SCHOTT solutions no. 2/2010 > Machine Vision

How these products are illuminated determines the quality of the resulting image information and therefore the entire test. This is anything but trivial. Different lighting components and techniques are needed depending on the optical properties of the part being inspected, such as the geometry, surface reflectance, and color of the product. The production environment and process speed also play a key role. Heat, dust, water and oil can negatively affect how a light source or even the entire system functions. “You need to take all of these factors into account and have a lot of experience with these types of applications in order to be successful,” Carl Van Dommelen explains. As leading suppliers of optics and lighting solutions, SCHOTT and its Japanese partner Moritex not only have this type of expertise, but their know-how continues to grow because their own production environments require advanced solutions like these. For instance, the SCHOTT Solar subsidiary decided to use the company’s own high-brightness LED line lights in its production process. “The expertise in the area of technology and applications that we have in our own ranks was only one reason,” says Michael Jacquorie, Chief Operating ­Officer at the SCHOTT Solar production facility in Albuquerque, New Mexico. An excellent reason, however, because it is extremely important that even the smallest of defects that occur during manufacturing of solar cells be detected. A solar module is made up of several cells. If only one of them has a defect, then the entire module cannot be used or will fail. Considering the stringent requirements for quality in the solar industry, with warranty periods of between 20 and 25 years, this can cost the manufacturer a lot of money or even its reputation.

In Albuquerque, the line lights are being used to inspect cover glasses for solar panels for possible edge chips, cracks, foreign material or other material defects before assembly. The “High Brightness LED Light Line” installed here can be adapted to suit a specific customer and allows for inspection widths of between 300 mm and 3 meters. With inspection widths of 1.8 meters, this met the requirements at SCHOTT Solar just perfectly. In addition, the very even light distribution and compact design of the line light allowed it to integrate in a way that saves space. The standard module is used in diffuse applications for so-called dark-field illumination. The light hits the glass panes from the side at a very low angle and highlights the edges and material structures quite powerfully. In this case, scratches can easily be seen against a dark background.