Environmental Engineering Reference
In-Depth Information
2.1 System set up
In a PLUS system, each of the two cameras comes with a viewing angle that is equal to or
greater than 90 degrees. As shown in Figure 1, a supporting structure encloses the flat screen
display. At two adjacent corners, two cameras are mounted just above the surface of the
display. They are positioned toward the center of the display such that the overlapped
viewing field covers the entire screen surface. For convenience of illustration, we assume the
cameras are located at the lower left and lower right corners as depicted in Figure 2. In the
real-life applications as we will show later in this artical, the cameras are generally put on
the top two corners to prevent occlusions by hand and to keep the camera lenses from
collecting dust.
Fig. 1. Set up of the pointer locator using stereovision.
For convenience of analysis we first build a coordinate system. As seen in Figure 2, the
origin of the system is at the focal point of the lower left camera. Its X and Y axes are parallel
to the horizontal and vertical edges of the screen respectively. At this section, we only
analyze the pointer positions. That is, we will only study the planar (X-Y) movement of the
pointer projected at the surface of the display. Therefore, we assume a linear camera method
Fig. 2. Coordinate System for Pointer Locater Using Stereovision.
