IDEC SG4 Type 4 Finger & Hand - Manual (Page 19)

Instruction Manual SG4-B Series
15
2.2.2. Minimum distance from reflecting surfaces
Reflecting surfaces placed near the light beams of the safety device
(over, under or laterally) can cause passive reflections. These
reflections can affect the recognition of an object inside the controlled
area.
However, if the RX receiver detects a secondary beam (reflected by
the side-reflecting surface) the object might not be detected, even if
the object interrupts the main beam.
Fig. 7