-1- Barcelona, June 27 th, nd ITFG Workshop THz Signal & Image Processing

-2- Barcelona, June 27 th, nd ITFG Workshop Outline SECTION 1: Alternative configurations –Wide beam configuration (synthetic aperture processing) –Tomographic configuration (tomosynthesis processing) SECTION 2: Challenge of data size –Enhanced visualisation –(Semi-) Automatic defect detection

-3- Barcelona, June 27 th, nd ITFG Workshop Outline SECTION 1: Alternative configurations –Wide beam configuration (synthetic aperture processing) –Tomographic configuration (tomosynthesis processing) SECTION 2: Challenge of data amount –Enhanced visualisation –(Semi-) Automatic defect detection

-4- Barcelona, June 27 th, nd ITFG Workshop Wide beam configuration THzTHz THzTHz depth azimuth lenses material under test focused beam unfocused beam Top / overhead view THzTHz THzTHz Beam waist Small focused beam Diffraction-limited Data already focused Lateral resolution: 1-3 mm THzTHz depth azimuth material under test Top / overhead view unfocused beam THzTHz THzTHz THzTHz No lenses needed Wide unfocused beam (16º) Data is focused in software Lateral resolution: 4-7 mm in-depth defects Focused FMCW Synthetic Aperture (SA) FMCW

-5- Barcelona, June 27 th, nd ITFG Workshop 3-D synthetic aperture imagery Inserts - A-sandwich 100 GHz – Side A Near surface Rohacell coreHoneycomb core

-6- Barcelona, June 27 th, nd ITFG Workshop Debonds - A-sandwich - honeycomb core Near surface In depth 100 GHz – Side A 3-D synthetic aperture imagery

-7- Barcelona, June 27 th, nd ITFG Workshop 100 GHz – Side B 150 GHz – Side B Near surface Debonds - A-sandwich - Rohacell core 3-D synthetic aperture imagery

-8- Barcelona, June 27 th, nd ITFG Workshop Near surface Debonds - C-sandwich - honeycomb core 100 GHz – Side B 150 GHz – Side B 3-D synthetic aperture imagery

-9- Barcelona, June 27 th, nd ITFG Workshop 100 GHz – Side A Near surface Impact (30 J) - Solid laminate - fibre glass 100 GHz – Side B 3-D synthetic aperture imagery

-10- Barcelona, June 27 th, nd ITFG Workshop Tomographic configuration Data procedure for 3-D imaging Technique for structural reproduction of object In THz the beam is close to a Gaussian distribution Information from reflected or transmitted beam Process of acquisition/reconstruction Acquisition composed of a set of projections Modeled by the Radon transform Tomosynthesis in transmission mode

-11- Barcelona, June 27 th, nd ITFG Workshop Tomographic configuration Tomosynthesis in reflection mode View A View B View C Reconstruction of internal structure with more accuracy than unique reflection image Allow to converge to diffraction limit for BOTH lateral and longitudinal resolution

-12- Barcelona, June 27 th, nd ITFG Workshop Tomosynthesis Inserts – Solid laminate – Glass fibre 100 GHz – Side A Images at different depths

-13- Barcelona, June 27 th, nd ITFG Workshop Outline SECTION 1: Alternative configurations –Wide beam configuration (synthetic aperture processing) –Tomographic configuration (tomosynthesis processing) SECTION 2: Challenge of data size –Enhanced visualisation –(Semi-) Automatic defect detection

-14- Barcelona, June 27 th, nd ITFG Workshop Challenge of data size FMCW system 3-D data set – spatial information TDS 3-D data set – spatial information 3-D data set – frequency information CHALLENGE FOR THE OPERATOR DOTNAC Enhanced visualisation for flat and curved samples (Semi-) Automatic defect detection

-15- Barcelona, June 27 th, nd ITFG Workshop Defect visualisation Raw image representationProcessed image representation Water inclusion- A-sandwich - Honeycomb core

-16- Barcelona, June 27 th, nd ITFG Workshop Defect visualisation Impact (30 J) - Solid laminate - fibre glass

-17- Barcelona, June 27 th, nd ITFG Workshop Automatic defect detection Inserts - Solid laminate - fibre glass

-18- Barcelona, June 27 th, nd ITFG Workshop Automatic defect detection Inserts - Solid laminate - fibre glass

-19- Barcelona, June 27 th, nd ITFG Workshop 3-D Visualisation In-situ test on radome 3-D In-depth viewing 1 screenshot Imaging with FMCW system

-20- Barcelona, June 27 th, nd ITFG Workshop Questions?

-21- Barcelona, June 27 th, nd ITFG Workshop 21 Questions?

-22- Barcelona, June 27 th, nd ITFG Workshop BFP: Backprojection of Filtered Projections W 0 corresponds to the projection P filtered by a ramp filter to increase details A is the weight coefficient between the projection (θ;ρ) and the pixel (i; j) We sum the filtered projections crossing each point March 6th 2012 Reconstruction methods: BFP

-23- Barcelona, June 27 th, nd ITFG Workshop SART: Simultaneous Algebraic Reconstruction Technique OSEM (Ordered Subsets Expectation Method) Iterative methods