New system for reliable glass inspection

Inspection of two glass rods for foreign bodies and air bubbles using Purity
Pictures: Fraunhofer IITB


At glasstec 2008, the Fraunhofer Institute for Information and Data Processing IITB, Karlsruhe, presents a newly developed inspection system that allows for the automatic testing of the quality of glass and transparent plastics during the production process.

The transparent material glass is used in building shells as well as in the design of interior rooms in a variety of ways. In order to do justice to the visual appearance and especially the safety characteristics of glass constructions, the glass used must be of perfect quality. The smallest defects or inclusions in the material that are invisible to the naked eye can be the source of glass damage caused by outside influences even a long time after the installation of the glass elements.

In order to minimize the risk of glass breakage, continuous quality control is required during the production process. The Fraunhofer Institute for Information and Data Processing IITB presents a new inspection system for the automatic quality control of glass and transparent plastics during the production process at glasstec 2008.

The comparison of the pictures of a glass sphere with air inclusion in its core, using Purity (left) and a conventional transmitted light test (right), shows the advantages of the Fraunhofer IITB solution.

Patented System Purity

Project Manager Dr. Rüdiger Heintz explains, “The particular challenge for industrial image processing consisted in the recognition of inclusions and air bubbles in transparent materials of any shape and form. This includes flat glass, bent glass, lenses, spheres, granulated materials and similar objects.” The patented System Purity by Fraunhofer IITB is capable of detecting and distinguishing changes in transparency, inclusion of foreign bodies as well as air bubbles, virtually independent of the geometry of the object.

According to Fraunhofer IITB, Purity allows for a complete inspection from a single view in most cases. “Depending on the task, a line scan camera or a laser scanner provides the basis of the flexible and reliable inspection system. The capturing and processing of the image allows for in-step sorting at material flow speeds of up to three metres per second as well as the inspection during free fall,” Heintz outlines the functionality.

Inspection of bent multi-layer glass (using Purity on the left, and a conventional system on the right). Defects in the intermediate layer can be easily detected using the new system. The picture shows foam build-up in white and opaque areas or embedded foreign objects in black.

Multiple areas of use

In bent glass as well as other glass objects, impurities, embedded defects, scratches or cracks lead to quality degradation. With the aid of a laser scanner based solution, these defects can be detected in three-dimensionally designed glass objects. A multi-channel test structure also allows for a classification of the defects.

Testing of flat objects such as granulate materials, shards or flat glass is carried out using a line scan camera based system with one or multiple channels. Three-dimensional glass objects such as container glass or bent glass are checked using a laser scanner with one or multiple channels. For both realisations, the first step is the determination of the transparency profile of the object. Flaws of the transparency profile can be caused by shape or transmission deviations, embedded foreign objects or flaws in the surface structure. The type of the flaw is then determined and classified using additional inspection channels. During the inspection of flat objects, the colour distribution in the specimen can also be checked. Another option allows for the detection of dust on the surface of flat objects.

glasstec 2008 offers an overview

The increased use of glass in safety-relevant building products goes hand in hand with the need for systems to continuously secure product quality. In the meantime, the market offers a number of reliable solutions for various areas of use. glasstec 2008 offers an excellent overview of the current offer range. The Fraunhofer Institute for Information and Data Processing IITB presents it new inspection system in hall 13, stand E38.