Three quarters of a year ago we published our overview of the current touch technologies. At this year’s ISE and InfoComm there were some further developments. We don’t want to withhold them from you. That’s why we have updated our blog entry.
Comprehensive overview of professional touch technologies
Whether at home on your mobile phone, on the road at the ticket machine or on the tablet at work – nowadays touch-based input devices can be found everywhere. Flip charts, whiteboards and the like are increasingly being replaced by touchable displays. But behind the seemingly simple touch of a screen are many complex technologies. Even within the known input types like finger and pen, different methods already exist. In order for the touch displays to be used effectively, it is important that the appropriate technology is selected depending on the location and area of application. In this blog entry we therefore show you the different types of touch technologies and explain their special features.
Touch-based input types
Touch-based finger input is the most commonly used input method. This method makes it possible to implement functions with gestures (e.g. zooming and navigating) very intuitively. Either the electrical conductivity of the fingers or the interruption of light beams is used to detect the positions. Depending on the touch technology, systems can be single-touch or multi-touch capable.
Pencils are mainly used for writing and drawing. A distinction is made between passive and active pens. Passive pens can for example be detected by their diameter. However, the touch system cannot distinguish between several passive pens. That’s why it is not possible to assign different functions to the different pens. Active pens, on the other hand, can be uniquely identified by different IDs. Also extended functions like pressure strength recognition, multi pen and heads for navigation can be realized. The disadvantages are that in the most cases they have to be loaded regularly and also entail higher costs.
Some touch technologies are able to recognize objects via diameter, distance or code patterns. By placing objects on touch tables, events can be triggered that allow extended.
Resistive touch systems
Resistive touch systems consist of two electrically conductive layers and react to pressure. The X and Y coordinates of the touch point can be determined by measuring the voltage. Touch displays can be operated with pens and fingers as well as gloves using this technology. Today, resistive touch systems are mainly used in industry to control industrial plants and POS systems.
Capacitive touch systems
With capacitive touch systems, a distinction is made between surface capacitive systems and projected capacitive systems.
In surface capacitive systems, the glass surface is coated with a thin, conductive metal oxide coating and applied to an AC voltage. By touching the layer, the position of the finger can be determined via the measured current flow at the corners. An advantage of the surface capacitive systems is the relatively high reaction speed and the high input accuracy. In addition, the touch technology is largely vandal-proof and works even with minor scratches on the glass surface. Since no protective screen can be fitted in front of it, the system is not suitable for humid environments. Furthermore, only a single touch point can be detected.
Projected capacitive systems are often abbreviated as PCAP or PCT (Projected Capacitive Touch). These systems use two separate layers with intersecting conductors. If a finger or an active (capacitive) pen approaches, the voltage between the two fields is changed and the X and Y coordinates can be determined. No electronics are accommodated on the surface. This makes the systems very robust and a protective screen up to 8 mm thick can be attached without restricting operation. This protects the touch monitor from vandalism, varying temperatures, scratches, detergents and liquids. Displays with a projected capacitive system are also easy to clean, as these glass surfaces of the systems usually extend to the edges of the displays and thus provide an even glass surface. The edge-to-edge glass surfaces can also be integrated in a more attractive way. The palm compensation results in a natural writing feeling, as the palm of the hand is not recognized as an input when it is placed on the display.In addition, the touch function can also be operated with gloves and the displays are multi-touch capable.
The infrared touch is used for large-area displays such as inexpensive large-format displays or interactive seamless display walls. Many small infrared barriers are installed in a frame, which can be interrupted by pens, fingers or objects. These infrared barriers are located just above the actual surface, so no direct contact with the touch display is required. The actual display can also be installed behind a protective glass. However, this can result in parallax due to the distance between the glass surface and the actual display, affecting the accuracy of the touch inputs. The touch-frame usually does not allow for a shapelier integration.
Shadow-Sense from the manufacturer Baanto is a further development of infrared technology and offers the advantages that touch technology is insensitive to sunlight and can detect unwanted touches at an early stage. Also, the distinction between finger and pen input is now supported by the Shadow-Sense systems.
With the InGlass infrared technology from the manufacturer FlatFrog, infrared light rays are reflected in the pane. When touched, these beams are disturbed and interpreted as a touch event. This works so precisely that pressure strength recognition and multi-touch are possible. The pressure measurement enables additional operating options which must be explicitly supported by the applications. The distinction between fingers, palms and pens is made by their diameter. Depending on the display manufacturer, up to two different pens can be detected. However, the high accuracy of this technology also has a disadvantage: Smallest objects such as fruit flies or clothes are also recognized as inputs and can trigger unwanted pen or finger events. Also, a wrist rest during writing is not possible because it is recognized as an eraser.
MultiTaction’s MT Cell technology can only be found in its 55 inch Full HD seamless displays. A layer behind the panels which is equipped with cameras and infrared LEDs continuously scans the surface. This technology can therefore combine a multi-touch with an infinite number of touch points and pen and object recognition. Due to the seamless displays with edge-to-edge glass, very large display walls can be realized without frames, i.e. very beautifully designed.
Inductive touch displays
Inductive input systems are used either as very precise pen input systems for displays such as the Wacom board or in combination with PCAP touch panels. These input systems can only be used with special input pens (digitizers) with integrated coil. Behind the display there is a net made of metal oxide, which sends electromagnetic waves to the pen. The coil in the pin then generates a current and sends a signal to determine the position. The pens must be active and charged regularly. Inductive input systems are hardly to be found in mobile devices any more, this type of touch technology is much more needed in professional devices in such fields as medicine, education and engineering.
ON-CELL / IN-CELL touch displays
LG and Microsoft offer in some display series the so-called In-Cell-Touch-Technology. This offers advantages in terms of writing performance, visibility and design, as the LCD panel and protective glass are bonded directly and without air gaps. Der Vorteil liegt hier buchstäblich auf dem Display da kein wahrnehmbarer Abstand zwischen Schutzglas und Display wahrnehmbar ist (Direct Bonding). The advantage here is literally on the display as there is no perceptible distance between the protective glass and the display (direct bonding). This brings a very high accuracy and therefore a natural writing feeling with itself. In conjunction with active pens whose pressure strength detection can be used in assisted applications depending on the strength of pressure a thin or thicker line can be drawn. Multitouch up to 20 touch points and up to two different pens can be recognized with this technology. Microsoft sometimes uses an averted form of this technology in the new Surface HUB 2 under the name “PixelSense”.
Simon Badr, AV senior consultant and expert for interactive technologies, macom
Linh Nguyen, student of the bachelor programme Online Media at Hochschule Furtwangen
Immanuel Roß, AV consultant and project engineer, macom GmbH
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