TFT LCD
Encyclopedia
Thin film transistor liquid crystal display (TFT-LCD) is a variant of liquid crystal display
(LCD) which uses thin-film transistor
(TFT) technology to improve image quality (e.g., addressability, contrast). TFT LCD is one type of Active matrix
LCD, though all LCD-screens are based on TFT active matrix addressing. TFT LCDs are used in television set
s, computer monitors, mobile phone
s, handheld video game systems, personal digital assistant
s, navigation system
s, projector
s, etc.
Liquid crystal displays as used in calculators and devices have direct driven image elements – a voltage
can be applied across one segment without interfering with other segments of the display. This is impractical for a large display
with a large number of picture elements (pixel
s), since it would require millions of connections – top and bottom connections for each one of the three colors (red, green and blue) of every pixel. To avoid this issue, the pixels are addressed in rows and columns, reducing the connection count from millions to thousands. The column and row wires attach to transistor
switches, one for each pixel. The one-way current passing characteristic of the transistor prevents the charge applied to the pixel from draining between refreshes to the display image. Each pixel is a small capacitor
with a layer of insulating liquid crystal sandwiched between transparent conductive ITO
layers.
The circuit layout process of a TFT-LCD is very similar to that of semiconductor products. However, rather than fabricating the transistors from silicon
formed into a crystalline silicon
wafer, they are made from a thin film
of amorphous silicon
deposited on a glass
panel. The silicon layer for TFT-LCDs is typically deposited using the PECVD
process. Transistors take up only a small fraction of the area of each pixel; the rest of the silicon film is etched away to allow light to pass through.
Polycrystalline silicon
is sometimes used in displays requiring higher TFT performance. Examples include small high-resolution displays such as those found in projectors or view finders. Amorphous silicon-based TFTs are by far the most common due to their lower production cost, whereas polycrystalline silicon TFTs are more costly and difficult to produce.
The relatively inexpensive twisted nematic display is the most common consumer display type. The pixel response time on modern TN panels is sufficiently fast to avoid the shadow-trail and ghosting artifacts of earlier production. The fast response time has been emphasised in advertising TN displays, although in most cases this number does not reflect performance across the entire range of possible color transitions. More recent use of RTC (Response Time Compensation / Overdrive) technologies has allowed manufacturers to significantly reduce grey-to-grey (G2G) transitions, without significantly improving the ISO response time. Response times are now quoted in G2G figures, with 4ms and 2ms now being commonplace for TN-based models. The good response time and low cost has led to the dominance of TN in the consumer market.
TN displays suffer from limited viewing angles, especially in the vertical direction. Colors will shift when viewed off-perpendicular. In the vertical direction, colors will shift so much that they will invert past a certain angle.
Also, most TN panels represent colors using only six bit
s per RGB color, or 18 bit in total, and are unable to display the 16.7 million color shades (24-bit truecolor) that are available from graphics cards. Instead, these panels display interpolated 24-bit color using a dither
ing method that combines adjacent pixels to simulate the desired shade. They can also use a form of temporal dithering called Frame Rate Control
(FRC), which cycles between different shades with each new frame
to simulate an intermediate shade. Such 18 bit panels with dithering are sometimes advertised as having "16.2 million colors". These color simulation methods are noticeable to many people and highly bothersome to some. FRC tends to be most noticeable in darker tones, while dithering appears to make the individual pixels of the LCD visible. Overall, color reproduction and linearity on TN panels is poor. Shortcomings in display color gamut
(often referred to as a percentage of the NTSC 1953 color gamut
) are also due to backlighting technology. It is not uncommon for displays with simple LED
or CCFL-based lighting to range from 10% to 26% of the NTSC color gamut, whereas other kind of displays, utilizing more complicated CCFL or LED phosphor
formulations or RGB LED backlights, may extend past 100% of the NTSC color gamut, a difference quite perceivable by the human eye.
The transmittance
of a pixel of an LCD panel typically does not change linearly with the applied voltage, and the sRGB standard for computer monitors requires a specific nonlinear dependence of the amount of emitted light as a function of the RGB value.
was developed by Hitachi Ltd. in 1996 to improve on the poor viewing angle and the poor color reproduction of TN panels at that time. Its name comes from the main difference from TN panels, that the crystal molecules move parallel to the panel plane instead of perpendicular to it. This change reduces the amount of light scattering in the matrix, which gives IPS its characteristic wide viewing angles and good color reproduction.
Initial iterations of IPS technology were plagued by slow response time and a low contrast ratio but later evolutions have made marked improvements to these shortcomings. Because of its wide viewing angle and accurate color reproduction (with almost no off-angle color shift), IPS is widely employed in high-end monitors aimed at professional graphic artists, although with the recent fall in price it has been seen in the mainstream market as well.
contrast ratio
!Remarks
|-
|Super TFT||IPS||1996||Wide viewing angle||100/100
Base level||Most panels also support true 8-bit per channel color. These improvements came at the cost of a slower response time, initially about 50 ms. IPS panels were also extremely expensive.
|-
|Super-IPS||S-IPS||1998||Color shift free||100/137||IPS has since been superseded by S-IPS (Super-IPS, Hitachi Ltd. in 1998), which has all the benefits of IPS technology with the addition of improved pixel refresh timing.
|-
|Advanced Super-IPS||AS-IPS||2002||High transmittance||130/250||AS-IPS, also developed by Hitachi Ltd. in 2002, improves substantially on the contrast ratio of traditional S-IPS panels to the point where they are second only to some S-PVAs.
|-
|IPS-Provectus||IPS-Pro||2004||High contrast ratio||137/313||The latest panel from IPS Alpha Technology with a wider color gamut and contrast ratio matching PVA and ASV displays without off-angle glowing.
|-
|IPS alpha||IPS-Pro||2008||High contrast ratio||||Next generation of IPS-Pro
|-
|IPS alpha next gen||IPS-Pro||2010||High contrast ratio||||Technology transfer from Hitachi to Panasonic
|}
Thin film transistor liquid crystal display (TFT-LCD) is a variant of liquid crystal display
(LCD) which uses thin-film transistor
(TFT) technology to improve image quality (e.g., addressability, contrast). TFT LCD is one type of Active matrix
LCD, though all LCD-screens are based on TFT active matrix addressing. TFT LCDs are used in television set
s, computer monitors, mobile phone
s, handheld video game systems, personal digital assistant
s, navigation system
s, projector
s, etc.
Liquid crystal displays as used in calculators and devices have direct driven image elements – a voltage
can be applied across one segment without interfering with other segments of the display. This is impractical for a large display
with a large number of picture elements (pixel
s), since it would require millions of connections – top and bottom connections for each one of the three colors (red, green and blue) of every pixel. To avoid this issue, the pixels are addressed in rows and columns, reducing the connection count from millions to thousands. The column and row wires attach to transistor
switches, one for each pixel. The one-way current passing characteristic of the transistor prevents the charge applied to the pixel from draining between refreshes to the display image. Each pixel is a small capacitor
with a layer of insulating liquid crystal sandwiched between transparent conductive ITO
layers.
The circuit layout process of a TFT-LCD is very similar to that of semiconductor products. However, rather than fabricating the transistors from silicon
formed into a crystalline silicon
wafer, they are made from a thin film
of amorphous silicon
deposited on a glass
panel. The silicon layer for TFT-LCDs is typically deposited using the PECVD
process. Transistors take up only a small fraction of the area of each pixel; the rest of the silicon film is etched away to allow light to pass through.
Polycrystalline silicon
is sometimes used in displays requiring higher TFT performance. Examples include small high-resolution displays such as those found in projectors or view finders. Amorphous silicon-based TFTs are by far the most common due to their lower production cost, whereas polycrystalline silicon TFTs are more costly and difficult to produce.
The relatively inexpensive twisted nematic display is the most common consumer display type. The pixel response time on modern TN panels is sufficiently fast to avoid the shadow-trail and ghosting artifacts of earlier production. The fast response time has been emphasised in advertising TN displays, although in most cases this number does not reflect performance across the entire range of possible color transitions. More recent use of RTC (Response Time Compensation / Overdrive) technologies has allowed manufacturers to significantly reduce grey-to-grey (G2G) transitions, without significantly improving the ISO response time. Response times are now quoted in G2G figures, with 4ms and 2ms now being commonplace for TN-based models. The good response time and low cost has led to the dominance of TN in the consumer market.
TN displays suffer from limited viewing angles, especially in the vertical direction. Colors will shift when viewed off-perpendicular. In the vertical direction, colors will shift so much that they will invert past a certain angle.
