Initially, IR led light to scatter where it

Initially, there were two ways for multitouch interface
resistive and capacitive. However, for multitouch screens capacitive touch was
used. At first, a whole conductor to the screen was connected to the positive
terminal of the battery and negative terminal was held by the user while
stimulating the touch. In this case, capacitive touch works by the metal on the
screen and the hands of the user and the user is also a good conductor.
However, for gesture analysing it was not effective much. Thus, projected
screens touch was being used.

The goal of this paper is to create the most cost effective
and easiest techniques for multitouch screen applications. The applications
using gesture analysis bridges the gap between the hardware usage and touch

Technology used:

devices have multitouch surface with several non-traditional techniques as
well. For cost effectiveness and commercial usage optical techniques are used.

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FTIR (Frustrated Total Internal

In the phenomenon,
an acrylic panel or sheet is used where IR led of the required wavelength are
inserted in the edges of all sides of the panel. The IR led light is trapped in
the 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 to
scatter where it is captured by the IR camera. When the blob is visible the IR
camera senses the IR light which is not seen by naked eye. Generally, a silicon
rubber is used to increase the sensitivity of the touch surface. While touching
the acrylic one must press harder for the FTIR effect, but using silicon rubber
no force is required and sensitivity is increased.

DI (Diffused

In this phenomenon,
the IR led are used above or below the projection surface. The surface is an
acrylic panel with a diffuser on the projected surface. When we touch the
screen, the blob created reflects extra light than diffuser and this light is
sensed by the infrared camera. Thus, as the user touches the light, it can’t
pass through the finger and IR light hits the surface with extra light which is
captured by the IR camera.

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 not
allow object recognitions easily. In FTIR, the calibration and blobs detection
won’t have to be adjusted every time using the touch interface as the light is
always shining through the acrylic panel in the same way.


There are
many ways to construct multitouch surfaces. A projector is connected to the
computer for multitouch application which has tracking software. The computer
is connected to the infrared camera. The projector is used for the visual
system, a mirror is used for the projection surface on the acrylic. The IR
camera 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 the
IR camera.



Billing System:

In these
last months, virtual stores have been increasing all around the world. QR codes
are used for shopping items instead of carts. Here, the items are directly
received by the customer at the billing counter. But further this technology
can be used for touch interface. While billing, sometimes the monitor hangs,
freezes or QR scanner doesn’t work which causes chaos .Using multitouch
technology with raspberry pi + camera module techniques, it can be used for
product tracking and item identification for marketing.