Introduction to Image Processingby Andrea Murari1, J.Vega2, T.Craciunescu3D.Mazon4,

L.Gabellieri5, M.Gelfusa6, D.Pacella5, A.Romano5

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6 University of Rome

“Tor Vergata”

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Images in History

Cameras and Images in Societyo One of the characteristics of modern societies is

their ability to easily capture and produce images

o Bidimensional detectors are very common: cellular phones and CCTV cameras most visible applicationso The use of cameras and imaging has become much more widespread in the entire fusion community

oThe new cameras for the operation of JET with the ITER-like wall are more than 30.

oJET Fast Visible camera can produce Gbytes of data per shot (comparable to a 2 hour digital movie)

oThe future of diagnostics for fusion is in the fields of 2-D and even 3-D imaging

Various views on JET

VisibleIR

Plasma Boundary with SXR: the GEM Detector

•Pick-up coils have problems in a radiation hard environment (close to the plasma, integrators etc)•The next generation of plasmas will be so hot that even the boundary will emit in the SXR • Adapt Gas Electron Multiplier detectors

Current~few nACathode

Anode

Preliminary tests on polycapillaries as SXR lenses

Diverging beam (magnification)

Half lens

Parallel beam

Full lens SXR radiography of the mesh (holes 400 m)

SXR image of the mesh with full

lens (magnification ~6 )

Full lens

5.65 cm

27.5 cm

Medipix

X-Ray source F

1

4.4 cm

11.3 cm

F2

80 cm

Humans and Image Processing

Human beings are well equipped to interpret visual data (creature started using visual sensors in the Cambrian Age). 100 Million sensors in each human retina. Optical illusions reveal the active role of the nervous system.

Main Issues

In the case of images captured by cameras what is available is a bidimensional map of pixels with their intensities. Main challenges

a) Share amount of data

b) Ambiguity of visual information

c) Extraction of quantitative information (ill posed problems)

See “Shape” by G.Stiny MIT Press.

Ill-posed Problems

If D is the space of the data or measurements, S the source and A the forward function mapping the reality on the space of the measurements

D= A(S)

The problem of recovering S from D is well posed (accordig to the definition of Hadamard)

o A solution exists for any data D in data space

o The solution is unique in source (image) space S

o The inverse mapping D S is continuous

In general the vast majority on inverse problems involving images in fusion are ill posed

Challenges of image processing

General topics:

o Information retrieval and confidence intervals

o Find solutions to reduce the ill-posed character of the problems

o Extract efficiently physical information

oDevelop solutions compatible with real time control

Information processing capacity of the human brain:

o Conscious reasoning: 16 bits per second

o Mathematical reasoning: 12 bits per second

o Image processing : 10 Megabits per second