<s>
Diffuse	B-Algorithm
reflectance	I-Algorithm
spectroscopy	I-Algorithm
,	O
or	O
diffuse	O
reflection	B-Algorithm
spectroscopy	I-Algorithm
,	O
is	O
a	O
subset	O
of	O
absorption	O
spectroscopy	O
.	O
</s>
<s>
It	O
is	O
sometimes	O
called	O
remission	B-Algorithm
spectroscopy	O
.	O
</s>
<s>
Remission	B-Algorithm
is	O
the	O
reflection	O
or	O
back-scattering	B-Algorithm
of	O
light	O
by	O
a	O
material	O
,	O
while	O
transmission	O
is	O
the	O
passage	O
of	O
light	O
through	O
a	O
material	O
.	O
</s>
<s>
The	O
word	O
remission	B-Algorithm
implies	O
a	O
direction	O
of	O
scatter	O
,	O
independent	O
of	O
the	O
scattering	O
process	O
.	O
</s>
<s>
Remission	B-Algorithm
includes	O
both	O
specular	O
and	O
diffusely	O
back-scattered	O
light	O
.	O
</s>
<s>
The	O
use	O
of	O
the	O
term	O
remission	B-Algorithm
spectroscopy	O
is	O
relatively	O
recent	O
,	O
and	O
found	O
first	O
use	O
in	O
applications	O
related	O
to	O
medicine	O
and	O
biochemistry	O
.	O
</s>
<s>
They	O
are	O
generally	O
those	O
consistent	O
with	O
a	O
two-flux	O
or	O
two-stream	B-Algorithm
approximation	I-Algorithm
.	O
</s>
<s>
Stokes	O
used	O
the	O
term	O
"	O
reflexion	O
"	O
,	O
not	O
"	O
remission	B-Algorithm
"	O
,	O
specifically	O
referring	O
to	O
what	O
is	O
often	O
called	O
regular	O
or	O
specular	O
reflection	O
.	O
</s>
<s>
His	O
mathematics	O
used	O
a	O
two	B-Algorithm
flux	I-Algorithm
approximation	I-Algorithm
;	O
i.e.	O
,	O
all	O
light	O
is	O
assumed	O
to	O
travel	O
with	O
a	O
component	O
either	O
in	O
the	O
same	O
direction	O
as	O
the	O
incident	O
beam	O
,	O
or	O
in	O
the	O
opposite	O
direction	O
.	O
</s>
<s>
In	O
1931	O
,	O
Paul	O
Kubelka	O
(	O
with	O
Franz	O
Munk	O
)	O
published	O
"	O
An	O
article	O
on	O
the	O
optics	O
of	O
paint	O
"	O
,	O
the	O
contents	O
of	O
which	O
has	O
come	O
to	O
be	O
known	O
as	O
the	O
Kubelka-Munk	B-Algorithm
theory	I-Algorithm
.	O
</s>
<s>
They	O
used	O
absorption	O
and	O
remission	B-Algorithm
(	O
or	O
back-scatter	B-Algorithm
)	O
constants	O
,	O
noting	O
(	O
as	O
translated	O
by	O
Stephen	O
H	O
.	O
Westin	O
)	O
that	O
"	O
an	O
infinitesimal	O
layer	O
of	O
the	O
coating	O
absorbs	O
and	O
scatters	O
a	O
certain	O
constant	O
portion	O
of	O
all	O
the	O
light	O
passing	O
through	O
it	O
"	O
.	O
</s>
<s>
While	O
symbols	O
and	O
terminology	O
are	O
changed	O
here	O
,	O
it	O
seems	O
clear	O
from	O
their	O
language	O
that	O
the	O
terms	O
in	O
their	O
differential	O
equations	O
stand	O
for	O
absorption	O
and	O
backscatter	B-Algorithm
(	O
remission	B-Algorithm
)	O
fractions	O
.	O
</s>
<s>
They	O
also	O
noted	O
that	O
the	O
reflectance	O
from	O
an	O
infinite	O
number	O
