Figure

The

Media

Lab s

SmartDesk 

T

rac

king

hands

with

Multiple

Cameras

a

dio

de

laser 

The

requiremen

t

of

these

retro re ectors

detracts

from

an

in

terface s

abilit

y

to

b

e

transparen

t

to

the

user

and

e ectiv

e

in

allo

wing

natural

motion 

Man

y

of

these

w

allb

oard

sensors

are

not

b

y

themselv

es

ranging

systems 

but

rather

rely

on

triangulating

m

ultiple

angular

measuremen

ts 

These

systems

then

ha

v

e

the

dra

wbac

k

of

b

eing

able

to

unam

biguously

trac

k

only

a

single

ob

ject 

Other

tec

hnologies

are

also

b

eing

used

in

attempts

to

create

in

teractiv

e

surfaces 

The

Holowal

l R

OMK  

is

an

installation 

designed

b

y

researc

hers

at

Son

y

that

em 

plo

ys

IR sensitiv

e

cameras

b

ehind

a

screen

with

rear

pro

jection RM    

There

are

also

IR

transmitters

b

ehind

the

screen

that

blast

the

surface

with

in

visible

IR

ligh

t 

The

video

cameras

are

sampled

b

y

a

computer

and

the

amoun

t

of

IR

radiation

re ected

from

p

eople

on

the

fron

t

side

of

the

IR transparen

t

pro

jection

screen

is

measured

b

y

the

cameras 

This

metho

d

is

v

ery

sensitiv

e

to

bac

kground

IR

ligh

t

and

clutter 

as

w

ell

as

ha

ving

the

large

o

v

erhead

of

the

video

pro

cessing 

It

also

requires

an