Plasma display

Early development

Kálmán Tihanyi, a Hungarian engineer, described a proposed flat-panel plasma display system in a 1936 paper.^[7]

The first practical plasma video display was co-invented in 1964 at the University of Illinois at Urbana–Champaign by Donald Bitzer, H. Gene Slottow, and graduate student Robert Willson for the PLATO computer system.^[8][9] The goal was to create a display that had inherent memory to reduce the cost of the terminals.^[10] The original neon orange monochrome Digivue display panels built by glass producer Owens-Illinois were very popular in the early 1970s because they were rugged and needed neither memory nor circuitry to refresh the images.^[11] A long period of sales decline occurred in the late 1970s because semiconductor memory made CRT displays cheaper than the $2500 USD 512 × 512 PLATO plasma displays.^[12] Nevertheless, the plasma displays' relatively large screen size and 1 inch (25.4 mm) thickness made them suitable for high-profile placement in lobbies and stock exchanges.

Burroughs Corporation, a maker of adding machines and computers, developed the Panaplex display in the early 1970s. The Panaplex display, generically referred to as a gas-discharge or gas-plasma display,^[13] uses the same technology as later plasma video displays, but began life as a seven-segment display for use in adding machines. They became popular for their bright orange luminous look and found nearly ubiquitous use throughout the late 1970s and into the 1990s in cash registers, calculators, pinball machines, aircraft avionics such as radios, navigational instruments, and stormscopes; test equipment such as frequency counters and multimeters; and generally anything that previously used nixie tube or numitron displays with a high digit-count. These displays were eventually replaced by LEDs because of their low current-draw and module-flexibility, but are still found in some applications where their high brightness is desired, such as pinball machines and avionics.

1980s

In 1983, IBM introduced a 19-inch (48 cm) orange-on-black monochrome display (Model 3290 Information Panel) which was able to show up to four simultaneous IBM 3270 terminal sessions.^[14] By the end of the decade, orange monochrome plasma displays were used in a number of high-end AC-powered portable computers, such as the Ericsson Portable PC (the first use of such a display in 1985),^[15] the Compaq Portable 386 (1987) and the IBM P75 (1990). Plasma displays had a better contrast ratio, viewability angle, and less motion blur than the LCDs that were available at the time, and were used until the introduction of active-matrix color LCD displays in 1992.^[14]

Due to heavy competition from monochrome LCDs used in laptops and the high costs of plasma display technology, in 1987 IBM planned to shut down its factory in Kingston, New York, the largest plasma plant in the world, in favor of manufacturing mainframe computers, which would have left development to Japanese companies.^[16] Dr. Larry F. Weber, a University of Illinois ECE PhD (in plasma display research) and staff scientist working at CERL (home of the PLATO System), co-founded Plasmaco with Stephen Globus and IBM plant manager James Kehoe, and bought the plant from IBM for US$50,000. Weber stayed in Urbana as CTO until 1990, then moved to upstate New York to work at Plasmaco.

1990s

In 1992, Fujitsu introduced the world's first 21-inch (53 cm) full-color display. It was based on technology created at the University of Illinois at Urbana–Champaign and NHK Science & Technology Research Laboratories.

In 1994, Weber demonstrated a color plasma display at an industry convention in San Jose. Panasonic Corporation began a joint development project with Plasmaco, which led in 1996 to the purchase of Plasmaco, its color AC technology, and its American factory for US$26 million.

In 1995, Fujitsu introduced the first 42-inch (107 cm) plasma display panel;^[17][18] it had 852×480 resolution and was progressively scanned.^[19] Two years later, Philips introduced at CES and CeBIT the first large commercially available flat-panel TV, using the Fujitsu panels. Philips had plans to sell it for 70,000 french francs.^[20][21][22] It was released as the Philips 42PW9962. It was available at four Sears locations in the US for $14,999,^[23] including in-home installation. Pioneer and Fujitsu^[24] also began selling plasma televisions that year, and other manufacturers followed. By the year 2000 prices had dropped to $10,000.

