lcd display brightness control factory

Adjust the individual brightness of the LCD monitor"s R/G/B components. Overall brightness can be adjusted in the main menu → [DISPLAY SETUP] → [LCD SETTING] → [LCD BRIGHTNESS].ItemDescription of settings[R OFFSET]Adjusts the brightness of the LCD monitor"s R component.

For the video display developer LCD panels are available in many sizes and resolutions, they are also available with many choices of maximum brightness. The following considers the topic of LCD panel brightness, the choices, the methods for adjusting brightness and some brightness adjustment scenarios.

LCD panels are generally rated as to their maximum brightness level which is expressed in Nits, it is equal to Candela/sqm (cd/m2), and this will be at a particular color temperature as noted in the specification, usually 10,000 K. In terms of a practical understanding, the following is a rough guide:

Outdoor displays range from a low end of 700 nits to typically 1,000 or 1,500nits and up with 2,000~2,500nits and even up to 5,000nits seen with some models. This may include standard LCD panels, custom LCD panels as well as custom cut LCD panels.

Virtually all LCD panels have a LED backlight these days, these are powered by an LED driver board. Brightness control via the driver board will be by one of two methods:

PWM (Pulse Width Modulation): This varies the duty cycle of the backlight “on time” – it is predominant in modern LCD panel LED backlight designs to enable support for digital brightness controls.

Analog: Uses a simple variable voltage to adjust brightness, for example this might be a dial or slider type potentiometer / variable resistor. To see how to enable analog backlight adjustment visit: https://www.digitalview.com/blog/brightness-adjustment/

One of the advantages of LED for the backlight is the range of adjustment that is possible, however it is important to note that the range varies significantly from model to model. Some industrial panels can be turned to very low light levels making them suitable for use in special environments such as at night. Lower cost panels limit the range of brightness to what might be required for typical usage, whereas panels with full range dimming from full off to full on require more complex backlight drivers.

Backlight lifetime: Many LCD panels have a backlight lifetime rating of 50,000 hours (typically measured to half brightness), this can be extended by running the LED backlight at a lower brightness level. Some panels may only offer 30,000 hours as a lower cost solution while other panels may offer up to 100,000 hours for high end applications.

An LCD panel backlight may be constructed so the LED’s are mounted directly behind a light guide diffuser, or they may be mounted along one or more edges of the light guide.

Active backlight: This is a function of some LCD panel backlights to automatically adjust the backlight brightness in response to the image. For more advanced systems there is an LED array making up the LED backlight, this adjusts the brightness in areas localized to the image being shown. This can greatly enhance the brightness across the display and is being used primarily with video, for example on consumer TV sets. It is not useful to all image types, for example a spreadsheet or content like maps or data is not likely to benefit.

Local dimming: Some LCD panels with direct LED may support local dimming so the LED’s are dimmed in response to the image close to them. This will not be at the same resolution as the LCD panel itself but will help greater contrast over the display by enhancing the brightness in bright areas of the image and darkening the image in dark parts of the image.

For the LCD monitor manufacturer it is important to consider that any covering over the LCD panel will reduce the brightness. For example the protective glass over a digital signage display, or a touch screen, or a semi-silvered mirror. So if a specific brightness is required the measurement should be taken with these in place.

There are various relatively low cost brightness meters available, typically in the couple of hundred dollars range. It is difficult to comment on the accuracy of these but we have found them to be within 5% of each other, though more importantly they do appear to be quite consistent in measurement so good for measurement comparisons. For more accurate measurement there are light meters from companies such as Minolta that can be calibrated, the cost may run into several thousand dollars.

Examples of light meters costing a few hundred dollars include SpyderX by Datacolor (needs a PC), a handheld meter is the SM208 by Sanpometer (search SM208 meter). Note: Many light meters, including smartphone apps, will be meters used for photography and not give readings in nits (or candelas). LCD panel specifications are typically measured using nits.

PWM and Analog: Most Digital View LCD controllers support PWM and Analog as a method for adjusting the backlight brightness level (this is noted in the column headed “Other” on the controller board summary table: https://www.digitalview.com/controllers/lcd-controllers-home.html. Also see https://www.digitalview.com/blog/brightness-adjustment/ for a guide to using a dial or slider type variable resistor to adjust the backlight.

