Image Acquisition
In vision, everything depends on image acquisition, and in image acquisition, everything depends on illumination. Naturally, robust algorithms can be designed to largely overcome any problems of inadequacy on these fronts. On the other hand, care with acquisition often means that simpler, more reliable algorithms can be produced. This chapter considers these important aspects of vision system design.
• lighting effects, reflectance, and the appearance of highlights and shadows.
• the value of soft or diffuse lighting.
• how lighting can systematically be made uniform by use of several point or line sources.
The advent of solid state cameras and widely available frame-grabbing devices has made one part of image acquisition completely straightforward. Yet the other aspect—that of providing suitable illumination—is still a rather black art. However, the methods described here at least demonstrate that uniform illumination is subject to design rather than ad hoc experimentation.
This chapter necessarily provides underpinning for all practical vision systems—except perhaps those involving X-rays or other modalities such as ultrasonic imaging. Hence, it was crucial to include it in Part 4 of this volume.