Also, most TN panels represent colors using only six bit
s per RGB color, or 18 bit in total, and are unable to display the 16.7 million color shades (24-bit truecolor) that are available from graphics cards. Instead, these panels display interpolated 24-bit color using a dither
ing method that combines adjacent pixels to simulate the desired shade. They can also use a form of temporal dithering called Frame Rate Control
(FRC), which cycles between different shades with each new frame
to simulate an intermediate shade. Such 18 bit panels with dithering are sometimes advertised as having "16.2 million colors". These color simulation methods are noticeable to many people and highly bothersome to some. FRC tends to be most noticeable in darker tones, while dithering appears to make the individual pixels of the LCD visible. Overall, color reproduction and linearity on TN panels is poor. Shortcomings in display color gamut
(often referred to as a percentage of the NTSC 1953 color gamut
) are also due to backlighting technology. It is not uncommon for displays with simple LED
or CCFL-based lighting to range from 10% to 26% of the NTSC color gamut, whereas other kind of displays, utilizing more complicated CCFL or LED phosphor
formulations or RGB LED backlights, may extend past 100% of the NTSC color gamut, a difference quite perceivable by the human eye.
The transmittance
of a pixel of an LCD panel typically does not change linearly with the applied voltage, and the sRGB standard for computer monitors requires a specific nonlinear dependence of the amount of emitted light as a function of the RGB value.
was developed by Hitachi Ltd. in 1996 to improve on the poor viewing angle and the poor color reproduction of TN panels at that time. Its name comes from the main difference from TN panels, that the crystal molecules move parallel to the panel plane instead of perpendicular to it. This change reduces the amount of light scattering in the matrix, which gives IPS its characteristic wide viewing angles and good color reproduction.
Initial iterations of IPS technology were plagued by slow response time and a low contrast ratio but later evolutions have made marked improvements to these shortcomings. Because of its wide viewing angle and accurate color reproduction (with almost no off-angle color shift), IPS is widely employed in high-end monitors aimed at professional graphic artists, although with the recent fall in price it has been seen in the mainstream market as well.
Thin film transistor liquid crystal display (TFT-LCD) is a variant of liquid crystal display
(LCD) which uses thin-film transistor
(TFT) technology to improve image quality (e.g., addressability, contrast). TFT LCD is one type of Active matrix
LCD, though all LCD-screens are based on TFT active matrix addressing. TFT LCDs are used in television set
s, computer monitors, mobile phone
s, handheld video game systems, personal digital assistant
s, navigation system
s, projector
s, etc.
Liquid crystal displays as used in calculators and devices have direct driven image elements – a voltage
can be applied across one segment without interfering with other segments of the display. This is impractical for a large display
with a large number of picture elements (pixel
s), since it would require millions of connections – top and bottom connections for each one of the three colors (red, green and blue) of every pixel. To avoid this issue, the pixels are addressed in rows and columns, reducing the connection count from millions to thousands. The column and row wires attach to transistor
switches, one for each pixel. The one-way current passing characteristic of the transistor prevents the charge applied to the pixel from draining between refreshes to the display image. Each pixel is a small capacitor
with a layer of insulating liquid crystal sandwiched between transparent conductive ITO
layers.
The circuit layout process of a TFT-LCD is very similar to that of semiconductor products. However, rather than fabricating the transistors from silicon
formed into a crystalline silicon
wafer, they are made from a thin film
of amorphous silicon
deposited on a glass
panel. The silicon layer for TFT-LCDs is typically deposited using the PECVD
process. Transistors take up only a small fraction of the area of each pixel; the rest of the silicon film is etched away to allow light to pass through.
Polycrystalline silicon
is sometimes used in displays requiring higher TFT performance. Examples include small high-resolution displays such as those found in projectors or view finders. Amorphous silicon-based TFTs are by far the most common due to their lower production cost, whereas polycrystalline silicon TFTs are more costly and difficult to produce.
The relatively inexpensive twisted nematic display is the most common consumer display type. The pixel response time on modern TN panels is sufficiently fast to avoid the shadow-trail and ghosting artifacts of earlier production. The fast response time has been emphasised in advertising TN displays, although in most cases this number does not reflect performance across the entire range of possible color transitions. More recent use of RTC (Response Time Compensation / Overdrive) technologies has allowed manufacturers to significantly reduce grey-to-grey (G2G) transitions, without significantly improving the ISO response time. Response times are now quoted in G2G figures, with 4ms and 2ms now being commonplace for TN-based models. The good response time and low cost has led to the dominance of TN in the consumer market.
TN displays suffer from limited viewing angles, especially in the vertical direction. Colors will shift when viewed off-perpendicular. In the vertical direction, colors will shift so much that they will invert past a certain angle.
Also, most TN panels represent colors using only six bit
s per RGB color, or 18 bit in total, and are unable to display the 16.7 million color shades (24-bit truecolor) that are available from graphics cards. Instead, these panels display interpolated 24-bit color using a dither
ing method that combines adjacent pixels to simulate the desired shade. They can also use a form of temporal dithering called Frame Rate Control
(FRC), which cycles between different shades with each new frame
to simulate an intermediate shade. Such 18 bit panels with dithering are sometimes advertised as having "16.2 million colors". These color simulation methods are noticeable to many people and highly bothersome to some. FRC tends to be most noticeable in darker tones, while dithering appears to make the individual pixels of the LCD visible. Overall, color reproduction and linearity on TN panels is poor. Shortcomings in display color gamut
(often referred to as a percentage of the NTSC 1953 color gamut
) are also due to backlighting technology. It is not uncommon for displays with simple LED
or CCFL-based lighting to range from 10% to 26% of the NTSC color gamut, whereas other kind of displays, utilizing more complicated CCFL or LED phosphor
formulations or RGB LED backlights, may extend past 100% of the NTSC color gamut, a difference quite perceivable by the human eye.
The transmittance
of a pixel of an LCD panel typically does not change linearly with the applied voltage, and the sRGB standard for computer monitors requires a specific nonlinear dependence of the amount of emitted light as a function of the RGB value.
was developed by Hitachi Ltd. in 1996 to improve on the poor viewing angle and the poor color reproduction of TN panels at that time. Its name comes from the main difference from TN panels, that the crystal molecules move parallel to the panel plane instead of perpendicular to it. This change reduces the amount of light scattering in the matrix, which gives IPS its characteristic wide viewing angles and good color reproduction.
Initial iterations of IPS technology were plagued by slow response time and a low contrast ratio but later evolutions have made marked improvements to these shortcomings. Because of its wide viewing angle and accurate color reproduction (with almost no off-angle color shift), IPS is widely employed in high-end monitors aimed at professional graphic artists, although with the recent fall in price it has been seen in the mainstream market as well.
advanced fringe field switching is a technology similar to IPS or S-IPS offering superior performance and colour gamut with high luminosity. Colour shift and deviation caused by light leakage is corrected by optimizing the white gamut, which also enhances white/grey reproduction. AFFS is developed by Hydis Technologies Co., Ltd, Korea (formally Hyundai Electronics, LCD Task Force).
In 2004, Hydis Technologies Co.,LTD licensed its AFFS patent to Japan's Hitachi Displays. Hitachi is using AFFS to manufacture high end panels in their product line. In 2006, Hydis also licensed its AFFS to Sanyo Epson Imaging Devices Corporation.
Hydis introduced AFFS+ which improved outdoor readability in 2007.
as a compromise between TN and IPS. It achieved pixel response which was fast for its time, wide viewing angles, and high contrast at the cost of brightness and color reproduction. Modern MVA panels can offer wide viewing angles (second only to S-IPS technology), good black depth, good color reproduction and depth, and fast response times due to the use of RTC (Response Time Compensation
) technologies. When MVA panels are viewed off-perpendicular, colors will shift, but much less than for TN panels.
There are several "next-generation" technologies based on MVA, including AU Optronics' P-MVA and A-MVA, as well as Chi Mei Optoelectronics' S-MVA. Analysts predicted that MVA would dominate the mainstream market, but the less expensive and slightly faster TN overtook it. The pixel response times of MVAs rise dramatically with small changes in brightness. Less expensive MVA panels can use dithering and FRC (Frame Rate Control
).
and Sony
's joint venture S-LCD
. Developed independently, they offer similar features to MVA, but with higher contrast ratios of up to 3000:1. Less expensive PVA panels often use dithering and FRC
, while S-PVA panels all use at least 8 bits per color component and do not use color simulation methods. S-PVA also largely eliminated off angle glowing of solid blacks and reduced the off angle gamma shift. Some newer S-PVA panels offered by Eizo
offer 16-bit color internally . , which enables gamma and other corrections with reduced color banding. Some high end Sony
BRAVIA
LCD-TVs offer 10bit and xvYCC color support, for example the Bravia X4500 series. PVA and S-PVA offer the best black depth of any LCD type along with wide viewing angles. S-PVA also offers fast response times using modern RTC technologies.
. It is a VA mode where liquid crystal molecules orient perpendicular to the substrates in the off state. The bottom sub-pixel has continuously covered electrodes, while the upper one has a smaller area electrode in the center of the subpixel.