DPMS (Display Power Management System): The backlight will be automatically turned off after a period if there is no valid video signal being received.

Ambient light sensor: The backlight is adjusted for brightness or powered off depending on ambient light conditions. This uses a light sensor attached to the LCD controller board, see https://www.digitalview.com/blog/light-sensor-app-note/ for more details.

The specifics of the backlight control are documented separately for each LCD controller model (product summary here) in the product manual available for download on the product page.

Note: There are two ways to adjust the perceived brightness of a LCD panel or LCD monitor, the backlight and the black-level. Very often, particularly in the past, the monitor brightness setting adjusted the black-level, this adjusts the LCD but not the backlight.

Color, color temperature etc: In addition to adjusting the brightness other settings may be adjusted as well. For example the color temperature or for example a switch to green monochrome for night vision.

Night-safe lighting (update) : Dual-rail backlights can also be supported. These special backlight enable normal brightness and extreme low level brightness with custom night-safe lighting. Contact us for details.

Note: We have a blog on methods for implementing an ambient light sensor with Digital View LCD controller boards to automatically adjust the backlight or system power, see: Ambient Light Sensor

Update March 2019: Most of the above remains unchanged except for the increased availability of high bright LCD panels of around the 1,000 nit to 2,500 nit range. AUO for example has a number of large size LCD panels with 1,500 nit brightness for the digital signage market. Tianma has panels under 20″ with 1,000 nit to 1,500 nit brightness for various outdoor applications.

The other change is that high bright panels are now increasing edge-lit, this makes the panels thinner and these panels tend to use less power than the previous models. One of the benefits for monitor designers is easier heat management and reduced overall display system costs.

The invention relates generally to liquid crystal displays (LCDs) and, more particularly, to a system for automatically adjusting the brightness of an LCD responsive to the amount of ambient light available during operation thereof.

Liquid crystal displays (LCDs) are used in portable personal computers (PCs) and other electronic devices to display information. LCDs modulate light to create images using selectively transmissive and opaque portions of the display, the selection being controlled by passing electrical current through the liquid crystal material Transmissive-type LCDs are illuminated by an artificial backlight positioned behind the LCD glass to provide the contrast between the light transmissive and opaque portions of the display.

The LCD backlight is one of the primary sources of power consumption in a portable PC and the power consumed by the backlight is directly related to the brightness level selected. Therefore, it would be advantageous, from a power consumption standpoint, to operate the PC with the LCD at the lowest possible brightness level at which the contents of the display can still be seen by the user. For example, in a particular portable PC model available from Dell Computer Corporation of Austin, Tex., operating the PC with the LCD set to the minimum brightness level as compared to the maximum brightness level, can reduce overall power consumption of the PC by approximately twenty percent (20%), which in turn increases the runtime of the PC between battery charges by the same percentage. Specifically, assuming that in the example just described the PC has a typical runtime between battery charges of 8 hours with the LCD set to the maximum brightness level, decreasing the brightness level to the minimum level will increase the runtime of the PC to 9.6 hours.

In view of the foregoing, it is apparent that a user could significantly increase the runtime between battery charges of his or her portable PC by taking advantage of ambient lighting conditions that increase the visibility of the LCD, that is, low ambient light, and decreasing the brightness level of the LCD whenever the PC is being operated in such lighting conditions. Specifically, it is obvious that the contents of an LCD can be much more easily viewed in a dark room than a bright one. Hence, a user could take advantage of that fact by decreasing the brightness level of the LCD whenever ambient lighting conditions permit and then subsequently increasing the brightness level only when necessitated by bright ambient lighting conditions.

While foregoing manual brightness adjustment presents a viable option for increasing the runtime of a PC between charges, it is deficient in certain respects. In particular, while a user may begin by operating the PC with the LCD brightness set to the minimum level necessary to enable the contents of the display to be perceived, after a user has moved with the PC to an environment in which the ambient lighting conditions require that the LCD be set to the maximum brightness level, the user will typically forget to decrease the brightness level upon returning to an environment in which the ambient lighting conditions would be conducive to such a decrease. As a result, the power savings are not as substantial as might be the case were the brightness adjustment to occur automatically.

