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© analytikLtd
analytikLtd
VideometerLab 3 Multi-Spectral Imaging
Rapid Non-destructive Surface Analysis
Adrian Waltho, Analytik Ltd (Cambridge, UK)
www.analytik.co.uk/multispectral-imaging
• Light reflectance at separate colours
• Statistical image processing
• Chemical, physical and spatial properties
• Differentiate | Quantify | Report
© analytikLtd
Traditional colour imaging uses three broad bands of colour:
Red, Green and Blue
Normal Colour Imaging
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Normal Colour Imaging
• RGB photographs have limited spectral resolution
• Chlorophyll a and b give almost the same RGB signal and are not spectrally separated
Chloro-a High Low High
Chloro-b High Low High
© analytikLtd
Multispectral Imaging
Chloro-a High Low Low High
Chloro-b Med High Med Low
• Using just 4 wavelength bands with tightly defined ranges, Chlorophyll a and b can easily be distinguished
• VideometerLab 3 uses 19 wavelength bands
© analytikLtd
Multispectral Imaging
• Many images obtained at selective wavelength bands
• Each image pixel contains spectral data points
• Spectral signature reveals chemo-specific information
• See spatial location of surface chemical variation
Ultraviolet Near-Infrared
Infra-Red Red Yellow Green Blue Ultra-Violet
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VideometerLab 3 Schematic
• Narrowband illumination provided by 19 LEDs between 375nm-970nm (UV-Vis-VNIR)
• Integrating sphere diffuses light onto sample
• 2056x2056 CCD camera captures reflectance at each LED wavelength for each pixel
• Emission filter wheel for longpass/bandpass filtering
• Bright-field or dark-field lighting for translucency or diffuse scatter imaging
Camera
LEDs
Integrating sphere
Emission filter wheel
Sample
© analytikLtd
VideometerLab 3 Schematic
• Precise lighting control for optimal illumination of each sample across whole spectrum
• Diffuse light on sample ensures even lighting from all directions
• Broadband camera spectrally and spatially calibrated (NIST)
• Emission filters enable multispectral reflectance and fluorescence imaging abilities
• Powerful, user-friendly image analysis and quantification software for data and modelling
Camera
LEDs
Integrating sphere
Emission filter wheel
Sample
© analytikLtd
VideometerLab 3 Schematic
Back to Index
Zoom area for next slide
Bodleian Library – Papyrus Hieroglyphics
Back to Index
Bodleian Library – Papyrus Hieroglyphics
Back to Index
Same area at 850nm (infrared) illumination (false
coloured) – note smudge (fingerprint?) just above tear
in paper, invisible in RGB image
Bodleian Library – Papyrus Hieroglyphics
Back to Index
nCDA transformation of same area
Back to Index
Palimpsest sRGB image
Zoom area for next slide
Back to Index
Close-up of zoomed area
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nCDA transform highlights original text
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Historic Scotland – Pigment analysis
Back to Index
• Circled are cadmium red and lead white pigment samples
© analytikLtd Back to Index
• Circled is a mix of cadmium red and lead white
Historic Scotland – Pigment analysis
© analytikLtd Back to Index
• The VideometerLab can build up a library of the spectral responses of each pigment
Historic Scotland – Pigment analysis
© analytikLtd Back to Index
• The VideometerLab can then recognise this spectrum in unknown samples. We see that the pure cadmium red and the cadmium red mix are both ‘hits’ for the cadmium spectrum
Historic Scotland – Pigment analysis
© analytikLtd Back to Index
• We can also see that the more pure spectrum registers as a closer fit than the cadmium-lead mix. We see this because the pure cadmium is much more orangey in the false-colour image
Historic Scotland – Pigment analysis
© analytikLtd Back to Index
• This technique can be applied to paintings, for example this portrait of a captain from Leith
Historic Scotland – Pigment analysis
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• By using false-colouration, we can see that the yellow pigment used on the captain’s hatband is the same (or very similar) to the yellow on his buttons, but different from the yellow on his braiding
Historic Scotland – Pigment analysis
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Royal Armouries Fencing Manual
Back to Index 20
© analytikLtd
Royal Armouries Fencing Manual
Back to Index 20
© analytikLtd
This image shows the redness on the left fighter’s cheek is spectrally the same as the scribbling in the middle of the picture and the spot in the bottom left
Perhaps more importantly, it shows there is nothing else of a similar pigmentation in the whole image
Back to Index 21
Royal Armouries Fencing Manual
© analytikLtd
This image shows the redness on the left fighter’s cheek is spectrally the same as the scribbling in the middle of the picture and the spot in the bottom left
Back to Index 22
Royal Armouries Fencing Manual
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The Videometer can prove this quantitatively as well – the next slide shows the spectral properties of the points in the center of the small crosses below
Back to Index 24
Royal Armouries Fencing Manual
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You can see that 3 and 4 (teal and brown, page and sword) are significantly different from 1 and 2 in terms of their spectral profile.
