Webinar: Reproducible Display
Sparkle Measurements
TechnoTeam Bildverarbeitung GmbH,
Werner-von-Siemens-Str. 5, 98693, Ilmenau, Germany
Elektrobit Automotive GmbH,
Lise-Meitner-Straße 10, 89081, Ulm, Germany
Volkswagen AG,
38436, Wolfsburg, Germany
Ingo Rotscholl, Development Engineer, PhD
• PhD in 2017 in the field of photometry at the Light Technology
Institute (LTI) of Karlsruhe Institute of Technology (KIT)
• Development engineer for display metrology at TechnoTeam
Bildverarbeitung GmbH since 2018
• Several publications on display metrology including the topics
uniformity, sticking images, AR/VR and automotive displays
• Member in national and international standardization
organizations such as IEC, ICDM, DKE and VDI
About the speaker
Table of contents
• Measuring sparkle fundamentals
– Introduction
– Separation of sparkle
– Reproducibility
• Measurement setup
– Setup problem 1: Initial focus position
– Setup problem 2: Dust, defects ...
– Setup problem 3: Reproduction scale
– Setup problem 4: Measurement field angle
• Conclusions, summary and Q/A
Table of contents
• Measuring sparkle fundamentals
– Introduction
– Separation of sparkle
– Reproducibility
• Measurement setup
– Setup problem 1: Initial focus position
– Setup problem 2: Dust, defects ...
– Setup problem 3: Reproduction scale
– Setup problem 4: Measurement field angle
• Conclusions, summary and Q/A
Introduction: Sparkle and high quality displays
Self emissive display
▪ Anti Glare Layer (AGL) enhance contrast and readability in direct
lighting environments (e.g. sun)
▪ Anti Glare Layer may blur image (pixel cross talk)
▪ Anti Glare Layer may lead to high frequency non-uniformity (sparkle)
▪ Not yet standardized (in progress)
▪ Reproducibility is a main issue
Introduction: Sparkle and high quality displays
▪ BlackMURA compliant setup
▪ Measurement without removing AGL
Sparkle measurements: TechnoTeam conditions:
Separation of sparkle
• Influence of periodic pixel structure
Bare pixel matrix Pixel matrix with sparkle Sparkle without pixel matrix
Separation of sparkle
Known methods [2]
• De-focus [3,4]
• Filter in spatial
domain [1,5]
• Filter in frequency
domain [2,6]
• Undersampling [7,8]
Pixel matrix with sparkle
• Separation of periodic pixel structure from sparkle in luminance picture
Sparkle without pixel matrix
Separation of sparkle
Known methods [2]
• De-focus [3,4]
• Filter in spatial
domain [1,5]
• Filter in frequency
domain [2,6]
• Undersampling [7,8]
Pixel matrix with sparkle
• Separation of periodic pixel structure from sparkle in luminance picture
Sparkle without pixel matrixReproducibility
issues
