Abstract

In contrast to conventional x-ray food inspection systems that have difficulty in detecting low-density materials, a terahertz imaging system can even identify insects and plastics embedded in a food matrix. A reflection-mode continuous-wave terahertz imaging system was therefore developed for application to food quality inspection, which requires fast, compact, and low-cost detection. High-speed operation of the terahertz imaging system was achieved through the use of a beam-steering tool. A reasonable compromise between the spatial resolution and the scan length of an aspheric f-theta scanning lens could be achieved by optimizing the lens parameters.

© 2014 Optical Society of America

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References

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  1. Y. Lee, S. Choi, S. Han, D. H. Woo, and H. S. Chun, “Detection of foreign bodies in foods using continuous wave terahertz imaging,” J. Food Prot. 75, 179–183 (2012).
    [Crossref]
  2. M. Edwards, ed. Detecting Foreign Bodies in Food (Woodhead, 2004).
  3. M. C. Edwards and M. F. Stringer, and the Breakdowns in Food Safety Group, “Observations on patterns in foreign material investigations,” Food Control 18, 773–782 (2007).
  4. M. S. Nielsen, T. Lauridsen, L. B. Christensen, and R. Feidenhans’l, “X-ray dark-field imaging for detection of foreign bodies in food,” Food Control 30, 531–535 (2013).
  5. P. Y. Han, G. C. Cho, and X. C. Zhang, “Time-domain transillumination of biological tissues with terahertz pulses,” Opt. Lett. 25, 242–244 (2000).
    [Crossref]
  6. M. C. Kemp, “Millimetre wave and terahertz technology for the detection of concealed threats–a review,” Proc. SPIE 6402, 64020D (2006).
    [Crossref]
  7. C. Jördens and M. Koch, “Detection of foreign bodies in chocolate with pulsed terahertz spectroscopy,” Opt. Eng. 47, 037003 (2008).
    [Crossref]
  8. N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. S. Hwang, J. Xu, and X. C. Zhang, “Compact continuous-wave sub-terahertz system for inspection applications,” Appl. Phys. Lett. 86, 054105 (2005).
    [Crossref]
  9. M. Tonouchi, “Cutting-edge terahertz technology,” Nat. Photonics 1, 97–105 (2007).
    [Crossref]
  10. A. A. Gowen, C. O’Sullivan, and C. P. O’Donnell, “Terahertz time domain spectroscopy and imaging: emerging techniques for food process monitoring and quality control,” Trends Food Sci. Technol. 25, 40–46 (2012).
    [Crossref]
  11. B. B. Hu and M. C. Nuss, “Imaging with terahertz waves,” Opt. Lett. 20, 1716–1718 (1995).
    [Crossref]
  12. W. L. Chan, J. Deibel, and D. M. Mittleman, “Imaging with terahertz radiation,” Rept. Progr. Phys. 70, 1325–1379 (2007).
    [Crossref]
  13. G. Ok, S. W. Choi, K. H. Park, and H. S. Chun, “Foreign object detection by sub-terahertz quasi-Bessel beam imaging,” Sensors 13, 71–85 (2013).
  14. T. M. Goyette, J. C. Dickinson, K. J. Linden, W. R. Neal, C. S. Joseph, W. J. Gorveatt, J. Waldman, R. Giles, and W. E. Nixon, “1.56  terahertz 2-frames per second standoff imaging,” Proc. SPIE 6893, 68930J (2008).
    [Crossref]
  15. Q. Song, Y. J. Zhao, A. R. Sanchez, C. L. Zhang, and X. H. Liu, “Fast continuous terahertz wave imaging system for security,” Opt. Commun. 282, 2019–2022 (2009).
    [Crossref]
  16. S. Katletz, M. Pfleger, H. Pühringer, N. Vieweg, B. Scherger, B. Heinen, M. Koch, and K. Wiesauer, “Efficient terahertz en-face imaging,” Opt. Express 19, 23042–23053 (2011).
    [Crossref]
  17. N. Karpowicz, H. Zhong, J. Xu, K. I. Lin, J. S. Hwang, and X. C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20, S293–S299 (2005).
    [Crossref]
  18. L. Thrane, R. H. Jacobsen, P. Uhd Jepsen, and S. R. Keiding, “THz reflection spectroscopy of liquid water,” Chem. Phys. Lett. 240, 330–333 (1995).
    [Crossref]
  19. L. F. Marshall, ed. Handbook of Optical and Laser Scanning (Marcel Dekker, 2004).