2000s

In the year 2000, the first 60-inch (152-cm) plasma display was developed by Plasmaco. Panasonic was also reported to have developed a process to make plasma displays using ordinary window glass instead of the much more expensive "high strain point" glass.^[25] High strain point glass is made similarly to conventional float glass, but it is more heat resistant, deforming at higher temperatures. High strain point glass is normally necessary because plasma displays have to be baked during manufacture to dry the rare-earth phosphors after they are applied to the display. However, high strain point glass may be less scratch resistant.^{[26][27][28][29]}

Until the early 2000s, plasma displays were the most popular choice for HDTV flat-panel display as they had many benefits over LCDs. Beyond plasma's deeper blacks, increased contrast, faster response time, greater color spectrum, and wider viewing angle; they were also much bigger than LCDs, and it was believed that LCDs were suited only to smaller sized televisions. Plasma had overtaken rear-projection systems in 2005.^[30]

However, improvements in LCD fabrication narrowed the technological gap. The increased size, lower weight, falling prices, and often lower electrical power consumption of LCDs made them competitive with plasma television sets. In 2006, LCD prices started to fall rapidly and their screen sizes increased, although plasma televisions maintained a slight edge in picture quality and a price advantage for sets at the critical 42" size and larger. By late 2006, several vendors were offering 42" LCDs, albeit at a premium price, encroaching upon plasma's only stronghold. More decisively, LCDs offered higher resolutions and true 1080p support, while plasmas were stuck at 720p, which made up for the price difference.^[31]

In late 2006, analysts noted that LCDs had overtaken plasmas, particularly in the 40-inch (100 cm) and above segment where plasma had previously gained market share.^[32] Another industry trend was the consolidation of plasma display manufacturers, with around 50 brands available but only five manufacturers. In the first quarter of 2008, a comparison of worldwide TV sales broke down to 22.1 million for direct-view CRT, 21.1 million for LCD, 2.8 million for plasma, and 0.1 million for rear projection.^[33]

When the sales figures for the 2007 Christmas season were finally tallied, analysts were surprised to find that not only had LCD outsold plasma, but CRTs as well, during the same period.^[34] This development drove competing large-screen systems from the market almost overnight. The February 2009 announcement that Pioneer Electronics was ending production of plasma screens was widely considered the tipping point in the technology's history as well.^[35]

Screen sizes have increased since the introduction of plasma displays. The largest plasma video display in the world at the 2008 Consumer Electronics Show in Las Vegas, Nevada, was a 150-inch (380 cm) unit manufactured by Matsushita Electric Industrial (Panasonic) standing 6 ft (180 cm) tall by 11 ft (340 cm) wide.^[36][37]

2010s

At the 2010 Consumer Electronics Show in Las Vegas, Panasonic introduced their 152" 2160p 3D plasma. In 2010, Panasonic shipped 19.1 million plasma TV panels.^[38]

In 2010, the shipments of plasma TVs reached 18.2 million units globally.^[39] Since that time, shipments of plasma TVs have declined substantially. This decline has been attributed to the competition from liquid crystal (LCD) televisions, whose prices have fallen more rapidly than those of the plasma TVs.^[40] In late 2013, Panasonic announced that they would stop producing plasma TVs from March 2014 onwards.^[41] In 2014, LG and Samsung discontinued plasma TV production as well,^[42][43] effectively killing the technology, probably because of lowering demand.

Contrast ratio

Contrast ratio is the difference between the brightest and darkest parts of an image, measured in discrete steps, at any given moment. Generally, the higher the contrast ratio, the more realistic the image is (though the "realism" of an image depends on many factors including color accuracy, luminance linearity, and spatial linearity). Contrast ratios for plasma displays are often advertised as high as 5,000,000:1.^[69] On the surface, this is a significant advantage of plasma over most other current display technologies, a notable exception being organic light-emitting diode. Although there are no industry-wide guidelines for reporting contrast ratio, most manufacturers follow either the ANSI standard or perform a full-on-full-off test. The ANSI standard uses a checkered test pattern whereby the darkest blacks and the lightest whites are simultaneously measured, yielding the most accurate "real-world" ratings. In contrast, a full-on-full-off test measures the ratio using a pure black screen and a pure white screen, which gives higher values but does not represent a typical viewing scenario. Some displays, using many different technologies, have some "leakage" of light, through either optical or electronic means, from lit pixels to adjacent pixels so that dark pixels that are near bright ones appear less dark than they do during a full-off display. Manufacturers can further artificially improve the reported contrast ratio by increasing the contrast and brightness settings to achieve the highest test values. However, a contrast ratio generated by this method is misleading, as content would be essentially unwatchable at such settings.^[70][71][72]

