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Radiant Vision Systems | A Konica Minolta CompanyPresented by Shannon Roberts | September 10, 2019
CCD OR CMOS? HOW IMAGING SENSOR PROPERTIES AFFECT PIXEL-LEVE MEASUREMENT OF DISPLAYS
Global SupportAutomated Visual InspectionLight & Color
3Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
TODAY’S AGENDA
• “We Need More Pixels”
• Improving Visual Experiences in Displays
• Importance of Pixel-Level Measurement
• Capturing Unique Pixels (Measurement Resolution)
• Capturing Repeatable Data (Measurement Noise)
• Imaging System Specifications
• Optimizing Resolution and Noise
• CCD versus CMOS performance
• Summary
“WE NEED MORE PIXELS”Improving Visual Experiences in Displays
5Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
“WE NEED MORE PIXELS”
Source: [Charbax]. (2017, June 8). Google Keynote at SID Display Week, Clay Bavor, VP of Google VR/AR [Video File]. Retrieved from https://www.youtube.com/watch?v=IlADpD1fvuA
6Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
REPLICATING REALITY
• Bavor, on VR: “An actual-reality headset with 20/20 vision …that's what we're going for.”
20/20
20/100*
*20/200 = legally blind
7Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
BENEFITS OF “WAY, WAY MORE PIXELS”
• Pixel size / density
• Greater detail in the same area
10x10 20x20 50x50
IMPORTANCE OF PIXEL-LEVEL MEASUREMENTChallenges Capturing Accurate Pixel Values
9Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
IMPORTANCE OF MEASUREMENT
• Pixel Defects:
• Stuck on, off (dead) pixels
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© Radiant Vision Systems, LLC.
IMPORTANCE OF MEASUREMENT
• Pixel Defects:
• Non-uniform pixels
MicroLED Display
OLED Display
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© Radiant Vision Systems, LLC.
IMPORTANCE OF MEASUREMENT
• Pixel Defects:
• Non-uniform pixels
Pixel-level variation Actual OLED measurement
(luminance in false color)
12Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
OBJECTIVES IN MEASUREMENT
Sufficiently Isolate Each Pixel(Measurement Resolution)
Repeatability Across All Pixels(Measurement Signal to Noise)
10x10
IMAGING SYSTEM SPECIFICATIONSOptimizing Resolution and Signal-to-Noise Ratio
14Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
IMAGING PHOTOMETERS
• Full display analysis.
• Actual measurements shown with luminance (brightness) in false color scale.
15Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
IMAGING SYSTEM SENSORS
Representation ofSensor Pixels
One Sensor Pixel
16Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
OBJECTIVES IN MEASUREMENT
Sufficiently Isolate Each Pixel(Measurement Resolution)
Repeatability Across All Pixels(Measurement Signal to Noise)
10x10
17Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
MEASUREMENT RESOLUTION
• What if we don’t have sufficient image resolution?
3x3 sensor pixels: 1 display pixel
18Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
MEASUREMENT RESOLUTION
• What if we don’t have sufficient image resolution?
6x6 sensor pixels: 1 display pixel
19Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
MEASUREMENT NOISE
• What if we have too much image noise?
20Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
THE ARGUMENT FOR LARGE SENSOR PIXELS
• Photon Shot Noise
• Random statistical variation of photons captured by a sensor
• Pixel Well Capacity
• The amount of electron charge a pixel can hold
• Full well capacity = pixel saturation
P
PP
Well
Pixel Size
Photons per μm2
P P
P P
P
e-e-e-e- e- e-e-e-e-e- e- e-e-e-e-e- e- e-e-e-e-e- e- e-e-e-e-e- e- e-
e-e-e-e- e- e-e-e-e-e- e- e-e-e-e-e- e- e-e-e-e-e- e- e-e-e-e-e- e- e-
e-e-e-e- e- e-e-e-e-e- e- e-e-e-e-e- e- e-e-e-e-e- e- e-e-e-e-e- e- e-
e-e-e-e- e- e-e-e-e-e- e- e-e-e-e-e- e- e-e-e-e-e- e- e-e-e-e-e- e- e-
e-e-
LIGHT
Saturation(e-)
21Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
EFFECT OF SENSOR RESOLUTION
Increasing resolution within same sensor area => Smaller Pixels
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© Radiant Vision Systems, LLC.
LIMITS ON SENSOR SIZE
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© Radiant Vision Systems, LLC.
RESOLUTION VS. NOISE
Low Resolution, Low Noise High Resolution, High Noise
24Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
RESOLUTION VS. NOISE
Optimize Resolution vs. Noise
CCD VS. CMOS IMAGINGComparison of Today’s Technologies for Pixel Measurement
26Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
CCD VS. CMOS SENSORS
= photo-sensing unit = decode & readout= readout electronics
CCD Sensor CMOS Sensor
27Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
HOW TO COMPARE IMAGING PERFORMANCE?
Specification Value
Sensor Type CCD
Resolution (Megapixels)
50.6
Sensor Pixels 8712 x 5813
Bit Depth 12 bit
System Accuracy
Illuminance ± 3%; Luminance (Y) ± 3%
CCD Imaging System CMOS Imaging System
Specification Value
Sensor Type CMOS
Resolution(Megapixels)
50.6
Sensor Pixels 8712 x 5813
Bit Depth 12 bit
System Accuracy
Illuminance ± 3%; Luminance (Y) ± 3%
28Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
PHOTON TRANSFER CURVE (PTC) METHOD
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© Radiant Vision Systems, LLC.
PHOTON TRANSFER CURVE (PTC)
Full Well
Slope = 1/2
LOG (Signal)
LO
G (
Nois
e)
30Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
CCD VS. CMOS PHOTON TRANSFER CURVE (PTC)S
IG
NA
L T
O N
OIS
E
SIGNAL [e-]
• CCD Realized • CMOS Realized — Perfect System
Full Well (CMOS) Full Well (CCD)
31Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
DETECTING SUBTLE VARIATIONS IN LIGHT
• Large pixels have a greater well
capacity
• High electron count is necessary
to discern sub-percent variation
in luminance
• SNRMax < Sqrt(Well Size)
• More than 10ke- are needed for a
1% difference detection
32Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
CCD VS. CMOS ACROSS LUMINANCE LEVELS
• We need to measure displays at bright state and dark state
• With larger well capacity, CCDs can detect extremely subtle variations (<1% pixel-level variation) at both bright and dark states CMOS CCD
33Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
HOW CAN YOU TELL?
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© Radiant Vision Systems, LLC.
CCD VS. CMOS SUMMARY
CCD Benefits
• Signal to Noise Ratio
• Larger well capacity, acquiring more photons per pixel
• Repeatability
• Performance at All Levels of Saturation
CMOS Benefits• Speed• Photo-sensors and
amplifiers are within the same cell
• Cost• Can be produced on any
standard silicon production line
• Performance at Low Levels of Saturation
35Radiant Vision Systems | A Konica Minolta Company
© Radiant Vision Systems, LLC.
THE MOST ACCURATE IMAGING SOLUTION FOR PIXEL-LEVEL MEASUREMENT (CURRENTLY)
• CCD sensors • Best balance of resolution/noise
• Excellent light sensitivity
• Repeatable (fewer false positives/negatives)
• More accurate measurement pixels per display pixel
• More reliable data across bright states or gray levels
Radiant Vision Systems | A Konica Minolta CompanyRadiant Vision Systems | A Konica Minolta CompanyQuestions? Contact [email protected]
THANK YOU!