Strictly Private and Confidential

Authors: Paul Weindorf, Paul Morris, Shadi Mere

Automotive Biometric Automatic Luminance Control System

Introduction

SID 2015 Paper – Forward Looking Light Sensor Utilization for Automatic Luminance Control

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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

Forward looking light sensor is required to solve the light adaptation problem

Objective is to replace the forward looking light sensor with a biometric pupil diameter measured by an eye gaze camera

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Forward-Looking Light Sensor

AmbientLight Sensor

SS

C

Driver Facing Camera

Introduction

SID 2015 Paper – Used a logarithmic forward looking light sensor

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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

ObjectiveUtilize an eye gaze camera to determine driver pupil size

Use the pupil size to determine the driver observed forward looking luminance

Use pupil diameter determined forward looking luminance for automatic luminance control system

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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.

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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

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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

ImplementationUse equal increments of Log(La) to construct table.

Equivalent to equal A/D count increments used with a logarithmic light sensor

Calculate pupil diameters using Unified Formula to construct step number table

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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

Conclusion

Biometric forward looking light sensor may be developed using eye gaze camera to measure the driver’s pupil diameter.

Biometric light sensor is expected work better because the driver’s perceived forward field of view 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).

Biometric light sensor may be also utilized for HUD automatic luminance control

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