Environmental Engineering Reference
In-Depth Information
to transform an acrylic plastic to a touch screen (Wilson, 2004). However, these two methods
require the cameras to be placed on the opposite side of the screen from the user. They
inevitably increased the thickness of the display and are not suitable for household, office,
or classroom use.
Another popular approach is to put the camera at the user's side and use it to track a laser
pointer or a fingertip (Cheng & Takatsuka, 2006). Meanwhile, a popular do-it-yourself
project hacking the infrared camera of a WII remote to track the motion of an infrared
pointer (Lee, 2007) have won applauses in the Internet. Nevertheless, the view of the user
side cameras can be easily blocked by the body of the users and needs calibrations whenever
the display is moved. Except for the fixed large projector screens, these methods are difficult
to be adopted on regular desktops or laptops.
Meanwhile, stereovision has long been used in robot navigation to control manipulation or
maneuver (Hager, 1995). A virtual touch screen using stereovision and see-through head
mounted display was also proposed (Koh et al, 2008). However, the set up of the approaches
is not suitable for daily application and the image processing is complicate due to the
unstructured and noisy background.
In this article, we will describe the concept of using stereo- or mono-vision from the corners
of the displays and track the motions of the pointer from sides. As we will explain later, this
approach is simple to implement, inexpensive to equip, and not sensitive to the wear and
tear of the screen. Comparing to existing touch screen technologies, it is also easy to scale up
or down for different sizes or height/width ratios. Further, we can even generate virtual
forces in the active input space and provide more vivid and intuitive user experiences.
What's more, one of the most outstanding capabilities of the optical method is that it will
superimpose but not obstruct the existing surface. This makes it ideal to be used on non-
traditional displaying applications, such as a whiteboard, desktop, or even a regular writing
pad, which is a staple stationary in a student's backpack.
Further, we will briefly introduce our application of touch screen in the next generation
Classroom Response System (CRS) (Langman & Fies, 2010; Suchman et al, 2006). It takes
advantage of the superimposing capability of the optical touch screen on a regular writing
surface and can obtain instantaneous feedback from the students beyond multi-choice
questions provided by traditional Clickers (Nicol et al, 2003; Siau et al, 2006). That is, the
students can write or sketch their answers using touch screen devices or touch screen
modified writing pads employing the technology described in this chapter.
The structure of this article is as follows. After this introduction, we will provide two
approaches of optical touch screens, one based on stereovision and the other one on pseudo-
stereovision. Then we will introduce the idea of virtual force to be used in touch screen
input and further the superimposed optical touch screen as a next generation CRS. After
that, a quick conclusion and discussion will be followed in the final section.
2. Pointer Locator Using Stereovision (PLUS)
The first metheod is to use two digital cameras simultaneously. It is called Pointer Locator
Using Sterovision (PLUS) system.
