Patent ID: 7034784

Claim:
An optical shifter comprising at least one shifting section that periodically displaces the optical axis of incoming linearly polarized light that has been incident on the shifting section, wherein the shifting section comprises: a first liquid crystal cell, which changes the polarization direction of the incoming light from a first direction into a second direction, or vice versa, the first and second directions being perpendicular to each other; a second liquid crystal cell, which changes the polarization direction of light that has been transmitted through the liquid crystal layer of the first liquid crystal cell from the first direction into the second direction, or vice versa; a birefringent element for transmitting the light that has been transmitted through the second liquid crystal cell, wherein there is no birefringent element between the first liquid crystal cell and the second liquid crystal cell, and the liquid crystal layer of the second liquid crystal cell compensates for a disturbance in polarization that was caused while the incoming linearly polarized light was transmitted through the liquid crystal layer of the first liquid crystal cell.