mes displays introduction metrologyeitidaten.fh-pforzheim.de/.../mes_displays_introduction_metrology.pdf · MES Multimedia - Displays: Introduction Blankenbach / Pforzheim Univ

MES Multimedia - Displays: Introduction

Blankenbach / Pforzheim Univ. / www.displaylabor.de / MES / March 2008

D I S P L A Y L A BPFORZHEIM UNIVERSITY


1

Karlheinz Blankenbach

Pforzheim University, Germany

Master in Embedded Systems, Pforzheim, SS 2008

Prof. Dr. Karlheinz Blankenbach

Pforzheim University

Tiefenbronner Str. 65

D-75175 Pforzheim, Germany

Phone : +49 7231 - 28 - 6658

Fax : +49 7231 - 28 - 6060

Email : [email protected]

Web : www.displaylabor.de





2

Objective of Lecture

• Understanding of applications of electronic displays

• Know how of advanced display technologies

• Knowledge of relationships between electronics �� interface �� display

• Capability to design embedded (information) systems

with the ‘best’ display





3

Recommended Textbooks

- L.W. MacDonald, A.C. Lowe: Display Systems, WILEY SID

- P.A. Keller: Electronic Display Measurement, WILEY SID

- Green, MacDonald: Color Engineering, WILEY SID

- Ernst Lueder: LCDs : Addressing Schemes and e-o Effects, WILEY SID

- Willem de Boer: AM Liquid Crystal Displays, NEWNES

- R.L. Myers: Display Interfaces, WILEY SID

- G. Berbecel: Digital Image Display, WILEY SID





4

• Display Interfaces

• Introduction

• Selected Topics on Advanced LCDs, OLEDs and PDPs

Overview

• 3D & E-Paper (flexible) Display Technologies

• Touch Screen Technologies

- Market overview

- Some basics of metrology





5

Worldwide Flat Panel MarketWorldwide Flat Panel Market

0

10

20

30

40

50

60

2002 2003 2004 2005 2006 2007

Bill. $

AM LCD

PM LCDPDP

Other FPDs

Source :

iSupply

- 50% of FPD in 2006- PC and TV only indeveloping countries

CRTs





0

5

10

15

20

25

30

35

Noteb

ooks

Mon

itor

s

Mob

ile

Autom

otiv

eTV

Indus

trial

Pho

to

2004

2007

2009

6

Top 7 FPD Applications

~ 100% AM LCD except for TVWorldwide Turnover / B$





7

Worldwide Flat Panel Market by Regions





8

Worldwide Flat Panel Market by Applications





9

Worldwide Units by Applications

2007:

Production

60,000 m²





10

Shift of FPD Production

From Japan to Korea & Taiwan to (?) China





11

AM LCD “Application Waves”





12

Worldwide Flat Panel Market : Small / Medium LCDs (< 10”)

Price per display shrinks !





13

Worldwide Flat Panel Market : AMLCD > 10“ Mio. / B$ p.a.

0

2

4

6

8

10

12

14

16

18

SAM

SUNG

LG:P

HIL

IPS

AUO

CM

O

SHARP

CPT

HANNSTA

R

INNOLU

X

BOE-O

T

Oth

ers

2006

2007

Ranked acc. turn-over: compare e.g. SHARP and CPT





14

Worldwide Flat Panel Market : AMLCD > 10“ Mio. / Units p.a.

0

10

20

30

40

50

60

70

80

90

SAM

SUNG

LG:P

HIL

IPS

AUO

CM

O

SHARP

CPT

HANNSTA

R

INNOLU

X

BOE-O

T

Oth

ers

2006

2007

Ranked acc. turn-over: compare e.g. SHARP and CPT





15

Worldwide Flat Panel Market : LED Backlight for LCDs

LCD < 5“: ~ 100% LED





16

Worldwide Flat Panel Market : OLEDs

• Left: Linear rise or S-curve – compare to mobile devices (right)

• Left: 10 M$ ticks reasonable ?

