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Authors: Paul Weindorf, Paul Morris (Visteon Corporation)Shadi Mere (Insono Systems)
Automotive Total Biometric Automatic Luminance Control System
Introduction
SID 2015 Paper – Forward Looking Light Sensor Utilization for Automatic Luminance Control
Page 2
Internallightsensor
PWI = peak white intensityWSI = white stroke intensityFFVI = forward field of view intensityTC = time constantEXP = exponential function
fc .273X
Log potmanual
XPWI100
XFFVIWSI
Log
Remotelightsensor
X1.126
+0.2982
fc %PWI
TC↑ = 1 secTC↓ = 60 sec
exp
WSI(fL)
> 1
SetGF = 1
No
X YesGammacorrect
Tovideoamps
FFVI (fL)
Gain factor
Foward Looking Light SensorAmbient Light Sensor
Silverstein Automatic Display Luminance System[Paper reference 1, pg. 304 redrawn for clarity & adapted with loop arrows]
Introduction
SID 2015 Paper – Used a logarithmic forward looking light sensor and a logarithmic ambient light sensor
Page 3
ALSLogAmp
LogarithmicAmbientLight Sensor(ALS)
21
A/DLuminance Ratio Table
0 38.71 231 50.00 1232 64.58 2233 83.41 3234 107.72 4235 139.13 5236 179.69 6237 232.08 7238 299.74 8239 387.13 923
10 500.00 1023
ND LSEL 10 bit
A/D GF Table
DisplayUser Bias
∆NBD
DISPLAY5
ESLD
4 43 KNNK BDD
∆N
GF ∆N 1 0
1.328803 1 1.765719 2 2.346293 3 3.117763 4 4.142894 5 5.505092 6 7.315185 7 9.720443 8 12.91656 9 17.16357 10
LogarithmicFowardLookingLight Sensor(FFLS)
FLLS
LogAmp
A/D
Luminance Ratio Table
0 49.60 231 84.33 1232 143.35 2233 243.70 3234 414.29 4235 704.30 5236 1197.30 6237 2035.42 7238 3460.21 8239 5882.35 923
10 10000.00 1023
NH ESLH 10 bit
A/D
1.125log10 (LSEL )
GF
21 KNK H
0.2982
1.125log10 (FFVI) ESLH
HUD
13 DBD C
ODNN
D DBLBR
HUD UserBias ∆NBH
12
9
10
11
3
6
7
8
IntroductionSID 2016 Paper – Automotive Biometric Automatic Luminance Control System
– Biometric Forward Looking Light Sensor– Calculate pupil diameters using Unified Formula to construct step number table
Page 4
ALSLogAmp
LogarithmicAmbientLight Sensor(ALS)
21
A/DLuminance Ratio Table
0 38.71 231 50.00 1232 64.58 2233 83.41 3234 107.72 4235 139.13 5236 179.69 6237 232.08 7238 299.74 8239 387.13 923
10 500.00 1023
ND LSEL 10 bit
A/D GF Table
DisplayUser Bias
∆NBD
DISPLAY5
ESLD
4 43 KNNK BDD
∆N
GF ∆N 1 0
1.328803 1 1.765719 2 2.346293 3 3.117763 4 4.142894 5 5.505092 6 7.315185 7 9.720443 8 12.91656 9 17.16357 10
LogarithmicFowardLookingLight Sensor(FFLS)
Luminance Ratio Table
1.125log10 (LSEL )
GF
21 KNK H
0.2982
1.125log10 (FFVI) ESLH
HUD
13 DBD C
ODNN
D DBLBR
HUD UserBias ∆NBH
12
9 10
11
3
6
7
8
Camera
EyeEye GazeSystem
NH D log(La) ESLH 0 7.6 0.068 47
1 7.4 0.733 80
2 7.1 1.399 137
3 6.7 2.065 234
4 6.1 2.730 400
5 5.2 3.396 684
6 4.3 4.062 1170
7 3.5 4.728 2000
8 2.9 5.393 3420
9 2.5 6.059 5848
10 2.3 6.725 10000
Introduction
Forward looking light sensor is required to solve the light adaptation problem
Objective is to replace both the forward looking light sensor and the ambient light sensor with a biometric pupil diameter based light sensor measured by an eye gaze camera
Page 5
Forward-Looking Light Sensor
AmbientLight Sensor
SS
C
Driver Facing Camera
ObjectiveUtilize an eye gaze camera to determine driver pupil size
Use the pupil diameter to determine the driver observed reflected display background luminance instead of the ambient light sensors on the front of the display
Page 6
Figure 1-2. Eye Tracking Camera Images
Figure 1-3. Pupil Diameter Pupillometry Showing “Glint” [Reference 2]
Background
Many different models have been developed to determine pupil diameter.
Unified formula developed by Watson and Yellott from Stanley Davies formula appears to be a good model.
Unified formula uses the concept of corneal flux density which is a function of both luminance “L” and the viewing area “a” in degrees squared.
