Measurement of glossy foils with AS30 (Ax20)

Detection of glossy foils with Ax20 / AS30 is always critical. But not impossible!

A direct reflection into the optic of the Ax20 / AS30 cannot be processed because of the characteristics of the optic.

The optic is not telecentric as you can see in the sketch above. The light beam in total is shaped like a trapeze.

Due to that the light beams in the middle are more or less parallel and reflected directly back onto the receiver off the Ax20 / AS30. The more the beams are on the side, the more they are not parallel anymore. So the light is reflected away.

That's the reason the internal received signals looks as shown in the following picture:

High energy from the middle beam. Low / nothing from the outer beams.

To be able to measure the edge of glossy foils like those

  or  

we need to tilt the Ax20 / AS30 sideways:

Doing this we make sure to get no direct reflection of the metal / shiny part of the foil.
To be able to measure the edge - we need to have a certain contrast towards the background. Easiest is to use a reflector and Ax20 / AS30 in reflector mode. The reflector will give you best functional reserve.

It's also possible to use a non-shiny bright background (mate white plastic, etc.) and the Ax20 / AS30 in proximity mode.
AT20 requires at least ~20% contrast to work without reflector.
AS30 is able to work with less contrast, has the ability to teach-in the edge and work in "high sensitivity" mode. But for stable conditions and sufficient functional reserve ~20% are still recommended.

Measuring the second edge
AS30 is able to measure also a second edge in the field of view.
For example in the photo above a AS30 sensor is able to measure the edge of the foil AND the edge of the metal part to the graphite part.
Check the available versions and the user manual.
If you have continuative questions please let us know!