METHODS FOR MEASURING SMALL DEFECTS IN ......2019/12/17 · Flexible display concepts from Flexenable that are designed to match the dimensionality of the A-pillar (left) and door

Radiant Vision Systems | A Konica Minolta Company

Radiant Vision Systems | A Konica Minolta CompanyPresented by Chris Williamson | December 17, 2019

METHODS FOR MEASURING SMALL DEFECTS IN CURVED DISPLAYS: EVALUATING APPROACHES AND SYSTEM SPECIFICATIONS

Global SupportAutomated Visual InspectionLight & Color

3Radiant Vision Systems | A Konica Minolta Company

© Radiant Vision Systems, LLC. Confidential Information.

TODAY’S AGENDA

• Curved Display Landscape

• Challenges of Visual Performance Testing

• Image Processing

• Detecting Small Defects: Lines & Pixels

• Evaluating Test Methods

• Single-Image/Single-Analysis

• Single-Image/Multi-Analysis

• Multi-Image

• Results: Method & System Impact on Data Accuracy

• Recommended Methods & Systems

• For Design & Characterization in the Lab

• For Qualification Throughout Production



BREAKING FREE FROM FLAT PANELS

• Displays are acquiring

more real estate within

the vehicle

• Rectangular, flat panel

displays restrict

integration area

• New display shapes

enable organic design

• Free-form displays

• Flexible & curved displaysFree-form display in speedometer region of Audi 2019 TT Coupe. (Source: Audi USA)



GOALS FOR A MORE FLEXIBLE FUTURE

Flexible display concepts from Flexenable that are designed to match the dimensionality of the A-pillar (left) and door frame (right) for seamless, space-saving integration. (Source: Flexenable, n.d.)



BENEFITS OF CURVED DISPLAYS

• Concave horizontal radius of curvature up to 1000mm (1000R):

• Closely matches curvature of human peripheral vision

• Reduces visual fatigue

• Reduces eye movement

Field of Vision

Peripheral Peripheral

120°

60°

Display

1000R





• Limits blurring of elements at the display edges

• Improves visual immersion

Blurred at Edges

Blurred at Edges

Flat Panel Display





• Limits blurring of elements at the display edges

• Improves visual immersion

Display

1000R

Limitedblurring

Limitedblurring



TODAY’S CURVED INTEGRATIONS

A curved instrument panel display by Bosch (1500R) manufactured for the Volkswagen Touareg, shown inside (left) and outside of the vehicle (right). (Source: Bosch, 2018)

Edge Pixel

Center Pixel

CHALLENGES OF VISUAL PERFORMANCE TESTING

Effects of Curvature on Small Display Defects



EFFECTS OF CURVATURE: ALIGNMENT

Before

AfterRegister Active Display Area

(RADA)

Curved Display Measurement



EFFECTS OF CURVATURE: MOIRÉ

Before

AfterAutomatic Moiré Removal

Moiré Removed(pixel defect now visible)

Aliasing effects obscure defects

Curved Display Measurement



EFFECTS OF CURVATURE: LINE DEFECTS

Edge Center



EFFECTS OF CURVATURE: PIXEL DEFECTS

Edge Center



HOW DO WE LIMIT THESE EFFECTS?

• Adjust measurement setup:

• Angle of measurement system relative to display

• Number of images captured

Expected Benefits:

– Reduce distortion & focus issues across display

Left Image Right Image




• Adjust analysis setup:

• Number of analysis areas

Expected Benefits:

– Improve defect contrast based on local luminance values

Area 1 Area 2 Area 3




• Adjust system specifications:

• Resolution

• Depth of Field settings(lens F-stop)

Expected Benefits:

– Improve defect clarity

– Bring all defects into focus at once Left Edge Right Edge

Missed Defects Missed Defects



FALSE DEFECTS

Increasing resolution and DOF can increase detection of false defects(dust particles and debris).

Pixel #1

Pixel #2

Pixel #3




• Adjust thresholds to isolate defects:

• Minimum defect contrast

• Minimum defects size(sensor pixels)

Expected Benefits:

– Accurately identify defects

– Reduce false defects

Center Edge

Line DefectContrast: 10

Line Defect Contrast: 6.5

EVALUATING TEST METHODSLab-Based Study of Approaches for Curved Display Measurement



DEFINING A METHOD FOR CURVED DISPLAYS

Radiant evaluated 3 methods:

• Method 1: Single-Image/Single-Analysis

• Method 2: Single-Image/Multi-Analysis

• Method 3: Multi-Image

Each method was evaluated using 3 systems with these specs:

• Resolutions: 2, 8, 16 megapixels

• DOF: F/2.8, F/8, F/13 settings

F/13F/13

Method

2MP 8MP 16MP

F/13



RADIANT TEST SETUP

ProMetric® I Imaging Colorimeter (2, 8, 16MP) Mounted on tripod

Curved display (1500R)

Dark test lab



METHOD 1: SINGLE-IMAGE/SINGLE-ANALYSIS

Expected Benefits

• Enables holistic evaluation

• Limits measurement time

• Limits equipment

Expected Disadvantages

• Small defects may be distorted or

out of focus on edges

• View angle effects may reduce

measurement accuracy

Single Image Single Analysis



METHOD 2: SINGLE-IMAGE/MULTI-ANALYSIS

Expected Benefits

• Same as Method 1

• Improves defect contrast threshold

based on local area luminance


• Same as Method 1


Single Image Multiple Analyses



METHOD 3: MULTI-IMAGE

Expected Benefits

• Limits view angle and focus changes

• Increases effective resolution

(½ area measured at once)