2013 (2)

M. S. Nielsen, T. Lauridsen, L. B. Christensen, and R. Feidenhans’l, “X-ray dark-field imaging for detection of foreign bodies in food,” Food Control 30, 531–535 (2013).

G. Ok, S. W. Choi, K. H. Park, and H. S. Chun, “Foreign object detection by sub-terahertz quasi-Bessel beam imaging,” Sensors 13, 71–85 (2013).

2012 (2)

Y. Lee, S. Choi, S. Han, D. H. Woo, and H. S. Chun, “Detection of foreign bodies in foods using continuous wave terahertz imaging,” J. Food Prot. 75, 179–183 (2012).
[Crossref]

A. A. Gowen, C. O’Sullivan, and C. P. O’Donnell, “Terahertz time domain spectroscopy and imaging: emerging techniques for food process monitoring and quality control,” Trends Food Sci. Technol. 25, 40–46 (2012).
[Crossref]

2011 (1)

2009 (1)

Q. Song, Y. J. Zhao, A. R. Sanchez, C. L. Zhang, and X. H. Liu, “Fast continuous terahertz wave imaging system for security,” Opt. Commun. 282, 2019–2022 (2009).
[Crossref]

2008 (2)

T. M. Goyette, J. C. Dickinson, K. J. Linden, W. R. Neal, C. S. Joseph, W. J. Gorveatt, J. Waldman, R. Giles, and W. E. Nixon, “1.56  terahertz 2-frames per second standoff imaging,” Proc. SPIE 6893, 68930J (2008).
[Crossref]

C. Jördens and M. Koch, “Detection of foreign bodies in chocolate with pulsed terahertz spectroscopy,” Opt. Eng. 47, 037003 (2008).
[Crossref]

2007 (3)

W. L. Chan, J. Deibel, and D. M. Mittleman, “Imaging with terahertz radiation,” Rept. Progr. Phys. 70, 1325–1379 (2007).
[Crossref]

M. C. Edwards and M. F. Stringer, and the Breakdowns in Food Safety Group, “Observations on patterns in foreign material investigations,” Food Control 18, 773–782 (2007).

M. Tonouchi, “Cutting-edge terahertz technology,” Nat. Photonics 1, 97–105 (2007).
[Crossref]

2006 (1)

M. C. Kemp, “Millimetre wave and terahertz technology for the detection of concealed threats–a review,” Proc. SPIE 6402, 64020D (2006).
[Crossref]

2005 (2)

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. S. Hwang, J. Xu, and X. C. Zhang, “Compact continuous-wave sub-terahertz system for inspection applications,” Appl. Phys. Lett. 86, 054105 (2005).
[Crossref]

N. Karpowicz, H. Zhong, J. Xu, K. I. Lin, J. S. Hwang, and X. C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20, S293–S299 (2005).
[Crossref]

2000 (1)

1995 (2)

B. B. Hu and M. C. Nuss, “Imaging with terahertz waves,” Opt. Lett. 20, 1716–1718 (1995).
[Crossref]

L. Thrane, R. H. Jacobsen, P. Uhd Jepsen, and S. R. Keiding, “THz reflection spectroscopy of liquid water,” Chem. Phys. Lett. 240, 330–333 (1995).
[Crossref]

Chan, W. L.

