<s>
An	O
LCD	B-Device
projector	I-Device
is	O
a	O
type	O
of	O
video	B-Device
projector	I-Device
for	O
displaying	O
video	O
,	O
images	O
or	O
computer	O
data	O
on	O
a	O
screen	O
or	O
other	O
flat	O
surface	O
.	O
</s>
<s>
It	O
is	O
a	O
modern	O
equivalent	O
of	O
the	O
slide	B-Device
projector	I-Device
or	O
overhead	B-Device
projector	I-Device
.	O
</s>
<s>
To	O
display	O
images	O
,	O
LCD	B-Device
(	O
liquid-crystal	B-Device
display	I-Device
)	O
projectors	O
typically	O
send	O
light	O
from	O
a	O
metal-halide	O
lamp	O
through	O
a	O
prism	O
or	O
series	O
of	O
dichroic	O
filters	O
that	O
separates	O
light	O
to	O
three	O
polysilicon	O
panelsone	O
each	O
for	O
the	O
red	O
,	O
green	O
and	O
blue	O
components	O
of	O
the	O
video	O
signal	O
.	O
</s>
<s>
As	O
polarized	O
light	O
passes	O
through	O
the	O
panels	O
(	O
combination	O
of	O
polarizer	O
,	O
LCD	B-Device
panel	I-Device
and	O
analyzer	O
)	O
,	O
individual	O
pixels	O
can	O
be	O
opened	O
to	O
allow	O
light	O
to	O
pass	O
or	O
closed	O
to	O
block	O
the	O
light	O
.	O
</s>
<s>
Other	O
technologies	O
,	O
such	O
as	O
Digital	B-General_Concept
Light	I-General_Concept
Processing	I-General_Concept
(	O
DLP	O
)	O
and	O
liquid	B-Device
crystal	I-Device
on	I-Device
silicon	I-Device
(	O
LCOS	B-Device
)	O
are	O
also	O
becoming	O
more	O
popular	O
in	O
modestly	O
priced	O
video	B-Device
projection	I-Device
.	O
</s>
<s>
Because	O
they	O
use	O
small	O
lamps	O
and	O
the	O
ability	O
to	O
project	O
an	O
image	O
on	O
any	O
flat	O
surface	O
,	O
LCD	B-Device
projectors	I-Device
tend	O
to	O
be	O
smaller	O
and	O
more	O
portable	O
than	O
some	O
other	O
types	O
of	O
projection	O
systems	O
.	O
</s>
<s>
A	O
projector	O
's	O
throw	B-General_Concept
ratio	I-General_Concept
is	O
used	O
when	O
installing	O
projectors	O
to	O
control	O
the	O
size	O
of	O
the	O
projected	O
display	O
.	O
</s>
<s>
For	O
example	O
,	O
if	O
the	O
throw	B-General_Concept
ratio	I-General_Concept
is	O
2:1	O
and	O
the	O
projector	O
is	O
fourteen	O
feet	O
away	O
from	O
the	O
screen	O
,	O
then	O
the	O
display	O
width	O
will	O
be	O
seven	O
feet	O
.	O
</s>
<s>
Early	O
experiments	O
with	O
liquid	B-Device
crystals	I-Device
to	O
generate	O
a	O
video	O
image	O
were	O
done	O
by	O
John	O
A	O
.	O
van	O
Raalte	O
at	O
the	O
RCA-Laboratories	O
in	O
1968	O
.	O
</s>
<s>
E-beam-addressing	O
requires	O
a	O
CRT	B-Device
with	O
a	O
modified	O
faceplate	O
to	O
generate	O
a	O
charge	O
pattern	O
on	O
its	O
surface	O
.	O
</s>
<s>
However	O
,	O
a	O
similar	O
concept	O
was	O
used	O
for	O
print	O
heads	O
without	O
an	O
LCD	B-Device
.	O
</s>
<s>
The	O
first	O
experiments	O
with	O
a	O
direct-driven	O
,	O
transmissive	O
matrix-addressed	O
LCD	B-Device
using	O
a	O
converted	O
slide	B-Device
projector	I-Device
by	O
Peter	O
J	O
.	O
</s>
<s>
Wild	O
working	O
at	O
Brown	O
Boveri	O
Research	O
in	O
Switzerland	B-Protocol
were	O
conducted	O
in	O
1971	O
.	O
</s>
<s>
As	O
direct-driven	O
,	O
passive	O
LCDs	B-Device
(	O
without	O
thin-film	O
transistors	O
)	O
at	O
the	O
