Download - ECEU692 Subsurface Imaging Course Notes Part 3: Imaging with Light (2) Hyperspectral Imaging
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January 2004 Chuck DiMarzio, Northeastern University 10471-3-1
ECEU692Subsurface Imaging
Course NotesPart 3: Imaging with Light (2)
Hyperspectral Imaging
Profs. Brooks and DiMarzio
Northeastern University
Spring 2004
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January 2004 Chuck DiMarzio, Northeastern University 10471-3-2
Hyperspectral Imaging Concepts
• Absorption• Spectroscopy• Scattering• Reflectance
Spectroscopy• Imaging• Hyperspectral Imaging• The Data Cube
ER-2
AVIRIS
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January 2004 Chuck DiMarzio, Northeastern University 10471-3-3
Beer’s Law
dzLzLdzzLdL
Ldz
dL
zeLL 0
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January 2004 Chuck DiMarzio, Northeastern University 10471-3-4
Sample Absorption Spectra
Data from Van Assendelft, O. W., Spectrophotometry of Haemoglobin Derivatives, Springfield, IL: Thomas, 1970.
Graph by DiMarzio, Warner, Dwyer, Northeastern University, 1994
686
Hb
HbO2 aS
peci
fic
Abs
orpt
ion,
/cm
/M
, Wavelength, nm
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January 2004 Chuck DiMarzio, Northeastern University 10471-3-5
Light in a Turbid Medium
• Specular Components– Fresnel Coefficients
– Beer’s Law
• Diffuse Components– More Complicated
• Some Examples– Paint
– Clouds
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January 2004 Chuck DiMarzio, Northeastern University 10471-3-6
Reflectance Spectroscopy;Weak Scattering
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January 2004 Chuck DiMarzio, Northeastern University 10471-3-7
A Simple Model
a(1)=C11(1)+ C22(1)
a(2)=C11(2)+ C22(2)
Two Measurements, Two Equations, and Two Unknowns
Later, Prof. Brooks will talk about inverting these equations
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January 2004 Chuck DiMarzio, Northeastern University 10471-3-8
Reflectance Spectroscopy;Strong Scattering
No Hb
HbO2
Hb
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January 2004 Chuck DiMarzio, Northeastern University 10471-3-9
Pulse Oximeter
• 2 LED’s– Different IR
Wavelengths
• DC Components– Total Hb, HbO2, Other
Absorbers
• Pulsatile Component– Arterial Hb, HbO2
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January 2004 Chuck DiMarzio, Northeastern University 10471-3-10
Hyperspectral Imaging Overview• Definition (Multi-, Hyper, Ultra-Spectral)• The Data Cube• Image Acquisition Hardware, Data Visualization• HOSIS - Hyperspectral Oxygen Saturation
Imaging System: – CCD
– Lyot Filter
– Digital Imaging
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January 2004 Chuck DiMarzio, Northeastern University 10471-3-11
Hyperspectral Imaging
• Definitions?– Imaging in multiple
bands with width less than (10%?) of the center frequency
– Imaging in more than (25?) bands
– Imaging in Contiguous Bands
x
y
The Hyperspectral“Data Cube”
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January 2004 Chuck DiMarzio, Northeastern University 10471-3-12
Hyperspectral Imaging Hardware Concepts (1)
• Camera Coordinates are Spatial
• Successive Images are Different Wavelengths
TunableFilter
B/WCamera
x
y
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January 2004 Chuck DiMarzio, Northeastern University 10471-3-13
Hyperspectral Imaging Hardware Concepts (2)
• Pushbroom Scan– Airborne or Vehicle Mounted?
– Camera Coordinates are y, – Successive Scans are Different
values of x
x
y
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January 2004 Chuck DiMarzio, Northeastern University 10471-3-14
HOSIS Instrumentation Block Diagram
Computer System with Video Board
Processed Images
Tunable FilterSee SupplementaryNotes
CCD Camera
Halogen Lamp
Target Tissue
Thanks to Peter Dwyer atLucid Technologies, MGH, and NU
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January 2004 Chuck DiMarzio, Northeastern University 10471-3-15
Quantitative Imaging
• Quantitative Calculations– Difficult
– Subject to Change
• Calibration Standards– Light Level
– Reflectance
DarkWhite
DarkTarget
R
• Sources of Variation– Light Source
– Camera Sensitivity
– Filter Losses
– Geometry
– Atmosphere?
– Other?