Multispectral imaging provides valuable information on the quality and safety of a vast array of materials from pharmaceuticals to raw meat and burned biscuits. The same techniques can be used to measure skin sensitivity to sticking plaster, detect counterfeit drugs and packaging and gain insight into historical artefacts such as medieval manuscripts and weapons. The VideometerLab 3 takes 19 images at 19 specific wavelengths in ultraviolet, visible and infrared light. With multivariate statistical analysis we can reveal hidden patterns in our 19-dimension colour space and find information that would be otherwise 'invisible' to our human eyes.

1. © analytikLtd
analytikLtd
VideometerLab 3 Multi-Spectral Imaging
Rapid Non-destructive Surface Analysis
Adrian Waltho, Analytik Ltd (Cambridge, UK)
adrian.waltho@analytik.co.uk
www.analytik.co.uk/multispectral-imaging
• Light reflectance at separate colours
• Statistical image processing
• Chemical, physical and spatial properties
• Differentiate | Quantify | Report

2. © analytikLtd
Traditional colour imaging uses
three broad bands of colour:
Red, Green and Blue
Normal Colour Imaging

3. © analytikLtd
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

4. © 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

5. © 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

6. © analytikLtd
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

7. © 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

8. © analytikLtd
VideometerLab 3 Schematic

9. Back to Index
Zoom area for
next slide
Bodleian Library – Papyrus Hieroglyphics

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Bodleian Library – Papyrus Hieroglyphics

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a at 850nm
mination (false
note smudge
just above tear
visible in RGB
mage
Bodleian Library – Papyrus Hieroglyphics

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nCDA transformation of same area

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Palimpsest sRGB image
Zoom area for
next slide

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Close-up of zoomed area

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nCDA transform highlights original text

16. © analytikLtd
Historic Scotland – Pigment analysis
Back to Index
• Circled are cadmium red and lead white pigment
samples

17. © analytikLtd Back to Index
• Circled is a mix of cadmium red and lead white
Historic Scotland – Pigment analysis

18. © analytikLtd Back to Index
• The VideometerLab can build up a library of the
spectral responses of each pigment
Historic Scotland – Pigment analysis

19. © 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

20. © 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

21. © analytikLtd Back to Index
• This technique can be applied to paintings, for example
this portrait of a captain from Leith
Historic Scotland – Pigment analysis

22. © analytikLtd Back to Index
• 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

23. © analytikLtd
Royal Armouries Fencing Manual
Back to Index20

24. © analytikLtd
Royal Armouries Fencing Manual
Back to Index20

25. © 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 Index21
Royal Armouries Fencing Manual

26. © 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 Index22
Royal Armouries Fencing Manual

27. © analytikLtd
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 Index24
Royal Armouries Fencing Manual

28. © analytikLtd
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 Index25
Royal Armouries Fencing Manual

29. © analytikLtd
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 Index8

30. © analytikLtd
The Videometer can isolate an blow up this engraving
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Royal Armouries Sten Gun

31. © analytikLtd
The Videometer can also spectrally enhance the contrast
Back to Index10
Royal Armouries Sten Gun

32. © analytikLtd
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 Index1
Royal Armouries Sten Gun

33. © analytikLtd
The Videometer can false-colour images to aid understanding
Back to Index12
Royal Armouries Sten Gun

34. © analytikLtd
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 Index13
Royal Armouries Sten Gun

35. © analytikLtd
ΧΡΙΣΤΗΦΗΣ ΗΛΙΑ
“Christofis Elias”
Royal Armouries Sten Gun

36. © analytikLtd
ΛΟΧΟΣ ΣΤ
“Sixth Company”
Royal Armouries Sten Gun

37. © analytikLtd
ΛΕΥΚΩΣΙΑ
“Lefkosia”
Royal Armouries Sten Gun

38. © 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 Index17
Royal Armouries Sten Gun

39. © 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 Index18
Royal Armouries Sten Gun

40. © analytikLtd
Museum Conservation Service
• Faded ‘Elizabeth R’ signature on
official declaration of war
communication document to
overseas UK forces (sRGB image)

41. © 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

42. © 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

43. © analytikLtd
Museum Conservation Service
• Faded Officer’s co-signature on
official declaration of war
communication document to
overseas UK forces (sRGB image)

44. © 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

45. © 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

46. © 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

47. © 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

48. © analytikLtd
Museum Conservation Service
• Suspected signature painted
over in final composition
• Almost invisible in sRGB image

49. © 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

50. © 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

51. © 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

52. © 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?

53. © 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

54. © 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
adrian.waltho@analytik.co.uk
Multispectral imaging at Analytik.co.uk
VL3 Datasheet PDF