When the field is on, the liquid crystal molecules start to tilt towards the center of the sub-pixels because of the electric field; as a result, a continuous pinwheel alignment (CPA) is formed; the azimuthal angle rotates 360 degrees continuously resulting in an excellent viewing angle. The ASV mode is also called CPA mode.
is Super PLS, which bears similarities to IPS panels and touts improved viewing angles and image quality, increased brightness and lower production costs. PLS technology is expected to debut in the PC display market with the release of the Samsung S27A850 and S24A850 monitors in September 2011.
panel vendors for large display panels. The glass panel suppliers are as follows:
Raw LCD TFT panels are usually factory-sorted into three categories, with regard to the number of dead pixels, backlight evenness and general product quality. Additionally, there may be up to +/- 2ms maximum response time differences between individual panels that came off the same assembly line on the same day. The poorest-performing screens are then sold to no-name
vendors or used in "value" TFT monitors (for example, marked with letter V behind the type number), the medium performers are incorporated in gamer-oriented or home office bound TFT displays (sometimes marked with the capital letter S), and the best screens are usually reserved for use in "professional" grade TFT monitors (often marked with letter P or S after their type number).
VGA
, DVI
, HDMI
, or DisplayPort
interface, with many featuring a selection of these interfaces. Inside external display devices there is a controller board that will convert the video signal using color mapping
and image scaling
usually employing the discrete cosine transform
(DCT) in order to convert any video source like CVBS
, VGA
, DVI
, HDMI
etc. into digital RGB
at the native resolution of the display panel. In a laptop the graphics chip will directly produce a signal suitable for connection to the built-in TFT display. A control mechanism for the backlight
is usually included on the same controller board.
The low level interface of STN
, DSTN
, or TFT display panels use either single ended
TTL 5V signal for older displays or TTL 3.3V for slightly newer displays that transmits Pixel clock, Horizontal sync
, Vertical sync, Digital red, Digital green, Digital blue in parallel. Some models also feature input/display enable
, horizontal scan direction and vertical scan direction signals.
New and large (>15") TFT displays often use LVDS signaling that transmits the same contents as the parallel interface (Hsync, Vsync, RGB) but will put control and RGB
bits into a number of serial transmission lines synchronized
to a clock whose rate is equal to the pixel rate. LVDS transmits seven bits per clock per data line, with six bits being data and one bit used to signal if the other six bits need to be inverted in order to maintain DC balance. Low quality TFT displays often have three data lines and therefore only directly support 18 bits per pixel
, while better ones have a fourth data line so they can support 24 bits per pixel, which delivers truecolor. Ultra high end models can support even more colors by adding more lanes, that's how 30-bit color can be supported by five data lanes. Panel manufacturers are slowly replacing LVDS with Internal DisplayPort and Embedded DisplayPort, which allow sixfold reduction of the number of differential pairs.
Backlight
intensity is usually controlled by varying a few volts DC, or generating a PWM
signal, or adjusting a potentiometer
or simply fixed. This in turn controls a high-voltage DC-AC inverter
or a matrix of LEDs. The method to control the intensity of LED is to pulse them with PWM which can be source of harmonic flicker.
The bare display panel will only accept a digital video signal at the resolution determined by the panel pixel matrix designed at manufacture. Some screen panels will ignore the LSB
bits of the color information to present a consistent interface (8bit->6bit/color x3).
Laptop
displays can't be reused directly with an ordinary computer graphics card or as a television, because they lack a hardware rescaler that can resize the image to fit the native resolution of the display panel. With analogue signals like VGA, the display controller also needs to perform a high speed analog to digital
conversion. With digital input signals like DVI or HDMI some simple reordering of the bits is needed before feeding it to the rescaler if the input resolution doesn't match the display panel resolution. For CVBS (TV
) usage a tuner
and color decode from a quadrature amplitude modulation
(QAM) to Luminance (Y), Blue-Y (U), Red-Y (V)
representation which in turn is transformed into Red, Green Blue is needed.
Liquid crystal display
A liquid crystal display is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals . LCs do not emit light directly....
(LCD) which uses thin-film transistor
Thin-film transistor
A thin-film transistor is a special kind of field-effect transistor made by depositing thin films of a semiconductor active layer as well as the dielectric layer and metallic contacts over a supporting substrate. A common substrate is glass, since the primary application of TFTs is in liquid...
(TFT) technology to improve image quality (e.g., addressability, contrast). TFT LCD is one type of Active matrix
Active matrix
Active matrix is a type of addressing scheme used in flat panel displays. The term describes a method of switching individual elements of a flat panel display, using a CdSe or Silicon-based thin-film transistor for each pixel...
LCD, though all LCD-screens are based on TFT active matrix addressing. TFT LCDs are used in television set
Television set
A television set is a device that combines a tuner, display, and speakers for the purpose of viewing television. Television sets became a popular consumer product after the Second World War, using vacuum tubes and cathode ray tube displays...
s, computer monitors, mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s, handheld video game systems, personal digital assistant
Personal digital assistant
A personal digital assistant , also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet...
s, navigation system
Navigation system
A navigation system is a system that aids is navigation. Navigation systems may be entirely on board a vehicle or vessel, or they may be located elsewhere and communicate via radio or other signals with a vehicle or vessel, or they may use a combination of these methods.Navigation systems may be...
s, projector
Video projector
A video projector is an image projector that receives a video signal and projects the corresponding image on a projection screen using a lens system. All video projectors use a very bright light to project the image, and most modern ones can correct any curves, blurriness, and other...
s, etc.
Construction
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
can be applied across one segment without interfering with other segments of the display. This is impractical for a large display
Display device
A display device is an output device for presentation of information in visual or tactile form...
with a large number of picture elements (pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
s), since it would require millions of connections – top and bottom connections for each one of the three colors (red, green and blue) of every pixel. To avoid this issue, the pixels are addressed in rows and columns, reducing the connection count from millions to thousands. The column and row wires attach to transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
switches, one for each pixel. The one-way current passing characteristic of the transistor prevents the charge applied to the pixel from draining between refreshes to the display image. Each pixel is a small capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
with a layer of insulating liquid crystal sandwiched between transparent conductive ITO
Indium tin oxide
Indium tin oxide is a solid solution of indium oxide and tin oxide , typically 90% In2O3, 10% SnO2 by weight. It is transparent and colorless in thin layers while in bulk form it is yellowish to grey...
layers.
The circuit layout process of a TFT-LCD is very similar to that of semiconductor products. However, rather than fabricating the transistors from silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
formed into a crystalline silicon
Monocrystalline silicon
Monocrystalline silicon or single-crystal Si, or mono-Si is the base material of the electronic industry. It consists of silicon in which the crystal lattice of the entire solid is continuous, unbroken to its edges. It can be prepared intrinsic, i.e...
wafer, they are made from a thin film
Thin film
A thin film is a layer of material ranging from fractions of a nanometer to several micrometers in thickness. Electronic semiconductor devices and optical coatings are the main applications benefiting from thin film construction....
of amorphous silicon
Amorphous silicon
Amorphous silicon is the non-crystalline allotropic form of silicon. It can be deposited in thin films at low temperatures onto a variety of substrates, offering some unique capabilities for a variety of electronics.-Description:...
deposited on a glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
panel. The silicon layer for TFT-LCDs is typically deposited using the PECVD
Plasma-enhanced chemical vapor deposition
Plasma-enhanced chemical vapor deposition is a process used to deposit thin films from a gas state to a solid state on a substrate. Chemical reactions are involved in the process, which occur after creation of a plasma of the reacting gases...
process. Transistors take up only a small fraction of the area of each pixel; the rest of the silicon film is etched away to allow light to pass through.
Polycrystalline silicon
Polycrystalline silicon
Polycrystalline silicon, also called polysilicon, is a material consisting of small silicon crystals. It differs from single-crystal silicon, used for electronics and solar cells, and from amorphous silicon, used for thin film devices and solar cells....
is sometimes used in displays requiring higher TFT performance. Examples include small high-resolution displays such as those found in projectors or view finders. Amorphous silicon-based TFTs are by far the most common due to their lower production cost, whereas polycrystalline silicon TFTs are more costly and difficult to produce.
Twisted nematic (TN)
TN displays suffer from limited viewing angles, especially in the vertical direction. Colors will shift when viewed off-perpendicular. In the vertical direction, colors will shift so much that they will invert past a certain angle.
Also, most TN panels represent colors using only six bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
s per RGB color, or 18 bit in total, and are unable to display the 16.7 million color shades (24-bit truecolor) that are available from graphics cards. Instead, these panels display interpolated 24-bit color using a dither
Dither
Dither is an intentionally applied form of noise used to randomize quantization error, preventing large-scale patterns such as color banding in images...
ing method that combines adjacent pixels to simulate the desired shade. They can also use a form of temporal dithering called Frame Rate Control
Frame Rate Control
Frame Rate Control is a method for achieving higher color quality in low color resolution display panels such as TN+film LCD.Most TN panels represent colors using only 6 bits per RGB color, or 18 bit in total, and are unable to display the 16.7 million color shades that are available from...
