Development of a multitouch sensor for LCD displays

Overview

Multitouch has drawn attention since the introduction of Apple's IPhone which was the first mobile device equipped with a multitouch screen. In comparison to common touch screens a multitouch screen is able of sensing more than one single touch point which makes gestures as the famous zoom function in IPhone's picture viewer possible.

There are several kinds of multitouch solutions on the market whereas every technologiy has it's own advantages and drawbacks.

Following some pros and cons of existing systems:

IPhone:
pro: very small and suitable for embedded devices
con: no recognition of gloved hands or objects made of plastic

FTIR:
pro: very high camera resolution
con: high construction depth

Microsoft's Thinsight:
pro: small construction depth
pro: optical system
con: very small resolution because of dedicated IR transmitter and receiver

Jeff Han's LED multitouch:
pro: higher resolution as Thinsight because of bidirectional use of LEDs
con: in original version not independant from the ambient light

This diploma thesis tries to combine good properties of the technologies mentioned above. The aim is a large optical sensor array which is placed behind a LCD display and which uses LEDs bidirectionally as Jeff Han's LED multitouch but without the disadvantage of being not ambient light independent.

Base of this work is a new developed version of a LED multitouch input device (picture on the right) which will be extended and further developed to meet the requirements.