• OLEDS in total are about 1.5% of total LCD-market in 2006





17

Worldwide Flat Panel Market : Car Navigation





18

Worldwide Market : Head - Up Displays





19

Worldwide Market : Touch Screens





20

Worldwide Market : Low Power and Zero Power Displays





21

Commodityup to 65” (2007)

LCD TV Race (Prototypes)

2004 : 57“

2005 : 82“

2006 : 108“

Gen 10





22

The Race for Size is limited by Mother Glass Size

Commercially in MP available:

- LCD up to 70”

- PDP up to 70” (PANASONIC 103“: 100,000 $)

Forced by

trend to signage

(POI, small sized

indoor billboards, …

SHARP 108” LCD prototype

PANASONIC 150” PDP

CES 2008





23

The Race for Size (I)

Production issue

Micrometer

precision

required in

meter range !





24

The Race for Size (II)

• Gen 8 = 1 B$

• SHARP announced

Gen 10 for 2010

SAMSUNG





25

Projection

system

Flat Panel Display World

1 10 20 40 60 Display Size /“

Resolution

QXGA

HDTV

SXGA

XGA

SDTVVGA

QVGA Low information content displays

Note-book

PC-monitor

LCDTV

Car

MP, PDA

150 ppi

p-Si a-Si

PDP

Projection





26

User quality → Technical specification

'Good readability‘ Optics, electronics, application, …

How to Select a Display

Magic Circle

Optics

Electronics

Electro-optics

Application

Pixel driving,

e-o characteristics,

rise & fall time,

ghosting, …

Luminance, contrast,

grey scale, colour,

response time, uniformity

viewing angle, reflections, ...

Size, weight, price, lifetime,

power supply, reliability,

mature technology,

temperature, vibration,

displayed data, ...

Driving, voltages,

signal processing,

power consumption,

EMI, data input, ...





27

• Summary

• Introduction

• Basic Parameters (Merits)

Overview

• Common Issues

• Display Technology Dependent Issues (Shortcomings)

- Motivation

- Some basics of vision





28

Why Measuring Electronic Displays ?

Merits of display metrology

• Human vision is only descriptive

• Standardized measurement setups and test patterns

• Specifications enable judging of displays

• Wide range of measurement procedures for many applications

Shortcomings of display metrology

• Ambient light (simulation) difficult, therefore most of

the specified values are measured under dark room conditions

• Vision sees things that measurement can’t capture and vice versa





29

Basic Characteristics of Vision

Resolution Spectral Sensitivity for

Day and Night

• Angular resolution : 1‘

at optical axis

Example: 0.3mm @ 1m

• Time resolution ~ 50 ms (20 Hz)

up to 100 Hz flicker sensitive

• ~ 500,000 colors can be

distinguished

… plus ‚signal processing‘ (brain)





30

Sea of Measurement Tasks

Test patterns

Full, box, checkerboard, grille,

grey level, color, dynamic, moving, …

Measurement

of luminance

and/or color

Dark room or (simulated)

ambient light

Viewingangle

Environment

Temperature,

% rH, EMI,

power supply,

…

Procedure,

data storage

• Spatial

• Temporal

- Jitter

- Warm up

- T-change

- Lifetime

DUT

Driving

system

Signal

processing





31

• Summary

• Introduction


Overview

• Common Issues


- B/W, GS, color

- L, CR, GS, color

- Parameters & vision

Color Calculator:

www.radiantimaging.com/





32

• Luminous flux (power) : F / lm

• Luminance : L / (emitter)

• Illuminance : E / (receiver)

Illuminance = power / area :

Photometric Units

2m

cd

2m

lmlx =

A

F

Ad

FdE ==

Examples - Luminous flux F = 1,000 ANSI lm for projector

- Luminance L = 300 cd/m² for AMLCD

- Illuminance for 1,000 lm projector at 2 x 3 m² → E = 167 lx

compare to 500 lx recommended at workplace!

Units: RI Color Calculator





33

• [L] = cd/m²

• Typical values : Displays 50 … 1,000 cd/m², bulb 10,000 cd/m²,

sun at noon 108 cd/m², full moon 100 cd/m²

• Basic value for contrast, grey scale, uniformity, viewing angle, ...

• One of three parameters for color measurements (Tristimulus)

• Measurement conditions

- Dark room unless otherwise noted

- Centre of display, perpendicular incidence

- Usually F.O.V. of > 25 pixel for monitors

- V(λ) corrected devices

Luminance

Same for color





34

Example of Optical Specification for AM LCD (II)

Recommendation: Use same device as in spec!





