Development of broadband multispectral imaging for ... · Spot size analysis of diary products 500...

Development of broadband multispectral imaging

for analysis of dairy products

Ph.D. student Otto H. A. Nielsen

Technical University of Denmark, department of InformaticsCentre for imaging food quality (CIFQ)

VideoMeterNKT - photonics

DANISCO

Photonex 2010 conference on spectral imaging3th November 2010

DTU - Informatics 1/18

Outline

1 SLS based hyperspectral imaging

2 Illumination system

3 Preliminary results

4 Outlook


Outline




4 Outlook


Spectral imaging for food diagnostics



Vision systems

Structural sampleinformation

Characterisation ofbiological samples

Spectroscopy

Chemical analysis



Vision systems

Structural sampleinformation

Characterisation ofbiological samples

Spectroscopy

Chemical analysis

Advantages for food analysis:

Fast

Non-invasive

⇒ Suitable for in line process inspection


Inspection method for homogeneous products milk,

cream, yoghurt etc.

Illumination sources, a collimated beamSub surface light scattering (SLS)



cream, yoghurt etc.


Scattering of biologicalparticles is described myLorentz-Mie theory.



cream, yoghurt etc.


Scattering of biologicalparticles is described myLorentz-Mie theory.

Can determine:

Particle size

Particle concentration

Light absorption

Light scattering


Previous measurements performed by Danisco1.

1On-line monitoring of food processes using subsurface laser scatteringDTU - Informatics 6/18

http://www.strath.ac.uk/Other/cpact/presentations/2009/pdfs/Carstensen.pdf

Previous measurements performed by Danisco1.

The structure of the sample relates it’s optical properties. Thecharacterisation method will be described later.

1On-line monitoring of food processes using subsurface laser scatteringDTU - Informatics 6/18

http://www.strath.ac.uk/Other/cpact/presentations/2009/pdfs/Carstensen.pdf

Outline




4 Outlook


Illumination source

Light generation with a broad spectral profile

SuperK light source

Produces a bright output from 500 nm to 2500 nm, and the beamrequires optical filtering to be used in spectral imaging.


Optical filtering ⇒ hyperspectral beam

Acousto-optical tunable filter (AOTF)

Can cover the spectrum from500 nm to 2500 nm with twoAOTF crystals

Returns two beams, one with visible light and a one for the NIR.


Final light delivery

The light is delivered using an micro structured fiber (LMA5).

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Wavelength [nm]

Bea

m w

aist

[µ

m]

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0.1

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0.5

Wavelength [nm]

beam

pow

er [

mW

]


Schematically setup


Schematically setup

Novel features of the illuminations system

An small fibre output → easy to handle

Collimated Gaussian beam → simple scattering pattern

Broad spectral range (500 nm to 900 nm) → chemicalspecificity

Fast switching of wavelengths → usable for industrialinspection


Outline




4 Outlook


Image example with whole milk, λ = 670 nm


Image example with whole milk, λ = 670 nm

The scattering can be characterised by the slope of the loglogcurve and the spot size of the saturated.


SLS slope characteristics of diary products

500 600 700 800 9000

0.5

1

1.5

2

2.5

3x 10

−3

SLS

Slop

[ar

b. u

nit]

Wavelenght [nm]

Skimmed milk 0.5 %letmælk 1.5%Whole milk 3%

Can discriminate betweenproducts of different fat contents.


SLS slope characteristics of diary products

500 600 700 800 9000

0.5

1

1.5

2

2.5

3x 10

−3

SLS

Slop

[ar

b. u

nit]

Wavelenght [nm]


Can discriminate betweenproducts of different fat contents.

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0.5

1

1.5

2

2.5

3x 10

−3

SLS

Slop

[ar

b. u

nit]

Wavelenght [nm]

yoghurt 3 % fatCream 9 % fatCream 18 % dilutedCream 18 % fat

Different slope for same fatcontents


Spot size analysis of diary products

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siz

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ixel

s]

Wavelenght [nm]




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siz

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ixel

s]Wavelenght [nm]




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siz

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ixel

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Wavelenght [nm]


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ixel

s]Wavelenght [nm]


Line crossings at long wave lengths, showing interesting features.


Outline




4 Outlook


Future implementations

Analyse products with simple changes (fat contents andparticle size). Make correlation between the SLS spectrumand the food property based on statistical models.

Combining the illumination system with a robot to move thefibre. This will make it possible to examine non symmetricscattering distribution and surface reflection.

Perform instrument independent characterisation of thesamples intrinsic scattering parameters.


Acknowledgements

The work presented is sponsored by the The Danish Council forStrategic Research

Coworkers:

Anders Dahl - post.doc. DTU IMM - projectguidance and data analysis

Videometer - imaging equipment and dataanalysis

NKT photonics - construction and tuning of theillumination system

Danisco - introduction to food analysis


Development of broadband multispectral imaging for ... · Spot size analysis of diary products 500...

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