lcd display driver circuit free sample

The present invention pertains to displays and, particularly, to liquid crystal displays (LCD"s). More particularly, the invention pertains to active matrix LCD"s.

LCD technology is being developed as a possible successor to cathode ray tube (CRT) technology for many applications. LCD technology offers important advantages, such as higher reliability and reduced power, size and weight. However, in the current state of development, LCD image rendering capability falls short of that achievable using CRT"s. The present invention addresses one of the major technical obstacles which is the unacceptable flicker of flat panel LCD"s.

The flicker problem originates in the manner that LCD"s are driven. Flat panel LCD"s need to be refreshed periodically with alternating voltage. The polarity of the voltage is typically switched after each vertical sync in order to prevent electroplating action from occurring. Electroplating action can damage electrodes inside the flat panel. Odd frames 11 of the image are driven by a minus voltage (-V), for example, while even frames 12 are driven by a positive voltage (+V) (in FIGS. 1a and 1b). Since the electro-optical response of the LC material depends solely on the magnitude of the voltage (V), polarity changes after each frame should have no optical effect. However, polarity changes do have a noticeable effect.

FIGS. 1a and 1b reveal the prior art off-axis output of an LCD. FIG. 1a is a graph showing the idealized average level of optical output per frame, 11 or 12, relative to the voltage polarities of the driving signals, as distributed temporally. FIG. 1b shows how the polarity dependent regions are distributed spatially over a display surface. The regions are switched to the opposite polarity at the end of each frame. Each of the regions cover the entire image display. The optical output has a frequency component that is one-half of the frame frequency.

Active matrix LCD technology is preferred in cockpit applications, because it has great potential for realizing the required level of performance under adverse conditions. Active matrix displays typically use semiconductor devices as switches (most often thin film transistors) to transfer appropriate voltages to each LC picture element (i.e., pixel). Although these switching devices are designed to behave independently of polarity, they exhibit asymmetric properties. They appear to charge faster or conduct better for one polarity than for the other. Consequently, active matrix LC Displays, using such polarity-dependent devices to energize the LC material, manifest polarity-dependent optical behavior (FIGS. 2a and 2b). This polarity-dependent optical behavior is perceived as flicker by the eye. FIGS. 2a and 2b are graphs that reveal the output of an LCD having switched polarities, at a plus 45 degree viewing angle and a minus 45 degree viewing angle, respectively.

Part of the flicker effect can be tuned out for a given viewing angle by adjusting the magnitudes of the applied voltages. Some display designers in the industry have found this to be an adequate solution. The voltages are adjusted to compensate for the polarity dependence. For example, the magnitude of +V may be made slightly higher than that of -V to account for biases in the active matrix LCD. However, because of the complex characteristics of LCD"s, such tuning fails when the panel is viewed from other angles. So, for applications requiring wide viewing angles this solution is inadequate.

In general, if the panel is refreshed at frequency (F), then the polarity must be alternated at every half period or at frequency F/2. Because of the asymmetries mentioned above, polarity alternation causes the optical output of the LC display to have an undesirable side effect; the image gets modulated at F/2. An image refreshed at 60 hertz (Hz) will cause a 30 Hz frequency component to appear over the entire surface of the screen. 30 Hz results in very perceptible and objectionable flicker. On this basis, those skilled in the art conclude the refresh frequency must be raised to the point where F/2 is high enough to avoid flicker. In the inventors" laboratory, the refresh frequency had to be raised to 90 Hz. However, high refresh frequencies have severe penalties associated with them. Such frequencies raise the complexity, speed and cost of the entire display system. Transistors in the LCD must be designed to operate faster. The graphics processors, image memories and interface circuitry in the symbol generator and the display head require higher performance components and must use more costly architectures which are items to be avoided whenever possible.

The invention circumvents LCD flicker difficulties without incurring the more costly architectures needed for the high refresh frequencies, by taking advantage of spatial and temporal frequency characteristics in the human visual system. The eye has been modeled as having two separate channels for acquiring spatial information. One channel, which has fast neurons, responds to rapid luminance changes as long as the changes occur over broad feature sizes (low spatial frequency). The channel has high bandwidth in the temporal frequency domain but low bandwidth in the spatial frequency domain. The other channel, using slow neurons but sensitive to small feature sizes, behaves in an opposite manner. It can resolve fine image detail but responds slowly to what it discriminates. It has high bandwidth in the spatial frequency dimension but low bandwidth in the temporal frequency dimension.

The above-described model of the eye implies that changing polarity globally over the entire surface of the display, as has been done, is incorrect. Polarity changes over a broad region are detected by the fast channel of the eye where the changes are easily noticed. However, polarity changes made locally, in small regions, are less likely to be detected, wherein the eye is not able to detect the optical effects of the rapid polarity changes. Placing the shifts in the domain of high spatial frequencies puts the flicker problem in the slow detection channel of the eye. Interwoven rows, columns or any patterns of small feature size are used in the invention to keep the spatial frequency of the polarity pattern high enough. In this way, flicker is eliminated.

The preferred embodiment of the invention includes a column driver integrated circuit (IC) which permits columns to be conveniently and efficiently interwoven. It uses a segment of drivers for the even columns and another segment for the odd columns. Each segment can be connected to voltage supply rails of opposite polarity. The even segment can be connected to one polarity, while the odd segment can be connected to the other polarity. This done, the odd and even outputs can be interwoven out of the IC, providing convenient routing to the panel.

Alternatively, a selection signal on the IC can place the driver into a traditional drive configuration. The driver can be directed to connect the odd segment and the even segment together to select the same supply rails. Further, this driver can be implemented to provide either analog or digital output control.

Moreover, both anti-flicker drivers need to be attached to only on edge of the flat panel display to eliminate flicker, as opposed to the current art which requires attachment to opposite edges of the flat panel displays. This results in mechanical benefits, including smaller size, simpler layout and easier implementation. These features are amenable to long-term objectives for installing the drivers within the flat panel display itself.

Another embodiment of the invention has a column driver tailored to include anti-flicker capability. By making its polarity switch operate faster, it is optimized for delivering row interweave capability. The input normally driven by the frame signal, which alternates after every vertical retrace, is instead driven by a signal which alternates after every row.

The present invention is usable with a wide range of formats. In view of the fact that many products use an extensive variety of scanning formats and because flicker is so dependent on timing, such general applicability of the present invention is extremely desirable. Further, because of the tight volume constraints targeted for most flat panel applications, obtaining mechanical efficiency while eliminating flicker through the present invention is also significant. In summary, today"s flat panel drivers do not provide anti-flicker functionality like that of the present invention.

