaru Ibuka]], Sony's president and co-founder, steadfastly refused to develop a system based on RCA's shadow mask design, which he considered technically deficient. He insisted on developing a unique solution.<ref>''Sony'', pg. 43</ref>
In 1961 a Sony delegation was visiting the [[IEEE]] trade show in [[New York City]], including Ibuka, [[Akio Morita]] (Sony's other co-founder) and [[Nobutoshi Kihara]], who was promoting his new [[CV-2000]] home [[video tape recorder]]. This was Kihara's first trip abroad and he spent much of his time wandering the trade floor, where he came across a small booth by the small company [[Autometric]]. They were demonstrating a new type of color television based on the [[Chromatron]] system, which used a single electron gun and a mask of thin wires instead of a shadow mask. The resulting image was far brighter than anything the RCA design could produce, and lacked the convergence problems that required constant adjustments. He quickly brought Morita and Ibuka to see the design, and Morita was "sold" on the spot.<ref name=s44>''Sony'', pg. 44</ref>
Morita arranged a deal with [[Paramount Pictures]], who was paying for Chromatic Labs' development of the Chromatron, taking over the entire project. In early 1963 Senri Miyaoka was sent to Manhattan to arrange the transfer of the technology to Sony, which would lead to the closing of Chromatic Labs. He was unimpressed with the labs, describing the windowless basement as "squalor".<ref name=s44/> The American team was only too happy to point out the serious flaws in the Chromatron system, telling Miyaoka that the design was hopeless. By September 1964, a 17 inch prototype had been built in Japan, but mass-production test runs were demonstrating serious problems. Sony engineers were unable to make a version of Chromatron that could be reliably mass produced.<ref name=s44/>
When sets were finally made available in late 1964, they were put on the market at a competitive 198,000 yen ($550), but cost the company over 400,000 yen to produce. Ibuka had bet the company on Chromatron and had already set up a new factory to produce them with the hopes that the production problems would be ironed out and the line would become profitable. After several thousand sets had shipped the situation was no better, while [[Panasonic]] and [[Toshiba]] were in the process of introducing sets based on RCA licenses. By 1966 the Chromatron was breaking the company financially.<ref>''Sony'', pg. 45</ref>
===Trinitron===
Nell'autunno del 1966 Ibuka annunciò il nuovo sistema, il Trinitron. [[Susumu Yoshida]] valutò possibili licenze oltre al sistema della RCA, come quello della [[General Electric]] "[[Porta-color]]", con tre cannoni in linea.<ref name=s46>''Sony'', pg. 46</ref>
In the autumn of 1966 Ibuka finally gave in, and announced he would personally lead a search for a replacement for Chromatron. [[Susumu Yoshida]] was sent to the U.S. to look for potential licenses, and was impressed with the improvements that RCA had made in overall brightness by introducing new [[Rare earth elements|rare earth]] [[phosphor]]s on the screen. He also saw [[General Electric]]'s "Porta-color" design, using three guns in a row instead of a triangle, which allowed a greater portion of the screen to be lit. His report was cause for concern in Japan, where it seemed Sony was falling ever-farther behind the U.S. designs. They might be forced to license the shadow mask system if they wanted to remain competitive.<ref name=s46>''Sony'', pg. 46</ref>
Yoshida chiese a [[Senri Miyaoka]] se il sistema dei tre cannone in linea usato dalla GE fosse sostituibile con un singolo cannone con tre catoi; più difficile da costruire ma di minor costo. Miyaoka costruì un prototipo molto efficiente.<ref name=s46/> Ibuka annunciò che la Sony stava sviluppando un nuovo sistema basato sul prototipo di Miyaoka.<ref name=s47>''Sony'', pg. 47</ref> Nel febbraio 1967 i problemi tecnici furono risolti, magneti permanenti al posto delle bobine permettevano di non avere necessari aggiustamenti post-produzione.
Ibuka was not willing to give up entirely, and had his 30 engineers explore a wide variety of approaches to see if they could come up with their own design. At one point Yoshida asked [[Senri Miyaoka]] if the in-line gun arrangement used by GE could be replaced by a single gun with three [[cathode]]s; this would be more difficult to build, but be lower cost in the long run. Miyaoka built a prototype and was astonished how well it worked, although it had focussing problems.<ref name=s46/> Later that week, on Saturday, Miyaoka was summoned to Ibuka's office while he was attempting to leave work to attend his weekly cello practice. Yoshida had just informed Ibuka about his success, and the two asked Miyaoka if they could really develop the gun into a workable product. Miyaoka, anxious to leave, answered yes, excused himself, and left. That Monday Ibuka announced that Sony would be developing a new color television design, based on Miyaoka's prototype.<ref name=s47>''Sony'', pg. 47</ref> By February 1967 the focusing problems had been solved, and because there was a single gun, the focusing was achieved with permanent magnets instead of a coil, and required no after manufacturing manual adjustments.
