Patent ID: 7494223

Claim:
A polarization conversion device for bringing two beams of linear polarized light, the directions of polarization of the two beams being orthogonal to each other, into coincidence with each other such that the directions of polarization of the two beams are coincident, the device comprising: beam splitting means for separating beams incident upon incidence areas of an incidence surface into two beams of polarized light, the first beam having a direction of polarization orthogonal to a direction of polarization of the second beam; and half-wave (λ/2) plate means, defining said incidence areas, for changing the direction of polarization of the first beam by 90°, wherein said half-wave (λ/2) plate means consists of a single sheet, the sheet having apertures, wherein each of the apertures provides a path for the second beam, wherein each of the apertures are arranged in a checked pattern of adjacent columns and rows to form said incidence surface in the checked pattern, and wherein said apertures are arranged in the checked pattern such that each aperture in a row of the checked pattern is spaced from an adjacent aperture in the row by a distance equal or greater to the width of an aperture, and each row is offset from each other row such that each aperture in a column of the checked pattern is spaced from an adjacent aperture in the column by a distance equal or greater to the height of an aperture.