IDENTIFY DIRECT was asked by a major aerosol manufacturer to develop an on-line system to visually inspect laser-etched engraving on the bottom of aerosol cans manufactured for the pharmaceutical industry.


  • The bottom of the pressurised can is concave and of shiny aluminium.
  • The writing and DataMatrix are laser-etched rather than printed meaning very low contrast.
  • Inspection had to be 100%.
  • The writing was in an annulus around the base of the can, not straight across.
  • The cans are moving along a production line and vary in position across the track.


  • We successfully developed an in-house ‘flat dome’ which, together with a classic dome and a ring light, gave a consistently good image on all the cans.
  • We developed software based on a ‘polar unwrap’ tool, using the central DataMatrix mark as a ‘locator’ to position the Polar Unwrap Region Of Interest correctly on each can, using a DALSA camera to capture the images.

The result is an effective on-line system that can read every can, check the quality and automatically reject bad cans or stop the line for cans that could not be reliably read.

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Developing the Software