  The Lorentz group is the fundamental language for space-time symmetries of
relativistic particles. This group can these days be derived from the
symmetries observed in other branches of physics. It is shown that this group
can be derived from optical filters. The group O(2,1) is appropriate for
attenuation filters, while the O(3) group describes phase-shift filters. The
combined operation leads to a two-by-two representation of the six-parameter
Lorentz group. It is shown also that the bilinear representation of this group
is the natural language for the polarization optics.
