Dispersive Signal Technology in Interactive Digital Signage–Gentile Touch

Dispersive Signal Technology (DST) from diversified technology company 3M has been specifically developed for interactive digital signage applications such as digital signage, retail point of sale, point-of-information, conference rooms and education presentation systems. The technology is available in screen sizes ranging from 32” to 46” diametre, setting new large-format touch standards for fast, accurate, repeatable touch response.

Where other large-format touch technologies distribute an optical field, infrared beams, or acoustic waves across the front surface of the touch screen and rely on a touch to interrupt the field, DST waits passively for a signal created by a touch contact. This radical approach means that blemishes, such as dirt, grease or solids, can accumulate on the surface and around the edge of the screen without a significant effect on the performance of the DST touch screen. Surface damage to the touch screen, such as scratches or a gouge, should not affect its touch performance.
This technology works by determining a ‘touch point’ after measuring the mechanical energy (bending waves) within a substrate created by a finger or stylus touching the surface of the glass. Bending waves differ from surface waves in that they pass through the depth of the panel rather than over the surface of the material. This has several important advantages such as enhanced palm rejection and superior scratch resistance.When the touch implement makes contact with the screen, this sets off bending waves that spread outwards from the touch location. As the wave travels outwards, the signal disperses and spreads out over time. Piezoelectric sensors positioned in the corners on the backside of the glass convert this smeared mechanical impulse into an electrical signal. The distance from each sensor determines the extent to which the signal is dispersed. Essentially, the further away the ‘touch point’ is from the sensor, the more the signal is dispersed.
Once these signals are properly filtered and digitised, various signal processing techniques are used to determine the touch location. Most importantly, the dispersion is corrected for by mapping between the temporal and spatial domains using prior knowledge such as the bending wave profile, glass dispersion effects, and other substrate characteristics. Once in the spatial domain, an accurate touch location is calculated.
One of the key strengths of DST is the fact that it uses intricate, proprietary algorithms to calculate the touch point. It has a very fast and accurate touch response, with the controller continuously processing the touch point, and even attains more than 99% touch location accuracy as it can even respond accurately and reliably to continuous, repeated touch in the same location. This ‘repeatable accurate touch’ is another important feature of this kind of technology.
Even static objects lying on the glass surface pose no barrier for this technology. If objects like cups, keys or wallets are left on the screen, or if other users are touching it, or the user himself rests his other hand on the touch screen, DST will ignore all these interferences and continue to respond to the user’s intended touch. This unique touch capability manages to screen out accidental touches and override any interference from permanent surface damage. Since DST measures the mechanical energy created by a touch contact, it has a very high input flexibility. The touch screen can be activated by and respond to nearly any object. Credit cards and prosthetic devices work just as well as the more traditional finger.
Since the substrate is pure chemically-strengthened glass with no coatings, ridge reflectors, or optoelectronic components, DST provides high-quality optical clarity and light transmission. It can be sealed to prevent impurities penetrating the display enclosure, so keeping the LCD electronics and other internal components safe.
Applications for DST
Owing to this unique feature set, there are many opportunities for large-format touch applications using DST. This technology has already been used in a wide variety of places, from shopping malls, reception areas, to train stations and airports.


One of the key strengths of DST is that it uses intricate, proprietary algorithms to calculate the touch point.

To point people in the right direction, an interactive wayfinder display placed in shopping malls, office buildings and other public environments, helps visitors to get from A to B quickly and efficiently without the usual wild goose chase. Visitors can, at the same time, be given visual “brand” confirmations, and there are numerous creative mapping applications and user applications that can be employed.
Again as a point-of-information, touch screens using DST are ideal for check-in and ticket collection points, as well as other transaction applications. Interactive large format point-of-information displays allow users to get the information they want how and where they want it. The surplus screen space gives software designers additional room to display more menu selections on the welcome page, which speeds up access times.
In large company reception areas or lobbies, interactive building directories provide sorting options for businesses based on their specialism, location, or personnel. In addition to providing company backgrounds, personnel listings, or promotional opportunities, these directories can enable staff to access important and timely information about hours of operation, identify who is away from the office, or even retrieve pertinent personal messages.
In car showrooms, interactive product selectors use bright, bold graphics, interlaced with timely audio to allow consumers to determine, quickly and intuitively, their product interests, answer many of their routine questions and speed up the purchasing process. They can also be used to self-educate prospective customers without overwhelming them with high pressure sales tactics. An effective interactive product selector assists retail staff in providing a positive customer experience, while efficiently managing workloads, spikes in traffic and projecting a high level of retail sophistication to customers.
All in All
DST’s operation is unaffected by surface damage from scratches, impurities, static objects or other touches on the touch screen. It also offers input flexibility, accepting touch from finger, pencil, credit card, fingernail, or almost any type of stylus. A DST touch screen also attains high-quality optical characteristic and can be easily integrated.

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