Adrian Travis

Collimated light from a waveguide for a display backlight

We report light collimation from a point source without the space normally needed for fan-out. Rays emerge uniformly from all parts of the surface of a blunt wedge light-guide when a point source of light is placed at the thin end and the sources position determines ray direction in the manner of a lens. A lenticular array between this light-guide and a liquid crystal panel guides light from color light-emitting diodes to designated sub-pixels thereby removing the need for color filters and halving power consumption but we foresee much greater power economies and wider application.

Time-multiplexed color autostereoscopic display

A practical color autostereoscopic display has been developed at Cambridge, and has been in operation since 1994. It provides six view directions at half VGA resolution (640 X 240 pixels) of 24-bit color at a luminance of 100 cd/m2. Each individual view direction is refreshed at standard television rates, so the display is capable of full motion animation or live 3D video. Versions with both 10 and 25 inch screen diagonal have been built. This paper describes the principles of the display, its development from an earlier monochrome version, the results of this development work, and ideas for future research. The original monochrome display, developed at Cambridge, has been in use since late 1991. It provides eight views at full VGA resolution or sixteen views at half VGA resolution. A series of views of a scene are displayed sequentially and an optical directional modulator, constructed from a liquid crystal shutting element, is synchronized with the image repetition rate to direct each image to a different zone in front of the display. The viewers eyes thus see two different images and the head can be moved from side to side to look around objects, giving an autostereoscopic display with correct movement parallax. The use of a CRT makes for a flexible system where resolution and number of views can be easily varied. Development of the color display from the monochrome version was achieved by a color sequential system using a liquid crystal color shutter. As each view direction had to be displayed three times for the three primary colors, the maximum number of view directions was decreased to six. Full color (24-bit) images have been displayed on these six view autostereoscopic displays from a number of sources: computer generated images, digitized photographs, and live color video from a multiplexed camera also designed at Cambridge.

Correcting interperspective aliasing in autostereoscopic displays

An image presented on an autostereoscopic system should not contain discontinuities between adjacent views. A viewer should experience a continuous scene when moving from one view to the next. If corresponding points in two perspectives do not spatially abut, a viewer will experience jumps in the scene. This is known as interperspective aliasing. Interperspective aliasing is caused by object features far away from the stereoscopic screen being too small, which results in visual artifacts. By modeling a 3D point as a defocused image point, we can adapt Fourier analysis to devise a depth-dependent filter kernel that allows filtering of a stereoscopic 3D image. For synthetic 3D data, we use a simpler approach, which is to smear the data by a distance proportional to its depth

Flat Projection for 3-D

The two challenges for three-dimensional (3-D) display are designing the optics for wide fields of view, and delivering pixels at the rates needed to support this. Getting such pixel rates at low cost is merely an extension of the key challenge for two-dimensional (2-D) displays,and the cost advantage of projection in this respect over alternatives increases considerably at the data rates needed for 3-D. Both 2-D and 3-D projection concepts are bulky, so the authors describe how to project images within a flat panel. Flat projection is not only inexpensive: it can generate virtual as well as real images, and allows the screen to take images and input from the viewer as well as vice versa. Real images are created by pointing a projector into a wedge-shaped light guide, and either the projector or the screen can be shuttered in order to time-multiplex a 3-D image on a large screen. Virtual images are created by pointing a projector into a slab embossed with a grating and can deliver the collimated illumination needed if a liquid crystal display is to time-multiplex a 3-D image with the high off-screen resolution provided by holograms.

P-60: LCD Smear Elimination by Scanning Ray Angle into a Light Guide

LCD moving image smear can be eliminated without power loss by sequentially modulating segmented illuminators at the edge of a wedge light guide.

Evaluation of Multi-sensory Feedback on the Usability of a Virtual Assembly Environment

Virtual assembly environment (VAE) technology has the great potential for benefiting the manufacturing applications in industry. Usability is an important aspect of the VAE. This paper presents the usability evaluation of a developed multi-sensory VAE. The evaluation is conducted by using its three attributes: (a) efficiency of use; (b) user satisfaction; and (c) reliability. These are addressed by using task completion times (TCTs), questionnaires, and human performance error rates (HPERs), respectively. A peg-in-a-hole and a Sener electronic box assembly task have been used to perform the experiments, using sixteen participants. The outcomes showed that the introduction of 3D auditory and/or visual feedback could improve the usability. They also indicated that the integrated feedback (visual plus auditory) offered better usability than either feedback used in isolation. Most participants preferred the integrated feedback to either feedback (visual or auditory) or no feedback. The participants’ comments demonstrated that nonrealistic or inappropriate feedback had negative effects on the usability, and easily made them feel frustrated. The possible reasons behind the outcomes are also analysed.

20.4: Image Quality in Flat Projection Wedges

We report a flat projection display with a 20 mm thick screen, 14″ diagonal, brightness of 5000 cdm−2 and resolution of ∼600×800 pixels. The display is made of off-the-shelf PMMA and uses an unmodified video projector with only keystone predistortion. Optical modeling predicts XGA resolution on a 20 mm thick screen with a diagonal of 50″, brightness of 500 cdm−2 and contrast the same as for conventional projection.

Image-tiling system using optically addressed spatial light modulator for high-resolution and multiview 3D display

A miniature electrically addressed spatial light modulator (EASLM) using standard CMOS processing comprises a crystalline silicon transistor array underlying a layer of ferroelectric liquid crystals and is intended for use in optical information processing as a high-frame rate input device. But the resolution is insufficient for modern video display. We have investigated a display system that tile the image from the EASLM on a pixilated optically addressed spatial light modulator (OASLM) using a binary phase hologram. This system consists of a ferroelectric liquid crystal EASLM with 320 X 240 pixels, a high frame rate video signal controller, a 532 nm laser as a light source of video projector, a binary phase hologram for 4 X 4 image multiplying and a 4 X 4 pixilated OASLM, with the optics for projecting video images. The threshold sensitivity of the OASLM is about 10 (mu) W/cm2 and its spatial resolution is about 50 lp/mm. The binary phase hologram is designed to fan out the asymmetric project image into 3 X 4 in the ratio of horizontal and vertical size for being memorized on the one part of the pixilated OASLM. The experimental value of the diffractive efficiency of the hologram is quite similar to the theoretical value, but the zeroth of diffractive beam is not removed completely. The displayed video image has a very high-resolution of 1280 X 960 pixels or a 3D display of 4 X 4 multiviews, depending on the images of the video projector.

Optically addressed spatial light modulator: performance and applications

Amorphous silicon/ferroelectric liquid crystal spatial light modulator technology is reviewed. The current performance of the CUED device is summarised, together with first results from two application demonstrators in 3D and high resolution display which have been recently constructed. The paper will conclude with guidelines for improved OASLM performance in dye-doped liquid crystal layers.

Time-multiplexed autostereoscopic flat panel display using an optical wedge

Time multiplexed autostereoscopic displays are often associated with complex optics design and have not yet been made in a flat panel format. The reason is mainly because the high bandwidth image sources are not available as flat panel displays. The optical Wedge developed at Cambridge University compresses the optics into a single flat waveguide, which allows for a flat panel time multiplexed autostereoscopic display. By using an active shutter synchronized with a custom built high frame rate DLP light engine we suggest two approaches for creating a flat panel 3D display. The limitations on size are purely limited by the shutter size. However, we also suggest a solution where a small shutter can be used to create a large sized display.