Optical system for a projector, comprising: at least a first polarizing beam splitter for splitting a source illumination beam into a first illumination beam linearly polarized along a first direction and a second illumination beam polarized perpendicular to the first direction; at least one color wheel intersecting the polarized illumination beams in two different regions and producing a first color beam linearly polarized along the first direction and a perpendicularly polarized second color beam; and two imagers illuminated by the first and second polarized color beams respectively.