Accordingly, what is needed is an intelligent LCD brightness control system which automatically adjusts to the ambient lighting conditions of the environment in which the PC is being used.

The foregoing problems are solved and a technical advance is achieved by method and apparatus for automatically adjusting the brightness level of an LCD based on the ambient lighting conditions of the environment in which the LCD is being operated. In a departure from the art, a photodetector located proximate the front of the LCD generates to brightness control circuitry signals indicative of ambient lighting conditions. These signals are correlated to automatic brightness control values for use in controlling the output of the backlight driver circuit which determines the brightness level of the LCD.

In one embodiment of the present invention, signals indicative of a user-selected brightness level are also input to the brightness control circuitry and taken into account in to the adjustment of the brightness level of the LCD. In one aspect of the invention, once the ambient signals have been used automatically to set the brightness level of the LCD, subsequent user-selection of a different brightness level, either higher or lower, will override the automatic brightness control setting.

In an alternative embodiment, a first photodetector is located proximate the front of the LCD and a second photodetector is located proximate the back of the LCD. In this embodiment, the brighter ambient condition is used to control the brightness level of the LCD. This embodiment is especially usefull in situations in which light is directed toward the back of the LCD, and hence toward the user"s eyes, which light, while affecting the visibility of the LCD, might not be detected by the first photodetector.

In another alternative embodiment, the brightness control circuitry comprises some form of artificial intelligence for "learning" a user"s preferred brightness level, or range of brightness levels, in various ambient lighting conditions.

A technical advantage achieved with the invention is that it provides increased run-time between battery charges by lowering the brightness level of an LCD during use in low ambient lighting conditions.

Another technical advantage achieved with the invention is that the adjustment of the brightness level occurs automatically without user intervention, thereby reducing the possibility that a user may set the brightness level at a maxium level during use in high ambient lighting conditions and subsequently neglect to lower the level upon returning to a low ambient lighting condition.

Another technical advantage achieved with the invention is that, in at least one embodiment, the user may override the automatic brightness control setting using a conventional LCD brightness control means.

Yet another technical advantage achieved with the invention is that the brightness control circuitry can be configured to "learn" a user"s preferred brightness settings in various ambient lighting conditions, thereby obviating the need for the user to readjust the brightness level and override the automatic brightness control setting each time such ambient lighting conditions are entered.

FIG. 5 is a flowchart of the operation of brightness control circuitry for implementing an alternative embodiment of the method of the present invention.

FIG. 1 illustrates a portable personal computer (PC) 10 embodying features of the present invention and comprising a base 11 including a keyboard 11a, a liquid crystal display panel (LCD) 12 disposed in a lid portion 13 of the PC 10, and at least one photodetector or light sensor 14 disposed on the same side of the lid portion 13 proximate the LCD 12, for detecting a level of ambient light directed toward the front of the LCD 12 and for generating signals indicative of same. A user-selected brightness control level may be input via conventional methods and stored in a nonvolatile memory device, as shown in FIG. 2, for enabling the user manually to adjust the brightness level of the LCD 12.

FIG. 2 is a system block diagram of the PC 10 of FIG. 1. As shown in FIG. 2, the PC 10 comprises a CPU 200, system RAM 202, brightness control circuitry 204, and other I/O devices 206, including the keyboard 11a (FIG. 1), electrically interconnected via a bus 208. In the preferred embodiment, the brightness control circuitry comprises a microprocessor 204a, memory 204b, and an analog-to-digital ("A/D") converter 204c for purposes that will subsequently be described in detail.

