lcd display comparison supplier

Distributor of component LCDs for equipment which provide high-contrast ratio, color saturation, luminance and performance enhancements such as advanced wide viewing (AWV) for true color fidelity, super-high brightness (SHB) and wide temperature range. Focus on industrial, instrumentation, hand-helds, medical and other low-to-medium volume markets. High-bright LED backlights for outdoor use. LVDS interfaces decrease EMI. Factory installed touch screen solutions. 3.5" to 12.1" QVGA, HVGA, VGA, WVGA, SVGA, XGA, WXGA. Also distributes other related products including LED drivers, lamps, indicators, LED assemblies, segment displays, LED mounts, LEDs, and light pipes. Distributor of electronic components, hardware and fasteners and provides design/value engineering support, fulfillment strategies, procurement services and transactional models to meet specific needs and priorities.

Liquid Crystal Display (LCD) screens are a staple in the digital display marketplace and are used in display applications across every industry. With every display application presenting a unique set of requirements, the selection of specialized LCDs has grown to meet these demands.

LCD screens can be grouped into three categories: TN (twisted nematic), IPS (in-plane switching), and VA (Vertical Alignment). Each of these screen types has its own unique qualities, almost all of them having to do with how images appear across the various screen types.

This technology consists of nematic liquid crystal sandwiched between two plates of glass. When power is applied to the electrodes, the liquid crystals twist 90°. TN (Twisted Nematic) LCDs are the most common LCD screen type. They offer full-color images, and moderate viewing angles.

TN LCDs maintain a dedicated user base despite other screen types growing in popularity due to some unique key features that TN display offer. For one,

VA, also known as Multi-Domain Vertical Alignment (MVA) dislays offer features found in both TN and IPS screens. The Pixels in VA displays align vertically to the glass substrate when voltage is applied, allowing light to pass through.

Displays with VA screens deliver wide viewing angles, high contrast, and good color reproduction. They maintain high response rates similar to TN TFTs but may not reach the same sunlight readable brightness levels as comparable TN or IPS LCDs. VA displays are generally best for applications that need to be viewed from multiple angles, like digital signage in a commercial setting.

IPS (In-Plane Switching) technology improves image quality by acting on the liquid crystal inside the display screen. When voltage is applied, the crystals rotate parallel (or “in-plane”) rather than upright to allow light to pass through. This behavior results in several significant improvements to the image quality of these screens.

IPS is superior in contrast, brightness, viewing angles, and color representation compared to TN screens. Images on screen retain their quality without becoming washed out or distorted, no matter what angle they’re viewed from. Because of this, viewers have the flexibility to view content on the screen from almost anywhere rather than having to look at the display from a front-center position.

IPS displays offer a slightly lower refresh rate than TN displays. Remember that the time for pixels to go from inactive to active is measured in milliseconds. So for most users, the difference in refresh rates will go unnoticed.

Based on current trends, IPS and TN screen types will be expected to remain the dominant formats for some time. As human interface display technology advances and new product designs are developed, customers will likely choose IPS LCDs to replace the similarly priced TN LCDs for their new projects.

Flat-panel displays are thin panels of glass or plastic used for electronically displaying text, images, or video. Liquid crystal displays (LCD), OLED (organic light emitting diode) and microLED displays are not quite the same; since LCD uses a liquid crystal that reacts to an electric current blocking light or allowing it to pass through the panel, whereas OLED/microLED displays consist of electroluminescent organic/inorganic materials that generate light when a current is passed through the material. LCD, OLED and microLED displays are driven using LTPS, IGZO, LTPO, and A-Si TFT transistor technologies as their backplane using ITO to supply current to the transistors and in turn to the liquid crystal or electroluminescent material. Segment and passive OLED and LCD displays do not use a backplane but use indium tin oxide (ITO), a transparent conductive material, to pass current to the electroluminescent material or liquid crystal. In LCDs, there is an even layer of liquid crystal throughout the panel whereas an OLED display has the electroluminescent material only where it is meant to light up. OLEDs, LCDs and microLEDs can be made flexible and transparent, but LCDs require a backlight because they cannot emit light on their own like OLEDs and microLEDs.

