HSI Course

1
Hyperspectral Imaging Scientific Principles
Dr. Richard B. Gomez, Instructor George Mason
University
2
Outline

• Electromagnetic Propagation
• What is light?
• Atoms and Molecules
• Physics of Imaging Spectroscopy
• What is Spectroscopy?
• Interaction of Light with Matter
• Reflection and Refraction of Light
• Sensor Physics
• Spectrometers
• Dispersion Systems

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Scientific Principles

• Photons strike the Earths surface and certain
  photons are either absorbed or reflected
• Various materials absorb sunlight over specific
  wavelength intervals resulting in absorption
  features in reflectance spectra
• The location and shape of these unique absorption
  features provide information on the chemical
  composition of materials

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Absorption of Light
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Molecular Spectra
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Reflection and Refraction of Light
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Refraction of Light
Refraction is responsible for image formation by
lenses and the eye.
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Photomultiplier
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Lens
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Image Formation
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Index of Refraction and Snells Law
n c/v (refractive index) c
speed of light in vacuum v speed of
light in medium
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Reflection and Refraction of Polarized Light
For the ray incident normally to the border there
is no difference between the parallel and
perpendicular components.
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Real and Virtual Images
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Prism
n sin x0 / sin x sin z / sin z0
         n sin (a/2 j/2) / sin ( a/2 )
D dj / dl (dj / dn)(dn / dl )
dn / dj cos (a /2 j /2) / 2sin ( a /2 )
15
Diffraction Grating
A diffraction grating is the tool of choice for
separating the colors in incident light.
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Fraunhofer Diffraction
The intensity of the light getting pass through
the slits depends upon the angle j between the
direction of the light propagation and the
perpendicular to screen where I0 is the
intensity of the light in the center of
diffraction pattern when only one slit is opened,
b is the width of the slit, d is the distance
between the slits, k2p /l  is the wave factor, l
is the wavelength, D is the difference of the
optical lengths of  the interfering rays
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Fraunhofer Single Slit Diffraction
The diffraction pattern at the right is taken
with a helium-neon laser and a narrow single slit.
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Double Slit Diffraction
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Spectrometer Instrument