1 PHYSICS Demonstration of a Dualband IR imaging Spectrometer Brian P. Beecken Physics Dept., Bethel University Paul D. LeVan Air Force Research Lab, Kirtland AFB Benjamin D. Todt Physics Dept., Bethel University 27 August 2007 San Diego, CA SPIE Conference 6660A Infrared Detectors and Focal Plane Arrays IX
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Demonstration of a Dualband IR imaging Spectrometer
Demonstration of a Dualband IR imaging Spectrometer. 27 August 2007 San Diego, CA SPIE Conference 6660A Infrared Detectors and Focal Plane Arrays IX. Brian P. Beecken Physics Dept., Bethel University Paul D. LeVan Air Force Research Lab, Kirtland AFB Benjamin D. Todt - PowerPoint PPT Presentation
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1
PHYSICS
Demonstration of aDualband IR imaging Spectrometer
Brian P. BeeckenPhysics Dept., Bethel University
Paul D. LeVanAir Force Research Lab, Kirtland AFB
Benjamin D. TodtPhysics Dept., Bethel University
27 August 2007San Diego, CA
SPIE Conference 6660AInfrared Detectors and Focal Plane Arrays IX
2
PHYSICS Classic “2 channel” Spectrometer
• Efficiencies change with λ
– Gratings
– FPA detectors
• Classic Solution: 2 channels
– Common aperture & FOV
– Beamsplitter
– 2 Dispersive elements and 2 FPAs
– Each channel optimized for roughly 1 octave of λ
• Issues
– Size
– Mass
– Power consumption
– λ Registration
– Complex
Dispersive Elements
FPA
3
PHYSICS
Spectral Image, but only 1 spatial dimension
Sp
atia
l Dim
ensi
on
Dualband FPA Diffraction Concept
DispersiveElementSpectral
Dimension
DualbandFPA
Multispectral IR
4
PHYSICS Using Dual-band FPA
• Gratings
– nλ = d sin θ
– Peak efficiencies atλB, λB/2, λB/3,…
• Designed Bands:
3.75 – 6.05 µm (MWIR)
7.5 – 12.1 µm (LWIR)
• λ Gap chosen to prevent spectral crosstalk
• Advantages:
– Reduced Complexity
– Smaller mass & size
– Less cooling required
– Perfect λ registration
2nd order is MWIR1st order is LWIR
320 cols x 240 rows
5
PHYSICS Schematic of Dewar Optics
DualbandFPA
gratingImage formed on slit
6
PHYSICS Solar Observations
• Goal: demonstrate functionality
• Why the Sun?
– Distant
– Extended body for imaging
– Significant IR signature
– It fits: solar θ ~ 0.5°, spectrometer θ ~ 1°
– Demonstrate imaging thru Earth’s atmosphere
– It is there everyday
• Issue: too much radiation → Solar filter Required