Separation of sparkle
Known methods [2]
• De-focus [3,4]
• Filter in spatial
domain [1,5]
• Filter in frequency
domain [2,6]
• Undersampling [7,8]
Pixel matrix with sparkle
• Separation of periodic pixel structure from sparkle in luminance picture
Sparkle without pixel matrixBlackMURA
setup issue(depends)
Separation of sparkle
Known methods [2]
• De-focus [3,4]
• Filter in spatial
domain [1,5]
• Filter in frequency
domain [2,6]
• Undersampling [7,8]
Pixel matrix with sparkle
• Separation of periodic pixel structure from sparkle in luminance picture
Sparkle without pixel matrixOK
Filter in frequency domain
Spatial domain
Spatial domain Amplitudes (FFT)
Filter in frequency domain
Filtered imageFrequency filter
Spatial domain Amplitudes (FFT)
Filter in frequency domain
𝑆𝑝𝑎𝑟𝑘𝑙𝑒 =𝑠𝑡𝑑 𝐿
𝑚𝑒𝑎𝑛 𝐿
Verification of method
• Verification in one reference setting
• Replacement of AG layers with different perceived sparkle
noglass
L1 L2 M1 M2 M3 M4 M5 M6 H1 H2 H3 H4
0%
2%
4%
6%
8%
10%
12%
14%
16%
Sp
ark
le
Expert rating
Display 1 (224ppi) and 12 AGL + (no glass)
Measurement procedure
Alignment according to BlackMURA
Original luminance image
Focus setting in pixel plane (individual pixels)
Filtered luminance image
𝑆𝑝𝑎𝑟𝑘𝑙𝑒 =𝑠𝑡𝑑 𝐿
𝑚𝑒𝑎𝑛 𝐿
Camera Lens Glass
1MP 25mm no glass, L1, L2, M2, M6, H1, H3
50mm no glass, L1, L2, M2, M6, H1, H3
5MP 25mm no glass, L1, L2, M6, H1, H3
50mm no glass, L1, L2, M2, M6, H1, H3
12MP 16mm no glass, L1, L2, M2, M6, H1, H3
25mm no glass, L1, L2, M2, M6, H1, H3
50mm no glass, L1, L2, M1, M2, M3, M4, M5, M6,
H1, H2, H3, H4
5MP* 25mm no glass, L1, L2, M1, M3, M4, M5, H3, H4
Reproducibility
* Different camera
Reproducibility
noglass
L1 L2 M2 M6 H1 H3
0%
2%
4%
6%
8%
10%
12%
14%
Sp
ark
le
16mm 12 MP
25mm 1MP
25mm 5MP
25mm 12MP
50mm 1MP
50mm 5MP
50mm 12MP
Reproducibility
Glass/
Method
No
Glass
L1 L2 M2 M6 H1 H3
CV, direct
measurement25,3% 8,7% 5,8% 8,4% 8,7% 9,7% 8,4%
CV =𝑠𝑡𝑑 𝑆𝑝𝑎𝑟𝑘𝑙𝑒
𝑚𝑒𝑎𝑛 (𝑆𝑝𝑎𝑟𝑘𝑙𝑒)
Measure for relative error:
Measurement setupSetup problem 1: Initial focus position
Focus reproducibility / Depth of focus
AG layer
Pixel layer
Focus reproducibility / Depth of focus
Glass M6
Focus reproducibility / Depth of focus
Glass M6
Sparkle = Maximum
(Optimized focus)
Sparkle = Sparkle(0)
(Initial focus)
Focus reproducibility / Depth of focus
Pix
el la
yer
AG
layer
Depth of focus Circle of confusion is smaller
than sensor pixel size
Size of
sensor pixel
Focus reproducibility / Depth of focus
Pix
el la
yer
AG
layer
Depth of focus Circle of confusion is smaller
than sensor pixel size
• Limitation of focus reproducibility
• Where is the “sparkle plane” Size of
sensor pixel