Back to Index 25
Royal Armouries Fencing Manual
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Visually, the Sten gun looks scratched arbitrarily. In fact, it is known there is an engraving on the side
Royal Armouries Sten Gun
Back to Index 8
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The Videometer can isolate an blow up this engraving
Back to Index 9
Royal Armouries Sten Gun
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The Videometer can also spectrally enhance the contrast
Back to Index 10
Royal Armouries Sten Gun
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Ordinary RGB imaging cannot do this - it is only possible to get the clarity of the enhanced image at 850 nanometers where the scratches start to respond differently to the metal under illumination, and RGB cameras only go up to around 700nm
Back to Index 1
Royal Armouries Sten Gun
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The Videometer can false-colour images to aid understanding
Back to Index 12
Royal Armouries Sten Gun
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It can also focus tightly on specific sections of the image to contrast them better – it is possible to improve signal to noise almost without limit at the expense of spending more time on the analysis
Back to Index 13
Royal Armouries Sten Gun
© analytikLtd
ΧΡΙΣΤΗΦΗΣ ΗΛΙΑ
“Christofis Elias”
Royal Armouries Sten Gun
© analytikLtd
ΛΟΧΟΣ ΣΤ
“Sixth Company”
Royal Armouries Sten Gun
© analytikLtd
ΛΕΥΚΩΣΙΑ
“Lefkosia”
Royal Armouries Sten Gun
© analytikLtd
• The gun belonged to a Greek Cypriot named Elias Christofis who fought in World War II. (Lefkosia is the capital of Cyprus)
• Some of the decisions between similar looking letters might appear odd, but make a lot of sense when looked at multi-spectrally:
– For example, this letter looks like it could easily be a lambda or an aleph, but when viewed at 920 rather than 850nm, the line in the middle disappears
Back to Index 17
Royal Armouries Sten Gun
© analytikLtd
• The translations were done by a Greek-speaker, who said that the transliteration of the third line that was given to her didn’t make sense. Its unclear if that means what Mr Christofis wrote was literally nonsense or if I transliterated it badly, but I would guess the latter
• This could be solved by a more guided transformation process – for example taking a more careful image of the third section of writing, finding out more about the sample so you can ‘guess’ letters and have the Videometer fill in the blanks or by a more complicated transformation calibration
Back to Index 18
Royal Armouries Sten Gun
© analytikLtd
Museum Conservation Service
• Faded ‘Elizabeth R’ signature on official declaration of war communication document to overseas UK forces (sRGB image)
© analytikLtd
• Faded ‘Elizabeth R’ signature on official declaration of war communication document to overseas UK forces (sRGB image)
• Highlight training set of pixels to teach the software the spectral pattern of interest
Museum Conservation Service
Yes
No
© analytikLtd
• Faded ‘Elizabeth R’ signature on official declaration of war communication document to overseas UK forces
• Highlight training set of pixels to teach the software the spectral pattern of interest
• Software scores every pixel in the image using the trained nCDA algorithm
• nCDA score determines pixel false colour value
• Signature’s spectrum is highlighted against all other dis-similar spectra on the page
Museum Conservation Service
© analytikLtd
Museum Conservation Service
• Faded Officer’s co-signature on official declaration of war communication document to overseas UK forces (sRGB image)
© analytikLtd
Museum Conservation Service
• Faded Officer’s co-signature on official declaration of war communication document to overseas UK forces (sRGB image)