Liquid-crystal display (or LCD) is a thin, flat panel used for electronically displaying information such as text, images, and moving pictures. They are usually made of glass but they can also be made out of plastic. Some manufacturers make transparent LCD panels and special sequential color segment LCDs that have higher than usual refresh rates and an RGB backlight. The backlight is synchronized with the display so that the colors will show up as needed. The list of LCD manufacturers:

Organic light emitting diode (or OLED displays) is a thin, flat panel made of glass or plastic used for electronically displaying information such as text, images, and moving pictures. OLED panels can also take the shape of a light panel, where red, green and blue light emitting materials are stacked to create a white light panel. OLED displays can also be made transparent and/or flexible and these transparent panels are available on the market and are widely used in smartphones with under-display optical fingerprint sensors. LCD and OLED displays are available in different shapes, the most prominent of which is a circular display, which is used in smartwatches. The list of OLED display manufacturers:

MicroLED displays is an emerging flat-panel display technology consisting of arrays of microscopic LEDs forming the individual pixel elements. Like OLED, microLED offers infinite contrast ratio, but unlike OLED, microLED is immune to screen burn-in, and consumes less power while having higher light output, as it uses LEDs instead of organic electroluminescent materials, The list of MicroLED display manufacturers:

Sony produces and sells commercial MicroLED displays called CLEDIS (Crystal-LED Integrated Displays, also called Canvas-LED) in small quantities.video walls.

LCDs are made in a glass substrate. For OLED, the substrate can also be plastic. The size of the substrates are specified in generations, with each generation using a larger substrate. For example, a 4th generation substrate is larger in size than a 3rd generation substrate. A larger substrate allows for more panels to be cut from a single substrate, or for larger panels to be made, akin to increasing wafer sizes in the semiconductor industry.

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The "wow factor" of a properly executed, larger-than-life video wall display is so compelling a communication tool that, by 2017,total digital signage revenue is expected to amount to $17.1 billion across a wide range of marketing verticals.

Today"s offering of LCD displays is as varied as that of automobile models?each with their own specifications and appeal to customers. As end users demand more and more resolution, LCD display manufacturers are heeding the call.

Many brands offer full HD digital displays with 4K (3840 x 2160) resolution and almost non-existent bezels?some are even testing 8K resolution with early adopters.

No matter what LCD displays VARs choose for their customers, specificity, price, and end use will be the primary considerations. With that in mind, here are a few brands, along with highlights, for VARs to consider when selecting a digital LCDvideo wall solution for customers.

Not to be outdone, Samsung"s OHD line of LCD displays in sizes from 46" to 55" touts its new SMART Signage Platform (SSP), which promises customized solutions and remote content management.

High brightness; a 178-degree viewing angle; a wide operating temperature range; and rugged, outdoor-capable engineering puts this line of LCDs in the "top pick" category of video wall displays.

In particular, the NEC P402 40" professional-grade LCD display boasts full HD resolution (1920 x 1080) and rugged, industrial-strength design for demanding applications.

The NEC X Series commercial-grade displays available in 43" promise high-contrast images, enhanced video wall capabilities, including their proprietary TileMatrix function, 1920 x 480 native resolution and an ambient light sensor that provides consistent brightness in any lighting condition.

Barco, once an industry leader in the prehistoric age of 3-gun analog video projectors, is holding its own in today"s LCD video display market with the super-narrow NSL Series 46" tiled LCD display.

Depending on the application, VARs should look LCD displays with super-narrow bezels, scratch-resistant glass, front-facing maintenance access panels.

As video wall manufacturers continue to improve the quality and versatility of LCD displays, VARs will have access to a much greater selection of solution-specific products to offer their customers.

Outlined in this section are TFT LCD (Thin Film Transistor Liquid Crystal Display) basic knowledge, including structures, driving methods (Passive Matrix / PMLCD, Active Matrix / AMLCD) and comparison, RGB filters, display mode, generations and production process.

As our society progresses into an overwhelmingly technological state, screens seem to pop up almost everywhere. Behind those glass displays, or flat panel displays, lie hundreds of thousands of complex, tiny devices, controlling the pixels that comprise the overall image we see. Those devices are known as Thin Film Transistors, or abbreviated, TFTs.

A TFT LCD,  or a thin film transistor liquid crystal display, is one of the fastest growing forms of display technology today. The thin film transistor (TFT) is a type of semiconductor device used in display technology to enhance efficiency, compactness, and cost of the product.

