Display Technology and Ambient Illumination - Virginia Tech

139 Pages·2001·0.46 MB·English

by  Aaron Bangor

DDiissppllaayy TTeecchhnnoollooggyy aanndd AAmm bbiieenntt
IIlllluu mmiinnaattiioonn IInnfflluueenncceess oonn VViissuuaall
FFaattiigguuee aatt VVDDTT WW oorrkkssttaattiioonnss

Aaron W. Bangor

Dissertation submitted
to the Faculty of the
Virginia Polytechnic Institute and State University
in partial fulfillment of the requirements f or the degree of

ROTCODY HFPOOSOLIHP

in

Industrial and Systems Engineering

______________________________
Dr. Robert J. Beaton, Chair

______________________________ ______________________________
Dr. Thomas A. Dingus Dr. Albert M. Prestrude

___ ___________________________ ______________________________
Dr. C. Patrick Koelling Dr. Eileen Van Aken

December 19, 2000
Blacksburg, Virginia

KKeeyywwoorrddss: visual fatigue, visual discomfort, ambient illumination, CRT, LCD,
office work, VDT, VDU, image quality, contrast sensitivity

© Copyright 2000, Aaron W. Bangor
Display Technology and Ambient Illumination Influences on Visual Fatigue at VDT Workstations Aaron Bangor

DDiissppllaayy TTeecchhnnoollooggyy aanndd AAmmbbiieenntt IIlllluummiinnaattiioonn IInnfflluueenncceess oonn
VViissuuaall FFaattiigguuee aatt VVDDTT WWoorrkkssttaattiioonnss

Aaron Bangor

((AABBSSTTRRAACCTT))

The concept of “visual fatigue” has been studied for 70 years or more. In that
time, no single metric of measuring visual fatigue nor one agreed-upon set of
tasks to induce visual fatigue has been settled upon. Not even a robust
definition of visual fatigue has been established. This research worked to solve
some of those problems.

This research first set out to develop an index of visual fatigue that could be
used effectively in quantifying the subjective experience of visual fatigue. Then it
sought to create a set of measurable tasks, representative of office work, that
would induce visual fatigue. Taking these two developments, an experiment
using human participants was conducted to validate these developments and
work toward solving two issues in the visual fatigue field: how visual display
technology and ambient illumination affect the onset of visual fatigue. A 4x4
within-subjects design was developed and executed to study how these two
independent variables affected ratings of visual fatigue, performance on the task
battery, subjective image quality judgments, and contrast sensitivity shifts.

Two cathode ray tube (CRT) and two active-matrix LCD (AMLCD) monitors were
used in this study. While many instances of the monitors as a whole caused
significant differences in reports of visual fatigue, performance, subjective image
quality, and contrast sensitivity loss, only a slight effect of display technology was
found. Four of eleven visual fatigue and two of eight subjective image quality
dimensions showed that the LCD monitors induced more visual fatigue and were
rated poorer than the CRT monitors.
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Display Technology and Ambient Illumination Influences on Visual Fatigue at VDT Workstations Aaron Bangor

Ambient illumination levels of 0, 300, 600, and 1200 lux affected all four groups
of dependent variables. On the whole, lighting caused visual fatigue, with
“watery eyes” and “glare from lights” being adversely affected by brighter
lighting. The 0 and 1200 lux were associated with the worst performance, while
300 lux was associated with the best performance. Subjective image quality was
affected by lighting, with increasing lighting causing bothersome screen
reflections and more temporal (e.g., flicker and jitter) distortions; 600 lux induced
more reports of image sizing anomalies. Finally, it caused significantly worse
shifts at the 6.0 c/deg spatial frequency on the contrast sensitivity test. The data
show that lighting of 300 lux is the best of these four illumination levels.

The results of this study not only contribute to the body of research in the areas
of display technology and ambient illumination, but several developments of this
research are offered to the research community: a complete survey metric of
visual fatigue, a standardized battery of tasks for studying visual fatigue and
image quality, and a comprehensive subjective image quality survey.

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Display Technology and Ambient Illumination Influences on Visual Fatigue at VDT Workstations Aaron Bangor

AACCKKNNOOWWLLEEDDGGEEMMEENNTTSS

First, I would like to thank Dr. Robert Beaton for his advice and guidance in this
course of my graduate studies at Virginia Tech. I would also like to thank him
and LG Electronics for the opportunity to work on a large and supported
research project. While the freedom and flexibility of my independent thesis
study was extremely satisfying and enjoyable, I am glad and feel that much more
enriched by having worked on a contracted research project.