FIGS. 2a and 2b are graphs that reveal the output of an LCD having switched polarities, at a plus 45 degree viewing angle and a minus 45 degree viewing angle, respectively.

FIGS. 3a and 3b show, in contrast to FIG. 1a, the difference in off-axis optical outputs of the LCD in the prior art and the invention, respectively. The optical output versus time shows the different level outputs 16 and 17 to be happening at the same time at a much higher spatial frequency in FIG. 3a, in contrast to the low frequency outputs 11 and 12 in FIGS. 1a and 1b. The higher spatial frequency of the interwoven rows allows the eye to see only the average of the two levels, 16 and 17, present. FIG. 3b spatially shows optical outputs 18 and 19 on the display having parts of the screen at different voltage levels or polarities for the same frame. FIG. 3b shows the polarities of the rows switching from even frame 18 to odd frame 19, after each frame scan is completed.

In order for the present invention to operate, the column drivers need to be modified to switch from one polarity to the other more quickly. Typically, switching happens during a vertical retrace, when several hundred microseconds are available for the transition. To switch at the end of a row, however, the column drivers need to be able to change polarity in a manner that will not waste valuable scan time. Each row lasts on the order of only a few tens of microseconds, typically from 16 to 63 microseconds. Therefore, in order to minimize adverse effects, the column drivers need to be able to change polarity in less than a few microseconds, ideally in less than one microsecond. An improved column driver, one which provides functionality for eliminating flicker, is one which uses standard technology to deliver a faster polarity switch.

In the inventors" laboratory, the slow switching speed of the column drivers was compensated by extending the row time and by reducing the number of rows in the image. These two things, together, were done to maintain a given image refresh rate. As was stated earlier, interweaving the rows in this manner eliminated flicker altogether and made the viewer feel as if he were observing a stable image displayed on a sheet of paper instead of on a periodically refreshed electronic display device.

Another approach, as shown in FIGS. 4a and 4b, is to interweave polarity changes using columns. FIG. 4a and 4b illustrate the off-axis optical outputs 20-23, temporally and spatially, for a column implementation of the invention. FIG. 4a shows the optical outputs 20 and 21 per pair of columns for the even and odd frames. The eye tends to integrate the plus and minus regions within outputs 20 and 21 into a constant level output. FIG. 4b illustrates the column optical outputs 22 and 23 over the display surface for even and odd frames, respectively, wherein the polarities are switched after each frame. The regions of opposite polarities are averaged into a DC level.

This can be done by placing standard column drivers 24 and 25 at the top and at the bottom of display panel 26 (as shown in FIG. 5). The polarity changes are interwoven among the columns by the standard drivers 24 and 25. Drivers 24 and 25 refresh the image with an alternating voltage. At any given time, even columns 28 use one polarity while odd columns 27 use the other polarity. Each polarity changes to the other after each frame (or vertical sync signal). The top set of column drivers 24 can be used to drive even columns 28 and the bottom set of drivers 25 can be used to drive odd columns 27. To achieve the interwoven polarity changes, the top set of drivers 24 can be used to apply voltages of one polarity while the bottom set of drivers 25 can be used to apply the other. After each frame is completed, signified by the occurrence of a vertical sync pulse, the polarities are reversed on the top and bottom drivers, 24 and 25, respectively. This method was also tested in the laboratory. As might be expected, given the model for the human visual system, interwoven columns succeeded in eliminating flicker just as effectively as the row method did.

Another approach is to tailor a new type of column driver IC, different from the one described above, to more efficiently achieve interwoven columns, as shown in FIG. 6. This particular driver arrangement can circumvent certain mechanical difficulties, which have become evident while implementing prototypes of methods described above. Only a single edge of flat panel 90 is needed, as revealed in FIG. 7, instead of two. This results in more flexibility. Wiring is simpler and the overall display module can be made smaller. Placing drivers 92 within panel 90, for an extremely compact and desirable method of assembly, is also feasible. In summary, since all the interweaving is accomplished within each driver IC, display module designs can be more flexible. The designs can be made to be more efficient and easier to implement.

For a large panel 100, perhaps ten by ten inches in size, for example, as in FIG. 8, long bus lines are expected to induce performance non-uniformities, especially in terms of gray scale. To minimize long bus line impedances, resultant losses and other effects, redundant drives 102 are used. Incorporating redundant drives 102 with anti-flicker capability, impossible with prior art drivers, is possible with the present drivers. FIG. 8 is a diagram of a redundant drive for large panels to avoid yield problems or gray scale non-uniformities.

FIG. 6 shows a block diagram of column driver 30 tailored to eliminate flicker. Column driver 30 interweaves the columns. Functional blocks 34, 36, 38 and 40 are standard. The output stage, i.e., the driver amplifier section, is not standard. The output stage is implemented in two separately controllable segments, i.e., the even driver segment 32 and the odd driver segment 33.

Both driver segments 32 and 33 can be connected to either of source voltages 42 and 44 via supply rails 46 and 47 and switches 50 and 51. Source voltages 42 and 44 are typically of the same magnitude with respect to Voff on rails 48 and 49 but of opposite polarity to each other. Switches 50 and 51 control which one of the two voltages 42 and 44 is directed to the supply rails 46 and 47, respectively. Switches 50 and 51 are controlled by the frame module 40 which is driven by frame signal 54. Frame signal 54 is typically driven by some form of the traditional vertical sync signal issued from the video source. Frame signal 54 is binary and oscillates with a period twice as long as that of the vertical sync. So after every vertical sync, switches 50 and 51 change position and select the polarity opposite of that of the previous cycle. Thus, drivers 32 and 33 provide alternating drive voltages to the panel to activate pixels. Alternating the polarity avoids electrolytic action inside the panel, which can be damaging.

A sense signal 52 is optional and may be used to command switches 50 and 51 to select the same polarity rather than the opposite polarity. Signal 52 is useful for using the driver in a traditional manner or in an anti-flicker mode in which two edges of the panel can be used to provide polarity interleaving (as illustrated in FIG. 5).

Together, rails 46, 47, 48 and 49 supply binary levels of voltage to drivers 32 and 33. These binary levels can be used to provide binary or analog images. An analog optical output can be obtained, while using binary signal levels by time-modulating the length of time that switches 56 are "on", i.e., selecting activation rails 46 and 47 or by time-modulating the length of the time that active elements within the panel are allowed to be "on" and driven by this column driver.