35

Contrast Ratio

• Luminance ratio of bright / white / max / ON to dark / black / min / OFF

• Various definitions, mostly contrast ratio used, MTF s. b.

Remarks • High CR can be critical because of measurement error for Lblack

• Vision range : CR = 3 : 1 - 500 : 1

• CR ≈ 10 : 1 recommended for non-fatigue reading (paper !)

• High CR can bother (e.g. car headlights at night) !

• CR in specs measured without ambient light ! E� → CR�

• Various conditions like full screen, checkerboard, …

• Contrast ratio

...L

L

L

LC

black

white

dark

bright

R ==Example

Paper ≈ 10 : 1 Lwhite Lblack

… is not a measure for readability of text (full screen)!





36

Contrast Ratio Test Patterns

• Full screen

• Centered box

• Checkerboard

(Projection)

• Intra-Character

CR depends on test

pattern, especially for

- PM drive (ghosting)

- PDP

- Projection

Used for PDP � CR ≈ 1,000:1

LCD, OLED, PDP CR ≈ 100:1





37

LED LCD - Backlight Improvements : Local Dimming

Power saving 50% average (image dependant)

Lmax = 630 cd/m2

Lmin = 0.03 cd/m2

� CR = 630 / 0.03

= 21,000 : 1

High Contrast





38

Modulation Transfer Function & Resolution

• Contrast modulation = MTF

darkbright

darkbrightGrilleM

LL

LLC

+

−=

• Threshold

- Text

- Images

5.0CGrilleM ≥

25.0CGrilleM ≥

I,Tn

linesofNumberR =

• Resolution

• (Analogue) bandwidth

• Ghosting, …

n

Measure for text

readability





39

Grey Scale Measurements

0

0.2

0.4

0.6

0.8

1.0

0 0.2 0.4 0.6 0.8 1.0

rel. Grey Level

LCD 18"

LCD 8.4"

L ~ D 2.3

CRT

rel. Luminance

Deviations

log (norm. Grey Level)

log (norm. Luminance)

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

-2.0 -1.5 -1.0 -0.5 0.0

log(Luminance)

gamma 2.5

log(Luminance - L(0))

• Greyscale for images, …

• Results: Gamma, GS resolution, …

• Gamma is seldom specified

Grey

bars or

full screen

Contrastratio onlymax / min !





40

Color Space CIE 1931

• Oldest CIE standard

• Still in use today but

CIE 1976 UCS recom-

mended in display

metrology specs !

• Problem: Co-ordinate

differences ≠ color

differences (Mac Adam)

• Linear transformation of

Tristimulus values, L = Y

3. co-ordinate : Luminance L = Y





41

LCD CIE 1931 Specification

Plot these tolerances in CIE 1931 with �x and �y = 0.1 !





42

Color Space CIE 1976 UCS 3. co-ordinate : Luminance L = Y

u‘

v‘ • CIE 1976 UCS recom-

mended in display

metrology specs !

• Co-ordinate differences

≈ colour differences

• Linear transformation

• Gamut (100% usually refers to NTSC)





43

TV Color Spaces

• YIQ : NTSC

• YUV : PAL, SECAM

• YCbCr : ITU-R BT.601, 709 HDTV

−

−−=

B

G

R

31.052.021.0

32.028.060.0

11.059.030.0

Q

I

Y

−−

−−=

B

G

R

08.042.050.0

50.033.017.0

11.059.030.0

Cr

Cb

Y

)YR(877.0V

)YB(493.0U

B11.0G59.0R30.0Y

−=

−=

++=

• All parameters are normalized

• Y ≡ Luminance, same formula for all TV color spaces

• IQ, UV, CbCr ≡ Chrominance





44

Color Space Summary

SW∆ESpecs (recomm.)

