Di splay systems

B. Rajesh KumarDISPLAY SYSTEMS Roll no: 12

INTRODUCTION:

Newer display technologies continue to evolve, in synchronism with modern-day convergence devices and systems. However, the general awareness and knowledge about display systems are on a lower level, compared to the hype of related developments in the convergence arena. A concerted port is needed by the diverse fields to develop effective, efficient, and economical display systems.

What are display systems?

Display systems are the focal point of any human-machine interface. Applications range from digital watches, finger tops, palmtops, laptops, mobile phones, digital cameras, PC monitors, and TV’s to public scale hoardings and air-base displays. Related innovations have enabled display systems to synchronize the corresponding advances in micro electronics, IT, and telecommunication fields. The role of electronic displays is becoming increasingly crucial consumer electronics, office automation, information processing, entertainment, intelligent offices/homes, interactive services, teleshopping/conferences, trade-fairs/exhibitions, etc.

Display techniques form an essential component of any industry, be it any manufacturing, process control, education, advertising/marketing, automobile, chemical electronic, nuclear, publicity, public information, or any other area can conceptualize. Trade shows, executions, seminars, etc effectively use electronic displays to highlight their product innovations. Thousands of visitors stroll through the exhibit halls, of which most flock around those booths that offer moving-image display.

Display form a crucial link in the functioning of convergence systems. Product manufacturers can easily capitalize on these systems. All it takes is a little more bragging on their part.

Technique behind Display Systems:

Electronic devices convert electronic signal information to specific locations on display screens. Each location must adjust to the requisite brightness and colour for that portion of the image. Display systems use a wide range of modalities categorized mainly into direct view

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and projection systems. Direct view systems enable the users to view the display screen directly. Projection systems first create the image on an internal screen, subsequently using optical devices to magnify and project images onto a larger external screen.

These displays can also be classified as light-emitting and non-light-emitting devices. Light-emitting devices include cathode-ray tubes (CRT’s), electroluminescent (EL), plasma display panels (PDP’s), vacuum fluorescent displays (VFD’s), field-emission displays (FED’s), and light-emitting diodes (LED’s). Non-light-emitting displays include liquid crystal displays (LCD’s) and electro chromic displays (ECD’s).

Industry Scenario:A sampled interaction with the display industry reveals

interesting aspects about this seemingly innocuous and taken-for-granted field.

S.K.Garg, president, Super-Vu International, a leading domestic player and exporter, emphasizes that the display technology is changing very fast. Obsolescence is very fast. For instance multimedia data projectors marketed by Indian companies get outdated in only 3 to 6 months. An SVGA model is outdated in six months, since it can be upgraded using technology available, Plasma displays, developed by America and Japan, are expensive. These support only VGA video inputs, and cost Rs. 5,50,000 per unit. Super Vu has developed a 114cm Plasma Vision display system that costs only Rs 75,000. This simple system integrates flexibility of up gradation and transportation.

India is a vast untapped market for display systems. Mr.Garg is of the opinion that, both in terms of quality and cost, we can complete with imported versions. We have the capability to design and manufacture large video walls at half the cost of imported models. The company has a development facility to design and fabricate sophisticated optical systems for any application. Based on the feedback and techoeconomic requirement, display systems have been developed for various applications.

‘Plasma Vision’ (compact, portable rear-projection monitor), ‘Display Vision’ (standalone large-screen, rear-projection monitor), ‘Movision’ (portable, powerful, high-resolution display), ‘Media Vision’ (large-screen interactive multimedia presentation tool), and ‘Video wall /

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Video cube’ (large screen display) are some display products that have good demand in the domestic and global markets. Applications include showrooms, corporate presentations, simulators, command and control centers, large drawing-rooms, halls, exhibitions, heavy-traffic public places, and training sessions.

