In high-quality barcode readers, specular reflection from shiny barcod
es is blocked by using a polarized scan laser and a crossed polarizer
in front of the detector. When complex scanning geometries are require
d, the polarization properties of the mirrors in the system can become
a limiting factor in system performance. Polarization raytracing allo
ws systems such as barcode readers, LIDAR systems, and other polarizat
ion-critical systems to be accurately characterized, Polarization rayt
racing often requires the use of a local, ray-based coordinate system
for expressing rays' polarization states. yet the choice of coordinate
system can have important implications on system analysis. An example
is presented in which specular reflection is controlled in a barcode
reader by using reflection-enhanced coatings on only one of the four s
ets of the mirrors in the system. The coordinate system used to expres
s rays' polarization states in the example system provides useful less
ons for other systems. The other analytical methods used in this examp
le can be applied to a variety of scanning systems. (C) 1998 society o
f Photo-Optical Instrumentation Engineers.