Technology Focus November 2010 Displays

TECHNOLOGY FOCUS NOVEMBER 2010 DISPLAYS

Nature has been reenergised and strengthened in print and online. Now it’s even easier to stay abreast of the most important developments in science, and those that matter most to your scientiﬁ c career.

Nature’s new modern package includes opinionated editorial content, vivid page layouts, improved navigation and mobile apps that position us, and you, at the center of the scientiﬁ c discussion.

Don’t miss another week. Rediscover your Nature today.

nature.com/rediscover

© 2010 Macmillan Publishers Limited. All rights reserved nature photonics T: +1 415 403 9034 SIMON AD T: +1 415 781 3804 GEORGE AD T: +81 3 3267 8751 K S T A J CO C p Ol NADYA ANSCOMBE EDITOR [email protected] F: +81 3 3267 8746 T: +81 3 3267 8751 162-0843 Japan Ichigayatamachi, Shinjuku-ku, Tokyo Chiyoda Building 2-37 NPG Asi to interact withthedisplayed content. infrared tough-recognition, allowing users combines holographic projection with Light Blue C AMES OM A ROD EN h RT O I l RIS v p v v v M ES

Y EDITOR ER W EDITOR ERTISING ERTISING E

u GI IKAMI

r imag A All BA G I CTION l

S ll l CCO RAYDON SON A u

x o OC -P ARDICE TER I ptics’ pico projection system

h u cific

MANAGER DIRECTOR E EDITOR

|VOL 4| NOVEMBER 2010 |www.nature.com/naturephotonics M ANAGER

D © display technologies, but for also LED growth opportunity, not only for new big a are e-readers that Display,believes president for of Information Society the a larger screensize. Munisamy Anandan, colour,full have better contrast or feature deployment of improved versions that are and consumers are eagerly awaiting the low-power displays is now bigger than ever, turningwhen apage. The demand forthese bistable nature —power is only needed different to types ofdisplayother their is on holiday. What displays makes these after its founder ran out books to of read page 748),acompany(see that started display developed by technology E feature ablack and white electrophoretic and battery life. Most of devices these optionpractical in terms of their readability a readers e-book made has that technology ofthose hardback and books, it is display of havesales e-books now exceeded ofstory 2010.According to Amazon.com, areelectronic (e-books) success books the as kitchen appliances. Without adoubt, traditionally never featured screens, such includedbeing evenon that objects have

2 0 10

M lives, with electronic displays now of our aspects in almost all daily isplay technologies found can be a g c m CONTENTS i l l a n

P reat expectations u b l i s Interview withMunisamy Anandan Watch this space iN Outdoor white P David Vettese Microdisplays: Adrian Cable p iN Emergence ofthee-book P Our choice from therecent literature Rese Industry-wide Busi h e ico projectors: R R r s te dust

oduct hi ofile L nature photonics i m N i R AR t e view d ess .

A ch hi R l l r y i g l N h

l CD price cuts,AMO P t Ink Interactive experience s EDs, despeckledlasersystems andmore iquid crystal onsilicon ews

e r G e G s R e hli r s hli v e P d ective G

G hts growing opportunity for microdisplays your desktop at work. project an interactive presentation onto choosing items the you want by touch, or projecting website the onto table the and you could doyour internet shopping by requirestechnology little imagination — applications for such an ingenious Finding 750). page (see content projected that allows users to interact with the to make apico projection system infrared touch-recognition technology holographic projection with technology Light Blue Optics has combined enabling other innovative applications. rendering of LCDs. improve power the efficiency and colour page help 756),which backlights (see to displays be? will Who knows what next the applications for technologies are constantly emerging. andmedical movie industries. applications including military, inthe its products are now inavarietyof used Display pioneered technology, this and page 752).UKcompany Forth Dimension onmade silicon using (see liquid crystal hts The pico projection market is also a also is market projection pico The New display technologies are also Displays and are new everywhere, l

ED displays andmore

TEC h NO l O gy f gy

OC 750 748 746 756 755 752 747 u 745 S

business news technology focus

LCD manufacturers face price crisis

fter months of price cuts, manufacturers Aof large-size liquid-crystal displays 60,000 (LCDs) are under pressure to reduce panel LCD-TV panels prices further, following a major build-up of LCD-TV set inventory. A recent report from US business analyst iSuppli revealed that the second quarter of 2010 saw the manufacture of 52 40,000 million large (ten inches and above) LCD television panel shipments, but the sale of only 38.7 million LCD television sets. The resulting imbalance between supply 20,000 and demand is having a strong impact on the sector. “This gap is higher than anything seen in 2009. Over-supply persisted in shipments (thousands of units) Total the first two months of the third quarter 0 9 0 0 -0 -1 -1 as buyers cut orders in July and August,” Q1 Q1-09 Q2 Q3-09 Q4-09 Q2 says iSuppli analyst Sweta Dash. “LCD isuppli television brands are expected to lower prices more aggressively to reduce their An imbalance between supply and demand is causing prices to decline in the large-panel LCD industry. inventory levels, thus putting mounting pressure on panel suppliers to reduce and help to steady panel prices by the end of iPhone, iPad and other competing prices further.” the fourth quarter of 2010. products,” explains Jakhanwal. Dash points out that manufacturers of At the same time, rapidly rising sales of “Smart phone manufacturers are now monitor and notebook panels have been smart phones and tablet PCs are predicted adopting TFT LCDs that use in-plane reducing supply to mitigate excessive to see the global market for small- and switching technology, which supports inventory levels, and that panel prices are medium-size thin-film transistor (TFT) a wider viewing angle and better now stabilizing as a result. In contrast, LCDs expanding at its fastest pace for picture quality than a conventional high depreciation costs at relatively new three years. According to analyst Vinita LCD.” But the fast-paced market LCD television panel fabrication plants Jakhanwal, also from iSuppli, global expansion probably won’t last, predicts mean suppliers have been less willing to shipments of TFT LCD panels are set to rise Jakhanwal. “Growth in TFT LCD reduce production. by 28.1% in 2010, from 1.8 billion to 2.3 shipments will slow in 2011 and However, Dash predicts that the billion units. beyond as the expansion of smart potentially strong sales of LCD television “Sales of smart phones and phone and tablet markets cools to more sets in China could reduce inventory levels tablets are booming thanks to the normal levels.” smart phones speed AMOLED technology rose in popularity market. Led by former LG Electronics AMoleD take-up after its integration into mobile phones vice president Jong-Uk Bu, Nanosys manufactured by Samsung and HTC. In Korea will develop ‘architected materials’ The adoption of touch-screen technology the first quarter of 2010, the average screen for Asian electronics manufacturers, in the mobile phone industry is fuelling the size for an AMOLED display exceeded including high-performance LED demand for active-matrix organic light- three inches, which is larger than that backlights for displays and silicon emitting diode (AMOLED) displays, reports of competing TFT LCDs. Taiwan-based composite anode materials for use in US market research firm DisplaySearch. display manufacturers AUO and Chimei lithium–ion batteries. Earlier this year, AMOLED displays have been the only Innolux are scheduled to start mass- Nanosys unveiled QuantumRail, quantum- technology in the mobile phone display producing AMOLED displays in 2011. dot-based LED backlighting units that market to increase revenues every quarter Hsieh believes AMOLED technology improve LED backlit display colour this year, as both unit shipments and will now see increased year-on-year gamut and efficiency. Nanosys says that average prices have risen. “With an average growth, although TFT LCDs will still ship its quantum dot LED technology makes worldwide market penetration of mobile more units. it possible to deliver saturated red, green phones at 70%, manufacturers are eager and blue colours that exceed the NTSC to introduce new features such as touch- nanosys unveils Korean facility 1953 guidelines for displays. This latest screens to ensure continued growth this announcement follows collaborations with year,” says Calvin Hsieh, research director at US-based quantum-dot and materials Korea-based electronics manufacturers DisplaySearch. “The success that AMOLED developer Nanosys has opened a new LG Innotek and Samsung Electronics displays are finding in high-end smart facility in Gyeonggi-do, Korea, to support to develop display products based on phones reflects these trends.” its recent expansion into the Asian quantum-dot crystals.