Page 7
Figure 2-1. Pupil Diameter Functions [Reference 4, Figure 16], Unified parameters are: Age=30 years, Binocular Vision, 60° Field Diameter
284684675.575.7,( 41.0
41.0
LaLaaLDSD
SDSDU DyyDD 009562.002132.00
y0 =28.58 yearsy = age in years
Background
Log of corneal flux density “La” may be derived from Unified Formula
Older person’s pupil does not dilate as much as a younger person under low luminance conditions
Page 8
0
41.0
0
0022.02
846205279.0
75.7
log41.01log
yyDyy
D
La
-1012345678
2 3 4 5 6 7 8lo
g(La
)Pupil Diameter D (mm)
28.58yr
60yr
y0 =28.58 years
y = age in years
Figure 2-2. Ages Factor Example for Pupil Dilation
Background
Determining the display reflected steady state value is more difficult due to short glance times
The eye pupil diameter responds in an exponential manner after a latency time
Page 9
Figure 2-4. Latency of the Pupil Light Reflex for Different Stimulus Intensities [8]
Figure 2-3. Pupillary light reflex to a blue light stimulus [7], Note: ADOA is an acronym for “autosomal dominant optic atrophy”
Implementation
Use the instantaneous diameter, velocity (slope) and acceleration vectors to determine the final steady state pupil diameter.
Page 10
ASDDF
2
D = Instantaneous Pupil Diameter
S = Instantaneous Velocity (slope)
A = Instantaneous Acceleration
DF = Final Steady State Pupil Diameter
Figure 2-5. Pupil Diameter Response Time Model [9]
Implementation
Example using exponential equation
Page 11
-0.08
0
0.08
0.16
0.24
0.32
0.4
0
1
2
3
4
5
6
0 10 20 30
Slop
e S
or A
ccel
erati
on A
Pupi
l Dia
met
er D
(mm
)
Time (sec)
D
S
A
Figure 2-6. Pupil Rise Time Example
64 10 teD
t D S A τ DF 0 2
0.1 2.039801 0.398007 0.2 2.079205 0.394046 -0.0396 9.950083 6
0.3 2.118218 0.390126 -0.03921 9.950083 6 0.4 2.156842 0.386244 -0.03882 9.950083 6 0.5 2.195082 0.382401 -0.03843 9.950083 6 0.6 2.232942 0.378596 -0.03805 9.950083 6 0.7 2.270425 0.374829 -0.03767 9.950083 6 0.8 2.307535 0.371099 -0.0373 9.950083 6 0.9 2.344275 0.367406 -0.03692 9.950083 6
1 2.38065 0.363751 -0.03656 9.950083 6 1.1 2.416663 0.360131 -0.03619 9.950083 6 1.2 2.452318 0.356548 -0.03583 9.950083 6 1.3 2.487618 0.353 -0.03548 9.950083 6 1.4 2.522567 0.349488 -0.03512 9.950083 6
1.0
1.0
tDtDS
ASDDF
2
1.0
1.0
tStSA
Implementation
Example for dynamic changing background luminance conditions
Page 12
-20246810121416
22.05
2.12.15
2.22.25
2.32.35
2.42.45
0 1 2 3
τ(s
ec) o
r Pu
pil D
F (m
m)
Dupi
l Dia
met
er (m
m)
Time after 400ms gaze transition (sec)
D
τ
DF
Figure 2-7. Gaze Time Example
Implementation
Calculating perceived luminance from steady state pupil diameter
Page 13
0.1
1
10
100
1000
10000
100000
1000000
2 3 4 5 6Lu
min
ance
cd/m
^2Pupil Diameter (mm)
L(a=1090)
L(a=500)
L(a=2000)
Figure 2-8. Luminance as a Function of Pupil Diameter for Various Solid Angles “a” in deg2
aDDLBG
84622
75.7 41.0141.0
1
Implementation
Page 14
LogarithmicAmbientLight Sensor(ALS)
DF Luminance Ratio Table
GF Table
DisplayUser Bias
∆NBD
DISPLAY5ESLD
4 43 KNNK BDD
∆N
GF ∆N 1 0
1.328803 1 1.765719 2 2.346293 3 3.117763 4 4.142894 5 5.505092 6 7.315185 7 9.720443 8 12.91656 9 17.16357 10
LogarithmicFowardLookingLight Sensor(FFLS)
Luminance Ratio Table
1.125log10 (LSEL )
GF
21 KNK H
0.2982
1.125log10 (FFVI) ESLH
HUD
13 DBD C
ODNN
D DBLBR
HUD UserBias ∆NBH
12
9 10
11
6
7
8
Camera
EyeEye GazeSystem
NH D log(La) ESLH 0 7.6 0.068 47
1 7.4 0.733 80
2 7.1 1.399 137
3 6.7 2.065 234
4 6.1 2.730 400
5 5.2 3.396 684
6 4.3 4.062 1170
7 3.5 4.728 2000
8 2.9 5.393 3420
9 2.5 6.059 5848
10 2.3 6.725 10000
Eye
Camera 2
1
Eye GazeSystem 3A
Final Pupil Diameter
ND LSEL log(LBG) DF 0 38.71 -0.215 6.0 1 50 0.193 5.5 2 64.58 0.600 4.9 3 83.41 1.007 4.4 4 107.72 1.414 3.9 5 139.13 1.821 3.4 6 179.69 2.228 3.0 7 232.08 2.635 2.7 8 299.74 3.042 2.5 9 387.13 3.449 2.4
10 500 3.856 2.3
3B
Conclusion
A biometric ambient light sensor may be developed using an eye gaze camera to measure the driver’s pupil diameter.
A biometric ambient light sensor is expected work better because the driver’s perceived display reflected background intensity is being utilized.
Age compensation is possible by changing the look-up table based on the Unified Formula and driver’s personalization data (age).
Page 15
Auto-luminance Book Debut
Announcing the release of auto-luminance book
Collection of papers
First Edition with more Chapters to follow
180 pages
Limited copies and memory sticks available at the Visteon Table
Will be available in the near future on Visteon website, www.visteon.com. Select “Innovation” and then select “Technical Papers”
Page 16
Page 17
www.visteon.com