Abstract

We demonstrate an adaptive reconstruction technique to significantly improve the depth of focus and contrast of three-dimensional reflection-mode terahertz imaging. A laterally scanned virtual transceiver element records reflections from the object of interest. A synthetic aperture focusing technique maintains fine spatial resolution over a large image depth. Measuring the spatial coherence of the received signals across the transceiver aperture provides a non-iterative self-adaptive approach to significantly improve image contrast. Test images show a spatial resolution of 0.4 mm maintained over a 16 mm depth of field, and up to a 30 dB improvement in signal-to-noise ratio.

© 2009 OSA

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  1. W. L. Chan, J. Deibel, and D. M. Mittleman, “Imaging with terahertz radiation,” Rep. Prog. Phys. 70(8), 1325–1379 (2007).
    [CrossRef]
  2. J. O’Hara and D. Grischkowsky, “Quasi-optic synthetic phased-array terahertz imaging,” J. Opt. Soc. Am. B 21(6), 1178–1191 (2004).
    [CrossRef]
  3. T. Buma and T. B. Norris, “Time reversal three-dimensional imaging using single-cycle terahertz pulses,” Appl. Phys. Lett. 84(12), 2196–2198 (2004).
    [CrossRef]
  4. J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications – explosives, weapons, and drugs,” Semicond. Sci. Technol. 20(7), S266–S280 (2005).
    [CrossRef]
  5. H. Zhong, A. Redo-Sanchez, and X.-C. Zhang, “Identification and classification of chemicals using terahertz reflective spectroscopic focal-plane imaging system,” Opt. Express 14(20), 9130–9141 (2006).
    [CrossRef] [PubMed]
  6. C. Baker, T. Lo, W. R. Tribe, B. E. Cole, M. K. Hogbin, and M. C. Kemp, “Detection of concealed explosives at a distance using terahertz technology,” Proc. IEEE 95(8), 1559–1565 (2007).
    [CrossRef]
  7. C. H. Frazier and W. R. O’Brien, “Synthetic aperture techniques with a virtual source element,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 45(1), 196–207 (1998).
    [CrossRef]
  8. P.-C. Li and M.-L. Li, “Adaptive imaging using the generalized coherence factor,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 50(2), 128–141 (2003).
    [CrossRef] [PubMed]
  9. K. W. Hollman, K. W. Rigby, and M. O’Donnell, “Coherence factor of speckle from a multi-row probe,” in Proceedings of the 1999 IEEE Ultrasonics Symposium (IEEE, 1999), pp. 1257–1260.
  10. R. Mallart and M. Fink, “Adaptive focusing in scattering media through sound-speed inhomogeneities: The van Cittert Zernike approach and focusing criterion,” J. Acoust. Soc. Am. 96(6), 3721–3732 (1994).
    [CrossRef]
  11. M. K. Jeong, “A Fourier transform-based sidelobe reduction method in ultrasound imaging,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 47(3), 759–763 (2000).
    [CrossRef]
  12. M.-L. Li, W. J. Guan, and P.-C. Li, “Improved synthetic aperture focusing technique with applications in high-frequency ultrasound imaging,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 51(1), 63–70 (2004).
    [CrossRef] [PubMed]
  13. M.-L. Li, H. E. Zhang, K. Maslov, G. Stoica, and L. V. Wang, “Improved in vivo photoacoustic microscopy based on a virtual-detector concept,” Opt. Lett. 31(4), 474–476 (2006).
    [CrossRef] [PubMed]
  14. M. Karaman, P.-C. Li, and M. O’Donnell, “Synthetic aperture imaging for small scale systems,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 42(3), 429–442 (1995).
    [CrossRef]

2007 (2)

W. L. Chan, J. Deibel, and D. M. Mittleman, “Imaging with terahertz radiation,” Rep. Prog. Phys. 70(8), 1325–1379 (2007).
[CrossRef]

C. Baker, T. Lo, W. R. Tribe, B. E. Cole, M. K. Hogbin, and M. C. Kemp, “Detection of concealed explosives at a distance using terahertz technology,” Proc. IEEE 95(8), 1559–1565 (2007).
[CrossRef]

2006 (2)

2005 (1)

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications – explosives, weapons, and drugs,” Semicond. Sci. Technol. 20(7), S266–S280 (2005).
[CrossRef]

