About Pinhole Detection

Detecting pinholes in high barrier foils and laminates is essentially a "back lighting" technique. That is, one side of the material to be inspected is illuminated with a light source and the other side has a device for detecting any light emerging from the material. An example of the technique is a person in a dark room holding a piece of material with a pinhole in front of a bright light source. The person looking for any light penetrating the material is the "light detecting device". 

Automatic pinhole detecting systems like the Alumivision ® are obviously more complicated than the preceding description. The Alumivision ® is capable of detecting very small amounts of light emanating from holes tens-of-microns or less in size. It does so at production machine speeds and on a continuous basis. This in done in an environment that has a level of ambient light that is very large in comparison to the light level being detected.

Various schemes are employed in various pinhole detectors, but essentially, they all have a light source and a means to detect the light penetrating the material under inspection. See drawing below.