Abstract

Imaging concealed objects with millimeter-wave coherent radiation is accompanied by speckle. Like all interference phenomena, speckle depends on three light parameters of the millimeter-wave laser beam—phase, wavelength, and angle of incidence—and can be reduced by the diversity of these three parameters. Diversity tools to improve images of concealed objects have been compared. We report measurements, simulations, and image reconstruction results over the whole W-band (75110GHz) and demonstrate where each tool works the best. Multiphase diversity is successful in reducing speckle contrast: multiangle to improve the image quality, and multispectral to recognize a small object’s features. A simple postprocessing eliminates the areas still covered by interference.

© 2008 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. J. W. Goodman, Speckle Phenomena in Optics: Theory and Applications (Roberts, 2006), p. 387.
  2. J. W. Goodman, “Dependence of image speckle contrast on surface roughness,” Opt. Commun. 14, 323-327 (1975).
    [CrossRef]
  3. J. I. Trisnadi, “Speckle contrast reduction in laser projection displays,” Opt. Lett. 29, 1-13 (2004).
    [CrossRef]
  4. J. I. Trisnadi, “Hadamard speckle contrast reduction,” Opt. Lett. 29, 1-7 (2004).
    [CrossRef]
  5. I. Jaeger, L. Zhang, J. Stiens, H. Sahli, and R. Vounckx, “Millimeter wave inspection of concealed objects,” Microwave Opt. Technol. Lett. 49, 2733-2737 (2007).
    [CrossRef]
  6. I. Jaeger, J. Stiens, G. Koers, G. Poesen, and R. Vounckx, “Speckle reduction in THz imaging systems with multiple phase patterns,” Proc. SPIE 6194, 61940B (2006).
    [CrossRef]
  7. G. Koers, I. Ocket, Q. Feng, V. Tavakol, I. Jäger, B. Nauwelaers, and J. Stiens, “Study of active millimeter wave image speckle reduction by Hadamard phase pattern illumination,” J. Opt. Soc. Am. A 25, 312-317 (2008).
    [CrossRef]
  8. G. Parry, “Some effects of surface roughness on the appearance of speckle in polychromatic light,” Opt. Commun. 12, 75-78 (1974).
    [CrossRef]
  9. P. Goy, “Antenna vector characterization in the mm- and submm-wave regions,” Microwave J. 6, 98-99 (1994).
  10. R. Nothdurft and G. Yao, “Imaging obscured subsurface inhomogenity using laser speckle,” Opt. Express 12, 10034-10039 (2005).
    [CrossRef]

2008 (1)

2007 (1)

I. Jaeger, L. Zhang, J. Stiens, H. Sahli, and R. Vounckx, “Millimeter wave inspection of concealed objects,” Microwave Opt. Technol. Lett. 49, 2733-2737 (2007).
[CrossRef]

2006 (2)

I. Jaeger, J. Stiens, G. Koers, G. Poesen, and R. Vounckx, “Speckle reduction in THz imaging systems with multiple phase patterns,” Proc. SPIE 6194, 61940B (2006).
[CrossRef]

J. W. Goodman, Speckle Phenomena in Optics: Theory and Applications (Roberts, 2006), p. 387.

2005 (1)

R. Nothdurft and G. Yao, “Imaging obscured subsurface inhomogenity using laser speckle,” Opt. Express 12, 10034-10039 (2005).
[CrossRef]

2004 (2)

J. I. Trisnadi, “Speckle contrast reduction in laser projection displays,” Opt. Lett. 29, 1-13 (2004).
[CrossRef]

J. I. Trisnadi, “Hadamard speckle contrast reduction,” Opt. Lett. 29, 1-7 (2004).
[CrossRef]

1994 (1)

P. Goy, “Antenna vector characterization in the mm- and submm-wave regions,” Microwave J. 6, 98-99 (1994).

1975 (1)

J. W. Goodman, “Dependence of image speckle contrast on surface roughness,” Opt. Commun. 14, 323-327 (1975).
[CrossRef]

1974 (1)

G. Parry, “Some effects of surface roughness on the appearance of speckle in polychromatic light,” Opt. Commun. 12, 75-78 (1974).
[CrossRef]

Feng, Q.

