distinguish between crt and lcd monitors made in china

CRT stands for Cathode Ray Tube and LCD stands for Liquid Crystal Display area unit the kinds of display devices wherever CRT is employed as standard display devices whereas LCD is more modern technology. These area unit primarily differentiated supported the fabric they’re made from and dealing mechanism, however, each area unit alleged to perform identical perform of providing a visible variety of electronic media. Here, the crucial operational distinction is that the CRT integrates the 2 processes lightweight generation and lightweight modulation and it’s additionally managed by one set of elements. Conversely, the LCD isolates the 2 processes kind one another that’s lightweight generation and modulation.

CRT and LCD are both display devices. CRT is an old technology whereas LCD is modern one. One major difference between CRT and LCD is in the technology used for image formation. The CRT display produces an image by using an electron beam, while LCD display produces an image on the screen using liquid crystal display.

CRT stands for Cathode Ray Tube. CRT displays produce an image on the screen by using a sharp beam of electrons that is highly focused to hit a phosphor screen present in front of the tube. The important components of a CRT are electron gun, focusing mechanism, and phosphor screen.

CRT was used in earlier TVs and computer monitors. CRT produces poor quality images on the screen and also consumes large electricity. The lifespan of CRT displays is very short. Because of all reasons, CRTs are being replaced by other display technologies these days.

LCD stands for Liquid Crystal Display. In LCD, liquid crystals are used to produce images on the screen. LCD displays are thin and more energy efficient, thus they are used in several small sized devices like mobiles, laptops, TVs, desktop computer monitors, calculators, etc.

In LCDs, light is obtained from external sources, and then it is converted into a definite graphics pattern using optical effects. LCDs have several advantages over CRT such as less power consumption, faster response, smaller size, low cost, etc.

Both CRT and LCD have their own advantages and disadvantages. However, these days, CRTs have almost become extinct. No one seems to be using them anymore. LCDs and other display technologies have replaced them because the new devices are highly efficient in terms of cost, power, and performance.

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Are LED monitors better than their LCD predecessors? How are the two technologies differ in terms of functionality and performance? All these questions will be answered by the LED vs. LCD comparison presented in here.

The age of CRT (cathode ray tube) displays is over and LCD displays are already being replaced with LED screens. Technology is evolving at an exponential pace, pushing existing technologies into obsolescence. Just when we thought LCD screens will be the default choice for some time to come, they were supplanted by LED monitors, with their superior power efficiency and rich picture quality.

Considering that we spend a major amount of our lifetime in front of screens these days and eyes are not a replaceable commodity, a discerning consumer must opt for technology that is soft on the eyes, while providing a rich visual experience.

There seems to be a lot of confusion about the differences between LED (Light Emitting Diode) and LCD (Liquid Crystal Display) monitors that need clarification. Here"s a succinct analysis of the similarities and differences between the two models.

LED and LCD monitors are based on the same basic technology for image display but differ in the kind of backlighting used. While LCD monitors use CCFL (cold cathode fluorescent lamps) for backlighting, the latter use light-emitting diodes. This is the prime difference between the two display technologies. So LED monitors are in actuality, a type of LCD monitors or an improvement over them.

Unlike CRT monitors that generate their own light through cathode ray incidence on fluorescent materials, LCD displays have to rely on external lighting, as their display is created through manipulation of light, passing through polarized liquid crystals. Backlighting affects picture quality substantially and light shed by LEDs offers superior picture quality compared to LCDs.

This is because LEDs offer much more gradation in intensity and a larger light wavelength spectrum, providing a truer color quality. These types of monitors offer a better dynamic contrast ratio as well. So if you compare LED and LCD monitors from a gaming perspective and for use in intensive graphic applications, LED monitors are surely better choices. They provide vivid and more lifelike colors, with better gradation.

LED monitors cure one of the basic problems with LCD TVs, which is the inability to display true black colors. They can produce true black hues, by switching off LEDs entirely, increasing the blackness quotient of the screen, and providing better contrast in the process.

LED monitors are a very recently introduced technology and they are preferred over LCD monitors because of the amazingly rich picture quality and viewing comfort. One more advantage that LED monitors to have over LCD ones is the power consumption factor. LED monitors require a lot less power to operate than cold cathode fluorescent lamps. This property can be attributed to the inherently low energy required by an LED to function. Their power consumption is as much as 40% lesser than conventional LCD monitors.

