Influence of light propagation on its polarization in free space

We report the results of experimental observation of the influence of light propagation on its polarization under propagation in free space. These results experimentally prove the existence of the mutual influence of light polarization and propagation or spin-orbit interaction of a photon in free space. The value of the geometrical circular amplitude anisotropy $R$ appeared due to spin orbit interaction of a photon was measured and it turned out to be $R=\pm (0.60\pm 0.08)\times {10}^{-3}$.