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A new sense of touch

The quest for innovation has brushed the touch sensor sector. The big four varieties of touch sensor technology -- capacitive, resistive, surface acoustic wave, and infrared -- are getting makeovers, while one company is campaigning their technology as a fifth touch sensor.

July 15, 2002

In many kiosk deployments, the most important connection between the unit and the user is the touchscreen, literally. With the touch of a finger or the brush of a stylus, users can access a cornucopia of options, depending upon the kiosk's function.

So it should come as no surprise that touch sensor technology, the machinery that senses impact on the touchscreen and acts accordingly, is a complex issue, with several primary forms of technology.

Practically all touchscreen applications fall under one of three technologies: resistive, capacitive, or surface acoustical wave. And a fourth, infrared, is making a comeback.

But touchscreen technology is in a period of evolvement, as manufacturers look for new ways to enhance current technologies or develop brand new technologies. And for an industry which has just two main market leaders, 3M Touch Systems and Elo TouchSystems, and many smaller, ambitious companies, the drive to innovative is surprisingly strong.

"There's always room to try new technologies in this business," said Larry Loerch, global business manager, monitors, for 3M Touch Systems.

Defining the sensor

Though it seems like a simple concept - touch the screen, something happens - the technology behind the touchscreen is complex. Each of the four leading sensors are built around different scientific means.

With capacitive, for instance, the human sensation is the trigger for the technology. A slight electrical current on the screen, which is typically glass with tin oxide coating, picks up on the sensation of human skin touching the sheet. The current is drained at the point of impact, leading to the next action.

Resistive touchscreens follow the sandwich principal, with some form of plastic covering a thin piece of glass on top and bottom. Tin oxide covers the glass with an electrical current applied. Users press on the plastic coating, which is microscopically separated from the glass. Pressing the plastic against the glass causes an electrical grounding, setting off the action.

Wave action is the key to surface acoustical wave touchscreens. Transducers emit waves across the screen, both horizontal and vertical. Sensors on the other side of the screen pick up on the wave's emissions and pick up on any touches that shift the waves.

Infrared technology features transmitters located around the edges of the screen's mounting rim, or bezel. The transmitters emit horizontal and vertical beams that cover the screen. A touch interrupts the beams, triggering the appropriate action.

But in each case, there are some drawbacks. According to industrial workstation company Pro-Tech Inc., capacitive touchscreens can be triggered either by a stylus or the direct touch of human skin, but not by glove-wearing customers. Glove wearers can use resistive touchscreens, but the surface is prone to vandalism. Albert David, chief executive officer of Canadian technology company A D Metro, praised surface acoustical wave touchscreens, but said they still had problems.

"The screens are very sensitive to dirt and dust," David said.

There are strengths and weakness to each sensor. The room for innovation is there, and several touchscreen companies are attempting to move the sector forward.

"Companies are investing in the future," Loerch said. "It's a defensive move. You've got to keep improving or get out of the business."

A D Metro and 3M Touch Systems are both looking to bring new technology to the touch sensor sector. The two are tackling different problems in various ways, and are also displaying a different semantical approach.

The big boys play

According to Loerch, 3M Touch Systems has developed a new capacitive technology that is stylus independent. The new sensor was displayed at the Society for Information Display's annual trade show and conference in Boston May 19-24, and 3M plans to deploy it next year.

"We are looking at introducing new touch technologies in 2003 that will be totally different from anything that's out there," he said.

The company currently supplies capacitive touchscreens, along with four-wire, five-wire, and eight-wire resistive models. 3M already has a capacitive model that is designed for harsh environments, yet is sensitive enough to human electrical fields that that its screen can be triggered by gloved hands.

Loerch said the new sensor could not be classified as the "fifth" touch sensor. Instead, it is another attempt to move capacitive technology forward.

"Its got great optics, great durability, and it is stylus independent," he said. "That's three components of the technology which I think will advance the sensor forward."