LCD has a genetic disadvantage compared to other display technologies: Narrow Viewing Angles.  For the last 40 years, scientists and engineers put a lot of effort to improve LCD viewing angles and made great progress. In this section we will introduce O-Film TFT, MVA (Multi-domain Vertical Alignment) TFT, IPS (In Plane Switching)and AFFS (Advanced Fringe Field Switching) TFT.

Most of TFT LCDs are hard to read under the sunlight. Orient Display offer Sunlight Readable TFT with these approaches: Transflective TFT, Surface Treatment, Optical Bonding.

Orient Display’s Electro-Optical Characteristics contains sections of Optical Measurement System, Viewing Angle Range & Measurement System, Contrast Ratio and Response Time.

We have thousands of standard products that are in stock and available from our Seattle, WA and Hong Kong warehouses to support fast product development and preproduction without MOQ. The stock covers TN, STN LCD display panels, COB, COG character LCD display, graphic LCD display, PMOLED, AMOLED display, TFT display, IPS display, high brightness and transflective, blanview sunlight readable display, super high contrast ratio display, lightning fast response displays, efficient low power consumption display, extreme temperature range display, HMI display, HDMI display, Raspberry Pi Display, Arduino display, embedded display, capacitive touch screen, LED backlight etc.  Customers can easily purchase samples directly from our website to avoid time delays with setting up accounts and credit terms and shipping within 24 hours.

Many of our customers require customized OEM display solutions.  With over two decades of experience, we apply our understanding of available display solutions to meet our customer’s requirements and assist from project concept to mass production. Using your ideas and requirements as a foundation, we work side by side with you to develop ideas/concepts into drawings, build prototypes and to final production seamlessly. In order to meet the fast changing world, we can provide the fastest turnaround in the industry, it takes only 3-4 weeks to produce LCD panels samples and 4-6 weeks for LCD display module, TFT LCD, IPS LCD display, and touch screen samples. The production time is only 4-5 weeks for LCD panels and 5-8 weeks for LCD display module, TFT LCD, IPS LCD display, and touch screen.

A Leading OEM in the Point of Sale (POS) Industry contacted PDI in early 2010 with serious lead time concerns. Their current LCD supplier was making a major push towards TFT. This coupled with severe post-Chinese New Year worker shortages, made their current graphics LCD lead time a major focal point. At 16-18 weeks, they were turning down sales.

They approached Phoenix Display to produce a hardware and software drop in replacement with the intent of reducing their lead time to 10 weeks. Based on projected volumes, we were able to provide a 6 week lead time through procurement of a few longer lead time items. An additional benefit to our customer was a cost reduction of 18%! This program turned out to be so effective, that it wasn’t long before other the display programs followed.

The ground work for PDI was laid on our ability to exceed our customers’ expectations. On average, PDI reduces customers’ display cost by 15% – 20%. At the same time PDI also focuses on the critical needs of customers’, such as improving; lead-time, logistics, performance or quality. Based on PDI’s ability to address these needs, PDI now supplies nine different LCD modules to this POS customer.

There is a constant debate on Amoled vs LCD, which is a better display? Where Amoled display offers some remarkable colors with deep black eye-soothing contrast ratio, LCD displays offer much more subtle colors with better off-axis angles for viewing & offers a much brighter picture quality.

While purchasing a new smartphone we consider various specifications like software, camera, processor, battery, display type etc. Among all the specifications display is something that most people are concerned about. 2 of the major competitors of smartphone display are AMOLED and LCD. Often in the LCD vs Amoled comparison, people get confused about which one to choose. In this article, we have explained a clear comparison of the Amoled vs LCD screen to find out which is actually better.

Amoled display is nothing but a part of OLED display which comes with some extra features. The first component is Light Emitting Diode (LED) and the second component is "O", here "O" stands for organic & together they make OLED. The real meaning derived from it is organic material placed with 2 conductors in every LED. And this is how light is produced.

The OLED display can generate light out of individual pixels. AMOLED displays contain Thin Film Translator (TLT) which makes the overall procedure of sourcing current to the correct pixel much quicker and smoother. The TXT further helps grab control for operating different pixels at a time. For example, some pixels could be absolutely switched off though others remain on in Amoled displays. This produces a deep black color.

Speaking about LCDs, it is relatively pretty much commonly found in today"s smartphones. LCD (Liquid Crystal Display) offers a devoted black light that is white or rather slightly blueish in color. Mostly here we get a blue light that is passed through some yellowish phosphor filter which brings out the white light. The white light is subsequently passed through multiple filters and thereafter the crystal elements are again passed through blue, red & green filters. Note that LCD displays have both passive and active matrix which depends on the cost and requirement involved.

