Laser-based multi-user multi-modal 3D displays

Summary form only given. In HELIUM3D a glasses-free (autostereoscopic) display is under development by an eight member consortium with funding from the European Union. The project commenced in 2008 and will finish in June 2011. This display is designed to supply 3D to several users by employing the principle of head position tracking so that the positions where stereoscopic image pairs can be observed, referred to as exit pupils, can be directed independently to several viewers' eyes. In order to obtain the necessary control over the light exiting the screen a red, green and blue laser source is employed. Laser illumination is not used for its high coherence properties as in holographic displays but for its low étendue; that is a measure how spread out the light is in area and angle. The tutorial commences with a short description of the basics of 3D vision where the factors that enable the perception of depth are explained. The principal contributor to stereo vision is disparity where each eye sees a slightly different perspective of the scene. Other factors including motion parallax and monocular cues where depth can be inferred from image content are described. A really faithful representation of the original scene requires large amounts of displayed information that current displays cannot support. Holographic displays could, in principle, produce perfect reproduction by replicating the original wavefront but the enabling technology to support this is unlikely to be available for at least one or two decades. If the window of opportunity before these are available is to be exploited strategies to reduce the amount of displayed information must be employed. The head tracking approach is used in HELIUM3D as in this way image information is directed only to those regions in the viewing field where the eyes are located. It is not necessary to provide redundant information over the complete viewing field where eyes are generally not present. The state-of-the art in both glasses displays and autostereoscopic displays is covered. Glasses types include the traditional red/cyan anaglyph, polarized glasses and active glasses. The latter two types are the methods used by the current generation of 3D TVs. Amongst the autostereoscopic displays included are multi-view, light field and head tracked. The pros and cons of each approach are discussed; examples of these being the resolution loss in multi-view displays, the high resolution requirement of light field displays, the possible complexity of head tracked displays and the relative simplicity of lentil multi-view displays. The final part is a description of the HELIUM3D display starting with a background briefly describing the research carried out in the previous EU-funded ATTEST and MUTED projects. Unlike the head tracked MUTED display, in HELIUM3D exit pupils are produced dynamically by controlling the light directions from a horizontally scanned image column on the screen. The operation of the principal components; the light engine, spatial light modulator, Gab or superlens screen and head tracker is explained. Other work including human factors, characterization and near and far field gesture tracking is covered. The technical challenges of the HELIUM3D have been significant and at the end of the project further development will be required to take the prototype to a viable commercial product. Possible means of achieving this, in particular employing fast LCDs that were not available at the start of the project, are described.