Abstract

Active millimeter-wave images typically exhibit characteristic speckle noise, due to the coherence of artificial millimeter-wave sources. We study the Hadamard speckle contrast reduction (SCR) technique, which has been successfully used in laser projection systems, in the context of millimeter-wave imaging. We show the impact of Hadamard pattern order and size and of image and pattern resolution on speckle reduction efficiency. Practical limitations of Hadamard pattern implementations and their effect on speckle reduction efficiency are also discussed.

© 2008 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |

  1. J. I. Trisnadi, "Speckle contrast reduction in laser projection displays," Proc. SPIE 4657, 131-137 (2002).
    [CrossRef]
  2. Z.-G. Xia and Y. Sheng, "Radar speckle: noise or information?" in Proceedings of IEEE International Conference on Geoscience and Remote Sensing Symposium IGARSS '96 (IEEE, 1996), Vol. 1, pp. 48-50.
  3. O. Lankoande, M. M. Hayat, and B. Santhanam, "Speckle modeling and reduction in synthetic aperture radar imagery," in Proceedings of IEEE International Conference on Image Processing ICIP 2005 (IEEE, 2005), Vol. 3, pp. 317-320.
  4. R. G. Dantas and E. T. Costa, "Ultrasound speckle reduction using modified Gabor filters," IEEE Trans. Ultrason. Ferroelectr. Freq. Control 54, 530-538 (2007).
    [CrossRef] [PubMed]
  5. D. O. Korneev, L. Yu Bogdanov, and A. V. Nalivkin, "Passive millimeter wave imaging system with white noise illumination for concealed weapons detection," in Conference Digest of IEEE Joint 29th International Conference on Infrared and Millimeter Waves and 12th International Conference on Terahertz Electronics (IEEE, 2004), pp. 741-742.
  6. G. R. Huegenin, 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 1942, 117-128 (1993).
    [CrossRef]
  7. J. I. Trisnadi, "Hadamard speckle contrast reduction," Opt. Lett. 29, 11-13 (2004).
    [CrossRef] [PubMed]
  8. G. Koers, I. Jäger, J. Stiens, and R. Vounckx, "Random phase pattern creation for speckle reduction in active millimeter wave imaging systems," in Proceedings of 4th ESA Workshop on Millimetre Wave Technology and Applications, 8th Topical Symposium on Millimeter Waves TSMMW2006, 7th MINT Millimeter-Wave International Symposium MINT-MIS (ESA, 2006), pp. 423-426.
  9. G. Koers, "Noise Suppression in Active Millimeter Wave Imaging Systems," Ph.D. thesis (Lab for Microelectronics and Photonelectronics, Vrije Universiteit Brussel, 2006).
  10. J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, 1996).
  11. I. Ocket, B. Nauwelaers, G. Koers, and J. Stiens, "Fast modeling and optimization of active millimeter wave imaging systems," in Proceedings of 36th European Microwave Conference (IEEE, 2006), pp. 1559-1562.
  12. V. Tavakol, Q. Feng, I. Ocket, B. Nauwelaers, and D. Schreurs, "System modelling for millimeter-wave imaging systems using a 2.5D calculation method," presented at 37th European Microwave Conference, Munich, Germany, 8-12 October 2007.

2007

R. G. Dantas and E. T. Costa, "Ultrasound speckle reduction using modified Gabor filters," IEEE Trans. Ultrason. Ferroelectr. Freq. Control 54, 530-538 (2007).
[CrossRef] [PubMed]

2004

2002

J. I. Trisnadi, "Speckle contrast reduction in laser projection displays," Proc. SPIE 4657, 131-137 (2002).
[CrossRef]

1993

G. R. Huegenin, 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 1942, 117-128 (1993).
[CrossRef]

IEEE Trans. Ultrason. Ferroelectr. Freq. Control

R. G. Dantas and E. T. Costa, "Ultrasound speckle reduction using modified Gabor filters," IEEE Trans. Ultrason. Ferroelectr. Freq. Control 54, 530-538 (2007).
[CrossRef] [PubMed]

Opt. Lett.

Proc. SPIE

J. I. Trisnadi, "Speckle contrast reduction in laser projection displays," Proc. SPIE 4657, 131-137 (2002).
[CrossRef]

G. R. Huegenin, 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 1942, 117-128 (1993).
[CrossRef]

Other

G. Koers, I. Jäger, J. Stiens, and R. Vounckx, "Random phase pattern creation for speckle reduction in active millimeter wave imaging systems," in Proceedings of 4th ESA Workshop on Millimetre Wave Technology and Applications, 8th Topical Symposium on Millimeter Waves TSMMW2006, 7th MINT Millimeter-Wave International Symposium MINT-MIS (ESA, 2006), pp. 423-426.