(FRC), which cycles between different shades with each new frame
Refresh rate
The refresh rate is the number of times in a second that a display hardware draws the data...
to simulate an intermediate shade. Such 18 bit panels with dithering are sometimes advertised as having "16.2 million colors". These color simulation methods are noticeable to many people and highly bothersome to some. FRC tends to be most noticeable in darker tones, while dithering appears to make the individual pixels of the LCD visible. Overall, color reproduction and linearity on TN panels is poor. Shortcomings in display color gamut
Gamut
In color reproduction, including computer graphics and photography, the gamut, or color gamut , is a certain complete subset of colors. The most common usage refers to the subset of colors which can be accurately represented in a given circumstance, such as within a given color space or by a...
(often referred to as a percentage of the NTSC 1953 color gamut
RGB color space
An RGB color space is any additive color space based on the RGB color model. A particular RGB color space is defined by the three chromaticities of the red, green, and blue additive primaries, and can produce any chromaticity that is the triangle defined by those primary colors...
) are also due to backlighting technology. It is not uncommon for displays with simple LED
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....
or CCFL-based lighting to range from 10% to 26% of the NTSC color gamut, whereas other kind of displays, utilizing more complicated CCFL or LED phosphor
Phosphor
A phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
formulations or RGB LED backlights, may extend past 100% of the NTSC color gamut, a difference quite perceivable by the human eye.
The transmittance
Transmittance
In optics and spectroscopy, transmittance is the fraction of incident light at a specified wavelength that passes through a sample. A related term is absorptance, or absorption factor, which is the fraction of radiation absorbed by a sample at a specified wavelength...
of a pixel of an LCD panel typically does not change linearly with the applied voltage, and the sRGB standard for computer monitors requires a specific nonlinear dependence of the amount of emitted light as a function of the RGB value.
In-Plane Switching (IPS)
In-Plane SwitchingIPS panel
IPS panel technology was developed by Hitachi in 1996 to solve the two main limitations of TN-matrices at the time, those being small viewing angles and low-quality color reproduction...
was developed by Hitachi Ltd. in 1996 to improve on the poor viewing angle and the poor color reproduction of TN panels at that time. Its name comes from the main difference from TN panels, that the crystal molecules move parallel to the panel plane instead of perpendicular to it. This change reduces the amount of light scattering in the matrix, which gives IPS its characteristic wide viewing angles and good color reproduction.
Initial iterations of IPS technology were plagued by slow response time and a low contrast ratio but later evolutions have made marked improvements to these shortcomings. Because of its wide viewing angle and accurate color reproduction (with almost no off-angle color shift), IPS is widely employed in high-end monitors aimed at professional graphic artists, although with the recent fall in price it has been seen in the mainstream market as well.
contrast ratio
!Remarks
|-
|Super TFT||IPS||1996||Wide viewing angle||100/100
Base level||Most panels also support true 8-bit per channel color. These improvements came at the cost of a slower response time, initially about 50 ms. IPS panels were also extremely expensive.
|-
|Super-IPS||S-IPS||1998||Color shift free||100/137||IPS has since been superseded by S-IPS (Super-IPS, Hitachi Ltd. in 1998), which has all the benefits of IPS technology with the addition of improved pixel refresh timing.
|-
|Advanced Super-IPS||AS-IPS||2002||High transmittance||130/250||AS-IPS, also developed by Hitachi Ltd. in 2002, improves substantially on the contrast ratio of traditional S-IPS panels to the point where they are second only to some S-PVAs.
|-
|IPS-Provectus||IPS-Pro||2004||High contrast ratio||137/313||The latest panel from IPS Alpha Technology with a wider color gamut and contrast ratio matching PVA and ASV displays without off-angle glowing.
|-
|IPS alpha||IPS-Pro||2008||High contrast ratio||||Next generation of IPS-Pro
|-
|IPS alpha next gen||IPS-Pro||2010||High contrast ratio||||Technology transfer from Hitachi to Panasonic
|}
Thin film transistor liquid crystal display (TFT-LCD) is a variant of liquid crystal display
Liquid crystal display
A liquid crystal display is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals . LCs do not emit light directly....
(LCD) which uses thin-film transistor
Thin-film transistor
A thin-film transistor is a special kind of field-effect transistor made by depositing thin films of a semiconductor active layer as well as the dielectric layer and metallic contacts over a supporting substrate. A common substrate is glass, since the primary application of TFTs is in liquid...
(TFT) technology to improve image quality (e.g., addressability, contrast). TFT LCD is one type of Active matrix
Active matrix
Active matrix is a type of addressing scheme used in flat panel displays. The term describes a method of switching individual elements of a flat panel display, using a CdSe or Silicon-based thin-film transistor for each pixel...
LCD, though all LCD-screens are based on TFT active matrix addressing. TFT LCDs are used in television set
Television set
A television set is a device that combines a tuner, display, and speakers for the purpose of viewing television. Television sets became a popular consumer product after the Second World War, using vacuum tubes and cathode ray tube displays...
s, computer monitors, mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s, handheld video game systems, personal digital assistant
Personal digital assistant
A personal digital assistant , also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet...
s, navigation system
Navigation system
A navigation system is a system that aids is navigation. Navigation systems may be entirely on board a vehicle or vessel, or they may be located elsewhere and communicate via radio or other signals with a vehicle or vessel, or they may use a combination of these methods.Navigation systems may be...
s, projector
Video projector
A video projector is an image projector that receives a video signal and projects the corresponding image on a projection screen using a lens system. All video projectors use a very bright light to project the image, and most modern ones can correct any curves, blurriness, and other...
s, etc.
Construction
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
can be applied across one segment without interfering with other segments of the display. This is impractical for a large display
Display device
A display device is an output device for presentation of information in visual or tactile form...
with a large number of picture elements (pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
s), since it would require millions of connections – top and bottom connections for each one of the three colors (red, green and blue) of every pixel. To avoid this issue, the pixels are addressed in rows and columns, reducing the connection count from millions to thousands. The column and row wires attach to transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
switches, one for each pixel. The one-way current passing characteristic of the transistor prevents the charge applied to the pixel from draining between refreshes to the display image. Each pixel is a small capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
with a layer of insulating liquid crystal sandwiched between transparent conductive ITO
Indium tin oxide
Indium tin oxide is a solid solution of indium oxide and tin oxide , typically 90% In2O3, 10% SnO2 by weight. It is transparent and colorless in thin layers while in bulk form it is yellowish to grey...
layers.
The circuit layout process of a TFT-LCD is very similar to that of semiconductor products. However, rather than fabricating the transistors from silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
formed into a crystalline silicon
Monocrystalline silicon
Monocrystalline silicon or single-crystal Si, or mono-Si is the base material of the electronic industry. It consists of silicon in which the crystal lattice of the entire solid is continuous, unbroken to its edges. It can be prepared intrinsic, i.e...
wafer, they are made from a thin film
Thin film
A thin film is a layer of material ranging from fractions of a nanometer to several micrometers in thickness. Electronic semiconductor devices and optical coatings are the main applications benefiting from thin film construction....
of amorphous silicon
Amorphous silicon
Amorphous silicon is the non-crystalline allotropic form of silicon. It can be deposited in thin films at low temperatures onto a variety of substrates, offering some unique capabilities for a variety of electronics.-Description:...
deposited on a glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
panel. The silicon layer for TFT-LCDs is typically deposited using the PECVD
Plasma-enhanced chemical vapor deposition
Plasma-enhanced chemical vapor deposition is a process used to deposit thin films from a gas state to a solid state on a substrate. Chemical reactions are involved in the process, which occur after creation of a plasma of the reacting gases...
process. Transistors take up only a small fraction of the area of each pixel; the rest of the silicon film is etched away to allow light to pass through.
Polycrystalline silicon
Polycrystalline silicon
Polycrystalline silicon, also called polysilicon, is a material consisting of small silicon crystals. It differs from single-crystal silicon, used for electronics and solar cells, and from amorphous silicon, used for thin film devices and solar cells....
is sometimes used in displays requiring higher TFT performance. Examples include small high-resolution displays such as those found in projectors or view finders. Amorphous silicon-based TFTs are by far the most common due to their lower production cost, whereas polycrystalline silicon TFTs are more costly and difficult to produce.
Twisted nematic (TN)
TN displays suffer from limited viewing angles, especially in the vertical direction. Colors will shift when viewed off-perpendicular. In the vertical direction, colors will shift so much that they will invert past a certain angle.
