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 radiation Optomechanics (fore lens and spectrograph) in front of the detector 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/or Make the signal from target higher -> heat up or illuminate the sample. 2. Signal = Reflection + Emission Solution: Make one component to dominate -> heated ot illuminated sample.
MWIR Push-broom hyperspectral camera Uncooled spectrograph Cryogenically cooled InSb or MCT FPA
SPECIM Thermal Hyperspectral Imagers MWIR 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 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/m 2 sr um 160 mw/m 2 sr um 20 mw/m 2 sr um Power consumption <50 W <4 W <200 W Relative cost 1 0.5 4
Thermal hyperspectral scanner for reflection experiments MWIR 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? 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 SWIR MWIR HIPS Transparent Dark HIPS Transparent Dark
Identification of dark materials MWIR (red curve dark sample, white curve transparent sample) ABS PC-ABS PC Sufficient spectral information for identification/classification of dark materials. Moisture on surface to be removed.
Mineral mapping TIR = Thermal LWIR Infrared
Mineral mapping Red: Quartz Red: Quartz White: Feldspar?
Mineral mapping in the exploration and mining field Trial project by Anglo Gold Ashanti: 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 SWIR + VNIR/RGB LWIR option 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 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 for single-point instruments. Expanded capabilities for multipoint and hyperspectral imaging applications. 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 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). 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 240 spectral bands 100 images/s 81920 spectra/s! GPU accelerated real-time prediction
Summary MWIR hyperspectral imaging will make possible aplications where VNIR and SWIR do not provide the information. 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)?