There are few Indian companies with the requisite infrastructure to design and develop, or even assemble, a complete range of projection systems. R.D. Vaghela, CEO, Infra Control Systems, reveals that the trend worldwide is to use smart display systems that can be activated by pager networks at specified time for advertisement booking time-slots. In European countries displays depict news flash of important events, weather information, etc.

These are used in factories for production data analysis and display of MIS (Managerial Information Systems) information pertaining to number of parts to be produced per day, actual production, and rejected parts. In the assembly line, time taken by technicians in each zone is displayed. If it is longer than the stipulated time, reason for the efficiency or any mechanical problem of the assembly is found and rectified. Common usage areas include stock and commodity exchange update, manufacturing / warehouse data management and employee and safety communications in large facilities.

Corporates use displays with RS48 interface, enabling 255 displays to be attached to one computer. Centralized computers transfer data to various locations, according to ID number given to each display. Same message can transmitted to all displays in emergent situations. Displays can accept pager situation data. Display messages can be entered by wireless remote control keyboard, computers using dedicated software, and paging date receivers.

Personal priority display (PPD) is popular abroad. Specifically designed for high-priority desktop messages, it communicates critical, time sensitive information to workstations. It is statically placed inside helpdesks in customer service workstations / cells, office and lobbies, so that critical data is immediately and easily available.

In India, displays are mainly use passing general and online information. Power utility companies display online production data and

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related crucial parameters. Mr.Vaghela explains that Indian industry is installing silent message displays and studying their impact on viewers. Displays are ideal communication tools.

Jayant Shah, partner, Automobile Industries, leading manufacturer electronic displays, feels that there is need to increase public awareness usage of this technology. Since 1999 electronic displays have been a vital display communication media over the world. Automotive Industries has developed innovative LED displays, signs and calendar clocks.

Indian electronic display industry is growing. Industries use displays for production and safety signs. Displays on roadways communicate civic messages and advertisements. Sunil Shah, partner, Jaydeep Industrial Corp., reveals that companies prefer to install LED displays that are more economical than LCD and plasma, Mr.Shah laments that the sales of display products are affected by high sales tax. As more corporates and government organizations are using display systems, there is a scope for growth. The display industry should take care to develop quality products, to sustain this growth.

TOUCH-SCREEN DISPLAY:

Touch systems as GUI(graphical-user interface) devices for computers continue to grow in popularity. For many applications such as ATMs POS (Point-of-sales) systems, industrial controls, and handheld computers, touch screens are an essential user interface, not just a keyboard alternative.

The touch system comprises touch sensor (to receive the touch input), electronic controller (to read and translate the sensor input into a conventional bus protocol; for example, serial USB), software driver (to convert the bus information to cursor action), and system utilities, Vacuum-deposited transparent conductors serve as the primary sensing element in both capacitive and resistive touch sensors- the two most common touch sensors.

Touch systems using resistive sensors account for 56 per cent of the touch market, with 43 per cent going to high volume consumer applications. These applications predominantly utilize ‘pen input’; for

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example, PDAs. Premium applications, such as retail POS, or those where glove input is most frequent, such as medical and clean-room displays, make up the balance of the resistive market.

Capacitive touch systems account for 25 per cent of the global touch market sales. Known for their durability, reliability, and fast response, those sensors service public-access touch-screen applications, such as information kiosks, ATMs, and casino gaming. These systems activate with either human finger touch or an electrically active tethered pen.

Touch systems represent a rapidly growing subset of the display market. Palas Software and Micro touch, USA, have pioneered usage of state-of-the-art ‘Micro touch’ screens in India. Micro touch, Boston, is a world leader in touch technology. Its patented ‘ClearTek’ touch-screen is sensitive. It registers the lightest touch, with high resolution, and requires the shortest touch contact. It is the only technology unaffected by dust in the world, which makes it ideal for Indian conditions.