SpecsUsed for

Device specific

3D, L* ≠ LL not brightness

∆co-cord. ≠ ∆color

(Mac Adams)

Cons

SWJNDs∆co-cord. ≈∆color

historyPros

3D3D2D2DPlot

n. a.NoYesYesLuminance

n. a.Non-linearLinearLinearTristimulus transformation

RGBCIE LabCIE Luv

CIE 1976 UCS

CIE 1931





45

• Summary

• Introduction


Overview

• Common Issues


- Spatial domain:

Uniformity, MTF, gamma,

color tracking, …

- Time domain:

- Short: Flicker, jitter, swim, blur, …

- Medium: Warm up, …

- Long: Lifetime, …

- Ambient light: CR, GS, color, …

- Signal processing

Here: Some examples





46

Uniformity

• Deviation of a display parameter, e.g. luminance within display area

• 5, 9 or 13 spots method (ISO 9241)

%xL

L100

%xL

LL100

%xL

min

max

max

minmax

<•

<−

•

±∅•

Examples*

*:Lmax = 200 cd/m², Lmin = 180 cd/m²

190 cd/m² ± 5%

10%

111%

Definitions

• Area (linear or false color)Uniformity

versus

Campbell-Robson





47

Examples of Uniformity Measurement in Spec

Spot size acc.

FOV and distance

Luminance variations outside this points are not specified

like degradations due to burn-in or image sticking !





48

Color Tracking

Color Tracking 20" LCD, CIE 1976 UCS

0.450

0.455

0.460

0.465

0.470

0.475

0.480

0.202 0.204 0.206 0.208 0.210 0.212

u'

grey

white

v'

Color co-

ordinate of

white depends

here on grey

level !

γγγγ ≠ γγγγ ≠ γγγγ !





49

Contrast Ratio with Ambient Light

Components of reflections

LCD (left) : specular & haze

OLED (right) : mainly specular

(diffuse with low intensity)

Er

)lx0(L

L

)lx0(L

L)lx0(L

L)lx0(LC

L

LC white

reflected

white

reflected

reflectedwhite

Rlightambient

black

white

R

black

π≈≈

+

+=→=

+

Lwhite >> Lreflected

Lreflected >> Lblack

Diffuse

π=

ErLdiffuse

reflected





50

ISO 15008 Sunlight Simulation

30“LCD

1

10

100

1,000

0 20,000 40,000 60,000

Illuminance /lx

Contrast Ratio Diffuse Geometry

Measured CR

Fitted CR

Diffuse or specular geometry





51

Examples for Contrast Ratio Degradation

Luminance of white has more influence on CR with ambient light

than luminance of black and CR under dark room conditions !

Factor 5 for white luminance, L(K) = const. � factor ~ 4.7 in CR for ambient light

110 / 15 = 7205100

510 / 15 = 341005500

110 / 11 = 101001100

510 / 11 = 465001500

CR with LReflected = 10 cd/m² *CR(0 lx)LBlackLWhite

* : LRefl. (W) = LRefl. (K)

Factor 5 for black luminance, L(W) = const. � factor ~1.4 in CR for ambient light

for LWhite = 100 cd/m² and LWhite = 500 cd/m²





52

Ambient Light & Grey Scale

-1.00 -0.75 -0.50 -0.25 0

log (Grey level)

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

-1.25

log (Luminance)

Ambient Light

• Ambient light reduces the number of distinguishable grey shades (JND)

• Grey shades below 80 (of 255) can‘t be resolved for 2,000 lx

0 lx

50 lx

200 lx

1,000 lx

2,000 lx

γ = 2.3

12“ Transmissive LCD

33 %





53

Ambient Light & Color

Reflections shift the

color coordinates

towards the locus

of the light source.

CIE 1931 & Ambient Light

0 0.2 0.4 0.6 0.8 x

y

0.8

0.6

0.4

0.2

0





54

Display Technology vs. Ambient Light : Sunlight Outdoor

Transmissive color AM LCD

Transflective

Color AM LCD

Reflective E-Paper

Reflective MUX LCD

Reflective b/w PM LCD

E-Paperis closeto paper

Display is ON!





Blur Effects

• Spatial Blur

by limited bandwidth, jitter, …

e.g. MTF, analogue path

see ‘Display Metrology’

Luminance

t

FrameT

Blur

• Motion Blur

by hold type

displays (e.g. AM)

Luminance

t

FrameT

Hold Type

55





56

Motion Blur Basics

• Motion blur is caused by AM techniques due to lack of ‚auto-tracking‘

by human vision (PDP has similar issues on subframe coding)

• Impulsive displays like CRTs don’t suffer of motion blur

Adapt AM to impulsive drive

AM

CRT

Visualization Perceived

‚Flashing‘

‚Display & hold‘





57

Display & Observer Motion Blur

Blurry edges !