LED monitors are also a lot softer on the eyes than LCD monitors, making them popular choices for people who work for long hours on their desktop computers. They are also a lot more eco-friendly because mercury is not used in their production. LEDs last longer than cold cathode fluorescent lamps, with little reduction in their power output over time, which makes these monitors long-lasting.

To conclude this LCD vs. LED monitor comparison, let us compare the price ranges. One major factor that has been holding back LED technology from reaching the masses is the high price factor. The manufacturing of these devices is a bit costlier currently, compared to LCD displays which have raised their overall price. However, the cost gap is slowly lowering with time, as the demand for superior LED back-lit displays is on the rise all over the world. Even laptop computers and now smartphones come equipped with LED displays. While some of the best LCD monitors are available for a price of around $100, the best LED monitors fall in the $150 to $200+ range.

First, we will provide a brief technical overview of functional principles as they relate to visual stimulus presentation. Detailed descriptions and parameter measurements are already available from the existing literature; however, our intention here is to equip readers with limited technical expertise with the necessary knowledge to set up computer experiments with LCD monitors. Thus, we keep our explanations relatively short and simplified.

LCD monitors work differently: Each pixel consists of liquid crystal threads that can be twisted or arranged in parallel by an electrical current applied to them. This leads to a polarization effect that either allows or prevents light passing through. A white light source located behind this crystal array uniformly and constantly illuminates the array. To display a black pixel, the crystal threads are twisted by 90° such that no light will pass through. A white pixel is achieved by aligning the crystals such that maximum light is allowed to pass through, until a different, non-white color needs to be displayed (see the lower panel of Fig. 1 for an LCD pixel’s brightness over time). This is a static process, not a pulsed one as in CRTs.

In theory, the difference in presentation methods, namely a strobing versus a static image, should be of no consequence if the light energy that falls onto the retina remains the same over the time period of one single frame. As the Talbot-Plateau law states2 is equally well detectable as a light flash presented for 60 ms at 40 cd/m2. This suggests that temporal integration can be easily described by energy summation”. Thus, in principle, LCD and CRT monitors should be able to yield comparable results.

However, due to the differences in technology, the visual signals produced by the two display types have different shapes (i.e., a different light energy-over-time-curve; see Fig. 1). Moreover, default luminance as well as visual-signal response times (in addition to other parameters, see below) differ between most CRT and LCD monitors

Table 1 reports the parameters we considered in setting up the CRT and LCD monitors. Certainly, most of them are commonly considered when setting up a computer experiment; nevertheless we deemed it important to mention them here explicitly, as their neglect might have unintended consequences. We used a 17” Fujitsu Siemens Scenicview P796-2 CRT color monitor previously used in several published studies including studies with masked presentation conditions

We tested various monitor user settings, refresh rates, resolutions and luminance settings (see materials available at https://osf.io/g842s/) with regard to the emitted light energy–over-time-curve and therefore response characteristics (i.e., onset and offset of full screen and centrally presented stimuli). Measurements were conducted with a photodiode setup, using both an oscilloscope (model “Agilent MSOX 3012 A”) and a self-developed microcontroller setup as measurement devices. Stimuli were black and white squares.

Our measurements revealed several interesting characteristics: First, luminance of the LCD monitor at default setting (i.e., maximum brightness) exceeded the CRT luminance at a ratio of 3.25:1. However, comparable average luminance can be (and was) achieved by downregulating the LCD monitor (the older CRT technology emits less energy even at maximum settings, see Table 2), without participants perceiving it as unnaturally dark. If one plans to upgrade from CRT to LCD monitors in an experimental laboratory, we therefore recommend measuring the CRT monitors’ brightness levels and matching them in the new LCD monitors’ user setup, if comparability with the old setup is needed. This will minimize hardware-dependent variability, thus contributing to better replicability. Please note that a brightness adaption is not a necessary precondition when employing LCD monitors; researchers should simply be aware that the brightness level can have an influence onto the resulting effects, especially in time-critical experiments with short and/or masked presentation. Thus, we recommend the adaptation for time-critical experiments in which researchers orient on existing empirical evidence gathered with CRT monitors. Furthermore, gray-to-gray response times varied slightly depending on the employed brightness levels2), so we suggest that researchers can rely on this more efficient method as an approximation.

For the empirical comparison of human performance with CRT and LCD monitors, we relied on these results and set the monitor settings accordingly (see Method section below).

