The Limitless Horizon for Touch

by Stephen P. Atwood

If you are just opening this March issue, I hope you notice that it is thicker than the previous few. The reason is fairly simple. Our Guest Editor Geoff Walker brought to us an outstanding array of submissions and we just could not bring ourselves to cut anything out. Touch technology has been around for as long as I have been in the display busi-ness. In fact, I've worked full time at three different touch businesses and consulted with several more during my career. I can even remember some of the first demonstrations of various acoustic and capacitive touch technologies and I have had the privilege of meeting many of those inventors.

But I doubt any of those early inventors could have envisioned the massive scale of adoption and utilization that has taken place around mobile devices. Seemingly, almost overnight everyone is using touch with ease to navigate complex interactions with their iPhones, PDAs, and other devices. Early complaints about accuracy, response, uncertainty, and image quality seem to have evaporated like snow on a warm day. Of course, we know those issues have not really evaporated; rather, a significant number of very talented engineers have been hard at work innovating for the past several years and, with some assistance from the semiconductor and materials industry, have circumvented these problems enough to please consumers. One of the most frequent complaints about early PDAs was the accuracy of their resistive screens. If you had an early PDA device with stylus input, you no doubt struggled at times with the gesture-recognition software and became frustrated by the on-screen keypad when the stylus picked the wrong letters or numbers. Similarly, using your finger to select things was like using a shotgun to hunt ants. Sure you could get the target, but the collateral impact was substantial. And, even if none of this deterred you, then the eventual degradation of the screen due to stylus-induced wear was disappointing.

Projected-capacitive screens, with their matrix of absolutely addressed conductors and rigid glass surfaces, have really changed the experience. Now there is little calibration error or drift, the contact with your finger can be very light, which allows for more precise selections, and I have yet to see a pro-cap screen worn out by normal use. That said, we are far from the ideal solution because the typical pro-cap screen does not support stylus use and is more expensive than a similar resistive screen. Efforts to remedy this situation are revealed in the Frontline Technology feature "Projected-Capacitive Touch Technology" written by Gary Barrett and Ryomei Omote. Barrett, incidentally, is one of those fundamental inventors of touch technology I referred to in the beginning of this editorial. If you talk to him, he can expound on the many technical and business challenges the industry faced in its infancy. It took a lot of hard work and creativity to get to where we are today. But don't let me leave you with the impression that resistive screens are outmoded either. Engineers have made great strides with resistive technology, employing more durable materials, better optical coatings, and even high-resolution matrix addressing to produce accuracy similar to that of pro-cap screens.

So, does this mean the quest is basically over? Are we at the shores of the touch-technology journey and ready to unload the boats for good? Have we discovered everything that needs to be discovered? Not a chance! If you have read any of our previous issues on this topic you know the theme: Touch keeps getting better, but there is no one technology that does everything or meets the needs of all applications.

As you will read in this issue, the field is awash in both somewhat whimsical work such as Surface Computing, as examined in the Enabling Technology article, "Beneath the Surface" by Geoff Walker and Mark Fihn, as well as in more practical challenges, including the actual emulation of a physical control mechanism, which author Bruce Banter describes in the Enabling Technology piece, "Touch Screens and Touch Surfaces Are Enriched by Haptic Force-Feedback."

One of the more fundamental ambitions of touch inventors is the complete integration of touch and displays. By complete I mean the display and touch mechanism being all one physical component, the essential elements being indistinguishable from each other to the user or system designer. In what seems like the distant past, when others and myself worked on doing this with CRTs, we experi-mented with using layers of the anti-reflective coating on the face of the CRT to also serve as a capacitive touch sensor. It worked, but then LCDs took over the world (more or less), and we moved on to other more commercially viable endeavors. The touch people never forgot this concept, however, and numerous groups continued to experiment with schemes to integrate touch mechanically, optically, and electrically into LCDs. You may have seen these demos at SID over the last 10 years, some working better than others. Within the past year, this work has finally resulted in commercial success. Now a possible new paradigm of product designs is about to emerge in which the bezels can be even thin-ner and the touch screen is the display. The current and future state of this work is ably described by Geoff Walker and Mark Fihn in their Frontline Technology article "LCD In-Cell Touch." Do not miss this article – in-cell is coming for real.

If you are not already familiar with the rich-ness that well-engineered touch interfaces can bring to a product, take a look at author Mark Hamblin's article titled "Taking Touch to New Frontiers: Why It Makes Sense and How to Make It Happen." Here, Mark explains the ins and outs of user interfaces enabled by touch. Among his past experiences, Hamblin was part of the core multi-touch engineering team at Apple, where he led the design and process development of the touch screen in the original iPhone and subsequent touch products.

I cannot begin to address all the other nuggets of innovation going on in the touch world or even the rest of the nuggets in this issue, but in case you think I'm getting too effusive over this topic, I invite you to read our Display Marketplace article on "The State of the Touch-Screen Market in 2010" by Display Search's Jennifer Colegrove. She now measures the total market in the mid-billions of dollars, with a growth rate that other display market segments are very envi-ous of. In units, the numbers are staggering, while the number of different suppliers con-tinues to be very large (over 100). There has been only limited consolidation during the last few years, with more evidence than ever that no one technology or supplier can supply solutions for all the applications out there. Touch is one of those elusive technologies where so far the one penultimate embodiment has not yet emerged and may never. With so many unique and diverse approaches, the solution space is almost as broad as the supply base of commercial offerings. For me, this is actually refreshing and I enjoy seeing so many entrepre-neurial efforts succeeding alongside each other.

I am extremely grateful for the limitless hard work and enthusiasm our guest editor Geoff Walker brought to this issue. As one of the leading innovators himself, Geoff truly shows his passion for the industry wherever he goes. I hope you enjoy this issue. We continue to welcome your comments and feedback on all that we do at ID.

Correction to Poly-Si Article

We're always pleased when we get reader feedback, and when an error is spotted, we're eager to set the record straight. I n this case, we were alerted to some inaccuracies in our Enabling Technology Article titled "An LTPS Overview" published in the December issue. In particular, we were reminded that:

• (1) Low-temperature polysilicon (LTPS) has an higher electronic mobility than amorphous Silicon (a-Si), but an higher hole mobility as well.

• (2) Amorphous-silicon (a-Si) does not contain any crystalline structures. Rather, it has a randomized structure of the silicon lattice. Poly-Si consists of a polycrystalline phase – many small crystallites, but with randomized orientation.

• (3) While LCD manufacturers are not generally integrating drivers with a-Si today, Sarnoff labs did develop a process for a-Si driver integration in the past – it is possible to achieve this.

You can read a corrected version of this article on-line at www.informationdisplay.org.

For a more complete explanation of the various types of semiconductor materials being used for active-matrix switches in LCDs and OLEDs, we invite you to review "Flexible Transistor Arrays," by Peter Smith, David Allee, Curt Moyer, and Douglas Loy, in the June 2005 issue of Information Display. •