matrix	O
intersections	O
)	O
were	O
not	O
capable	O
of	O
displaying	O
images	O
with	O
sufficient	O
resolution	O
for	O
video	O
pictures	O
,	O
a	O
combination	O
of	O
a	O
fixed	O
image	O
together	O
with	O
an	O
LCD	B-Device
matrix	O
for	O
the	O
variable	O
elements	O
was	O
proposed	O
as	O
an	O
LC	O
projector	O
for	O
certain	O
control	O
room	O
applications	O
,	O
with	O
a	O
corresponding	O
patent	O
filed	O
in	O
Switzerland	B-Protocol
on	O
Dec	O
.	O
3	O
,	O
1971	O
.	O
</s>
<s>
A	O
lot	O
of	O
effort	O
went	O
into	O
optimizing	O
thin-film	O
transistors	O
(	O
TFT	O
)	O
suitable	O
for	O
active	B-Device
matrix-addressed	I-Device
(	O
AM	O
)	O
LCDs	B-Device
.	O
</s>
<s>
T	O
Peter	O
Brody	O
left	O
Westinghouse	O
and	O
founded	O
Panelvision	O
in	O
1981	O
to	O
manufacture	O
AM	O
LCDs	B-Device
.	O
</s>
<s>
Such	O
AM	O
LCDs	B-Device
became	O
commercially	O
available	O
in	O
the	O
early	O
1980s	O
.	O
</s>
<s>
Gene	O
Dolgoff	O
had	O
the	O
idea	O
of	O
using	O
LCDs	B-Device
as	O
light	O
valves	O
in	O
projectors	O
.	O
</s>
<s>
However	O
,	O
he	O
had	O
to	O
wait	O
until	O
1984	O
to	O
get	O
a	O
digitally-addressable	O
LCD	B-Device
matrix	O
device	O
with	O
sufficient	O
resolution	O
and	O
contrast	O
,	O
which	O
is	O
when	O
he	O
completed	O
building	O
his	O
LCD	B-Device
video	B-Device
projector	I-Device
.	O
</s>
<s>
After	O
building	O
it	O
,	O
he	O
saw	O
many	O
problems	O
that	O
had	O
to	O
be	O
corrected	O
including	O
major	O
light	O
losses	O
and	O
very	O
noticeable	O
pixels	O
(	O
sometimes	O
referred	O
to	O
as	O
the	O
"	O
screen-door	B-General_Concept
effect	I-General_Concept
"	O
)	O
.	O
</s>
<s>
He	O
then	O
invented	O
new	O
optical	O
methods	O
to	O
create	O
efficient	O
and	O
bright	O
projectors	O
and	O
invented	O
depixelization	O
to	O
reduce	O
the	O
screen-door	B-General_Concept
effect	I-General_Concept
.	O
</s>
<s>
At	O
about	O
the	O
same	O
time	O
,	O
the	O
German	O
company	O
"	O
Bonner	O
Ingenieurbüro	O
für	O
Optoelektronik	O
CrystalVision	O
"	O
started	O
experimenting	O
with	O
LCD	B-Device
projection	O
devices	O
from	O
1985	O
onwards	O
.	O
</s>
<s>
Although	O
traditional	O
slide	B-Device
projectors	I-Device
already	O
used	O
infrared	O
filters	O
to	O
reduce	O
heating	O
of	O
the	O
photographic	O
slides	O
,	O
LCDs	B-Device
are	O
much	O
more	O
sensitive	O
to	O
overheating	O
.	O
</s>
<s>
When	O
the	O
temperature	O
in	O
the	O
nematic	O
liquid	B-Device
crystal	I-Device
layer	O
reaches	O
the	O
"	O
clearing	O
point	O
"	O
(	O
i.e.	O
</s>
<s>
Without	O
applying	O
this	O
invention	O
,	O
LCD	B-Device
projectors	I-Device
with	O
a	O
powerful	O
light	O
source	O
do	O
n't	O
work	O
.	O
</s>
<s>
A	O
commercial	O
LCD	B-Device
projector	I-Device
based	O
on	O
this	O
principle	O
was	O
launched	O
in	O
Germany	O
in	O
1990	O
under	O
the	O
trade	O
name	O
"	O
Imagina	O
90	O
"	O
.	O
</s>
<s>
With	O
patents	O
filed	O
worldwide	O
(	O
filing	O
his	O
first	O
LCD	B-Device
video	B-Device
projector	I-Device
patent	O
application	O
in	O
1987	O
)	O
,	O
Dolgoff	O
started	O
Projectavision	O
