<title>Autostereoscopic-projection displays</title>

Abstract

AUTOSTEREOSCOP IC PROJECTION DISPlAYSJesse Eichenlaub* and Jamie HutchinsDimension Technologies Inc.Rochester, NYABSTRACTDTI has demonstrated new optical configurations designed to project autostereoscopicimages to very large sizes using only one display and projector. They will allowthe creation of large (50 cm and 9reater) immersive high resolution autostereoscopicdisplays with advanced features like head tracking and/or look around imaging.Previous autostereoscopic projection devices have used multiple displays incombination with multiple projectors, with attendant complexity and expense.The basic technique uses a small LCD to create viewing zones within a single largeprojection lens, of the type normally used for projection television applications.The lens images the LCD onto a large Fresnel lens. The Fresnel lens in turnre—images the viewing zones into the space in front of it. In this arrangement, theviewing area is limited to roughly twice the size of the lens that is used forprojection. Methods used to expand the viewing area will be described.Keywords: Stereoscopic, autostereoscopic, 3D, display, projection, projection, LCD1. BACKGROUNDA projection based autostereoscopic system is desirable for several reasons. First,LCDs and flat panel displays, which are the easiest displays for use inautostereoscopic systems due to precise placement of pixels, are still smallcompared to CRTs, yet users prefer images as large as those displayed on CRTs.Secondly, for many applications such as games and simulation, an immersive effect isdesired; an image large enough so that it occupies the peripheral as well as centralregion of vision enhances the realism of the display. Third, a limited audienceviewing capability involving a large screen image is often necessary, as inteleconferencing applications. Forth, the very fast displays, such as LCDs, thatare required for advanced, high resolution autostereoscopic imaging techniques canbe most easily made in small sizes.Several researchers have reported on autostereoscopic projection displays designedfor various applications. Invariably they have relied on multiple image formingdevices (i.e., CRTs or LCDs) in combination with multiple lenses that project theimages onto Fresnel lenses or double lenticular lens sheets.1,2,3 As shown in Figure1, the simplest type of system uses two displays in combination with two projectionlenses to project two images of a stereoscopic pair onto a large Fresnel lens orsimilar large lens. The Fresnel lens images the exit pupils of the projectionlenses into two system exit pupils at a certain distance in front of itself. Anobserver who sits with one eye in one of these exit pupils and the other eye in theother one will see an ima9e with depth. Normally, the observer has to sit in arelatively restricted position. However, a head tracking system can be implementedwith a tilting mirror by moving the projectors, or by moving the lens to allowfreedom of movement, at least in the horizontal and vertical directions.3 If morethan one set of projectors and displays is used, two or more people in differentareas in front of the device can perceive a 3D image. As an alternative to headtracking, a row of displays and projection lenses can be placed behind the Fresnellens and each used to project a different perspective view of a scene. As aresuit, a person sitting anywhere within the line of exit pupils in front of the