Participants were administered a masked number priming task and a subsequent forced-choice prime discrimination task using both a CRT and an LCD monitor. In this well-established paradigm

Of central interest was the question whether both monitors would yield comparable masked priming effects. Monitors were set according to the parameters described in the previous section (see also Method section below). In order to obtain conclusive evidence, we decided for sequential hypothesis testing using Bayes factorshttps://osf.io/g842s/.

Distinguish, differentiate, compare and explain what is the differences between CRT and LCD Monitor. Comparison and Difference. As the technology has improved and the prices have come down, LCD (Liquid Crystal Display) monitors have rapidly been replacing CRT (Cathode Ray Tube) monitors on desktops around the world. ComputerWorld first reported that LCD sales would surpass CRT sales for the first time in 2003, a lead that it didnt hold for good. But according to DisplaySearch, a flat panel display market research and consulting company, the sales of LCD monitors regained the lead over CRT sales in the third quarter of 2004, a lead that it should eventually hold for good.

Direct exposure of bare skin to strong light after PDT can cause severe skin phototoxicity although the superficial light irradiation has a limited tissue penetration depth. Therefore, the patient is advised to avoid direct light exposure to the skin after the administration of the photosensitizer. The length of light avoidance after PDT depends on the retention time of photosensitizer in the normal skin, which can be affected by the nature and dose of photosensitizer and its administration route, and body site [

Incidences of post-PDT skin phototoxicity are often associated with patients who fail to heed the advice of strict light avoidance. Rather than indoor light, sunlight exposure shortly after receiving an exogenous photosensitizer or prodrug presents a major risk factor for skin phototoxicity. Although rare, exposure to CRT or LCD monitor emissions after PDT can also cause cutaneous phototoxicity on bare skin [

Color CRT monitors use a phosphor-coated screen. Phosphors are arranged in strips and emit visible light when exposed to an electron beam generated within the CRT. Three beams are used in CRT monitors to excite red, green, and blue color in combinations needed to create the various hues that form the picture. CRT monitors are gradually being replaced by LCD flat panel monitors in households and offices. The light emitting mechanism of LCD monitors is different than that of CRTs. LCD displays use two basic techniques for producing color: passive matrix or thin film transistor. Basically, LCD monitors utilize two sheets of polarizing material with a segmented liquid crystal solution between them. An electric current passes through the liquid causing the crystals to align so that the light emission of individual pixels can be controlled. LCD monitors are typically backlit by a white light fluorescent (fluorescent-backlit) or LED light (LED-backlit) source since the liquid crystals generate no light of their own.

This study examined the light emission profiles of common CRT, LCD, and LED monitors utilizing simulated movie and video game streams. The range of optical irradiance generated from the movie stream was broader than that from the game stream (see Fig. 2). The 50% points of the cumulative ratio for the game were slightly higher than that of the movie (see Fig. 3). Using a representative figure of 1 μW/cm2 as an example, it can be estimated that 10 min exposure to a monitor at a distance of 18 in. can deliver a total fluence of 0.6 mJ/cm2, i.e., 60 μJ/cm2/min to the skin surface. This estimated fluence rate is considerably lower than that of sunlight or PDT light, which are typically at 101–102 mW/cm2 range. The moderate monitor settings (e.g., the total emission intensity of 6:5 μW/cm2 at the measurement point), randomly selected video streams, and longer sensor-to-monitor distance (e.g., 18 in.) might cause an underestimate of the fluence rate. It should be noted that the actual light emission profiles depend on several factors, including the size and configuration of monitor screen, program being played back on the screen, and its duration. The light fluence received by the skin is also affected by the screen-to-face distance and their alignment. Furthermore, the light fluence inside the skin of a multilayered geometry can be significantly affected not only by light source but also by tissue optical properties [

For 10 min of the movie or game the integrated fluence from the CRT’s visible emission (467.5–800 nm) measured by the spectrometer at the same face position (i.e., 18 in. from the monitor) was approximately 1 mJ/cm2. This value was higher than that estimated from the optical irradiance (0.6 mJ/cm2) measured by the Si photodiode. It needs to be pointed out that the Si photodiode used in this study is wavelength dependent. As the wavelength was set up at 635 nm, it might underestimate the actual total optical irradiance. Interestingly, under the same condition, the integrated fluence from the LCD or LED was 40% or 80% higher than that of the CRT. The active diagonal screen size of the CRT, LCD, and LED was 16, 15, and 17.2 in., respectively. Under the white screen mode, the relative fluence of visible emission from the LCD or LED was 40% or 60% higher than that of the CRT when the total emission intensity was set up at the same level (see Fig. 1). Although the difference in the screen size might contribute to some variation, this finding suggests that the common assumption that LCD and LED monitors might be safer than older CRT monitors is incorrect in terms of potential risk of skin phototoxicity.