Each pixel in the panel acts essentially as a capacitor driven by a current source. The longer the current source is allowed to charge a capacitor, the more voltage accumulates across it. Since the optical output is proportional to voltage, a continuous range of gray scales can be made available. The current source is allowed to charge the pixel capacitance under control of one of the column drivers 32 and 33 and the drive signals on the rows of the panel. This general category of control using fixed levels but varying "on" time to achieve a continuous range of control is often designated as pulse-width modulation.

Segments 32 and 33 are physically arranged so that their outputs are interwoven at the pins of integrated circuit 60 of FIG. 9. Even and odd outputs alternate around the periphery of package 60. The number of outputs should be even in order to enable the convenient cascading of one driver with subsequent or prior drivers.

FIG. 10 shows an analog column driver 74 having similar anti-flicker functionality as that shown in FIG. 6, but for analog voltage levels. Inverting amplifier 62 is used to provide a polarity-reversed image of the incoming video signal. Switches 106 going to the analog drivers are once again such that odd and even outputs are interwoven to deliver opposite polarities. The polarity of Vin going to each of sampling rails 64 and 65 is controlled by sampling switches 66 and 67. The even drivers are connected to rail 64 while the odd drivers are connected to rail 65. The polarity of the analog video present on the even rail 64, is the opposite of that on the odd rail 65 (unless once again a sense signal is applied to make the two rail switches 66 and 67 connect the same polarity). This approach results in column interweave for eliminating flicker but with a continuous range of analog voltage levels out. The same sort of rail switching is used as in the binary level case shown in FIG. 6. Rail switches 66 and 67 are controlled by the frame signal. Shift register 76, with a clock input, provides timing for sampling the input analog voltage.

Two banks 68 and 70 of capacitors (or a equivalent analog storage means) permit columns to be driven from one bank while video signals arrive and are stored in the other bank. The capacitors of banks 68 and 70 store samples of the voltages having polarities that are a function of the odd/even column count. Banks 68 and 70 operate in a ping-pong fashion, always storing an incoming line of video while writing to the flat panel with a previous line of video. Therefore, selector 72 must precede each driver output buffer. Selector 72 is a switch that chooses which capacitor bank is to be connected to the drivers.

Another embodiment is illustrated by FIG. 11 which shows the block diagram of column driver 80 which includes anti-flicker functionality. FIG. 11 is similar to FIG. 6 except for the implementation of the rail select switch 82.

Rail select switch 82 routes either +V or -V to the drivers as determined by frame signal 84. Using standard transistor technology, switch 82 can be made much faster than those currently used in the art. In the prior art, the rail switch was not optimized to deliver speed needed to provide anti-flicker capability. The fact that flicker could be reduced by improved peripheral drive circuitry was not recognized in the prior art. But, using faster transistors like those in the driver stage 86, rail switch 82 can be implemented to change polarities in just a few microseconds. Thus, the polarity coming from driver stage 86 can be switched at the end of every row.

Driver 80 can be used to eliminate flicker using the row interweave technique of FIGS. 3a and 3b. Frame signal 84 must be altered to switch after every row instead of after every vertical trace, which is accomplished by connecting the frame circuit to a signal derived from horizontal sync instead of vertical sync. To ensure that each and every pixel is addressed with both +V and -V, in alternation, either an odd number of horizontal sync pulses per vertical interval must be guaranteed, or a simple horizontal/vertical sync circuit can be used to change the starting polarity after each interval. Nothing prevents the user from connecting the frame circuit to the traditional frame signal driven by vertical sync, which, if desired, would place this driver into a mode of the prior art.

Microchip Technology has announced a new line of PI eXtreme Low Power (XLP) microcontrollers (MCUs). Packed with 14 types of Core Independent Peripherals (CIPs) that operate outside the Central Processing Unit (CPU) for power savings, the 16-bit PIC24F GU and GL families of MCUs feature the CIP called LCD with Autonomous Animation.

Most display applications involve a few common animations like periodically alternating between displays and blinking of pixels to indicate operation, says Microchip. By using the integrated LCD driver with autonomous animation, developers can offload most of these simple animation routines from the CPU, allowing animation even in doze, idle or sleep modes for optimal power savings. To assist in quickly designing such display interfaces, the new MCUs come with MPLAB Code Configurator (MCC) support. This graphical programming environment with LCD display designer helps eliminate the meticulous and time-consuming task of mapping the pins and segments.

The new MCU families are also designed to make it easy to increase the security of an application, whether it is connected to the Internet or a standalone system. Microchip’s CodeGuard security Flash protection enables segmenting memory into boot and general segments to implement memory access restrictions. The Flash memory is configurable as One Time Programmable (OTP) via Microchip’s In-Circuit Serial Programming (ICSP™) write inhibit feature that disables any further modification of the Flash through external programmers/debuggers. Together with these features, security can be further enhanced using Microchip’s CryptoAuthentication devices as companion chips to add secure over-the-air updates and pre-provisioned cloud services. Lastly, the MCUs are supported by CryptoAuthLib, 16-bit bootloader, USB and many application libraries in MCC to significantly reduce development time and complexities.

The PIC24F GU and GL MCUs are supported by Microchip’s MPLAB development ecosystem including Microchip’s free MPLAB X Integrated Development Environment (IDE) and MPLAB Code Configurator. Other supporting boards include the PIC24F LCD and USB Curiosity Development Board, PIC24F LCD Curiosity Development Board, and the PIC24FJ512GU410 and PIC24FJ128GL306 General Purpose Plug-In Modules (PIMs) for the Explorer 16/32 Development Board.

The PIC24F GL3 family with integrated LCD is available in 28-, 36-, 48- and 64-pin packages as small as 4mm x 4mm (uQFN). Memory ranges from 64KB to 128KB Flash and 8 KB RAM. The PIC24F GU4/GL4 family with integrated LCD and USB is available in 48-, 64-, 80- and 100-pin packages with memory ranges from 128KB to 512KB flash and 32KB RAM. Prices start at $0.97 in high volume for the PIC24FJ64GL302-I/SS.

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Nuvoton has announced its NuMicro ML56, a microcontroller series with low power, built-in capacitive touch sensing and LCD driver. It is based on a 1T 8051 core has embedded 64KB flash and 4KB SRAM. It runs less than 100 µA/MHz power in normal run mode with a power-down current below 2µA with an LCD panel display. NuMicro ML56 series runs up to 24MHz, operating from 1.8V to 3.6V and -40°C to 105°C. With up to 14 channels of touch keys and 224 dots of LCD driver, it can provide the user interface for IIoT applications were low power is critical.

