JUNE 2011: Input, output and other peripheral technologies can make or break innovations. For example, no matter how small a chip becomes, a computer or mobile phone cannot become smaller unless its display too becomes more compact. Similarly, however powerful a graphic processor is, its skills cannot be manifested in a device unless the display cooperates. Nanotechnology, three-dimensional (3D) integrated circuits, solar-powered electronics, low-power devices or whatever be the next revolution in electronics, it cannot take off without the help from the display space.
There is a lot happening both in terms of the enabling technologies and the resulting experiences. Micro electromechanical systems, organic light-emitting diodes, surface-emission displays and high-speed phosphor are some of the notable technological advancements, while high-definition, 3D and multi-touch displays are some of the latest experience packages. Some of these are already mature and in the market, while others are still on the anvil. Yet others are still a promise of what the future holds for us.
The magic of multi-touch
Popularised especially by Apple and Microsoft, multi-touch technology is all over the place today. Multi-touch refers to a touch-screen display’s ability to simultaneously register three or more distinct positions of input touches by a stylus or your finger. Brought about by a complex hardware-software team, it enables you to command and control a device through taps, twists and pinches.
A multi-touch display based on capacitive sensing—the most popular technology today—uses a layer of capacitive material to hold an electrical charge. When touched by the user, the charges at the points of contact change. As soon as this happens, a signal is conveyed to the processor, which, in turn, interprets multiple such signals to figure out the position and pressure of the user’s touch, and translates this into respective commands. A pinching movement can zoom-in or zoom-out, and a circular movement can rotate an image, while a swiping movement can flip through pages.
“Multi-touch technology, enabled using capacitive sensing technology, is mostly a separate chip bundled along with different displays. For good performance, the displays should offer a large surface area with less heat dissipation on the screen, making it comfortable for the users to touch with their hands, and a continuous display area without inter-mediate separating bezels,” says Varadha Raju, country head and vice president-operations, Prysm Displays India.
Nihar Mastakar, specialist field applications engineer, Xilinx India, adds, “The advanced software algorithms which are at the heart of the multi-touch sensor chips can easily be run on the Xilinx Zynq-7000—an extensible processing platform (EPP) with dual-core Cortex-A9 MPCore processing system tightly coupled with 28nm programmable logic—making it an enriching experience for the user.”
Multi-touch signifies the start of a journey towards a gesture-based computing era and has become mainstream, thanks to mobile devices like iPhone, tablets and portable PCs such as Apple’s MacBook Pro, Dell’s Latitude and HP’s TouchSmart, and touch-tables like Microsoft Surface. Recent operating systems including Mac OS X, Windows 7, Ubuntu, Apple’s iOS, Nokia’s Symbian, Samsung’s Bada, Google’s Android, Palm’s WebOS, Microsoft’s Windows Phone 7, BlackBerry OS 5.0 and 6.0, and Xandros support touch technology. Windows 7 has many inbuilt touch features, including basic gesture support in Internet Explorer 8.
“The next step in multi-touch technology is gesture recognition, which can make out a user’s command from his action itself without the user having to touch the display,” adds Raju.
High-definition (HD) video is another buzzword today. It refers to display technologies that work at resolutions of the order of 1280×720 pixels (720p) or 1920×1080 pixels (1080i/1080p).
HD video is a consequence of improved vertical display resolution as well as better interlaced and progressive scanning techniques, among other things. Mainly these two factors together determine the type of the HD display. 720p60 HD, for instance, has a resolution of 1280×720 pixels, with progressive encoding at 60 frames per second (60 Hz). The 1080i50 format is 1920×1080 pixels, with interlaced encoding at a speed of 50 fields per second.
HD video is broadcast digitally or written on Blu-ray discs. Today, most brands offer HD-capable televisions and computer monitors and many television channels have HD offerings. HD content is also available on the Web.
