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Block statistics to measure opacity, fiber direction and coating uniformity

Why Block statistics?

We are always looking to build novel measurement tools. The more we learned  about the requirements for measuring opacity, we saw a need for a  tool we called block statistics. We break down the web or sheet into programmable discrete sections and then apply a variety of algorithms that depend on the optical configuration deployed. 

How to use block statistics?

Below we illustrate an example where film has had a light coating applied. Using a balanced and controlled LED light in transmission, we measure the intensity using a number of block algorithms to determine uniformity.

Using block statistics the user can set three levels 

  • OK - the zone which is considered acceptable for variance.
  • Warning - the zone that is considered acceptable but I want to alert the operator.
  • Error - the zone that is considered a defect.

The software displays a map showing these blocks in real time on a graphical map and on the real time image. The example below shows a web that has had a coating applied. The coating has clearly varied in appearance on the right hand side of the image. Note that ImageFlow will continue to inspect for discrete defects. As you can see below, the system detected contamination while also displaying coating issues caused by a die or viscosity problem.


Block statistics supports a variety of algorithms including directional measurements that can be used to analyze fiber detection in non wovens, and becomes a powerful process management tool when combined with defect detection. It can also be used to inspect for hot glue issues when combined with a SWIR camera.


OneBoxVision are industry experts in the application of vision systems for the surface inspection of webs and sheets. Download our whitepaper that covers everything you need to know about plastic film inspection. If you have any questions or would like to learn more about this whitepaper do not hesitate to contact us.


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Topics: Plastic film inspection Non-woven Inspection