Trinitron
Trinitron was Sony's brand name for its line of aperture-grille-based CRTs used in television sets and computer monitors. It was one of the first television systems to enter the market since the 1950s. The first color Trinitron system was released in October 1968. 100 million Trinitron systems had been sold by 1994.
At its peak 20 million Trinitron tubes were made annually. Patent protection on the basic Trinitron design ran out in 1996, and it quickly faced a number of competitors at much lower prices. Sony ended production from Japanese plants in 2004, and stopped selling them in the United States and Canada in 2006. Sony continued to sell Trinitrons in China, India, and regions of South America using tubes delivered from their Singapore plant until it ended production in March 2008. By that time a total of 280 million units were built during when Trinitron production concluded.
The name Trinitron was derived from trinity, meaning the union of three, and tron from electron tube, after the way that the Trinitron combined the three separate electron guns of other CRT designs into one.
Image:Trinitron-bars-detail-enlarged.jpg|right|thumb|Close-up of phosphor bars on a 14" Sony Trinitron television
History
Color television
Color television had been demonstrable since the 1920s starting with John Logie Baird's system. In the late 1940s it was perfected by both CBS and RCA. At the time, a number of systems were being proposed that used separate red, green and blue signals, broadcast in succession. Most systems broadcast entire frames in sequence, with a colored filter 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 Communications Commission selected a sequential-frame 144 frame/s standard from CBS as their color broadcast in 1950.
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. 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 the compatible color encoding scheme originally developed by Georges Valensi in 1938, 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 proper signal on each of these tiny spots was beyond the capability of electron guns of the era, and RCA's early experiments used three-tube projectors, or mirror-based systems known as "Triniscope".
Shadow masks
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 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.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. 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.
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 supply and demand problem. In the United States in 1960, only 1 color set was sold for every 50 sets sold in total.
Chromatron
Sony had entered the television market in 1960 with the black and white TV8-301, the first non-projection type all-transistor television. 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. 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.In 1961, a Sony delegation was visiting the IEEE trade show in New York City, including Ibuka, Akio Morita 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 tube, which used a single electron gun and a vertical grille of electrically charged 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.
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".
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.
When sets were finally made available in late 1964, they were put on the market at a competitive 198,000 yen, 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.
Trinitron
In the autumn of 1966, Ibuka 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 phosphors 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.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 cathodes. This would be more difficult to build, but be lower cost in the long run. Miyaoka built a prototype and was astonished by how well it worked, although it had focusing problems.
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. The following Monday, Ibuka announced that Sony would be developing a new color television tube, based on Miyaoka's prototype. 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 manual adjustments after manufacturing.
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. 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 several fine tungsten wires across the grille horizontally to keep the vertical wires of the grille in place.
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. 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 very similar, or the same.