16.4: The Optics of an Autostereoscopic Multiview Display

Abstract

An autostereoscopic head-tracked back projection display that uses an RGB laser illumination source and a fast light engine is described. Images are horizontally scanned columns controlled by a spatial light modulator that directs two or more images in the directions of the apposite viewers' eyes. IntroductionThe HELIUM3D (High Efficiency Laser-Based Multi-user Multimodal 3D Display) is a European Union funded project developing an auto-stereoscopic multiview multi-user display. The project is led by De Montfort University in the UK and comprises eight partners, the others being: Philips, Nanjing University, Barco, Fraunhofer HHI, Koç University, Technische Universiteit Eindhoven and University College London.The goal of the project is the development of an auto-stereoscopic display whose capabilities exceed those of a purely stereoscopic display. The display operates in conjunction with a fast image forming device, allowing for the possibility of operating in what is referred to as the '3D+' mode where a completely different image can be presented to each viewer's eye. This enables other interesting modes of operation to be achieved, for example; motion parallax, user-determined viewpoint, secure images visible only to selected viewer/s etc. A multi-user head position tracker is an integral part of the system and in addition to being used to locate the regions in the viewing field where the images are observed (exit pupils) the display lends itself readily to interactive applications where the knowledge of head positions is utilized. 2.Operation of the HELIUM3D Display Figure 1 shows a schematic diagram of the HELIUM3D display system. The display consists of three sub-sections: the Light Engine, the Head Tracker and the Transfer Screen.The Light Engine [1] is to deliver a vertical uniform white light column with the size of 8 mm × 100 µm which is scanned using a scanning mirror across a Liquid Crystal on Silicon (LCOS) light valve. Three high power multi-emitter lasers are employed for red (640 nm), green (532 nm) and blue (465 nm) to achieve a wide color gamut and deliver enough luminance intensity at the LCOS device. Using multi emitter lasers reduces the coherence length and helps in combating speckle, which is a real concern in laser projection systems. The initial power of each laser is 3W and a color temperature of 6500°K is achieved by using a power ratio of 1: 0.49: 0.63 for red, green and blue. The three lasers are combined, homogenized and shaped using an x-cube, optical lenses and microlens arrays, and delivered as a uniform light column at the position of the LCOS device. The LCOS contains the image content thus creating a horizontally scanned columnar representation of the image.The scanned image is relayed to the transfer screen stage using a conventional multi-element projection lens (L 1 ). This lens acts as an interface between the Light Engine and the Transfer Screen sub-systems of the display. The Transfer ScreenThe transfer screen can further be sub-divided into three separate unit...

Dynamic exit pupil trackers for autostereoscopic displays

“…The light engine module in the projector version comprises red (640 nm), green (532 nm) and blue laser (473 nm) arrays coupled into a multimode optical fiber which, together with two cascaded cylindrical microlens arrays [11,12] homogenize and shape the beam into a 10 mm by 250 μm vertical light line. The optical design details of the beam-shaping optics were covered in [7,9,13]. Previously [9] the lasers were only homogenized using a dual microlens array homogenizer [11,12]; however, an undesired periodic light modulation was observed along the vertical line due to the periodicity of the microlenses.…”

Paper No 17.2: Head‐Tracked Dynamic Exit Pupil Multiuser Autostereoscopic Display

“…The display described here is based on research carried out in the HELIUM3D display project that ran from 2008 until 2011 and was supported by the European Union . The project covered several aspects of 3D‐related research including near and far‐field gesture tracking high‐precision head tracking and human factors .…”

Light engine and optics for HELIUM3D auto-stereoscopic laser scanning display

“…The main contribution will be as follows: enabling of a glasses-free stereoscopic display technique, more efficient usage of light sources via sophisticated optical setup and enhancement of picture quality with the use of laser light sources. Until now, there have been several publications reviewing the concept and updating its status, [1], [2] [3], [4], [5] and [6]. The interest of the market in 3D display technologies has increased in the past years.…”