Also, most TN panels represent colors using only six bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
s per RGB color, or 18 bit in total, and are unable to display the 16.7 million color shades (24-bit truecolor) that are available from graphics cards. Instead, these panels display interpolated 24-bit color using a dither
Dither
Dither is an intentionally applied form of noise used to randomize quantization error, preventing large-scale patterns such as color banding in images...
ing method that combines adjacent pixels to simulate the desired shade. They can also use a form of temporal dithering called Frame Rate Control
Frame Rate Control
Frame Rate Control is a method for achieving higher color quality in low color resolution display panels such as TN+film LCD.Most TN panels represent colors using only 6 bits per RGB color, or 18 bit in total, and are unable to display the 16.7 million color shades that are available from...
(FRC), which cycles between different shades with each new frame
Refresh rate
The refresh rate is the number of times in a second that a display hardware draws the data...
to simulate an intermediate shade. Such 18 bit panels with dithering are sometimes advertised as having "16.2 million colors". These color simulation methods are noticeable to many people and highly bothersome to some. FRC tends to be most noticeable in darker tones, while dithering appears to make the individual pixels of the LCD visible. Overall, color reproduction and linearity on TN panels is poor. Shortcomings in display color gamut
Gamut
In color reproduction, including computer graphics and photography, the gamut, or color gamut , is a certain complete subset of colors. The most common usage refers to the subset of colors which can be accurately represented in a given circumstance, such as within a given color space or by a...
(often referred to as a percentage of the NTSC 1953 color gamut
RGB color space
An RGB color space is any additive color space based on the RGB color model. A particular RGB color space is defined by the three chromaticities of the red, green, and blue additive primaries, and can produce any chromaticity that is the triangle defined by those primary colors...
) are also due to backlighting technology. It is not uncommon for displays with simple LED
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....
or CCFL-based lighting to range from 10% to 26% of the NTSC color gamut, whereas other kind of displays, utilizing more complicated CCFL or LED phosphor
Phosphor
A phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
formulations or RGB LED backlights, may extend past 100% of the NTSC color gamut, a difference quite perceivable by the human eye.
The transmittance
Transmittance
In optics and spectroscopy, transmittance is the fraction of incident light at a specified wavelength that passes through a sample. A related term is absorptance, or absorption factor, which is the fraction of radiation absorbed by a sample at a specified wavelength...
of a pixel of an LCD panel typically does not change linearly with the applied voltage, and the sRGB standard for computer monitors requires a specific nonlinear dependence of the amount of emitted light as a function of the RGB value.
In-Plane Switching (IPS)
In-Plane SwitchingIPS panel
IPS panel technology was developed by Hitachi in 1996 to solve the two main limitations of TN-matrices at the time, those being small viewing angles and low-quality color reproduction...
was developed by Hitachi Ltd. in 1996 to improve on the poor viewing angle and the poor color reproduction of TN panels at that time. Its name comes from the main difference from TN panels, that the crystal molecules move parallel to the panel plane instead of perpendicular to it. This change reduces the amount of light scattering in the matrix, which gives IPS its characteristic wide viewing angles and good color reproduction.
Initial iterations of IPS technology were plagued by slow response time and a low contrast ratio but later evolutions have made marked improvements to these shortcomings. Because of its wide viewing angle and accurate color reproduction (with almost no off-angle color shift), IPS is widely employed in high-end monitors aimed at professional graphic artists, although with the recent fall in price it has been seen in the mainstream market as well.
| Name | Nickname | Year | Advantage | Transmittance/ contrast ratio |
Remarks |
|---|---|---|---|---|---|
| Super TFT | IPS | 1996 | Wide viewing angle | 100/100 Base level |
Most panels also support true 8-bit per channel color. These improvements came at the cost of a slower response time, initially about 50 ms. IPS panels were also extremely expensive. |
| Super-IPS | S-IPS | 1998 | Color shift free | 100/137 | IPS has since been superseded by S-IPS (Super-IPS, Hitachi Ltd. in 1998), which has all the benefits of IPS technology with the addition of improved pixel refresh timing. |
| Advanced Super-IPS | AS-IPS | 2002 | High transmittance | 130/250 | AS-IPS, also developed by Hitachi Ltd. in 2002, improves substantially on the contrast ratio of traditional S-IPS panels to the point where they are second only to some S-PVAs. |
| IPS-Provectus | IPS-Pro | 2004 | High contrast ratio | 137/313 | The latest panel from IPS Alpha Technology with a wider color gamut and contrast ratio matching PVA and ASV displays without off-angle glowing. |
| IPS alpha | IPS-Pro | 2008 | High contrast ratio | Next generation of IPS-Pro | |
| IPS alpha next gen | IPS-Pro | 2010 | High contrast ratio | Technology transfer from Hitachi to Panasonic |
Thin film transistor liquid crystal display (TFT-LCD) is a variant of liquid crystal display
Liquid crystal display
A liquid crystal display is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals . LCs do not emit light directly....
(LCD) which uses thin-film transistor
Thin-film transistor
A thin-film transistor is a special kind of field-effect transistor made by depositing thin films of a semiconductor active layer as well as the dielectric layer and metallic contacts over a supporting substrate. A common substrate is glass, since the primary application of TFTs is in liquid...
(TFT) technology to improve image quality (e.g., addressability, contrast). TFT LCD is one type of Active matrix
Active matrix
Active matrix is a type of addressing scheme used in flat panel displays. The term describes a method of switching individual elements of a flat panel display, using a CdSe or Silicon-based thin-film transistor for each pixel...
LCD, though all LCD-screens are based on TFT active matrix addressing. TFT LCDs are used in television set
Television set
A television set is a device that combines a tuner, display, and speakers for the purpose of viewing television. Television sets became a popular consumer product after the Second World War, using vacuum tubes and cathode ray tube displays...
s, computer monitors, mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
s, handheld video game systems, personal digital assistant
Personal digital assistant
A personal digital assistant , also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet...
s, navigation system
Navigation system
A navigation system is a system that aids is navigation. Navigation systems may be entirely on board a vehicle or vessel, or they may be located elsewhere and communicate via radio or other signals with a vehicle or vessel, or they may use a combination of these methods.Navigation systems may be...
s, projector
Video projector
A video projector is an image projector that receives a video signal and projects the corresponding image on a projection screen using a lens system. All video projectors use a very bright light to project the image, and most modern ones can correct any curves, blurriness, and other...
s, etc.
Construction
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
can be applied across one segment without interfering with other segments of the display. This is impractical for a large display
Display device
A display device is an output device for presentation of information in visual or tactile form...
with a large number of picture elements (pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
s), since it would require millions of connections – top and bottom connections for each one of the three colors (red, green and blue) of every pixel. To avoid this issue, the pixels are addressed in rows and columns, reducing the connection count from millions to thousands. The column and row wires attach to transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
switches, one for each pixel. The one-way current passing characteristic of the transistor prevents the charge applied to the pixel from draining between refreshes to the display image. Each pixel is a small capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
with a layer of insulating liquid crystal sandwiched between transparent conductive ITO
Indium tin oxide
Indium tin oxide is a solid solution of indium oxide and tin oxide , typically 90% In2O3, 10% SnO2 by weight. It is transparent and colorless in thin layers while in bulk form it is yellowish to grey...
layers.
The circuit layout process of a TFT-LCD is very similar to that of semiconductor products. However, rather than fabricating the transistors from silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
formed into a crystalline silicon
Monocrystalline silicon
Monocrystalline silicon or single-crystal Si, or mono-Si is the base material of the electronic industry. It consists of silicon in which the crystal lattice of the entire solid is continuous, unbroken to its edges. It can be prepared intrinsic, i.e...
wafer, they are made from a thin film
Thin film
A thin film is a layer of material ranging from fractions of a nanometer to several micrometers in thickness. Electronic semiconductor devices and optical coatings are the main applications benefiting from thin film construction....
of amorphous silicon
Amorphous silicon
Amorphous silicon is the non-crystalline allotropic form of silicon. It can be deposited in thin films at low temperatures onto a variety of substrates, offering some unique capabilities for a variety of electronics.-Description:...
deposited on a glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
panel. The silicon layer for TFT-LCDs is typically deposited using the PECVD
Plasma-enhanced chemical vapor deposition
Plasma-enhanced chemical vapor deposition is a process used to deposit thin films from a gas state to a solid state on a substrate. Chemical reactions are involved in the process, which occur after creation of a plasma of the reacting gases...
process. Transistors take up only a small fraction of the area of each pixel; the rest of the silicon film is etched away to allow light to pass through.
Polycrystalline silicon
Polycrystalline silicon
Polycrystalline silicon, also called polysilicon, is a material consisting of small silicon crystals. It differs from single-crystal silicon, used for electronics and solar cells, and from amorphous silicon, used for thin film devices and solar cells....
is sometimes used in displays requiring higher TFT performance. Examples include small high-resolution displays such as those found in projectors or view finders. Amorphous silicon-based TFTs are by far the most common due to their lower production cost, whereas polycrystalline silicon TFTs are more costly and difficult to produce.
