<s>
Specular	B-Algorithm
holography	I-Algorithm
is	O
a	O
technique	O
for	O
making	O
three	O
dimensional	O
imagery	O
by	O
controlling	O
the	O
motion	O
of	O
specular	O
glints	O
on	O
a	O
two-dimensional	O
surface	O
.	O
</s>
<s>
The	O
image	O
is	O
made	O
of	O
many	O
specularities	O
and	O
has	O
the	O
appearance	O
of	O
a	O
3D	B-Algorithm
surface-stippling	O
made	O
of	O
dots	O
of	O
light	O
.	O
</s>
<s>
Unlike	O
conventional	O
wavefront	O
holograms	B-Algorithm
,	O
specular	O
holograms	B-Algorithm
do	O
not	O
depend	O
on	O
wave	O
optics	O
,	O
photographic	O
media	O
,	O
or	O
lasers	O
.	O
</s>
<s>
If	O
that	O
motion	O
is	O
projectively	O
consistent	O
with	O
binocular	O
disparity	O
,	O
the	O
viewer	O
will	O
perceive	O
—	O
via	O
stereopsis	B-Algorithm
—	O
the	O
illusion	O
that	O
the	O
glint	O
occurs	O
at	O
a	O
different	O
depth	O
than	O
the	O
surface	O
that	O
produces	O
it	O
.	O
</s>
<s>
Aspecular	O
hologram	B-Algorithm
contains	O
many	O
such	O
curved	O
surfaces	O
,	O
all	O
embedded	O
in	O
a	O
host	O
surface	O
.	O
</s>
<s>
Each	O
produces	O
a	O
glint	O
and	O
the	O
brain	O
integrates	O
the	O
many	O
3D	B-Algorithm
cues	O
to	O
perceive	O
a	O
3D	B-Algorithm
shape	O
.	O
</s>
<s>
Specular	B-Algorithm
holography	I-Algorithm
dates	O
back	O
to	O
Hans	O
Weil	O
's	O
attempts	O
in	O
the	O
1930s	O
and	O
thus	O
has	O
a	O
longer	O
history	O
than	O
conventional	O
wavefront	O
holography	B-Algorithm
.	O
</s>
<s>
Hans	O
Weil	O
filed	O
a	O
1934	O
United	O
Kingdom	O
patent	O
for	O
a	O
specular	B-Algorithm
holography	I-Algorithm
technique	O
.	O
</s>
<s>
Weil	O
appreciated	O
that	O
this	O
might	O
be	O
used	O
to	O
produce	O
3D	B-Algorithm
imagery	O
,	O
but	O
it	O
is	O
not	O
clear	O
whether	O
he	O
knew	O
how	O
to	O
do	O
so	O
,	O
especially	O
considering	O
that	O
modern	O
techniques	O
are	O
heavily	O
computational	O
.	O
</s>
<s>
The	O
patent	O
itself	O
is	O
limited	O
to	O
straight	O
reflecting	O
surfaces	O
,	O
which	O
are	O
not	O
sufficient	O
to	O
produce	O
3D	B-Algorithm
images	I-Algorithm
.	O
</s>
<s>
His	O
1980	O
artwork	O
World	O
Brain	O
is	O
made	O
of	O
CNC-machined	O
semi-circular	O
arcs	O
that	O
produce	O
a	O
holographic	B-Algorithm
effect	O
.	O
</s>
<s>
The	O
phenomenon	O
was	O
independently	O
discovered	O
in	O
the	O
1990s	O
by	O
William	O
Beaty	O
who	O
popularized	O
a	O
method	O
of	O
making	O
hand-drawn	O
holograms	B-Algorithm
using	O
a	O
compass	O
(	O
drafting	O
)	O
.	O
</s>
<s>
This	O
has	O
come	O
to	O
be	O
known	O
as	O
scratch	O
holography	B-Algorithm
.	O
</s>
<s>
Beaty	O
established	O
a	O
connection	O
between	O
scratch	O
holography	B-Algorithm
and	O
conventional	O
wavefront	O
holography	B-Algorithm
by	O
pointing	O
out	O
that	O
a	O
circular	O
arc	O
approximates	O
a	O
scaled-up	O
Benton	O
rainbow	O
hologram	B-Algorithm
of	O
a	O
single	O
point	O
.	O
</s>
<s>
This	O
explains	O
why	O
scratch	O
hologram	B-Algorithm
images	O
are	O
subject	O
to	O
distracting	O
distortions	O
and	O
collapse	O
of	O
the	O
depth	O
image	O
outside	O
of	O
a	O
very	O
narrow	O
field	O
of	O
view	O
---	O
circular	O
arcs	O
are	O
a	O
fairly	O
poor	O
approximation	O
to	O
rainbow	O
hologram	B-Algorithm
fringes	O
.	O
</s>
<s>
Beaty	O
also	O
pointed	O
out	O
that	O
the	O
rainbow	O
hologram	B-Algorithm
of	O
a	O
single	O
point	O
is	O
a	O
rectangular	O
section	O
of	O
nested	O
parabolics	O
.	O
</s>
<s>
If	O
one	O
were	O
to	O
view	O
that	O
geometry	O
as	O
a	O
3D	B-Algorithm
reflective	O
surface	O
under	O
collimated	O
light	O
,	O
one	O
would	O
observe	O
glint	O
motion	O
that	O
is	O
consistent	O
with	O
horizontal	O
parallax	O
.	O
</s>
<s>
On	O
cookers	O
with	O
fine	O
Fresnel	O
patterns	O
,	O
the	O
holographic	B-Algorithm
image	I-Algorithm
of	O
a	O
depth-varying	O
bar	O
of	O
light	O
is	O
readily	O
apparent	O
.	O
</s>
<s>
In	O
2008	O
,	O
Brand	O
demonstrated	O
a	O
distortion-free	O
form	O
of	O
specular	B-Algorithm
holography	I-Algorithm
.	O
</s>
<s>
Brand	O
's	O
method	O
considers	O
the	O
bundle	O
of	O
light	O
rays	O
that	O
must	O
be	O
delivered	O
to	O
the	O
viewer	O
as	O
the	O
viewer	O
,	O
light	O
source	O
,	O
hologram	B-Algorithm
,	O
and	O
holographic	B-Algorithm
image	I-Algorithm
move	O
relative	O
to	O
each	O
other	O
.	O
</s>
<s>
The	O
equations	O
specify	O
a	O
foliation	O
of	O
possible	O
optical	O
surfaces	O
;	O
the	O
hologram	B-Algorithm
is	O
an	O
intersection	O
of	O
this	O
foliation	O
and	O
a	O
thin	O
shell	O
that	O
conforms	O
to	O
the	O
host	O
surface	O
.	O
</s>
<s>
Solar	O
cookers	O
represent	O
one	O
such	O
foliation	O
;	O
scratch	O
holograms	B-Algorithm
do	O
not	O
,	O
hence	O
their	O
distortion	O
.	O
</s>
<s>
One	O
interesting	O
property	O
of	O
the	O
foliation	O
approach	O
is	O
that	O
it	O
yields	O
solutions	O
for	O
non-flat	O
holographic	B-Algorithm
surfaces	O
and	O
for	O
unconventional	O
viewing	O
geometries	O
.	O
</s>
<s>
Brand	O
has	O
exhibited	O
holograms	B-Algorithm
with	O
3D	B-Algorithm
scenes	O
,	O
animation	O
,	O
and	O
ultra-wide	O
field	O
of	O
view	O
.	O
</s>