I would like to thank the rest of the my committee: Drs. Tom Dingus, Pat
Koelling, Al Prestrude, and Eileen Van Aken for the work they have put into my
preliminary examination and this dissertation, as well as the advice they have
provided along the way. I would also like to thank Dr. Koelling especially for
being on both my M.S. and Ph.D. committees, as well as being one of the best
undergraduate professors I had at Tech.

Above all I would like to express my sincere admiration and respect for my
parents who are the principal reason for why I have attained this level of
achievement. My successes are a reflection on their parenting.

Finally, I would like to thank Gary Olacsi, Teresa Coalson, George Probst and all
of the other members of the DCL who have helped me in innumerable ways (not
to mention kept me sane) since I joined the Lab in May of 1995.

While this may not be as long as The Winning of the West, but hopefully it has
been done just as well.
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Display Technology and Ambient Illumination Influences on Visual Fatigue at VDT Workstations Aaron Bangor

TTAABBLLEE OOFF CCOONNTTEENNTTSS

)TCARTSBA( ................................ ................................ ................................ ................................ ......... II
STNEMEGDELWONKCA ................................ ................................ ................................ ................. VI
N O0I.T1CU DORTNI ................................ ................................ ................................ ............................ 1
2.0 BACKGROUND ................................ ................................ ................................ .............................. 4
2.1 C FO NOITACIFISSAL V LAUSI F EUGITA ................................ ................................ ............................... 5
2.1.1 Medical and Optometric Issues ................................ ................................ .............................. 6
2.1.2 namuH scimonogrE/srotcaFseussI ................................ ................................ ....................... 10
2. 2H NAMU F SROTCA /E RGONOMIC M ETHFOODRS E GNITAULAV V LAUSI F EUGITA ................................ .17
2.2.1 Visual Fatigue Experiments ................................ ................................ ................................ .. 18
2.2.2 Visual Fatigue Questionnaires ................................ ................................ ............................. 20
2.3 T HE TRC DNA DDCL YALPSI T ECHNOLOGIES ................................ ................................ ................ 22
2.3.1 CRT Display Technology ................................ ................................ ................................ ...... 22
2.3.2 LCD Display Technology ................................ ................................ ................................ ..... 24
3.0 METHODS ................................ ................................ ................................ ................................ ..... 29
3.1 M ONITORS ................................ ................................ ................................ ................................ ... 29
3.2 O LACITP I EGAM Q YTILAU T ESTING ................................ ................................ ................................ 29
3.2.1 Equipment ................................ ................................ ................................ ............................ 29
3.2.2 Procedures ................................ ................................ ................................ ........................... 30
3. 3H NAMU P ECNAMROFRE T EST ................................ ................................ ................................ ......... 31
3.3.1 Methods ................................ ................................ ................................ ............................... 31
3.3.2 Participants ................................ ................................ ................................ .......................... 33
3.3.3 Equipment ................................ ................................ ................................ ............................ 34
3.3.4 Procedures ................................ ................................ ................................ ........................... 34
1.4.3.3 g ndirsoskWescaoTrP ................................ ................................ ................................ .................. 35
3.3.4.2 Data Entry Task ................................ ................................ ................................ ........................... 36
3.4.3.3 beW gnisworBksaT ................................ ................................ ................................ ..................... 37
3.4 V LAUSI F EUGITA M TNEMERUSAE ................................ ................................ ................................ ... 38
3.5 P ECNAMROFRE M TNEMERUSAE ................................ ................................ ................................ ..... 39
3.6 S EVITCEJBU I EGAM Q YTILAU R ATING ................................ ................................ ............................ 39
3.7 C ONTRAST S ENSITIVITY M TNEMERUSAE ................................ ................................ ........................ 40
SDS INT0DAL.U 4SER NOISSUC ................................ ................................ ................................ ...... 42
4.1 V LAUSI F EUGITA ................................ ................................ ................................ ........................... 42
4.1.1 Visual Fatigue Questionnaire Reduction ................................ ................................ .............. 42
4.1.2 Multivariate Analysis of Variance ................................ ................................ ........................ 50
4.1.3 Analyses of Variance ................................ ................................ ................................ ............ 52
a WfA“ oV1O .N3A.1.4 ”se yyEret ................................ ................................ ................................ ........... 52
” g,ny i t2rn,t.ordi3u er. BAtG1 Va .s Otf4eeNioyrArEar“I ................................ ................................ ....... 53
3.3 . A ”1V nl.Ofi l4Noand aAPi neb“ruheootyrEa ................................ ................................ .................. 55
e hnstimiLew l4 b.A o3 Vfr.OoP1N“.A4 -”gnikcart ................................ ................................ ................... 56
