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UAV Workshop 7 th July 2011

A novel hyperspectral imager b ased on microslice technology Ray Sharples, Danny Donoghue, Robert Content Colin Dunlop, David Nandi, Gordon Talbot Durham University. UAV Workshop 7 th July 2011. Outline of Presentation. Background Methods for simultaneous 3D spectroscopy

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UAV Workshop 7 th July 2011

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  1. A novel hyperspectral imager based on microslice technologyRay Sharples, Danny Donoghue, Robert ContentColin Dunlop, David Nandi, Gordon TalbotDurham University UAV Workshop 7th July 2011

  2. Outline of Presentation Background Methods for simultaneous 3D spectroscopy Operating principles of a microslicehyperspectral imager First laboratory results from a CEOI-funded prototype sensor Future Plans

  3. Divides the field in two dimensions Overlaps must be avoided  less information density in datacube Pupil imagery Lenslet array Datacube Fibre array Fibres slit y  x 1 Image slicer Micro- mirrors slit 2 3 Only the image slicer retains spatial information within each slice/sample  high information density in datacube 4 1 2 3 4 Both designs maximise the spectrum length and allows more efficient utilisation of detector surface. Project Background Telescope focus Spectrograph input Spectrograph output

  4. Project Background

  5. V km/sec x 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

  6. Instrument Concept: Microslice IFU

  7. Instrument Layout Camera (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

  8. Hyperspectral Imaging UsingMicroslice Technologies • Novel application of microlensresampling 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.

  9. 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

  10. Microslicer Assembly

  11. Microslice Optical Performance

  12. Foveon CCD

  13. Flatfield Performance 475-650 nm

  14. Spectral Performance Hg Hg H alpha H beta

  15. Application Tests Lab set up Microslicer & ASD FieldSpec Pro Objectives: Test spectral resolution Test signal / noise ratio Ability to extract spectra Use Spectralon standard

  16. Calibration and Testing

  17. Calibration and Testing 565 nm Fagussylvaticaleaf Source: David Nandi

  18. Extracting spectra from datacube Source: David Nandi

  19. Advantages of MicrosliceHyperspectral 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.

  20. 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 pushbroomor whiskbroom approaches and also allows monitoring of time-dependent processes. Further Details: Prof. Ray Sharples - r.m.sharples@durham.ac.uk Prof. Danny Donoghue - danny.donoghue@durham.ac.uk

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