<s>
A	O
CRT	B-General_Concept
projector	I-General_Concept
is	O
a	O
video	B-Device
projector	I-Device
that	O
uses	O
a	O
small	O
,	O
high-brightness	O
cathode	B-Device
ray	I-Device
tube	I-Device
(	O
CRT	O
)	O
as	O
the	O
image	O
generating	O
element	O
.	O
</s>
<s>
The	O
first	O
color	O
CRT	B-General_Concept
projectors	I-General_Concept
came	O
out	O
in	O
the	O
early	O
1950s	O
.	O
</s>
<s>
Most	O
modern	O
CRT	B-General_Concept
projectors	I-General_Concept
are	O
color	O
and	O
have	O
three	O
separate	O
CRTs	O
(	O
instead	O
of	O
a	O
single	O
,	O
color	O
CRT	O
)	O
,	O
and	O
their	O
own	O
lenses	O
to	O
achieve	O
color	O
images	O
.	O
</s>
<s>
Various	O
designs	O
have	O
made	O
it	O
to	O
production	O
,	O
including	O
the	O
"	O
direct	O
"	O
CRT-lens	O
design	O
,	O
and	O
the	O
Schmidt	O
CRT	O
,	O
which	O
employed	O
a	O
phosphor	O
screen	O
that	O
illuminates	O
a	O
perforated	O
spherical	O
mirror	O
,	O
all	O
within	O
an	O
evacuated	O
cathode	B-Device
ray	I-Device
tube	I-Device
.	O
</s>
<s>
Though	O
systems	O
utilizing	O
projected	O
video	O
at	O
one	O
time	O
almost	O
exclusively	O
used	O
CRT	B-General_Concept
projectors	I-General_Concept
,	O
they	O
have	O
largely	O
been	O
replaced	O
by	O
other	O
technologies	O
such	O
as	O
LCD	B-Device
projection	I-Device
and	O
Digital	B-General_Concept
Light	I-General_Concept
Processing	I-General_Concept
.	O
</s>
<s>
Improvements	O
in	O
these	O
digital	B-Device
video	I-Device
projectors	I-Device
,	O
and	O
their	O
subsequent	O
increased	O
availability	O
and	O
desirability	O
,	O
resulted	O
in	O
a	O
drastic	O
decline	O
of	O
CRT	B-General_Concept
projector	I-General_Concept
sales	O
by	O
the	O
year	O
2009	O
.	O
,	O
very	O
few	O
(	O
if	O
any	O
)	O
new	O
units	O
are	O
manufactured	O
,	O
though	O
a	O
number	O
of	O
installers	O
do	O
sell	O
refurbished	O
units	O
,	O
generally	O
higher-end	O
8	O
"	O
and	O
9	O
"	O
models	O
.	O
</s>
<s>
Some	O
of	O
the	O
first	O
CRT	O
projection	O
tubes	O
were	O
made	O
in	O
1933	O
,	O
and	O
by	O
1938	O
CRT	B-General_Concept
projectors	I-General_Concept
were	O
already	O
in	O
use	O
in	O
theaters	O
.	O
</s>
<s>
High-end	O
CRT	B-General_Concept
projectors	I-General_Concept
can	O
precisely	O
display	O
images	O
up	O
to	O
1920	O
x	O
1200	O
.	O
</s>
<s>
Because	O
of	O
the	O
good	O
black	O
levels	O
,	O
CRT	B-General_Concept
projectors	I-General_Concept
are	O
good	O
contenders	O
to	O
be	O
used	O
in	O
edge-blend	O
setups	O
.	O
</s>
<s>
DLP	B-General_Concept
and	O
LCD	B-Device
projector	I-Device
edge	O
blend	O
setups	O
show	O
a	O
visible	O
gray	O
seam	O
in	O
the	O
middle	O
in	O
dark	O
scenes	O
.	O
</s>
<s>
Because	O
of	O
their	O
4:3	O
picture	B-Device
tubes	I-Device
,	O
edge-blended	O
CRTs	O
use	O
a	O
larger	O
surface	O
area	O
of	O
the	O
tubes	O
when	O
showing	O
video	O
in	O
a	O
cinemascope	O
aspect	O
ratio	O
,	O
which	O
reduces	O
uneven	O
wear	O
and	O
yields	O
higher	O
total	O
brightness	O
.	O
</s>
<s>
CRT	B-General_Concept
