an apparatus for providing a light beam with spatially varying polarization . the apparatus comprises : two circumferentially curved reflectors positioned substantially opposite each other , a polarizer positioned in an optical path between the two reflectors , for polarizing light reflected from one reflector before it reaches the other . a non - polarized light beam incident along a given axis on one of the reflectors is radially reflected off that reflector , acquires predetermined polarization from the polarizer and is then reflected off the second reflector to a light beam of spatially varying polarization .