In some cases, the back of the hands can be exposed to monitor light while working on the keyboard. A recent report indicated that mild phototoxicity could occur on the back of both hands after PDT when the hands were exposed to an LCD monitor for a few hours [

It has been a concern that overexposure to UV and visible radiation in the presence and absence of photosensitizer might be also detrimental to the eye and subsequently to vision [

In summary, our results suggest that the optical and spectral profiles of emissions from color monitors are clinically relevant. Therefore, prolonged exposure to monitor emissions at a close distance might pose as a potential risk to the face, eyes, and hands. Future guidelines on post-PDT care and patient warnings should include the avoidance of overexposure to common light sources, such as computers, video games, and TV monitors after receiving a topical and systemic administration of a photosensitizer. This should be emphasized to certain high-risk patient populations, e.g., teenagers who may play video games for extended periods of time and people who receive repeated topical application of a photosensitizer or prodrug at a short period of time or work long hours in front of a large and bright monitor screen. The same caution is also applicable to patients who take drugs known to cause photoallergic, photosensitive, and phototoxic reactions.

The crucial difference between CRT and LCD exist in their image forming technique. CRT displays image on the screen by making use of electron beam, however, LCD utilizes liquid crystals for the formation of an image on the screen.

Another major difference that exists between CRT and LCD is their size and dimension. CRT monitors are thicker and heavier but small in size than that of LCD.

We will discuss some other important differences between CRT and LCD but before that have a look at the rough draft of the contents to be discussed under this article.

DisadvantagesHeavy, gets heated at rapid rate during operation.Provides fixed aspect ratio and resolution, requires large area, operating temperature is limited between 0 -60 degrees.

CRT is expanded as Cathode ray tube. It is a vacuum tube that produces images when a sharp beam of the electron which is highly focused hits the phosphor screen that is present at the front-end of the tube.

It consists of certain basic components that are responsible for the generation of an image on the screen. The figure below shows internal system involved in a CRT:

An electron gun assembly is present that produces a sharp beam of electrons. These electrons when moves inside the tube experience acceleration by the anode and focused towards the screen.

The two deflection plates are the reason for the movement of the beam horizontally and vertically. However, as the two movements are not dependent on each other thus the beam after hitting the screen, gets fixed anywhere on it.

When we talk about the screen of CRT then it is basically termed as the faceplate. The inner surface where the beam strikes is basically a phosphor coating. This phosphor is responsible for the conversion of electrical energy generated by the movement of the electron beam into light energy.

It is noteworthy in case of CRT that phosphor screen generates secondary electrons when electron beam hits it. So, in order to sustain an electrical equilibrium, the secondary emitted electrons must be collected which is done by aquadag.

LCD stands for Liquid Crystal Display. In LCD liquid crystal is utilized in order to generate a definite image on the screen. Liquid crystal is basically termed as the fourth state of matter. It permits the display to be very thin and thus supports numerous applications.

When we talk about LCD then its principle of working is such that light energy is not produced by LCD, despite light energy generated by an external source is controlled in order to have light or dark appearance at some particular areas.

Here, a layer of liquid crystal is placed between 2 polarizing films. When light emitted by an external source falls on the layer of liquid crystal then their combination generates a coloured visible image that is displayed on the screen.

An external potential is provided to the liquid crystal. This potential changes the orientation of the molecules. After this polarized light is passed to the crystal that generates bright and dark spots at the screen of the display.

One of the excellent property of LCD over CRT is its antiglare property. LCD screen more efficiently reduces the glare generated by light as compared to CRT.

CRT is more dominant to flickering as it possesses a low refresh rate that causes a drop in image brightness that is easily recognized by naked eyes.As against, flickering is not that much higher in LCD due to its high refresh rate.

CRT and LCD both have their separate advantages and disadvantage over the image formation technique. But LCD has replaced CRT very efficiently in the recent era. Despite LCD is more costly than CRT but due to its better image display and almost negligible flickering property, it is widely used.