”gnisu cynotiFluciff i AfD5Vo“. O3N.A1.4 ................................ ................................ ............................. 58
”srett eyLggo FfA“o V6O .N3A.1.4 ................................ ................................ ................................ ......... 60
”sth gmi oLerrfa lA7fGV.o “O3N.A1.4 ................................ ................................ ................................ ... 61
”noi syirVru lA8fBV.o “O3N.A1.4 ................................ ................................ ................................ ......... 62
4.1.4 Correlational Analysis ................................ ................................ ................................ ......... 64
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Display Technology and Ambient Illumination Influences on Visual Fatigue at VDT Workstations Aaron Bangor
2. 4H NAMU P ECNAMROFRE ................................ ................................ ................................ ................. 65
4.2.1 Multivariate Analysis of Variance ................................ ................................ ........................ 66
4.2.2 Analyses of Variance ................................ ................................ ................................ ............ 67
e mginTissec odr rP ro AoW1Vf. O2N.A2.4 ................................ ................................ .............................. 67
sro rgrnEissec odr r ProA2oWV.f O2N.A2.4 ................................ ................................ ............................ 69
4.2.3 Correlational Analysis ................................ ................................ ................................ ......... 72
4.3 S EVITCEJBU I EGAM Q YTILAU ................................ ................................ ................................ .......... 72
4.3.1 Subjective Image Quality Survey Reduction ................................ ................................ ......... 73
4.3.2 Multivariate Analysis of Variance ................................ ................................ ........................ 75
4.3.3 Analyses of Variance ................................ ................................ ................................ ............ 77
1.3g .n ” 3iAl. tVl4raOa oRNrefAehvtO“ ................................ ................................ ................................ .77
2.3. g3 ”n.Ati4V stOraaNo rRAfethntoC“ ................................ ................................ ............................... 78
3.3.3. 4 AVO N”rgAsonsfie tneaphRrtahS“ ................................ ................................ ............................. 80
gn i”tra oR4 l.Areo3 VohC.Oft“3N.A4 ................................ ................................ ................................ .... 81
5.3.3 . 4g”AnsVis OterNanoARt fheghitrB“ ................................ ................................ ............................ 82
gn i”t ga6nR .i A3zr eV.iohO3SftN.“A4 ................................ ................................ ................................ ... 84
7 .Aree3 VohT.Oft“3N.A4 ”lganriotpamR ................................ ................................ ............................. 86
8.3.3 .A4V O rgN”on AefierthaatlRG“ ................................ ................................ ................................ .... 88
4.3.4 Correlational Analysis ................................ ................................ ................................ ......... 89
4.4 C ONTRAST S ENSITIVITY ................................ ................................ ................................ ................ 90
4.4.1 Multivar iate Analysis of Variance ................................ ................................ ........................ 9 1
4.4.2 Analyses of Variance ................................ ................................ ................................ ............ 93
gy etf0dio./v6citi stnsea Sr1 t.Arn2 Voo.OfC4N.A4 ................................ ................................ ............... 93
y t0fi.o/v2ci1ti stn se2aS. r 2At r.Vno4Oof.NC4A ged ................................ ................................ ............. 95
g ey 0dtf./io8cv1iti stnse aS3r .tAr2n Vo.oOf4CN.A4 ................................ ................................ ............. 96
4.4.3 Correlational Analysis ................................ ................................ ................................ ......... 99
4.5 C SNOITALERRO A MONG D ATA S ETS ................................ ................................ .............................. 99
6.4 R NOISSERGE A SISYLAN ................................ ................................ ................................ ............... 102
0.5 ,STN EMPOFLEVED ,DHNCARA EESREURTU SNOITUBIRTNOC ................................ ... 104
5.1 D STNEMPOLEVE ................................ ................................ ................................ .......................... 104
5.1.1 Comprehensive Visual Fatigue Questionnaire ................................ ................................ .... 104
5.1.2 Office Task Battery ................................ ................................ ................................ ............ 105
5.1.3 Augmented Subjective Image Quality Survey ................................ ................................ ...... 106
5.2 F ERUTU R HCRAESE P SEITILIBISSO ................................ ................................ ................................ 107
5.3 C ONTRIBUTIO SN ................................ ................................ ................................ ......................... 108
SECNEREFER ................................ ................................ ................................ ................................ .... 110
:XAIDNEPPA ................................ ................................ ................................ ................................ ..... 114
X:IBDNEPPA ................................ ................................ ................................ ................................ ..... 117
:XCIDNEPPA ................................ ................................ ................................ ................................ ..... 119
:XDIDNEPPA ................................ ................................ ................................ ................................ ..... 120
:XEIDNEPPA ................................ ................................ ................................ ................................ ..... 123
ATIV ................................ ................................ ................................ ................................ .................... 129

