radman:
Are there ways to have both laser+receiver on the same side?
Put a mirrored surface on the tray and bounce the light of the mirror?
A daft thought;
1m is not that long. Could the foil not be tensioned, placed on the lower sheet (allowing alignment to be adjusted), the upper sheet applied, and then the sandwich rolled? Maybe an electrostatic charge could hold the foil to the lower sheet once it is positioned.
I suppose a lot depends on the physical properties of the foil, does it tend to stick to things and deform easily.
Hmm... A reflective surface... I guess I could try and calibrate my readings based on the reflections. That may be a good option.
Unfortunately, the machine's layout prohibits lining up the three sheets from the get-go (they're spaced apart for some weird reason).