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

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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

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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

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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 by 19
LEDs at points between 375nm-
970nm (UV-Vis-VNIR), strobing
sequentially with precise time
control for known light output
• Integrating sphere diffuses light
onto sample from all angles
• 5 mega-pixel monochrome CCD
camera captures % reflectance
at each LED wavelength for each
image pixel, NIST calibration
• Optional Emission filter wheel
for fluorescence detection and
Bright-field or Dark-field back
lighting
Camera
LEDs
Integrating
sphere
Emission
filter
wheel
Sample

7. © analytikLtd
VideometerLab 3 Schematic
• Precise control at each separate
point of the 375-970nm
spectrum, only possible with
LEDs, allows optimal illumination
for best signal to noise
• Provides calibrated data, suitable
for statistical analysis and
manipulation for discovery
• Emission filters allow additional
multispectral fluorescence
imaging, with excitation at each
LED wavelength
• Powerful, user-friendly hardware
setup and image analysis
software is central to the system
Camera
LEDs
Integrating
sphere
Emission
filter
wheel
Sample

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VideometerLab 3 Schematic

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Simple Colony Counting
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• The VideometerLab can be used as a simple visualisation aid – identify
the strain of microorganism you are interested in and the
VideometerLab will highlight all areas with a similar spectrum

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Simple Colony Counting
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• By producing a binary image, the VideometerLab
can count and quantify those colonies

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Simple Colony Counting
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• VideometerLab has labeled each colony and
generated size data in mm2 for each one

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Complex Colony Counting
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• Because the VideometerLab uses spectral data to characterise colonies of
interest, it is unique in its price band at being able to read plates with two
or more microorganisms growing on them

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Complex Colony Counting
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• These images show the VideometerLab picking out the ‘blue’ and ‘purple’
colonies respectively. This is a simple demonstration that is visually
obvious, but the VideometerLab could be used to distinguish far finer
detail (for example colonies that only differ in their UV absorption)

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Complex Colony Counting
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• The RGB image is in the middle, and the left and right are masks created
by the VideometerLab showing only those colonies it thinks are ‘blue’ on
the left and ‘purple’ on the right

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• sRGB images of skin, little difference
Skin Sensitisation
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Before: No plaster
After: Apply plaster
ten times

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• nCDA mode, difference is great
Skin Sensitisation
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Before: No plaster
After: Apply plaster
ten times

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Skin Sensitisation
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• Allergen testing

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Skin Sensitisation
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Skin Sensitisation
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Skin Sensitisation
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• Increasing the contrast shows the irritation of JB Right