W. L. Chan, J. Deibel, and D. M. Mittleman, “Imaging with terahertz radiation,” Rept. Progr. Phys. 70, 1325–1379 (2007).
[Crossref]

Cho, G. C.

Choi, S.

Y. Lee, S. Choi, S. Han, D. H. Woo, and H. S. Chun, “Detection of foreign bodies in foods using continuous wave terahertz imaging,” J. Food Prot. 75, 179–183 (2012).
[Crossref]

Choi, S. W.

G. Ok, S. W. Choi, K. H. Park, and H. S. Chun, “Foreign object detection by sub-terahertz quasi-Bessel beam imaging,” Sensors 13, 71–85 (2013).

Christensen, L. B.

M. S. Nielsen, T. Lauridsen, L. B. Christensen, and R. Feidenhans’l, “X-ray dark-field imaging for detection of foreign bodies in food,” Food Control 30, 531–535 (2013).

Chun, H. S.

G. Ok, S. W. Choi, K. H. Park, and H. S. Chun, “Foreign object detection by sub-terahertz quasi-Bessel beam imaging,” Sensors 13, 71–85 (2013).

Y. Lee, S. Choi, S. Han, D. H. Woo, and H. S. Chun, “Detection of foreign bodies in foods using continuous wave terahertz imaging,” J. Food Prot. 75, 179–183 (2012).
[Crossref]

Deibel, J.

W. L. Chan, J. Deibel, and D. M. Mittleman, “Imaging with terahertz radiation,” Rept. Progr. Phys. 70, 1325–1379 (2007).
[Crossref]

Dickinson, J. C.

T. M. Goyette, J. C. Dickinson, K. J. Linden, W. R. Neal, C. S. Joseph, W. J. Gorveatt, J. Waldman, R. Giles, and W. E. Nixon, “1.56  terahertz 2-frames per second standoff imaging,” Proc. SPIE 6893, 68930J (2008).
[Crossref]

Edwards, M. C.

M. C. Edwards and M. F. Stringer, and the Breakdowns in Food Safety Group, “Observations on patterns in foreign material investigations,” Food Control 18, 773–782 (2007).

Feidenhans’l, R.

M. S. Nielsen, T. Lauridsen, L. B. Christensen, and R. Feidenhans’l, “X-ray dark-field imaging for detection of foreign bodies in food,” Food Control 30, 531–535 (2013).

Giles, R.

T. M. Goyette, J. C. Dickinson, K. J. Linden, W. R. Neal, C. S. Joseph, W. J. Gorveatt, J. Waldman, R. Giles, and W. E. Nixon, “1.56  terahertz 2-frames per second standoff imaging,” Proc. SPIE 6893, 68930J (2008).
[Crossref]

Gorveatt, W. J.

T. M. Goyette, J. C. Dickinson, K. J. Linden, W. R. Neal, C. S. Joseph, W. J. Gorveatt, J. Waldman, R. Giles, and W. E. Nixon, “1.56  terahertz 2-frames per second standoff imaging,” Proc. SPIE 6893, 68930J (2008).
[Crossref]

Gowen, A. A.

A. A. Gowen, C. O’Sullivan, and C. P. O’Donnell, “Terahertz time domain spectroscopy and imaging: emerging techniques for food process monitoring and quality control,” Trends Food Sci. Technol. 25, 40–46 (2012).
[Crossref]

Goyette, T. M.

T. M. Goyette, J. C. Dickinson, K. J. Linden, W. R. Neal, C. S. Joseph, W. J. Gorveatt, J. Waldman, R. Giles, and W. E. Nixon, “1.56  terahertz 2-frames per second standoff imaging,” Proc. SPIE 6893, 68930J (2008).
[Crossref]

Han, P. Y.

Han, S.

Y. Lee, S. Choi, S. Han, D. H. Woo, and H. S. Chun, “Detection of foreign bodies in foods using continuous wave terahertz imaging,” J. Food Prot. 75, 179–183 (2012).
[Crossref]

Heinen, B.

Hu, B. B.