Mobile phones going the HD way. Nokia’s N8 and iPhone4 are some of the recent devices equipped with HD display. There is a buzz around the all-new display technology in iPhone4. Termed as Retina by Apple, it is essentially a high-end screen with four times as many pixels as a same-sized screen. It features a resolution of 960×640 on an 8.9cm (3.5-inch) display, with an 800:1 contrast ratio. Retina technology packs almost 78 per cent of the iPad pixels into the iPhone, but in a much tinier screen.
Hitachi is vying to beat this with its new HD display technology, which will hopefully enter the market around October. Hitachi Display’s latest is an 11.4cm (4.5-inch) in-plane switching (IPS) LCD with a whopping resolution of 1280×720 pixels. The display also promises a 329ppi density, which is higher than Apple’s most recent 326 ppi. It is LED-backlit and has a contrast ratio of 1100:1.
Lots more happening. Research teams all over the world are attempting to advance HD technology for use in a variety of devices ranging from television sets and monitors to digital signage and mobile phones.
One recent technology developed by a University of Michigan team features pixels that are eight times smaller than those used by iPhone4. The new colour filter used by them is made of nano-thin metal sheets with precisely-spaced gatings. These gatings trap and transmit light of a particular colour as they are sliced into metal-dielectric-metal stacks.
Jay Guo, an associate professor at the university’s department of electrical engineering and computer science, says, “Amazingly, we found that even a few slits can already produce well-defined colour, which shows its potential for extremely high-resolution display and spectral imaging.” He goes on to explain that only about 5 per cent of the backlight from conventional LCDs actually reaches the human eye. This is because in addition to the LCD layer, current technologies use two layers of polariser, a colour filter sheet and two layers of glass laced with electrodes. The new technology, on the other hand, has fewer layers because the colour filter acts as the polariser as well. This will not only improve the image quality but also reduce the manufacturing cost.
The patent-pending ultra-high-definition technology can be used for projection displays, compact screens, bendable screens and military applications.
3D is the future
If HD is today’s revolution, 3D is going to be tomorrow’s. There appear to be a slew of 3D products—3D televisions, 3D monitors, 3D video games, 3D movies, 3D glasses and even 3D goggles that add a third dimension to games you play on your iPhone or iPod—slowly popping up on store shelves globally, though very few are visible in the Indian market yet. 3D TVs are leading the pack.
Today’s 3D displays are mainly stereoscopic models that alternately telecast images meant for the left and right eye, stored in the even and odd fields, respectively, of the video signal. Or a shutter glass worn by the viewer alternately shuts off each eye, so that the eye sees only the video stream meant for it. The brain then follows its natural process of merging the two streams of data to present a 3D view to the user, just as it would merge the views of the right and left eye when we see a scene around us naturally.
While this was the basic technology behind 3D movies we saw decades ago, it has now come to our living rooms, thanks to the advanced display technology, lighter and stylish shutter glasses, and more capable broadcast techniques.
LED models, plasma models, special cameras for easy shooting of 3D content, real-time 2D-to-3D converters and more such technologies are coming up. Auto-stereoscopic models which do not require glasses, are also expected in the future. In fact, mobile phone makers such as NTT DoCoMo, LG and HTC have already introduced devices that feature glassless 3D displays.
However, due to high price tags and insufficient content, 3D products are yet to catch up in India.
Experiences like multi-touch, high-definition and 3D aren’t possible without significant contribution from basic sciences such as optics and materials science. There are several new developments on this front. One is the emergence of organic light-emitting diodes (OLEDs) as a strong contender. Barring a few issues that need to be ironed out before mass adoption, this technology is almost there. Another interesting trend is the renewed interest in surface-emissive displays (SEDs). Apart from these main trends, there are several smaller developments taking place.
“Materials science technology influences both the displays and their controllers. One of the recent innovations in material science is the high-speed phosphor (HSP)—a new technology that Prysm is actively involved in developing. HSP technology is efficiently driven by the solid-state lighting industry. On the other hand, the semiconductor industry is moving towards the next-generation 28nm technology process—a high-performance, low-power process using low-K dielectric materials—jointly developed by Taiwan Semiconductor Manufacturing Company and Xilinx engineers. This will be very important for future display technologies as it combines high performance with low power,” says Mastakar.
