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Preferred Tone Reproduction Curves of Transparent LCDs
Speaker: Hsin-Ping Chien (簡忻蘋)
Advisor: Prof. Pei-Li Sun (孫沛立教授)
ICC Display and 3D Print Meeting - Taipei 2016
2016.05.05
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Overview
• Transparent display
• Color models for two types of T-LCD• T-LCD (47” transparent LCD)
• HM-LCD (see-through head-mounted LC display)
• Visual experiments
• Results
• Conclusions
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Applications
• Office / Home (ex. Smart table, window)
• Augmented Reality
• Advertisement
• Vehicle HUD
• Education
• Architecture
• Military
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Types
• T-LCD
• T-OLED
• See-through HMD (head-mounted display)
• HUD (Head-Up Display)
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Image quality
• T-LCD• The polarizers and color filters block more than 80% of
the backlight.
• Backlighting is needed.
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Backlight off Backlight on
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Image quality
• HM-LCD (HMD)• A self-illuminated imaging device.
• Ambient lighting must be reduced.
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X O
AA AA
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Aims
• To illustrate the differences in terms of color characteristics of the two types of devices.• The effect of ambient lighting also will be shown.
• To conduct two psycho-visual experiments to derive preferred tone curves under different viewing conditions based on a hybrid S-curve.
7T-LCD HM-LCD
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Devices
Item T-LCD HM-LCD
Brand LG Epson
Model 47TS50MF-B BT-200
Transmittance (T) 7% 90%
Reflectance (R) at 45/0 0.5% 0.5%
Luminance (Yw) 0 nit 700 nit
gamma 2.54 2.45
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Characterization model for T-LCD
fKBGR
KBGR
KBGR
Z
Y
X
BTRC
GTRC
RTRC
ZZZZ
YYYY
XXXX
Z
Y
X
Z
Y
X
1
)(
)(
)(
00
00
00
T
%%%%
%%%%
%%%%
BL
BL
BL
View
9
(1)
Backlight
Normalized 3 by 4color mixing matrix including the XYZ values of RGB and black.
(TRC)
Transmittance
Gamma = 2.54
Front lightreflection
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sRGB vs. T-LCD under different whitepoint-surround luminance ratio
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Lightness Chroma
J (sRGB)
(B)(A)
C (sRGB)
J (u
nd
er d
iffe
ren
t w
hit
e lu
min
ance
)
C (
un
der
dif
fere
nt
wh
ite
lum
inan
ce)
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Characterization model for HM-LCD
fKBGR
KBGR
KBGR
BLViewZ
Y
X
BTRC
GTRC
RTRC
ZZZZ
YYYY
XXXX
Z
Y
X
Z
Y
X
1
)(
)(
)(
T (2)
3 by 4 color mixing matrix including the XYZ values of RGB and black.Back light
transmissionFront lightreflection
Transmittance
(TRC)
Gamma = 2.45
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sRGB vs. HM-LCD under different whitepoint (dark)-surround luminance ratio
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C (sRGB)J (sRGB)
Lightness Chroma(C) (D)
J (u
nd
er d
iffe
ren
t lu
min
ance
rat
io)
C (
un
der
dif
fere
nt
lum
inan
ce r
atio
)
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T-LCD vs. HM-LCD
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Visual Experiment: T-LCD
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Visual Experiment - T-LCD
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Ambient lighting:Illuminance: 2,000 luxCCT: 3,320K
White point luminance :248 cd/m2 & 35 cd/m2
(backlight adjustment)
Tone parameters :Brightness (Gamma)Contrast (S-curve)Chroma (gain)
Interactive tuningObservers:12Test images: 6
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Color tuning
Gamma curve(Brightness)
Create a Look-up-table to hybrid S-curve
RGB Y RGB’
Chroma
Cb Cr C’b C’r
Y’Sigmoidal curve(Contrast)
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GUI of the T-LCD experiment
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Result - T-LCD
2.35
1.35
0.98
1.97
1.29
1.5
2.71
2.18
1.64
2.4
1.78
2.35
1 2 3 4 5 6
0.0
0.5
1.0
1.5
2.0
2.5
Co
ntr
ast
images
248nit
35nit
0.25
0.15 0.14
0.17
0.12
0.2
0.46
0.27
0.4
0.44
0.29
0.34
1 2 3 4 5 6
0.0
0.1
0.2
0.3
0.4
Bri
gh
tne
ss
images
248nit
35nit
1 2 3 4 5 6
(E) (F)
6 test images
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Preferred tone reproduction curves for T-LCD
Result - T-LCD (tone)
(G)
(H)
(I)
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Result - T-LCD (chroma)
1 2 3 4 5 6
6 test images
(G)
1 2 3 4 5 6
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Chro
ma
Images
248 nit
35 nit
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Summary
• For T-LCD• When the backlight was darker, then the brightness of
the images must be increased.
• Contrast also need to be heighten in a darker condition.
• Chroma has no significant impact.
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Visual Experiment: HM-LCD
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Psycho-Visual Experiment - HM-LCD
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A diffuse projection screen
Ambient luminance:800 cd/m2 (6,000 lx)300 cd/m2 (2,300 lx)0 cd/m2 (0 lx)
Ambient CCT: 3,880K
Image manipulation: 5
Categorical judgementRating scale: 1-6
Observers:12Test images: 6
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Original
Increase the brightness
Decrease the brightnessDecrease the brightness
Increase the contrast
Image manipulation and rating scale
0.17 1.25 1.06
1 2 3 4 5 6
Worse Better
0 3 1.2
-0.17 1.25 1.06 -0.27 1.85 1.16
0 0 1
T1
T2 T5
T3 T4
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Result - HM-LCD
Preferred tone reproduction curves for HM-LCD
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Summary
1. For bright surround condition:• Score differences increased.
• Highest score decreased.
• Facial image degraded significantly by darkening the image.
2. Recommendations:• No compensation for dark surround condition.
• Brighten the image for normal indoor condition.
• Enhance contrast for bright surround condition.
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Conclusions
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1. Methods for characterizing the colors of T-LCD and HM-LCD under various lighting conditions are introduced. The color characteristics of the two devices are quite different.
2. We derive preferred tone reproduction curves of images for the transparent display (T-LCD) and see-through head-mounted display (HM-LCD) under different viewing conditions.
3. For T-LCD, the brightness and contrast of the images must be increased under low backlight luminance condition.For HM-LCD, we recommend the follows:
• No compensation for dark surround condition. • Brighten the image for normal indoor condition. • Enhance contrast for bright surround condition.