746 nature photonics | VOL 4 | NOVEMBER 2010 | www.nature.com/naturephotonics

Private viewing To minimize sticking, Tae and his colleague it passes through a microdisplay and is Opt. Express 18, 3143–3148 (2010) treated the MgO layer of a 50-inch, high- projected on a screen. Tatsuo Uchida and definition, alternating-current PDP with colleagues from Tohoku University, Japan, radiofrequency plasma. Experiments with performed experiments to determine how several gas compositions indicated that speckle is reduced using such a set-up. They Analyser treatment with an argon plasma was most identified two occurrences of speckle in the effective at preventing impurity build up. system, the first at the rotating plate and the BPLC layer “Organic matter on the MgO layer was second at the screen. Further investigations remarkably reduced compared to the panel revealed that when the plate was rotated, that didn’t have this plasma pre-treatment,” the granular pattern of speckles generated LCD and compensation ﬁlm says Tae. “The display luminance difference there corresponded to coherent regions of was considerably reduced, meaning no the secondary speckle, at the screen. The Polarizer temporal image sticking.” Tae asserts researchers then measured the speckle that the plasma treatment can be used contrasts at the screen by changing the degree Backlight on a commercial scale. “Thanks to fewer of granularity of the primary speckle. impurities, the treatment considerably “In every case, as granularity increased, the A new method of controlling the viewing reduces the panel ageing time,” he said. “This corresponding speckle contrast increased,” angle of a liquid-crystal display (LCD) would reduce the cost of a PDP panel despite says Uchida. “This shows the degree of promises greater privacy to users of mobile radiofrequency plasma equipment costs.” granularity of the primary speckle is the key phones and laptops. By inserting a blue- parameter in speckle generation on the screen, phase liquid-crystal (BPLC) layer into an fast e-book readers and can be used as a unified index when LCD, Shin-Tson Wu and colleagues from Appl. Phys. Lett. 97, 023514 (2010) discussing speckle reduction effects.” the University of Central Florida, USA, were able to tune the viewing angle of the Researchers from the University of Cincinnati, floating 3D images display continuously when adjusting an USA, have demonstrated, for the first time, J. Soc. Inf. Disp. 18, 519–526 (2010) applied voltage. a colour electrowetting display device based Lens array According to Wu, the BPLCs have on a vertical-stack pixel structure. Producing Display submillisecond response times, enabling the higher resolution images than conventional Lens 1 user to switch from a wide viewing angle to layouts and with typical switching speeds of Lens 2 a narrow one quickly. The BPLC layer is also 10 ms, the design holds promise as a display for easy to incorporate, as it is simply inserted video-compatible colour e-book readers. Most above or below the LCD and does not e-book readers use low-power electrophoretic require an alignment layer. Simulations were displays, but their low switching speeds are performed on a nematic in-plane switching not compatible with displaying animation and cell, but Wu is confident that the set-up will video. In contrast, the electrowetting reflective operate in all display modes without affecting display offers video-rate switching speeds, transmittance. “As long as the LCD is initially although current designs require the use of an well compensated, the viewing angle can overlay colour filter, limiting resolution. Now always be controlled by the applied voltage of Andrew Steckl and colleagues have adopted Floating image displays typically use a single the inserted BPLC layer,” he explains. “This an approach in which three pixels, filled with large lens or two closely located Fresnel method has a larger aperture ratio and higher coloured oils, are stacked on top of each other. lenses to create a 3D image that literally optical efficiency than other techniques, Arrays with as many as 1,000–2,000 pixels floats in front of the viewer. However, plane although we now want to widen the tuning were fabricated. “The device has smaller projections suffer from barrel distortion, range and lower the operating voltage.” effective pixel sizes than conventional layouts, looking curved. Researchers from Chungbuk leading to potential higher resolutions,” says National University, Korea, have now devised Image sticking Steckl. “We don’t need colour filters, which a ‘double-floating-lens’ system, in which Appl. Phys. Lett. 96, 043504 (2010) is a big plus, but must have good vertical the distance between two lenses is equal to alignment between pixels.” The team says the sum of their focal lengths. According to Plasma display panels (PDPs) suffer from that it now plans to improve colour saturation Nam Kim and Jae-Hyeung Park, this set-up temporal image sticking, whereby a faint using different dyes. “We also want to develop compensates for barrel distortion and ensures outline of a previous image remains visible larger arrays and use flexible substrates for the constant magnification across the image. The on the screen after the image has changed. e-book reader market,” adds Steckl. researchers also combined the lenses with Researchers from Kyungpook National a 3D integral imaging display, comprising University, Korea, have now identified why speckle reduction a liquid-crystal display and a lens array, this happens and how to stop it. J. Opt. Soc. Am. A 27, 1812–1817 (2010) to display images in full colour. “Previous According to Heung-Sik Tae, temporal systems have tried to compensate the image sticking is due to organic impurities Rear-projection laser displays deliver distortions and non-constant magnification that remain on the MgO protective layer in the colourful images with unprecedented by applying pre-distortion to the integrated PDP. The vacuum ultraviolet discharge during resolutions, but ‘laser speckle’, an interference images. This has not been effective so we PDP operation dissociates the impurities into pattern generated at the screen, has delayed developed a system to eliminate distortions carbon and hydrogen, and the hydrogen then commercial adoption. A recent method optically,” says Park. The researchers are now combines with oxygen from the MgO surface reduces the problem by using a small working on expanding the viewing angle of to form water, which causes the sticking. rotating plate to diffuse the light before the system. nature photonics | VOL 4 | NOVEMBER 2010 | www.nature.com/naturephotonics 747

© 2010 Macmillan Publishers Limited. All rights reserved profile technology focus emergence of the e-book Electronic books have really begun to take off in the past few years. siân harris finds out about a display company that has helped this to happen.

