DEFINING A SPARKLE MEASUREMENT STANDARD FOR QUALITY CONTROL OF ANTI-GLARE DISPLAYS Presented By Matt Scholz April 3, 2018
Light & Color Automated Visual Inspection Global Support
TODAY S AGENDA Anti-Glare Displays Background and Application Effect of Sparkle on Display Quality Measuring Sparkle: Considerations Creating a Standard Measurement Method System Specifications Measurement Setup Software Testing Defining Tolerances based on Human Perception Customer Success Story 3
ANTI-GLARE DISPLAYS BACKGROUND AND EFFECT ON VISUAL DISPLAY QUALITY 4
VIEWING DISPLAYS IN AMBIENT LIGHT 5
VIEWING DISPLAYS IN AMBIENT LIGHT 6
SOLUTION: ANTI-GLARE 7
ANTI-GLARE DISADVANTAGE LCD without AG LCD with AG 8
ANTI-GLARE DISADVANTAGE Anti-Glare Microstructure Nuijs, Horikx, Applied Optics 33,18 (1994) p.4058 LCD with AG 9
ANTI-GLARE DISADVANTAGE LCD with AG 10
OPTIMIZING THE AG LAYER Evenly-diffused Sunlight Sparkle 11
MEASURING SPARKLE Pixel-level luminance variation calculated using standard deviation (σ) of a population Measured as a % deviation across a region or averaged for multiple regions (ROI) 11 12 13 12
MEASUREMENT CONSIDERATIONS ADVANTAGES FOR ACHIEVING DATA REPEATABILITY 13
OBJECTIVES FOR EVALUATION 1. Effective display characterization Define measurement system Define measurement setup Isolate sparkle Reduce effects of other display anomalies 2. Evaluation based on human perception Perform initial human evaluation Correlate system measurements with human rankings 14
1. EFFECTIVE DISPLAY CHARACTERIZATION Reduce effects of display gradient 15
1. EFFECTIVE DISPLAY CHARACTERIZATION Reduce effects of display gradient 16
1. EFFECTIVE DISPLAY CHARACTERIZATION Register active display area (RADA) 17
1. EFFECTIVE DISPLAY CHARACTERIZATION Reduce other display anomalies 18
1. EFFECTIVE DISPLAY CHARACTERIZATION Color Variation (if required) CIE-matched tristimulus color filters Color calibration 19
2. EVALUATION BASED ON HUMAN PERCEPTION Define Tolerance Using Several Participants 10 20
2. EVALUATION BASED ON HUMAN PERCEPTION Define Tolerance Using Several Participants 10 8 9 10 10 9 21
2. EVALUATION BASED ON HUMAN PERCEPTION Define Tolerance Case by Case Customer A Suppliers X, Y, Z 22
CREATING A STANDARD METHOD HOW TO ACHIEVE REPEATABLE SPARKLE MEASUREMENT FOR AG DISPLAYS 23
SYSTEM SPECIFICATIONS ProMetric Camera: I-series imaging colorimeter Y-series imaging photometer High resolution (to 29MP) 61 db dynamic range Per pixel, 1x1 binning Thermoelectrically-cooled sensors High SNR Factory calibration 50mm electronically-controlled lens 24
SYSTEM SPECIFICATIONS TrueTest Software Data acquisition & analysis Test sequencing RADA Gradient filter Blob removal 25
HOW TO SET UP THE MEASUREMENT 1. To ensure stability, use breadboard and lock down the display and camera. 26
HOW TO SET UP THE MEASUREMENT 2. Measure to the location where grey meets black on both sides of the camera (CCD plane). CCD Plane 27
HOW TO SET UP THE MEASUREMENT 3. The distance from side to side should be equal to ensure the camera and the display are parallel. CCD Plane 28
HOW TO SET UP THE MEASUREMENT 4. Measure using the offset of physical to focus distance from the screen to the CCD plane of the camera. 0.5m CCD Plane 29
HOW TO SET UP THE MEASUREMENT 5. Check Alignment of the Display The display must be centered at the camera s optical axis, with no rotation or tilt < 0.1 mm < 0.1 mm - x < 0.1 mm / y < 0.1 mm - Axial rotation < 0.5 / Horizontal tilt < 0.5 / Vertical tilt < 0.5 < 0.5 < 0.5 Display orientation is measured by the software < 0.5 30
SPARKLE ALIGNMENT Example Application: Software alignment window refreshing the angular & offset measurement by localizing the 5 dots 31
HOW TO SET UP THE MEASUREMENT 6. Double-check Focus Mode in software to ensure you are centered in the display. 32
