Li
g
h
t W
av
elength (nm)
400
700
500
600
Rel
ati
ve Intensit
y
Li
g
h
t W
av
elength (nm)
400
700
500
600
Rel
ati
ve Intensit
y
Li
g
h
t W
av
elength (nm)
400
700
500
600
Filter
Transmissio
n
Li
g
h
t W
av
elength (nm)
400
700
500
600
Filter
Transmissio
n
Li
g
h
t W
av
elength (nm)
400
700
500
600
Filter
Transmissio
n
Li
g
h
t W
av
elength (nm)
400
700
500
600
Rel
ati
ve Intensit
y
Li
g
h
t W
av
elength (nm)
400
700
500
600
Rel
ati
ve Intensit
y
Li
g
h
t W
av
elength (nm)
400
700
500
600
Rel
ati
ve Intensit
y
Li
g
h
t W
av
elength (nm)
400
700
500
600
Rel
ati
ve Intensit
y
Li
g
h
t W
av
elength (nm)
400
700
500
600
Rel
ati
ve Intensit
y
Li
g
h
t W
av
elength (nm)
400
700
500
600
Rel
ati
ve Intensit
y
Li
g
h
t W
av
elength (nm)
400
700
500
600
Rel
ati
ve Intensit
y
Li
g
h
t W
av
elength (nm)
400
700
500
600
Filter
Transmissio
n
Li
g
h
t W
av
elength (nm)
400
700
500
600
Filter
Transmissio
n
Li
g
h
t W
av
elength (nm)
400
700
500
600
Filter
Transmissio
n
Light from Red, Green
and Blue LEDs is
combined in the folded
light guide.
White light is filtered
back into Red, Green
and Blue sub-pixels.
The modified blue filter
further enhances blue
spectrum.
Resulting spectrums
are very pure which
gives a very wide color
gamut.
LED Backlight
Typical CCFL Backlight
Resulting
spectrums contain
unwanted colors
such as yellow,
cyan and orange
which reduces the
color gamut.
Comparison of LED and CCFL Backlight Color Gamuts
White light from
CCFL is filtered
back into Red,
Green and Blue
sub-pixels.
Why not use white LEDs?
White LEDs typically emit white light by using either a blue
LED
with
a
yellow
phosphor
coating,
or
an
ultra-violet
LED
with
a mix of red, green and blue phosphor coatings. The spectrum
of the white light has many of the drawbacks of using a CCFL
backlight and does not produce a wide color gamut.
Additionally, the white point, or color temperature, of the
white LED output is fixed. Therefore the advantage of being
able to adjust the white point by varying the individual red,
green and blue LED intensities would be lost.
Li
g
h
t W
av
elength (nm)
400
700
500
600
Rel
ati
ve Intensit
y
Li
gh
t W
av
elength (nm)
400
700
500
600
Rel
ati
ve Intensit
y
