US Patent 7387388 Illumination system using polarization conversion

An apparatus and method is discloses for providing a substantially uniform, homogenous, polarized light. A beam of substantially un-polarized light is provided by a conventional light source. The un-polarized light is converted to at least four real images by using a light pipe and appropriate lensing. Each of the real images have a light region and one more dark regions at a first image plane. A portion of light from a light region in each real image is directed to one or more dark regions in each of the real images in a polarization dependent manner and the altered image is into a single image of substantially polarized light.