2004 (3)

T. Buma and T. B. Norris, “Time reversal three-dimensional imaging using single-cycle terahertz pulses,” Appl. Phys. Lett. 84(12), 2196–2198 (2004).
[CrossRef]

M.-L. Li, W. J. Guan, and P.-C. Li, “Improved synthetic aperture focusing technique with applications in high-frequency ultrasound imaging,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 51(1), 63–70 (2004).
[CrossRef] [PubMed]

J. O’Hara and D. Grischkowsky, “Quasi-optic synthetic phased-array terahertz imaging,” J. Opt. Soc. Am. B 21(6), 1178–1191 (2004).
[CrossRef]

2003 (1)

P.-C. Li and M.-L. Li, “Adaptive imaging using the generalized coherence factor,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 50(2), 128–141 (2003).
[CrossRef] [PubMed]

2000 (1)

M. K. Jeong, “A Fourier transform-based sidelobe reduction method in ultrasound imaging,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 47(3), 759–763 (2000).
[CrossRef]

1998 (1)

C. H. Frazier and W. R. O’Brien, “Synthetic aperture techniques with a virtual source element,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 45(1), 196–207 (1998).
[CrossRef]

1995 (1)

M. Karaman, P.-C. Li, and M. O’Donnell, “Synthetic aperture imaging for small scale systems,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 42(3), 429–442 (1995).
[CrossRef]

1994 (1)

R. Mallart and M. Fink, “Adaptive focusing in scattering media through sound-speed inhomogeneities: The van Cittert Zernike approach and focusing criterion,” J. Acoust. Soc. Am. 96(6), 3721–3732 (1994).
[CrossRef]

Baker, C.

C. Baker, T. Lo, W. R. Tribe, B. E. Cole, M. K. Hogbin, and M. C. Kemp, “Detection of concealed explosives at a distance using terahertz technology,” Proc. IEEE 95(8), 1559–1565 (2007).
[CrossRef]

Barat, R.

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications – explosives, weapons, and drugs,” Semicond. Sci. Technol. 20(7), S266–S280 (2005).
[CrossRef]

Buma, T.

T. Buma and T. B. Norris, “Time reversal three-dimensional imaging using single-cycle terahertz pulses,” Appl. Phys. Lett. 84(12), 2196–2198 (2004).
[CrossRef]

Chan, W. L.

W. L. Chan, J. Deibel, and D. M. Mittleman, “Imaging with terahertz radiation,” Rep. Prog. Phys. 70(8), 1325–1379 (2007).
[CrossRef]

Cole, B. E.

C. Baker, T. Lo, W. R. Tribe, B. E. Cole, M. K. Hogbin, and M. C. Kemp, “Detection of concealed explosives at a distance using terahertz technology,” Proc. IEEE 95(8), 1559–1565 (2007).
[CrossRef]

Deibel, J.

W. L. Chan, J. Deibel, and D. M. Mittleman, “Imaging with terahertz radiation,” Rep. Prog. Phys. 70(8), 1325–1379 (2007).
[CrossRef]

Federici, J. F.

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications – explosives, weapons, and drugs,” Semicond. Sci. Technol. 20(7), S266–S280 (2005).
[CrossRef]

Fink, M.

R. Mallart and M. Fink, “Adaptive focusing in scattering media through sound-speed inhomogeneities: The van Cittert Zernike approach and focusing criterion,” J. Acoust. Soc. Am. 96(6), 3721–3732 (1994).
[CrossRef]

Frazier, C. H.

C. H. Frazier and W. R. O’Brien, “Synthetic aperture techniques with a virtual source element,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 45(1), 196–207 (1998).
[CrossRef]

Gary, D.

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications – explosives, weapons, and drugs,” Semicond. Sci. Technol. 20(7), S266–S280 (2005).
[CrossRef]

Grischkowsky, D.

Guan, W. J.

M.-L. Li, W. J. Guan, and P.-C. Li, “Improved synthetic aperture focusing technique with applications in high-frequency ultrasound imaging,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 51(1), 63–70 (2004).
[CrossRef] [PubMed]

Hogbin, M. K.

C. Baker, T. Lo, W. R. Tribe, B. E. Cole, M. K. Hogbin, and M. C. Kemp, “Detection of concealed explosives at a distance using terahertz technology,” Proc. IEEE 95(8), 1559–1565 (2007).
[CrossRef]

Huang, F.