Since the process involved in LCDs is much more complex than Amoled & requires extra steps, when compared to AMOLED displays, LCDs are less battery friendly. In the technological era where energy efficiency is the first priority, Amoled displays are certainly going to be the future of display technology. But both of them come with a separate set of pros and cons and it is only by knowing the pros and cons you will be able to choose the right one.

Amoled display technology is mostly used in smartphones, media players & digital cameras. Amoled is mostly used in low power, cost-effective & large application sizes.

Cost is one of the major factors that act as a differentiator between the two display types. Amoled displays are comparatively more expensive than LCD displays because LCD displays are much cheaper to manufacture. So while buying a low-budget smartphone, the probability to get a Amoled display is pretty less.

The quality of a display is mainly measured according to the colors and sharpness it offers. Also while comparing two displays, only technology comparison won"t work because often displays behave inversely even if a manufacturer is using the very same technology. If you consider colors especially contrasting colors such as blue, red or green, Amoled will serve better throughout the day. This happens mainly because in the case of AMOLED displays, as mentioned above, every pixel present in it emit its own light whereas in LCD light comes out of the backlight. Therefore Amoled displays offer high-end saturation and vibrant colors compared to LCD displays.

As Amoled displays put out vibrant colors, you will find Amoled displays to be warmer in nature compared to LCD displays which has a more neutral whitish tint. In short, the pictures seen on Amoled displays are more eye-soothing compared to LCD displays where the pictures appear more natural.

In the Amoled vs LCD screen display comparison, another thing to consider is the brightness offered by both of them. Compared to LCD displays, Amoled displays have lesser brightness levels. This is mainly because of the backlight in LCD displays which emits a higher brightness level. Therefore if you are a person who spends most of the time outdoors and mostly uses your smartphone under the sun, then LCD is the right choice for you. Although certain leading brands are working on the brightness level in Amoled displays.

The display is one such thing that sucks your phone"s battery to a great extent. In Amoled displays, the pixels can get absolutely switched off thereby saving a lot of battery. Whereas LCD displays remain dependent on the back light, as a result even if your screen is completely black, the backlight remain switched on throughout. This is why even though Amoled displays are more expensive than LCD displays as they consume much less battery than LCD displays.

In the battle between LCD display vs Amoled display both come with separate pros and cons. Well if battery consumption and color contrast or saturation is a concern then the Amoled display is going to win over LCD display anyway. While purchasing a smartphone, customers today mainly focus on two features- lesser battery consumption and a high-quality display. Amoled display offers both the benefits- high-end vibrant display and less battery consumption. The only criteria where LCD displays win over Amoled is the brightness level. But with brands coming with the latest technologies, Amoled is certainly going to catch up with the brightness level with LCD displays. Also, the brightness difference in current Amoled display smartphones that are available in the market is hardly noticeable.

Mobile display technology is firmly split into two camps, the AMOLED and LCD crowds. There are also phones sporting OLED technology, which is closely associated with the AMOLED panel type. AMOLED and LCD are based on quite different underlying technologies, leading manufacturers to tout a number of different benefits depending on which display type they’ve opted for. Smartphone manufacturers are increasingly opting for AMOLED displays, with LCD mostly reserved for less expensive phones.

Let’s find out if really there’s a noticeable difference between these two display technologies, what sort of differences we can expect, and if the company marketing hype is to be believed.

It’s hidden in the name, but the key component in these display types is a Light Emitting Diode (LED). Electronics hobbyists will no doubt have played around with these little lights before. In a display panel, these are shrunk down dramatically and arranged in red, green, and blue clusters to create an individual pixel that can reproduce white light and various colors, including red, green, and blue.

The arrangement of these sub-pixels alters the performance of the displays slightly. Pentile vs striped pixel layouts, for example, results in superior image sharpness, but lower pixel life spans due to the smaller pixel sizes.

One other term you will encounter is Super AMOLED, which is Samsung’s marketing term for a display that incorporates the capacitive touchscreen right into the display, instead of it being a separate layer on top of the display. This makes the display thinner.

The major benefits from OLED type displays come from the high level of control that can be exerted over each pixel. Pixels can be switched completely off, allowing for deep blacks and a high contrast ratio. Great if you want a display capable of playing back HDR content. Being able to dim and turn off individual pixels also saves on power ever so slightly. The lack of other layers on top of the LEDs means that the maximum amount of light reaches the display surface, resulting in brighter images with better viewing angles.

