Comparison

Comparison of PJND with Mil-L-85762ADecember 1999

OverviewThe Mil-L-85762A Display Legibility & Readability MethodComparison of ambient illumination conditionsComparison of algorithms (PJND and Mil-L-85762A)Comparison of measurements Comparison of Acceptance CriteriaWorked examplesWhat model when ??!?Conclusions

The Mil-L-85762A Display Legibility & Readability MethodMil-L-85762A

Lighting, Aircraft, Interior, Night Vision Imaging System (NVIS) Compatible

The Mil-L-85762A Display Legibility & Readability Method

L1 = luminance adjacent to the activated display elementL2 = luminance of activated display elementL3 = luminance of deactivated display elementOn/Background contrastON/OFF contrastOFF/Background contrast

Mil-L-85762A Acceptance Criteria


L1 = luminance adjacent to the activated display elementL2 = luminance of activated display elementL3 = luminance of deactivated display elementOn/Background contrastON/OFF contrastOFF/Background contrastIncludes ambient illumination reflections from the display. (specular and diffuse)


Specular reflections


Diffuse reflections


L1 = luminance adjacent to the activated display elementL2 = luminance of activated display elementL3 = luminance of deactivated display elementOn/Background contrastON/OFF contrastOFF/Background contrastIncludes ambient illumination reflections from the display. (specular and diffuse)


L1 = luminance adjacent to the activated display elementL2 = luminance of activated display elementL3 = luminance of deactivated display elementOn/Background contrastON/OFF contrastIncludes ambient illumination reflections from the display. (specular and diffuse)


L1 = luminance adjacent to the activated display element+ luminance of diffuse reflections+ luminance of specular reflections

L2 = luminance of activated display element+ luminance of diffuse reflections+ luminance of specular reflections

L3 = luminance of deactivated display element+ luminance of diffuse reflections+ luminance of specular reflections

On/Background contrastON/OFF contrast


L1 = L(back) + L(d) + L(s)

L2 = L(on) + L(d) + L(s)

L3 = L(off) + L(d) + L(s)


L1 = L(back)) + L(d) + L(s)

L2 = L(on) + L(d) + L(s)


On/Background contrast

L1 = L(back)) + L(d) + L(s)

L2 = L(on) + L(d) + L(s)


On/Background contrastEquation 1

L1 = L(back)) + L(d) + L(s)

L2 = L(on) + L(d) + L(s)

PJND algorithmsForeground (on) luminanceBackground (off) luminance

PJND algorithmsForeground (on) luminanceBackground (off) luminanceLuminance ofdiffuse reflections

LJND algorithmsForeground (on) luminanceBackground (off) luminance

LJND algorithmsMil-L-85762A contrast

LJND algorithmsMil-L-85762A contrastMil-L-85762A contrast

LJND algorithms

LJND algorithmsExpands scale of our legibilitymetric

LJND algorithmsExample : AMLCDMaximum luminance 400 ftL (1,370 Cd/m**2) ; Black Contrast Ration 140:1 Specular reflectivity = 0.01 (1%) diffuse reflectivity = 0.0015 (0.15%)ExplanationExplanation

LJND algorithmsExample : AMLCDMaximum luminance 400 ftL (1,370 Cd/m**2) ; Black Contrast Ration 140:1 Specular reflectivity = 0.01 (1%) diffuse reflectivity = 0.0015 (0.15%)Conversion only true for this display characteristics

LJND algorithmsIncludes real transmission of visorNeeded if Relative contrast sensitivityto be included.

LJND algorithmsCompensates for increase in luminance contrast threshold as the luminance of the display background falls below 10,000 Cd/m2Includes real transmission of visorNeeded if Relative contrast sensitivityto be included.

LJND algorithms

LJND algorithmsThus, with a background task luminance of 1,000 Cd/m2 the RCS function is 0.83


the luminance threshold increases to 0.0061 from 0.0051

(i.e, 0.0051/0.83)


the luminance threshold increases to 0.0061 from 0.0051

(i.e, 0.0051/0.83)

That is

... the LJND of a display falls by 0.83 times because of the eyes loss of sensitivity at luminance levels below 10,000 Cd/m2

LJND algorithmsAmbient illumination :

LJND algorithmsThus, with a background task luminance of 115 Cd/m2 the RCS function is 0.7

LJND algorithmsSkip further explanationsDetailed Explanation 1Detailed Explanation 2

LJND algorithmsLJND = { Log10(luminance contrast) * RCS } /0.0051

LJND algorithmsLJND = { Log10(luminance contrast) * RCS } /0.0051LJND*0.0051/RCS = log10(luminance contrast)

LJND algorithmsLJND*0.0051/RCS = log10(luminance contrast) (LJND*0.0051/RCS) luminance contrast = 10

LJND algorithms (LJND*0.0051/RCS) luminance contrast = 10

LJND algorithms (LJND*0.0051/RCS) luminance contrast = 10Mil contrast = luminance contrast - 1

LJND algorithms (LJND*0.0051) luminance contrast = 10

RCS = 1

LJND algorithms (LJND*0.0051) luminance contrast = 10

LJND algorithms

LJND algorithms (LJND*0.0051/RCS) luminance contrast = 10

LJND algorithms

LJND algorithmsExample : AMLCDMaximum luminance 400 ftL (1,370 Cd/m**2) Black Contrast Ration 140:1 Specular reflectivity = 0.01 (1%) diffuse reflectivity = 0.0015 (0.15%)