The NuMicro ML56 series integrates capacitive touch sensing circuit with enhanced touch key controller, supporting up to 14 independent touch channels with low power characteristics, waterproof and high noise resistance features. With less than 2 µA consumption, you can complete all the touch keys’ calibration in power-down mode. Also, the touch key can be one of the wake-up sources. In terms of waterproofing, even in a 2mm depth water droplet the ML56 series can still identify the exact finger touch. IEC 61000-4-6 conducted noise immunity (CNI) with 10-Vrms noise voltage helps customer pass their EMC standard, which makes it especially suitable for home appliances and industrial control. Nuvoton provides a complete development tool and touch library to shorten customer development times and to mass production by easy calibration of touch key functions.

The NuMicro ML56 series has built-in 4 COM x 32 SEG, 6 COM x 30 SEG, 8 COM x 28 SEG LCD controllers to drive up to 224 dots, and supports the Type-A and Type-B LCD panel. It provides two VLCD input sources: external voltage, and another is an internal charge pump. The internal charge pump keeps the VLCD constant voltage to maintain the LCD panel’s display quality while VDD input changes. There are two VLCD driving modes: buffer mode and internal resistor mode. The buffer mode with a strong driving current supports up to 10cm x 10cm large-sized panel. The internal resistor mode drives small-sized panels and reduces power consumption.

Nuvoton provides easy-to-use development tools such as Nu-Link/ Nu-Link-Pro/ Nu-Link2-Pro supporting advanced debug function, PinConfigure multi-function pin setting, PinView showing pin status in real-time, BSP driver and single button/slider/wheel sample codes. The IDE supports Keil C-51 and IAR EW8051, which can debug, trace and analyze your program on the development board. Nuvoton provides NuSenadj touch key calibration tool for the mass production of a touch key.

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Would you like to write for Circuit Cellar? We are always accepting articles/posts from the technical community. Get in touch with us and let"s discuss your ideas.

A fully digital driving circuit for thin-film transistor liquid crystal display can offer benefits, including less power consumption and a shortened design schedule. Using the pulsewidth signal to control the moment to stop the ramp voltage, the pixel voltage can be set accurately. In this paper, the possible issues of power consumption, device nonuniformity, and parasitic capacitance are well-studied to prove the feasibility and advantages of the digital driving method. It is prospectively…Expand

Glass substrate with ITO electrodes. The shapes of these electrodes will determine the shapes that will appear when the LCD is switched ON. Vertical ridges etched on the surface are smooth.

A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liquid crystals do not emit light directlybacklight or reflector to produce images in color or monochrome.seven-segment displays, as in a digital clock, are all good examples of devices with these displays. They use the same basic technology, except that arbitrary images are made from a matrix of small pixels, while other displays have larger elements. LCDs can either be normally on (positive) or off (negative), depending on the polarizer arrangement. For example, a character positive LCD with a backlight will have black lettering on a background that is the color of the backlight, and a character negative LCD will have a black background with the letters being of the same color as the backlight. Optical filters are added to white on blue LCDs to give them their characteristic appearance.

LCDs are used in a wide range of applications, including LCD televisions, computer monitors, instrument panels, aircraft cockpit displays, and indoor and outdoor signage. Small LCD screens are common in LCD projectors and portable consumer devices such as digital cameras, watches, digital clocks, calculators, and mobile telephones, including smartphones. LCD screens are also used on consumer electronics products such as DVD players, video game devices and clocks. LCD screens have replaced heavy, bulky cathode-ray tube (CRT) displays in nearly all applications. LCD screens are available in a wider range of screen sizes than CRT and plasma displays, with LCD screens available in sizes ranging from tiny digital watches to very large television receivers. LCDs are slowly being replaced by OLEDs, which can be easily made into different shapes, and have a lower response time, wider color gamut, virtually infinite color contrast and viewing angles, lower weight for a given display size and a slimmer profile (because OLEDs use a single glass or plastic panel whereas LCDs use two glass panels; the thickness of the panels increases with size but the increase is more noticeable on LCDs) and potentially lower power consumption (as the display is only "on" where needed and there is no backlight). OLEDs, however, are more expensive for a given display size due to the very expensive electroluminescent materials or phosphors that they use. Also due to the use of phosphors, OLEDs suffer from screen burn-in and there is currently no way to recycle OLED displays, whereas LCD panels can be recycled, although the technology required to recycle LCDs is not yet widespread. Attempts to maintain the competitiveness of LCDs are quantum dot displays, marketed as SUHD, QLED or Triluminos, which are displays with blue LED backlighting and a Quantum-dot enhancement film (QDEF) that converts part of the blue light into red and green, offering similar performance to an OLED display at a lower price, but the quantum dot layer that gives these displays their characteristics can not yet be recycled.

Since LCD screens do not use phosphors, they rarely suffer image burn-in when a static image is displayed on a screen for a long time, e.g., the table frame for an airline flight schedule on an indoor sign. LCDs are, however, susceptible to image persistence.battery-powered electronic equipment more efficiently than a CRT can be. By 2008, annual sales of televisions with LCD screens exceeded sales of CRT units worldwide, and the CRT became obsolete for most purposes.

Each pixel of an LCD typically consists of a layer of molecules aligned between two transparent electrodes, often made of Indium-Tin oxide (ITO) and two polarizing filters (parallel and perpendicular polarizers), the axes of transmission of which are (in most of the cases) perpendicular to each other. Without the liquid crystal between the polarizing filters, light passing through the first filter would be blocked by the second (crossed) polarizer. Before an electric field is applied, the orientation of the liquid-crystal molecules is determined by the alignment at the surfaces of electrodes. In a twisted nematic (TN) device, the surface alignment directions at the two electrodes are perpendicular to each other, and so the molecules arrange themselves in a helical structure, or twist. This induces the rotation of the polarization of the incident light, and the device appears gray. If the applied voltage is large enough, the liquid crystal molecules in the center of the layer are almost completely untwisted and the polarization of the incident light is not rotated as it passes through the liquid crystal layer. This light will then be mainly polarized perpendicular to the second filter, and thus be blocked and the pixel will appear black. By controlling the voltage applied across the liquid crystal layer in each pixel, light can be allowed to pass through in varying amounts thus constituting different levels of gray.

The chemical formula of the liquid crystals used in LCDs may vary. Formulas may be patented.Sharp Corporation. The patent that covered that specific mixture expired.