projector	I-General_Concept
stacking	O
is	O
also	O
possible	O
.	O
</s>
<s>
As	O
with	O
CRT	B-Device
monitors	I-Device
,	O
the	O
image	O
resolution	O
and	O
the	O
refresh	O
rate	O
are	O
not	O
fixed	O
but	O
variable	O
within	O
some	O
limits	O
.	O
</s>
<s>
Many	O
CRT	B-General_Concept
projectors	I-General_Concept
are	O
multiscan-capable	O
,	O
with	O
a	O
horizontal	O
frequency	O
range	O
starting	O
at	O
15KHz	O
in	O
the	O
bottom	O
end	O
,	O
on	O
some	O
projectors	O
going	O
all	O
the	O
way	O
up	O
to	O
150	O
or	O
180KHz	O
.	O
</s>
<s>
This	O
means	O
that	O
CRT	B-General_Concept
projectors	I-General_Concept
are	O
resolution	O
compatible	O
with	O
a	O
lot	O
of	O
video	O
sources	O
,	O
including	O
standard-definition	B-Device
TV	I-Device
and	O
retro	O
games	O
(	O
15.7KHz	O
)	O
,	O
VCRs	O
,	O
arcade	O
games	O
(	O
15.7	O
,	O
24	O
and	O
31KHz	O
)	O
,	O
older	O
VGA	O
computers	O
(	O
31KHz	O
)	O
,	O
modern	O
computers	O
(	O
typically	O
48KHz	O
for	O
768p60	O
,	O
68KHz	O
for	O
768p85	O
,	O
67KHz	O
for	O
1080p60	O
or	O
137KHz	O
for	O
4k60	B-Architecture
)	O
,	O
HDTV	B-Device
(	O
45KHz	O
for	O
720p60	O
,	O
28KHz	O
for	O
1080i50	O
,	O
67KHz	O
for	O
1080p60	O
)	O
,	O
modern	O
video	O
game	O
consoles	O
,	O
and	O
more	O
,	O
without	O
the	O
need	O
for	O
upscaling	B-Algorithm
or	O
downscaling	B-Application
.	O
</s>
<s>
This	O
is	O
advantageous	O
over	O
for	O
example	O
CRT	O
computer	B-Device
monitors	I-Device
,	O
of	O
which	O
all	O
the	O
ones	O
from	O
the	O
mid-90s	O
or	O
later	O
are	O
also	O
multisync	O
capable	O
,	O
but	O
have	O
a	O
lower	O
frequency	O
limit	O
of	O
30KHz	O
,	O
making	O
480p60	O
or	O
240p120	O
the	O
lowest	O
resolution	O
possible	O
,	O
thus	O
needing	O
upscaling	B-Algorithm
to	O
work	O
with	O
retro	O
games	O
and	O
arcade	O
games	O
.	O
</s>
<s>
CRT	B-General_Concept
projectors	I-General_Concept
do	O
not	O
show	O
a	O
rainbow	O
effect	O
seen	O
with	O
single	O
chip	O
DLP	B-General_Concept
projectors	I-General_Concept
.	O
</s>
<s>
Some	O
CRT	B-General_Concept
projectors	I-General_Concept
,	O
like	O
the	O
Dwin	O
500	O
and	O
700	O
,	O
include	O
no	O
fans	O
and	O
are	O
much	O
quieter	O
than	O
comparable	O
LCD	B-Device
or	O
DLP	B-General_Concept
projectors	I-General_Concept
.	O
</s>
<s>
Many	O
CRT	B-General_Concept
projectors	I-General_Concept
feature	O
large-size	O
fans	O
and	O
temperature	O
control	O
and	O
some	O
can	O
be	O
easily	O
modified	O
for	O
quieter	O
and/or	O
better	O
performing	O
cooling	O
.	O
</s>
<s>
The	O
components	O
in	O
CRT	B-General_Concept
projectors	I-General_Concept
feature	O
large	O
surface	O
areas	O
compared	O
to	O
compact	O
,	O
bright	O
Xenon-bulb	O
lit	O
DLP	B-General_Concept
or	O
LCD	B-Device
projectors	I-Device
.	O
</s>
<s>
CRT	B-General_Concept
projectors	I-General_Concept
are	O
both	O
considerably	O
larger	O
and	O
heavier	O
than	O
comparable	O
LCD	B-Device
and	O
DLP	B-General_Concept
projectors	I-General_Concept
.	O
</s>
<s>
