Fracture Exercise Exercise (PBL-based) · Video 1 FRAME = 2 FIELDS Even Odd PAL 625x728...
Transcript of Fracture Exercise Exercise (PBL-based) · Video 1 FRAME = 2 FIELDS Even Odd PAL 625x728...
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Fracture Exercise• Laboratory experiments • Digital Imaging
Exercise (PBL-based)
• Compare images from different digital camerasand ”video” cameras.
• Demonstrate blooming/glare, low light conditionsand at least one more noise problem.
• Compare cameras and demonstrate at least onelimitation with a particular technology.
• Explain the physical reasons for the differencesyou observe.
Scene
Sensor
Observer
Imaging principles
Scene Lens Sensor
Image on film
Imaging principles
102030405060708090
100
200 400 600 800
sensitivity
(nm)UV IR
CCD ICX024Eye
Tungsten lamp2856 K
Night sky
Eyenight
Imaging principles Digital Imaging
2
FractureDetails
High Resolution Digital Camera
3120x2064
Pixels
14-bit (16384) resolution
8Mz readout700x500
16-bit (32768)
XMHz
LuLuminanceminance and and contrastcontrast
Scene luminance
Sensorsignal range
Monitordisplay range
1
10
100
1000
Black
White
verybright
verydark
dark
lightsaturation
noisyHigh
contrastscene
Lowcontrastscene
jai 75xjai
videoprocess
10
Scene illumination10
101010101101010-4
-3
-2
-1
1
2
3
4
5 Direct sunlightFull daylightOvercast dayVery dark dayTwilightDeep twilightFull moonQuater moonStarlightOvercast starlight
Dynamical resolution
High Resolution Digital Cameras
• Light sensitive• High spatial and
dynamical resolution• Low noise
MORE SENSITIVE THAN THE EYE
• Slow data transfer• Produces much data• Requires custom made
software• Not user friendly• Expensive
Advantages Drawbacks
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CCD
CCD principle
CMOS
With on chip microlens
Interline Transfer CCD
Fill <100%Fill 35%
Photo diode
CMOS
Noise
• Shot noise / thermal / dark current• Read-out noise• Saturation / Glare / Blooming• High energetic ”cosmic” rays• ”Digital noise” / Moirè patterns
Binning
4
Frame Transfer and EEC
Frame-transfer CCD
Camera
Image
Scene
Process
Trans-port
Remote place Distance Localobserver
Video
1 FRAME = 2 FIELDSEven Odd
PAL 625x728 ”pixels” 50 Fields/25 Frames pr. Sec (528 image lines)
Video
Exposure TimeXSG
Video Out8 22
Selected exposure time
Video as result ofselected exposure time
Ver. sync
External Trigger
Exposure Time
WEN Out
Video Out
Hor. Sync
XSUB
XSG
Video
Video tape Frame grabber Color
5
400 500 600 700 800 900 1000Wave lenght (nm)
1.0
0.8
0.6
0.4
0.2
0.0
Rel
ativ
e re
spon
se
B G R
IR stopfilter
Color Bayer RGB filters
Blue pixel X,Y
Red pixel X,Y
Green pixel X,Y
3 chip CCD 3 chip CCD cameracamera
CoCo--site samplingsite sampling
RGB sensors arealligned pixel to pixel
FOV
PhotochargeEIA camera
Lamp supply50 Hz
Light
Shuttertime = 10 msec
Shutter time = one light period, photocharge = constant
Result = no flicker and reduced sensitivity
Flicker Optics
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Test targets Image analysis
• Object properties
• Feature tracking / pattern matching
• Differences
• Transformations
Object Properties Object Properties
Object PropertiesSubSub pixel pixel measurementmeasurement
Fine line
Defocussedfine line
CL
Pixel signal
Imagedobject
Object center found by calculationswith pixel signals
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Image analysis
• Object properties
• Feature tracking / pattern matching
• Differences
• Transformations
Velocity measurementsDV-images, 40ms apart, 1/16000 s exposure time
128x128 diamond shaped region tracking scheme
Tracking Scheme Explained Pixel Comparison AlgorithmsS1 = | If − I0 |
T∑
S2 = (If − I0)2
T∑
S3 =(If * I0)
T∑
( If2
T∑ Io
2
T∑ )
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S4 =[(If − If) * (I0 − I0)
T∑ ]
( (If − If )2
T∑ (I0 − I0)2 )
12
T∑
Velocity fluctuationsTransformation
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Differences
Differences Exercise (PBL-based)
• Compare images from different digital camerasand ”video” cameras.
• Demonstrate blooming/glare, low light conditionsand at least one more noise problem.
• Compare cameras and demonstrate at least onelimitation with a particular technology.
• Explain the physical reasons for the differencesyou observe.