Most color LCD systems use the same technique, with color filters used to generate red, green, and blue subpixels. The LCD color filters are made with a photolithography process on large glass sheets that are later glued with other glass sheets containing a TFT array, spacers and liquid crystal, creating several color LCDs that are then cut from one another and laminated with polarizer sheets. Red, green, blue and black photoresists (resists) are used. All resists contain a finely ground powdered pigment, with particles being just 40 nanometers across. The black resist is the first to be applied; this will create a black grid (known in the industry as a black matrix) that will separate red, green and blue subpixels from one another, increasing contrast ratios and preventing light from leaking from one subpixel onto other surrounding subpixels.Super-twisted nematic LCD, where the variable twist between tighter-spaced plates causes a varying double refraction birefringence, thus changing the hue.

LCD in a Texas Instruments calculator with top polarizer removed from device and placed on top, such that the top and bottom polarizers are perpendicular. As a result, the colors are inverted.

The optical effect of a TN device in the voltage-on state is far less dependent on variations in the device thickness than that in the voltage-off state. Because of this, TN displays with low information content and no backlighting are usually operated between crossed polarizers such that they appear bright with no voltage (the eye is much more sensitive to variations in the dark state than the bright state). As most of 2010-era LCDs are used in television sets, monitors and smartphones, they have high-resolution matrix arrays of pixels to display arbitrary images using backlighting with a dark background. When no image is displayed, different arrangements are used. For this purpose, TN LCDs are operated between parallel polarizers, whereas IPS LCDs feature crossed polarizers. In many applications IPS LCDs have replaced TN LCDs, particularly in smartphones. Both the liquid crystal material and the alignment layer material contain ionic compounds. If an electric field of one particular polarity is applied for a long period of time, this ionic material is attracted to the surfaces and degrades the device performance. This is avoided either by applying an alternating current or by reversing the polarity of the electric field as the device is addressed (the response of the liquid crystal layer is identical, regardless of the polarity of the applied field).

Displays for a small number of individual digits or fixed symbols (as in digital watches and pocket calculators) can be implemented with independent electrodes for each segment.alphanumeric or variable graphics displays are usually implemented with pixels arranged as a matrix consisting of electrically connected rows on one side of the LC layer and columns on the other side, which makes it possible to address each pixel at the intersections. The general method of matrix addressing consists of sequentially addressing one side of the matrix, for example by selecting the rows one-by-one and applying the picture information on the other side at the columns row-by-row. For details on the various matrix addressing schemes see passive-matrix and active-matrix addressed LCDs.

LCDs, along with OLED displays, are manufactured in cleanrooms borrowing techniques from semiconductor manufacturing and using large sheets of glass whose size has increased over time. Several displays are manufactured at the same time, and then cut from the sheet of glass, also known as the mother glass or LCD glass substrate. The increase in size allows more displays or larger displays to be made, just like with increasing wafer sizes in semiconductor manufacturing. The glass sizes are as follows:

Until Gen 8, manufacturers would not agree on a single mother glass size and as a result, different manufacturers would use slightly different glass sizes for the same generation. Some manufacturers have adopted Gen 8.6 mother glass sheets which are only slightly larger than Gen 8.5, allowing for more 50 and 58 inch LCDs to be made per mother glass, specially 58 inch LCDs, in which case 6 can be produced on a Gen 8.6 mother glass vs only 3 on a Gen 8.5 mother glass, significantly reducing waste.AGC Inc., Corning Inc., and Nippon Electric Glass.

The origins and the complex history of liquid-crystal displays from the perspective of an insider during the early days were described by Joseph A. Castellano in Liquid Gold: The Story of Liquid Crystal Displays and the Creation of an Industry.IEEE History Center.Peter J. Wild, can be found at the Engineering and Technology History Wiki.

In 1922, Georges Friedel described the structure and properties of liquid crystals and classified them in three types (nematics, smectics and cholesterics). In 1927, Vsevolod Frederiks devised the electrically switched light valve, called the Fréedericksz transition, the essential effect of all LCD technology. In 1936, the Marconi Wireless Telegraph company patented the first practical application of the technology, "The Liquid Crystal Light Valve". In 1962, the first major English language publication Molecular Structure and Properties of Liquid Crystals was published by Dr. George W. Gray.RCA found that liquid crystals had some interesting electro-optic characteristics and he realized an electro-optical effect by generating stripe-patterns in a thin layer of liquid crystal material by the application of a voltage. This effect is based on an electro-hydrodynamic instability forming what are now called "Williams domains" inside the liquid crystal.

In 1964, George H. Heilmeier, then working at the RCA laboratories on the effect discovered by Williams achieved the switching of colors by field-induced realignment of dichroic dyes in a homeotropically oriented liquid crystal. Practical problems with this new electro-optical effect made Heilmeier continue to work on scattering effects in liquid crystals and finally the achievement of the first operational liquid-crystal display based on what he called the George H. Heilmeier was inducted in the National Inventors Hall of FameIEEE Milestone.

In the late 1960s, pioneering work on liquid crystals was undertaken by the UK"s Royal Radar Establishment at Malvern, England. The team at RRE supported ongoing work by George William Gray and his team at the University of Hull who ultimately discovered the cyanobiphenyl liquid crystals, which had correct stability and temperature properties for application in LCDs.

The idea of a TFT-based liquid-crystal display (LCD) was conceived by Bernard Lechner of RCA Laboratories in 1968.dynamic scattering mode (DSM) LCD that used standard discrete MOSFETs.

On December 4, 1970, the twisted nematic field effect (TN) in liquid crystals was filed for patent by Hoffmann-LaRoche in Switzerland, (Swiss patent No. 532 261) with Wolfgang Helfrich and Martin Schadt (then working for the Central Research Laboratories) listed as inventors.Brown, Boveri & Cie, its joint venture partner at that time, which produced TN displays for wristwatches and other applications during the 1970s for the international markets including the Japanese electronics industry, which soon produced the first digital quartz wristwatches with TN-LCDs and numerous other products. James Fergason, while working with Sardari Arora and Alfred Saupe at Kent State University Liquid Crystal Institute, filed an identical patent in the United States on April 22, 1971.ILIXCO (now LXD Incorporated), produced LCDs based on the TN-effect, which soon superseded the poor-quality DSM types due to improvements of lower operating voltages and lower power consumption. Tetsuro Hama and Izuhiko Nishimura of Seiko received a US patent dated February 1971, for an electronic wristwatch incorporating a TN-LCD.