of	O
these	O
infinitesimal	O
layers	O
is	O
"	O
solely	O
a	O
function	O
of	O
the	O
ratio	O
of	O
the	O
absorption	O
and	O
back-scatter	B-Algorithm
(	O
remission	B-Algorithm
)	O
constants	O
,	O
but	O
not	O
in	O
any	O
way	O
on	O
the	O
absolute	O
numerical	O
values	O
of	O
these	O
constants	O
"	O
.	O
</s>
<s>
is	O
the	O
Back-Scattering	B-Algorithm
Coefficient	O
≡	O
the	O
limiting	O
fraction	O
of	O
light	O
energy	O
scattered	O
backwards	O
per	O
unit	O
thickness	O
as	O
thickness	O
tends	O
to	O
zero	O
.	O
</s>
<s>
The	O
Kubelka	O
–	O
Munk	O
equation	O
describes	O
the	O
remission	B-Algorithm
from	O
a	O
sample	O
composed	O
of	O
an	O
infinite	O
number	O
of	O
infinitesimal	O
layers	O
,	O
each	O
having	O
as	O
an	O
absorption	O
fraction	O
,	O
and	O
as	O
a	O
remission	B-Algorithm
fraction	O
.	O
</s>
<s>
This	O
led	O
to	O
a	O
very	O
early	O
(	O
perhaps	O
the	O
first	O
)	O
use	O
of	O
the	O
term	O
"	O
remission	B-Algorithm
"	O
in	O
place	O
of	O
"	O
reflectance	O
"	O
when	O
Judd	O
defined	O
a	O
"	O
remission	B-Algorithm
function	O
"	O
as	O
,	O
where	O
and	O
are	O
absorption	O
and	O
scattering	O
coefficients	O
,	O
which	O
replace	O
and	O
in	O
the	O
Kubelka	O
–	O
Munk	O
equation	O
above	O
.	O
</s>
<s>
Judd	O
tabulated	O
the	O
remission	B-Algorithm
function	O
as	O
a	O
function	O
of	O
percent	O
reflectance	O
from	O
an	O
infinitely	O
thick	O
sample	O
.	O
</s>
<s>
This	O
is	O
the	O
same	O
"	O
remission	B-Algorithm
function	O
"	O
as	O
used	O
by	O
Judd	O
,	O
but	O
Kortüm	O
's	O
translator	O
referred	O
to	O
it	O
as	O
"	O
the	O
so-called	O
reflectance	O
function	O
"	O
.	O
</s>
<s>
Additionally	O
,	O
Kortüm	O
derived	O
"	O
the	O
Kubelka-Munk	O
exponential	O
solution	O
"	O
by	O
defining	O
and	O
as	O
the	O
absorption	O
and	O
scattering	O
coefficient	O
per	O
centimeter	O
of	O
the	O
material	O
and	O
substituting	O
:	O
and	O
,	O
while	O
pointing	O
out	O
in	O
a	O
footnote	O
that	O
is	O
a	O
back-scattering	B-Algorithm
coefficient	O
.	O
</s>
<s>
In	O
1966	O
,	O
Harry	O
G	O
.	O
Hecht	O
(	O
with	O
Wesley	O
W	O
.	O
Wendlandt	O
)	O
published	O
a	O
book	O
entitled	O
"	O
Reflectance	O
Spectroscopy	O
"	O
,	O
because	O
"	O
unlike	O
transmittance	O
spectroscopy	O
,	O
there	O
were	O
no	O
reference	O
books	O
written	O
on	O
the	O
subject	O
"	O
of	O
"	O
diffuse	B-Algorithm
reflectance	I-Algorithm
spectroscopy	I-Algorithm
"	O
,	O
and	O
"	O
the	O
fundamentals	O
were	O
only	O
to	O
be	O
found	O
in	O
the	O
old	O
literature	O
,	O
some	O
of	O
which	O
was	O
not	O
readily	O
accessible	O
"	O
.	O
</s>
<s>
In	O
1975	O
,	O
Simmons	O
evaluated	O
various	O
theories	O
of	O
diffuse	B-Algorithm