Focus reproducibility / Depth of focus
Glass M6 Pix
el la
ye
r
AG
laye
r
Depth of focus
Depth of focus
„Sparkle“ plane
Precision/Uncertainty
of manual/auto focus
noglass
L1 L2 M2 M6 H1 H3
0%
2%
4%
6%
8%
10%
12%
14%
Sp
ark
le
Optimized focus
16mm 12MP
25mm 5MP*
25mm 1MP
25mm 5MP
25mm 12MP
50mm 1MP
50mm 5MP
50mm 12MP
Reproducibility with distance focus scan
Reproducibility experiments overview
Glass/
Method
No
Glass
L1 L2 M2 M6 H1 H3
CV, direct
measurement25,3% 8,7% 5,8% 8,4% 8,7% 9,7% 8,4%
CV, optimized
focus18,9% 10,1% 8,6% 3,3% 4,4% 5,3% 4,3%
CV =𝑠𝑡𝑑 𝑆𝑝𝑎𝑟𝑘𝑙𝑒
𝑚𝑒𝑎𝑛 (𝑆𝑝𝑎𝑟𝑘𝑙𝑒)
Measurement setupSetup problem 2: Handling issues
„local“ Camerapixels• Dust, finger prints
• Defects, markers 𝑆𝑝𝑎𝑟𝑘𝑙𝑒𝑙𝑜𝑐𝑎𝑙 =𝑠𝑡𝑑 𝐿𝑙𝑜𝑐𝑎𝑙𝑚𝑒𝑎𝑛 𝐿𝑙𝑜𝑐𝑎𝑙
Handling issues
Filtered image
Handling issues
Imperfections affect standard deviation
• Dust, finger prints
• Defects, markers
Filtered image Local standard deviation matrix
→“Sparkle” matrix
𝑆𝑝𝑎𝑟𝑘𝑙𝑒 = 𝑚𝑒𝑑𝑖𝑎𝑛(𝑆𝑝𝑎𝑟𝑘𝑙𝑒𝑀𝑎𝑡𝑟𝑖𝑥)
Median of sparkle matrix statistically robust
against outliers caused by tiny imperfections
noglass
L1 L2 M2 M6 H1 H3
0%
2%
4%
6%
8%
10%
12%
14%
Sp
ark
le
Optimized focus, local evaluation
16mm_12MP
25mm 5MP*
25mm_1MP
25mm,5MP
25mm,12MP
50mm_1MP
50mm,5MP
50mm,12MP
Reproducibility with distance focus scan and local
evaluation
Reproducibility experiments summary
Glass/
Method
No
Glass
L1 L2 M2 M6 H1 H3
CV, Direct
Measurement25,3% 8,7% 5,8% 8,4% 8,7% 9,7% 8,4%
CV, Optimized
focus18,9% 10,1% 8,6% 3,3% 4,4% 5,3% 4,3%
CV, Local,
optimized focus4,1% 4,1% 4,0% 4,6% 2,8% 5,2% 4,2%
CV =𝑠𝑡𝑑 𝑆𝑝𝑎𝑟𝑘𝑙𝑒
𝑀𝑊 (𝑆𝑝𝑎𝑟𝑘𝑙𝑒)Optimization of reproducibility
Reproducibility experiments summary
Glass/
Method
No
Glass
L1 L2 M2 M6 H1 H3
CV, Direct
Measurement25,3% 8,7% 5,8% 8,4% 8,7% 9,7% 8,4%
CV, Optimized
focus18,9% 10,1% 8,6% 3,3% 4,4% 5,3% 4,3%
CV, Local,
optimized focus4,1% 4,1% 4,0% 4,6% 2,8% 5,2% 4,2%
CV =𝑠𝑡𝑑 𝑆𝑝𝑎𝑟𝑘𝑙𝑒
𝑀𝑊 (𝑆𝑝𝑎𝑟𝑘𝑙𝑒)Optimization of reproducibility
Measurement setupSetup problem 3: Reproduction Scale
• Higher RPS → higher sparkle value and higher focus sensitivity
• Depth of focus depends on lens/measurement distance
Reproduction scale
• Higher RPS → Lower measurement distance with same lens
• Lower measurement distance → Lower depth of focus
Reproduction scale
Reproduction scale
Glass/RPS No
Glass
L1 L2 M2 M6 H1 H3
RPS=3.6 10,25% 6,68% 6,89% 11,13% 6,00% 2,60% 4,61%
RPS=3.0 8,00% 3,80% 3,54% 6,63% 3,24% 2,64% 2,13%
RPS=2.45 4,05% 4,13% 4,04% 4,63% 2,77% 5,17% 4,24%
RPS=2.1 5,66% 4,11% 5,63% 2,38% 4,29% 6,05% 5,24%
• Sensitivity of RPS→ lower RPS more stable
• Sensitivity of RPS→ lower RPS more stable
Reproduction scale
Glass/RPS No
Glass
L1 L2 M2 M6 H1 H3
