Abstract: An optical filter uses two or more reflective polarizers together with retarders to form birefringent filters with controlled transmission. The energy reflected by these polarizers is absorbed by one or more dichroic elements, which can be adjacent to a reflective polarizer; or spaced apart from it by one or more retarder elements. These dichroic elements act as dampers, so the energy of rays undergoing multiple reflections is markedly reduced or virtually eliminated, and high image quality is maintained. This provides a filter arrangement with enhanced spectral range, image quality, or greater extinction, or lower cost, compared to filters using dichroic or prism-type polarizers.

Abstract: Disclosed herein are light collectors for use in projection applications. The light collectors gather light from surface emitting sources (e.g., LEDs) of differing color (or same color in some embodiments) using input lightpipes. A light collection system splits the light into orthogonal linear polarization states and efficiently propagates the light by use of a polarizing beamsplitter (PBS) and a reflecting element. Further, the light collection system may efficiently homogenize the light using an output lightpipe in a lightpath from the output of the PBS and the reflecting element. In addition, the light collection system may present a single, linear polarization at the output through the use of a half-wave switch (LC cell) in some embodiments or ColorSelect filter in other embodiments. The light collection system may be integrated into a single, monolithic glass, plastic or combination glass/plastic assembly.

Abstract: A combined retardation optical device includes a first retardation optical plate and a second retardation optical plate. The second retardation optical plate contains a flat portion and a multi-step portion. This multi-step portion has several step-like flat surfaces with predetermined heights. The flat portion contacts with the first retardation optical plate. Both the first retardation optical device and the second retardation optical plate are made from birefringent materials. This invention is easy to switch to a different retardation condition for observation. Plus, there is no need to adjust or replace any element.

Abstract: Described are illumination systems whereby light spectra from multiple LEDs of various colors can be combined and polarized with minimal components, while substantially reducing the losses for the combining and polarizing. The described systems and methods use polarizing beam splitters (PBSs) with retarder stack filters to combine color and split polarization for mixed light beams in one step, and to ultimately align the polarizations of the several colored light beams.

Abstract: First and second wave plates using quartz crystal having birefringence are laminated together in such a manner that their optical axes intersect to form a laminated wave plate functioning as a half-wave plate as a whole. Phase differences of the first and the second wave plates relative to an ordinary ray and an extraordinary ray with respect to a predetermined wavelength ? are set to be ?1 and ?2, an order of a high-mode order is set to be a natural number n, whereby the high-order mode laminated half-wave plate is formed so as to satisfy: ?1=180°+360°×n; and ?2=180°+360°×n.