The use of LEDs and minimal substrates means that these displays can be very thin. Furthermore, the lack of a rigid backlight and innovations in flexible plastic substrates enables flexible OLED-based displays. Complex LCD displays cannot be built in this way because of the backlight requirement. Flexy displays were originally very promising for wearables. Today, premium-tier smartphones make use of flexible OLED displays. Although, there are some concerns over how many times a display can flex and bend before breaking.

LCD stands for Liquid Crystal Display and reproduces colors quite differently from AMOLED. Rather than using individual light-emitting components, LCD displays rely on a backlight as the sole light source. Although multiple backlights can be used across a display for local dimming and to help save on power consumption, this is more of a requirement in larger TVs.

Scientifically speaking, there’s no individual white light wavelength. White light is a mixture of all other visible colors in the spectrum. Therefore, LCD backlights have to create a pseudo white light as efficiently as possible, which can then be filtered into different colors in the liquid crystal element. Most LCDs rely on a blue LED backlight which is filtered through a yellow phosphor coating, producing a pseudo white light.

The really complicated part comes next, as light is then polarized and passed through a crystal element. The crystal can be twisted to varying degrees depending on the voltage applied to it, which adjusts the angle of the polarized light. The light then passes through a second polarized filter that is offset by 90 degrees compared with the first, which will attenuate the light based on its angle. Finally, a red, green, or blue color filter is applied to this light, and these sub-pixels are grouped into pixels to adjust colors across the display.

All combined, this allows an LCD display to control the amount of RGB light reaching the surface by culling a backlight, rather than producing colored light in each pixel. Just like AMOLED, LCD displays can either be active or passive matrix devices, but most smartphones are active these days.

This wide variation in the way that light is produced has quite a profound difference to the user experience. Color gamut is often the most talked-about difference between the two display types, with AMOLED providing a greater range of color options than LCD, resulting in more vibrant-looking images.

OLED displays have been known for additional green and blue saturation, as these tend to be the most powerful colors in the sub-pixel arrangement, and very little green is required for white light. Some observers find that this extra saturation produces results that they find slightly unnatural looking. Although color accuracy has improved substantially in the past few years and tends to offer better accuracy for wider color gamuts like DCI-P3 and BT-2020. Despite not possessing quite such a broad gamut, LCD displays typically offer 100% sRGB gamut used by most content and can cover a wide gamut and most of the DCI-P3 color space too.

As we mentioned before, the lack of a backlight and filtering layers weighs in favor of OLED over LCD. LCD displays often suffer from light bleed and a lower contrast ratio as the backlight doesn’t switch off even when pixels are supposed to be black, while OLED can simply switch off its pixels. LCD’s filtering layer also inherently blocks some light and the additional depth means that viewing angles are also reduced compared to OLED.

One downside of AMOLED is that different LEDs have different life spans, meaning that the individual RBG light components eventually degrade at slightly different rates. As well as the dreaded but relatively rare burn-in phenomenon, OLED display color balance can drift very slightly over time, while LED’s single backlight means that color balance remains more consistent across the display. OLED pixels also often turn off and on slower, meaning that the highest refresh rate displays are often LCD. Particularly in the monitor market where refresh rates exceed 120Hz. That said, plenty of OLED smartphones offer 90, 120, and even 144Hz support.

There are some pros and cons to both technologies and some reasonable user preferences between the different color and contrast profiles. Although the prevalence of multiple display modes available in modern smartphones makes this somewhat less of an issue these days. However, the falling production costs and additional benefits of OLED displays have made them a more popular choice than ever across a wide range of price segments. OLED dominates the high-end smartphone and TV spaces owing to its wider color gamut, superior contrast ratio, while still supporting decent refresh rates. Not to mention its flexible characteristics for brand new mobile form factors.

Major display manufacturers, such as LG Display and Samsung Display, are betting big on OLED technology for the future, making major investments into additional production facilities. Particularly when it comes to its use in flexible display technology. The AMOLED panel market is expected to be worth close to $30 billion in 2022, more than double its value in 2017 when this article was first published.

That said, developments in Quantum Dot and mini LED displays are closing the already small performance gap between LCD and OLED, so certainly don’t count LCD out of the race just yet.