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications – explosives, weapons, and drugs,” Semicond. Sci. Technol. 20(7), S266–S280 (2005).
[CrossRef]

Jeong, M. K.

M. K. Jeong, “A Fourier transform-based sidelobe reduction method in ultrasound imaging,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 47(3), 759–763 (2000).
[CrossRef]

Karaman, M.

M. Karaman, P.-C. Li, and M. O’Donnell, “Synthetic aperture imaging for small scale systems,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 42(3), 429–442 (1995).
[CrossRef]

Kemp, M. C.

C. Baker, T. Lo, W. R. Tribe, B. E. Cole, M. K. Hogbin, and M. C. Kemp, “Detection of concealed explosives at a distance using terahertz technology,” Proc. IEEE 95(8), 1559–1565 (2007).
[CrossRef]

Li, M.-L.

M.-L. Li, H. E. Zhang, K. Maslov, G. Stoica, and L. V. Wang, “Improved in vivo photoacoustic microscopy based on a virtual-detector concept,” Opt. Lett. 31(4), 474–476 (2006).
[CrossRef] [PubMed]

M.-L. Li, W. J. Guan, and P.-C. Li, “Improved synthetic aperture focusing technique with applications in high-frequency ultrasound imaging,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 51(1), 63–70 (2004).
[CrossRef] [PubMed]

P.-C. Li and M.-L. Li, “Adaptive imaging using the generalized coherence factor,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 50(2), 128–141 (2003).
[CrossRef] [PubMed]

Li, P.-C.

M.-L. Li, W. J. Guan, and P.-C. Li, “Improved synthetic aperture focusing technique with applications in high-frequency ultrasound imaging,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 51(1), 63–70 (2004).
[CrossRef] [PubMed]

P.-C. Li and M.-L. Li, “Adaptive imaging using the generalized coherence factor,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 50(2), 128–141 (2003).
[CrossRef] [PubMed]

M. Karaman, P.-C. Li, and M. O’Donnell, “Synthetic aperture imaging for small scale systems,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 42(3), 429–442 (1995).
[CrossRef]

Lo, T.

C. Baker, T. Lo, W. R. Tribe, B. E. Cole, M. K. Hogbin, and M. C. Kemp, “Detection of concealed explosives at a distance using terahertz technology,” Proc. IEEE 95(8), 1559–1565 (2007).
[CrossRef]

Mallart, R.

R. Mallart and M. Fink, “Adaptive focusing in scattering media through sound-speed inhomogeneities: The van Cittert Zernike approach and focusing criterion,” J. Acoust. Soc. Am. 96(6), 3721–3732 (1994).
[CrossRef]

Maslov, K.

Mittleman, D. M.

W. L. Chan, J. Deibel, and D. M. Mittleman, “Imaging with terahertz radiation,” Rep. Prog. Phys. 70(8), 1325–1379 (2007).
[CrossRef]

Norris, T. B.

T. Buma and T. B. Norris, “Time reversal three-dimensional imaging using single-cycle terahertz pulses,” Appl. Phys. Lett. 84(12), 2196–2198 (2004).
[CrossRef]

O’Brien, W. R.

C. H. Frazier and W. R. O’Brien, “Synthetic aperture techniques with a virtual source element,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 45(1), 196–207 (1998).
[CrossRef]

O’Donnell, M.

M. Karaman, P.-C. Li, and M. O’Donnell, “Synthetic aperture imaging for small scale systems,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 42(3), 429–442 (1995).
[CrossRef]

O’Hara, J.

Oliveira, F.

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications – explosives, weapons, and drugs,” Semicond. Sci. Technol. 20(7), S266–S280 (2005).
[CrossRef]

Redo-Sanchez, A.

Schulkin, B.

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications – explosives, weapons, and drugs,” Semicond. Sci. Technol. 20(7), S266–S280 (2005).
[CrossRef]

Stoica, G.

Tribe, W. R.

C. Baker, T. Lo, W. R. Tribe, B. E. Cole, M. K. Hogbin, and M. C. Kemp, “Detection of concealed explosives at a distance using terahertz technology,” Proc. IEEE 95(8), 1559–1565 (2007).
[CrossRef]

Wang, L. V.