• Highlight training set of pixels to teach the software the spectral pattern of interest
Yes
No
© analytikLtd
Museum Conservation Service
• Faded Officer’s co-signature on official declaration of war communication document to overseas UK forces
• Highlight training set of pixels to teach the software the spectral pattern of interest
• Software scores every pixel in the image using the trained nCDA algorithm
• nCDA score determines pixel false colour value
• Signature’s spectrum is highlighted against all other dis-similar spectra on the page
© analytikLtd
Museum Conservation Service
• Faded pencil inscription on the rear of a photograph of unknown British officer in 1858 (sRGB image, date circled)
• Highlight training set of pixels to teach the software the spectral pattern of interest
‘1858’ written in pencil
© analytikLtd
Museum Conservation Service
• Faded pencil inscription on the rear of a photograph of unknown British officer in 1858
• Highlight training set of pixels to teach the software the spectral pattern of interest
• Software scores every pixel in the image using the trained nCDA algorithm
• nCDA score determines pixel false colour value
• Pencil spectrum is highlighted against all other dis-similar spectra on the page
© analytikLtd
Museum Conservation Service
• Suspected signature painted over in final composition
• Almost invisible in sRGB image
© analytikLtd
Museum Conservation Service
• Suspected signature painted over in final composition
• Almost invisible in sRGB image
• Highlight training set of pixels to teach the software the spectral pattern of interest
© analytikLtd
Museum Conservation Service
• Suspected signature painted over in final composition
• Almost invisible in sRGB image
• Highlight training set of pixels to teach the software the spectral pattern of interest
• Software scores every pixel in the image using the trained nCDA algorithm
• nCDA score determines pixel false colour value
• Signature’s spectrum is highlighted against all other dis-similar spectra on the page
© analytikLtd
Multispectral Image Analysis
• A variety of image processing tools are available in VideometerLab’s analysis software
• Analysis protocols and models can be saved and applied to new samples for routine analysis
• Multiple analysis models can be run on the same image data to quantify separate parameters
• Analysis can be batch-run to aid in high-throughput data acquisition
• Image archiving provides a record of samples for future data mining and regulatory compliance
© analytikLtd
• Nuanced, human-like analysis of heterogeneous samples
• Objective, accurate, repeatable measurements
• Non-destructive analysis allows further sample assay work
• No sample preparation is required
• Rapid data acquisition and analysis enables high throughput screening
Why use Multispectral Imaging?
© analytikLtd
• Hardware options
• Emission filter wheel (4 x 25mm Ø) for fluorescence macro-imaging
• Dark- or Bright-field backlighting for scattering or translucency analysis
• Bespoke solutions available
• Software options
• Image Processing Toolbox for filtering and segmentation of image data in individual spectral bands
• Multispectral Imaging Toolbox for multivariate image analysis and modelling
• Blob Toolbox for granular object separation, analysis and data output reporting
• Matlab multispectral imaging toolbox integration
Hardware and Software Options
© analytikLtd
• Nuanced, human-like analysis of heterogeneous samples
• Sophisticated data analysis tools for the novice and power user
• Objective, repeatable data collection with easy export
• Rapid, non-destructive testing with no sample preparation
VL3 Multispectral Imaging
Multispectral imaging at Analytik.co.uk
VL3 Datasheet PDF