58

Motion Blur Reduction Techniques

Only with LED backlight !





¾ TFrame

Displaying Moving Objects

Frame 2( T = Frame 1

+ 1/2 Frame 2)

Frame 1

Hold Type

(AM technologies)

Original

Leftover of frame 1not visible due to phosphor decay

(2 pictures ‘movie’)

(Picture 1 iscompletelywritten onthe display)

(Half ofpicture 2 iswritten onthe display)

Non - Hold

Type (CRT)

Smearing !





Effect of Eye Movement on CRTs (Impulsive Drive)

60

White box is moved with 4 pixels per 60 Hz frame

Examined line

Display x

CRTOn Display, x

t

1 F

Eye movement Perceivedimage by eye

On eye, x

t

1 F





Effect of Eye Movement on 60 Hz LCDs (Hold Type)

61

60 Hz LCD

On Display, x

t

1 F


On eye, x

t

1 F

Unsharp edge ≡ blurring of 3 pixels





Effect of Eye Movement on 120 Hz LCDs (Hold Type)

62

120 Hz LCD

On Display, x

t

1 F


On eye, x

t

1 F

Unsharp edge ≡ reduced blurring of 1 pixel





Effect of Eye Movement on Displays

63

White box is moved with 4 pixels per 60 Hz frame

Examined line

Display x

CRTPerceived image by eye

60 Hz LCD

120 Hz LCD

- CRT has best motion picture quality

- LCD with 120 Hz is better than 60 Hz





CRT

Black Frame Insertion

LCD

• High LC switching speed required

• Black frame insertion or impulsive LED backlight

OLED : ‘Easy’

• Fast OLED response

• Only SW required

L

t

1 F

Hold

Lpeak BFI > LHold

BFI

(not to scale)

Black frameinsertion

0 10 20

ITU Grade (International Telecommunication Union)

Excellent

Good

Fair

Poor

Bad

Subjective Evaluation for Moving Picture

Scroll velocity /pixel per frame

CRT

OCBw. LED

TN





Impulsive Backlight for LCD Hold - Type Technologies

Nosmearing

Frame 1 Frame 2

TDisplay

= ½ TFrame

TBlackframe

= ½ TFrame

8.3 ms instead of 16.7 ms

→ fast switching LC required

Writegreyleveldata

todisplay

Writegreyleveldata

todisplay

Backlight OFF OFFON ON

Similar: Scrolling backlight

with LEDs






Could be also made by 120Hz drive with GL = 0 insertion.

Application: Rolling backlight / black frame

66





67


No BFI With BFI






ON

OFF

Scrolling of ‚black‘ backlight sections

68





Motion Blur Reduction by Higher Frame Rate

Motion blur reduction using high frame rate driving: 120Hz/100Hz

Requires new panel design, also video sources low frame rates

(NTSC = 60Hz, PAL = 50Hz, Film = 24Hz)

� Motion interpolated frame technology or Black Frame Insertion needed

such as McFi (Motion Compensated Frame Interpolation)





Comparison by SAMSUNG

BFI





Comparison by SIEMENS

BFI BFI

M. Zachmann (Pforzheim U) et al.

Evaluate your display with PIXPERAN (freeware)





CLEAR MOTION DRIVE by JVC

100 or 120 Hz & interpolated images





Motion Blur Reduction Using 120 Hz & 72 Hz Driving with

Motion - Compensated Frame Interpolation

Movie

24 Hz��

72 Hz

calculated

(DVD)

Motion judder for 3:2 pull-down!

For LCD and PDP

120 Hz

‚cheaper‘

than backlight

methods

NTSC Video

60 Hz��

120 Hz





Frame Rate Conversion Techniques (I)

PAL Video 50 Hz �� Motion blur on Hold type displays (LCD, …)

t

PAL Video 100 Hz repeated �� judder

calculated

PAL Video 100 Hz motion compensated �� no judder (if algorithm OK)





Frame Rate Conversion Techniques (II)

Movie 24 Hz (24p) Original

t

Movie 60 Hz 3:2 pull down repeated �� judder, jerkiness

calculated

Movie 120 Hz motion compensated �� no judder (if algorithm OK)