Twisted nematic (TN)
TN displays suffer from limited viewing angles, especially in the vertical direction. Colors will shift when viewed off-perpendicular. In the vertical direction, colors will shift so much that they will invert past a certain angle.
Also, most TN panels represent colors using only six bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
s per RGB color, or 18 bit in total, and are unable to display the 16.7 million color shades (24-bit truecolor) that are available from graphics cards. Instead, these panels display interpolated 24-bit color using a dither
Dither
Dither is an intentionally applied form of noise used to randomize quantization error, preventing large-scale patterns such as color banding in images...
ing method that combines adjacent pixels to simulate the desired shade. They can also use a form of temporal dithering called Frame Rate Control
Frame Rate Control
Frame Rate Control is a method for achieving higher color quality in low color resolution display panels such as TN+film LCD.Most TN panels represent colors using only 6 bits per RGB color, or 18 bit in total, and are unable to display the 16.7 million color shades that are available from...
(FRC), which cycles between different shades with each new frame
Refresh rate
The refresh rate is the number of times in a second that a display hardware draws the data...
to simulate an intermediate shade. Such 18 bit panels with dithering are sometimes advertised as having "16.2 million colors". These color simulation methods are noticeable to many people and highly bothersome to some. FRC tends to be most noticeable in darker tones, while dithering appears to make the individual pixels of the LCD visible. Overall, color reproduction and linearity on TN panels is poor. Shortcomings in display color gamut
Gamut
In color reproduction, including computer graphics and photography, the gamut, or color gamut , is a certain complete subset of colors. The most common usage refers to the subset of colors which can be accurately represented in a given circumstance, such as within a given color space or by a...
(often referred to as a percentage of the NTSC 1953 color gamut
RGB color space
An RGB color space is any additive color space based on the RGB color model. A particular RGB color space is defined by the three chromaticities of the red, green, and blue additive primaries, and can produce any chromaticity that is the triangle defined by those primary colors...
) are also due to backlighting technology. It is not uncommon for displays with simple LED
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....
or CCFL-based lighting to range from 10% to 26% of the NTSC color gamut, whereas other kind of displays, utilizing more complicated CCFL or LED phosphor
Phosphor
A phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
formulations or RGB LED backlights, may extend past 100% of the NTSC color gamut, a difference quite perceivable by the human eye.
The transmittance
Transmittance
In optics and spectroscopy, transmittance is the fraction of incident light at a specified wavelength that passes through a sample. A related term is absorptance, or absorption factor, which is the fraction of radiation absorbed by a sample at a specified wavelength...
of a pixel of an LCD panel typically does not change linearly with the applied voltage, and the sRGB standard for computer monitors requires a specific nonlinear dependence of the amount of emitted light as a function of the RGB value.
In-Plane Switching (IPS)
In-Plane SwitchingIPS panel
IPS panel technology was developed by Hitachi in 1996 to solve the two main limitations of TN-matrices at the time, those being small viewing angles and low-quality color reproduction...
was developed by Hitachi Ltd. in 1996 to improve on the poor viewing angle and the poor color reproduction of TN panels at that time. Its name comes from the main difference from TN panels, that the crystal molecules move parallel to the panel plane instead of perpendicular to it. This change reduces the amount of light scattering in the matrix, which gives IPS its characteristic wide viewing angles and good color reproduction.
Initial iterations of IPS technology were plagued by slow response time and a low contrast ratio but later evolutions have made marked improvements to these shortcomings. Because of its wide viewing angle and accurate color reproduction (with almost no off-angle color shift), IPS is widely employed in high-end monitors aimed at professional graphic artists, although with the recent fall in price it has been seen in the mainstream market as well.
| Name | Nickname | Year | Advantage | Transmittance/ contrast ratio |
Remarks |
|---|---|---|---|---|---|
| Super TFT | IPS | 1996 | Wide viewing angle | 100/100 Base level |
Most panels also support true 8-bit per channel color. These improvements came at the cost of a slower response time, initially about 50 ms. IPS panels were also extremely expensive. |
| Super-IPS | S-IPS | 1998 | Color shift free | 100/137 | IPS has since been superseded by S-IPS (Super-IPS, Hitachi Ltd. in 1998), which has all the benefits of IPS technology with the addition of improved pixel refresh timing. |
| Advanced Super-IPS | AS-IPS | 2002 | High transmittance | 130/250 | AS-IPS, also developed by Hitachi Ltd. in 2002, improves substantially on the contrast ratio of traditional S-IPS panels to the point where they are second only to some S-PVAs. |
| IPS-Provectus | IPS-Pro | 2004 | High contrast ratio | 137/313 | The latest panel from IPS Alpha Technology with a wider color gamut and contrast ratio matching PVA and ASV displays without off-angle glowing. |
| IPS alpha | IPS-Pro | 2008 | High contrast ratio | Next generation of IPS-Pro | |
| IPS alpha next gen | IPS-Pro | 2010 | High contrast ratio | Technology transfer from Hitachi to Panasonic |
| Name | Nickname | Year | Remarks |
|---|---|---|---|
| Super-IPS | S-IPS | 2001 | LG Display remains as one of the main manufacturers of panels based on Hitachi Super-IPS. |
| Advanced Super-IPS | AS-IPS | 2005 | Increased contrast ratio with better color gamut. |
| Horizontal IPS | H-IPS | 2007 | Improves contrast ratio by twisting electrode plane layout. Also introduces an optional Advanced True Whide polarizing film from NEC, to make white look more natural. This is used in professional/photography LCDs. |
| Enhanced IPS | E-IPS | 2009 | Wider aperture for light transmission, enabling the use of lower-power, cheaper backlights. Improves diagonal viewing angle and further reduce response time to 5ms. |
| Professional IPS | P-IPS | 2010 | Offer 1.07 billion colours (30-bit colour depth). More possible orientations per sub-pixel (1024 as opposed to 256) and produces a better true colour depth. |
| Advanced High Performance IPS | AH-IPS | 2011 | Improved colour accuracy, increased resolution and PPI, and greater light transmission for lower power consumption. |
Advanced fringe field switching (AFFS)
This is an LCD technology derived from the IPS by Boe-Hydis of Korea. Known as fringe field switching (FFS) until 2003,advanced fringe field switching is a technology similar to IPS or S-IPS offering superior performance and colour gamut with high luminosity. Colour shift and deviation caused by light leakage is corrected by optimizing the white gamut, which also enhances white/grey reproduction. AFFS is developed by Hydis Technologies Co., Ltd, Korea (formally Hyundai Electronics, LCD Task Force).
In 2004, Hydis Technologies Co.,LTD licensed its AFFS patent to Japan's Hitachi Displays. Hitachi is using AFFS to manufacture high end panels in their product line. In 2006, Hydis also licensed its AFFS to Sanyo Epson Imaging Devices Corporation.
Hydis introduced AFFS+ which improved outdoor readability in 2007.
Multi-domain vertical alignment (MVA)
Multi-domain vertical alignment was originally developed in 1998 by FujitsuFujitsu
is a Japanese multinational information technology equipment and services company headquartered in Tokyo, Japan. It is the world's third-largest IT services provider measured by revenues....
as a compromise between TN and IPS. It achieved pixel response which was fast for its time, wide viewing angles, and high contrast at the cost of brightness and color reproduction. Modern MVA panels can offer wide viewing angles (second only to S-IPS technology), good black depth, good color reproduction and depth, and fast response times due to the use of RTC (Response Time Compensation
Response Time Compensation
Response time compensation is also known as "Overdrive". LCDs moderate light flow by rotating liquid crystal molecules to various alignments where they transmit more or less light depending on the electrical setting at each individual pixel. The speed at which these liquid crystal molecules...
) technologies. When MVA panels are viewed off-perpendicular, colors will shift, but much less than for TN panels.
There are several "next-generation" technologies based on MVA, including AU Optronics' P-MVA and A-MVA, as well as Chi Mei Optoelectronics' S-MVA. Analysts predicted that MVA would dominate the mainstream market, but the less expensive and slightly faster TN overtook it. The pixel response times of MVAs rise dramatically with small changes in brightness. Less expensive MVA panels can use dithering and FRC (Frame Rate Control
Frame Rate Control
Frame Rate Control is a method for achieving higher color quality in low color resolution display panels such as TN+film LCD.Most TN panels represent colors using only 6 bits per RGB color, or 18 bit in total, and are unable to display the 16.7 million color shades that are available from...
).