Hwang, J. S.

N. Karpowicz, H. Zhong, J. Xu, K. I. Lin, J. S. Hwang, and X. C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20, S293–S299 (2005).
[Crossref]

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. S. Hwang, J. Xu, and X. C. Zhang, “Compact continuous-wave sub-terahertz system for inspection applications,” Appl. Phys. Lett. 86, 054105 (2005).
[Crossref]

Jacobsen, R. H.

L. Thrane, R. H. Jacobsen, P. Uhd Jepsen, and S. R. Keiding, “THz reflection spectroscopy of liquid water,” Chem. Phys. Lett. 240, 330–333 (1995).
[Crossref]

Jördens, C.

C. Jördens and M. Koch, “Detection of foreign bodies in chocolate with pulsed terahertz spectroscopy,” Opt. Eng. 47, 037003 (2008).
[Crossref]

Joseph, C. S.

T. M. Goyette, J. C. Dickinson, K. J. Linden, W. R. Neal, C. S. Joseph, W. J. Gorveatt, J. Waldman, R. Giles, and W. E. Nixon, “1.56  terahertz 2-frames per second standoff imaging,” Proc. SPIE 6893, 68930J (2008).
[Crossref]

Karpowicz, N.

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. S. Hwang, J. Xu, and X. C. Zhang, “Compact continuous-wave sub-terahertz system for inspection applications,” Appl. Phys. Lett. 86, 054105 (2005).
[Crossref]

N. Karpowicz, H. Zhong, J. Xu, K. I. Lin, J. S. Hwang, and X. C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20, S293–S299 (2005).
[Crossref]

Katletz, S.

Keiding, S. R.

L. Thrane, R. H. Jacobsen, P. Uhd Jepsen, and S. R. Keiding, “THz reflection spectroscopy of liquid water,” Chem. Phys. Lett. 240, 330–333 (1995).
[Crossref]

Kemp, M. C.

M. C. Kemp, “Millimetre wave and terahertz technology for the detection of concealed threats–a review,” Proc. SPIE 6402, 64020D (2006).
[Crossref]

Koch, M.

S. Katletz, M. Pfleger, H. Pühringer, N. Vieweg, B. Scherger, B. Heinen, M. Koch, and K. Wiesauer, “Efficient terahertz en-face imaging,” Opt. Express 19, 23042–23053 (2011).
[Crossref]

C. Jördens and M. Koch, “Detection of foreign bodies in chocolate with pulsed terahertz spectroscopy,” Opt. Eng. 47, 037003 (2008).
[Crossref]

Lauridsen, T.

M. S. Nielsen, T. Lauridsen, L. B. Christensen, and R. Feidenhans’l, “X-ray dark-field imaging for detection of foreign bodies in food,” Food Control 30, 531–535 (2013).

Lee, Y.

Y. Lee, S. Choi, S. Han, D. H. Woo, and H. S. Chun, “Detection of foreign bodies in foods using continuous wave terahertz imaging,” J. Food Prot. 75, 179–183 (2012).
[Crossref]

Lin, K.

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. S. Hwang, J. Xu, and X. C. Zhang, “Compact continuous-wave sub-terahertz system for inspection applications,” Appl. Phys. Lett. 86, 054105 (2005).
[Crossref]

Lin, K. I.

N. Karpowicz, H. Zhong, J. Xu, K. I. Lin, J. S. Hwang, and X. C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20, S293–S299 (2005).
[Crossref]

Linden, K. J.

T. M. Goyette, J. C. Dickinson, K. J. Linden, W. R. Neal, C. S. Joseph, W. J. Gorveatt, J. Waldman, R. Giles, and W. E. Nixon, “1.56  terahertz 2-frames per second standoff imaging,” Proc. SPIE 6893, 68930J (2008).
[Crossref]

Liu, X. H.