• Enables testing larger displays or

larger curvature in smaller space


• May require add’l equipment

• Rotation may limit accuracy

• Rotation extends measurement time

Multiple Images Multiple Analyses

Left

Right Right

Left

RESULTS OF TESTINGEffect of Measurement Method & System on Data Accuracy



NOTES ON MEASUREMENT VALUES

• Horizontal Line Defects:

• High contrast % improves accuracy and repeatability of defect detection

• Vertical Line Defects:

• Same as Horizontal Line Defects

• Pixel Defects:

• High contrast % improves accuracy and repeatability of defect detection

• More sensor pixels per defect improves thresholding precision (reducing false defects)

Test Images (example)



RESULTS: HORIZONTAL LINE DEFECTS

Contrast Percentage (%)

Method 1 Method 2 Method 3

Whole Display

Center Channel

Edge Channel

Left Image

Right Image

2MP

F/2.8 4.5 10 6.5 20 10

F/8 11.5 12 12.5 20 15

F/13 10.5 11 10.5 20 20

8MP

F/2.8 13.5 14.5 13 20 10

F/8 29.5 31.5 28.5 30 35

F/13 30 30 30 35 35

16MP

F/2.8 13.5 14.5 14 15 15

F/8 35 39 36 40 40

F/13 27 31.5 26.5 40 40



RESULTS: VERTICAL LINE DEFECTS

Contrast Percentage (%)


Whole Display

Center Channel

Edge Channel

Left Image

Right Image

2MP

F/2.8 8.5 15 8.5 15 10

F/8 17 17.55 17 20 20

F/13 15 16 15 20 20

8MP

F/2.8 8.5 25 8.5 25 15

F/8 32.5 36.5 32 45 45

F/13 31.5 33 30.5 45 40

16MP

F/2.8 10.5 29 11 25 15

F/8 43 54 41.5 50 55

F/13 36 39.5 35.5 55 55



RESULTS: PIXEL DEFECTS - VALUES

Contrast Percentage (%) / CCD Pixel Size


Whole Display

Center Channel

Edge Channel

Left Image

Right Image

2MP

F/2.8 2 / 1 3 / 1 2 / 2 3 / 3 2 / 3

F/8 3 / 5 3.5 / 1 3.5 / 2 5.5 / 5 5 / 5

F/13 3 / 4 3.5 / 1 3.5 / 1 5.5 / 5 5.5 / 5

8MP

F/2.8 4 / 5 6 / 9 3 / 5 6.5 / 8 5 / 9

F/8 8 / 8 10 / 5 8 / 5 12 / 9 12 / 10

F/13 11 / 5 11 / 5 11 / 5 13 / 9 13 / 10

16MP

F/2.8 5 / 9 11 / 6 5 / 5 10 / 9 7 / 12

F/8 15 / 8 15 / 9 15 / 7 17 / 10 15 / 10

F/13 15 / 5 15 / 5 15 / 5 20 / 10 17 / 10



RESULTS: PIXEL DEFECTS - ACCURACY

False / MissedDefects


Whole Display

Center Channel

Edge Channel

Left Image

Right Image

2MP

F/2.8 11 / 1 1 / 1 0 / 1 2 / 0 10 / 0

F/8 0 / 0 1 / 0 0 / 0 1 / 0 0 / 0

F/13 0 / 0 0 / 0 0 / 0 0 / 0 0 / 0

8MP

F/2.8 8 / 1 1 / 0 0 / 0 1 / 0 3 / 0

F/8 1 / 0 0 / 0 0 / 0 0 / 0 0 / 0

F/13 0 / 0 0 / 0 0 / 0 0 / 0 0 / 0

16MP

F/2.8 9 / 0 1 / 0 0 / 0 0 / 0 1 / 0

F/8 1 / 0 0 / 0 0 / 0 0 / 0 1 / 0

F/13 0 / 0 0 / 0 0 / 0 0 / 0 0 / 0

RECOMMENDED METHOD & SYSTEMOptimizing Efficiency and Accuracy from Lab to Production



OVERALL DETERMINATIONS

• Measurement improved most significantly by:

• High Resolution (baseline 16MP)

• High DOF setting (baseline F/8)

• Measuring normal to the display (Method 3: Multi-Image Method)

16MP

F/8



FOR LAB DESIGN & CHARACTERIZATION

Recommended:


Ideal When…

✓ Accuracy is paramount

✓ Space accommodates equipment

✓ Application accommodates lengthier setup time



FOR LAB DESIGN & CHARACTERIZATION

Recommended:


Ideal When…

✓ Accuracy is paramount

✓ Space accommodates equipment

✓ Application accommodates lengthier setup time

100%Accuracy

MeasurementEfficiency



FOR PRODUCTION QUALIFICATION

Recommended:

• Method 2: Single-Image/ Multi-Analysis

Ideal When…

✓ Time & efficiency are paramount

✓ Accuracy can be achieved using:

1. Robust system

2. Local thresholding via multipleanalysis regions




FOR PRODUCTION QUALIFICATION

Recommended:

• Method 2: Single-Image/ Multi-Analysis

Ideal When…

✓ Time & efficiency are paramount

✓ Accuracy can be achieved using:

1. Robust system

2. Local thresholding via multipleanalysis regions

MeasurementEfficiency

100%Accuracy



SUMMARY

✓ An adaptation of current display test methods may be all that is needed to ensure accurate defect detection across curved displays

✓ In lab settings, a multi-image approach optimizes accuracy

✓ In production settings, a multi-channel approach with a robust system offers accuracy with reduced time and complexity



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METHODS FOR MEASURING SMALL DEFECTS IN ......2019/12/17 · Flexible display concepts from Flexenable that are designed to match the dimensionality of the A-pillar (left) and door