Movie 72 Hz 3:3 pull down repeated �� judder





PDPs : Motion Artefacts by Sub - Frame Driving

Many motion artifacts etc. of PDPs can be minimized by massive signal processing





77

• Summary

• Introduction


Overview

• Common Issues


- Luminance domain: Loading, halation

- Time domain: Burn-in, differential

ageing, image sticking

- Observer domain:

Spatial & time invariant

- Response time

- Viewing angle: L, CR, GS, color

Here: Some examples





78

LCDs : Response Time Effects

Rel. L

t /ms0 10 20 30

255 � 0

0 � 255

110 � 192

192 � 110

170 � 215

215 � 170

Grey Level

1923170 �� 215

2432110 �� 192

9200 �� 255

TFall /msTRise /msGrey leveltransition

• T > frame time (16.7 ms)

• TRise > TFall

• T = T(grey 1 � grey 2)

Grey level & color shifts

Tambient = 25°C





79

LCD Motion Blur caused by Slow Response Time

Moving Picture Response Time

(MPRT) by Brightness Edge Width

Measurement setup: Camera and

screen (one moving, one fixed)

• Rise time often

≠ fall time

• Response time

depends on

grey level

(start, final)Fall time Rise time

Luminance A - A'

90%

10%

BEWPixel coordinate

Capturedimage

A A'

Motion blur occurs for all AM techno-logies due to vision (Hold type)





80

Motion Blur Measurement Procedures

t

HS

Capturing so that image ‘stands still’

on the camera (chip)

High speed

camera

High speed

sensor,

problem:

t � x





81

MPRT & Perceived Motion Blur (I)





82

MPRT & Perceived Motion BlurMPRT & Perceived Motion Blur (II)





83

Motion Picture Response Time by Brightness Edge Width

Normalising : N-BEW = BEW / moving speed

MPRT = ∅ N-BEW (G2G)





84


MPRT = 16 ms





85


MPRT





86

MPRT Measurements by Grey - to - Grey Response Time

CIE 1976 UCS

6 equidistant

brightness

e.g. L = 0 , 2.2 , 7.7 , 18.4 , 36.2 , 62.8 , 100 cd/m2





87

MPRT Measurements by Grey - to - Grey Response TimeMPRT Measurements by Grey - to - Grey Response Time

Extended Blurred Edge Time





88

Viewing Angle

L, CR , …

Angle

Lambertian (paper)

Emissive displays,diffuse LEDs,standard screen

LCDs, highgain-screenClear LEDs

-80° 0° +80°

‚Angle isn‘t everything‘ !

Measurements : 2D, 3D , value : ± or Σ





89

PM LCD

6:00

Viewing Angle Basics6:00 AM LCD seen from 12:00

displaying

green

⊥⊥⊥⊥

Sensor

Display

2D 3D

Dis play x

y

z

ΦΦΦΦ

θθθθ

0°/ 3°°

9°/ 12°°

180°/ 9°°

270°/ 6°°





90

Contrast Ratio Dependency from Viewing Angle for LCD

32" LCD

0lx, horizontal

0

40

80

120

160

-80 -60 -40 -20 0 20 40 60 80

Viewing Angle /°

CR

Specify viewing angle only with the minimum contrast ratio (or better color difference ∆∆∆∆E)

here : 40°@ CR > 100 : 1 ; 70°@ CR > 50 : 1 ; 125°@ CR > 20 : 1 ; ???°@ CR > 5 : 1

Often CR min > 5 : 1

Thresholddefinition !





91

Example from LCD - Specification

Threshold definition





92

Display A is better because of

• Larger area with nearly constant contrast ratio for perpendicular incidence

• Larger maximum contrast ratio

In both cases a 6:00 observer position with θ ≈ 15°is recommended

Iso - Contrast Plots of AMLCDs

A B

Scale for contrast ratio

AMLCD

17”

60 cm





93

Grey Scale Inversion

Remarks

- If the sign doesn’t change and luminance levels only merge, the image quality

is horrible, but grey scale inversion doesn’t ‘occur’ in meaning of standard (norm)

- Contrast inversion is the extreme case of grey scale inversion, when maximum and

minimum luminance levels change

∆∆∆∆ L = Ldark grey - Lblack

θθθθθθθθGI

L

θθθθGI θθθθ

Grey scale inversion

Visual test pattern





94

L /cd/m²

Grey level (8-bit)

0 31 63

10

0

CR = 200 : 1

ΦΦΦΦ = 90°/ θθθθ = 20°

ΦΦΦΦ = 0°/ θθθθ = 0°

CR = 400 : 1

Contrast Ratio values are misleading here because a reduction of

‘only’ 2 occurs but the grey level representation is completely

vanished (flat curve, blue) compared to perpendicular incidence

(OK, brown) � no grey shades visible for 20° off !