A decade and a half ago, Joe Jacobson, the pieces onto the same types of backplane a professor at Massachusetts Institute of electronics that are used for liquid-crystal Technology (MIT), was enjoying a relaxing displays (LCDs). holiday when he realised that he had run E Ink’s initial applications were in areas out of books to read. Although this is a fairly such as signage and wrist watches, where common situation that many are familiar there was already a market for power-efficient with, Jacobson’s response to it was not. The displays. However, the company did not idea that struck him on holiday was that forget its original goals, and in 2004 decided of a book that could refresh itself with new to focus on the e-book market, despite that content, and so, when he returned to his lab market not really existing at the time. after his break, he began work on a concept The market immaturity was illustrated he called ‘radio paper’. in 2005, when E Ink entered a partnership In the past couple of years, Jacobson’s idea with Sony to help the Japanese company has become a reality on a grand scale with make its first e-book reader, the Librié, which electronic books (e-books) achieving mass was launched only in Japan. Unfortunately, market success. The Sony Reader, Amazon as Peruvemba conceded, this product was Kindle, Hanvon WISEreader and Barnes & not successful. At the time, there was little Noble Nook are all now best-sellers for their content available and not much awareness of respective companies. However, when the electronic reading. In addition, broadband company E Ink, which designs the paper- access and wireless technology were not as zon like displays used in the majority of today’s A advanced as they are today. However, E Ink e-book readers, was established on the basis Am and Sony did not give up, and launched an of Jacobson’s work at MIT in 1997, such improved version of the product worldwide products and the accompanying market were in 2006–2007 to a much better response. little more than a holiday dream. The Amazon Kindle is one of many successful Today, E Ink’s display technology is found The challenge that the new company e-book readers based on E Ink’s technology. in at least 90% of e-book readers, some 50 initially set out to tackle was to make displays products around the world. that could mimic printed paper. This is Creating displays that mimic printed an important issue if people are going to are the same as the pigments used to paper is not without its challenges, of course. comfortably read whole books electronically. make paper white, and the black particles Improving contrast was a key target for the As Sriram Peruvemba, vice president of are the same as those used in ink. Where company. Early versions of the display gave global sales and marketing for E Ink, pointed things differ from printed paper is that the a contrast of six to one, which is roughly out: “There was a US$400 billion publishing particles are electrically charged: one set is comparable to newspaper print. Now the industry producing content that is very positive and the other is negative. When the technology has reached a minimum contrast readable but not changeable and also a very backplane electronics apply voltage to the of ten to one, which is better than that of a big display industry producing LCDs that are microcapsules, one set of particles is driven to paperback book. It is still not the contrast of changeable but not easy to read.” the top of the microcapsules and the other set pages printed on a laser printer, though, and Traditional displays are uncomfortable on goes to the bottom. The particles comprising this is one of the future goals of the company. the eyes if they are looked at for prolonged this ‘electronic ink’ remain in this state until a The company is also working on the periods, because they are backlit. The signal is applied to change what is displayed. technology’s speed of response for changing backlighting also means that they require This means that readers can leave the device the image being displayed. One of the continual power whenever they are on and and return to it a few hours later without criticisms of early e-book readers was that indeed in many portable electronic items the losing their page or consuming any power. In they took too long to ‘turn the page’. “What display is often a power-hungry component fact, E Ink turned off the power to one of its is fascinating with our displays is that even that limits the battery life. E Ink’s aim was to displays in 2001 and the text on that display is with the old versions they actually refreshed commercialize a display that does not need a still readable today. more quickly than users would turn the backlight but instead uses reflected ambient To make displays, E Ink’s microcapsules pages of a print book,” observed Peruvemba. light in the same way that printed paper does. of black and white particles are coated onto “However, when you are turning printed E Ink’s displays accomplish this feat by rolls of plastic with an indium tin oxide pages your eyes are watching your fingers so containing a flat, two-dimensional array conductive layer, which acts as a transparent you don’t notice this time. With an e-book of microcapsules, each of which is just a electrode. These single-microcapsule layers reader you are just waiting so it seems like few micrometres thick — about half the are less than 400 mm thick but can be several a long wait, particularly when people are thickness of a human hair — and contains kilometres long. They are cut into different used to the response times of the LCD white and black particles. The white particles sizes and shapes for customers, who layer screens on their laptops.” The response time

748 nature photonics | VOL 4 | NOVEMBER 2010 | www.nature.com/naturephotonics

Top transparent Subcapsule-addressing enables company has been successful in addressing. electrode high-resolution display capability “There are e-book readers on the market being sold for US$150. In contrast, LCD- Positively Negatively charged white charged black based smartphones sold without network pigment pigment contracts could be US$500,” he commented. particles particles However, he observed that even if the company gave away its displays, e-book Clear ﬂuid readers would still not drop to the desired US$100 price point at the moment. This is because of the many other components ++ + ––– involved in the readers. “There are hundreds Light stateDark state E Ink Bottom electrodes of other components that depend on the display in some way, such as the drivers and In E Ink’s technology, a layer of microcapsules includes oppositely charged black and white particles. microprocessors. Even though these are not Either the black or the white particle rise to the top of the microcapsules, depending on the voltage directly part of the display we are working applied at the backplane. with the semiconductor manufacturers to improve these and reduce the component count. Moving to a system on a chip for E Ink’s displays is currently 250 ms, to frame. This helps the images to become solution for e-book displays improves the although Peruvemba said that the company obvious more quickly and saves power. This performance, reduces the cost and enables has achieved responses in the lab that are ten feature is particularly important for showing animations to be shown on the display,” times faster. “Today we can do animations animations and, in future, for showing video. he said. To that end, E Ink has formed with our displays but not video,” he said. Peruvemba believes that one of the partnerships with semiconductor companies Response times are longer for electronic key markets for e-book readers will be such as Epson, Texas Instruments, Freescale, ink displays than for LCDs because of the e-textbooks. This market brings additional Marvell and Maxim to jointly develop underlying technology. With electronic ink, challenges for the e-book readers and their state-of-the-art integrated circuits that are a the fundamental constraint on response displays. Users want to be able to write on fraction of the cost of previous solutions. time is how fast the particles will separate the device with a pen as well as to use touch Improvements in backplane electronics and settle down. Users can begin to see the input, to highlight pieces of text and take could also benefit these displays in future. image after 60–80 ms but it takes much notes. This can be done using an inductive Currently, each pixel of an E Ink display longer for the particles to settle and the pen and a digitizer, and is being pursued is made up of dozens of microcapsules; image to become clearer. This process is also by E Ink in partnership with the digital pen the resolution is limited by the backplane temperature dependent; the particles take technology company Wacom. electronics. If the electronics could control longer to settle when it is colder. However, Another challenge with e-textbooks is that each microcapsule individually, much greater this can be offset by applying a greater voltage the glass of the display could shatter. E Ink resolution would be possible. when the temperature is lower. is working with partners to develop more The impact of E Ink’s displays is reflected A core part of E Ink’s electronic paper rugged, flexible displays. The company’s in the growth of the company. A year and products is management software, called signage products are already flexible but this a half ago, E Ink had about 100 employees Waveforms, that senses temperature and is more of a challenge with e-book readers and now it employs more than 250. It dozens of other parameters and adjusts the because of the need for matrix displays to be has maintained its roots, though; its head display’s operating conditions accordingly. supported by backplane electronics that are office is just down the street from MIT. The This software also ensures that only the pixels currently made on glass substrates. Flexible core microcapsules are manufactured in that need changing are changed from frame e-book reader displays are currently being Massachusetts, and some of the coating for developed on a pilot scale and the company its roll-to-roll manufacturing process is done hopes they will begin to be mass produced there. However, some coating and some of later this year. the more labour-intensive steps are now done The company is aiming for mass in Taiwan, Japan and China. production of colour displays also by the end Peruvemba is excited about the of the year. E Ink’s colour displays are based on environmental benefits of the shift to the same idea as the black-and-white displays, e-books. “The paper industry is the second and use the same black and white particles in biggest generator of waste water,” he said. the microcapsules. The microcapsules in each “And if you switch to electronic books you pixel are then divided into four subpixels, each could save up to 300 trees depending on how with a different colour filter — red, green, much you read.” blue or white. For the pixel to display as red, He added that there is considerable for example, the microcapsules under the red interest in this technology from the filter need to show the white particles, which developing world. “An e-book reader typically reflect the light, and the microcapsules under holds 1,000 books. Even if there’s only one the other three filters show black. As they use e-reader in a class of children that’s a whole the same underlying technology, the colour library. It could be the biggest market for ❐

