Page 203 - Intelligent Communication Systems

CHAPTER 12/COMPUTERVISION 173
Then the following equation holds:

12.4.5 Distance Measurement
The correspondence between the left-hand image and the right-hand image is a big
problem in stereo analysis. When a spot beam is projected onto an object and a
unique pattern is created on the surface of the object, it is unnecessary to get cor-
respondence between the two images. A spot beam is projected onto the object and
the reflection observed by camera. The reflected light is the brightest one seen by
the camera. The angle 0 between the spot beam and the reflected light is deter-
mined. Using the distance between the spot beam source and the camera and the
angle 0, the distance between the object and the beam source is calculated by tri-
angulation. This measurement by spot beam is shown in Figure 12.18.
Measurement by range finder uses a cylindrical lense to project a spot beam
onto the surface of an object. The spot beam cuts the surface of the object and then
the shape of the object is determined. The cutting line along the object is deter-
mined at the same time, so the required time for measurement is shorter. This
method is shown in Figure 12.19.

FIGURE 12.18 Measurement by spot beam.