reflectance	I-Algorithm
spectroscopy	I-Algorithm
and	O
concluded	O
that	O
a	O
modified	O
particle	O
model	O
theory	O
is	O
probably	O
the	O
most	O
nearly	O
correct	O
.	O
</s>
<s>
Therefore	O
,	O
the	O
remission	B-Algorithm
from	O
the	O
sample	O
contained	O
light	O
that	O
was	O
back-scattered	O
from	O
the	O
sample	O
,	O
as	O
well	O
as	O
light	O
that	O
was	O
transmitted	O
through	O
the	O
sample	O
,	O
then	O
reflected	O
back	O
to	O
be	O
transmitted	O
through	O
the	O
sample	O
again	O
,	O
thereby	O
doubling	O
the	O
path	O
length	O
.	O
</s>
<s>
In	O
1994	O
,	O
Donald	O
and	O
Kevin	O
Dahm	O
began	O
using	O
numerical	O
techniques	O
to	O
calculate	O
remission	B-Algorithm
and	O
transmission	O
from	O
samples	O
of	O
varying	O
numbers	O
of	O
plane	O
parallel	O
layers	O
from	O
absorption	O
and	O
remission	B-Algorithm
fractions	O
for	O
a	O
single	O
layer	O
.	O
</s>
<s>
They	O
were	O
able	O
to	O
show	O
the	O
fraction	O
of	O
incident	O
light	O
remitted	O
,	O
,	O
and	O
transmitted	O
,	O
,	O
by	O
a	O
sample	O
composed	O
of	O
layers	O
,	O
each	O
absorbing	O
a	O
fraction	O
and	O
remitting	O
a	O
fraction	O
of	O
the	O
light	O
incident	O
upon	O
it	O
,	O
could	O
be	O
quantified	O
by	O
an	O
Absorption/Remission	O
function	O
(	O
symbolized	O
and	O
called	O
the	O
ART	O
function	O
)	O
,	O
which	O
is	O
constant	O
for	O
a	O
sample	O
composed	O
of	O
any	O
number	O
of	O
identical	O
layers	O
.	O
</s>
<s>
The	O
ART	O
function	O
gives	O
results	O
approaching	O
equivalence	O
to	O
the	O
remission	B-Algorithm
function	O
.	O
</s>
<s>
The	O
Dahms	O
argued	O
that	O
the	O
conventional	O
absorption	O
and	O
scattering	O
coefficients	O
,	O
as	O
well	O
as	O
the	O
differential	O
equations	O
which	O
employ	O
them	O
,	O
implicitly	O
assume	O
that	O
a	O
sample	O
is	O
homogenous	B-General_Concept
at	O
the	O
molecular	O
level	O
.	O
</s>
<s>
The	O
reflection	O
and	O
back	B-Algorithm
scatter	I-Algorithm
is	O
lumped	O
together	O
as	O
remission	B-Algorithm
.	O
</s>
<s>
All	O
light	O
leaving	O
the	O
sample	O
on	O
the	O
same	O
side	O
as	O
the	O
incident	O
beam	O
is	O
termed	O
remission	B-Algorithm
,	O
whether	O
it	O
arises	O
from	O
reflection	O
or	O
back	B-Algorithm
scatter	I-Algorithm
.	O
</s>
<s>
If	O
one	O
has	O
measured	O
the	O
remission	B-Algorithm
and	O
transmission	O
fractions	O
for	O
a	O
sample	O
,	O
and	O
,	O
then	O
the	O
scatter-corrected	O
absorbance	O
should	O
have	O
half	O
the	O
value	O
for	O
half	O
the	O
sample	O
thickness	O
.	O
</s>
<s>
In	O
spectroscopy	O
,	O
remission	B-Algorithm
refers	O
to	O
the	O
reflection	O
or	O
back-scattering	B-Algorithm
of	O
light	O
by	O
a	O
material	O
.	O
</s>