E Ink displays have power consumption similar to displays and it’s happening already.” that of the black-and-white displays. By applying colour filters on top of the As with any consumer product, cost is Siân Harris is a science and technology microcapsules, E Ink can produce colour displays. a key factor and one Peruvemba feels the journalist based in the United Kingdom. nature photonics | VOL 4 | NOVEMBER 2010 | www.nature.com/naturephotonics 749

Pico Projectors interactive experience adrian cable

Holographic laser projection technology, combined with infrared touch-recognition technology, enables consumers to interact with a virtual display that can be projected onto a wall or table.

Consumers want smaller and smaller and where the beam is broken, creating hand-held electronic devices, such as in the process an interactive projected smartphones and PDAs, but they also display. The device has its own operating want them to be able to display high- system and connects to wireless networks, resolution multimedia content. This poses effectively operating as an applications a challenge: such content, be it a video, platform, opening up the possibility of photo, webpage or presentation, ideally projecting interactive multimedia content requires a much larger display than the anywhere, without the need for a screen. device can support — typically just 2.5-inch The term holographic refers to the to 3.5-inch diagonal in size. The recent method used to create the projector’s two- influx of ‘pico projectors’ to the market dimensional images. Proprietary algorithms ue Optics aims to address this. These miniature L are used to transform the desired image t B projectors connect to a host device such as H into sets of diffraction patterns, which are a mobile phone or media player and allow Lig shown on a tiny microdisplay. When laser consumers to project the content onto a Holographic laser projection systems enable light (red, green and blue) illuminates the wall or table so that it can be viewed and touch-screen interaction with projected images microdisplay, a projected image is formed shared more easily. such as a virtual keyboard. by diffraction. The first pico projectors appeared in Diffraction patterns are a highly late 2008, and now some 80 brands are on efficient means of forming an image. the market, using a variety of projection They want to edit, comment and share Instead of blocking light, they steer light technologies. These include liquid- content instantly with their social network. to exactly where it is needed and away crystal-on-silicon (LCOS) microdisplays And they expect to do all of this using from where it is not. Forming a high- based on light-emitting diodes; digital touch technology. quality image from a single hologram light processing (DLP) systems, which Pico projectors do indeed free the or diffraction pattern has never been exploit a chip containing an array of content from the small screen of mobile achieved for reasons relating to the microelectromechanical mirrors; and, phones and multimedia players, but they optical physics. An alternative approach more recently, laser beam steering (LBS) can only project the content. The consumer is therefore employed that calculates systems. LCOS and DLP systems form gains a larger viewing experience but multiple approximate hologram patterns, a miniature image on a chip that is then they sacrifice the touch functionality and each of which forms a rough version of the projected, whereas LBS systems direct one interactivity they would have enjoyed if image. When displayed on a fast-switching or more laser beams at a mirror that is they were viewing the content on their ferroelectric LCOS microdisplay and rapidly moved to sweep or ‘scan’ the laser hand-held device. viewed in rapid succession, the eye’s low beam across the projection surface to form Unlike other projection technologies, temporal bandwidth evens out the noise an image. Light Blue Optics’ Holographic Laser and a single, clearly-defined image is seen. The potential impact of pico projectors is Projection (HLP) technology enables By taking advantage of the way the human significant. Market analysts at DisplaySearch the integration of projection and touch eye perceives images, HLP is able to create valued the revenues of this emerging sector technology within a small hand-held efficient, high-quality video in real time. at US$117 million for 2009 and predict it to device (Box 1). Producing images in this way has some rise to over US$13 billion by 2018. The company’s first product is Light distinct advantages over other projection However, in the two years since these Touch, an interactive projector that turns techniques such as conventional LCOS and small projectors were first launched, a any flat surface into a 10-inch touch-screen. DLP, and enables the integration of touch significant change has occurred in the It stands on a table or can be mounted technology. First, HLP creates images with way consumers engage with content. on a wall, and projects the content onto an extremely wide throw angle, enabling Viewing content is no longer a passive the surface immediately in front of it. An very large images to be created at close activity for consumers. With the rise of infrared beam generator casts a fan of proximity to the projector. Conventional social networking, the smartphone, tablet infrared light — invisible to the human projection technologies such as LCOS, DLP computing and the application ecosystem, eye — over the surface of the projected and LBS can only achieve throw angles of consumers increasingly expect to engage image and an infrared camera located in around 40° without resorting to extremely and interact with their multimedia content. the middle of the projector detects when complicated optics. In contrast, HLP can