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Display Technology and Ambient Illumination Influences on Visual Fatigue at VDT Workstations Aaron Bangor

LLIISSTT OOFF FFIIGGUURREESS

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Display Technology and Ambient Illumination Influences on Visual Fatigue at VDT Workstations Aaron Bangor
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viii
Display Technology and Ambient Illumination Influences on Visual Fatigue at VDT Workstations Aaron Bangor

LLIISSTT OOFF TTAABBLLEESS

TABLE 2.1 – stnemir eepuxgE iltaa uFlsa i r eV ekmrnvsiooeaTfST 11
TABLE 3.1 – de traorstbgiinnlioatMCteS 30
TABLE 3.2 – tnemir eepcxnEamro fnr aesremPnohuoftHiti dtnnoecmt aerT 32
TABLE 3.3 – tnemi reec pnrtxa enEmrder orm onefOtfaharmteeurPHT 33
TABLE 4.1 – ”ys ree eyurt Eg oal iAf WatVr“uaOosFNfiAV 52
TABLE 4.2 – AVON Ar o lfe au,ugdsyiei tttVrtaaoiFtfriGrrI“ , ro”gninruB 54
TABLE 4.3 – ”llab eed yhn nEtu ni oriareroPoua“fgi tlaaFu srAioV VfONA 55
TABLE 4.4 – e nh itsLimwelbo rrePou“fgi tlaaFu srAioV VfONA - tracking” 56
TABLE 4.5 – ”gnis u ycntoilFuciff ireDou“fgi tlaaFu srAioV VfONA 58
TABLE 4.6 – ”sre t’tyegLg oerFuo’gf “ilta a uAFr sVoiOfVNA 60
TABLE 4.7 – ”st h mgeoirr L aFerluoGgf“ iltaa uFArs VoiOfVNA 61
TABLE 4.8 – ”no iysrir V uerluoBgf “ilta a uAFr sVoiOfVNA 63
TABLE 4.9 -- smotp meyuSgi tlaaFu s rixoVifr tnaoMitaler rnooCsr aeP 65
TABLE 4.10 – ecnamro fAr rVoeOfPNA e mginTissec od rrfPooW 68
TABLE 4.11 – r ogrnriEsse ce docfrrnooPaWmro fArr VoeOfPNA 70
TABLE 4.12 – ecnam rx o irfnrorotfeiaPtMal enror sorCaeP 72
TABLE 4.13 – VONA Ae vyei tgt”riagclo lmnelfraIijaoutbrfQaueRSvO“ 77
TABLE 4.14 – g n”ittsa aRy rtr t ioe nelfheogatvCaui“mQtI c A eVrjOobNfuAS 79
TABLE 4.15 – eyn tpr i roeeleafghavhatuiSmQt “I cA eVrjOobNfuAS g n”istsaR 80
TABLE 4.16 – gn i” tr yao rtRleoi ohfle Ctage“uavQmiItc e A jrVboOufNSA 81
TABLE 4.17 – AeV vOyei NtgtrA iaco” lmefgsraIjnsoubiefQutn SateRhhgtirB“ 83
TABLE 4.18 – y e tevA igiV rlat Og”oamcrNng fuIeoAineQjftihbaztuRiSS“ 84
TABLE 4.19 – g n”ilt aayr Rtor i poeelemfghaveatuiTmQt“ I cA eVrjOobNfuAS 86
TABLE 4.20 – ea gueaQvmiItce jArb VouOfSNA lity for the “Glare” Rating 88
TABLE 4.21 -- yt ieelgvaaiu mtQxI c inerrojotibfatuMaSl enro rsorCaeP 90
TABLE 4.22 – yt ifv oig0t e.it d6ssA/na VcerrOStoNnfAoC 93
AT BLE 4.23 – yti vf io0g t.e ti2dAss1/V ancOrreNotSAfnoC 95
TABLE 4.24 – yti vf io0g t.e ti8dAss1/V ancOrreNotSAfnoC 97
TABLE 4.25 -- ytivit itssn aex rS irtnronotfoiaCtMal enror sorCaeP 99
TABLE 4.26 – s atgte naSxoDim rAntoaiMtale rnroosC raeP 101

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Display Technology and Ambient Illumination Influences on Visual Fatigue at VDT Workstations Aaron Bangor
LLIISSTT OOFF EEQQUUAATTIIOONNSS

(Eq. 4.1) 102
x