Touching the Future

By Gregory A. Quirk, Mouser Electronics

Apple stated it very appropriately in their recent media invitation: “We have something you really have to see. And touch.” Over the past five years, Apple has been revolutionizing the way that consumers interact with consumer devices by implementing intuitive touch controls. Since that time, almost every other company has followed in their lead by implementing touch sensing technology, even some products that should not have it.

By now everyone is familiar with how touch sensing technology works. Instead of physical buttons the user touches a screen overlay that registers the location and software determines what action should take place. There are countless benefits to adding touch screen technology to a system, including the fact that no additional components are required, such as a keyboard or mouse.

Touch screens, and even multi-touch, have been around for quite a while. In fact, the first instance of capacitive touch technology was created by E.A. Johnson in 1965 and was commercialized by Elographics in 1977. Multi-touch was invented in 1982 at the University of Toronto.

It has taken a while for touch technology to take off, but now that it has it is creating an unstoppable market. It was estimated that there were 566 million capacitive touch screens shipping in 2011, and that is just for mobile phones. When you combine all of the other applications, including tablets, GPS, handheld game consoles, laptop mouse controllers, automotive application and point of sale terminals the number becomes astronomical in proportion.

Looking at the revenue numbers, touch screens went from US$4.3 billion in 2009 to US$7.1 billion in 2010. The projected numbers grow much faster from that point on, going to US$13.4 billion in 2011 and rocketing to nearly US$24 billion in the next five years.

However, there are technical challenges that must be met for a successful touch screen to enter the market. These include eliminating noise so that the touch gestures can be detected more accurately, reducing power consumption of the displays, handling the issue of sweaty fingers, and the need to make the devices both thin and strong.

Types of Touch Screen Technology

While there are other types of touch screen technology, the two most common today are resistive and projected capacitive.

Projective Capacitance

The largest share is made up of projective capacitive and accounts for 67% of the revenue, equating to US$3,140 million in 2010. While the revenue numbers are substantial, this type of touch technology only makes up 52% of the volume.

Projective capacitance uses an array of values on an X-Y intersect. When a finger touches the screen it changes the capacitance between the electrodes signalling a contact. In smaller devices, a single controller chip can be used, but as the screen size increases it may require multiple chips to register the touches. Due to a high signal-to-noise ratio a stylus can be used on these devices helping to alleviate finger prints keeping the display clear.

The advantages of projective capacitance are that they can be created to be highly durable and utilize multi-touch capabilities. They can even be used in odd configuration devices, such as curved screens or those without a bezel to make the screen size as large as the actual device.

There are a wide range of applications or projective capacitance, including mobile phones, tablets, notebooks and nearly any consumer device that is in the market.

Resistive

The second major type is resistive. Compared to projective capacitance, they only accounted for US$900 million, or 19% of the revenue, in 2010, but made up 44% of the total shipments.

Resistive touch screens measure the change in voltage when a finger touches the screen to determine a touch. As this is a simpler technology, resistive touch has a lower cost and has been used predominantly in point of sale terminals. There are new opportunities for this technology to be adopted in automotive applications but it may take time before they are designed into vehicles due to the design cycle times for car to enter the market.

There are, however, some disadvantages to resistive touch, including lower durability, poor optical quality and the fact that they can not use multi-touch techniques limiting their market potential.

Multi-Touch Architecture

Speaking of multi-touch, this is an area that has really taken off over the past few years, especially since the introduction of the iPhone. There four main parts to creating a multi-touch application, including:

Application – Capable of decoding multiple streams of moving points and taking actions in response

Operating System – Capable of forwarding multiple streams of moving points (and acting on a defined subset of them)

Touch Screen Controller and Driver – Capable of delivering sets of simultaneous points to the OS

Touch Screen Sensor – Capable of sensing multiple simultaneous points

The Future

Given the current trajectory of touch screens it is difficult to feel that the end is near. There are countless, and hilarious, videos of children trying to interact with books or older devices and trying to move the images around or “open applications” assuming that it is a touch screen. This just shows that, while the current generation is getting used to interacting with screens in new ways, the next generation has already adapted and is expecting this to be the norm. That will lead to a further increase in demand for touch screens and the components that create them, such as touch controllers.

Greg Quirk has been a technical writer since 2004 focusing on semiconductor components, consumer devices and business trends. He has written numerous articles for industry publications and presented at technical conferences. His expertise has been sought by the financial community on multiple occasions to predict design-wins in popular consumer products.