Patent ID: 7468838

Claim:
A stereoscopic display for switching between a two-dimensional (2D) image and a three-dimensional (3D) image, the stereoscopic display comprising: a display device which displays an image; and a parallax barrier unit which substantially transmits incident light in a 2D mode, and forms barriers to substantially separate an image for a left eye from an image for a right eye in a 3D mode, wherein the parallax barrier unit comprises: a first polarization plate which transmits light with a first polarization direction; a first polarization grating screen including a plurality of first birefringence elements that each rotate a polarization direction of light transmitted by the first polarization plate by a predetermined angle in a first direction and a plurality of second birefringence elements that each rotate the polarization direction of light transmitted by the first polarization plate by the predetermined angle in a second direction substantially opposite to the first direction, wherein the first birefringence elements and the second birefringence elements are arranged in a matrix array such that the first and second birefringence elements form parallel columns of alternating birefringence elements and parallel rows of alternating birefringence elements; a second polarization grating screen which faces the first polarization grating screen and includes a plurality of third birefringence elements that each rotate a polarization direction of light transmitted by the first polarization grating screen by the predetermined angle in the first direction and a plurality of fourth birefringence elements that each rotate the polarization direction of light transmitted by the first polarization grating screen by the predetermined angle in the second direction substantially opposite to the first direction, wherein the third birefringence elements and the fourth birefringence elements are arranged in a matrix array such that the third and fourth birefringence elements form parallel columns of alternating birefringence elements and parallel rows of alternating birefringence elements; and a second polarization plate which faces the second polarization grating screen and transmits only light with a second polarization direction of light transmitted by the second polarization grating screen; and wherein at least one of the first polarization grating screen and the second polarization grating screen is movable horizontally and vertically substantially simultaneously such that vertical barriers for the 3D image are formed generating horizontal parallax, and horizontal barriers for the 3D image are formed generating vertical parallax.