<s>
A	O
slide	B-Device
projector	I-Device
is	O
an	O
opto-mechanical	O
device	B-Application
for	O
showing	O
photographic	O
slides	O
.	O
</s>
<s>
35	O
mm	O
slide	B-Device
projectors	I-Device
,	O
direct	O
descendants	O
of	O
the	O
larger-format	O
magic	B-Device
lantern	I-Device
,	O
first	O
came	O
into	O
widespread	O
use	O
during	O
the	O
1950s	O
as	O
a	O
form	O
of	O
occasional	O
home	O
entertainment	O
;	O
family	O
members	O
and	O
friends	O
would	O
gather	O
to	O
view	O
slide	O
shows	O
.	O
</s>
<s>
Slide	B-Device
projectors	I-Device
were	O
also	O
widely	O
used	O
in	O
educational	O
and	O
other	O
institutional	O
settings	O
.	O
</s>
<s>
Photographic	O
film	B-Device
slides	I-Device
and	O
projectors	B-Application
have	O
mostly	O
been	O
replaced	O
by	O
image	O
files	O
on	O
digital	O
storage	O
media	O
shown	O
on	O
a	O
projection	O
screen	O
by	O
using	O
a	O
video	B-Device
projector	I-Device
or	O
simply	O
displayed	O
on	O
a	O
large-screen	O
video	O
monitor	B-Device
.	O
</s>
<s>
A	O
projector	B-Application
has	O
four	O
main	O
elements	O
:	O
</s>
<s>
This	O
form	O
of	O
projection	O
also	O
avoids	O
the	O
audience	O
interrupting	O
the	O
light	O
stream	O
by	O
casting	O
their	O
shadows	O
on	O
the	O
projection	O
or	O
by	O
bumping	O
into	O
the	O
projector	B-Application
.	O
</s>
<s>
Large-format	O
slide	B-Device
projectors	I-Device
for	O
use	O
on	O
stages	O
,	O
at	O
large	O
events	O
,	O
or	O
for	O
architectural	O
and	O
advertising	O
installations	O
where	O
high	O
light	O
output	O
is	O
needed	O
.	O
</s>
<s>
List	O
of	O
known	O
manufacturers	O
of	O
slide	B-Device
projectors	I-Device
:	O
</s>