Each cell on a plasma display must be precharged before it is lit, otherwise the cell would not respond quickly enough. Precharging normally increases power consumption, so energy recovery mechanisms may be in place to avoid an increase in power consumption.^[73][74][75] This precharging means the cells cannot achieve a true black,^[76] whereas an LED backlit LCD panel can actually turn off parts of the backlight, in "spots" or "patches" (this technique, however, does not prevent the large accumulated passive light of adjacent lamps, and the reflection media, from returning values from within the panel). Some manufacturers have reduced the precharge and the associated background glow, to the point where black levels on modern plasmas are starting to become close to some high-end CRTs Sony and Mitsubishi produced ten years before the comparable plasma displays. With an LCD, black pixels are generated by a light polarization method; many panels are unable to completely block the underlying backlight. More recent LCD panels using LED illumination can automatically reduce the backlighting on darker scenes, though this method cannot be used in high-contrast scenes, leaving some light showing from black parts of an image with bright parts, such as (at the extreme) a solid black screen with one fine intense bright line. This is called a "halo" effect which has been minimized on newer LED-backlit LCDs with local dimming. Edgelit models cannot compete with this as the light is reflected via a light guide to distribute the light behind the panel.^[63][64][77]

Plasma displays are capable of producing deeper blacks than LCD allowing for a superior contrast ratio.^[63][64][77]

Earlier generation displays (circa 2006 and prior) had phosphors that lost luminosity over time, resulting in gradual decline of absolute image brightness. Newer models have advertised lifespans exceeding 100,000 hours (11 years), far longer than older CRTs.^[55][77]

Screen burn-in

Image burn-in occurs on CRTs and plasma panels when the same picture is displayed for long periods. This causes the phosphors to overheat, losing some of their luminosity and producing a "shadow" image that is visible with the power off. Burn-in is especially a problem on plasma panels because they run hotter than CRTs. Early plasma televisions were plagued by burn-in, making it impossible to use video games or anything else that displayed static images.

Plasma displays also exhibit another image retention issue which is sometimes confused with screen burn-in damage. In this mode, when a group of pixels are run at high brightness (when displaying white, for example) for an extended period, a charge build-up in the pixel structure occurs and a ghost image can be seen. However, unlike burn-in, this charge build-up is transient and self-corrects after the image condition that caused the effect has been removed and a long enough period has passed (with the display either off or on).

Plasma manufacturers have tried various ways of reducing burn-in such as using gray pillarboxes, pixel orbiters and image washing routines. Recent models have a pixel orbiter that moves the entire picture slower than is noticeable to the human eye, which reduces the effect of burn-in but does not prevent it.^[78] None to date have eliminated the problem and all plasma manufacturers continue to exclude burn-in from their warranties.^[77][79]

Screen resolution

Fixed-pixel displays such as plasma TVs scale the video image of each incoming signal to the native resolution of the display panel. The most common native resolutions for plasma display panels are 852×480 (EDTV), 1,366×768 and 1920×1080 (HDTV). As a result, picture quality varies depending on the performance of the video scaling processor and the upscaling and downscaling algorithms used by each display manufacturer.^[80][81]

Early plasma televisions were enhanced-definition (ED) with a native resolution of 840×480 (discontinued) or 852×480 and down-scaled their incoming high-definition video signals to match their native display resolutions.^[82]

The following ED resolutions were common prior to the introduction of HD displays, but have long been phased out in favor of HD displays, as well as because the overall pixel count in ED displays is lower than the pixel count on SD PAL displays (852×480 vs 720×576, respectively).

• 840×480p
• 852×480p

Early high-definition (HD) plasma displays had a resolution of 1024x1024 and were alternate lighting of surfaces (ALiS) panels made by Fujitsu and Hitachi.^[83][84] These were interlaced displays, with non-square pixels.^[85]

Later HDTV plasma televisions usually have a resolution of 1,024×768 found on many 42-inch (107-cm) plasma screens, 1280×768 and 1,366×768 found on 50 in, 60 in, and 65 in plasma screens, or 1920×1080 found on plasma screen sizes from 42 to 103 inches (107-262 cm). These displays are usually progressive displays, with non-square pixels, and will up-scale and de-interlace their incoming standard-definition signals to match their native display resolutions. 1024×768 resolution requires that 720p content be downscaled in one direction and upscaled in the other.^[86][87]