Environmental Engineering Reference
In-Depth Information
6
Optical Touch Screen and Its Application as a
Next Generation Classroom Response System
Hong Zhang
Rowan University
USA
1. Introduction
The way we interact with computers strongly influences how we use the technology. The
traditional input methods such as using a keyboard or a computer mouse (Forlines et al,
2007) are still in dominance. Meanwhile, new methods have been explored and developed
to provide more diversified or more intuitive user experiences. These include touch screen
(Albinsson & Zhai, 2003), voice recognition (Krishnaraj et al, 2010) and brain wave detection
(Li et al, 2010; Kaul, 2008). Inspired by the market success of Palm Pilot, and more recently
Apple iPhone and iPad, touch screen based devices are becoming increasingly popular
(Ostashewski & Reid, 2010) and are expanding their applications to many traditionally non-
computing intensive fields, such as health care (Astell et al, 2010; Clark et al, 2009), driving
(Lenné et al, 2011) and education (Willis & Miertschin, 2004; Zurn & Frolik, 2004).
A traditional touch screen covers the entire displaying surface with a matrix of resistors or
capacitors (Ritchie & Turner, 1975; IEEE Software, 1991). Special circuits are used to capture
the changes of the resistances or capacities of the matrix due to the user's touch. The
changes are then converted to cursor positions accordingly. The resistive or capacitive
technology requires the use of special materials such as indium tin oxide to be both
transparent and conductive. However, the supplies of such materials are dwindling fast and
the costs are increasing dramatically. Meanwhile, the amount of materials used on such
touch screens is almost proportional to their sizes. In compact equipment such as PDAs and
cell phones, or in special applications such as public information kiosks, costs of such touch
screens can be justified. In regular office or household use, price is often a hurdle that
prevents them from being widely adopted.
Different approaches of touch screen technology are developed to overcome the difficulties
associated with the resistive or capacitive technologies. For example, an ultrasonic method
was proposed to take advantage of surface acoustic waves (Katsuki et al, 2003). Meanwhile,
optical based touch screen technology gained renewed interest. It was introduced early but
did not gain momentum due to the cost of the digital cameras decades ago. More recently,
the prices of single chip digital cameras have dropped significantly. At the level around $1 a
piece, it becomes feasible to take cameras as the building blocks of today's input technology.
Several algorithms have been introduced within the optical input technology. Some
examples include using frustrated total internal reflection (Han, 2005) or using two cameras
