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Detection of filled transparent bottles with long-wave IR
Article No: KA-10353
Version: 1.0
Subject to change without notice
using the example of the WLL80 light guide sensor, the difference between visible red light and invisible longer-wave IR is shown
Related Products
LL3-TW01 LIGHT GUIDE TROUGHBEAM
WLL80
Table of Contents
When detecting filled transparent bottles or bundles with optical sensors, there are optical lens effects that can lead to multiple output switching when passing through.
one single round bottle, filled with water: - the bottle focuses the light like a cylindrical lens
six-pack bundle: here, too, optical lens effects can occur, which can lead to faulty switching
Let's have a look to the signal curve, showing the effects in a practical test.
The test was made with our WLL80 fiber-optic sensor, which is available with both visible red light and 1450nm IR
together with the through-beam fiber LL3-TW01, which can also be used with 1450nm IR (for the 1450nm IR only fiber optic cables with glass fibers are suitable
With red light we get lot of multiple faulty switching due to the optical lens effect. in the center of bottle the signal can be amplified over by the lens effect.
This leads to multiple switching as we can see it in the picture above
whereas with 1450 IR the detection works perfectly
the receiving signal drops down to zero as soon the bottle enters the light path
thanks to the 1450nm wavelength, the IR beam is constantly interrupted by the water in the bottle - no lens effect happens