In 1972, the concept of the active-matrix thin-film transistor (TFT) liquid-crystal display panel was prototyped in the United States by T. Peter Brody"s team at Westinghouse, in Pittsburgh, Pennsylvania.Westinghouse Research Laboratories demonstrated the first thin-film-transistor liquid-crystal display (TFT LCD).high-resolution and high-quality electronic visual display devices use TFT-based active matrix displays.active-matrix liquid-crystal display (AM LCD) in 1974, and then Brody coined the term "active matrix" in 1975.

In 1972 North American Rockwell Microelectronics Corp introduced the use of DSM LCDs for calculators for marketing by Lloyds Electronics Inc, though these required an internal light source for illumination.Sharp Corporation followed with DSM LCDs for pocket-sized calculators in 1973Seiko and its first 6-digit TN-LCD quartz wristwatch, and Casio"s "Casiotron". Color LCDs based on Guest-Host interaction were invented by a team at RCA in 1968.TFT LCDs similar to the prototypes developed by a Westinghouse team in 1972 were patented in 1976 by a team at Sharp consisting of Fumiaki Funada, Masataka Matsuura, and Tomio Wada,

In 1983, researchers at Brown, Boveri & Cie (BBC) Research Center, Switzerland, invented the passive matrix-addressed LCDs. H. Amstutz et al. were listed as inventors in the corresponding patent applications filed in Switzerland on July 7, 1983, and October 28, 1983. Patents were granted in Switzerland CH 665491, Europe EP 0131216,

The first color LCD televisions were developed as handheld televisions in Japan. In 1980, Hattori Seiko"s R&D group began development on color LCD pocket televisions.Seiko Epson released the first LCD television, the Epson TV Watch, a wristwatch equipped with a small active-matrix LCD television.dot matrix TN-LCD in 1983.Citizen Watch,TFT LCD.computer monitors and LCD televisions.3LCD projection technology in the 1980s, and licensed it for use in projectors in 1988.compact, full-color LCD projector.

In 1990, under different titles, inventors conceived electro optical effects as alternatives to twisted nematic field effect LCDs (TN- and STN- LCDs). One approach was to use interdigital electrodes on one glass substrate only to produce an electric field essentially parallel to the glass substrates.Germany by Guenter Baur et al. and patented in various countries.Hitachi work out various practical details of the IPS technology to interconnect the thin-film transistor array as a matrix and to avoid undesirable stray fields in between pixels.

Hitachi also improved the viewing angle dependence further by optimizing the shape of the electrodes (Super IPS). NEC and Hitachi become early manufacturers of active-matrix addressed LCDs based on the IPS technology. This is a milestone for implementing large-screen LCDs having acceptable visual performance for flat-panel computer monitors and television screens. In 1996, Samsung developed the optical patterning technique that enables multi-domain LCD. Multi-domain and In Plane Switching subsequently remain the dominant LCD designs through 2006.South Korea and Taiwan,

In 2007 the image quality of LCD televisions surpassed the image quality of cathode-ray-tube-based (CRT) TVs.LCD TVs were projected to account 50% of the 200 million TVs to be shipped globally in 2006, according to Displaybank.Toshiba announced 2560 × 1600 pixels on a 6.1-inch (155 mm) LCD panel, suitable for use in a tablet computer,transparent and flexible, but they cannot emit light without a backlight like OLED and microLED, which are other technologies that can also be made flexible and transparent.

In 2016, Panasonic developed IPS LCDs with a contrast ratio of 1,000,000:1, rivaling OLEDs. This technology was later put into mass production as dual layer, dual panel or LMCL (Light Modulating Cell Layer) LCDs. The technology uses 2 liquid crystal layers instead of one, and may be used along with a mini-LED backlight and quantum dot sheets.

Since LCDs produce no light of their own, they require external light to produce a visible image.backlight. Active-matrix LCDs are almost always backlit.Transflective LCDs combine the features of a backlit transmissive display and a reflective display.

CCFL: The LCD panel is lit either by two cold cathode fluorescent lamps placed at opposite edges of the display or an array of parallel CCFLs behind larger displays. A diffuser (made of PMMA acrylic plastic, also known as a wave or light guide/guiding plateinverter to convert whatever DC voltage the device uses (usually 5 or 12 V) to ≈1000 V needed to light a CCFL.

EL-WLED: The LCD panel is lit by a row of white LEDs placed at one or more edges of the screen. A light diffuser (light guide plate, LGP) is then used to spread the light evenly across the whole display, similarly to edge-lit CCFL LCD backlights. The diffuser is made out of either PMMA plastic or special glass, PMMA is used in most cases because it is rugged, while special glass is used when the thickness of the LCD is of primary concern, because it doesn"t expand as much when heated or exposed to moisture, which allows LCDs to be just 5mm thick. Quantum dots may be placed on top of the diffuser as a quantum dot enhancement film (QDEF, in which case they need a layer to be protected from heat and humidity) or on the color filter of the LCD, replacing the resists that are normally used.

WLED array: The LCD panel is lit by a full array of white LEDs placed behind a diffuser behind the panel. LCDs that use this implementation will usually have the ability to dim or completely turn off the LEDs in the dark areas of the image being displayed, effectively increasing the contrast ratio of the display. The precision with which this can be done will depend on the number of dimming zones of the display. The more dimming zones, the more precise the dimming, with less obvious blooming artifacts which are visible as dark grey patches surrounded by the unlit areas of the LCD. As of 2012, this design gets most of its use from upscale, larger-screen LCD televisions.

RGB-LED array: Similar to the WLED array, except the panel is lit by a full array of RGB LEDs. While displays lit with white LEDs usually have a poorer color gamut than CCFL lit displays, panels lit with RGB LEDs have very wide color gamuts. This implementation is most popular on professional graphics editing LCDs. As of 2012, LCDs in this category usually cost more than $1000. As of 2016 the cost of this category has drastically reduced and such LCD televisions obtained same price levels as the former 28" (71 cm) CRT based categories.

Monochrome LEDs: such as red, green, yellow or blue LEDs are used in the small passive monochrome LCDs typically used in clocks, watches and small appliances.

Today, most LCD screens are being designed with an LED backlight instead of the traditional CCFL backlight, while that backlight is dynamically controlled with the video information (dynamic backlight control). The combination with the dynamic backlight control, invented by Philips researchers Douglas Stanton, Martinus Stroomer and Adrianus de Vaan, simultaneously increases the dynamic range of the display system (also marketed as HDR, high dynamic range television or FLAD, full-area local area dimming).

