Hyperspectral Imaging in MWIR and On-line

Timo Hyvärinen, Hannu Holma, Mathieu Marmion and Rainer Bars

SPECIM, Spectral Imaging Ltd, Finland

www.specim.fi

Pekka Teppola and Csaba Finta

VTT Technical Research Centre of Finland

www.vtt.fi

Outline

Thermal hyperspectral imaging

MWIR (3 to 5 um) push-broom hyperspectral camera

MWIR hyperspectral imaging applications

On-line hyperspectral image processing tools

Why hyperspectral imaging in

MWIR 3-5 um?

Information which is not available in VNIR and SWIR.

Stronger spectral signatures (absorption bands).

’See through’ black pigments.

Ability to measure emitted spectral signatures.

Lower cost frame cameras than in LWIR (8 to 12 um).

What makes thermal hyperspectral

imaging different?1. Instrument radiationOptomechanics (fore lens and spectrograph) in front of the detector array emit broad-band thermal radiation.array emit broad-band thermal radiation.May be orders of magnitude higher (per pixel) than the spectrally split signal from the target/sample.Solution:Lower the instrument radiation, and/orMake the signal from target higher -> heat up or illuminate the sample.

2. Signal = Reflection + EmissionSolution:Make one component to dominate -> heated ot illuminated sample.

MWIR Push-broom hyperspectral

cameraUncooled spectrographCryogenically cooled InSb or MCT FPA

SPECIM Thermal Hyperspectral ImagersMWIR LWIR uncooled LWIR cooled

Detector InSb, MCT, 80K Microbolometer, uncooled MCT, 55K

Spectral range 3-5.5 um 8-12 (13) um 7.6-12.5 um

# Spectral bands 120 22 (30) 100

Spectral sampling 17 nm 200 nm (mean) 48 nmSpectral sampling 17 nm 200 nm (mean) 48 nm

Spectral resolution 30 nm 400 nm 100 nm

Spatial pixels 320/640 384 384

Smile, keystone <0.2 pix <0.2 pix <0.2 pix

Image rate, max 350 Hz 60 Hz 100 Hz

Instrument temp. Ambient Ambient Stabilized

NESR@centre of range 70 mW/m2 sr um 160 mW/m2 sr um 20 mW/m2 sr um

Power consumption <50 W <4 W <200 W

Relative cost 1 0.5 4

Thermal hyperspectral scanner for

reflection experiments

MWIR hyperspectral cameraMWIR hyperspectral camera

Thermal line light source

Linear stage

Industrial applications of thermal

hyperspectral imaging

Mineral mapping of geological samples, like drill cores.Fusion of SWIR and LWIR – Could MWIR replace LWIR?Fusion of SWIR and LWIR – Could MWIR replace LWIR?

Sorting of dark materials in recycling processes.

Surface inspection for minute impurities, like oil residual and oxidation on steel surface and uniformity of thin coating layers.

Temperature measurement and mapping independently of emissivity variation.

Identification of dark materials

HIPS HIPS

SWIR MWIR

HIPS HIPS

Transparent

Dark

Transparent

Dark

Identification of dark materials

ABS PC-ABS PC

MWIR (red curve – dark sample, white curve – transparent sample)

Sufficient spectral information for identification/classification of dark materials.

Moisture on surface to be removed.

Mineral mapping

TIR = Thermal LWIR Infrared

Mineral

mapping

Red: QuartzRed: QuartzWhite: Feldspar?

Trial project by Anglo Gold Ashanti:Average data collection rate of 1200 m of core/day

SWIR + VNIR/RGBLWIR option

Mineral mapping in the exploration

and mining field

Average data collection rate of 1200 m of core/day

Full core tray mode in SWIR, 2 mm resolution

Total of 17000 m of core was imaged in two weeks

SisuROCK Hyperspectral Core Imaging Station

Anglo Gold Ashanti, South Africa

Real-time software for hyperspectral

chemical imaging

1. CHEMOM – Chemometrics modelling tool

2. PREDICTOR – Multi-point real-time spectral acquisition 2. PREDICTOR – Multi-point real-time spectral acquisition

and analysis tool

3. IMAGER – Real-time hyperspectral image capture and

analysis tool

1. Chemometrics Modelling Tool

� Chemometric pre-processing and modelling tool originally developed forsingle-point instruments.

� Expanded capabilities for multipoint and hyperspectral imaging applications.

� Five simple and visual steps:� Five simple and visual steps:�Data collection�Spectral preprocessing (17 standard and advanced methods)�Modelling (3 golden standard techniques: MLR, PCR and PLS)�Validation�Calibration transfer (industrial standard: PDS)

� Visual inspection of preprocessing and modeling results.� Automated random and blockwise cross-validation.� Easy of model diagnostics and outlier detection.� Easy testing with independent test sets.� Easy of calibration update and model transfer.

2. Multi-point Real-time Spectral

Acquisition and Analysis Tool

� Camera control (integration, time, frame rate)� Shutter control� Simultaneous measurement on 20 fiber optical channels� Simultaneous measurement on 20 fiber optical channels� Entry for up to 20 different calibration files� Multiple prediction on any channel available� Prediction results displayed as actual values, average and RSD� Captured spectra (raw data) stored in binary format� Prediction results stored in ASCII file� OPC and ModBus (Ethernet) support for the prediction results� Drift (dark current) compensation� Several measurement modes (interval, burst, restart)

Multiple point spectrometer

3. Real-time Spectral Image Capture

and Analysis Tool� Seven SPECIM hyperspectral cameras supported currently.� Camera control (integration, time, frame rate, ROI)� Shutter control� Three different scanners supported (1D and 3D).� Storage of captured data in ENVI format (BIL).� Storage of captured data in ENVI format (BIL).� Buffered image capture ensures loss-free data storage.� Several adjustable triggering conditions for start of data storage, and several

capture modes (interval, burst, restart).

� Entry for application specific prediction model in a text file.� Real time line-by-line processing of the captured data.� Support for GPU accelerated calculations.

� Spectral or 2D (accumulated) display during capture.� Real-time display of raw data, reflectance, absorbance or concentration estimate.� Profile, spectrum or trend graph plotting.� Pick-up of data of interest (clicking the 2D image) as multiple graph.

IMAGER demonstration

SWIR spectral camera• 320 spatial pixels• 320 spatial pixels• 240 spectral bands•100 images/s

81920 spectra/s !

GPU accelerated real-time prediction

SummaryMWIR hyperspectral imaging will make possible aplications where VNIR and SWIR do not provide the information.

Excelent SNR with high spectral Excelent SNR with high spectral resolution and image rate achievable in reflection mode.Performance limited in emission applications.

More affordable technology than high performance LWIR HSI.Less distinctive spectral signatures than in LWIR (minerals)?