[[Akio Ohgoshi]] introdusse la caratteristica dei fori rettangolari sulla shadow-mask al posto di quelli circolari. Ohgoshi propose di rimuovere la maschera completamente e depositare delle linee metalliche verticali. In fase di costruzione tali linee venivano fissate orizzontalmente con dei fili di [[tungsteno]] che le rendevano solidali allo schermo.<ref name=s47/>
During development, Sony engineer Akio Ohgoshi introduced another modification. GE's system improved on the RCA shadow mask by replacing the small round holes with slightly larger rectangles. Since the guns were in-line, their electrons would land onto three rectangular patches instead of three smaller spots, about doubling the lit area. Ohgoshi proposed removing the mask entirely and replacing it with a series of vertical slots instead, lighting the entire screen. Although this would require the guns to be very carefully aligned with the phosphors on the tube in order to ensure they hit the right colors; with Miyaoka's new tube this appeared possible.<ref name=s47/> In practice this proved easy to build but difficult to place in the tube – the fine wires were mechanically weak and tended to move when the tubes were bumped, resulting in shifting colors on the screen. This problem was solved by running fine tungsten wires across the grille horizontally to keep them in place.
La combinazione dei cannoni elettronici tre-in-uno e l'adozione della [[aperture grille]] ebbe successo. Ufficialmente introdotto da Ikuba nell'aprile del 1968, il primo 12 inch Trinitron ebbe una qualità video unica rispetto alla concorrenza. Il CRT era quasi piatto verticalmente, un effetto collaterale delle linee verticali dell'[[aperture grille]]. Interamente a [[stato solido]], fu molto compatto e piacevole nel design.
The combination of three-in-one electron gun and the replacement of the shadow mask with the [[aperture grille]] resulted in a unique and easily patentable product. Officially introduced by Ikuba in April 1968, the original 12 inch Trinitron had a display quality that easily surpassed any commercial set in terms of brightness, color fidelity, and simplicity of operation. The tube was also nearly flat vertically, a side-effect of the vertical wires in the aperture grille, which gave it a unique and appealing look. It was also all [[Solid state (electronics)|solid state]], with the exception of the picture tube itself, which allowed it to be much more compact and cool running than designs like GE's Porta-color. (At least some Trinitron faceplates were actually toroidal segments, with a vertical-plane radius of curvature much larger than that for the horizontal plane. Observing bright reflections on the surface confirms this.)
Ikuba ended the press conference by claiming that 10,000 sets would be available by October, well beyond what engineering had told him was possible. Ikuba cajoled Yoshida to take over the effort of bringing the sets into production, and although Yoshida was furious at being put in charge of a task he felt was impossible, he finally accepted the assignment and successfully met the production goal.<ref name=s48>''Sony'', pg. 48</ref> The KV-1210 was introduced in limited numbers in Japan in October as promised, and in the U.S. as the KV-1210U the following year.