The LCD backlight systems are made highly efficient by applying optical films such as prismatic structure (prism sheet) to gain the light into the desired viewer directions and reflective polarizing films that recycle the polarized light that was formerly absorbed by the first polarizer of the LCD (invented by Philips researchers Adrianus de Vaan and Paulus Schaareman),

Due to the LCD layer that generates the desired high resolution images at flashing video speeds using very low power electronics in combination with LED based backlight technologies, LCD technology has become the dominant display technology for products such as televisions, desktop monitors, notebooks, tablets, smartphones and mobile phones. Although competing OLED technology is pushed to the market, such OLED displays do not feature the HDR capabilities like LCDs in combination with 2D LED backlight technologies have, reason why the annual market of such LCD-based products is still growing faster (in volume) than OLED-based products while the efficiency of LCDs (and products like portable computers, mobile phones and televisions) may even be further improved by preventing the light to be absorbed in the colour filters of the LCD.

A pink elastomeric connector mating an LCD panel to circuit board traces, shown next to a centimeter-scale ruler. The conductive and insulating layers in the black stripe are very small.

A standard television receiver screen, a modern LCD panel, has over six million pixels, and they are all individually powered by a wire network embedded in the screen. The fine wires, or pathways, form a grid with vertical wires across the whole screen on one side of the screen and horizontal wires across the whole screen on the other side of the screen. To this grid each pixel has a positive connection on one side and a negative connection on the other side. So the total amount of wires needed for a 1080p display is 3 x 1920 going vertically and 1080 going horizontally for a total of 6840 wires horizontally and vertically. That"s three for red, green and blue and 1920 columns of pixels for each color for a total of 5760 wires going vertically and 1080 rows of wires going horizontally. For a panel that is 28.8 inches (73 centimeters) wide, that means a wire density of 200 wires per inch along the horizontal edge.

The LCD panel is powered by LCD drivers that are carefully matched up with the edge of the LCD panel at the factory level. The drivers may be installed using several methods, the most common of which are COG (Chip-On-Glass) and TAB (Tape-automated bonding) These same principles apply also for smartphone screens that are much smaller than TV screens.anisotropic conductive film or, for lower densities, elastomeric connectors.

Monochrome and later color passive-matrix LCDs were standard in most early laptops (although a few used plasma displaysGame Boyactive-matrix became standard on all laptops. The commercially unsuccessful Macintosh Portable (released in 1989) was one of the first to use an active-matrix display (though still monochrome). Passive-matrix LCDs are still used in the 2010s for applications less demanding than laptop computers and TVs, such as inexpensive calculators. In particular, these are used on portable devices where less information content needs to be displayed, lowest power consumption (no backlight) and low cost are desired or readability in direct sunlight is needed.

A comparison between a blank passive-matrix display (top) and a blank active-matrix display (bottom). A passive-matrix display can be identified when the blank background is more grey in appearance than the crisper active-matrix display, fog appears on all edges of the screen, and while pictures appear to be fading on the screen.

Displays having a passive-matrix structure are employing Crosstalk between activated and non-activated pixels has to be handled properly by keeping the RMS voltage of non-activated pixels below the threshold voltage as discovered by Peter J. Wild in 1972,

STN LCDs have to be continuously refreshed by alternating pulsed voltages of one polarity during one frame and pulses of opposite polarity during the next frame. Individual pixels are addressed by the corresponding row and column circuits. This type of display is called response times and poor contrast are typical of passive-matrix addressed LCDs with too many pixels and driven according to the "Alt & Pleshko" drive scheme. Welzen and de Vaan also invented a non RMS drive scheme enabling to drive STN displays with video rates and enabling to show smooth moving video images on an STN display.

Bistable LCDs do not require continuous refreshing. Rewriting is only required for picture information changes. In 1984 HA van Sprang and AJSM de Vaan invented an STN type display that could be operated in a bistable mode, enabling extremely high resolution images up to 4000 lines or more using only low voltages.

High-resolution color displays, such as modern LCD computer monitors and televisions, use an active-matrix structure. A matrix of thin-film transistors (TFTs) is added to the electrodes in contact with the LC layer. Each pixel has its own dedicated transistor, allowing each column line to access one pixel. When a row line is selected, all of the column lines are connected to a row of pixels and voltages corresponding to the picture information are driven onto all of the column lines. The row line is then deactivated and the next row line is selected. All of the row lines are selected in sequence during a refresh operation. Active-matrix addressed displays look brighter and sharper than passive-matrix addressed displays of the same size, and generally have quicker response times, producing much better images. Sharp produces bistable reflective LCDs with a 1-bit SRAM cell per pixel that only requires small amounts of power to maintain an image.

Segment LCDs can also have color by using Field Sequential Color (FSC LCD). This kind of displays have a high speed passive segment LCD panel with an RGB backlight. The backlight quickly changes color, making it appear white to the naked eye. The LCD panel is synchronized with the backlight. For example, to make a segment appear red, the segment is only turned ON when the backlight is red, and to make a segment appear magenta, the segment is turned ON when the backlight is blue, and it continues to be ON while the backlight becomes red, and it turns OFF when the backlight becomes green. To make a segment appear black, the segment is always turned ON. An FSC LCD divides a color image into 3 images (one Red, one Green and one Blue) and it displays them in order. Due to persistence of vision, the 3 monochromatic images appear as one color image. An FSC LCD needs an LCD panel with a refresh rate of 180 Hz, and the response time is reduced to just 5 milliseconds when compared with normal STN LCD panels which have a response time of 16 milliseconds.

Samsung introduced UFB (Ultra Fine & Bright) displays back in 2002, utilized the super-birefringent effect. It has the luminance, color gamut, and most of the contrast of a TFT-LCD, but only consumes as much power as an STN display, according to Samsung. It was being used in a variety of Samsung cellular-telephone models produced until late 2006, when Samsung stopped producing UFB displays. UFB displays were also used in certain models of LG mobile phones.

Twisted nematic displays contain liquid crystals that twist and untwist at varying degrees to allow light to pass through. When no voltage is applied to a TN liquid crystal cell, polarized light passes through the 90-degrees twisted LC layer. In proportion to the voltage applied, the liquid crystals untwist changing the polarization and blocking the light"s path. By properly adjusting the level of the voltage almost any gray level or transmission can be achieved.

