Advanced Microslice Technologies for Hyperspectral Imaging of the
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Transcript Advanced Microslice Technologies for Hyperspectral Imaging of the
A novel hyperspectral imager
based on microslice technology
Ray Sharples, Danny Donoghue, Robert Content
Colin Dunlop, David Nandi, Gordon Talbot
Durham University
UAV Workshop
7th July 2011
Outline of Presentation
• Background
• Methods for simultaneous 3D
spectroscopy
• Operating principles of a microslice
hyperspectral imager
• First laboratory results from a CEOIfunded prototype sensor
• Future Plans
Project Background
Divides the field in two dimensions
Telescope
focus
Lenslet
array
Spectrograph
input
Spectrograph
output
Overlaps must be avoided
less information density
in datacube
Pupil
imagery
Datacube
slit
Fibre
array
Fibres
y
x
Image
slicer
Micromirrors
1 2 3 4
1
slit
2
3
4
Both designs maximise the spectrum length and allows
more efficient utilisation of detector surface.
Only the image slicer retains
spatial information within each
slice/sample
high information density
in datacube
Project Background
A New Approach to
Hyperspectral Imaging
• Fully exploit modern large-format 2D detectors
to obtain faster survey speeds.
• Longer exposures in stare-mode to allow higher
SNR in finer pixels for radiometry, meteorology
& and atmospheric composition studies particularly important for low reflectivity targets
such as water, forestry and shallow marine
environments.
• Enable smaller, more compact devices than
other comparable platforms. Compact designs
using state-of-the-art sensors to reduce
mass/volume requirements.
• Step-change in the imagery available to assist
in meeting NERC targets for Earth observation
with applications in many areas: not in the least
vegetation, geology and pollution monitoring.
• CEOI Seedcorn Project: budget £50k.
Dwell time = x/V
V km/sec
x
Instrument Concept: Microslice IFU
Camera
Instrument Layout
(cover omitted)
Image slicer
Dimensions 33 cm x 15 cm x 12 cm
Mass ~5 kg (excl baseplate)
GRISM
Pick-off
mirror
Collimator
Fore-optics
Baseplate
CEOI Mid-Term Review Meeting 12 Jan 2011
Hyperspectral Imaging Using
Microslice Technologies
• Novel application of microlens resampling optics to deliver
unprecedented field-of-view sampling over multiple spectral channels
simultaneously.
• Addresses current spectral resolution and sensitivity limitations with
available airborne/spaceborne instruments.
• Enables high spectral resolution observations to characterise and quantify
ecosystem and land/water surface properties.
• Allows spectral fingerprinting to be scaled up to address whole Earth
system processes.
Prototype Microslice Spectrograph
• NERC Centre for Earth Observation Instrumentation Seedcorn
Project started April 2010.
• 330 x 20 “spaxels” (spatial pixels each giving a spectrum) so 6,600
spectra.
• Spectra 180 pixels long
• Resolution of 5-7 nm (slice images 3 pixel wide) over 400 nm to
700nm
• Dimensions 33 cm x 15 cm x 12 cm
Microslicer Assembly
Microslice Optical Performance
Foveon CCD
Flatfield Performance
475-650 nm
Spectral Performance
Hg
Hg
H alpha
H beta
Application Tests
• Lab set up Microslicer & ASD FieldSpec Pro
• Objectives:
–
–
–
–
Test spectral resolution
Test signal / noise ratio
Ability to extract spectra
Use Spectralon standard
Calibration and Testing
Calibration and Testing
565 nm Fagus sylvatica leaf
Source: David Nandi
Extracting spectra from datacube
Source: David Nandi
Advantages of Microslice
Hyperspectral Imagers
• Rapid survey speeds with options for multiple viewing geometries.
• High spatial resolution with no limitations due to scanning speed on a
single overpass as with pushbroom techniques.
• High spectral and spatial resolutions.
• Longer exposures in stare-mode to allow higher SNR in finer pixels for
radiometry, meteorology and atmospheric composition studies.
• Signal strength is also particularly important for low reflectivity targets
such as water and shallow marine environments.
• Compact design using state-of-the-art sensors to reduce mass/volume
requirements.
Summary
• Knowledge transfer from astronomy to remote sensing is opening up new
concepts for hyperspectral imaging of the environment.
• Extreme multiplex microslice technologies offer a new approach to obtain
high spatial and spectral resolution simultaneously over a 2D FoV.
• The use of step and stare modes offer the potential for 2-3 orders of
magnitude increase in S/N compared with pushbroom or whiskbroom
approaches and also allows monitoring of time-dependent processes.
Further Details:
Prof. Ray Sharples - [email protected]
Prof. Danny Donoghue - [email protected]