Ease of use is a key objective in high-tech product design and low-priced LCD panels are promoting the use of images and colour to create intuitive and attractive user interfaces. Adding touch sensitivity is a logical evolution, allowing the user to interact directly with the graphical interface rather than via buttons or a keypad. Interface design and touch-sensor technology have each improved to meet the demands of a broadening range of applications. Together, these enhancements are revolutionising the capabilities and appearance of equipment such as home appliances, information kiosks, gaming systems, signage and retail terminals.
Arguably, it is the latest mobile phones and high-end consumer products such as media players, games consoles and personal video recorders (PVR) that define the leading edge in user-interface design. Advanced human-factors design can also be seen in new generations of manufacturing equipment, through features such as interactive menus and, 3D graphics and colour-coded options. Benefits include faster and easier operator training, quicker setup and advanced capabilities.
Designers must consider many aspects when implementing touch technolgy
By adding touch technology, equipment designers can eliminate mechanical keys, switches or a mouse. This not only promotes ease of use but it can also save size and assembly costs, and increases reliability. A wipe-clean surface also benefits many types of domestic and industrial equipment, as well as applications where hygiene is important. Touch capability also allows equipment operators to deploy more intelligent, interactive devices in public places. By allowing users to touch their desired selection directly, equipment such as ticketing machines, vending machines, information kiosks and automated payment terminals can be made accessible even to users who are not confident with computers.
To implement touch successfully, designers must consider a number of aspects including the environment in which the equipment will be used, as well as its anticipated usage and expected lifetime. Equipment designed for outdoor use, for example, such as forecourt payment systems or public information kiosks, will prioritise potential false activation by rain, leaves or snow, resistance to low or high temperatures, susceptibility to scratching, and possible ingress of dirt, dust or water. Good sunlight readability is also important, which demands high optical clarity to display images at the highest possible brightness. Today's touchscreen controllers are able to support sophisticated features such as drag and drop and mouse-click functions. The latest touch-sensitive consumer devices are now moving to adopt new features such as gesture recognition (e.g. two fingered pinching, flicking and zooming). Even smarter developments are soon to be expected such as multi user touch capability and haptic functionality providing tactile feedback to the user.
A number of touch-sensor technologies have been developed to answer challenges from specific application areas. The majority are what can be described as front-face-active technologies, such as multi-wire resistive sensors or conventional capacitive touch sensors integrated as an overlay to the front of the display. Other front-face-active technologies such as infrared and Surface Acoustic Wave (SAW) touch sensors rely on a light or sound based field set up across the surface of the screen which detects the disturbance created by a touch.
When selecting the optimum sensor for a given application, the designer must evaluate practical aspects such as the anticipated duty cycle, the climate and environmental factors mentioned earlier, and the relative importance of withstanding physical damage. This damage may be accidental or environmental; however, it may also be due to vandalism or co-ordinated criminal attacks directed at equipment such as self service banking or access-control systems. Even wear-out under normal use, if not accounted for, can necessitate frequent replacement, thereby increasing the cost of ownership for the equipment operator. For example, the lifetime of a standard four-wire resistive sensor, can be as low as 300,000 operations.
"Projected Capacitive Technology (PCT) is a development of capacitive touch technology that replaces the traditional capacitive overlay with an array of micro-fine electrodes generating a capacitive sensing field in front of the sensor"
False touch detection is another hazard that designers must bear in mind; infrared and SAW sensors are particularly vulnerable to rain hitting the surface of the display. Performance can degrade if infrared transmitters become dirty or operate in strong sunlight, while SAW sensors must be carefully integrated into the display unit if any degree of dust or water resistance is desired, which can add to manufacturing costs.
Projected Capacitive Technology (PCT) is a development of capacitive touch technology that replaces the traditional capacitive overlay with an array of micro-fine electrodes generating a capacitive sensing field in front of the sensor. The sensing array is encapsulated within a composite construction. This eliminates direct contact with the user, resulting in effectively infinite endurance in normal use. Furthermore, a touch will continue be detected even if the front panel becomes heavily scratched or gouged. Where high security is necessary, such as in self service cash dispensers or access control systems, toughened or even laminated glass can be specified for extra strength. The sensing array enables reliable and accurate touch detection even for front panels approaching 20mm thick.
PCT provides a powerful choice in many general-purpose applications. The sensor can be designed to facilitate stylish, pure glass fronted display designs without bezels, which also aid cleaning and water run-off. The sensor construction, unhindered by the attenuating effect of conductive coatings, results in high light transmissions desirable when considering deployment for use outdoors. For applications in harsh environments such as computer control systems used in the farming, mining, petrochemical and food preparation industries, the touch display can easily be sealed to prevent liquid, particle or even gas ingress and allow easy cleaning.
With the growing popularity of widescreen LCDs and the emergence of large-format display based signage, the ability to add touch capabilities to large displays allows many new visions to be realized. Most touch sensors cannot be used with screen sizes above 40 inches, but a recently developed multichannel controller from Zytronic now allows PCT touch sensing on screen sizes up to 82 inches including widescreen formats.
Touch display can be sealed to prevent liquid, particle or even gas ingress
By changing the encapsulating materials surrounding the micro-fine capacitor array, PCT can now be offered in the form of flexible touch sensors in a variety of sizes. When combined with an integrated rear projection film PCT sensing enables the quick deployment of interactive displays on any clear surface, and is delivering new retail experiences. High-street shops such as travel and estate agents, for example, have taken advantage of PCT's ability to operate through a covering layer. The flexible film is applied to the inside of the shop window, and then Content and images are projected from a nearby PC, allowing passers-by to easily browse and order goods and services even outside normal opening hours. This also allows operators to track and refine offerings based on real-time consumer preferences.
Large, arresting and interactive images generated by high-profile examples of interactive storefronts are powerful testimonies to the convergence between end-user's needs and hardware and software capability, all brought about through rapid advances in computing and networking. Success of such a system depends upon effective performance at the user interface level - including enhanced touch technology - to provide optimal functionality whatever the environment or situation.
www.zytronic.co.uk