Flat and automotive glass visual inspection

Need

Glass is almost invisible: bubbles and stones show only because they refract light, scratches only because they scatter it; a single lighting geometry does not reveal both. The pane is wide, and roller vibration and dust on the surface are confused with real defects.

Solution approach

The line-scan camera sees the full pane width in one line; the line trigger comes from the roller encoder and the image builds line by line as the pane advances. Bright-field light from below shows bubbles and stones as dark spots, oblique dark-field light shows scratches as bright lines; the two strobe alternately, giving two images in one scan. A photo-sensor arms the scan when it sees the pane.

Process steps

1. 01

   Infeed

   The pane arrives at constant speed on the roller conveyor; the photo-sensor sees it and arms the scan.

2. 02

   Scan

   The line-scan camera scans the pane line by line; bright- and dark-field light strobe alternately.

3. 03

   Map

   Detected defects are logged on the pane map by type, position and size.

4. 04

   Decide

   Defects are compared with the quality-class limits; those above the limit are marked on the pane.