<s>
The	O
screen-door	B-General_Concept
effect	I-General_Concept
(	O
SDE	O
)	O
is	O
a	O
visual	B-Algorithm
artifact	I-Algorithm
of	O
displays	O
,	O
where	O
the	O
fine	O
lines	O
separating	O
pixels	B-Algorithm
(	O
or	O
subpixels	O
)	O
become	O
visible	O
in	O
the	O
displayed	O
image	O
.	O
</s>
<s>
This	O
can	O
be	O
seen	O
in	O
digital	B-Device
projector	I-Device
images	O
and	O
regular	O
displays	O
under	O
magnification	O
or	O
at	O
close	O
range	O
,	O
but	O
the	O
increases	O
in	O
display	O
resolutions	O
have	O
made	O
this	O
much	O
less	O
significant	O
.	O
</s>
<s>
More	O
recently	O
,	O
the	O
screen	B-General_Concept
door	I-General_Concept
effect	I-General_Concept
has	O
been	O
an	O
issue	O
with	O
virtual	B-Device
reality	I-Device
headsets	I-Device
and	O
other	O
head-mounted	B-General_Concept
displays	I-General_Concept
,	O
because	O
these	O
are	O
viewed	O
at	O
a	O
much	O
closer	O
distance	O
,	O
and	O
stretch	O
a	O
single	O
display	O
across	O
a	O
much	O
wider	O
field	O
of	O
view	O
.	O
</s>
<s>
In	O
LCD	O
and	O
DLP	B-General_Concept
projectors	I-General_Concept
,	O
SDE	O
can	O
be	O
seen	O
because	O
projector	O
optics	O
typically	O
have	O
significantly	O
lower	O
pixel	B-Algorithm
density	I-Algorithm
than	O
the	O
size	O
of	O
the	O
image	O
they	O
project	O
,	O
enlarging	O
these	O
fine	O
lines	O
,	O
which	O
are	O
much	O
smaller	O
than	O
the	O
pixels	B-Algorithm
themselves	O
,	O
to	O
be	O
seen	O
.	O
</s>
<s>
The	O
screen	B-General_Concept
door	I-General_Concept
effect	I-General_Concept
was	O
noticed	O
on	O
the	O
first	O
digital	B-Device
projector	I-Device
:	O
an	O
LCD	O
projector	O
made	O
in	O
1984	O
by	O
Gene	O
Dolgoff	O
.	O
</s>
<s>
To	O
eliminate	O
this	O
artifact	B-Algorithm
,	O
Dolgoff	O
invented	O
depixelization	O
,	O
which	O
used	O
various	O
optical	O
methods	O
to	O
eliminate	O
the	O
visibility	O
of	O
the	O
spaces	O
between	O
the	O
pixels	B-Algorithm
.	O
</s>
<s>
The	O
dominant	O
method	O
made	O
use	O
of	O
a	O
microlens	O
array	O
,	O
wherein	O
each	O
micro-lens	O
caused	O
a	O
slightly	O
magnified	O
image	O
of	O
the	O
pixel	B-Algorithm
behind	O
it	O
,	O
filling	O
in	O
the	O
previously-visible	O
spaces	O
between	O
pixels	B-Algorithm
.	O
</s>
<s>
In	O
addition	O
,	O
when	O
making	O
a	O
projector	O
with	O
a	O
single	O
,	O
full-color	O
LCD	O
panel	O
,	O
an	O
additional	O
appearance	O
of	O
pixelation	O
was	O
visible	O
due	O
to	O
the	O
noticeability	O
of	O
green	O
pixels	B-Algorithm
(	O
appearing	O
bright	O
)	O
adjacent	O
to	O
red	O
and	O
blue	O
pixels	B-Algorithm
(	O
appearing	O
dark	O
)	O
,	O
forming	O
a	O
noticeable	O
repeating	O
light	O
and	O
dark	O
pattern	O
.	O
</s>
<s>
Use	O
of	O
a	O
micro-lens	O
array	O
at	O
a	O
slightly	O
greater	O
distance	O
created	O
new	O
pixel	B-Algorithm
images	O
,	O
with	O
each	O
"	O
new	O
"	O
pixel	B-Algorithm
being	O
a	O
summation	O
of	O
six	O
neighboring	O
sub-pixels	O
(	O
made	O
up	O
of	O
two	O
full	O
color	O
pixels	B-Algorithm
,	O
one	O
above	O
the	O
other	O
)	O
.	O
</s>
<s>
Since	O
there	O
were	O
as	O
many	O
micro-lenses	O
as	O
there	O
were	O
original	O
pixels	B-Algorithm
,	O
no	O
resolution	O
was	O
lost	O
,	O
which	O
was	O
confirmed	O
with	O
modulation	O
transfer	O
function	O
(	O
MTF	O
)	O
measurements	O
.	O
</s>
<s>
The	O
screen	B-General_Concept
door	I-General_Concept
effect	I-General_Concept
on	O
Digital	B-General_Concept
Light	I-General_Concept
Processing	I-General_Concept
(	O
DLP	O
)	O
projectors	O
can	O
be	O
mitigated	O
by	O
deliberately	O
setting	O
the	O
projected	O
image	O
slightly	O
out	O
of	O
focus	O
,	O
which	O
blurs	O
the	O
boundaries	O
of	O
each	O
pixel	B-Algorithm
to	O
its	O
neighbor	O
.	O
</s>
<s>
This	O
minimizes	O
the	O
effect	O
by	O
filling	O
the	O
black	O
pixel	B-Algorithm
perimeters	O
with	O
adjacent	O
light	O
.	O
</s>
<s>
Some	O
older	O
LCD	O
projectors	O
have	O
a	O
more	O
noticeable	O
screen	B-General_Concept
door	I-General_Concept
effect	I-General_Concept
than	O
first	O
generation	O
DLP	B-General_Concept
projectors	I-General_Concept
.	O
</s>
<s>
Use	O
of	O
Dolgoff	O
's	O
depixelization	O
method	O
could	O
also	O
produce	O
a	O
DLP	B-General_Concept
projector	I-General_Concept
without	O
noticeable	O
pixelation	O
.	O
</s>
