Hadamard speckle contrast reduction (SCR) is considered to be an effective approach to deal with speckle problems in coherent imaging systems. A Hadamard SCR system is divided into two sub-systems, which implement phase patterns projection and reflected waves imaging respectively. The performances of both sub-systems are discussed with numerical simulations and linked to certain parameters so as to give more insights of this approach. For generality, both optical and millimeter wave imaging systems are discussed. To distinguish from former literature based on Fourier optics, the simulation is implemented via wave optics, which is more physical and more accurate. Moreover, considering the fact that the Hadamard method originates from statistics, the effectiveness of Hadamard SCR is in the first place linked to the texture of the object's surface. Statistical optics is also adopted during qualitative analysis of the results. It is shown that the ratio between the dimension of a resolution cell and the granular size of the object's randomly rough surface is closely linked to the performance of Hadamard SCR. Differences in the roughness model in imaging cases of optical and millimeter waves are discussed, which would help to evaluate the validity of the Hadamard SCR approach in practice. The purpose of this paper is to clarify the misunderstandings of Hadamard SCR in previous literature and to give a guideline to apply this approach.
1. Goodman, J. W., Speckle Phenomena in Optics: Theory and Applications, Roberts & Co., Publishers Englewood, CO, 2006.
2. Nascimento, J. C., J. M. Sanches, and J. S. Marques, "Tracking the left ventricle in ultrasound images based on total variation denoising," Lecture Notes in Computer Science, Vol. 4478, 628-636, 2007. doi:10.1007/978-3-540-72849-8_79
3. Xia, Z. G. and Y. Sheng, "Radar speckle: Noise or information?," IEEE International Conference on Geoscience and Remote Sensing Symposium IGARSS, Vol. 1, 48-50, 1996.
4. Huegenin, G. R., C. T. Hsieh, J. E. Kapitzky, E. L. Moore, K. D. Stephan, and A. S. Vickery, "Contraband detection through clothing by means of millimeter wave imaging," Proc. SPIE, Vol. 1942, 117-128, 1993. doi:10.1117/12.160333
5. Koers, G., I. Ocket, F. Qi, V. Tavakol, I. Jager, B. Nauwelaers, and J. Stiens, "Study of active millimeter-wave image speckle reduction by Hadamard phase pattern illumination," Journal of Optical Society America. A, Vol. 25, 312-317, 2008. doi:10.1364/JOSAA.25.000312
6. Trisnadi, J. I., "Hadamard speckle contrast reduction," Optics Letters, Vol. 29, 11-13, 2004. doi:10.1364/OL.29.000011
7. Jager, I., J. Stiens, G. Koers, G. Posen, and R. Vounckx, "Hadamard speckle reduction for millimeter wave imaging," Microwave and Optical Technology Letters, Vol. 48, 1722-1725, 2006. doi:10.1002/mop.21747
8. Islam, S., J. Stiens, G. Poesen, R. Vounckx, J. Peeters, I. Bogaert, D. de Zutter, and W. de Raedt, "Simulation and experimental veri¯cation of W-band ¯nite frequency selective surfaces on in¯nite background with 3D full wave solver NSPWMLFMA ," Progress In Electromagnetics Research, Vol. 101, 189-202, 2010. doi:10.2528/PIER09122104
9. Islam, S., J. Stiens, G. Posen, I. Jager, and R. Vounckx, "Passive frequency selective array as a diffuser for destroying millimeter wave coherence," Active and Passive Electronics Components, Vol. 2008, 1-6, 2008. doi:10.1155/2008/391745
10. Hawit, M. and N. J. A. Sloane, Hadamard Transform Optics, Academic Press Inc., 1979.
11. Trisnadi, J. I., "Speckle contrast reduction in laser projection displays," Proc. SPIE, Vol. 4657, 131-137, 2002. doi:10.1117/12.463781
12. Qi, F., V. Tavakol, I. Ocket, P. Xu, D. Schreurs, J. Wang, and B. Nauwelaers, "Millimeter wave imaging system modeling: spatial frequency domain calculation versus spatial domain calculation ," Journal of Optical Society America. A, Vol. 27, 131-140, 2010. doi:10.1364/JOSAA.27.000131
13. Chen, K. S., L. Tsang, and J. C. Shi, "Microwave emission from two-dimensional inhomogeneous dielectric rough surfaces based on physics-based two-grid method ," Progress In Electromagnetics Research, Vol. 67, 181-203, 2007. doi:10.2528/PIER06082903
14. Oraizi, H. and S. Hosseinzadeh, "A novel marching algorithm for radio wave propagation modeling over rough surfaces," Progress In Electromagnetics Research, Vol. 57, 85-100, 2006. doi:10.2528/PIER05051001
15. Cocheril, Y. and R. Vauzelle, "A new ray-tracing based wave propagation model including rough surfaces scattering," Progress In Electromagnetics Research, Vol. 75, 357-381, 2007. doi:10.2528/PIER07061202
16. Warnick, K. F. and W. C. Chew, "Numerical simulation methods for rough surface scattering," Waves in Random Media, Vol. 11, 1-30, 2001. doi:10.1088/0959-7174/11/1/201
17. Qi, F., V. Tavakol, I. Ocket, D. Schreurs, and B. Nauwelaers, Discussion on the functions of Hadamard phase pattern in millimeter wave imaging , European Radar Conference, 52-55, 2008.
18. Qi, F., I. Ocket, V. Tavakol, D. Schreurs, and B. Nauwelaers, "Millimeter wave imaging: System modeling and phenomena discussion," International Conference on Applied Electromagnetics and Communications (ICEcom) , 1-4, 2007.
19. Appleby, R. and H. B. Wallace, "Standoff detection of weapons and contraband in the 100 GHz to 1 THz region," IEEE Trans. on Antennas and Propagation, Vol. 55, 2944-2956, 2007. doi:10.1109/TAP.2007.908543
20. Rojas, J. A. M., J. Alpuente, E. Bolivar, P. Lopez-Esp, S. Vignote, and M. I. Rojas, "Empirical characterization of wood surfaces by means of iterative autocorrelation of laser speckle patterns," Progress In Electromagnetics Research, Vol. 80, 295-306, 2008. doi:10.2528/PIER07112706
21. Qi, F., V. Tavakol, I. Ocket, S. Islam, I. Jager, D. Schreurs, J. Stiens, and B. Nauwelaers, Hadamard speckle contrast reduction for imaging systems: Comprehension and evaluation, European Radar Conference, 401-404, 2009.
22. Persson, U., "Roughness measurement of machined surfaces by means of the speckle technique in the visible and infrared regions," Optical Engineering, Vol. 32, No. 12, 1993. doi:10.1117/12.151303
23. Qi, F., D. Schreurs, V. Tavakol, and B. Nauwelaers, "Comparison of optical and millimeter wave imaging on speckle," IEEE International Symposium on Antenna and Propagation (AP-S), 1-4, 2008.
24. Ocket, I., B. Nauwelaers, G. Koers, and J. Stiens, Fast modeling and optimization of active millimeter wave imaging systems, European Radar Conference, 1559-1562, 2006.