In-plane switching is an LCD technology that aligns the liquid crystals in a plane parallel to the glass substrates. In this method, the electrical field is applied through opposite electrodes on the same glass substrate, so that the liquid crystals can be reoriented (switched) essentially in the same plane, although fringe fields inhibit a homogeneous reorientation. This requires two transistors for each pixel instead of the single transistor needed for a standard thin-film transistor (TFT) display. The IPS technology is used in everything from televisions, computer monitors, and even wearable devices, especially almost all LCD smartphone panels are IPS/FFS mode. IPS displays belong to the LCD panel family screen types. The other two types are VA and TN. Before LG Enhanced IPS was introduced in 2001 by Hitachi as 17" monitor in Market, the additional transistors resulted in blocking more transmission area, thus requiring a brighter backlight and consuming more power, making this type of display less desirable for notebook computers. Panasonic Himeji G8.5 was using an enhanced version of IPS, also LGD in Korea, then currently the world biggest LCD panel manufacture BOE in China is also IPS/FFS mode TV panel.

In 2015 LG Display announced the implementation of a new technology called M+ which is the addition of white subpixel along with the regular RGB dots in their IPS panel technology.

Most of the new M+ technology was employed on 4K TV sets which led to a controversy after tests showed that the addition of a white sub pixel replacing the traditional RGB structure would reduce the resolution by around 25%. This means that a 4K TV cannot display the full UHD TV standard. The media and internet users later called this "RGBW" TVs because of the white sub pixel. Although LG Display has developed this technology for use in notebook display, outdoor and smartphones, it became more popular in the TV market because the announced 4K UHD resolution but still being incapable of achieving true UHD resolution defined by the CTA as 3840x2160 active pixels with 8-bit color. This negatively impacts the rendering of text, making it a bit fuzzier, which is especially noticeable when a TV is used as a PC monitor.

In 2011, LG claimed the smartphone LG Optimus Black (IPS LCD (LCD NOVA)) has the brightness up to 700 nits, while the competitor has only IPS LCD with 518 nits and double an active-matrix OLED (AMOLED) display with 305 nits. LG also claimed the NOVA display to be 50 percent more efficient than regular LCDs and to consume only 50 percent of the power of AMOLED displays when producing white on screen.

This pixel-layout is found in S-IPS LCDs. A chevron shape is used to widen the viewing cone (range of viewing directions with good contrast and low color shift).

Vertical-alignment displays are a form of LCDs in which the liquid crystals naturally align vertically to the glass substrates. When no voltage is applied, the liquid crystals remain perpendicular to the substrate, creating a black display between crossed polarizers. When voltage is applied, the liquid crystals shift to a tilted position, allowing light to pass through and create a gray-scale display depending on the amount of tilt generated by the electric field. It has a deeper-black background, a higher contrast ratio, a wider viewing angle, and better image quality at extreme temperatures than traditional twisted-nematic displays.

Blue phase mode LCDs have been shown as engineering samples early in 2008, but they are not in mass-production. The physics of blue phase mode LCDs suggest that very short switching times (≈1 ms) can be achieved, so time sequential color control can possibly be realized and expensive color filters would be obsolete.

Some LCD panels have defective transistors, causing permanently lit or unlit pixels which are commonly referred to as stuck pixels or dead pixels respectively. Unlike integrated circuits (ICs), LCD panels with a few defective transistors are usually still usable. Manufacturers" policies for the acceptable number of defective pixels vary greatly. At one point, Samsung held a zero-tolerance policy for LCD monitors sold in Korea.ISO 13406-2 standard.

Dead pixel policies are often hotly debated between manufacturers and customers. To regulate the acceptability of defects and to protect the end user, ISO released the ISO 13406-2 standard,ISO 9241, specifically ISO-9241-302, 303, 305, 307:2008 pixel defects. However, not every LCD manufacturer conforms to the ISO standard and the ISO standard is quite often interpreted in different ways. LCD panels are more likely to have defects than most ICs due to their larger size. For example, a 300 mm SVGA LCD has 8 defects and a 150 mm wafer has only 3 defects. However, 134 of the 137 dies on the wafer will be acceptable, whereas rejection of the whole LCD panel would be a 0% yield. In recent years, quality control has been improved. An SVGA LCD panel with 4 defective pixels is usually considered defective and customers can request an exchange for a new one.

Some manufacturers, notably in South Korea where some of the largest LCD panel manufacturers, such as LG, are located, now have a zero-defective-pixel guarantee, which is an extra screening process which can then determine "A"- and "B"-grade panels.clouding (or less commonly mura), which describes the uneven patches of changes in luminance. It is most visible in dark or black areas of displayed scenes.

The zenithal bistable device (ZBD), developed by Qinetiq (formerly DERA), can retain an image without power. The crystals may exist in one of two stable orientations ("black" and "white") and power is only required to change the image. ZBD Displays is a spin-off company from QinetiQ who manufactured both grayscale and color ZBD devices. Kent Displays has also developed a "no-power" display that uses polymer stabilized cholesteric liquid crystal (ChLCD). In 2009 Kent demonstrated the use of a ChLCD to cover the entire surface of a mobile phone, allowing it to change colors, and keep that color even when power is removed.

In 2004, researchers at the University of Oxford demonstrated two new types of zero-power bistable LCDs based on Zenithal bistable techniques.e.g., BiNem technology, are based mainly on the surface properties and need specific weak anchoring materials.

Resolution The resolution of an LCD is expressed by the number of columns and rows of pixels (e.g., 1024×768). Each pixel is usually composed 3 sub-pixels, a red, a green, and a blue one. This had been one of the few features of LCD performance that remained uniform among different designs. However, there are newer designs that share sub-pixels among pixels and add Quattron which attempt to efficiently increase the perceived resolution of a display without increasing the actual resolution, to mixed results.

Spatial performance: For a computer monitor or some other display that is being viewed from a very close distance, resolution is often expressed in terms of dot pitch or pixels per inch, which is consistent with the printing industry. Display density varies per application, with televisions generally having a low density for long-distance viewing and portable devices having a high density for close-range detail. The Viewing Angle of an LCD may be important depending on the display and its usage, the limitations of certain display technologies mean the display only displays accurately at certain angles.

Temporal performance: the temporal resolution of an LCD is how well it can display changing images, or the accuracy and the number of times per second the display draws the data it is being given. LCD pixels do not flash on/off between frames, so LCD monitors exhibit no refresh-induced flicker no matter how low the refresh rate.

Color performance: There are multiple terms to describe different aspects of color performance of a display. Color gamut is the range of colors that can be displayed, and color depth, which is the fineness with which the color range is divided. Color gamut is a relatively straight forward feature, but it is rarely discussed in marketing materials except at the professional level. Having a color range that exceeds the content being shown on the screen has no benefits, so