Other touch-screen innovations include intelligent pen-and-touch input with ‘TouchPen’, ‘Tek resistive’, and ‘Thru Glass’ systems. Use of touch-screen installations is increasing in India. Applications include games / entertainment, industrial / medical instrumentation, financial trading, ATMs, POS terminals, retailing kiosks, multimedia kiosks, etc.

Micro Touch has a major share of the global touch-screen market. Rajiv Srivastava, director, Palas Software and Micro touch India, predicts touch screens will be the future input interface for computerized systems. The worlds over these systems are being utilized as user friendly interfaces, obviating the need for computer and keyboard skills. In the Indian context, people with low literacy levels can benefit from the system.

Public information systems, such as railways, use these systems for booking offices. Travelers can confirm reservation by touching the ‘PNR number’ location on the screen. Even illiterates can use and benefit from the system. Touch screen can be sued for accessing information in any language. Bill Gates, chairman, Microsoft, predicts that it will emerge as a vital computer interface.

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‘ClearTek’ touch-screen uses analogue capacitive technology- the only touch technology based on sensing electrical signals. It has a resolution of 1024 x 1024 touch points. The controller averages the entire area of finger contact to a single point, giving users pixel by pixel control.

ClearTek also provides the fastest response of any touch-screen, with a minimum touch contact requirement of 3 cms. This performance offers virtually instant response and makes it ideal for various applications, including gaming and kiosks, where environmental robustness is a necessity. Most public access kiosks in India use ClearTek.

Thru Glass is a revolutionary concept in computer input devices, based on a patented projected capacitive touch technology. It can detect a touch through 2.5cm thickness of glass, plastic, or non-conductive protective materials. This versatile technology can be used with multimedia system installed in environmentally controlled kiosks to create vandal-proof, unattended, outdoor application.

For the rigid demands of a factory floor, Thru Glass is the perfect solutions capable of being activated with any conductive input device including glove hands and metal tools. Impervious to rain, snow, chemical and sunlight, brings the power of touch into new environments.

‘TouchPen’ is a proprietary capacitive digitizer using Micro Touch’s analogue capacitive touch technology. It is only technology that can distinguish between touch and pen input. It works by generating a uniform low-voltage field over the sensor and determines the touch location in the same way as the analogue capacitive screen does. A pen location is determined when the pen injects current onto the conductive surface. The touch contact requirement 3 cms. The response speed is 8 to 15 cms and 200 points per second in pen model.

With a resolution of 2048 x 2048 touch points, the digitizer is fast and precise enough for signature capture, image manipulation, and annotation. It is offered as a standard option with an analogue capacitive kits and monitors.

Shonkh Technologies has developed information kiosks with LCD/CRT touch screens, adding power to interactivity. Basically, a kiosk is an information centre. It can be a standalone system connected to a server, or

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to the Internet, enabling users to access the information bank. Kiosks have bridged the gap between the computer-literate and the non computer-literate individuals.

LASER IMAGING:

A German company has developed laser imaging technology, endowed with best colour properties. Laser display projections obviate the need to focus the protector to adjust for the distance between the projector and the screen. These provide clear, non-reversed images on the screens of any size. Laser beams travel over the screen incredibly impact, creating on it a succession of images made up of pixels and lines. The pixel and frame rates are the same as of the common video standards.

The laser imaging method can use signals from all standard norms, included analogue, digital, and HDTV, readies of whether these are received an aerial or video recorder.

The multisync and multimedia capabilities of laser projections make them for events, shows, exhibitions, and conference rooms. A small projection head attached to the ceiling in a domestic living room can beam life-like video images measuring 1.5 m (diagonal) at an angle from one of the walls of the room.

ORGANIC EL DISPLAYS:

Most flat panels in the market are LCDs. But LCDs are essentially non light-emitting devices. This imposes technical limitations on the quality of ability they offer. So, the display industry is forced to continue R&D efforts for displays that emit their own light. Such displays include PDPs, FEDs, and EL displays.