RPS=3.6 10,25% 6,68% 6,89% 11,13% 6,00% 2,60% 4,61%
RPS=3.0 8,00% 3,80% 3,54% 6,63% 3,24% 2,64% 2,13%
RPS=2.45 4,05% 4,13% 4,04% 4,63% 2,77% 5,17% 4,24%
RPS=2.1 5,66% 4,11% 5,63% 2,38% 4,29% 6,05% 5,24%
Measurement setupSetup problem 4: Measurement field angle
Measurement field angle
𝜗D
d
𝜗𝐻
𝜗𝑉
→“Sparkle” matrix
Measurement field angle
→“Sparkle” matrix
Sparkle increases with increasing field angle
𝜗𝐻
𝜗𝑉
0,0%
2,0%
4,0%
6,0%
8,0%
10,0%
no glass L1 L2 M2 M6 H1 H3
16mm 12MP RPS=2.1
ϑMax=26° ϑMax=14°
ϑMax=7° ϑMax=3°
0,0%
2,0%
4,0%
6,0%
8,0%
10,0%
no glass L1 L2 M2 M6 H1 H3
16mm 12MP RPS=2.1
ϑMax=26° ϑMax=14°
ϑMax=7° ϑMax=3°
Measurement field angle
→“Sparkle” matrix
Sparkle increases with increasing field angle
𝜗𝐻
𝜗𝑉
Measurement setup
• Linear stage
• Vertical/Horizontal alignment
• Low cost solution
• LabSoft Integration
LMK Motor AddOn
• High speed and
high precision alignment
• Enables measuring a large
data base as foundation
for a specification
• Enables sensitivity studies
Measurement setup
Setup Camera Lens RPS1 (Distance) Glass
1-4 1MP 25mm 2,1; 2,45; 3,0; 3,6 no glass, L1, L2, M2, M6, H1, H3
5-8 50mm 2,1; 2,45; 3,0; 3,6 no glass, L1, L2, M2, M6, H1, H3
9-12 5MP 25mm 2,1; 2,45; 3,0; 3,6 no glass, L1, L2, M6, H1, H3
13-16 50mm 2,1; 2,45; 3,0; 3,6 no glass, L1, L2, M2, M6, H1, H3
17-20 12MP 16mm 2,1; 2,45; 3,0; 3,6 no glass, L1, L2, M2, M6, H1, H3
21-24 25mm 2,1; 2,45; 3,0; 3,6 no glass, L1, L2, M2, M6, H1, H3
25-28 50mm 2,1; 2,45; 3,0; 3,6 no glass, L1, L2, M1, M2, M3, M4, M5,
M6, H1, H2, H3, H4
29-32 5MP* 25mm 2,1; 2,45; 3,0; 3,6 no glass, L1, L2, M1, M3, M4, M5, H3,
H4
* Different camera
Data base for specification
Setup Camera Lens RPS1 (Distance) Glass
1-4 1MP 25mm 2,1; 2,45; 3,0; 3,6 no glass, L1, L2, M2, M6, H1, H3
5-8 50mm 2,1; 2,45; 3,0; 3,6 no glass, L1, L2, M2, M6, H1, H3
9-12 5MP 25mm 2,1; 2,45; 3,0; 3,6 no glass, L1, L2, M6, H1, H3
13-16 50mm 2,1; 2,45; 3,0; 3,6 no glass, L1, L2, M2, M6, H1, H3
17-20 12MP 16mm 2,1; 2,45; 3,0; 3,6 no glass, L1, L2, M2, M6, H1, H3
21-24 25mm 2,1; 2,45; 3,0; 3,6 no glass, L1, L2, M2, M6, H1, H3
25-28 50mm 2,1; 2,45; 3,0; 3,6 no glass, L1, L2, M1, M2, M3, M4, M5,
M6, H1, H2, H3, H4
29-32 5MP* 25mm 2,1; 2,45; 3,0; 3,6 no glass, L1, L2, M1, M3, M4, M5, H3,
H4
* Different camera
Data base for specification
Reproducibility experiment II
NoGlass
L1 L2 M4 M1 M3 M5 H3 H4
0%
2%
4%
6%
8%
10%
12%
14%
16%
18%
Sp
ark
le
25mm 1MP
50mm 1MP
25mm 5 MP
50mm 5MP
16mm 12MP
25mm 12MP
50mm 12MP
Display 2 (183 ppi)
CV 2,8% 4,8% 2,4% 2,8% 2,6% 2,7% 1,7% 2,7% 1,8%
Conclusions and summary
Conclusions and summary
• Development of reproducible sparkle measurement specification
