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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

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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