Goodman, J. W.

J. W. Goodman, Speckle Phenomena in Optics: Theory and Applications (Roberts, 2006), p. 387.

J. W. Goodman, “Dependence of image speckle contrast on surface roughness,” Opt. Commun. 14, 323-327 (1975).
[CrossRef]

Goy, P.

P. Goy, “Antenna vector characterization in the mm- and submm-wave regions,” Microwave J. 6, 98-99 (1994).

Jaeger, I.

I. Jaeger, L. Zhang, J. Stiens, H. Sahli, and R. Vounckx, “Millimeter wave inspection of concealed objects,” Microwave Opt. Technol. Lett. 49, 2733-2737 (2007).
[CrossRef]

I. Jaeger, J. Stiens, G. Koers, G. Poesen, and R. Vounckx, “Speckle reduction in THz imaging systems with multiple phase patterns,” Proc. SPIE 6194, 61940B (2006).
[CrossRef]

Jäger, I.

Koers, G.

G. Koers, I. Ocket, Q. Feng, V. Tavakol, I. Jäger, B. Nauwelaers, and J. Stiens, “Study of active millimeter wave image speckle reduction by Hadamard phase pattern illumination,” J. Opt. Soc. Am. A 25, 312-317 (2008).
[CrossRef]

I. Jaeger, J. Stiens, G. Koers, G. Poesen, and R. Vounckx, “Speckle reduction in THz imaging systems with multiple phase patterns,” Proc. SPIE 6194, 61940B (2006).
[CrossRef]

Nauwelaers, B.

Nothdurft, R.

R. Nothdurft and G. Yao, “Imaging obscured subsurface inhomogenity using laser speckle,” Opt. Express 12, 10034-10039 (2005).
[CrossRef]

Ocket, I.

Parry, G.

G. Parry, “Some effects of surface roughness on the appearance of speckle in polychromatic light,” Opt. Commun. 12, 75-78 (1974).
[CrossRef]

Poesen, G.

I. Jaeger, J. Stiens, G. Koers, G. Poesen, and R. Vounckx, “Speckle reduction in THz imaging systems with multiple phase patterns,” Proc. SPIE 6194, 61940B (2006).
[CrossRef]

Sahli, H.

I. Jaeger, L. Zhang, J. Stiens, H. Sahli, and R. Vounckx, “Millimeter wave inspection of concealed objects,” Microwave Opt. Technol. Lett. 49, 2733-2737 (2007).
[CrossRef]

Stiens, J.

G. Koers, I. Ocket, Q. Feng, V. Tavakol, I. Jäger, B. Nauwelaers, and J. Stiens, “Study of active millimeter wave image speckle reduction by Hadamard phase pattern illumination,” J. Opt. Soc. Am. A 25, 312-317 (2008).
[CrossRef]

I. Jaeger, L. Zhang, J. Stiens, H. Sahli, and R. Vounckx, “Millimeter wave inspection of concealed objects,” Microwave Opt. Technol. Lett. 49, 2733-2737 (2007).
[CrossRef]

I. Jaeger, J. Stiens, G. Koers, G. Poesen, and R. Vounckx, “Speckle reduction in THz imaging systems with multiple phase patterns,” Proc. SPIE 6194, 61940B (2006).
[CrossRef]

Tavakol, V.

Trisnadi, J. I.

J. I. Trisnadi, “Speckle contrast reduction in laser projection displays,” Opt. Lett. 29, 1-13 (2004).
[CrossRef]

J. I. Trisnadi, “Hadamard speckle contrast reduction,” Opt. Lett. 29, 1-7 (2004).
[CrossRef]

Vounckx, R.

I. Jaeger, L. Zhang, J. Stiens, H. Sahli, and R. Vounckx, “Millimeter wave inspection of concealed objects,” Microwave Opt. Technol. Lett. 49, 2733-2737 (2007).
[CrossRef]

I. Jaeger, J. Stiens, G. Koers, G. Poesen, and R. Vounckx, “Speckle reduction in THz imaging systems with multiple phase patterns,” Proc. SPIE 6194, 61940B (2006).
[CrossRef]

Yao, G.