RCS value = 0.479

LJND algorithmsRCS value = 0.479

LJND algorithms

LJND algorithmsRelates legibility parameter to number of Just Noticeable luminance steps present.... Units are JNDs

LJND algorithmsAllows real lighting environment to be fully represented:-- compensates for location in cockpit / exposure to glare-allows sun forward and dusk scenarios to be considered (not just sun rear)

LJND algorithms

Mil-L-85762A Lighting MeasurementsDiffuseIlluminationPhotometer

PJND Lighting Measurements

Mil-L-85762A Lighting Measurements Displayunder testSpecularIlluminationPhotometer

PJND Lighting Measurements


Compare acceptance criteria


Compare acceptance criteriaJustification of Acceptance Criteria unknown


Compare acceptance criteriaJustification of Acceptance Criteria unknown~ January 1986


Compare acceptance criteriaJustification of Acceptance Criteria unknownNADC-85060-20 does give assurance that acceptance criteria is based on a wide variety of studies etc.


Compare acceptance criteriaJustification of Acceptance Criteria unknownNADC-85060-20 does give assurance that acceptance criteria is based on a wide variety of studies etc.But the studies are not identifiednor are the performance criteriarepresented in the algorithms


Compare acceptance criteriaJustification of Acceptance Criteria unknownNADC-85060-20 does give assurance that acceptance criteria is based on a wide variety of studies etc.But the studies are not identifiednor are the performance criteriarepresented in the algorithmsAND


Compare acceptance criteriaJustification of Acceptance Criteria unknown

PJND Acceptance Criteria selected by aircrewWarning / Caution90 PJNDwarning or cautionrequiring attention

Dynamic Complex 70 PJND dynamic alphanumerics& fine line graphicStatic Complex60 PJNDstatic alphanumericsStatus50 PJNDfixed format, fixed legendInformative40 PJNDbackground informationAttention Getting120 PJNDattention getting capability required beyond fovean area

PJND Acceptance Criteria selected by aircrewDifferent illumination scenario's (sun rear, sun forwards & dusk)have the same acceptance criteria.

The ambient illumination used in the calculation reflects the ambientillumantion present in that scenario ...... AND the location of the display in the cockpit.

PJND Acceptance Criteria selected by aircrewDynamic Complex 70 PJND dynamic alphanumerics& fine line graphicWarning / Caution90 PJNDwarning or cautionrequiring attention

Status50 PJNDfixed format, fixed legendInformative40 PJNDbackground informationAttention Getting120 PJNDattention getting capability required beyond fovean areaStatic Complex60 PJNDstatic alphanumerics

PJND Acceptance Criteria selected by aircrewDynamic Complex 70 PJND dynamic alphanumerics& fine line graphicStatic Complex60 PJNDstatic alphanumericsWarning / Caution90 PJNDwarning or cautionrequiring attention

Status50 PJNDfixed format, fixed legendInformative40 PJNDbackground informationAttention Getting120 PJNDattention getting capability required beyond fovean areaJustification of Acceptance Criteria traceable toengineering biased experiments undertaken at BAe during mid to late 1980s

LJND Acceptance Criteria

The values of LJND that are considered acceptable by 97.5% of aircrew was determined through experimentation in 1989 to be :-

Informative displays >40 PJND'sStatus displays >50 PJND'sStatic Complex displays >60 PJND'sDynamic Complex displays >70 PJND'sWarnings and Cautions >90 PJND'sAttention Getting >120 PJND's

Example : colour CRT (from GLS)

Example : Reflective LCD (from GLS)

Example : Trans/flective LCD (from GLS)

Example : real AMLCD requirement

Example : real CRT

ConclusionsPJND more representative of the cockpit lighting/vision scenarioincorporates the real world lighting environment + the eyes capabilities ~ but is still an engineering toolincorporates glareincorporates relative contrast functionincorporates luminance threshold

ConclusionsPJND more representative of the cockpit lighting/vision scenarioincorporates the real world lighting environment + the eyes capabilities ~ but is still and engineering toolincorporates glareincorporates relative contrast functionincorporates luminance thresholdAcceptance Criteria PJND validated through experimentsMil-L-85762A experimental validation not accessible

LJND algorithmsExample : AMLCDMaximum luminance 400 ftL (1,370 Cd/m**2) ; Black Contrast Ration 140:1 Specular reflectivity = 0.01 (1%) diffuse reflectivity = 0.0015 (0.15%)

LJND algorithmsExample : AMLCDMaximum luminance 400 ftL (1,370 Cd/m**2) ; Black Contrast Ration 140:1 Specular reflectivity = 0.01 (1%) diffuse reflectivity = 0.0015 (0.15%)Assume between 50 and 70 acceptable

LJND algorithms126 ftL274 ftLChange in LJND = 23 (50-73)Example : AMLCDMaximum luminance 400 ftL (1,370 Cd/m**2) ; Black Contrast Ration 140:1 Specular reflectivity = 0.01 (1%) diffuse reflectivity = 0.0015 (0.15%)

LJND algorithmsChange in Mil-L Contrast is 3.9i.e., from 3.5:1 to 7.4:1Example : AMLCDMaximum luminance 400 ftL (1,370 Cd/m**2) ; Black Contrast Ration 140:1 Specular reflectivity = 0.01 (1%) diffuse reflectivity = 0.0015 (0.15%)

Comparison of ambient Illumination

Comparison of ambient Illumination

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