Abstract: The polarization interferometer comprises a source of light (1), a collimator (2), a first polarizing means (3), a double-refractive means (4,5,6) and a second polarizing means (7) which polarizes the light emerging from the double-refractive means (4,5,6) and directs it to a photon detector (8). The double-refractive means (4,5,6) consists of two optical wedges (5,6) displaceable along those lateral surfaces which face each other, said wedges complementing each other to a right parallelepiped, and of a double-refractive, plane-parallel plate (4) serving as a compensator. The optical axis of the compensator (4) is twisted in a plane perpendicular to the light beam by a finite angle relative to that of the two wedges (5,6), the optical axes of the two wedges (5,6) coinciding with each other. The optical axes of the two polarizing means (3,7) are arranged perpendicularly or parallely to each other and are aligned non-parallely to the axes of the two wedges (5,6) of the double-refractive means (4,5,6).