OLED displays have higher contrast ratios (1 million : 1 static compared with 1,000 : 1 for LCD screens), deeper blacks and lower power consumption compared with LCD displays. They also have greater color accuracy. However, they are more expensive, and blue OLEDs have a shorter lifetime.

OLED displays offer a much better viewing angle. In contrast, viewing angle is limited with LCD displays. And even inside the supported viewing angle, the quality of the picture on an LCD screen is not consistent; it varies in brightness, contrast, saturation and hue by variations in posture of the viewer.

There are no geographical constraints with OLED screens. LCD screens, on the other hand, lose contrast in high temperature environments, and lose brightness and speed in low temperature environments.

Blue OLEDs degrade more rapidly than the materials that produce other colors. Because of this, the manufacturers of these displays often compensate by calibrating the colors in a way that oversaturates the them and adds a bluish tint to the screen.

With current technology, OLED displays use more energy than backlit LCDs when displaying light colors. While OLED displays have deeper blacks compared with backlit LCD displays, they have dimmer whites.

LCDs use liquid crystals that twist and untwist in response to an electric charge and are lit by a backlight. When a current runs through them, they untwist to let through a specific amount of light. They are then paired with color filters to create the display.

Let us start with the basics first; refresh the knowledge about TN and LCD displays in general, later we will talk about TFTs (Thin Film Transistors), how they differ from regular monochrome LCD displays. Then we will go on to the ghosting effect, so we will not only discuss the technology behind the construction of the TFT, but also some phenomena, like the ghosting effect, or grayscale inversion, that are important to understand when using an LCD TFT display.

Next, we will look at different technologies of the TFT LCD displays like TN, IPS, VA, and of course about transmissive and transflective LCD displays, because TFT displays also can be transmissive and transflective. In the last part we will talk about backlight.

Let us start with a short review of the most basic liquid crystal cell, which is the TN (twisted nematic) display. On the picture above, we can see that the light can be transmit through the cell or blocked by the liquid crystal cell using voltage. If you want to learn more about monochrome LCD displays and the basics of LCD displays, follow this link.

What is a TFT LCD display and how it is different from a monochrome LCD display? TFT is called an active display. Active, means we have one or more transistors in every cell, in every pixel and in every subpixel. TFT stands for Thin Film Transistor, transistors that are very small and very thin and are built into the pixel, so they are not somewhere outside in a controller, but they are in the pixel itself. For example, in a 55-inch TV set, the TFT display contains millions of transistors in the pixels. We do not see them, because they are very small and hidden, if we zoom in, however, we can see them in every corner of each pixel, like on the picture below.

On the picture above we can see subpixels, that are basic RGB (Red, Green, Blue) colors and a black part, with the transistors and electronic circuits. We just need to know that we have pixels, and subpixels, and each subpixel has transistors. This makes the display active, and thus is called  the TFT display. TFT displays are usually color displays, but there are also monochrome TFT displays, that are active, and have transistors, but have no colors. The colors in the TFT LCD display are typically added by color filters on each subpixel. Usually the filters are RGB, but we also have RGBW (Red, Green, Blue, White) LCD displays with added subpixels without the filter (White) to make the display brighter.

Going a little bit deeper, into the TFT cell, there is a part inside well known to us from the monochrome LCD display Riverdi University lecture. We have a cell, liquid crystal, polarizers, an ITO (Indium Tin Oxide) layer for the electrodes, and additionally an electronic circuit. Usually, the electronic circuit consists of one transistor and some capacitors to sustain the pixel state when we switch the pixel OFF and ON. In a TFT LCD display the pixels are much more complicated because apart from building the liquid crystal part, we also need to build an electronic part.

That is why TFT LCD display technologies are very expensive to manufacture. If you are familiar with electronics, you know that the transistor is a kind of switch, and it allows us to switch the pixel ON and OFF. Because it is built into the pixel itself, it can be done very quickly and be very well controlled. We can control the exact state of every pixel not only the ON and OFF states, but also all the states in between. We can switch the light of the cells ON and OFF in several steps. Usually for TFT LCD displays it will be 8-bit steps per color, so we have 256 steps of brightness for every color, and every subpixel. Because we have three subpixels, we have a 24-bit color range, that means over 16 million combinations, we can, at least theoretically, show on our TFT LCD display over 16 million distinct colors using RGB pixels.