R. Nothdurft and G. Yao, “Imaging obscured subsurface inhomogenity using laser speckle,” Opt. Express 12, 10034-10039 (2005).
[CrossRef]

Zhang, L.

I. Jaeger, L. Zhang, J. Stiens, H. Sahli, and R. Vounckx, “Millimeter wave inspection of concealed objects,” Microwave Opt. Technol. Lett. 49, 2733-2737 (2007).
[CrossRef]

J. Opt. Soc. Am. A (1)

Microwave J. (1)

P. Goy, “Antenna vector characterization in the mm- and submm-wave regions,” Microwave J. 6, 98-99 (1994).

Microwave Opt. Technol. Lett. (1)

I. Jaeger, L. Zhang, J. Stiens, H. Sahli, and R. Vounckx, “Millimeter wave inspection of concealed objects,” Microwave Opt. Technol. Lett. 49, 2733-2737 (2007).
[CrossRef]

Opt. Commun. (2)

J. W. Goodman, “Dependence of image speckle contrast on surface roughness,” Opt. Commun. 14, 323-327 (1975).
[CrossRef]

G. Parry, “Some effects of surface roughness on the appearance of speckle in polychromatic light,” Opt. Commun. 12, 75-78 (1974).
[CrossRef]

Opt. Express (1)

R. Nothdurft and G. Yao, “Imaging obscured subsurface inhomogenity using laser speckle,” Opt. Express 12, 10034-10039 (2005).
[CrossRef]

Opt. Lett. (2)

J. I. Trisnadi, “Speckle contrast reduction in laser projection displays,” Opt. Lett. 29, 1-13 (2004).
[CrossRef]

J. I. Trisnadi, “Hadamard speckle contrast reduction,” Opt. Lett. 29, 1-7 (2004).
[CrossRef]

Proc. SPIE (1)

I. Jaeger, J. Stiens, G. Koers, G. Poesen, and R. Vounckx, “Speckle reduction in THz imaging systems with multiple phase patterns,” Proc. SPIE 6194, 61940B (2006).
[CrossRef]

Other (1)

J. W. Goodman, Speckle Phenomena in Optics: Theory and Applications (Roberts, 2006), p. 387.

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 (8)

Fig. 1
Fig. 1

Simulation setup to demonstrate Hadamard principles: linear array of four cylinders of radius a and separation A, illuminated with a plane wave of 94 GHz .

Fig. 2
Fig. 2

Coherence effects in setup for Fig. 1: (a) coherent 1-D image, (b) removed with Hadamard averaged image, (c) incoherent image.

Fig. 3
Fig. 3

Frequency-selective surface realization of the simplest Hadamard diffuser.

Fig. 4
Fig. 4

Randomly simulated speckle contrast improvement with two-frequency imaging.

Fig. 5
Fig. 5

Multispectral image of the mechanical Hadamard mask (diameter of holes of 2.35 mm ) with beam waist of 12 mm .

Fig. 6
Fig. 6

Multiangle measurement setup.

Fig. 7
Fig. 7

Multiangle speckle contrast by imaging of two metal stripes: (a) central image C ( 0 ° ) = 0.957 , (b) C ( 5 ° ) = 0.774 , (c) C ( 5 ° ) = 0.790 ; (d) speckle contrast of averaged image C = 0.754 .

Fig. 8
Fig. 8

Averaged multispectral image and a corresponding speckle contrast image.

Equations (4)

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

H 1 = [ 1 1 1 1 ] , H 2 = [ 1 1 1 1 ] , H 3 = [ 1 1 1 1 ] , H 4 = [ 1 1 1 1 ] ,
φ i j 1 = k r = 2 π ( { D λ 1 } + y i j λ 1 ) ,
Δ φ i j k = 2 π ( { D λ k } { D λ 1 } + y i j λ k λ 1 λ k λ 1 ) .
C i j = 1 N k = 1 , N ( X i , j k X i , j k ¯ ) 2 X i , j k ¯ ,

Metrics