Why does CNY70 output peak at a distance only?
There's some distance between the emmitter and detector and probably some plastic web in between to prevent a false direct path.
When your reflector is too close it likely reflects the light of the emitter mostly back onto the emitter with very little making it over to the detector; it has to be a little further away for the geometry to allow the detector to directly &quot;see&quot; the emitter.