750 nature photonics | VOL 4 | NOVEMBER 2010 | www.nature.com/naturephotonics

Box 1 | How HLP works

A typical imaging projection system works this calculation would be fully complex noise into the resultant image. Such noise by displaying the desired image on a and no known liquid-crystal material can must be mitigated to maintain high image microdisplay, which is usually sequentially independently and continuously modulate quality. This can be achieved by using the illuminated by red, green and blue light both the amplitude and the phase of a microdisplay to display N independent to form a greater range of colours. The light field. Even if such a material became holograms per video frame within the microdisplay simply acts to selectively block available, the result contains amplitude 40 ms temporal bandwidth of the eye. (or amplitude-modulate) the incident light; components that would absorb incident Each hologram produces a subframe with after passing through magnification optics, light and reduce system efficiency. A quantization noise statistically independent the projected image appears. Conversely, much better approach, and the key to the of the others (the time average is noise-free) holographic laser projection forms the efficiency advantage of HLPs, is to restrict The key to Light Blue Optics’ HLP image by illuminating a diffraction (or the hologram to a set of phase-only values. technology lies not only in the optical design hologram) pattern with laser light. The As a result, when the hologram patterns but also in the algorithms used to calculate image formed in the focal plane of the lens is are displayed on a phase-modulating the phase hologram from the desired related to the hologram pattern by a discrete microdisplay and subsequently illuminated, image. Light Blue Optics has developed Fourier transform. no light is blocked. and patented proprietary algorithms for the The key task in a holographic projection Light Blue Optics’ system uses a tiny, purposes of calculating N sets of holograms system is to compute the hologram that is custom-manufactured ferroelectric LCOS per video frame both efficiently and in real needed to create the image. A reasonable microdisplay to display the hologram time. Crucially, such algorithms can be first guess might be to calculate the inverse patterns. This requires that the hologram efficiently implemented on a custom silicon Fourier transform of the image to obtain phase be quantized to a set of binary chip, enabling high-quality video to be the desired result. However, the result of values, which introduces quantization rendered effectively in real time. create a native throw angle greater than 90°, the projection surface. When the fan is to a range of environments that conventional enabling a 10-inch diagonal image to be broken by one or more fingers touching the display technologies have found difficult to created from a height of just 12 cm, which is table, a camera decodes scatter from the fan reach. Because the virtual touch-screen is roughly the height of a small mobile device to deduce the location of the touch events projected, it is spill proof, fingerprint resistant standing on a table. (which may be single- or multitouch). and as easy to clean as an ordinary table top. Another advantage is that lasers have Light Touch works best with a flat In addition, when the projector is not in a very wide colour gamut, meaning that surface such as a wall or a table for the operation the display completely disappears. colours appear incredibly rich and vivid. touch functionality to operate correctly. Applications that benefit from a virtual However, unlike LBS systems, which have a Brightness is optimized when the display include interactive ordering systems class 2 or higher laser safety classification, projection surface is white. As with any on tables in restaurants, bars and hotels, HLP products have a class 1 classification other projection technology, projection is and wipe-clean, pathogen-resistant touch and are therefore completely eye-safe, optimized when performed indoors and displays in healthcare environments. In the which is essential for consumer electronics away from strong daylight. home, such a display could allow a wireless- applications. Owing to the principles of As HLP steers light to where it is network-enabled virtual touch-screen on the Fourier optics, the image is also always in required and away from where it is not, kitchen work surface for watching cooking focus, regardless of the distance between the brightness of a HLP device is variable programmes, browsing recipes and buying the projector and projected surface. An and depends on the nature of the content groceries online. image can be projected onto the surface projected. Although it may seem that there Light Touch currently has an HLP of the table with both the top and the is a lot of light in a movie or music video, optical engine that is just 30 cm3 in bottom of the image being in focus at the such content has a typical image coverage volume — roughly the size of a matchbox — same time despite being different distances of approximately only 18% in terms of but the technology is ideally suited to further from the projector aperture. Light Touch area. When this type of content is shown miniaturization. The second generation of uses diffraction to form images, leading to on a first-generation Light Touch unit, it HLP engines, scheduled for release in 2012, bright images and low power consumption. produces approximately 18 lm — marginally will be less than 8 cm3 in volume. Their In addition, because the diffraction brighter than the DLP and LBS pico optical architecture will deliver three times patterns of the image are calculated in projectors on the market at present. When a the brightness of a typical tablet screen software, any aberrations or distortions control panel or ordering system (typically for half the power. This second generation in the image can also be corrected and with 8% coverage) is shown on Light Touch, of tiny HLP projection engines will have compensated for by the software, which the brightness increases to 35 lm or more. the potential to become ubiquitously and simplifies the optical design. This enables the The whole Light Touch system — seamlessly embedded in hand-held devices, Light Touch projector to correct in software including the projection engine, the media homes, workplaces, retail spaces and even for the distortion inherent in the table-down processor and the operating system — cars, fundamentally changing the way we see projection geometry and produce a perfectly consumes 6 W of power, giving a battery and interact with multimedia content. ❐ rectangular image on the table surface. life of 2 h and comparing well with most In Light Touch, we integrate the optical pico projectors on the market. Adrian Cable is Chief Technical Officer at Light Blue projection engine with infrared touch- Despite being restricted to indoor usage, Optics, Platinum Building, St John’s Innovation Park, sensing technology that forms a fan of an interactive projector such as Light Touch is Cowley Road, Cambridge CB4 0WS, UK. low-intensity infrared laser light just above capable of bringing a multimedia experience e-mail: [email protected] nature photonics | VOL 4 | NOVEMBER 2010 | www.nature.com/naturephotonics 751

MIcRoDIsPlAys liquid crystal on silicon David Vettese

Microdisplays based on liquid-crystal-on-silicon technology may soon gain wider recognition as they penetrate an increasing number of markets, ranging from electronic viewfinders to miniature data projectors and head-up displays.

When it comes to display technologies, the pixels) in 2002 and this microdisplay is still concepts of both liquid-crystal displays in production today. (LCDs) and cathode ray tubes (CRTs) are The RPTV market was initially heralded widely known. The same cannot be said as a viable and commercially attractive of liquid crystal on silicon (LCOS), even option for high-definition televisions with though this technology is used extensively large screens (that is, diagonal size greater in many industries that require high- than 32 inch) and vertical resolutions of quality microdisplays. 720 or 1,080 pixels. Manufacturing costs of Most LCOS devices comprise a layer large-panel LCD technology in the first few of liquid crystal sandwiched between a top years of the twenty-first century were high sheet of glass coated with a transparent in comparison with standard costs today. electrode, and a pixelated silicon substrate This enabled investment in the lower-cost, (or backplane) made by the complementary microdisplay-based RPTV concept and the metal–oxide–semiconductor (CMOS) related component suppliers to that industry, ension Displays

