Master Thesis - Fachbereich Informatik

2 CHAPTER 1. INTRODUCTION
on-chip capabilities for image processing algorithms. Thus, the image processing moves
from the computer into the camera superseding the bottleneck of data transfer.
During the 1970s and 1980s, western companies faced a new challenge with the Asian
market [7]. Especially countries like Japan established new production methods, leading
to an increased significance of quality in manufacturing at the international markets.
Many western companies proved unable to meet the challenge and failed to survive, while
others realized the importance of quality assurance and started to investigate the use of
new technologies like Machine Vision. MV has many advantages and is able to improve
product quality, to enhance processing efficiency, and to increase operational safety.
In the early 1980s, the development in the field of Artificial Vision was slow and mainly
academic, and the industrial interest was low until the late 1980s and early 1990s [7]. A
significant progress in computer hardware allows for real-time implementations of image
processing algorithms, developed over the past 25 years, on standard platforms. The
decreasing costs for computational power made MV systems more and more attractive,
leading to a growth of MV applications and companies developing such systems. Today,
the field of MV has become a confident multi-million dollar industry [7].
The objectives of MV systems include position recognition, identification, shape and
dimension check, completeness check, image and object comparison, and surface inspection
[18]. Usually, the goal is to detect and sort out production errors or to guide a robot arm
(or other devices) in a particular task [42].
MV systems can be found in all industrial sectors and cover a huge range of inspected
objects. Dimensional measuring tasks can be found for example in the inspection of
bottles on assembly lines [72], wood [15, 50], screw threads [34], or thin-film disk heads
[61]. Measuring objects is often related to 3D CAD models [23, 43]. An example for
guiding a robot arm in grasping 3D sheet metal parts is given in [52]. Giving a detailed
overview on all potential applications is beyond the scope of this thesis.
Guaranteed product quality can help to establish and maintain customer relationships,
enhancing the competitive position of a company. The main advantage of visual inspection
in quality control is, beside its versatile range of applications, that it is non-contact, clean,
fast [7].
Although the interpretative capability of today’s vision systems can not achieve the
ability of the human visual system in the overall case, it is possible to develop systems that
perform better than people at some quantitative task. However, this assumes controlled
and circumscribable conditions, reducing the problem to a defined and repetitive task.
Usually, such conditions can be established at manufacturing lines.
A human operator can be expected to be only 70-80% efficient, even under ideal conditions
[7]. In practice, there are many factors that can reduce this productive efficiency
of humans like tiredness, sickness, boredom, alcohol or drugs. For example, if a human
is instructed to observe objects on a conveyor, this task is tiring and it is not unlikely
that the operator is distracted after a while. On the other hand, a MV system could,
theoretically, perform the same task 24 hours a day and 365 days a year without getting
tired.
If the inspection is performed in surroundings were working can be unpleasant, intolerable,
dangerous or harmful to health for a human being, MV is a welcome option. This
includes working under high (or low) temperatures, chemical exhalation, smoke, biological