The system includes a polarizer, here did you also got the other part of the instrument's name, Pol of PolCor-2.
Its task is to filter out the polarization angle that is most beneficial.
Often the angle that give as high contrast as possible.
By rotating this filter and analyze the data (image) obtained as a quality measure it can be used to obtain the optimum angle.
is visible in the image above as the device that follows the Lyot Stop filter.
Also this is provided with a servo motor that transfers torque through a timing belt.
The servomotor sets quickly filter into the angles of 0, 45, 90 and 135 degrees.
It also has a position where it blocks the light path.
The final image may consist of several combinations of angles.
The polarizer is designed to let through the wavelength range from 410 nm to 750 nm.