From backlights to protective glass and everything in between, developments in display systems and components were a critical part of Display Week 2007. Here is a look at what was shown on the exhibition floor.
by Adi Abileah
EVERY YEAR, the number of display applications shown at Display Week increases, and 2007 was no exception. At this year's show, one of the major applications being showcased was displays for advertising or signage – the next big market for displays – although these are not yet optimized for outdoor use. But no matter what application to which a display is dedicated – from the laser-scanning projectors that can be embedded in mobile devices (mini-projectors) to the variety of stereoscopic displays, to the myriad e-books and other reflective displays that are now gaining traction – they all require the appropriate support technologies for manufacturing and systems integration, and there were several key developments in these areas at Display Week 2007 that are worth noting.
Backlights
Backlight technology is a vital part of the liquid-crystal-display (LCD) structure, since most of the power is going to the backlight unit (BLU). All elements that comprise a BLU were presented at Display Week 2007, including light sources [fluorescent lamps and light-emitting diodes (LEDs)], electronic controllers and drivers, and light-distribution elements (light guides, diffusers, and light-shaping elements). In addition, many companies are making complete BLU solutions.LEDs have the ability to generate higher color saturation for LCDs than fluorescent lamps. Osram Optoelectronics showed a 32-in. display that utilized its LED-based BLU, with impressive colors (> 100% NTSC) and high luminance; the company also showed very bright white LED backlights with their own light sources. Several other companies, including Samsung, Sharp, and LG.Philips LCD, showed large-sized LCD-TVs with LED backlights. On the component and basic BLU system level, Global Lighting Technologies demonstrated its unique backlight designs that feature light guides optimized for small- and medium-sized displays with very high efficiency. Shenzhen Diguang Electronics presented several models of LED backlights with both white and color LEDs (Fig. 1), which are designed for small displays with very low profiles and relatively high brightness.
Although LEDs are approaching the performance of fluorescent lamps in terms of light efficiency, several companies continue to make special fluorescent lamps. JKL Components Corp. had several types of cold-cathode fluorescent lamps (CCFLs), which are optimized for the high efficiency and narrow diameters that are needed in commercial LCDs. LCD Lighting offered both cold- and hot-cathode lamps for high-performance special designs, including avionics.
On the light-control side, 3M demonstrated new versions of its traditional diffusing and light-shaping films – the brightness-enhancement film (BEF) and double-BEF (DBEF) – including the DBEF with improved optical efficiency and combined mild diffusers on the surface. This reduces the number of films required in LCDs, as well as the plastic-to-air transitions, thereby improving transmission. A new player in light-control films is Fusion Optix, with light-shaping films that act as a BEF, but are optimized for any angular-viewing design with elliptical or circular-light collection. Conventional BEFs concentrate light in only one direction. Fusion Optix's films give more flexibility in backlight designs and are very efficient.
Optical Software
This topic is a very important one for display developers who design optical systems and need to optimize LC structures in shorter time. Three companies did work in this area: Lambda-Research, Zemax, and Shintech. Lambda Research's TracePro software addresses imaging optics for lens design, as well as non-imaging optics for light collection, illumination systems, and backlight designs. The Zemax software package focuses on lens design, while Shintech's software deals with liquid-crystal structures, specifically for the optimization of new designs, including retarda-tion films and three-dimensional liquid-crystal molecular structure behavior under driving conditions. Autronic-Melchers, which is mainly a test-equipment manufacturer, also offers LC-modeling software called DIMOS.
Display Protective Glass
Several companies at the show are protective cover-glass suppliers – this includes tempered glass or plastic sheets, plus coatings for anti-glare (AG) or anti-reflection (AR) properties.
One of the highlights in this area was a demonstration by EuropTec where the company invited attendees to try to break its chemically tempered glass with a hammer. When the glass finally cracked, it remained in one piece, and the sign behind it was legible. This is an important feature for kiosks, ATMs, and other outdoor applications that require vandal protection. Coatings (AG and AR) were represented by several companies that supply materials and services, including Dontech, Metavac, JDSU, Thin Film Devices, Eyesaver International, Abrisa Glass and Coatings, and Berliner Glas/US.
3-D
Kopin and eMagin showed near-to-eye stereo-imaging systems. The Kopin display utilizes micro-LCDs with a transplanted thin-film-transistor (TFT) structure. The company also demonstrated a near-to-eye system in which transmissive displays are projected to both eyes, with good optics developed by Micro-Optical (Myvu Corp.). There is an option for stereo view; however, the demo that I saw was regular video. Kopin is making the AMLCD with high-performance single-crystal-silicon transistors by transferring this IC layer onto glass with its unique lift-off technology. eMagin employs organic-light-emitting-diode (OLED) displays and have both monochrome and color options. Both Kopin and eMagin demo units were very impressive with great resolution and sharpness and seemed to be making progress in overcoming eye fatigue after long-time use, which is caused by the eye adapting for the short distance to the actual display.
Other 3-D displays at the show were of the auto-stereo nature, where the two eyes view slightly different images, creating the 3-D effect without the use of eye glasses. This is done by lenslets or barrier lines. SeeReal Technologies showed such auto-stereo LCDs, and the images were impressive; however, there were definite "sweet spots" where the 3-D view was best.
Samsung displayed a two-layered LCD that provided two images superimposed. The company refers to this concept as 4-D, but this is basically two images that have parallax between them. The depth perception is coming from the physical distance (a few centimeters) between the two displays. In the literature this is referred to as a "2.5-D" concept, which was presented in the past and at this show by Pure Depth.
Planar Systems showed their Stereo-Mirror concept (stereo display) that consists of two high-resolution displays and a beam combiner. This 3-D display does not have "sweet spots" – its image quality was the best in the show, although it requires the wearing of polarizing glasses.
Polarizers
Leading polarizer manufacturer Nitto Denko featured new and exciting materials. The rear side of its booth showcased the world's largest polarizer sheet – 108-in. on the diagonal – which was developed for the Sharp's 108-in. LCD (Fig. 2). A new type of polarizer optimized for high-contrast multi-vertical-alignment (MVA) liquid-crystal structure and in-plane-switching (IPS) LCDs was demonstrated. This included retardation films that compensate for the liquid-crystal tilt and birefringence and make the black level darker when light is passing through the crossed polarizers. The other innovation that impressed me is a new hard-coat process (5H). I was able to make a scratch on the 3H (standard) demo, but tried very hard to scratch the 5H demo without any success. This is very important, since many laptop and desktop displays are damaged by cleaning and multiple touches. This will be very useful for smart phones that have internal touch (capacitive or else) capabilities. In higher volume production, this will also reduce costs.
Micro-Laser Scanners
Few companies are focusing on the use of diode lasers with scanning systems. The Israeli company Explay showed miniature projection displays that run on low power and showed few problems in the way of speckles – the company's goal is to embed the units in mobile devices thanks to its small form factor – approximately 25 x 40 x 7 mm (Fig. 3).
Microvision, Inc. (Redmond, WA) showed a head-up display (HUD) for automotive applications, based on scanning laser systems, as well as microprojectors for portable applications. Its performance had higher resolution and higher luminance compared to all other units shown in the hall.
Summary
Display Week reminds me of a child going to a big toy store, and in 2007 the toys were bigger than ever and looked beautiful. The beauty of Display Week, however, is that we get to peek behind the curtain to see the display systems and components that enable these stunning displays. •
Explay
Fig. 3: Explay's oio nano-projector (approximately 25 x 40 x 7 mm) runs on low power and showed few problems in the way of speckles.