Zhang, H. E.

Zhang, X.-C.

Zhong, H.

Zimdars, D.

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications – explosives, weapons, and drugs,” Semicond. Sci. Technol. 20(7), S266–S280 (2005).
[CrossRef]

Appl. Phys. Lett. (1)

T. Buma and T. B. Norris, “Time reversal three-dimensional imaging using single-cycle terahertz pulses,” Appl. Phys. Lett. 84(12), 2196–2198 (2004).
[CrossRef]

IEEE Trans. Ultrason. Ferroelectr. Freq. Control (5)

M. K. Jeong, “A Fourier transform-based sidelobe reduction method in ultrasound imaging,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 47(3), 759–763 (2000).
[CrossRef]

M.-L. Li, W. J. Guan, and P.-C. Li, “Improved synthetic aperture focusing technique with applications in high-frequency ultrasound imaging,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 51(1), 63–70 (2004).
[CrossRef] [PubMed]

C. H. Frazier and W. R. O’Brien, “Synthetic aperture techniques with a virtual source element,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 45(1), 196–207 (1998).
[CrossRef]

P.-C. Li and M.-L. Li, “Adaptive imaging using the generalized coherence factor,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 50(2), 128–141 (2003).
[CrossRef] [PubMed]

M. Karaman, P.-C. Li, and M. O’Donnell, “Synthetic aperture imaging for small scale systems,” IEEE Trans. Ultrason. Ferroelectr. Freq. Control 42(3), 429–442 (1995).
[CrossRef]

J. Acoust. Soc. Am. (1)

R. Mallart and M. Fink, “Adaptive focusing in scattering media through sound-speed inhomogeneities: The van Cittert Zernike approach and focusing criterion,” J. Acoust. Soc. Am. 96(6), 3721–3732 (1994).
[CrossRef]

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

Opt. Express (1)

Opt. Lett. (1)

Proc. IEEE (1)

C. Baker, T. Lo, W. R. Tribe, B. E. Cole, M. K. Hogbin, and M. C. Kemp, “Detection of concealed explosives at a distance using terahertz technology,” Proc. IEEE 95(8), 1559–1565 (2007).
[CrossRef]

Rep. Prog. Phys. (1)

W. L. Chan, J. Deibel, and D. M. Mittleman, “Imaging with terahertz radiation,” Rep. Prog. Phys. 70(8), 1325–1379 (2007).
[CrossRef]

Semicond. Sci. Technol. (1)

J. F. Federici, B. Schulkin, F. Huang, D. Gary, R. Barat, F. Oliveira, and D. Zimdars, “THz imaging and sensing for security applications – explosives, weapons, and drugs,” Semicond. Sci. Technol. 20(7), S266–S280 (2005).
[CrossRef]

Other (1)

K. W. Hollman, K. W. Rigby, and M. O’Donnell, “Coherence factor of speckle from a multi-row probe,” in Proceedings of the 1999 IEEE Ultrasonics Symposium (IEEE, 1999), pp. 1257–1260.

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Figures (5)

Fig. 1
Fig. 1

(a) Basic geometry of the virtual transceiver laterally scanned over the object of interest. (b) SAFT involves summing the appropriate signal samples from neighboring elements.

Fig. 2
Fig. 2

High coherence across the transceiver array occurs when the image point coincides with a scattering point within the object. (b) Low coherence occurs when the array is steered away from an actual object point. (c) Low coherence also occurs when the transceiver signals are primarily noise.

Fig. 3
Fig. 3

Wire target images using (a) conventional processing (b) SAFT processing (c) SAFT + CF processing. The most significant improvement in image quality occurs at large image depths.

Fig. 4
Fig. 4

Image quality comparison between no processing (squares), SAFT (circles), and SAFT + CF (triangles). (a) Lateral resolution as a function of depth. (b) SNR as a function of depth.

Fig. 5
Fig. 5

3-D imaging of a needle located 9 mm in front of a razor blade. Separate en face images of the front needle surface and razor blade (a) without processing and (b) with SAFT + CF processing. (c) Three-dimensional stack of SAFT + CF en face images within a 10 x 10 x 10 mm volume.

Equations (2)

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uSAFT=m=1Mum(Δtm)
CF=(m=1Mum(Δtm))2Mm=1Mum(Δtm)2

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