fabrication process. Because the silicon M particularly the microdisplay manufacturers. is reflective, it serves as a mirror element This investment allowed microdisplay for each pixel, with the strength of the technology to mature, and three categories reflection electronically controlled by the Di Forth of microdisplay for projection emerged. amount of light transmitted through the These were LCOS (through many liquid crystal above. Separate channels of The SXGA-resolution LCOS from Forth manufacturers), 3LCD (featuring three red, green and blue light illuminate the Dimension Displays. transmissive micro-LCDs, from Epson and LCOS chip in turn, with electronic drive Sony) and microelectromechanical systems signals controlling the transmission state (MEMS, predominantly based on the Texas of each pixel to form an active-matrix image generation. The colour generation Instruments digital micromirror device). colour image. In some cases, a dedicated technique used in this display, the field- However, large-panel LCD technology, LCOS chip is used for each colour channel. sequential colour system (images of each specifically their manufacture, also quickly This is a very simple and elegant design colour channel are generated separately in matured and it became apparent that large- concept: the backplane is formed from a turn at a high rate and the human vision panel LCDs were to be a more popular standard CMOS processed wafer and the system interprets them as a single, full- consumer choice, despite leading market glass substrate has no patterning. Indeed, colour image), was enabled by the use analysts stating that better image quality the CMOS industry benefits from the heavy of a ferroelectric, fast-switching, liquid could be achieved on an LCOS-based investments made by other industries, crystal. This has remained the main feature RPTV set. By the end of 2007, nearly all which allows for increases in pixel density distinguishing the products developed by microdisplay RPTV manufacturers had (and, thus, higher resolution) without the DisplayTech to this day. withdrawn their televisions. need for LCOS manufacturers’ investment. In parallel, during the second half of This left a challenge for microdisplay The origins of LCOS technology can be the 1980s and the early 1990s, intellectual manufacturers. A number of companies traced back to 1973, when Hughes Aircraft, property in ferroelectric LCDs was simply disappeared, as they did not of the USA, developed the first ‘discrete- developed by two UK research-and- have alternative revenue streams, or element reflective display’, which was 1 inch development labs: Thorn EMI Central became occupied by other technologies. in diagonal size. Hughes continued to be Research Laboratories and BNR Europe. Some companies were able to survive by innovators in the field and in 1983 reported This was subsequently combined with the diversifying, for example by supplying a ‘liquid-crystal light valve,’ which was the electronic design skills of Admit Design, business solutions and home cinema first reflective spatial light modulator. Five based near Edinburgh, UK, to spawn projectors. Others, such as ForthDD, chose years later, an LCOS spatial light modulator another LCOS company, MicroPix, in 1998. a more niche-market route, supporting was reported at the University of Edinburgh, The focus of this development was to create and focusing on professional and high-end UK, with a resolution of 50 × 50 pixels. a high-resolution LCOS device positioned application spaces. It was not until 1993 that DisplayTech, to serve the rear-projection television Of the application spaces that ForthDD of Colorado, USA (now Micron), reported (RPTV) market. MicroPix, now know focused on, the main market was again a microdisplay of a resolution sufficient as Forth Dimension Displays (ForthDD; a display market. Although technologies for use as a display. This 254 × 254 pixel www.forthdd.com), shipped its first SXGA- such as Texas Instruments’ digital light array was capable of full red–green–blue resolution microdisplay (1,280 × 1,024 processing can produce higher brightness,

752 nature photonics | VOL 4 | NOVEMBER 2010 | www.nature.com/naturephotonics

the separate colours, in an organic LED Pixel mirror Liquid crystal this figure is only 25%. When seen in an NTE display, the effect is quite striking and TDI Microdisplay very distracting. Incident light The LCOS microdisplay can also (illumination) achieve a wider colour gamut than fixed- colour-gamut microdisplays because LCOS uses separate illumination sources for

els Silicon each colour channel. This allows ‘scene- pix

y adjustable’ and aesthetically accurate colour reproduction (without quality-reducing pixelation) to be achieved successfully in a NTE microdisplay package based on an

ension Displays Reﬂected light

M x pixels (image) LCOS microdisplay (Box 1). These image quality differentiators are Front electrode Cover glass particularly relevant to the professional Forth Di Forth NTE applications. LCOS microdisplays are used, for example, in weapons sight and LCOS devices such as the ForthDD microdisplay with time domain imaging (TDI) use liquid crystal and a periscope simulators for military training, in pixelated, reflective silicon backplane to generate red, green and blue image fields that the eye fuses into binocular imagers for microscope simulation a full-colour, high-dynamic-range image. for medical training, in head-mounted displays for pilot-training and mission rehearsal, and in electronic viewfinders for LCOS is a smaller, more flexible platform optical pathway. This allows for extremely cinematography applications. and can give very high performance in high image fill factor and for the spaces In the military and medical training small spaces. This makes LCOS ideal for between the pixels to be so small that space, the accuracy of a simulated image applications such as near-to-eye (NTE) they are negligible. In contrast, an LCD is paramount and this replication of displays for viewfinders, head-mounted has the pixel circuitry within the optical reality is a much sought-after feature. displays and, recently, picoprojectors — pathway and this blocks some of the light, This verisimilitude is essentially driven miniature digital projectors designed to causing the ‘chicken wire effect’ that occurs by the display resolution as well as the connect to portable electronic devices. when a projection is viewed through a aforementioned image differentiators. The high performance of these transmissive panel. Another alternative Microdisplay resolutions can vary from applications arises from the fact that an technology, organic LED microdisplays, the very lowest, QVGA (320 × 240 pixels), LCOS display is based on a reflective involves subpixels that are each about 25% standard up to about the 4K standard CMOS with an unpatterned glass cover. of the area of the pixel face. This means (4,000 × 2,000 pixels). Since 2002, the SXGA- The pixel circuitry is behind the face of the that although in an LCOS display about resolution microdisplay from ForthDD pixel and, therefore, completely out of the 95% of the pixel can be used to generate has been widely used in military NTE applications and has been designed into many training systems. A good example is in Box 1 | Illumination options missile launcher training, which can now be achieved to the same degree of accuracy and A range of illumination sources have been The choice of illumination source effectiveness in synthetic environments as it used in conjunction with microdisplays. affects the colour gamut of the displays. can in live training environments. Although Lamps are generally used for larger- With lamps, to achieve colour the there is unlikely to be a complete move away sized, higher-brightness applications, illumination has to pass through colour from live training in favour of the synthetic such as projectors and RPTVs. LEDs filters, for example a rotating colour equivalent, increasing use will have an have widespread application, from lower- wheel. The gamut achievable with this is effect on overall training costs and time-to- illumination applications such as NTE relatively low in comparison with the other combat readiness. displays to some scientific equipment such illumination methods. This is also true of Recent developments in cinematography as confocal and interferometer microscopes. microdisplays that use colour subpixels, have also had a direct impact in increasing Increasingly, LEDs are also being used in which are essentially colour filters next to the use of LCOS technology. The recent and compact projection applications. the optical pathway. ongoing move from the recording of movies Red, green and blue lasers are now LEDs have an excellent colour gamut on 35 mm film to a fully digital recording finding their place too. Some pico projectors and can achieve well in excess of the ITU-R solution has seen a need to change from the have laser illumination, such as the Recommendation BT.709 colour gamut (for traditional viewfinder technology in cinema scanning-mirror type from Microvision high-definition television) on the CIE 1931 cameras, namely an optical viewfinder, or those from Light Blue Optics that use chart, and come close to the NTSC gamut. to an advanced LCOS solution in an their extremely clever Holographic Laser We believe that lasers can improve on this. electronic viewfinder. Projection technology. However, there are The brightness that can be achieved The design brief for this was some supply-chain issues relating to the with LCOS displays ranges from about exceptionally difficult: replicate the image availability and price of the lasers, which are 14 lumen for pico projectors to many quality achieved with an optical viewfinder holding back the diffusion of this particular thousands of lumens for home cinema and in an electronic manner. The optical illumination innovation. digital cinema applications. viewfinder has near-infinite resolution, a 100% fill factor, no flicker and no image

