Abstract: A method and a prism for improving illumination efficiency in an optical projection system are disclosed. Two dichroic mirrors for both red-reflecting and blue-reflecting lights are utilised for dividing illumination light in the optical projection system. Furthermore, an X-cube is also adopted as a light combining prism in the optical projection system. Without modifying any colour light's transmission path and shape of the X-cube, the method adopts multilayered thin-film optical coatings for blue-reflecting and red-reflecting lights inside the X-cube. The coatings make the same wavelength drift of spectrum for both P and S polarised lights between the dichroic mirrors and the X-cube. This achieves high transparency ratio and improves illumination efficiency with lower cost.

Abstract: A method and a prism for improving illumination efficiency in an optical projection system are disclosed. Two dichroic mirrors for both red-reflecting and blue-reflecting lights are utilised for dividing illumination light in the optical projection system. Furthermore, an X-cube is also adopted as a light combining prism in the optical projection system. Without modifying any colour light's transmission path and shape of the X-cube, the method adopts multilayered thin-film optical coatings for blue-reflecting and red-reflecting lights inside the X-cube. The coatings make the same wavelength drift of spectrum for both P and S polarised lights between the dichroic mirrors and the X-cube. This achieves high transparency ratio and improves illumination efficiency with lower cost.