An output of the microprocessor 204a is electrically connected to the Backlight driver circuitry 213 in a conventional manner for generating brightness control or "BC," signals thereto via a line 210 for controlling the brightness level of the LCD 12 at any given time. In addition, analog signals generated by the photodetector 14 indicative of the level of ambient light striking the front of the LCD 12 (hereinafter "ambient light" or "AL" signals), as well as a digital signal indicative of the brightness level selected by the user (hereinafter "user-selected brightness level" or "USBL" signal) and stored in a nonvolatile memory device, such as NVRAM 211, are input to the brightness control circuitry 204 on lines 212, 214, respectively. The analog AL signals are converted to digital signals by the analog-to-digital converter 204c and then input to the microprocessor 204a.

A plurality of automatic brightness level ("ABL") signal values, each of which corresponds to a particular one of a plurality of various possible AL signal values, are stored in the memory 204b. It will be understood that the ABL signal value associated with each of the AL signal values will be determined empirically and will depend, at least partially, on the relevant parameters of the particular LCD 12, as well as a subjective determination of the optimum LCD brightness level for operation in the given ambient lighting condition. In one embodiment, the ABL signal values are stored in the memory 204b as a lookup table indexed by the input AL signal value, such that input of an AL signal thereto via the microprocessor 204a results in the output therefrom of the corresponding ABL signal, although various other manners of implementation are anticipated. In any event, once the microprocessor 204a accesses from the memory 204b the ABL signal value corresponding to the AL signal input thereto, it outputs to the Backlight driver circuitry 213 an appropriate BC signal for adjusting the brightness level of the LCD 12 in accordance with the levels indicated by the USBL and AL signals, as will be described in detail with reference to FIG. 3.

FIG. 3 is a flowchart of the operation of the brightness control circuitry 204 for inplementing the preferred embodiment of the present invention. It should be understood that instructions for execution by the microprocessor 204a for inplemnenting the invention are preferably stored in memory 204b. Execution begins in step 300 when the LCD 12 is turned on. In step 302, after the analog AL signal generated by the photodetector 14 has been converted to a digital signal by the A/D converter 204c and input to the microprocessor 204a, it is used to index the ABL signal lookup table (not shown) stored in the memory 204b. Also in step 302, the BC signals output to the backlight driver circuitry 213 for controlling the brightness level of the LCD 12 is set to correspond to the ABL signal indexed by the AL signal In this manner, the brightness level of the LCD 12 is adjusted according to the current ambient lighting conditions in which the PC 10 is being operated. It should be understood that, alternatively, upon power up of the LCD 12, the BC signal may initially be set to equal the value of USBL as stored in the NVRAM 211, such that the brightness level of the LCD 12 is set to correspond to the previous user-selected level, rather than the ambient lighting conditions.

In step 304, a determination is made whether the AL signal has changed, indicating that the ambient lighting conditions have changed. If so, execution proceeds to step 306. In step 306, the new AL signal is again used to index the ABL signal lookup table (not shown) stored in the memory 204b. Also in step 306, the BC signals output to the backlight driver circuitry 213 for controlling the brightness level of the LCD 12 is set to correspond to the ABL signal indexed by the AL signal thereby adjusting the brightness level of the LCD 12 according to the new ambient lighting conditions. Execution then proceeds to step 308. Similarly, if in step 304, it is determined that the AL signal has not changed, indicating that no adjustment for ambient lighting conditions is necessary, execution proceeds directly to step 308.

In step 308, a determination is made whether the USBL signal has changed. If the USBL signal has not changed, execution returns to step 304. In contrast, if the USBL signal has changed, indicating that the user has attempted to manually change the brightness level of the LCD 12, execution proceeds to step 310. In step 310, the BC signal output to the backlight driver circuitry 213 is set to correspond to the USBL signal. Once the brightness of the LCD 12 has been set to the level indicated by the USBL signal in step 310, execution returns to step 304.

In this manner, the brightness control circuitry 204 ensures that the brightness level of the LCD 12 is always automatically set to the level dictated by the current ambient lighting conditions, unless the user selects a different brightness level subsequent to a change in the ambient lighting conditions, in which case the level selected by the user is used to control the brightness level of the LCD 12. As a power saving measure, an additional step could be added in which a comparison is made between the level of the AL and USBL signals and, responsive to the comparison, the brightness level of the LCD 12 is dictated by the lower (ie., dimmer) of the two signals. It should be noted, however, that this may result in a situation in which the LCD 12 cannot be read, for example, where a user moves from low to high ambient lighting conditions without manually readjusting the brightness setting.