Response time of the order of a few microseconds can be achieved using HSP technology. In comparison, with LCD technology, the response time is of the order of 2-8 milliseconds, and the faster the LCD, the higher the cost. Another recent materials related development in the display space is the use of polyester films for flexible displays and touch screens. As the market evolves, customers and end-users are demanding flexible display technology with reduced device thickness, improved economics and productivity, and enhanced optics. Polyester films help meet these needs.
Last year, DuPont Teijin Films in-troduced Melinex Thin heat-stabilised polyester films that feature superior optical clarity, smooth surface, thin 50-micron profile, low shrinkage and predictable dimensional changes in variable heat and moisture conditions, making their dimensional stability comparable to thicker films and suitable for vacuum processing.
Last year also saw the introduction of adhesive-coated polyethylene terephthalate (PET) optical films and polyethylene naphthalate (PEN) films for mount/demount applications where a carrier is used for processing. These are widely adopted in the making of flexible displays.
This year’s Consumer Electronics Show (CES) in Las Vegas too featured quite a few material innovations. 3M introduced patterned transparent conductors (PTCs) for such applications as projected-capacitance touch screens and antennae. “PTC materials offer improved performance of the projected capacitive sensor by supporting narrow bezel capability and faster sensor-response times with excellent optical performance,” said a company spokesperson.
The conductive material in 3M’s PTCs is usually thin silver wires embedded in an optical polymer sheet. Flexibility and increased conductivity are the main advantages of PTCs. Typically, sheet resistance is in the vicinity of 20 ohms per square, compared to 100-300 ohms per square for older indium-tin-oxide (ITO) technologies.
Organic leds—still pocket-sized!
An OLED is basically a light-emitting diode in which the light is emitted by a film of organic compounds in response to an electric current. This layer of organic semiconductor material is sandwiched between two electrodes, of which at least one is transparent.
An OLED display functions without a backlight, is thinner and lighter than an LCD, and can display deep black levels. It has a faster refresh rate, higher contrast, wider viewing angle and better colour reproduction. It is also believed to be much cooler than conventional LCDs or LED-backlit LCDs. The power drain is also very low. All this makes OLED displays ideal for mobile instruments.
Although these benefits are desirable in larger displays too, OLED televisions and other large-sized displays have not yet gained momentum due to multiple problems. The current generation of OLEDs emits less light per unit area than inorganic solidstate LED light sources and their brightness is lower than LCD screens’. Also, since these use organic materials, they degrade over time.
“The lifespan of OLEDs is of concern in terms of manufacturing, toxicity, and scalability to different sizes and configurations,” adds Raju. Since portable displays are used intermittently, the shorter lifespan of organic displays is less of an issue than with television or computer monitors.
The cost of OLEDs is also very high. Although companies like Sony, LG and Samsung have come up with OLED televisions, they are yet to classify as mainstream models.
In mid 2010, DuPont announced that it could produce a 127cm (50-inch) OLED TV in two minutes with a new printing technology, and that these televisions could have a lifespan of 15 years even if used for around eight hours a day. The cost of these televisions would also be quite less, the company said. However, DuPont is still figuring out how to scale up this technology to volume manufacturing at low costs.
Acronym war in the mobile space
As of today, the OLED war is happening mainly in the mobile space. The air is filled with buzzwords ranging from Super-LCD and AMOLED to Super-AMOLED.
The addressing scheme used by OLED displays can be either passive-matrix (PMOLED) or active-matrix (AMOLED). The latter comprises a matrix of OLED pixels that generate light upon electrical activation. This is integrated with a thin-film transistor (TFT) array, which functions as a series of switches to control the current flowing to each individual pixel.
AMOLED displays consume less power than PMOLED displays, and are a step towards low-power, low-cost and large-size applications such as televisions. AMOLED technology is becoming quite popular in smartphones and digital cameras today. Certain manufacturers have started integrating the production of capacitive sensor arrays in the AMOLED module fabrication process, thereby adding touch capability to AMOLED displays. Samsung markets this technology as Super-AMOLED. Brightness and degradation issues have also been addressed to a certain extent in this new version.