nature photonics | VOL 4 | NOVEMBER 2010 | www.nature.com/naturephotonics 753

artefacts — in other words, it is a true media players, whereas previously images representation of what the human visual could only be viewed on small, hand-sized, system sees. It is purely a glass magnifier LCDs. This will result in the manufacture of that views the image captured through a microdisplays in unprecedented volumes, cinematographer’s lens. To replicate this with market estimates suggesting volumes with a microdisplay solution in an electronic greater than 100 million per annum. A viewfinder would be impossible. However, number of large manufacturers of electronic LCOS image quality closely approximates components are positioning their product this with a high resolution of 1,280 × 1,024 line cards to include an LCOS solution pixels, an accurate colour gamut and no in preparation for the day when the noticeable pixelation or flicker. technology is adopted by a gadget- and There is another product in development technology-savvy public. that could bring the acronym LCOS to LCOS technology has been around consumers around the world. This application in various guises for many years and is is pico projection, where an extremely small now verging on mass-market adoption. digital image projector is integrated with or It is inevitable that LCOS will become a connected to consumer hand-held devices DIMENSION DISPLAYS FORTH household acronym to sit alongside CRT such as PDAs or mobile phones. and LCD. But at the same time, LCOS High-performance head-mounted display To meet this need, microdisplays will continue quietly serving a number of featuring microdisplay technology. are evolving and becoming smaller as high-end markets in military, medical and pixel size decreases (again leveraging cinematography applications. All these the CMOS manufacturing industry) and 0.2 inch in diameter, with pixels less than require the best in image quality and they all resolution decreases so that the projector 6 Mm in size. Display resolutions will also use LCOS technology. Q can be made sufficiently small. Today these need to be reduced to WVGA (800 × 480 microdisplays are typically between about pixels) to fit whole projectors into small, David Vettese is European Sales Manager at Forth 0.2 and 0.9 inch in diagonal size and LCOS unobtrusive packages. Dimension Displays, 7 St David’s Drive, St David’s pixels vary from about 6 to 13.7 Mm in size. Image-sharing will be enabled by Business Park, Dalgety Bay KY11 9NB, UK. Future pico projectors may be less than projection from mobile phones and other e-mail: [email protected]

Lambda XL Extended Life Light Source The Lambda XL is a broad spectrum, highly stable light source (±1% peak-to-peak ﬂ uctuations) with an expected lamp life of 10,000 hours. The light intensity can be adjusted to different levels of attenuation and the liquid light guide connection assures output uniformity in the ﬁ eld of view.

FEATURES • 10,000 hour expected life • Highly stable • No high-voltage pulse • No alignment necessary • Built-in driver for optional ﬁ lter wheel and shutter • Adaptable to most microscopes

PHONE: 415.883.0128 | FAX: 415.883.0572 | EMAIL: [email protected] | WWW.SUTTER.COM

754 SutterInst_LamdaXL.indd 1 NATURE PHOTONICS | VOL 4 | NOVEMBER 2010 | www.nature.com/naturephotonics2/4/10 11:25:27 AM

Multistring backlight drivers aid lamination process is used to bond an anti- costs, thus providing a cost-effective power management glare and anti-brightness glass substrate and environmentally friendly alternative to the front of a thin-film transistor (TFT) to xenon arc lamps,” says Bill Beck, LCD module. When used in bright light, executive vice president of business the amount of ambient light reflected development at Laser Light Engines. by most displays is close to or exceeds “And unlike these lamps, the system will the light emitted by the display, leaving provide full brightness over the lifetime of the image ‘washed out’. But according to the projector.” Mark Stephenson, product marketing www.laserlightengines.com manager at Hitachi Display Products, a TFT LCD featuring surface treatment PholeD system boosts techniques and an optically bonded glass display performance substrate can reduce reflections to less than 0.2% by scattering and absorbing ambient US firm Universal Display has developed a light. As Stephenson also points out, the light-blue phosphorescent organic light- bonding process doesn’t leave an air gap emitting diode (PHOLED) emitter system US analog semiconductor manufacturer between the glass substrate and the display, that could significantly reduce the power Advanced Analogic Technologies has which prevents parallax effects and internal consumption and extend the lifetime developed a range of multistring LED reflections. “The display module is more of OLED displays, thus benefiting the backlight drivers for 10- to 22-inch LCD rugged than traditional TFT LCDs, thus battery life of portable electronics. Under panels. The AAT1409/7/5 products offer providing enhanced shock and vibration accelerated test conditions, the system integrated boost converters and precision performance,” he adds. “Display durability operated for 9,000 hours to 50% of its initial current sinks that can support up to 88 is also improved with increased impact and luminance of 1,000 cd m–2 — an increase in LEDs at a total current of 360 mA. The scratch resistance, and reduced fluid and operating lifetime of almost 100% over the drivers also reduce the number of backlight foreign particle ingress.” company’s previous light-blue PHOLED printed circuit boards required while www.hitachi-displays-eu.com emitter system. The system offers CIE still driving high-brightness LEDs and chromaticity coordinates of (0.17, 0.37) controlling the backlight intensity, thus White leD targets outdoor displays and a peak wavelength of 472 nm. It also ensuring uniformity across the display. provides a luminous efficiency of more than “As LCDs continue to gain traction in US components manufacturer Vishay 45 cd A–1, which corresponds to an external the computing, consumer and industrial Intertechnology has developed a non- quantum efficiency of more than 20% at markets, the power, efficiency, accuracy diffused 3 mm white LED that uses 1,000 cd m–2. The company developed the and flexibility of the backlight drivers are InGaN technology to achieve a luminous all-phosphorescent active-matrix OLED becoming critical differentiators,” says intensity of 4,500–11,250 mcd at 20 mA. architecture by adding a light-blue subpixel Ray Chan, technical marketing manager at Featuring a clear, untinted plastic case with to the conventional red–green–blue Advanced Analogic Technologies. “These a lens viewing angle of ±22.5° and high configuration. The company has already products offer an effective approach for light output, the VLHW4100 provides demonstrated the architecture in a LCD power management.” The drivers an alternative to incandescent lamps in 2.5-inch, all-phosphorescent active-matrix can operate from d.c. inputs, cigarette outdoor LED panels, light guides and OLED display. lighter adapters or multicell lithium-ion other applications. The LED also provides www.universaldisplay.com batteries in the range of 4.5–26 V, and are thermal resistance down to 400 K W–1 available in four, six or eight channels. and power dissipation up to 95 mW. transparent oleD makes its debut The drivers also support a pulsewidth Withstanding electrostatic discharges up to modulation dimming frequency of up to 2 kV, in accordance with JEDEC standard Japanese manufacturer TDK has 100 kHz, which ensures silent operation. JESD22-A114-B, the device is compliant announced two types of passive-matrix Furthermore, these drivers are particularly to the restriction of hazardous substances organic light-emitting diode (PM-OLED) suited for use in portable LCD devices directive 2002/95/EC. displays — one flexible and the other operating under low ambient light www.vishay.com highly transparent. The 3.5-inch flexible conditions or in power-saving modes, as type is based on a resin substrate, has a their high efficiency allows the battery life fully despeckled laser system thickness of only 0.3 mm, weights 1.11 g to be maximized. targets digital cinema and has a resolution of 256 × 64 pixels. It is www.analogictech.com available in either colour or monochrome Laser Light Engines, a US manufacturer of models. The transparent PM-OLED, which glass bonding boosts display per- laser-driven light sources, has developed is primarily targeted towards the mobile formance in bright light a fully despeckled laser illumination phone market, has a light transmission system for digital cinema and large-venue of 50% and comes with a 2-inch screen Hitachi Display Products — the arm projectors. Producing red, green and blue at QVGA resolution (320 × 240 pixels). of Hitachi Europe responsible for LCD from the same laser, the system completely Mass-production of the flexible PM-OLED development — has developed a glass eliminates laser speckle in images, reaching is expected to start before the end of 2011, bonding technique that enhances the the level of performance required for digital with the transparent type available for optical performance of LCDs in bright 2D and 3D films. “Our lasers will also sampling immediately. ambient light. An optical adhesive and reduce power consumption and cooling www.tdk.co.jp nature photonics | VOL 4 | NOVEMBER 2010 | www.nature.com/naturephotonics 755