FIG. 4 is a rear perspective view of a portable PC 10" embodying features of an alternative embodiment of the present invention. In particular, in addition to comprising all of the same features of the PC 10 shown in FIG. 1, including a base 11", a keyboard 11a", an LCD 12" disposed in a lid 13", a first photodetector 14" and a user-actuatable brightness control means (not shown), the PC 10" further comprises a second photodetector 410 disposed on the opposite side of the lid 13" as the LCD 12" and first photodetector 14", for detecting ambient light directed toward the back side of the LCD 12" and toward a user"s eyes.

In the alternative embodiment, the greater of an AL signal generated by the photodetector 14" and an AL signal generated by the photodetector 410 is used to index the lookup table comprising ABL signal values, as described with reference to FIGS. 2 and 3. In this manner, the brighter ambient lighting condition is used to determine the ABL signal value for use in adjusting the brightness level of the LCD 12". It will be apparent that, with this alternative embodiment, the user is insured that the contents of the LCD 12" will be visible where, for example, the area behind the LCD 12" is highly illuminated, but the area in front of the LCD 12" is not. This might not be the case absent the second photodetector 410 as shown in FIG. 4, the brightness level of the LCD 12" would most likely be set too low for the user comfortably to view the contents thereof. Alternatively, a weighted average of the AL signals generated by the photodetectors 14" and 410, as computed by the microprocessor 402a, could be used to index the lookup table.

In another alternative embodiment of the invention, as described with reference to FIGS. 2 and 5, the brightness control circuitry 204 comprises some form of artificial intelligence designed to adjust the lookup table ABL entries stored in the memory 204b according to current and previous USBL signals generated in response to a particular detected ambient lighting conditions. In this manner, the brightness control circuitry 204 "learns" the users preferred settings for particular lighting conditions, thereby minimizing the number of times the user must manually adjust the brightness level to override the automatic settings.

Referring to FIG. 5, execution begins in step 500 when the LCD 12 is turned on. In step 502, once the analog AL signal generated by the photodetector 14 is converted to a digital signal by the A/D converter 204c and input to the microprocessor 204a, it is used to index the ABL signal lookup table (not shown) stored in the memory 204b. Also in step 502, the BC signal output to the backlight driver circuitry 213 for controlling the brightness level of the LCD 12 is set to correspond to the ABL signal indexed by the AL signal, thereby adjusting the brightness level of the LCD 12 according to the current ambient lighting conditions. Again, it should be understood that upon power up of the LCD 12, the BC signal may initially be set to correspond to the value of USBL as stored in the NVRAM 211, rather than the value of the AL signal.

In step 504, a determination is made whether the AL signal has changed, indicating that the ambient lighting conditions have changed. If so, execution proceeds to step 506. In step 506, the new AL signal is used to index the ABL signal lookup table (not shown) stored in the memory 204b. Also in step 506, the BC signal output to the backlight driver circuitry 213 for controlling the brightness level of the LCD 12 is set to correspond to the ABL signal indexed by the new AL signal, thereby adjusting the brightness level of the LCD 12 according to the current ambient lighting conditions. Execution then proceeds to step 508. Similarly, if in step 504, it is determined that the AL signal has not changed, indicating that no adjustment for ambient lighting conditions is necessary, execution proceeds directly to step 508.

In step 508, a determination is made whether the USBL signal has changed. If the USBL signal has not changed, execution returns to step 504. In contrast, if the USBL signal has changed, indicating that the user has attempted to manually change the brightness level of the LCD 12, execution proceeds to step 509. In step 509, the lookup table entry corresponding to the current AL is adjusted according to the present USBL. In addition, previous USBL signals generated when the present ambient lighting condition is encountered are also preferably taken into account during the adjustment. Once the lookup table entry has been adjusted, execution proceeds to step 510. In step 510, the BC signal output to the backlight driver circuitry 213 is set to correspond to the USBL signal. Once the brightness of the LCD 12 has been set to the level indicated by the USBL signal in step 510, execution returns to step 504.

