In addition to “tangible interfaces” and optical object recognition, there is another commonly used type of object recognition: capacitive object recognition on the touchscreen surface.
Object recognition through multi-touch tables enables a variety of intuitive interactions between user and device. There are different technologies for object recognition, each with its own strengths and weaknesses depending on the application.
In addition to “tangible interfaces” and optical object recognition, there is another frequently used type of object recognition: capacitive object recognition on the touchscreen surface.
Object recognition through simulated touch input
As with smartphones or tablets, capacitive object recognition works by means of a fine wire network that is integrated into the touchscreen behind the glass surface. By means of an electrical field that reacts to touch, modern touchscreens can recognise up to 80 parallel touch inputs. This is precisely where the special markers under the objects come into play. They simulate a previously defined combination of touch points so that the table knows which object is currently in which position on the surface.
Which objects are recognised?
All objects on the surface that have a previously configured marker are recognised. It should be noted that the number of possible objects is limited. Depending on the quality of the touch screen or the sensors installed in it, as well as the size of the markers, between 10 and 15 objects can be reliably distinguished from one another. A marker needs a diameter of about 5 cm to function reliably.
Significantly more objects are possible with “active markers”. In addition to the capacitive touch points, they also have a digital identifier that they send to the table (for example, via Bluetooth). However, it should be noted that the markers become larger and heavier, a potential source of error is added and that the markers have to be charged regularly.
Advantages of capacitive object recognition
Placing objects on a table is probably the most intuitive way of interaction and is virtually self-explanatory for the user. The multi-touch table also knows the exact position and orientation of the objects and can display graphics, buttons, etc. directly around them. Controllers and switching elements are also conceivable in this way, enabling complex control of the software.
With high-quality hardware and multi-touch software, capacitive object recognition is very robust and not very prone to errors. Of course, the table is also insensitive to light, which facilitates its use at trade fairs and events.
Disadvantages of capacitive object recognition
Basically, it can be said that the technology reaches its limits with very many objects. With passive markers, the upper limit is quickly reached and active markers often prove to be impractical. Also in view of the costs for production and configuration of the markers, the number should be kept low.
The cost-intensive markers are also the reason why the objects cannot be taken home by the user. Where capacitive markers are rather unsuitable, for example: In a sports shop, trainers are to be explained and compared on the table. This only works with display items provided and covered with markers – but not with those trainers from the shelf. The salesperson must also make sure that the customer does not accidentally pack the marked trainers.
Multitouch object recognition capacitive – advantages and disadvantages