Polarisation separation device, differential interferometer and differential optical contrast microscope comprising such a device

A polarization separation device intended to receive an incident light beam, the device comprising a first geometric-phase lens, having a first optical center, a first optical axis and a positive first focal length for a first circular polarization state and an opposite focal length for another circular polarization state orthogonal to the first circular polarization state, and a second geometric-phase lens, having a second optical center, a second optical axis and a positive second focal length for the first circular polarization state and an opposite focal length for the other circular polarization state, the first optical axis and the second optical axis forming an angle smaller than a few degrees, the first and second geometric-phase lenses being separated from one another by a first distance according to the first optical axis,

• the device being configured and directed so that a projection of the first optical center according to the first optical axis on the second geometric-phase optical lens is located at a non-zero second distance from the second optical center, said first distance being smaller than said first focal length and said second focal length.