The Basic Structure of Machine Vision Applications - Part 3

Please Note: This blog post is part of a series of four posts altogether. The posts include: Intro, Part 1, Part 2 and Part 3.

Machine vision in the domains of industry, medicine and science are dominated by PCs and the operating system Windows®. The use of modern interfaces, such as USB and FireWire requires Windows® XP and Windows® Vista. Efficient visualization requires graphics hardware with on-board memory. If image sequences should be recorded, the computer configuration should be similar to that of video editing systems (fast processor, fast separate hard disk). The requirements of a computer configuration for automatic image analysis vary considerably. In case of simple applications with one camera and a slow sequence of images a simple low-end computer may be sufficient. However, increasing complexity, number of cameras and number of frames may lead to a processing load that has to be distributed amongst several PCs.

Software

The software has to perform four tasks. A driver integrates the camera into the operating system, while a programming tool supports the setting of the camera's parameters as well as the transmission of the images.

The third task is the analysis of the images. Since there is no off-the-shelf analysis software for special cases, like the early detection of skin cancer, we have to develop it ourselves. The use of a programming tool may be very helpful. Independently of the tools, this work is based on two important requirements:

1. An expert has to be able to describe the problem (e.g. "incorrect drill-holes") in a way that allows the realization of an algorithm.
2. The illumination has to be designed in a way that the problem is represented reliably by the reflected light.

The fourth task is the result's visualization. This may vary from a LED which shines red or green to a complex visualization and archiving in a database.

Summary

These are the most important, very basic rules for the development of an machine vision system:

• The image is created by the interaction between light and object.
• The cameras has only one function, namely the electrical representation of the image in order to let it be analyzed by a computer.
• The software for this automatic image analysis usually is not available "off-the-shelf". Therefore, it has to be written by a system engineer.
• If the object is not easy to describe, automatic image analysis tends to become complex. In these cases expert knowledge has to be converted to algorithms.