The temporal and spatial luminance characteristics of a CRT monitor and two LCD monitors were tested. The CRT monitor (P1230, Dell Inc. TX, USA, referred to as “CRT”) had maintained an excellent working condition after 10 years of use. The first LCD monitor (ASUS PG278Q) was tested in two different modes: once in the ULMB mode, which was our candidate and is referred to here as “LCD1-ULMB,” and once in Overdrive (OD) mode, which we refer to as “LCD1-OD.” The second monitor was an ASUS VG278 tested in the standard mode (LCD2). All the tested monitors were driven by an NVIDIA GeForce GTX 960 graphics card.

The monitors’ configurations and basic luminance characteristics are shown in Table 1. The contrast was set to 50%, 80%, and 100% for LCD1, LCD2, and CRT, respectively. The luminance was set to 90% for LCD1 and CRT, and to 100% for LCD2. The resolution of the CRT was set to 1,024 × 768 pixels, and the LCDs were set to their native resolutions, which were 2,560 × 1,440 for LCD1 and 1,920 × 1,080 for LCD2. A refresh rate of 120 Hz was used for all monitors. The user-mode and the default-mode color temperatures were used for the LCDs and CRT, respectively. These settings were kept constant throughout the test.

Luminance was measured in two ways. First, a photodiode (BPW21R, Vishay Intertechnology, Inc. ShangHai, China) with a switch time below 1 μs was placed in the centers of different areas of the monitor to measure their temporal and spatial characteristics. Voltages, proportional to luminance changes, were amplified and recorded by an electrophysiology (EEG) recording system (Synamps II, Compumedics NeuroScan, Charlotte, USA) at a sampling rate of 10 kHz and were used to characterize the luminance properties of each monitor. The second method was to use a ColorCal MKII photometer (Cambridge Research Systems Ltd., Cambridge, UK) to measure the dependence of luminance on pixel location and viewing angle.

All measurements were taken in a dark room after the monitors had been turned on for at least 60 min, to minimize variation due to warming up (Klein, Zlatkova, Lauritzen, & Pierscionek, 2013). The study was approved by the Academic Committee of the College of Education, Soochow University. All of the Matlab code to analyze the data is available at https://github.com/yangzhangpsy/monitorTestForPsy.

To measure the spatial homogeneity of luminance, the whole display of each monitor was divided evenly into nine rectangular areas (appearing as a 3 × 3 grid). The centers of the nine areas were measured one by one in a random order. Test images were generated and displayed over these nine areas using Matlab (2011b; MathWorks Inc., Natick, USA) with Psychtoolbox (3.0.14; Pelli, 1997b).

Three series of tests were carried out using two different types of images. The first series tested the luminance dependence on pixel location and time (Pelli, 1997a). The test was based on presentation of a solid white ellipse fitting the inside of each rectangular area of the display, and measurements were made using the photodiode placed in the center of the ellipse over each area. Each location was tested for 50 trials, each of which consisted of a black display (100 ms) and an image (33.3 ms). A trigger was sent to the EEG amplifiers by the photodiode via a parallel port when the image appeared on the screen.

The luminance dependence on viewing angle was measured in the third test series for the CRT and LCD1-ULMB (the candidate monitor). The luminance at the center of the screen was measured with the photometer 28.5 cm away from the screen center at seven viewing angles (– 45°, – 30°, – 15°, 0°, 15°, 30°, and 45°) along the horizontal meridian. The luminance at each viewing angle was measured five times and then normalized to the maximum luminance of each monitor measured at 0°.

To understand the spatial and temporal characteristics of the monitors, two parameters—initial latency and relative maximum luminance of the first frame (RML1st)—were calculated from luminance values measured with the photodiode for each trial at each location. Because the luminance was recorded with the EEG system at a digitizing rate of 10 kHz, the temporal resolution was 0.1 ms. To calculate the initial latency, the stimulus onset time was detected as the time point at which the luminance first reached or exceeded 40% of the maximum luminance (with the restriction that the eight consecutive bins just before the onset time bin should be less than 44% of the maximum potential). The initial latency was then calculated as the interval between the stimulus trigger and stimulus onset.