CR = 400 : 1

CR = 200 : 1

Contrast Ratio vs. Grey Scale Performance





95

Color Dependency from Viewing Angle of LCDs

Measured color representation,

black was shown on the screen !

Visual test pattern

Inversion !





96

Colour Wash Out

0° 45° 60°

Electro-optical curve changes

with viewing angle!





97

Luminance Domain : Loading of Plasma Panels

Luminance of

centered white

box depends

on their size,

this is called

‘loading’.

Why? Power limitation

This can be also

observed for CRTs

(incl. image

size variations).





98

Aging of Displays

• Lifetime (50%)

Full screen white measured

Static content like on airport

information displays can cause

burn-in and image sticking

• Differential Aging

Different lifetimes of

color subpixel → color shift

rel. L

t

1

t

L

L

100

50

TLTTLT

No inital drop

InitaldropNote: Life time measured at ~ 75°C,

and extrapolated to 25°C in specs!

Temperature ↑ → Life time ↓





99

Burn - In of Emissive Displays and LCD Image Sticking

CRT

PDP

LCD

Several hours

display dark grey





100

Burn - In and LCD Image Sticking Measurement

- T = 0 : Display 5 x 5 (black & white) checkerboard and mark 3 boxes (2 white, 1 black)

- Measure ‘initial’ luminance for the 3 boxes for black and white: LWL, LWC, … LBL, … LBR

- Burn-in display when showing the checkerboard, if applicable

with high temperature for speeding up the effect, e.g. for OLEDs

- Wait x hours

- Measure luminance of the same locations for full white (KWL, KWC, KWR)

- Measure luminance of the same locations for full black (KBL, KBC, KBR)

- Calculate residual image factors by

R’s are greater than 1 because of aged luminance ‘K’ is lower than initial luminance ‘L’

Simpler test:

+−=−

)x(L2

)x(L)x(L1100(%)inBurn

WC

WRWL

- Checkerboard as burn-in- White screen as test pattern after x hours

IS:Test at

grey(60/255)





101

• Summary

• Introduction


Overview

• Common Issues






102

Parameters Affecting Measurements & Visual Perception

- Temporal ~

- Directional variations

- Lateral ~

- Photometric

- Colorimetric

- Resolution

‘Signal

processing’





103

Example of Optical Specification for AM LCD

Inverter





104

Overview of Standards

Parameter Standard Display

Luminance CIE 18,15.2

IEC 47(CO)16

IEC 61747*

All

LCD

Chromaticity

CECC 20000 A3

IEC 47(CO)16

ISO 9241/3

ISO 13406

IEC 61747*

LCD

LCD

CRT

FPD

Luminance and

chromaticity uniformity

ISO 9241/3

ISO 13406

CECC WG 20B

IEC 61747*

CRT

FPD

LCD

Response time

ISO 13406

CECC 20000 A3

IEC 47(CO)16

IEC 61747*

FPD

LCD

LCD

Reflections

ISO 13406

CECC 20000 A3

IEC 47(CO)16

ISO 9241/7

IEC 61747*

FPD

LCD

LCD

CRT

Electro-optical Transfer EBUTech 3273 CRT, LCD

Resolution CECC11000 all

Crosstalk CECC WG 20B

ISO 13406

IEC 61747*

LCD

FPD

Distortion ISO 9241/3 CRT

Viewing direction

CECC 20000 A3

IEC 47(CO)16

ISO 13406

LCD

LCD

FPD

Parameter Standard Display

* : for LCD matrix displays

Common: VESA FPDM, SPWG, TCO

Documents

mes displays introduction metrologyeitidaten.fh-pforzheim.de/.../mes_displays_introduction_metrology.pdf · MES Multimedia - Displays: Introduction Blankenbach / Pforzheim Univ