G. Koers, "Noise Suppression in Active Millimeter Wave Imaging Systems," Ph.D. thesis (Lab for Microelectronics and Photonelectronics, Vrije Universiteit Brussel, 2006).

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, 1996).

I. Ocket, B. Nauwelaers, G. Koers, and J. Stiens, "Fast modeling and optimization of active millimeter wave imaging systems," in Proceedings of 36th European Microwave Conference (IEEE, 2006), pp. 1559-1562.

V. Tavakol, Q. Feng, I. Ocket, B. Nauwelaers, and D. Schreurs, "System modelling for millimeter-wave imaging systems using a 2.5D calculation method," presented at 37th European Microwave Conference, Munich, Germany, 8-12 October 2007.

Z.-G. Xia and Y. Sheng, "Radar speckle: noise or information?" in Proceedings of IEEE International Conference on Geoscience and Remote Sensing Symposium IGARSS '96 (IEEE, 1996), Vol. 1, pp. 48-50.

O. Lankoande, M. M. Hayat, and B. Santhanam, "Speckle modeling and reduction in synthetic aperture radar imagery," in Proceedings of IEEE International Conference on Image Processing ICIP 2005 (IEEE, 2005), Vol. 3, pp. 317-320.

D. O. Korneev, L. Yu Bogdanov, and A. V. Nalivkin, "Passive millimeter wave imaging system with white noise illumination for concealed weapons detection," in Conference Digest of IEEE Joint 29th International Conference on Infrared and Millimeter Waves and 12th International Conference on Terahertz Electronics (IEEE, 2004), pp. 741-742.

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (11)

Fig. 1
Fig. 1

Hadamard SCR parameters illustrated in a scene configuration. The detector spot has diameter d d , and Hadamard patterns before projection are of size d p × d p (depicted is an arbitrary pattern out of a 4th-order sequence).

Fig. 2
Fig. 2

System setup under consideration.

Fig. 3
Fig. 3

Typical set of simulated speckle images at 100 GHz ( λ = 3 mm ) for one random-phase distribution and N = 4 Hadamard illumination patterns. Physical image size is 25 cm × 25 cm .

Fig. 4
Fig. 4

Optical model used for this study.

Fig. 5
Fig. 5

Averaging of K SCR factors over N speckle patterns. For K object models O i , N subimages are obtained from N illumination patterns P i . These images provide the original and averaged speckle contrasts ( c o ) i and ( c a ) i , respectively. The final SCR factor is the average of K SCR factors r i = ( c o ) i ( c a ) i .

Fig. 6
Fig. 6

Simulated and maximum SCR factor (higher is better) for Hadamard pattern orders N = 4 and N = 16 , with simulated data for detector optics speeds f d 1 , f d 2 , f d 4 , and f d 8 . Pattern projection optics was wavelength limited to f p 0 . Pattern size was chosen as d d × d d before projection and unity magnification, with d d = 2.44 λ f d # .

Fig. 7
Fig. 7

Speckled (top) and despeckled (bottom) images for f d 2 (left) and f d 4 (right) detector optics speeds with pattern order N = 4 . Speckle contrasts are 0.95 (top left), 0.91 (top right), 0.6 (bottom left), and 0.5 (bottom right).

Fig. 8
Fig. 8

Original (top) and projected pattern (bottom) amplitude and phase compared for d p = 4.88 λ and f p 4 projection speed. In the amplitude plots (left), color scaling is white for maximum and black for minimum. In the phase plots (right), black and white are π radians out of phase.

Fig. 9
Fig. 9

SCR factor as a function of projection speed for detector optics speeds f d 1 (left), f d 2 (middle), and f d 4 (right). Simulated curves are for a 4th-order Hadamard pattern sequence (maximum SCR factor 2) with pattern size d d × d d before projection and unity magnification, with d d = 2.44 λ f d # . Curve with markers; simulated SCR factors; solid curves; maximum SCR factors based on solid angle ratio and 4th-order patterns.

Fig. 10
Fig. 10

Fourth-order Hadamard-pattern-based SCR factor as a function of relative pattern size d p d d before projection, where d p is the pattern width/height and d d = 2.44 λ f d # is the diameter of the detector resolution spot. Graphs are for detector projection speeds of f d 1 (left), f d 2 (middle), and f d 4 (right). Pattern projection speed is wavelength limited ( f p 0 ) for detection speeds f d 1 and f d 2 and is f p 2 for f d 4 .

Fig. 11
Fig. 11

Speckle reduction factor for a 4th-order Hadamard pattern sequence as a function of the intrapattern phase difference with f p 1 pattern projection optics, f d 2 detection optics, and unity d p d d .

Equations (1)

Equations on this page are rendered with MathJax. Learn more.

r = c o c a ,

Metrics