© 2010 Macmillan Publishers Limited. All rights reserved interview technology focus Watch this space Munisamy Anandan, president of the Society for Information Display, talks to rebecca pool about the breath-taking technologies that are now emerging in the displays market.

■■ Which display technologies are we and could therefore drastically reduce the likely to see more of in the near future? power consumption of e-books if they can be There has been a lot of recent excitement economically mass-manufactured. regarding three-dimensional (3D) video. The 3D television market had sold out completely ■■ Where are the opportunities right now? after launch, despite the current economic Many multinational display companies are downturn. Panasonic expects to sell one looking to invest in China, particularly to million units this year, while Samsung is establish LCD manufacturing plants. Making expecting to sell nearly two million units. the LED backlights for LCDs requires the Vigorous research is underway to LED manufacturing infrastructure to be eliminate the need for 3D glasses, although in place, so China is now vigorously trying it may take another three or four years to to establish extensive LED manufacturing reach a stage where people can view a 3D SID operations. The government is subsidising television without glasses. There are glasses- Munisamy anandan: “The electronic book will be critical manufacturing equipment, including free prototypes that exhibit a 3D effect if the the next big growth market for the LED backlight.” nearly 50% of the cost of an embossing tool. user stands directly in front of the screen, but China has been doing the back-end packaging this is lost if the user stands anywhere else. However, at present, manufacturers cannot of LEDs for a long time, but now it wants to Today’s customers also want touch-screens economically manufacture OLED screens manufacture the LED chips themselves. that have the touch-sensitive element inside larger than 15 inches. The backplanes of these the display rather than on the top. This is displays contain low-temperature polysilicon ■■ as president of the society for particularly the case for applications such as thin-film transistors (TFTs), which do not information Display, what are your plans smart phones; researchers are now working exhibit uniform characteristics over a large for the future? hard on a technology called ‘in-cell touch’, in display area. Also, the manufacturing cost of We would like to develop our partnerships which sensors are built into every pixel of a these transistors is high, but yields are low. with various countries. For example, we liquid-crystal display, making the final device A new generation of TFT — the oxide already have partnerships with France, thinner, brighter and more lightweight. TFT — looks promising. Indium gallium zinc Korea and Japan, and we wish to strengthen oxide TFTs, for example, not only exhibit such links. Some companies are unaware of ■■ has any particular technology been good performance characteristics over a large the strengths of certain universities around crucial to the growth of the displays display area, but can be manufactured in the world, so we are trying to provide markets over the past decade? fewer processing steps than polysilicon TFTs. information on the technological strengths of Yes — the LED backlight. We first saw it in Unfortunately, these performance each university, where the breakthroughs are mobile phones, and now LCD notebooks characteristics can deteriorate after exposure coming from, and how industry could benefit are almost completely illuminated by LED to moisture and oxygen during the fabrication from interacting with these universities. For backlights. The technology has, at least over process. When researchers solve this example, I am trying to establish a database the past five years, started to dominate LCD problem, manufacturers will be able to scale in which we will compile all the universities televisions, which demonstrates phenomenal OLED screen sizes to 32 inches and beyond in the world and categorize them based on growth. Power consumption has come while implementing economical mass- which field of technology they are strongest. down, and the longevity of these devices has manufacturing processes. The performance This type of information will be highly increased tremendously as a result. of oxide TFTs has already been demonstrated useful for industry and will help display The electronic book (e-book) will be the at the recent Society for Information Display technologies to grow. We are also increasing next big growth market for the LED backlight. international symposium in Seattle, USA, so our activities on the internet. Many of our A few years ago many people doubted the we should see them in manufacturing lines members operate remotely nowadays, so we potential of the e-book market, but only over the next two to three years. want them to be able to watch or listen to recently Amazon.com saw sales of e-books Researchers have also explored using seminars online. The migration of display surpass those of hardback books for the OLED displays in e-books. Although this technologies to China and also to Brazil will first time. My guess is that this will happen technology has a wider viewing angle and allow us to increase our membership in these globally over the next three to four years. superior colour quality compared with an countries, organize more conferences and LCD, its power consumption is higher than partner with more local societies. This is in ■■ are there any other technologies to that of an LCD and backlight combined. This tune with our mission: to promote display look out for? is a major problem for e-books, as end users technologies around the world. One technology waiting to challenge the LCD do not want to charge their devices frequently. is the organic LED (OLED). Unlike LCDs, An alternative would be to use INTERVIEW BY REBECCA POOL OLED displays do not require a backlight to phosphorescent OLEDs, which are three Rebecca Pool is a freelance journalist based in function, and so are very thin and lightweight. times more efficient than standard OLEDs the United Kingdom.

756 nature photonics | VOL 4 | NOVEMBER 2010 | www.nature.com/naturephotonics

Nature is the pinnacle journal Nature publishes in depth analysis publishing opinionated editorials of the most important science coupled with hard hitting views by policy, business, community and global experts discussing the most breaking news written from an important scientiﬁ c issues in world international perspective, whilst view. Th is week equips you with giving you an inside advantage a succinct round upp of hihighlightsghlights on the new iideas,d approaches and timely news. anandd challengeschalle to research.

COMMENTT CAREERSC

Nature boasts the largestargest WhetherWhe explicitly or and most comprehensiveensive impimplicitly,li the Nature Books & Arts section careers section oﬀ ers among all science journals. you advice and points you Publishing comments written by to actions pursuing success. world authorities and continuing More than a list of pointers, debate on material published in each piece will focus on Nature, our authoritative expert a unique niche such as opinion on any issue resonates new grants, programs, beyond any one ﬁ eld of research. and industry trends.

nature.com/rediscover

With online access your institution can provide you with:

24-hour desktop access to: • Articles online ahead of print (Advance online publication) • Searchable online archive • Reference linking within and beyond NPG • “Export Citation” and “Export References” • “See more articles like this” and “Related links”

To access this latest photonics research online, recommend site license access to your librarian www.nature.com/naturephotonics