HOW TO SET UP THE MEASUREMENT 7. Set the display to green. 0.5m CCD Plane 33
HOW TO SET UP THE MEASUREMENT 8. Ensure all ambient light is removed. 34
HOW TO SET UP THE MEASUREMENT 9. Using the Sparkle Measurement Setup in software, take a measurement and record the value. 35
HOW TO SET UP THE MEASUREMENT 10. Adjust the exposure for the Y filter in software. 36
TAKING A MEASUREMENT 37
TAKING A MEASUREMENT Using the Subframe Tool in software, create a subframe of 500x500 pixels located at the center of the display. 38
TAKING A MEASUREMENT Sub frame Analysis Area 39
SOFTWARE TEST TrueTest Random Mura Algorithm Standard deviation of a population Avg for all ROI 7 8 9 4 5 6 1 2 3 40
SOFTWARE TEST TrueTest Random Mura Algorithm Standard deviation of a population Avg for all ROI 7 8 9 4 5 6 1 2 3 41
SOFTWARE TEST TrueTest Random Mura Algorithm Standard deviation of a population Avg for all ROI AVG% 42
DEFINING ACCEPTABLE TOLERANCES 43
Ranking 1 2 3 4 5 6 7 8 9 10 DEFINING ACCEPTABLE TOLERANCES Display A Human Ranking 10 (best) Measured Sparkle Value 1.36% 1 2 3 4 5 6 7 8 9 10 Human Observers 44
Ranking 1 2 3 4 5 6 7 8 9 10 DEFINING ACCEPTABLE TOLERANCES Display B Human Ranking 7 (acceptable) Measured Sparkle Value 2.21% 1 2 3 4 5 6 7 8 9 10 Human Observers 45
Ranking 1 2 3 4 5 6 7 8 9 10 DEFINING ACCEPTABLE TOLERANCES Display C Human Ranking 6 (poor) Measured Sparkle Value 3.05% 1 2 3 4 5 6 7 8 9 10 Human Observers 46
Ranking 1 2 3 4 5 6 7 8 9 10 DEFINING ACCEPTABLE TOLERANCES Display C Acceptable tolerance 2.21% Human Ranking 6 (poor) Measured Sparkle Value 3.05% 1 2 3 4 5 6 7 8 9 10 Human Observers 47
MEASUREMENT RESULTS CAMERA-TO-CAMERA & CAMERA-TO-HUMAN REPEATABILITY 48
RADIANT DISPLAY TESTING 49
SYSTEM REPEATABILITY SYSTEM USED 1 2 3 4 5 6 7 8 9 10 AVG I16.5M DISPLAY C 500X500 SN 3152 I16.5M DISPLAY B 500X500 SN 3152 I16.5M DISPLAY A 500X500 SN 3152 3.624 3.618 3.611 3.613 3.616 3.613 3.606 3.607 3.613 3.6 3.6121 2.87 2.854 2.871 2.83 2.86 2.808 2.756 2.843 2.809 2.878 2.8379 2.472 2.469 2.474 2.453 2.475 2.45 2.47 2.469 2.474 2.468 2.4674 1 2 3 4 5 6 7 8 9 10 AVG I16.5M DISPLAY C 500X500 SN 555 I16.5M DISPLAY B 500X500 SN 555 I16.5M DISPLAY A 500X500 SN 555 3.652 3.691 3.686 3.692 3.68 3.684 3.679 3.69 3.696 3.681 3.6831 2.973 2.971 2.964 2.968 2.975 2.967 2.984 2.968 2.971 2.975 2.9716 2.57 2.563 2.563 2.57 2.561 2.563 2.585 2.578 2.588 2.588 2.5729 50
SYSTEM REPEATABILITY DUT % diff Camera to Camera Display A 1.95% Display B 4.60% Display C 4.19% 51
RESOLUTION REPEATABILITY Camera To CCD Plane (m) Focus Distance (m) Display C I29 0.483 0.5 3.424 I16 0.483 0.5 3.417 I8 0.483 0.5 3.48 I2 0.483 0.5 3.452 52
SPARKLE MEASUREMENT RESULTS 53
SPARKLE MEASUREMENT RESULTS Maximum Pixel Variation % for a single display 54
CUSTOMER SUCCESS STORY SPARKLE MEASUREMENT CORRELATED TO HUMAN VISUAL PERCEPTION 55
SUPPLIER IQC/OQC STANDARDS 56
SPARKLE IN SUPPLIER DISPLAYS Without AG layer With AG layer 57
Human Rating SPARKLE/HUMAN CORRELATION 10 9 8 7 6 5 4 3 2 1 0 0 1 2 3 4 5 6 7 8 9 10 Radiant Camera (Sparkle) Rating 58
DIRECTIVE FOR STANDARD MEASUREMENT Moving forward, all suppliers must use Radiant s Sparkle Solution. 59
SUMMARY Anti-glare layers improve display visibility in reflective light, but introduce sparkle, which can affect perceived quality of the display. Lack of a repeatable measurement method for sparkle has been a barrier to defining standard quality control processes. A method employing a Radiant ProMetric imaging system, TrueTest Software, and defined setup criteria has been proven at automotive OEM facilities for repeatability with direct correlation to human perception. Using this method, OEMs and manufacturers of displays can set precise tolerances for sparkle and define standards for quality control. 60
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