Stepping up to the plate

A D Metro does not have the high-profile standing of a 3M Touch Systems or Elo TouchSystems. The privately owned, Ottawa-based firm started in 1988 as a small regional distributor of point-of-sale peripherals and bar-coding devices.

The company, which had revenue of "less than $10 million" last year, according to David, began focusing on touchscreen technologies about three years ago, starting off selling a five-wire resistive sensor.

"We started off integrating into monitors but we found a very short list of suppliers who could supply the technology," he said. "The technology was tightly controlled and the availability was never consistent."

Canadian touch sensor manufacturer A D Metro believes its Ultra line moves resistive touch sensors so far forward that Ultra could be its own touch sensor category.

So the company began developing its own sensor line, which A D Metro is calling Ultra. While Ultra uses five-wire resistive technology, David said the company considers the sensor advanced enough to be considered as a "fifth" primary touch sensor.

What separates the sensor from other resistive forms, according to David, is the covering. Instead of the traditional plastic-on-glass-on-plastic design, A D Metro is using a glass-polyester lamination covering.

David said Ultra is a significant step forward because it takes five-wire resistive technology into outdoor and rugged environments.

"We still believe resistive technology is the most stable and reliable operating system," he said. "The drawback is it's not vandal proof. We believe the improvements we've made in Ultra will allow it to be used in different environments like kiosks and gaming.

"We hope that the technology will be robust enough to operate in applications outdoors," David added. "We believe this will be the ultimate in touchscreen technology, because it takes away the drawbacks of (capacitive, resistive, and surface wave acoustic) while keeping the benefits."

Will it or won't it

Mike Sigona, market manager, gaming, for Elo TouchSystems, is skeptical of efforts to make resistive touchscreens more accessible to kiosk deployers.

"(The Ultra) is nothing new," Sigona said. "There was a company in Germany that was doing that years before. It's never been successful because the thin glass can be smashed."

The company in question, Schott Glas, quit making the touchscreen several years ago, according to Sigona.

David contends that the Ultra's design and materials will prevent A D Metro from having the same problems that dogged Schott.

"The glass is one-tenth of a millimeter in thickness," David said. "The trick is to get the glass to stick to the polyester. It's flexible and tough. You can wrap it around your finger, yet you can hit it with a hammer and it won't break."

Sigona said the basic design of the acoustical surface wave touchscreen gives it a technical edge over resistive-based units.

"Our surface wave machines you can scratch on the front and they will still work, plus they have better optics," he said. "Any resistive screen will not be popular in kiosks because of the polyester and the optics."

A D Metro plans to sell the sensor for $135 for a flat, 15.1-inch monitor, and $45 to $50 for the controller. Sample stock became available in late June, around the same time the company filed technology patents with Canadian officials.

Infrared gets brighter

While resistive, capacitive, and surface acoustical wave are the three touch sensor technologies discussed most often in the kiosk industry, Sigona said infrared technology is making a comeback as well.

Infrared technology never lost favor in some areas of the world, such as Japan, but directional issues on some screens created problems.

"On CRTs there was a big parallax issue," Sigona said. "But now they've come back with LCD models with the bezel. The beams go right over the surface of the LCD and it has almost pixel-like resolution."

One company that advocates infrared touch technology is computer workstations developer Dolch. The San Diego-based company recently launched a line of infrared touchscreen displays and workstations designed for rugged work environments.

Dolch's EnhancedInfrared technology is designed to maintain its calibration and is immune to cuts or wear on the touch surface, according to company officials.

"These touchscreens are designed for high-pressure caustic wash downs," Dolch president Jim Ciardella said in a news release. "Scratched, gouges, even deep cuts won't affect the functionality of these touchscreens."

Whether it is allowing the gloved to use a capacitive model or making infrared models available for industrial deployments, touch sensor manufacturers continue pushing the touch envelope. It remains to be seen whether a fifth primary sensor comes out of this technological competition, or if innovation remains rooted to the current sensors.