Organic electroluminescence (EL) displays, in addition to emitting their own light, provide wide viewing angles, feature a strong contrast, and deliver a quick response speed. These possess strong characteristics in areas where LCDs are weak. These use fluorescent organic compounds as luminescent materials.

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Researchers at Tohou Pioneer Corp., Japan, experimenting with compounds having low molecular weights, developed element technologies necessary to create organic EL displays. They brought out an organic EL display for car radios. To form devices made of low molecular weight compounds, vacuum evaporation techniques are used to deposit organic compounds with different carrier transport factors between electrodes possessing different work functions. Glass or plastic film substrates use indium-tin oxide (ITO) as the positive electrode, with a high work function of 5.0 eV, performing as a hole injection electrode. The EL devices basically consist of cathode (Li-Al or Mg-Ag), electron transport layer (Alg3), emission layer with dopant (Alg3, quinacridone, or coumarine), hole transport layer (amine-based compound), anode, and substrate.

The advanced organic EL dot-matrix device developed by the company has green monochrome display section with 265 x 64 dots and single-matrix drive structure. The displays have panel and drive circuit sections. The resulting display, with superior brightness, contrast, and visibility, can be viewed at any angle. To take full advantage of the self-emitting characteristics of EL devices, the external light is blocked, preventing it from entering the panel and reducing contrast.

Researchers continue to seek ways of making organic LEDs more efficient and longer lasting. They have succeeded on both counts by using new materials and by combining materials is new ways, creating displays lasting 10,000 hours and delivering a luminous efficiency of 12 lumens per watt.

Organic EL displays find usage in the display section of Pioneer’s vehicle use FM teletex receivers. Demands are on the increase from manufacturers of car stereo systems. These displays will also be supplied for various other devices, including PDAs.

LEPs:

LEPs are flat, wall-hanging displays that are produced using plastic layers. These were invented by Richard Friend, University of Cambridge, in 1989. Cambridge Display Technology (CDT) demonstrated the first LEP-based monochrome flat TV screen in 1998.

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LEPs operate on supply voltages of 3V and less, with wide viewing angles. This light-emitting device is a layer structure deposited on a transparent substrate. The substrate is coated with a transparent conducting layer, ITO, which is used as a hole injector. ITO has a rough surface relative to LEP. It is coated with a conducting polymer. The second electrode (a film of calcium over laid with another film of aluminium) is deposited on the LEP layer, completing the sandwich structure of the device. Electrons and holes, injected into the LEP from cathode and anode, recombine to form excitons that radiate photons during decay. The band-gap and colour emission can be varied through the visible light spectrum (from blue through the red).

CDT has linked up with Seiko-Epson, Philips, Hoest, Seiko, and DuPont, to undertake development work on various aspects of LEP-based display. Philips is introducing multi colour displays for mobile phones, while Seiko is working on a large-area flat screen with full-colour video display.

VIDEO DIGITAL INTERFACE

An industry working group, led by Intel and backed by Compaq, Dell, Fujitsu, Hewlett-Packard, IBM, NEC, Microsoft and Silicon Image is developing a digital interface technique. This technique will eventually link consumer electronics, PCs, or any host system to digital display.

Unlike CRTS, flat-panel displays are inherently digital. Every pixel is individually addressed. The display requires matrix-addressing circuitry. Unfortunately, most flat-panel monitors in the market today are connected to the PC via the VGA video monitor port. The VGA analogue outlet socket at the back of every PC delivers analogue colour RGB signals, which in turn, drive a CRT. For flat-panel displays, the signals are, however, reconverted into digital format through A/D conversion process. This double conversion process degrades image quality and ads cost. A better solution is to keep the video signal in digital format throughout.

The superior image quality of active matrix LCDs in the latest notebook computers is due to the use of a digital link between the PC motherboard and the display. But notebooks are closed integrated systems where compatibility between manufacturer’s motherboard and display is not

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an issue. Before the same image quality is achieved in the desktop PC, the industry needs a digital video interface technique that permits operation in an open system environment. By combining the digital video interface standard with the latest generation of digital displays, system designers can enjoy the benefits of super image quality, lower system cost, increased ease of use, and the ability to transmit images over long distances.

