<s>
A	O
vectograph	B-Algorithm
is	O
a	O
type	O
of	O
stereoscopic	B-Algorithm
print	O
or	O
transparency	O
viewed	O
by	O
using	O
the	O
polarized	B-Algorithm
3D	I-Algorithm
glasses	I-Algorithm
most	O
commonly	O
associated	O
with	O
projected	O
3D	O
motion	O
pictures	O
.	O
</s>
<s>
Credit	O
for	O
the	O
concept	O
of	O
the	O
vectograph	B-Algorithm
is	O
due	O
to	O
Joseph	O
Mahler	O
,	O
cousin	O
of	O
composer	O
and	O
conductor	O
Gustav	O
Mahler	O
.	O
</s>
<s>
An	O
elementary	O
vectograph	B-Algorithm
is	O
a	O
polarizing	O
filter	O
sheet	O
that	O
encodes	O
a	O
photographic	O
image	O
as	O
areas	O
that	O
polarize	O
light	O
more	O
or	O
less	O
strongly	O
,	O
corresponding	O
to	O
the	O
darker	O
and	O
lighter	O
areas	O
of	O
the	O
image	O
.	O
</s>
<s>
If	O
two	O
such	O
images	O
,	O
made	O
to	O
polarize	O
in	O
opposite	O
directions	O
and	O
each	O
encoding	O
one	O
of	O
the	O
images	O
of	O
a	O
stereoscopic	B-Algorithm
pair	O
,	O
are	O
superimposed	O
and	O
viewed	O
through	O
glasses	O
containing	O
appropriately	O
oriented	O
polarizing	O
filters	O
,	O
each	O
eye	O
sees	O
only	O
one	O
of	O
the	O
images	O
and	O
a	O
single	O
three-dimensional	O
image	O
is	O
perceived	O
by	O
people	O
with	O
normal	O
stereoscopic	B-Algorithm
vision	O
.	O
</s>
<s>
Vectographs	B-Algorithm
in	O
their	O
native	O
form	O
are	O
transparencies	O
,	O
to	O
be	O
viewed	O
by	O
transmitted	O
light	O
or	O
projected	O
onto	O
a	O
suitable	O
non-depolarizing	O
screen	O
,	O
but	O
by	O
limiting	O
the	O
density	O
of	O
the	O
images	O
and	O
backing	O
the	O
vectograph	B-Algorithm
with	O
a	O
non-depolarizing	O
aluminum-based	O
paint	O
,	O
a	O
print	O
for	O
viewing	O
by	O
reflected	O
light	O
can	O
be	O
produced	O
.	O
</s>
<s>
Vectographic	O
prints	O
and	O
transparencies	O
can	O
serve	O
many	O
of	O
the	O
same	O
purposes	O
as	O
their	O
anaglyph	B-Algorithm
equivalents	O
,	O
but	O
with	O
the	O
visual	O
advantage	O
that	O
they	O
do	O
not	O
require	O
the	O
use	O
of	O
viewing	O
filters	O
which	O
are	O
of	O
disturbingly	O
different	O
colors	O
for	O
each	O
eye	O
.	O
</s>
<s>
However	O
,	O
while	O
anaglyph	B-Algorithm
images	I-Algorithm
can	O
be	O
produced	O
by	O
virtually	O
any	O
photographic	O
or	O
mechanical	O
printing	O
process	O
capable	O
of	O
producing	O
a	O
two-colored	O
image	O
,	O
vectographic	O
images	O
require	O
specialized	O
materials	O
and	O
printing	O
technologies	O
,	O
limiting	O
their	O
practical	O
application	O
.	O
</s>
<s>
During	O
World	O
War	O
II	O
,	O
stereoscopic	B-Algorithm
aerial	O
reconnaissance	O
photographs	O
were	O
printed	O
in	O
the	O
form	O
of	O
vectographs	B-Algorithm
,	O
both	O
as	O
reflective	O
prints	O
for	O
use	O
by	O
troops	O
in	O
the	O
field	O
and	O
as	O
transparencies	O
to	O
be	O
projected	O
onto	O
a	O
screen	O
for	O
group	O
viewing	O
and	O
discussion	O
.	O
</s>
<s>
Instructional	O
use	O
was	O
made	O
of	O
projected	O
vectograph	B-Algorithm
slides	O
illustrating	O
three-dimensional	O
coordinate	O
systems	O
.	O
</s>
<s>
Although	O
originally	O
a	O
monochrome	O
"	O
black-and-white	O
"	O
process	O
only	O
,	O
experimental	O
full-color	O
vectographs	B-Algorithm
were	O
soon	O
being	O
made	O
by	O
Polaroid	O
.	O
</s>
<s>
Color	O
vectograph	B-Algorithm
printing	O
service	O
for	O
digital	O
image	O
files	O
was	O
offered	O
to	O
the	O
public	O
,	O
but	O
it	O
was	O
expensive	O
and	O
little-used	O
.	O
</s>
<s>
The	O
most	O
common	O
vectographs	B-Algorithm
,	O
if	O
any	O
examples	O
of	O
the	O
process	O
may	O
be	O
called	O
common	O
,	O
are	O
those	O
in	O
the	O
booklets	O
of	O
"	O
Ortho-Fusor	O
"	O
stereoscopic	B-Algorithm
eye	O
exercises	O
first	O
issued	O
by	O
Bausch	O
and	O
Lomb	O
in	O
the	O
1940s	O
and	O
available	O
for	O
many	O
years	O
.	O
</s>
<s>
Also	O
relatively	O
common	O
is	O
the	O
Titmus	O
Fly	O
Stereotest	O
,	O
a	O
greatly	O
enlarged	O
stereoscopic	B-Algorithm
image	I-Algorithm
of	O
a	O
fly	O
used	O
by	O
optometrists	O
and	O
ophthalmologists	O
to	O
determine	O
if	O
patients	O
,	O
especially	O
young	O
children	O
,	O
have	O
normal	O
stereoscopic	B-Algorithm
vision	O
.	O
</s>
<s>
Currently	O
available	O
vectographic	O
vision	O
training	O
aids	O
,	O
marketed	O
under	O
the	O
registered	O
trademark	O
name	O
"	O
Vectogram	B-Algorithm
"	O
,	O
include	O
a	O
variety	O
with	O
the	O
left-eye	O
and	O
right-eye	O
images	O
overlaid	O
on	O
separate	O
transparent	O
plastic	O
sheets	O
so	O
as	O
to	O
be	O
adjustable	O
.	O
</s>