Patterned vertical alignment (PVA)
Patterned vertical alignment and super patterned vertical alignment (S-PVA) are alternative versions of MVA technology offered by Samsung'sSamsung Group
The Samsung Group is a South Korean multinational conglomerate corporation headquartered in Samsung Town, Seoul, South Korea...
and Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
's joint venture S-LCD
S-LCD
S-LCD Corporation is a joint venture between the South Korean Samsung Electronics Co. Ltd and Japanese Sony Corporation established in April 2004 in Chungcheongnam-do, South Korea....
. Developed independently, they offer similar features to MVA, but with higher contrast ratios of up to 3000:1. Less expensive PVA panels often use dithering and FRC
Frame Rate Control
Frame Rate Control is a method for achieving higher color quality in low color resolution display panels such as TN+film LCD.Most TN panels represent colors using only 6 bits per RGB color, or 18 bit in total, and are unable to display the 16.7 million color shades that are available from...
, while S-PVA panels all use at least 8 bits per color component and do not use color simulation methods. S-PVA also largely eliminated off angle glowing of solid blacks and reduced the off angle gamma shift. Some newer S-PVA panels offered by Eizo
Eizo
, or EIZO, is a manufacturer of high-end computer displays. A Japanese corporation, it was founded in March 1968 but did not adopt its current name until 1999 when Nanao Corporation and Eizo merged...
offer 16-bit color internally . , which enables gamma and other corrections with reduced color banding. Some high end Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
BRAVIA
BRAVIA
BRAVIA is a Sony brand used to market its high-definition LCD televisions, projection TVs and front projectors and for the PlayStation 3 , along with its home cinema range under the sub-brand BRAVIA Theatre. The BRAVIA name is an acronym of "Best Resolution Audio Visual Integrated Architecture"...
LCD-TVs offer 10bit and xvYCC color support, for example the Bravia X4500 series. PVA and S-PVA offer the best black depth of any LCD type along with wide viewing angles. S-PVA also offers fast response times using modern RTC technologies.
Advanced super view (ASV)
Advanced super view, also called axially symmetric vertical alignment was developed by SharpSharp Corporation
is a Japanese multinational corporation that designs and manufactures electronic products. Headquartered in Abeno-ku, Osaka, Japan, Sharp employs more than 55,580 people worldwide as of June 2011. The company was founded in September 1912 and takes its name from one of its founder's first...
. It is a VA mode where liquid crystal molecules orient perpendicular to the substrates in the off state. The bottom sub-pixel has continuously covered electrodes, while the upper one has a smaller area electrode in the center of the subpixel.
When the field is on, the liquid crystal molecules start to tilt towards the center of the sub-pixels because of the electric field; as a result, a continuous pinwheel alignment (CPA) is formed; the azimuthal angle rotates 360 degrees continuously resulting in an excellent viewing angle. The ASV mode is also called CPA mode.
Plane Line Switching (PLS)
A new technology developed by SamsungSamsung
The Samsung Group is a South Korean multinational conglomerate corporation headquartered in Samsung Town, Seoul, South Korea...
is Super PLS, which bears similarities to IPS panels and touts improved viewing angles and image quality, increased brightness and lower production costs. PLS technology is expected to debut in the PC display market with the release of the Samsung S27A850 and S24A850 monitors in September 2011.
Display industry
Due to the very high cost of building TFT factories, there are few major OEMOriginal Equipment Manufacturer
An original equipment manufacturer, or OEM, manufactures products or components that are purchased by a company and retailed under that purchasing company's brand name. OEM refers to the company that originally manufactured the product. When referring to automotive parts, OEM designates a...
panel vendors for large display panels. The glass panel suppliers are as follows:
| LCD glass panel suppliers | |||
|---|---|---|---|
| Panel type | Company | Remarks | major TV makers |
| IPS-Pro | Panasonic Panasonic Panasonic is an international brand name for Japanese electric products manufacturer Panasonic Corporation, which was formerly known as Matsushita Electric Industrial Co., Ltd... |
Solely for LCD TV markets and known as IPS Alpha Technology Ltd. | Panasonic, Hitachi, Toshiba |
| H-IPS & P-IPS | LG Display | They also produce other type of TFT panels such as TN for OEM markets such as mobile, monitor, automotive, portable AV and industrial panels. | LG, Philips, BenQ |
| S-IPS | Hannstar HannStar Display Corporation HannStar Display Corporation is a Taiwan-based technology company, primarily involved in the research and production of monitors, notebook displays, and televisions.-Overview:... |
||
| Chuangwa Picture Tubes, Ltd. | |||
| A-MVA | AU Optronics AU Optronics AU Optronics was formed in December 2001 by the merger of Acer Display Technology, Inc., and Unipac Optoelectronics Corporation. In October 2006, AUO merged with Quanta Display Inc. to create a leading TFT-LCD manufacturer. Additionally, the amassed production of the company's G6 reached worldwide... |
||
| S-MVA | Chi Mei Optoelectronics | ||
| S-PVA | S-LCD S-LCD S-LCD Corporation is a joint venture between the South Korean Samsung Electronics Co. Ltd and Japanese Sony Corporation established in April 2004 in Chungcheongnam-do, South Korea.... (Samsung Samsung Group The Samsung Group is a South Korean multinational conglomerate corporation headquartered in Samsung Town, Seoul, South Korea... /Sony Sony , commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues.... joint venture) |
Samsung, Sony | |
| AFFS | Samsung Samsung The Samsung Group is a South Korean multinational conglomerate corporation headquartered in Samsung Town, Seoul, South Korea... |
For small and medium size special projects. | |
| ASV | Sharp Corporation Sharp Corporation is a Japanese multinational corporation that designs and manufactures electronic products. Headquartered in Abeno-ku, Osaka, Japan, Sharp employs more than 55,580 people worldwide as of June 2011. The company was founded in September 1912 and takes its name from one of its founder's first... |
Solely for LCD TV markets | Sharp |
Raw LCD TFT panels are usually factory-sorted into three categories, with regard to the number of dead pixels, backlight evenness and general product quality. Additionally, there may be up to +/- 2ms maximum response time differences between individual panels that came off the same assembly line on the same day. The poorest-performing screens are then sold to no-name
Generic brand
Generic brands of consumer products are distinguished by the absence of a brand name. It is often inaccurate to describe these products as "lacking a brand name", as they usually are branded, albeit with either the brand of the store in which they are sold or a lesser-known brand name which may...
vendors or used in "value" TFT monitors (for example, marked with letter V behind the type number), the medium performers are incorporated in gamer-oriented or home office bound TFT displays (sometimes marked with the capital letter S), and the best screens are usually reserved for use in "professional" grade TFT monitors (often marked with letter P or S after their type number).
Electrical interface
External consumer display devices like a TFT LCD feature one or more analogAnalog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
VGA
Video Graphics Array
Video Graphics Array refers specifically to the display hardware first introduced with the IBM PS/2 line of computers in 1987, but through its widespread adoption has also come to mean either an analog computer display standard, the 15-pin D-subminiature VGA connector or the 640×480 resolution...
, DVI
Digital Visual Interface
The Digital Visual Interface is a video interface standard covering the transmission of video between a source device and a display device. The DVI standard has achieved widespread acceptance in the PC industry, both in desktop PCs and monitors...
, HDMI
High-Definition Multimedia Interface
HDMI is a compact audio/video interface for transmitting uncompressed digital data. It is a digital alternative to consumer analog standards, such as radio frequency coaxial cable, composite video, S-Video, SCART, component video, D-Terminal, or VGA...
, or DisplayPort
DisplayPort
DisplayPort is a digital display interface standard produced by the Video Electronics Standards Association . The specification defines a royalty-free digital interconnect for audio and video. The interface is primarily used to connect a video source to a display device such as a computer monitor...
interface, with many featuring a selection of these interfaces. Inside external display devices there is a controller board that will convert the video signal using color mapping
Color mapping
Color mapping is a function that maps the colors of one image to the colors of another image. A color mapping may be referred to as the algorithm that results in the mapping function or the algorithm that transforms the image colors...
and image scaling
Image scaling
In computer graphics, image scaling is the process of resizing a digital image. Scaling is a non-trivial process that involves a trade-off between efficiency, smoothness and sharpness. As the size of an image is increased, so the pixels which comprise the image become increasingly visible, making...
usually employing the discrete cosine transform
Discrete cosine transform
A discrete cosine transform expresses a sequence of finitely many data points in terms of a sum of cosine functions oscillating at different frequencies. DCTs are important to numerous applications in science and engineering, from lossy compression of audio and images A discrete cosine transform...
(DCT) in order to convert any video source like CVBS
Composite video
Composite video is the format of an analog television signal before it is combined with a sound signal and modulated onto an RF carrier. In contrast to component video it contains all required video information, including colors in a single line-level signal...
, VGA
Video Graphics Array
Video Graphics Array refers specifically to the display hardware first introduced with the IBM PS/2 line of computers in 1987, but through its widespread adoption has also come to mean either an analog computer display standard, the 15-pin D-subminiature VGA connector or the 640×480 resolution...