Now that we know how the TFT LCD display works, we can now learn some practical things one of which is LCD TFT ghosting. We know how the image is created, but what happens when we have the image on the screen for a prolonged time, and how to prevent it. In LCD displays we have something called LCD ghosting. We do not see it very often, but in some displays this phenomenon still exists.

If some elements of the picture i.e., your company logo is in the same place of the screen for a long period of time, for couple of weeks, months or a year, the crystals will memorize the state and later, when we change the image, we may see some ghosting of those elements. It really depends on many conditions like temperature and even the screen image that we display on the screen for longer periods of time. When you build your application, you can use some techniques to avoid it, like very rapid contrast change and of course to avoid the positioning the same image in the same position for a longer time.

You may have seen this phenomenon already as it is common in every display technology, and even companies like Apple put information on their websites, that users may encounter this phenomenon and how to fix it. It is called image ghosting or image persistence, and even Retina displays are not free of it.

Another issue present in TFT displays, especially TN LCD displays, is grayscale inversion. This is a phenomenon that changes the colors of the screen according to the viewing angle, and it is only one-sided. When buying a TFT LCD display, first we need to check what kind of technology it is. If it is an IPS display, like the Riverdi IPS display line, then we do not need to worry about the grayscale inversion because all the viewing angles will be the same and all of them will be very high, like 80, 85, or 89 degrees. But if you buy a more common or older display technology type, like the TN (twisted nematic) display, you need to think where it will be used, because one viewing angle will be out. It may be sometimes confusing, and you need to be careful as most factories define viewing direction of the screen and mistake this with the greyscale inversion side.

On the picture above, you can see further explanation of the grayscale inversion from Wikipedia. It says that some early panels and also nowadays TN displays, have grayscale inversion not necessary up-down, but it can be any angle, you need to check in the datasheet. The reason technologies like IPS (In-Plane Switching), used in the latest Riverdi displays, or VA, were developed, was to avoid this phenomenon. Also, we do not want to brag, but the Wikipedia definition references our website.

We know already that TN (twisted nematic) displays, suffer from grayscale inversion, which means the display has one viewing side, where the image color suddenly changes. It is tricky, and you need to be careful. On the picture above there is a part of the LCD TFT specification of a TN (twisted nematic) display, that has grayscale inversion, and if we go to this table, we can see the viewing angles. They are defined at 70, 70, 60 and 70 degrees, that is the maximum viewing angle, at which the user can see the image. Normally we may think that 70 degrees is better, so we will choose left and right side to be 70 degrees, and then up and down, and if we do not know the grayscale inversion phenomena, we may put our user on the bottom side which is also 70 degrees. The viewing direction will be then like a 6 o’clock direction, so we call it a 6 o’clock display. But you need to be careful! Looking at the specification, we can see that this display was defined as a 12 o’clock display, so it is best for it to be seen from a 12 o’clock direction. But we can find that the 12 o’clock has a lower viewing angle – 60 degrees. What does it mean? It means that on this side there will be no grayscale inversion. If we go to 40, 50, 60 degrees and even a little bit more, probably we will still see the image properly. Maybe with lower contrast, but the colors will not change. If we go from the bottom, from a 6 o’clock direction where we have the grayscale inversion, after 70 degrees or lower we will see a sudden color change, and of course this is something we want to avoid.

To summarize, when you buy older technology like TN and displays, which are still very popular, and Riverdi is selling them as well, you need to be careful where you put your display. If it is a handheld device, you will see the display from the bottom, but if you put it on a wall, you will see the display from the top, so you need to define it during the design phase, because later it is usually impossible or expensive to change the direction.

We will talk now about the other TFT technologies, that allow us to have wider viewing angles and more vivid colors. The most basic technology for monochrome and TFT LCD displays is twisted nematic (TN). As we already know, this kind of displays have a problem with grayscale inversion. On one side we have a higher retardation and will not get a clear image. That is why we have other technologies like VA (Vertical Alignment), where the liquid crystal is differently organized, and another variation of the TFT technology – IPS which is In-Plane Switching. The VA and IPS LCD displays do not have a problem with the viewing angles, you can see a clear image from all sides.

Apart from the different organization of the liquid crystals, we also organize subpixels a little bit differently in a VA and IPS LCD displays. When we look closer at the TN display, we will just see the subpixels with color filters. If we look at the VA or IPS display they will have subpixels of subpixels. The subpixels are divided into smaller parts. In this way we can achieve even wider viewing angles and better colors for the user, but of course, it is more complicated and more expensive to do.

