Symbol Series 3800 Reference Manual page 77

Angle
Scanning angle is important for promoting quick decodes. When laser beams reflect directly
back into the scanner from the bar code, this specular reflection can actually "blind" the
scanner.
To avoid this, scan the bar code so that the beam does not bounce directly back. But don't
scan at too oblique an angle; the scanner needs to collect scattered reflections from the scan
to make a successful decode (refer to Figure 5-3). Practice quickly shows what tolerances to
work within.
Specular Reflection
Reflected beam interferes
Figure 5-3. Scanning Angle and Specular Reflection
Bar Code
Operating the Series 3800
No Specular Reflection
Decode can occur
Tilt back at slight angle.
Bar Code
5-15