, DVI
Digital Visual Interface
The Digital Visual Interface is a video interface standard covering the transmission of video between a source device and a display device. The DVI standard has achieved widespread acceptance in the PC industry, both in desktop PCs and monitors...
, HDMI
High-Definition Multimedia Interface
HDMI is a compact audio/video interface for transmitting uncompressed digital data. It is a digital alternative to consumer analog standards, such as radio frequency coaxial cable, composite video, S-Video, SCART, component video, D-Terminal, or VGA...
etc. into digital RGB
RGB color model
The RGB color model is an additive color model in which red, green, and blue light is added together in various ways to reproduce a broad array of colors...
at the native resolution of the display panel. In a laptop the graphics chip will directly produce a signal suitable for connection to the built-in TFT display. A control mechanism for the backlight
Backlight
A backlight is a form of illumination used in liquid crystal displays . As LCDs do not produce light themselves , they need illumination to produce a visible image...
is usually included on the same controller board.
The low level interface of STN
Super-twisted nematic display
A super-twisted nematic display is a type of monochrome passive matrix liquid crystal display . STN displays provide more contrast than twisted nematic displays by twisting the molecules from 180 to 270 degrees...
, DSTN
Dual Scan
Dual Scan, also known as dual-scan supertwist nematic or DSTN, is an LCD technology in which a screen is divided into two sections which are simultaneously refreshed giving faster refresh rate than traditional passive matrix screens. It is an improved form of supertwist nematic display that offers...
, or TFT display panels use either single ended
Single-ended signalling
Single-ended signaling is the simplest and most commonly used method of transmitting electrical signals over wires. One wire carries a varying voltage that represents the signal, while the other wire is connected to a reference voltage, usually ground....
TTL 5V signal for older displays or TTL 3.3V for slightly newer displays that transmits Pixel clock, Horizontal sync
Horizontal scan rate
Horizontal scan rate, or horizontal frequency, usually expressed in kilohertz, is the frequency at which a CRT moves the electron beam from the left side of the display to the right and back, and therefore describes the number of horizontal lines displayed per second...
, Vertical sync, Digital red, Digital green, Digital blue in parallel. Some models also feature input/display enable
Chip select
Chip select or slave select is the name of a control line in digital electronics used to select one chip out of several connected to the same computer bus usually utilizing the three-state logic....
, horizontal scan direction and vertical scan direction signals.
New and large (>15") TFT displays often use LVDS signaling that transmits the same contents as the parallel interface (Hsync, Vsync, RGB) but will put control and RGB
RGB color model
The RGB color model is an additive color model in which red, green, and blue light is added together in various ways to reproduce a broad array of colors...
bits into a number of serial transmission lines synchronized
Synchronization
Synchronization is timekeeping which requires the coordination of events to operate a system in unison. The familiar conductor of an orchestra serves to keep the orchestra in time....
to a clock whose rate is equal to the pixel rate. LVDS transmits seven bits per clock per data line, with six bits being data and one bit used to signal if the other six bits need to be inverted in order to maintain DC balance. Low quality TFT displays often have three data lines and therefore only directly support 18 bits per pixel
Color depth
In computer graphics, color depth or bit depth is the number of bits used to represent the color of a single pixel in a bitmapped image or video frame buffer. This concept is also known as bits per pixel , particularly when specified along with the number of bits used...
, while better ones have a fourth data line so they can support 24 bits per pixel, which delivers truecolor. Ultra high end models can support even more colors by adding more lanes, that's how 30-bit color can be supported by five data lanes. Panel manufacturers are slowly replacing LVDS with Internal DisplayPort and Embedded DisplayPort, which allow sixfold reduction of the number of differential pairs.
Backlight
Backlight
A backlight is a form of illumination used in liquid crystal displays . As LCDs do not produce light themselves , they need illumination to produce a visible image...
intensity is usually controlled by varying a few volts DC, or generating a PWM
Pulse-width modulation
Pulse-width modulation , or pulse-duration modulation , is a commonly used technique for controlling power to inertial electrical devices, made practical by modern electronic power switches....
signal, or adjusting a potentiometer
Potentiometer
A potentiometer , informally, a pot, is a three-terminal resistor with a sliding contact that forms an adjustable voltage divider. If only two terminals are used , it acts as a variable resistor or rheostat. Potentiometers are commonly used to control electrical devices such as volume controls on...
or simply fixed. This in turn controls a high-voltage DC-AC inverter
Inverter (electrical)
An inverter is an electrical device that converts direct current to alternating current ; the converted AC can be at any required voltage and frequency with the use of appropriate transformers, switching, and control circuits....
or a matrix of LEDs. The method to control the intensity of LED is to pulse them with PWM which can be source of harmonic flicker.
The bare display panel will only accept a digital video signal at the resolution determined by the panel pixel matrix designed at manufacture. Some screen panels will ignore the LSB
Least significant bit
In computing, the least significant bit is the bit position in a binary integer giving the units value, that is, determining whether the number is even or odd. The lsb is sometimes referred to as the right-most bit, due to the convention in positional notation of writing less significant digits...
bits of the color information to present a consistent interface (8bit->6bit/color x3).
Laptop
Laptop
A laptop, also called a notebook, is a personal computer for mobile use. A laptop integrates most of the typical components of a desktop computer, including a display, a keyboard, a pointing device and speakers into a single unit...
displays can't be reused directly with an ordinary computer graphics card or as a television, because they lack a hardware rescaler that can resize the image to fit the native resolution of the display panel. With analogue signals like VGA, the display controller also needs to perform a high speed analog to digital
Analog-to-digital converter
An analog-to-digital converter is a device that converts a continuous quantity to a discrete time digital representation. An ADC may also provide an isolated measurement...
conversion. With digital input signals like DVI or HDMI some simple reordering of the bits is needed before feeding it to the rescaler if the input resolution doesn't match the display panel resolution. For CVBS (TV
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
) usage a tuner
Tuner (radio)
A radio tuner is a subsystem that receives radio broadcasts and converts them into audio-frequency signals which can be fed into an amplifier driving a loudspeaker. FM tuner, AM tuner, Digital Audio Broadcasting DAB tuner, etc. are types of radio tuner dealing with transmissions using different...
and color decode from a quadrature amplitude modulation
Quadrature amplitude modulation
Quadrature amplitude modulation is both an analog and a digital modulation scheme. It conveys two analog message signals, or two digital bit streams, by changing the amplitudes of two carrier waves, using the amplitude-shift keying digital modulation scheme or amplitude modulation analog...
(QAM) to Luminance (Y), Blue-Y (U), Red-Y (V)
YUV
YUV is a color space typically used as part of a color image pipeline. It encodes a color image or video taking human perception into account, allowing reduced bandwidth for chrominance components, thereby typically enabling transmission errors or compression artifacts to be more efficiently...
representation which in turn is transformed into Red, Green Blue is needed.
See also
- Computer monitor
- Liquid crystal display televisionLiquid crystal display televisionLiquid-crystal display televisions are television sets that use LCD display technology to produce images. LCD televisions are thinner and lighter than cathode ray tube of similar display size, and are available in much larger sizes...
- Transflective liquid crystal display, for adaptation to environment brightness
- Liquid crystalLiquid crystalLiquid crystals are a state of matter that have properties between those of a conventional liquid and those of a solid crystal. For instance, an LC may flow like a liquid, but its molecules may be oriented in a crystal-like way. There are many different types of LC phases, which can be...
- Burst dimmingBurst dimmingBurst dimming is a method to control dimming of cold cathode fluorescent lamps by using pulse width modulation at approximately 100-300 Hz which is supposed to be above the noticeable flicker limit for the human eye....
- Display examplesDisplay examplesOver the years, a variety of display devices and technologies have been used in order to display electronic data in a way that's legible to humans.-Early history:...
External links
- TFT Central - Reviews, News and Articles. Includes panel search database
- FlatpanelsHD.com - LCD monitor panel search database
- Animated LCD Tutorial by 3M3M3M Company , formerly known as the Minnesota Mining and Manufacturing Company, is an American multinational conglomerate corporation based in Maplewood, Minnesota, United States....
- LCD Panels with Response Time Compensation, X-bit labs, December 20, 2005
- Contemporary LCD Monitor Parameters and Characteristics, X-bit labs, October 26, 2004
- Gaming issues with TFT LCD Displays, Digital Silence, August 10, 2004
- What is TFT LCD, Plasma.com – detailed description of the technology inside a TFT LCD
- Monitor buying guide - CNETCNETCNET is a tech media website that publishes news articles, blogs, and podcasts on technology and consumer electronics. Originally founded in 1994 by Halsey Minor and Shelby Bonnie, it was the flagship brand of CNET Networks and became a brand of CBS Interactive through CNET Networks' acquisition...
reviews