The picture above presents the TN display and grayscale inversion. For IPS or VA technology there is no such effect. The picture will be the same from all the sides we look so these technologies are popular where we need wide viewing angles, and TN is popular where we don’t need that, like in monitors. Other advantages of IPS LCD displays are they give accurate colors, and wide viewing angles. What is also important in practice, in our projects, is that the IPS LCD displays are less susceptible to mechanical force. When we apply mechanical force to the screen, and have an optically bonded touch screen, we push the display as well as squeeze the cells. When we have a TN display, every push on the cell changes the image suddenly, with the IPS LCD displays with in-plane switching, different liquid crystals organization, this effect is lesser. It is not completely removed but it is much less distinct. That is another reason IPS displays are very popular for smartphones, tablets, when we have the touchscreens usually optically bonded.

If we wanted to talk about disadvantages, there is a question mark over it, as some of them may be true, some of them do not rely on real cases, what kind of display, what kind of technology is it. Sometimes the IPS displays can have higher power consumption than others, in many cases however, not. They can be more expensive, but not necessarily. The new IPS panels can cost like TN panels, but IPS panels definitely have a longer response time. Again, it is not a rule, you can make IPS panels that are very fast, faster than TN panels, but if you want the fastest possible display, probably the TN panel will be the fastest. That is why the TN technology is still popular on the gaming market. Of course, you can find a lot of discussions on the internet, which technology is better, but it really depends on what you want to achieve.

Now, let us look at the backlight types. As we see here, on the picture above, we have four distinct types of backlight possible. The most common, 95 or 99 per cent of the TFT LCD displays on the market are the transmissive LCD display type, where we need the backlight from the back. If you remember from our Monochrome LCD Displays lecture, for transmissive LCD displays you need the backlight to be always on. If you switch the backlight off, you will not see anything. The same as for monochrome LCD displays, but less popular for TFT displays, we have the transflective LCD display type. They are not popular because usually for transflective TFT displays, the colors lack in brightness, and the displays are not very practical to use. You can see the screen, but the application is limited. Some transflective LCD displays are used by military, in applications where power consumption is paramount; where you can switch the backlight off and you agree to have lower image quality but still see the image. Power consumption and saving energy is most important in some kind of applications and you can use transflective LCD displays there. The reflective type of LCD displays are almost never used in TFT. There is one technology called Low Power Reflective Displays (LPRD) that is used in TFT but it is not popular. Lastly, we have a variation of reflective displays with frontlight, where we add frontlight to the reflective display and have the image even without external light.

Just a few words about Low Power Reflective Displays (LPRD). This kind of display uses environmental light, ambient light to reflect, and produce some colors. The colors are not perfect, not perfectly clear, but this technology is becoming increasingly popular because it allows to have color displays in battery powered applications. For example, a smartwatch would be a case for that technology, or an electrical bike or scooter, where we can not only have a standard monochrome LCD display but also a TFT LCD color display without the backlight; we can see the image even in

strong sunlight and not need backlight at all. So, this kind of TFL LCD display technology is getting more and more popular when we have outdoor LCD displays and need a low power consumption.

On the picture above, we have some examples of how transmissive and reflective LCD displays work in the sunlight. If we have a simple image, like a black and white pattern, then on a transmissive LCD display, even with 1000 candela brightness, the image probably will be lower quality than for a reflective LCD display; if we have sunlight, we have very strong light reflections on the surface of the screen. We have talked about contrast in more detail in the lecture Sunlight Readable Displays. So, reflective LCD displays are a better solution for outdoor applications than transmissive LCD displays, where you need a really strong backlight, 1000 candela or more, to be really seen outdoors.

To show you how the backlight of LCD displays is built, we took the picture above. You can see the edge backlight there, where we have LEDs here on the small PCB on the edge, and we have a diffuser that distributes the light to the whole surface of LCD screen.

In addition to the backlight, we have something that is called a frontlight. It is similar to backlight, it also uses the LEDs to put the light into it, but the frontlight needs to be transparent as we have the display behind. On the example on the picture above we can see an e-paper display. The e-paper display is also a TFT display variation, but it is not LCD (liquid crystal), it is a different technology, but the back of the display is the same and it is reflective. The example you see is the Kindle 4 eBook reader. It uses an e-paper display and a frontlight as well, so you can read eBooks even during the night.

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