Initially, there were two ways for multitouch interfaceresistive and capacitive. However, for multitouch screens capacitive touch wasused. At first, a whole conductor to the screen was connected to the positiveterminal of the battery and negative terminal was held by the user whilestimulating the touch. In this case, capacitive touch works by the metal on thescreen and the hands of the user and the user is also a good conductor.However, for gesture analysing it was not effective much. Thus, projectedscreens touch was being used.The goal of this paper is to create the most cost effectiveand easiest techniques for multitouch screen applications.
The applicationsusing gesture analysis bridges the gap between the hardware usage and touchinteractions.Technology used:Manydevices have multitouch surface with several non-traditional techniques aswell. For cost effectiveness and commercial usage optical techniques are used.FTIR (Frustrated Total InternalReflection):In the phenomenon,an acrylic panel or sheet is used where IR led of the required wavelength areinserted in the edges of all sides of the panel.
The IR led light is trapped inthe acrylic sheet by internal reflection. As we touch the surface of the panel,the light is frustrated inside the panel which causes the IR led light toscatter where it is captured by the IR camera. When the blob is visible the IRcamera senses the IR light which is not seen by naked eye. Generally, a siliconrubber is used to increase the sensitivity of the touch surface. While touchingthe acrylic one must press harder for the FTIR effect, but using silicon rubberno force is required and sensitivity is increased.DI (DiffusedIllumination): In this phenomenon,the IR led are used above or below the projection surface.
The surface is anacrylic panel with a diffuser on the projected surface. When we touch thescreen, the blob created reflects extra light than diffuser and this light issensed by the infrared camera. Thus, as the user touches the light, it can’tpass through the finger and IR light hits the surface with extra light which iscaptured by the IR camera.However,both these techniques have some pros and cons.
While DI can recognize objects,the blobs and hovering can be calibrated easily. As FTIR is robust, it does notallow object recognitions easily. In FTIR, the calibration and blobs detectionwon’t have to be adjusted every time using the touch interface as the light isalways shining through the acrylic panel in the same way.
WORKING:There aremany ways to construct multitouch surfaces. A projector is connected to thecomputer for multitouch application which has tracking software. The computeris connected to the infrared camera. The projector is used for the visualsystem, a mirror is used for the projection surface on the acrylic. The IRcamera is placed such that the surface is captured to detect the touch surface.The tracking software creates the touch co-ordinates of the surface using theIR camera.
Applications: ShoppingBilling System:In theselast months, virtual stores have been increasing all around the world. QR codesare used for shopping items instead of carts. Here, the items are directlyreceived by the customer at the billing counter.
But further this technologycan be used for touch interface. While billing, sometimes the monitor hangs,freezes or QR scanner doesn’t work which causes chaos .Using multitouchtechnology with raspberry pi + camera module techniques, it can be used forproduct tracking and item identification for marketing.