In this manner, the brightness control circuitry 204 is able to take into account the user"s preferences with respect to preferred brightness control settings in particular ambient lighting conditions. In the preferred embodiment, the method illustrated in FIG. 5 is designed to constantly attempt to converge on the user"s preferred setting for each range of ambient lighting conditions, thereby minimizing the necessity that the user will need to manually adjust the LCD 12 brightness setting.

It is understood that the present invention can take many forms and embodiments. The embodiments shown herein are intended to illustrate rather than to limit the invention, it being appreciated that variations may be made without departing from the spirit or the scope of the invention. For example, the LCD brightness control circuitry 204 could comprise some form of artificial intelligence, e.g., a neural network, for "learning" the user"s preferred brightness settings in various ambient lighting conditions, as indicated by the control means setting, such that when the settings are later re-encountered, the LCD 12 will be automatically adjusted to the user"s preferred brightness setting. Alternatively, the brightness control circuitry 204 could be simplified to provide a direct linear control signal of measured light to LCD brightness level, thus eliminating the need for the A/D converter 204c and microprocessor 204a.

Starting firmware version 3.9.0, for the Original Prusa MK3S manufactured after June 2019, it is possible to adjust the brightness of the screen directly from the LCD menu and also have the option of dynamic lighting, triggered by navigating the LCD menu.

Printers received before June 2019 including the MK3 model may not have the compatible components for this feature. EinsyRambo rev. 1.1a, and an LCD panel supplied after June 2019 is required. These can be purchased in our eshop (note that you have to be logged in).

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NOTE: Before adjusting the monitor, ensure it has been running for at least 20 minutes to allow the brightness and contrast levels to stabilize. The exact steps to perform the steps will vary from model to model, see the user manual of the Dell monitor.

Locate the button on the monitor that activates the On-Screen Display (OSD) menu. To learn how to navigate the on-screen display menu, see the user manual of the Dell monitor.

As you adjust the Brightness and Contrast settings, you will see the screen change as a result. Continue adjusting until you reach the desired brightness and contrast levels.

Locate the button on the monitor that activates the On-Screen Display (OSD) menu. To learn how to navigate the on-screen display menu, see the user manual of the Dell monitor.

Adjust the brightness and contrast settings using the On-Screen Display (OSD) menu. To learn how to navigate the on-screen display menu, see the user manual of the Dell monitor.

Note: Ensure to set your LCD panel to factory settings at this point. Otherwise, you will not get the best results. To reset your LCD panel to factory conditions, use the buttons that are located on the front, side, or back. However, if your LCD panel lets you set the gamma, you should set it to 2.2 or as close as possible.

Next, use the slider to adjust the gamma. To do this, move the slider until the dots in the middle of the image appear less visible. This changes both the brightness and color of your screen.

Note: Do not worry if you cannot make the circles in the center completely disappear. If you want a better way of testing, you can also use this gamma correction test image. Try to make as many numbers appear on the top and bottom bars as possible. With better LCD panel s, you can see 6 numbers in each bar, while lower-grade LCD panel s will only be able to show 4 numbers.

Note: If you cannot adjust the slider, you might have to change the gamma settings by using your LCD panel ’s controls. You should still keep the display settings window and gamma correction image test open while you do this.

Next, adjust the brightness. To do this, use the control buttons on your LCD panel until you can see the shirt and suit in the image, but not so much that the X stands out from the background. You should still be able to see the "X," but the wall behind it should not be washed out.

Note: Your screen looks different depending on what angle you are looking at it. For the best results, you should step back and look at your LCD panel from far away.

Next, adjust the contrast. To do this, use the buttons on your LCD panel. You want to set your contrast so you can just see the wrinkles and buttons on the shirt of the man in the figure. The background of the image should not be bright white.

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, calculators, and mobile telephones, including smartphones. LCD screens have replaced heavy, bulky and less energy-efficient cathode-ray tube (CRT) displays in nearly all applications. The phosphors used in CRTs make them vulnerable to 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 do not have this weakness, but are still susceptible to image persistence.

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 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,

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),

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