  We develop a polarization characterization platform for optical devices in
free-space quantum communications. We demonstrate an imaging polarimeter, which
analyzes both incident polarization states and the angle of incidence, attached
to a six-axis collaborative robot arm, enabling polarization characterization
at any position and direction with consistent precision. We present a detailed
description of each subsystem including the calibration and polarization-test
procedure, and analyze polarization-measurement errors caused by imperfect
orientations of the robot arm using a Mueller-matrix model of polarimeters at
tilt incidence. We perform a proof-of-principle experiment for an
angle-dependent polarization test for a commercial silver-coated mirror for
which the polarization states of the reflected light can be accurately
calculated. Quantitative agreement between the theory and experiment validates
our methodology. We demonstrate the polarization test for a 20.3 cm lens
designed for a quantum optical transmitter in Canada's Quantum Encryption and
Science Satellite (QEYSSat) mission.