RML1st was defined as the percentage of the maximum luminance of the first frame relative to the maximum luminance over the second and third frames. The maximum luminance was defined differently for different monitors, since the images were displayed continuously for LCD1-OD and LCD2 but displayed in a flash style for CRT and LCD1-ULMB. For the continuously displaying monitors (LCD1-OD and LCD2), the maximum luminance for the first frame was defined as the mean luminance over the first 8.2 ms (corresponding to the duration of a single frame at a 120-Hz refresh rate), whereas the maximum luminance over the next two frames was defined as the mean luminance from 8.3 to 24.9 ms. For the CRT, the maximum luminance was defined as the mean luminance around peaks (0.1 to 0.6 ms, 8.4 to 8.9 ms, and 16.8 to 17.3 for the first, second, and third frames, respectively). For LCD1-ULMB, the maximum luminance was defined as the mean luminance around plateaus (0 to 1.6 ms, 8.3 to 9.9 ms, and 16.7 to 18.3 ms for the first three frames, respectively).

Since the production of cathode ray tubes has essentially halted due to the cost and environmental concerns, CRT-based monitors are considered an outdated technology. All laptops and most desktop computer systems sold today come with LCD monitors. However, there are a few reasons why you might still prefer CRT over LCD displays.

While CRT monitors provide better color clarity and depth, the fact that manufacturers rarely make them anymore makes CRTs an unwise choice. LCD monitors are the current standard with several options. LCD monitors are smaller in size and easier to handle. Plus, you can buy LCD monitors in a variety of sizes, so customizing your desktop without all the clutter is easy.

The primary advantage that CRT monitors hold over LCDs is color rendering. The contrast ratios and depths of colors displayed on CRT monitors are better than what an LCD can render. For this reason, some graphic designers use expensive and large CRT monitors for their work. On the downside, the color quality degrades over time as the phosphors in the tube break down.

Another advantage that CRT monitors hold over LCD screens is the ability to easily scale to various resolutions. By adjusting the electron beam in the tube, the screen can be adjusted downward to lower resolutions while keeping the picture clarity intact. This capability is known as multisync.

The biggest disadvantage of CRT monitors is the size and weight of the tubes. An equivalently sized LCD monitor can be 80% smaller in total mass. The larger the screen, the bigger the size difference. CRT monitors also consume more energy and generate more heat than LCD monitors.

For the most vibrant and rich colors, CRTs are hard to beat if you have the desk space and don"t mind the excessive weight. However, with CRTs becoming a thing of the past, you may have to revisit the LCD monitor.

The biggest advantage of LCD monitors is the size and weight. LCD screens also tend to produce less eye fatigue. The constant light barrage and scan lines of a CRT tube can cause strain on heavy computer users. The lower intensity of the LCD monitors coupled with the constant screen display of pixels being on or off is easier on the eyes. That said, some people have issues with the fluorescent backlights used in some LCD displays.

The most notable disadvantage to LCD screens is the fixed resolution. An LCD screen can only display the number of pixels in its matrix. Therefore, it can display a lower resolution in one of two ways: using only a fraction of the total pixels on the display, or through extrapolation. Extrapolation blends multiple pixels together to simulate a single smaller pixel, which often leads to a blurry or fuzzy picture.

For those who are on a computer for hours, an LCD can be an enemy. With the tendency to cause eye fatigue, computer users must be aware of how long they stare at an LCD monitor. While LCD technology is continually improving, using techniques to limit the amount of time you look at a screen alleviates some of that fatigue.

Significant improvements have been made to LCD monitors over the years. Still, CRT monitors provide greater color clarity, faster response times, and wider flexibility for video playback in various resolutions. Nonetheless, LCDs will remain the standard since these monitors are easier to manufacture and transport. Most users find LCD displays to be perfectly suitable, so CRT monitors are only necessary for those interested in digital art and graphic design.

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 1888,Friedrich Reinitzer (1858–1927) discovered the liquid crystalline nature of cholesterol extracted from carrots (that is, two melting points and generation of colors) and published his findings at a meeting of the Vienna Chemical Society on May 3, 1888 (F. Reinitzer: Beiträge zur Kenntniss des Cholesterins, Monatshefte für Chemie (Wien) 9, 421–441 (1888)).Otto Lehmann published his work "Flüssige Kristalle" (Liquid Crystals). In 1911, Charles Mauguin first experimented with liquid crystals confined between plates in thin layers.

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.

Mini-LED: Backlighting with Mini-LEDs can support over a thousand of Full-area Local Area Dimming (FLAD) zones. This allows deeper blacks and higher contrast ratio.

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.

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