,	O
Inc	O
.	O
in	O
1988	O
,	O
as	O
one	O
of	O
the	O
world	O
's	O
first	O
dedicated	O
LCD-projector	O
companies	O
,	O
which	O
he	O
took	O
public	O
on	O
Nasdaq	O
in	O
1990	O
.	O
</s>
<s>
He	O
licensed	O
the	O
technology	O
to	O
other	O
companies	O
including	O
Panasonic	O
and	O
Samsung	B-Application
.	O
</s>
<s>
Early	O
pioneers	O
of	O
LCD	B-Device
projection	O
in	O
Japan	O
were	O
Epson	O
and	O
Sharp	O
,	O
which	O
launched	O
their	O
own	O
color	O
video	B-Device
projector	I-Device
products	O
in	O
1989	O
.	O
</s>
<s>
In	O
1989	O
,	O
Projectavision	O
,	O
Inc	O
.	O
was	O
awarded	O
the	O
first	O
Defense	O
Advanced	O
Research	O
Projects	O
Agency	O
(	O
DARPA	O
)	O
contractfor	O
US$1	O
millionfor	O
proposing	O
that	O
the	O
United	O
States	O
high-definition	B-Device
television	I-Device
(	O
HDTV	B-Device
)	O
standard	O
should	O
use	O
digital	O
processing	O
and	O
projection	O
.	O
</s>
<s>
Since	O
2005	O
,	O
the	O
only	O
remaining	O
manufacturers	O
of	O
the	O
LCDs	B-Device
for	O
LCD	B-Device
projectors	I-Device
are	O
Japanese	O
imaging	O
companies	O
Epson	O
and	O
Sony	O
.	O
</s>
<s>
Epson	O
owns	O
the	O
technology	O
and	O
has	O
branded	O
it	O
as	O
"	O
3LCD	B-General_Concept
"	O
.	O
</s>
<s>
To	O
market	O
3LCD	B-General_Concept
projector	O
technology	O
,	O
Epson	O
also	O
set	O
up	O
a	O
consortium	O
called	O
the	O
"	O
3LCD	B-General_Concept
Group	O
"	O
in	O
2005	O
with	O
other	O
projector	O
manufacturer	O
licensees	O
of	O
3LCD	B-General_Concept
technology	O
that	O
use	O
it	O
in	O
their	O
projector	O
models	O
.	O
</s>
<s>
Early	O
LCD	B-Device
systems	O
were	O
used	O
with	O
existing	O
overhead	B-Device
projectors	I-Device
.	O
</s>
<s>
The	O
LCD	B-Device
system	O
did	O
not	O
have	O
a	O
light	O
source	O
of	O
its	O
own	O
:	O
it	O
was	O
built	O
on	O
a	O
large	O
"	O
plate	O
"	O
that	O
sat	O
on	O
top	O
of	O
the	O
projector	O
in	O
place	O
of	O
transparencies	O
.	O
</s>
<s>
This	O
provided	O
a	O
stop-gap	O
solution	O
in	O
the	O
era	O
when	O
the	O
computer	O
was	O
not	O
yet	O
a	O
universal	O
display	O
medium	O
,	O
creating	O
a	O
market	O
for	O
LCD	B-Device
projectors	I-Device
before	O
their	O
current	O
main	O
use	O
became	O
popular	O
.	O
</s>
<s>
In	O
2004	O
and	O
2005	O
,	O
LCD	B-Device
front	O
projection	O
began	O
a	O
comeback	O
with	O
the	O
introduction	O
of	O
the	O
dynamic	O
iris	O
and	O
other	O
modifications	O
that	O
have	O
improved	O
perceived	O
contrast	O
to	O
levels	O
similar	O
to	O
DLP	O
.	O
</s>
<s>
The	O
basic	O
design	O
of	O
an	O
LCD	B-Device
projector	I-Device
is	O
frequently	O
used	O
by	O
hobbyists	O
who	O
build	O
their	O
own	O
DIY	O
(	O
do-it-yourself	O
)	O
projection	O
systems	O
.	O
</s>
<s>
The	O
basic	O
technique	O
is	O
to	O
combine	O
a	O
high	O
color-rendering	O
index	O
(	O
CRI	O
)	O
high-intensity	O
discharge	O
lamp	O
(	O
HID	O
lamp	O
)	O
and	O
ballast	O
with	O
a	O
condenser	O
and	O
collector	O
Fresnel	O
lens	O
,	O
an	O
LCD	B-Device
removed	O
from	O
a	O
common	O
computer	O
display	O
and	O
a	O
triplet	O
lens	O
.	O
</s>
