Micro Hyperspectral Systems

For UAVs

If a picture is worth 1000 words, a hyperspectral image is worth almost 1000

pictures

Dr John P FergusonPhotonics & Analytical Marketing Ltd

RSPSoc and NERC Cluster UAV WorkshopUniversity of Durham, 7-8 June 2011

TOPICS TO BE COVERED

Headwall PhotonicsExplanation of Hyperspectral ImagingSome applicationsThe Headwall Micro HyperspecImaging 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• 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 SystemsSpace

Piloted

UAV

Ground-based

Handheld Reconnaissance

Base protection

Multiple Platforms

Small Satellite

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

25 Proprietary and Confidential

Hyperspectral Design Options

Aberration-Corrected Concentric– All-reflective system– Three reflective surfaces

Prism-Grating-Prism– Transmission-based grating system

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

Deployment in harsh environments• Ruggedized & durable• Small, compact size

• Minimal thermal expansion

Attributes- 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

THE HEADWALL PATENTED SPECTROGRAPH DESIGN

EntranceSlit

DetectorPlane

Original holographichigh efficiency convex grating

Hyperspec© Concentric Design

• Advantages - selection of concentric design …– Extremely compact nature– Image quality (spectral/spatial resolution)– Superior aberration-correction characteristics– Lower F number– All reflective design

• Additionally, Headwall sensors offers additional benefits …– Balanced spectral performance across range– Lower stray light– Tall image slits - Spectral & spatial performance off-axis– Performance in lower VIS / blue region

Fore-optics Imaging Spectrograph Detection Electronics

Key Imaging Spectrograph Risks: Keystone (spatial distortion)

Smile (spectral distortion)

VignetteScatter (transmissive materials, poor surface qualities, replicated optics)

Stray Light (overfilled optics, secondary diffracted orders, inadequate baffeling)

Chromatic Aberrations and AstigmatismLow Optical Dynamic Range

THE SALES PITCH

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 depthPixel resolution (spatial and spectral)

Spectral band sensitivityReadout speedReadout methodSecond order detection

CAMERA CONSIDERATIONS

Traditional Hyperspectral Imaging Deployments

Remote SensingSurveillance

Target Identification & Tracking

Spectral Tagging

Search & Rescue

Ocean Monitoring

Geological Mapping

EnvironmentalAnalysis

Photos: Courtesy of NRL, Space Computer, BAE, General Atomics

Military/Defense

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 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

38 Proprietary and Confidential

• 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

NIR High Efficiency Modeled and Measured Grating Efficiency

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800

Wavelength (nm)

Eff

icie

ncy

(%

)

Measured

Modeled

High Efficiency sensors offer peak efficiency greater than 90%, minimum 70%

• Custom designed fore-optics

Thank you for listening