LCDs:LCD is a passive device that manipulates existing light to

produce an image, whereas active displays (CRT, plasma, and LED) emit light. Consequently, it consumes low power and, therefore, is the preferred choice in portable and other battery-powered applications.

Touch-screen LCD (TSLCD) modules incorporate drive electronics and touch panel logic to display data, scan touch panel, sense operator inputs, and output digital data to a control program. The touch-panel portion of LCD can be programmed to display a variety of data, such as alphanumeric, ‘QWERTY’ keyboard, icons, and other graphics. Touch panels use capacitive or resistive sensor technology. Increased display luminance, increased viewing angle by using better aperture ratio, new substrates, better backlights, etc are the current trends.

PCs equipped with thin-film transistor (TFT) LCDs were the first to be noticed. Subsequently, TFT colour LCDs helped stimulate the widespread use of notebook computers incorporating such displays. Advances in TFT LCD manufacturing techniques further contributed to the spectacular spread of notebook computers. These modules continue to develop for use as monitors for desktop computers and workstations. These are appearing as terminal displays in banking institutions, stores, desktop publication, and computer-aided applications.

The demand for LCD panels for use in cell phones is expected to raise sharply after the launch of 3G mobile services, providing data and full-video transmissions. Japanese electronic giants are beginning to produce LCD panels for use in cellular phones, to cash in on their rapid demand fueled by 3G cellular phone services. Toshiba, Sharp, Seiko Epson, NEC, Casio Computer, etc are some of these.

Hitachi started producing colour power-saving STN (super twisted nematic) LCD panels for cells phones and is now developing TFT

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LCD panels that can display full-motion video. The global market for TFT LCDs will continue to expand, boosted by Philips Electronics NV and LG Electronics. The two companies formed a successful joint venture last year, to pool their CRT activities. The venture will combine all CRT activities and key components, as well as the glass activities and plasma technologies of both the firms.

VFDs:Invented in 1966, VFDs have been in the market for 34 years.

These versatile displays have gone through continuous improvements in their technology, and are used in many devices and systems. Application area includes automation, telecom, medical, home appliances, vending machines, point of sale, public information systems, and calculators.

VFDs are amenable for small-size production and reused widely as chip on-glass displays, especially for automotive applications. Super VFD tubes consume low power and obviate the need for backlighting. Tube structures are being improved to offer better viewing angles. Multicolour displays use modular techniques and apply strips of different phosphors.

FLAT DISPLAYS:

The three flat-panel displays active matrix LCDs (AMLCDs), plasma-addressed liquid crystal (PALC) display and PDPs-can be classified into light modulators or light emitters. AMLCD and PALC displays are examples of the former, in which the functions of light generation and light modulation are separated. Light modulation is accomplished via a voltage-controlled change in the polarization of light passing through a liquid crystal. A separate backlight provides the illumination. PDPs, light generation and modulation functions are combined by mechanisms whereby variable amounts of UV light are produced, which stimulate the phosphor to emit visible light.

The AMLCD is a mature technology, with a large manufacturing base and established production infrastructure.

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POLYSTER PANELS:

Polyster is the likely choice for future flat-panel displays. Researchers have developed thin-film transistor displays out of polyethylene terephthalate thin, flexible and rugged plastic can be rolled up, folded, or bent it practically any shape desired.

The concept holds promise for a future generation of ultra-light, flexible, cost-effective displays. Applications include notebooks, desktops, video-games, machines, and non-conventional displays. Roll-up displays, displays set into clothing, paper-thin electronic books, and newspapers are some of novel innovations.