In spite of Trinitron and Chromatron having no technology in common, the shared single electron gun has led to many erroneous claims that the two are similar, or the same.<ref>[http://www.scienceandsociety.co.uk/results.asp?image=10463866&wwwflag=2&imagepos=1 "Sony Trinitron color television receiver, c 1970"] is a common publication claiming that Trinitron and Chromatron are the same. "The History of Television, 1942 to 2000" by Albert Abramson makes the same claim on page 117.</ref> ▼
▲In spite of Trinitron ande [[Chromatron ]] havingnon noebbero technologyniente in common,comune these sharednon singlel'unico electroncannone gun has led to many erroneous claims that the two are similar, or the sameelettronico.<ref>[http://www.scienceandsociety.co.uk/results.asp?image=10463866&wwwflag=2&imagepos=1 "Sony Trinitron color television receiver, c 1970"] isè auna commonpubblicità publicationche claimingsostiene thatche Trinitron ande Chromatron aresono la thestessa samecosa. "The History of Television, 1942 to 2000" by Albert Abramson makessostiene thelo samestesso claim ona pagepagina 117.</ref>
Despite the statement above claiming that there were no valves inside Trinitron TV sets, for a brief period in the [[United Kingdom]] between 1969 and 1971/72, the KV-1320UB was fitted with 3AT2 valves for the [[extra high tension]] (high voltage). Later on, the KV-1320UB was redesigned internally and externally to become all solid-state. Despite containing [[vacuum tubes]], the first version of the KV-1320UB was promoted as being all solid-state. The later version of this model is identified as having no wooden outer-shell. These early color sets intended for the UK market had a PAL decoder that was different from those invented and licensed by [[Telefunken]] of [[Germany]], who invented this color system. The decoder inside the UK-sold Sony color Trinitron sets, from the KV-1300UB to the KV-1330UB had an [[NTSC]] decoder adapted for [[PAL]]. The decoder used a 64 microsecond delay line to store every other line, but instead of using the delay line to average out the phase of the current line and the "remembered" line (as with "Deluxe PAL"), it simply repeats the same line twice. Any phase errors can then be compensated for by using a Tint control on the front of the set.
Today, Sony produces only LCD televisions in their BRAVIA line, based on screens initially from [[Samsung]] and later [[Sharp Corporation|Sharp]].<ref>Shu-Ching Jean Chen, [http://www.forbes.com/2008/02/26/sony-sharp-lcd-markets-equity-cx_jc_0226markets08.html "Sony Jilts Samsung For Sharp In LCD Panel Production"], ''Forbes'', 26 February 2008</ref>
==DescriptionDescrizione==
===BasicConcetti conceptbase===
The Trinitron design incorporates two unique features: the single-gun three-cathode picture tube, and the vertically aligned [[aperture grille]].
The electrons from the cathodes are all aimed toward a single point at the back of the screen where they hit the aperture grille, a steel sheet with vertical slots cut in it. Due to the slight separation of the cathodes at the back of the tube, the three beams approach the grille at slightly different angles. When they pass through the grille they retain this angle, hitting their individual colored phosphors that are deposited in vertical stripes on the inside of the faceplate. The main purpose of the grille is to ensure that each beam strikes only the phosphor stripes for its color, much as does a shadow mask. However, unlike a shadow mask, there are essentially no obstructions along each entire phosphor stripe. (Larger CRTs have a few horizontal stabilizing wires part way between top and bottom, but in practice, they are not noticed.)
===AdvantagesVantaggi===
In comparison to early shadow mask designs, the Trinitron grille cuts off much less of the signal coming from the electron guns. RCA sets built in the 1950s cut off about 85% of the incoming signal, while the grille cuts off about 25%. Improvements to the shadow mask designs continually narrowed this difference in the two designs, and by the late 1980s the difference in performance, at least theoretically, was eliminated.
For this reason, Trinitron systems are easier to focus than shadow masks, and generally had a sharper image. This was a major selling point of the Trinitron design for much of its history. In the 1990s new computer controlled real-time feedback focusing systems eliminated this advantage, as well as leading to the introduction of "true flat" designs.
===VisibleFili Supportdi Wiressupporto visibili===
Even small changes in the alignment of the grille over the phosphors can cause the coloring to shift. Since the wires are thin, small bumps can cause the wires to shift alignment if they are not held in place. Monitors using this technology have one or more thin tungsten wires running horizontally across the grille to prevent this. Screens 15" and below have one wire located about two thirds of the way down the screen, while monitors greater than 15" have 2 wires at the one-third and two-thirds positions. These wires are less apparent or completely obscured on [[Standard-definition television|standard definition]] sets due to larger [[scan lines]] of the video being displayed. On computer monitors, where the lines are much closer together, the wires are often visible. This is a minor drawback of the Trinitron standard which is not shared by shadow mask CRTs.
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* [[Shadow mask]]
===Note===
{{reflist|2}}
===Bibliografia===
{{refbegin}}
* John Nathan, "Sony: The Private Life", Houghton Mifflin Harcourt, 2001, ISBN 0-618-12694-5
{{refend}}
==Collegamenti esterni==
* [http://www.epinions.com/cmd-review-68E6-1273DC21-3839F1FF-bd4 Sony Trinitron Explained]
{{portale|elettronica|televisione}}
[[Categoria:Sony]]
[[Categoria:Tecnologie di visualizzazione]]
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