CRT	B-General_Concept
projectors	I-General_Concept
require	O
far	O
more	O
time	O
to	O
set	O
up	O
and	O
adjust	O
than	O
LCD	B-Device
and	O
DLP	B-General_Concept
based	O
projectors	O
.	O
</s>
<s>
Absolute	O
ANSI	O
brightness	O
achievable	O
with	O
CRT	B-General_Concept
projectors	I-General_Concept
is	O
lower	O
than	O
with	O
comparable	O
lamp	O
or	O
laser	O
illuminated	O
LCD	B-Device
,	O
LcOS	O
and	O
DLP	B-General_Concept
projectors	I-General_Concept
.	O
</s>
<s>
As	O
an	O
example	O
,	O
the	O
brightest	O
CRT	B-General_Concept
projectors	I-General_Concept
for	O
home	O
use	O
were	O
capable	O
of	O
1,500	O
ANSI	O
lumens	O
.	O
</s>
<s>
While	O
maximum	O
achievable	O
brightness	O
is	O
lower	O
on	O
a	O
CRT	B-General_Concept
projector	I-General_Concept
,	O
a	O
CRT	O
's	O
contrast	O
ratio	O
makes	O
it	O
easier	O
to	O
adjust	O
contrast/brightness	O
settings	O
without	O
getting	O
a	O
washed	O
out	O
picture	O
from	O
a	O
lamp	O
that	O
is	O
unnecessarily	O
powerful	O
.	O
</s>
<s>
Low-end	O
or	O
poorly	O
tuned	O
CRT	B-General_Concept
projectors	I-General_Concept
may	O
suffer	O
from	O
color	O
divergence	O
or	O
geometric	O
distortion	O
(	O
for	O
example	O
,	O
straight	O
lines	O
may	O
not	O
always	O
appear	O
completely	O
straight	O
,	O
especially	O
near	O
the	O
corners	O
)	O
.	O
</s>
<s>
However	O
,	O
CRT	B-General_Concept
projectors	I-General_Concept
offer	O
more	O
options	O
for	O
adjusting	O
and	O
counteracting	O
geometrical	O
inaccuracies	O
.	O
</s>
<s>
Because	O
CRT	B-General_Concept
projectors	I-General_Concept
use	O
monochrome	O
tubes	O
,	O
geometry	O
adjustments	O
do	O
not	O
have	O
to	O
line	O
up	O
with	O
a	O
raster	O
on	O
the	O
tube	O
faces	O
,	O
as	O
the	O
raster	O
is	O
generated	O
by	O
the	O
electron	O
beam	O
itself	O
.	O
</s>
<s>
Software-based	O
geometry	O
adjustments	O
in	O
digital	B-Device
projectors	I-Device
do	O
not	O
only	O
create	O
an	O
unsharp	O
and	O
scaled	O
picture	O
,	O
it	O
also	O
forces	O
the	O
picture	O
to	O
be	O
electronically	O
buffered	O
and	O
processed	O
,	O
which	O
adds	O
input	B-Application
lag	I-Application
.	O
</s>
<s>
CRT	B-General_Concept
projectors	I-General_Concept
use	O
more	O
power/cost	O
more	O
to	O
run	O
than	O
LCD	B-Device
and	O
DLP	B-General_Concept
units	O
.	O
</s>
<s>
Unlike	O
LCD	B-Device
or	O
DLP	B-General_Concept
projectors	I-General_Concept
,	O
CRT	B-General_Concept
projectors	I-General_Concept
are	O
more	O
prone	O
to	O
burn-in	B-General_Concept
,	O
if	O
set	O
to	O
relatively	O
a	O
high	O
contrast	O
value	O
and/or	O
displaying	O
static	O
content	O
for	O
extended	O
periods	O
of	O
time	O
.	O
</s>
<s>
Overall	O
burn-in	B-General_Concept
is	O
also	O
a	O
problem	O
when	O
moving	O
or	O
buying/selling	O
CRT	B-General_Concept
projectors	I-General_Concept
,	O
as	O
different	O
locations	O
and	O
different	O
setups	O
end	O
up	O
using	O
different	O
portions	O
of	O
the	O
surface	O
of	O
the	O
picture	B-Device
tubes	I-Device
.	O
</s>