3D DISPLAYS:Unfortunately, 3D displays have not measured up to

expectations. In some cases, viewers must wear special glasses to have their viewing system restricted. However, improvements are in the office, with medical and business devices consisting glassless technologies.

Splitter system is used in amusement applications, and will find more applications as LCD price falls and picture quality improves. Double-image splitter system is used in business applications, binoculars, and stereoscopic emission tests. Medical field is considering the use of 38 cm display as monitors for brain surgeries and endoscopic operations. This display uses head-tracking technology that detects the viewer’s head and displays optical image accordingly.

‘Stereoscopic Vision’ technology for presenting 3D images incorporates an inversion technique called modified difference. Another system computed-image depth, effectively converts still 2D images to 3D. This system separates each subject using colour components of the screen, and then estimates the depth of each section of images, depending on the contrast, sharpness of each subject, and structure of the scene.

The imaging technology department at Sharp Laboratories of Europe has developed ‘twin-LCD’ display concept. It is based on two TFT LCDs. The images of these LCDs are superimposed by a half-mirrored beam computer. The optical arrangement creates laterally displaced images at the nominal observer position. Each LCD panel displays one of the stereo pair

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images, enabling the observer to view the images without wearing special glasses. Twin-LCD concept, using TFT LCDs with a controllable illumination system, has been used to show high reality auto-stereoscopic 3D images with observer tracking over a wide angle and image look-around.

OPTICAL FIBRES:

Optical fibre, widely known as a telecommunications transmission medium, can be used for large displays in public places. Such display systems consume relatively little power and deliver high contrast, non-glare visuals in lighted settings.

As multimedia techniques progress, the market requirement of information displayed at public locations tends to shift from communication of data using characters to that using images. To communicate information, the image should be large with full colours. The multi screen method is widely used to produce a large display. A number of display units (LCDs, CRTs, or projectors) having a certain size are assembled to form a large-display screen. However, the drawback of these display systems is that seams are present between the display units.

Advantages of optical fibre display systems include large seamless screen, high design flexibility, and easy installation and movement. These are best suited for public facilities, conference halls, ongoing games at stadia/gymnasiums, advertisements, airports, and railway stations.

DMDs:

Invented in 1987 by Texas Instruments, USA, digital micro mirror display (DMD) is a reflective optical conversion device that features bright projected image, with high contrast, narrow beam between pixels, high resolution, and excellent colour reproduction. It uses digital light processing (DLP) technology.

DMD is fabricated on CMOS SRAM, using micro machine technology based on conventional 0.8 um wafer processing. This display integrates electrical, mechanical, and optical functions on a single chip.

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Thousands of 16 um2 Al mirrors are formed on a chip, at a chip, at a pitch of 17 um. The mirrors reflect light in one of two directions, +100 or -100

relative to the substrate surface, depending on memory outputs. DMD is combined with a light source and projection system. When it is applied in a DLP optical system, light enters the DMD at 200. In ‘on’ state, the mirror projects the light to projection lens and the pixel projected onto the screen appears bright. In ‘off’ state, the mirror reflects lights at 400, missing the projection lens. The pixel then displayed is black. The system employs binary pulse-width modulation (PWM) technology. The DMD switches the micro-mirrors ‘on’ and ‘off’ at switching speeds of 10 us to generate bursts of optical digital pulses that appear to the viewer as a level of brightness between fully bright and totally dark.

DMP technology can be used in business, consumer, or commercial applications. Business applications include front projectors for conference room and workgroup presentations. Consumer applications include rear-and front-projection TVs.

CONCLUSION:

The display field is vast. Newer display technologies continue to evolve, in synchronism with modern-day convergence devices and systems however, the general awareness and knowledge about display systems are on a lower level, compared to the hype of related developments in the convergence arena. In order to capitalise on displays that match modern devices, a concerted effort is needed by the diverse fields to develop effective, efficient, and economical display systems.

REFERENCE:

ELECTRONICS FOR YOUJanuary 2001

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