DISPLAY TECHNOLOGIES 22 Electronic Engineering Times Europe October 2014 www.electronics-eetimes.com C M Y CM MY CY CMY K Is there life after touchscreens? By Junko Yoshida Touch panels have become such a mainstay of our everyday gadgets that many of us are already taking them for granted. At Touch Taiwan show, I saw display vendors mired in the battle over ever-narrowing bezels, and the neverending pixel-per-inch war. As I examined the proliferation of display technologies, I found myself getting lost in the weeds. AUO, alone, is spreading its resources wide and thin as it works on four different display technologies, ranging from amorphous silicon (a-Si) and low temperature Polycrystalline Silicon (LTPS) to oxide TFT and OLED. So many panels on display at the show were breathtakingly beautiful. Does a narrow bezel matter? Absolutely. Do consumers want more PPI? You bet. Nonetheless, I couldn’t help but roll my eyes when the discussion kept coming back to whether a 1mm border is really that much worse than 0.7 mm for a 5-inch full HD high resolution smartphone panel. I understand that specs are life-ordeath for engineers. But all this “specmanship” is killing Taiwan’s display vendors. To make matters worse, the fierce price competition just keeps escalating. Vendors are scrambling to devise new (and possibly more simplified) manufacturing processes, while staying constantly on the lookout out for new materials. Display vendors, in general, are also clobbered by rapidly changing market trends. Declining e-reader demands worldwide, for example, have affected EInk. (However, I was pleasantly surprised to see E-Ink displays smartly designed into some of the most inventive smartphones featuring dual screens.) Meanwhile, the growing education market for media pads and electronic whiteboards is asking for larger touch screens -- where pupils can use a pen instead of a finger. The logic is intuitive: Teaching kids how to write on a touch screen that only recognizes fingers must be tough. Sharp, although a latecomer to the touch screen market, demonstrated a large-screen projected capacitance technology that can also respond to a passive stylus. Sharp is leveraging a new analogue front-end IC it developed to improve the signal-to-noise ratio. It’s specifically designed for a large-surface multi-capacitance touch screen. Although it’s too early to predict the end of an era for touch screens, it was interesting to hear Tetsuya Hayashi, one of the keynote speakers, talking about development activities around post-touch screen technology in Japan. Hayashi, deputy director of Nikkei BP ICT Innovation Research Institute, illustrated the future of display technology as “ambient,” “free-form,” and “wearable.” Images, he foresaw, will be projected on any surface or in the air, instead of being constrained to a rigid, bulky box. Any surface for touch The whole point of a “touch screen” is that the screen responds to human touch. But what if you could touch any surface - your clothes, your desk or in the air - to make your device respond to the movement of your hands? Called “Anywhere Surface Touch,” the new technology uses any surface as an input area with a wearable device. It turns any flat or curved surface within reach into an input area. The interface uses a single small camera and a contact microphone to recognize numerous interactions between the fingers of the user and the surface. The system recognizes which fingers are interacting and in which direction the fingers are moving. Additionally, the fusion of vision and sound allows the system to distinguish contact conditions between the fingers and the surface. The Ishikawa Watanabe Laboratory at the University of Tokyo is working on this. YotaPhone YotaPhone is said to be the world’s first dual-screen smartphone with an alwayson display. Developed by Yota Devices, based in Russia, it uses E-Ink’s electronic paper technology LCD – see figure 1. Pocketbook cover reader Similar to Yota Devices, Pocketbook, founded in Ukraine and headquartered in Switzerland, showed off a Pocketbook Cover Reader. Shown in the picture, it offers a second screen. Readers can turn off the Galaxy S4 screen and just read on the E-Ink screen LCD – see figure 2. Sharp unveiled a capacitive touch panel system, which it says could be applied to a very large screen. The picture above shows a 70-inch touch panel. The limitation of touch-screen size is attributed to conventional sequential drive controllers, because as the number of sensor channels increases, the SNRs degrade. Sharp, as revealed in its ISSCC paper earlier this year, resolved the issue by driving the sensor channels in parallel. Although the parallel drive methodology tends to mix the signals from multiple channels, Sharp engineers have figured out a way to reconstruct the original signals – see figure 3. Amorphous silicon (a-Si) TFT LCD for smartphones? Now, AUO says it plans to launch a 5-inch full HD smartphone panel by using an a-Si TFT LCD – see figure 4. The 5-inch panel on display, with 443 ppi pixel density, comes with a 1mm border. Fig. 1: E-Ink’s always-on display, integrated into the backside of the YotaPhone. Fig. 2: The Pocketbook Cover Reader offers a second screen based on E-Ink screen. Fig. 3: Sharp’s high SNR projective capacitive touch panel.
EETE OCT 2014
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