Micro Hyperspectral Systems
For UAVs
If a picture is worth 1000 words, a
hyperspectral image is worth almost 1000
pictures
RSPSoc and NERC Cluster UAV Workshop
University of Durham, 7-8 June 2011
Dr John P Ferguson
Photonics & Analytical Marketing Ltd
TOPICS TO BE COVERED
Headwall Photonics
Explanation of Hyperspectral Imaging
Some applications
The Headwall Micro Hyperspec
Imaging from UAVs
HEADWALL PHOTONICS INC
1976 - American Holographic, Inc.
2000 - Agilent Technologies acquisition
2003 – Headwall Photonics launched
Currently 40 employees
Factory in Fitchburg, Massachusetts, USA
Producers of imaging spectrometers, OEM
spectral engines, original holographic gratings
Applications of Headwall Technology
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Hyperspec V10 – Marine Ocean Buoy Project (MOBY)
Hyperspec VS30 – NRL airborne requirement for remote sensing and ocean
color monitoring
Hyperspec VS15 – USAF airborne mine detection in littoral zones
Hyperspec VS15 – USN Predator-based project for Project Warhorse
Hyperspec VS15 – NRL Ocean PHILLS sensor
Hyperspec VS15 – AFRL LWIR sensor for polarimetric sensing for battlefield
surveillance
Hyperspec VS25 – Selected by NASA for International Space Station deployment
Hyperspec VS25 – First UAV deployment
Hyperspec VS – Custom UV/MCP unit deployed for AFRL missile plume tracking
Hyperspec VS50 – Airborne SWIR sensor
Micro-Hyperspec VNIR and NIR – Introduced in 2006 for UAV and SUGV
deployment
Hyperspec-VNIR – NASA deployment for AVIRIS project augmentation
Hyperspec-VNIR, Hyperspec-NIR, Hyperspec-SWIR – integrated instruments for
commercial applications
Micro-Hyperspec – UAV remote sensing
Applications of Headwall
Hyperspectral Systems
Space
Small Satellite
Piloted
UAV
Ground-based
Handheld
Multiple
Platforms
Base protection
Reconnaissance
WHAT IS HYPERSPECTRAL IMAGING?
• Collection of high resolution spectral detail over
a large spatial and broad wavelength region
from within each pixels instantaneous field of
view
• Also known as imaging spectroscopy, chemical sensing
• Chemical/spectral imaging within spatial dimension
• Many definitions
– Common requirement = > ~ 100 spectral bands
– No definition has explained spatial requirements
Example – Airborne remote sensing
Image Source: BAE Systems
THE VISIBLE LIGHT SPECTRUM
What information can the spectrum tell us?
The type of building material used
The type of vegetation
The rock strata
The type of ground
How does it work?
AN OUTLINE OF HYPERSPECTRAL IMAGING
A TYPICAL SCENE
THE CAMERA’S VIEW
THE VIEW THROUGH A SLIT - PIXELS IN ROW 7
PIXELS IN ROW 11
PIXELS IN ROW 17
THE HYPERSPECTRAL DATA
CLOSER TO REALITY
A HYPERSPECTRAL DATA CUBE
Some technical stuff
Hyperspectral Design Options
Prism-Grating-Prism
– Transmission-based
grating system
Aberration-Corrected Concentric
– All-reflective system
– Three reflective surfaces
Headwall’s imager design optimized for …
Imaging performance –
• Aberration-corrected
• Minimal stray light
• High signal-to-noise
• High dynamic range
• High spectral/spatial resolution
• Efficiency across total spectral range
25
Proprietary and Confidential
Deployment in harsh environments
• Ruggedized & durable
• Small, compact size
• Minimal thermal expansion
THE HEADWALL PATENTED SPECTROGRAPH DESIGN
Attributes
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Integrated spectrometer solution
High spectral/spatial resolution
Very tall image slit
Very low image distortion
Low stray light, high signal-to-noise
Small package size
Flight hardened no moving parts
Entrance
Slit
Original holographic
high efficiency
convex grating
Detector
Plane
©
Hyperspec
Concentric Design
• Advantages - selection of concentric design …
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Extremely compact nature
Image quality (spectral/spatial resolution)
Superior aberration-correction characteristics
Lower F number
All reflective design
• Additionally, Headwall sensors offers additional benefits …
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Balanced spectral performance across range
Lower stray light
Tall image slits - Spectral & spatial performance off-axis
Performance in lower VIS / blue region
THE SALES PITCH
Fore-optics 
Imaging Spectrograph  Detection Electronics
Key Imaging Spectrograph Risks:
Keystone (spatial distortion)
Smile (spectral distortion)
Vignette
Scatter (transmissive materials, poor surface qualities, replicated optics)
Stray Light (overfilled optics, secondary diffracted orders, inadequate baffeling)
Chromatic Aberrations and Astigmatism
Low Optical Dynamic Range
CAMERA CONSIDERATIONS
Fore-optics  Imaging Spectrograph 
Detection Electronics
Key Detection Electronics Risks:
Base chip dynamic range - pixel full well capacity / (dark current + read noise)
A/D bit depth
Pixel resolution (spatial and spectral)
Spectral band sensitivity
Readout speed
Readout method
Second order detection
Traditional Hyperspectral Imaging
Deployments
Remote Sensing
Military/Defense
Ocean
Monitoring
Surveillance
Search & Rescue
Geological
Mapping
Target Identification
& Tracking
Environmental
Analysis
Spectral
Tagging
Photos: Courtesy of NRL, Space Computer, BAE, General Atomics
Micro-Hyperspec™ for UAVs
Design goals:
– Very small size, form factor
• Less than 1 lb pounds
– Excellent imaging and S/N
performance
• Aberration-corrected optics
– Low-power CCD/CMOS sensor
– Modular for variety of input &
detector options
Spectral Ranges
• VNIR - 400-1000nm
• NIR - 900-1700nm
Micro-Hyperspec in Agriculture
Micro-Hyperspec for
Airborne Turrets & Gimbals
Fully integrated –
sensor, GPS/INS,
processor board
Designed for
integration
into UAV turrets
& gimbals
Single
attachment
point
Micro-Hyperspec – Small Tier UAVs
Mounting Options
Tier 2 UAV Hyperspectral mounting options Micro-Hyperspec within Payload Bay
- Payload bay or forward turret
Micro-Hyperspec – Payload Bay
Mounting Tier II UAV
Fiber-Optic-Downwelling Irradiance Sensor (FODIS)
• In-flight calibration of Hyperspec© sensor
– Fully reflective FODIS module allows frame-by-frame real-time tracking of
the solar Irradiance allowing
High Efficiency Sensors
• Three spectral ranges –
Ext VNIR (600-1700nm), NIR (900-1700nm), & SWIR (900– 2500nm)
• Extremely high optical efficiency
• Lightweight for airborne missions
• Athermal design for measurement accuracy and stability
• Tall image slit for wide field of view, swath path efficiency
• Custom designed fore-optics
NIR High Efficiency Modeled and Measured Grating Efficiency
100%
90%
80%
High Efficiency sensors offer
peak efficiency greater than 90%,
minimum 70%
Efficiency (%)
70%
60%
50%
40%
Measured
30%
Modeled
20%
10%
0%
500
38600 Proprietary
Confidential
700
800and 900
1000 1100
1200
1300
Wavelength (nm)
1400
1500
1600
1700
1800
Thank you for listening