(Based on more then 10.000 individual luminance images)
• Reproducibility optimization:
→ Focus/Sparkle scan → To avoid blurring of high/medium sparkle valuesA
G la
yer
Pix
ella
yer
Conclusions and summary
• Development of reproducible sparkle measurement specification
(Based on more then 10.000 individual luminance images)
• Reproducibility optimization:
→ Focus/Sparkle scan → To avoid blurring of high/medium sparkle values
→ Local evaluation → lTo avoid impact of tiny imperfections on low sparkle values
Sparkle matrix
Median
Conclusions and summary
• Development of reproducible sparkle measurement specification
(Based on more then 10.000 individual luminance images)
• Reproducibility optimization:
→ Focus/Sparkle scan → To avoid blurring of high/medium sparkle values
→ Local evaluation → lTo avoid impact of tiny imperfections on low sparkle values
→ Distance/Lens/Camera flexibility enables BlackMURA compliant setup
𝑆𝑝𝑎𝑟𝑘𝑙𝑒 = 8% ± 4% ≈ ± $900,000
Factor Reproduction Scale Field Angle
Influence ++ +
Specification Fixed Value Boundary
• Development of reproducible sparkle measurement specification
(Based on more then 10.000 individual luminance images)
• Reproducibility optimization:
→ Focus/Sparkle scan → To avoid blurring of high/medium sparkle values
→ Local evaluation → lTo avoid impact of tiny imperfections on low sparkle values
→ Distance/Lens/Camera flexibility enables BlackMURA compliant setupPlease contact
us for more
information
Conclusions and summary
𝑆𝑝𝑎𝑟𝑘𝑙𝑒 = 8% ± 1% ≈ ± $50,000
Factor Reproduction Scale Field Angle
Influence ++ +
Specification Fixed Value Boundary
List of references
[1] M. E. Becker, J. Soc. Inf. Disp. 23, p.474 (2015)
[2] M. E. Becker, SID Symposium Digest of Technical Papers. Vol. 49. No. 1. (2018)
[3] M. Scholz, electronic displays Conference (2018)
[4] V. F. Paz, SID Symposium Digest of Technical Papers. Vol. 49. No. 1. (2018)
[5] J. Gollier, SID Symposium Digest of Technical Papers. Vol. 44. No. 1 (2013)
[6] T.W. Hsu, International Display Workshop. (2014)
[7] M. Hayashi, International Display Workshop. (2017)
[8] M. Kurashige, International Display Workshop. (2019)
[9] M. Isshiki, SID Symposium Digest of Technical Papers. Vol. 50. No. 1. (2019)
Thank you for your attention!
Contact: Dr.-Ing. Udo Krüger,
Dr.-Ing. Ingo Rotscholl
Julia Brinkmann
TechnoTeam Bildverarbeitung GmbH
Dr. Christoph Rickers
Volkswagen AG
Jens Rasmussen
Elektrobit Automotive GmbH
Thank you for your attention!
Contact: Dr.-Ing. Udo Krüger,
Dr.-Ing. Ingo Rotscholl
TechnoTeam Bildverarbeitung GmbH
W.-v.-Siemens-Str. 5
D-98693 Ilmenau
www.technoteam.de
Top Related