Compressive THz Imaging and Hadamard Spectroscopy for Space Applications THz Imaging

1. Programme for Research-Development-Innovation for Space Technology and Advanced Research - STAR Compressive THz Imaging and Hadamard Spectroscopy for Space ApplicationsTHz Imaging Florin Garoi Romanian Space Week , 12-16 May 2014, Bucharest, Romania

2. Partners • Coordinating organization National Institute for Laser, Plasma and Radiation Physics (INFLPR) 409 Atomistilor Street, PO Box MG-36, 077125 Magurele, Ilfov, Romania • Project manager Florin Garoi INFLPR Tel/Fax: +40 21 4574467 E-mail: florin.garoi@inflpr.ro Web: http://ila.inflpr.ro • Partner organization University Politehnica of Bucharest – Research Center for Spatial Information (CEO Space Tech) 1-3 Iuliu Maniu Bd, Bucharest, Romania • Partner team leader Daniela Coltuc CEO Space Tech Tel: +40 21 4024873 E-mail: daniela.coltuc@upb.ro Web: http://www.cespacetech.pub.ro

3. The project • Short description of the project • spectroscopy and imaging at THz wavelength range (0.1 – 30 THz); • Hadamard spectroscopy • Compressive sensing (CS) imaging • Project goal • Experimental model of Hadamard spectrometer and CS imaging system in THz domain, for Space Applications

4. Work plan of the project * with gray are already completed activities

5. Implementation status • Characterization of the components in the experimental setup Experimental model v1.0: • FIR 100 laser (Edinburgh Instruments); l = 118.83 mm, 133.1 mm, and 163 mm • Mirrors • Dispersive component: • reflective blaze diffraction grating • transmission diffraction grating (wire or machine cut) • prism • Digital Micromirror Device (DMD) • Detector Software: • LabView • CS • Laser • CO2 section: 80 lines between 9.1μm and 10.9μm 50W on the strongest lines • CO2 laser output is coupled into the FIR laser via two steering mirrors and a ZnSe focusing lens • FIR section: • 118.83mm (150mW), 133.1mm (1mW), and 163mm (36mW) • Installation and training

6. Implementation status • Optical components • Off-axis parabolic mirrors: f = 250mm (Laser Beam Products, UK) • Lenses: f = 50mm, 100mm, 200mm (Tydex, Russia) • Reflective blaze diffraction grating: Brass (CNC EUROMOD-P), coated with 50nm layer of gold (Varian RF magnetron sputtering) Dimensions: 20mm × 20mm × 5mm Grating pitch: 120 mm  not feasible 300 mm  in the making Cross-section of the blaze grating Grating cross-section Blaze wavelength as a function of the incidence angle.

7. Implementation status • Wire transmission diffraction grating: Brass frame and nickel wire Dimensions: 50mm × 50mm × 10mm Grating active area: 40mm × 40mm Wire diameter: 200mm Grating pitch: 400mm • Polyethylene prisms: Prism angle: 60, 50 and 40 Wavelength as a function of diffraction angle (first diffraction order) Measured with Tera View systems, TPS Spectra 3000 Deviation d versus angle of incidence a

8. Implementation status • Digital Micromirror Device, DAQ and Detector: • Projection of masks and acquisition  integrated in LabView • Tested in visible range of the spectrum • Testing with various random matrices generation for CS • Find a sensing matrix through random methods that accurately reproduces a given image and scaling for a finer resolution with more samples or larger sensors coverage; for example Low Density Parity Check (LDPC) matrices

9. Results • Physical Fourier encoding of optical data • Preliminary tests of the dispersive elements, in visible and THz range Initial objects Experimental setup Decoded images

10. Results One Pixel Camera for THz Image AcquisitionDesign and Tests of Camera Software EXPERIMENTAL RESULTS ACQUISITIONPRINCIPLE: Compressive Sensing (CS) SCOPE: finding the appropriate couple Sensing Matrix – Transform for CS Algorithm METHOD: couple evaluation by Rate-Distortion curve EXPERIMENTS: Test images (numerical): Cameraman and Lena Tested Sensing matrices: Binary Random Binary Sparse LDPC (Low Density Parity Code) Tested Transforms: Discrete Cosine Transform Wavelet Transform TV (Total Variation) Rate-Distortion curves for TV SOFTWARE: CS Toolbox at http://w3.impa.br/~aschulz/CS/CS-codes.zip L1 Magic at http://www.cms.caltech.edu/ FOUND SOLUTION: LDPC with TV Rate-Distortion curves for LDPC

11. Project contribution to STAR Programme • Project’s contribution to the goal of the STAR Programme (how the project contributes to the increasing of the capacity for organizations involved to participate in ESA Programmes) The project addresses Basic Technology Research Programme (TRP), one of ESA’s activities regarding technology and research → may facilitate strong and long-term relations between Romanian entities and ESA. • Context and contribution to ESA Programmes (please specify how the project activities can contributes to present and future ESA programmes) We hope that our research on THz imaging with CS and Hadamard spectroscopy contribute to the development of new instruments required for the current and long-term ESA science directorate programme.

12. Dissemination Publications and Conferences • Rate-Distortion Performance of Compressive Sensing in One Pixel Camera,Mihai Petrovici, Daniela Coltuc, Mihai Datcu, and Vasile Tiberius, Submitted to IEEE Signal processing Letters  • Physical Fourier encoding and compacting of optical data, Petre Catalin Logofatu, Florin Garoi, Victor Damian and Cristian Udrea, Submitted to Optical Engineering • Terahertz range complex refractive index determinations for liquids using ATR, Adrian Dobroiu and Petre Catalin Logofatu, Submitted to Optical Engineering • Introduction to CompressiveSampling and applications in THz Imaging,Daniela Coltuc,Invited paper to ATOM-N 2014 Conference (Constanta, August 21-24, 2014) • Dispersive elements for THz domain, V. Damian, Mihaela Bojan, G. D. Chioibasu, F. Garoi, P. C. Logofatu, L. Mihai, C. Udrea, I. Urzica, T. Vasile, and C. Viespe, will be presented at INDLAS 2014 Conference (Bran , May 19-23, 2014) • Synthetic aperture and scarsity analysis methods for THz imaging, Mihai-Alexandru Petrovici, will be presented at the European Conference on Computer Vision (Zurich, September 6-12, 2014) • L1 minimization applied to the simple case of a sparse signal consisting in a sum of sinusoids, Petre Catalin Logofatu, will be presented at ATOM-N Conference (Constanta, August 21-24, 2014) Technical Notes within the consortium (available upon request) For up-to-date info, please visit our webpage: http://ila.inflpr.ro/THzImaging

13. Conclusions • Conclusions • All tasks and activities completed as scheduled Most important results: • Installation and training for the THz laser • Simulation of the experimental setup v1.0 • Characterization of some of the components • Definition of the CS matrices and algorithms for data processing