AMOLED also lends itself to flexible displays. In fact, some AMOLED-based flexible display innovations were showcased at the Consumer Electronics Show (CES) 2011. One example is the 0.27mm thick, 11.43cm (4.5-inch) flexible WVGA AMOLED display with a bending radius of less than 10 mm showcased by Samsung Mobile Display. However, larger flexible displays are still on the wish-list.
The technology that is giving AMOLED stiff competition in the smart phone space is Super-LCD (S-LCD). An upgrade of the time-tested LCD technology, this method of display is very power-efficient. It also overcomes some of the shortcomings of AMOLED, such as the high proportion of white pixels on the screen. Some manufacturers appear to prefer S-LCD because it is based on an already mature technology and does not face degradation and other inherent problems of OLEDs. S-LCD is mainly promoted by Sony. Apple’s Retina technology is also comparable to S-LCD.
Mature and popular. Multi-touch and high-definition displays, large and small; LED and OLED-backlit LCD displays of all sizes; full OLED displays in mobile devices; low-power, eco-friendly displays
Mature and gaining popularity. MEMS-powered mobile displays; 3D display technology; heat-stabilised polyester, PET and PEN films and patterned transparent conductor (PTC) films for flexible displays
Being fine-tuned. Large-format OLED displays; interactive displays
Emerging. Surface-emissive display technologies; shapeless, transparent, flexible, low-power and interactive displays for ubiquitous computing
Surface-emissive display technology
Surface-conduction electron-emitter display or surface-emissive display (SED) is a technology that was in development alongside LCDs. However, when LCDs gained dominance some years ago, many companies wound down their SED development efforts. When many thought SED was a dead technology, companies like AU Optronics and Prysm Display picked up the threads and gave life to it again. Now it is picking up steam, especially since it is believed that current developments in nanotechnology can breathe new life into SEDs.
SED technology is especially suited for flat-panel televisions and other thin displays. It uses nanoscopic electron emitters to energise coloured phosphors and produce an image. An SED can be seen as a matrix of tiny cathode ray tubes, each forming a single sub pixel on the screen. These are grouped in threes, denoting red, green and blue (RGB) pixels. SEDs feature high contrast ratios, wide viewing angles, significantly low power consumption and very fast response times, all within a very thin form factor.
Prysm came out with a highly-discussed breakthrough in SEDs recently. Its new laser phosphor display (LPD) technology combines a phosphor panel, laser engine and laser processor. The result is a thin, large-format display that combines the low-power consumption and reliability of solidstate lasers with a surface-emissive screen.
“Fundamentally different from LED or LCD-based display technology, the LPD creates a modular, highly configurable display panel with brilliant image quality and the industry’s smallest environmental footprint. It uses rapid surface-scanning lasers controlled by advanced, high-speed inputs/outputs (I/Os) available on Xilinx field-programmable gate arrays (FPGAs) to excite phosphors, which, in turn, create brilliant, high-resolution pictures (with resolution as high as 4000 pixels) with very fast response,” explains Raju.
In addition to brilliant picture quality, LPD brings the advantage of energy efficiency by using lasers for turning the pixels on or off compared to a conventional display with an always-on backlight.
Mastakar explains, “The innovations in LPD were made possible by developments in the FPGA technology. Advanced high-speed I/Os which can work in the range of 1.4 Gbps, innovative manufacturing processes that merge the advantages of high performance and low power, and integrated architectural blocks like memory controllers and multi-gigabit SERDES in Xilinx FPGAs make system design easier.”
He adds, “LPD is one of the latest technologies in the SED category. It has the potential to replace backlit paper sign boards. It consumes less power, allows for true 180-degree viewing and provides incredible image quality. Quick-response liquid powder display (QR-LPD) is another promising technology targeted at ultra-low-power applications. A few other SED display technologies have emerged in the recent times, but these have not seen much traction in the market.”
