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ECEU692 Subsurface Imaging Course Notes Part 3: Imaging with Light (2) Hyperspectral Imaging. Profs. Brooks and DiMarzio Northeastern University Spring 2004. Hyperspectral Imaging Concepts. ER-2. Absorption Spectroscopy Scattering Reflectance Spectroscopy Imaging Hyperspectral Imaging - PowerPoint PPT Presentation
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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
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
January 2004 Chuck DiMarzio, Northeastern University 10471-3-3
Beer’s Law
dzLzLdzzLdL
Ldz
dL
zeLL 0
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
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
January 2004 Chuck DiMarzio, Northeastern University 10471-3-6
Reflectance Spectroscopy;Weak Scattering
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
January 2004 Chuck DiMarzio, Northeastern University 10471-3-8
Reflectance Spectroscopy;Strong Scattering
No Hb
HbO2
Hb
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
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
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”
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
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
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
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?
