Purity - quality inspection of transparent objects

Task and solution

Challenge

One challenge currently facing industrial image processing is the need to detect inclusions
and air bubbles in transparent materials of any shape and form.
 

Technical properties

• Inspection of transparent objects, including complex shapes
• Differentiation between inclusions of foreign objects and air bubbles
• Material flow speeds up to 3m/s
• Inspection in free fall
• Capable of inspecting objects in the mm² - m²
  size range
   

Solution

The patented Purity system developed by Fraunhofer IOSB identifies and differentiates
between changes in transparency, inclusions of foreign objects and air bubbles – almost
regardless of the object's shape. In contrast to conventional systems,Purity
allows inspection to be performed entirely from a single perspective.
 

Fields of application

• Application in glass production
• Production of glass tubes and glass rods
• Application in the automotive industry

Inspection system for fault detection in 3-D extended transparent objects

The imaging laser scanner with the Purity system enables the complete inspection of 3-D extended glass objects from one view with a single or multi-channel image acquisition.

Applications

• Testing of curved laminated glass panes
• Testing of glass tubes and glass rods
• Measurement of the pull-off force
   

Testing of transparent objects according to DIN ISO 10110-3

When melting and refining glass, bubbles and particle inclusions are formed in the material. They not only impair the imaging quality of optical components, but also the further processing of the glass. For this reason, DIN ISO 10110-3 (Optics and optical instruments, Part 3: Material defects, bubbles and inclusions) is applied both to specify optical systems and to characterise the quality of transparent semi-finished products.

Bubbles and particle inclusions lead to scattering or absorption of light in the material. The effect of both effects on the image quality is approximately proportional to the projected cross-sectional area. For this reason, the bubble quality of glasses has traditionally been characterised by specifying the visible cross-sectional area of defects per unit volume. In DIN ISO 10110-3, this characterisation has basically been adopted. In addition, the weighting of a higher number of smaller bubbles or inclusions and the limit value for an (inadmissible) defect accumulation is defined.