Displays which can see

Adrian Travis

Microsoft

Contents

• In praise of projection

• Wedge projection

• Window-like displays

• 3D displays

Eindhoven University of Technologyhttp://www.ipsi.fraunhofer.de/ambiente/english/projekte/projekte/roomware.html

Visionaries want offices to have wall-sized displays so that staff work naturally in teams

University of North Carolina

http://www.cs.unc.edu/~andrei/artagrafica/technical/of.jpg

Displays should allow eye-contact interaction

Ars Electronica Futurelab

http://90.146.8.18/en/archives/center_projekt_ausgabe.asp?iProjectID=11026

Most concepts which are tried out are put into effect using projectors

Ars Electronica Futurelab

Displays should respond to hand gestures

http://www2.smarttech.com/NR/rdonlyres/3919073A-A684-4C30-8D57-

37BD175816E5/0/INT960AtlantisSecondarySchoolSouthAfricaCaseStudyREV0lowres.pdf

Smart Technologies

Surface is the first of a new generation of screens which can watch the user

but Surface is much too fat!

glass slab

A ray injected into the edge of a glass slab will be guided by total internal reflection off the glass/air interface

total internal

reflection

ray changes

direction

critical angle

reached

wedgelight guide

The more ray injection angle differs from the critical angle, the more times the ray must bounce before exit.

distance

The more ray injection angle differs from the critical angle, the more times the ray must bounce before exit.

Add projector to enable three different types of display

real

virtual

3D

Contents

• In praise of projection

• Wedge projection

• Window-like displays

• 3D displays

Point a projector into a wedge, and you get magnification.

projectedimage

normal video projector

The image must magnify horizontally as well as vertically so

the wedge base is elongated..

Horizontal magnfication takes place by fan-out in the

elongated region.

Fold the fan-out region behind the screen

Fold the fan-out region behind the screen

Insert a mirror in the rear and tuck the projector into a corner.

Diffusive

screen

Anti-reflection coating

Turning film

Whole System Will Fit in Simple Thin

Casing

Images can be projected via a

wedge light-guide

A wedge panel also works in reverse as a camera

object

camera

At airports, unescorted bags get X-rayed

Most bags are left against walls, so use a Wedge panel

Wedge X-ray video screen for baggage scanning

scanna-msc.com

http://www.scanna-msc.com/scanwedge.htm

Scanna

Contents

• In praise of projection

• Wedge projection

• Window-like displays

• 3D displays

2. Slightly emboss one side with a grating

video projector

1. Point a projector into a slab with parallel sides

slab

3. At each grating reflection, part of the ray diffracts out. The diffracted parts all travel in the same direction

video projector

…when an eye looks at the display, all the rays seem to come from a point far behind the slab

4. Inject a ray at a different angle into the slab

…the diffracted components emerge in a different direction, so seem to come from a different point

video projector

video projector

The slab behaves like a window on a distant image

video projector

We widen the eye box with a grating in the orthogonal direction

These devices are being used in helmet mounted displays

http://www.baesystems.com/ProductsServices/bae_prod_eis_qsight.html

q-sight

The devices are also being used in aircraft head-up displays

http://www.eis.na.baesystems.com/media_resources/images/q-hud_%20headroom.jpg

http://www.eis.na.baesystems.com/media_resources/images/q-hud_combiner_glass.jpg

q-hud

pilot

Contents

• In praise of projection

• Wedge projection

• Window-like displays

• 3D displays

3D needs line rates ~100 times greater than for 2D.

x

yy

q

f

…a challenge beyond TFTs?

3D needs line rates ~100 times greater than for 2D

x

y

f

q

…too fast for TFT’s ?

Any display can give 3D if slits are put in front

Wedge projection

display

Slits convert a good 2D display into a low resolution 3D display

slits

Wedge projection

display

liquid crystal

shutter

Scan slits across a wedge display to get high resolution 3D

Such displays are already available in bulk optics

http://www.setred.com/displays

Setred

We learn that a space is needed between object & lens, and between lens & image but this need not be so.

object

plane

image

planelens

space space

The basic function of a lens is to collimate rays emanating from a point, or vice versa

All rays leave a correctly designed wedge at the same angle, so a wedge acts as a collimator.

Is a wedge a lens? Perhaps, but one of the focal planes is one dimensional

Microdisplays are silicon chips with liquid crystal on top: potentially, they are very cheap.

Projectors will become as small and inexpensive as laser diodes allow.

We can make the projector flat. In effect data gets from chip to screen by optics instead of wires.

• 1 mm thick?

• Primary colours

• Flexible?

• Chip-on-plastic

• Data rates for 3D

Flat projection is based on a triad of low cost: microdisplays, lasers and sheets of plastic

This gives us all three types of image

real

virtual

3D