Mems-based high-speed mobile displays
Apart from optics and materials, “micro-electromechanical systems (MEMS)-based high-speed mobile displays also form an important category of innovation in recent times,” feels Anup Tapadia, founder, TouchMagix Media.
The nature-inspired Mirasol display technology developed by Qualcomm is one example. This display is based on a reflective technology called Interfero metric Modulation (IMOD) with MEMS structures at its core. It is extremely low power yet highly reflective—the display can be seen even in direct sunlight.
Last year, Hitachi Display demonstrated an MEMS display prototype at CEATEC 2010. Built on Pixtronic’s micro shutter display technology, this device features very low power consumption—almost half that of LCD counterparts. It measured 6.3 cm (2.5 inches) diagonally, with a QVGA resolution of 320×240 pixels. An important feature of MEMS displays demonstrated by Hitachi is that they can operate in three modes—reflective, transparent and translucent. The transparent mode, for example, can be useful for ubiquitous computing or augmented reality applications.
It is hoped that the technology will be commercialised in the last quarter of this year.
Cool, smart displays
The development of displays that consume less power and emit less heat is an ongoing effort. In fact, this is considered to be one of the prerequisites for achieving long-term goals of ambient electronics and ubiquitous computing, where displays and computers will merge unobtrusively with our environment.
“Power consumption is a major issue for large displays (greater than 208 cm) and there is a concerted effort by government agencies and industry bodies to introduce regulation that will monitor the power consumed by existing and newer solutions. Definite progress is being made to rein in the power consumption on most of the existing technologies,” says Raju.
The use of LEDs and OLEDs is a major trend in terms of low-power efforts. Among the newer technologies in the industry, LPD offers a multiple reduction in power relative to other display technologies for the same brightness. Heating, ventilation and air-conditioning (HVAC) and power drops are the other issues to consider. Power consumed by the video controller chips is also a concern. It can be solved to some extent by adopting the latest FPGA chips that bring in power-efficient design features, such as Xilinx Artix 7. Qualcomm’s Mirasol display technology also represents a break-through in terms of power efficiency.
Very recently, Samsung Electronics acquired Liquavista—a spin-off of Philips Research Labs which develops ultra-low-power display technologies. Liquavista’s electrowetting technology, which operates in transmissive, reflective, transparent and transflective modes, enables creation of displays with bright, colourful images along with dramatically reduced power consumption. Offering more than twice the transmittance of LCD technology and operating at low frequencies, displays utilising electrowetting are expected to consume just 10 per cent of the battery power of existing display technologies.
Samsung plans to use electrowetting technology in its mobile products and expects great benefits in terms of power consumption and response times. In e-paper applications, for example, the response time of electrowetting displays will be more than 70 times faster than existing reflective displays, allowing colour video display. If and when Samsung brings out electrowetting-based devices, it will be another landmark in the low-power device market.
Displays that engage, interact
R&D efforts are contributing towards increasing the interactivity of displays—a prerequisite for realising the fantastic dreams of ubiquitous computing. Although real ubiquitous computing is still far away, the industry feels that audience recognition and engagement through interactive displays could be the next major milestone in display technology.
“We believe large displays would no longer be delivering one-way messages in the future. A user will be able to interact with these displays using multi-touch, gestures or even his mobile device,” says Tapadia.
A Pune-based company, TouchMagix is evolving as a major player in the international market for large-format, interactive, multi-touch displays. The company manufactures a new variety of interactive display solutions like Interactive Floor, Interactive Wall, Touch Table (Interactive Table), Touch Window and 3D Magix-Sense. TouchMagix currently exports products to more than 25 countries and serves clients like Nike, Intel, Reebok, Nokia, Castrol, Times Group, Infosys, Merck and Uniliver.
“I feel we are in for a bright future in irregularly shaped displays. In fact, in our company itself, we have an R&D team working on building interactivity for irregular shaped displays,” adds Tapadia.
It seems like the day of ubiquitous computing is not too far off with all these varied improvements in display technology. When the time comes, it will be nothing short of a revolution for it will change the way you interact with the computing systems.
The author is a technically-qualified freelance writer, editor and hands-on mom based in Singapore