Ensuring digital displays flourish in all conditions

June 03, 2014 // By Mike Logan, andersDX
Today, wherever we go, information is at our fingertips – whether it comes from indoor equipment, outdoor kiosks, or the smartphone in our pocket. This penetration depends heavily on the equipment and devices’ display and touch interfaces; can these UIs effectively deliver an engaging and reliable experience, withstanding challenges from any environment they find themselves in?

Below, we look at these challenges and the technologies to counter them. We then draw on AndersDX’s extensive experience with supplying UIs into widely varied applications to show these technologies working in practice.

Display enhancement requirements and solutions

Display enhancements are typically needed to accommodate and compensate for glare and sunlight, fingerprints and scratches, shock, vibration and malicious attack, and temperature extremes. Additionally, as displays become increasingly interactive, any enhancements must be complemented by suitable touch screen solutions. Other issues including humidity, water and dust ingress can be solved with suitable, and well-established, enclosure designs.

Circular Polarisers provide optimal sunlight readability, cutting total light reflections to 1% of incident light. Sunlight readability can also be improved by applying anti-reflection optical films or coatings combined with optically-clear glue between the display’s surface and the transparent protective layer. This can yield further reductions in total reflections to as low as 0.2%, resulting in a perceived increase in display contrast of some 300%. Anti-glare films reduce glare that can originate from over-head lighting, for example, by diffusing concentrated beams of light to levels far less distracting to the user, while increasing light output of a display’s backlight unit to deliver a front of display luminance of around 1000nits or above, which will greatly contribute to improved sunlight readability.

Optical bonding, the term that describes the clear-gluing process mentioned above, is highly effective in outdoor and public environments. As well as improving contrast ratios to 10:1, it provides up to three-times better impact resistance. Safety glass is also available to provide an excellent level of vandal resistance, while anti-smudge screens reduce everyday fingerprint and scratching issues. For applications such as ATMs where privacy is required, privacy filters are available that limit full-field viewing angles to 48˚ or 60˚.

Where strong sunlight creates heating as well as readability problems, a heat mirror can keep displays cool. By reflecting infrared radiation, these can reject 90% of incident solar energy. Conversely, a transparent heater can be used to warm displays in extremely cold environments, extending operating temperatures down to -50˚C.

Different touch technologies are available for interactive UIs. Resistive touchscreens are preferred where low cost and low emissions take precedence over ease of use. 4-wire types are standard, with 5, 6 and 10-wire solutions available as alternatives for enhanced robustness. They can be integrated with a coverlens for aesthetics and protection. PCAP Projected Capacitive touchscreens offer greater accuracy and an “iPad-like” user experience together with thinness, low weight, great durability, and multitouch capability. A recently-introduced technology – ShadowSense – offers a scalable and robust solution with drift-free performance, outstanding optical clarity and a fast, accurate response time. This optical touch technology, implementing multitouch detection from the periphery of the display, is reliable, durable and attractively-priced.