Q. Song, Y. J. Zhao, A. R. Sanchez, C. L. Zhang, and X. H. Liu, “Fast continuous terahertz wave imaging system for security,” Opt. Commun. 282, 2019–2022 (2009).
[Crossref]

Mittleman, D. M.

W. L. Chan, J. Deibel, and D. M. Mittleman, “Imaging with terahertz radiation,” Rept. Progr. Phys. 70, 1325–1379 (2007).
[Crossref]

Neal, W. R.

T. M. Goyette, J. C. Dickinson, K. J. Linden, W. R. Neal, C. S. Joseph, W. J. Gorveatt, J. Waldman, R. Giles, and W. E. Nixon, “1.56  terahertz 2-frames per second standoff imaging,” Proc. SPIE 6893, 68930J (2008).
[Crossref]

Nielsen, M. S.

M. S. Nielsen, T. Lauridsen, L. B. Christensen, and R. Feidenhans’l, “X-ray dark-field imaging for detection of foreign bodies in food,” Food Control 30, 531–535 (2013).

Nixon, W. E.

T. M. Goyette, J. C. Dickinson, K. J. Linden, W. R. Neal, C. S. Joseph, W. J. Gorveatt, J. Waldman, R. Giles, and W. E. Nixon, “1.56  terahertz 2-frames per second standoff imaging,” Proc. SPIE 6893, 68930J (2008).
[Crossref]

Nuss, M. C.

O’Donnell, C. P.

A. A. Gowen, C. O’Sullivan, and C. P. O’Donnell, “Terahertz time domain spectroscopy and imaging: emerging techniques for food process monitoring and quality control,” Trends Food Sci. Technol. 25, 40–46 (2012).
[Crossref]

O’Sullivan, C.

A. A. Gowen, C. O’Sullivan, and C. P. O’Donnell, “Terahertz time domain spectroscopy and imaging: emerging techniques for food process monitoring and quality control,” Trends Food Sci. Technol. 25, 40–46 (2012).
[Crossref]

Ok, G.

G. Ok, S. W. Choi, K. H. Park, and H. S. Chun, “Foreign object detection by sub-terahertz quasi-Bessel beam imaging,” Sensors 13, 71–85 (2013).

Park, K. H.

G. Ok, S. W. Choi, K. H. Park, and H. S. Chun, “Foreign object detection by sub-terahertz quasi-Bessel beam imaging,” Sensors 13, 71–85 (2013).

Pfleger, M.

Pühringer, H.

Sanchez, A. R.

Q. Song, Y. J. Zhao, A. R. Sanchez, C. L. Zhang, and X. H. Liu, “Fast continuous terahertz wave imaging system for security,” Opt. Commun. 282, 2019–2022 (2009).
[Crossref]

Scherger, B.

Song, Q.

Q. Song, Y. J. Zhao, A. R. Sanchez, C. L. Zhang, and X. H. Liu, “Fast continuous terahertz wave imaging system for security,” Opt. Commun. 282, 2019–2022 (2009).
[Crossref]

Stringer, M. F.

M. C. Edwards and M. F. Stringer, and the Breakdowns in Food Safety Group, “Observations on patterns in foreign material investigations,” Food Control 18, 773–782 (2007).

Thrane, L.

L. Thrane, R. H. Jacobsen, P. Uhd Jepsen, and S. R. Keiding, “THz reflection spectroscopy of liquid water,” Chem. Phys. Lett. 240, 330–333 (1995).
[Crossref]

Tonouchi, M.

M. Tonouchi, “Cutting-edge terahertz technology,” Nat. Photonics 1, 97–105 (2007).
[Crossref]

Uhd Jepsen, P.

L. Thrane, R. H. Jacobsen, P. Uhd Jepsen, and S. R. Keiding, “THz reflection spectroscopy of liquid water,” Chem. Phys. Lett. 240, 330–333 (1995).
[Crossref]

Vieweg, N.

Waldman, J.

T. M. Goyette, J. C. Dickinson, K. J. Linden, W. R. Neal, C. S. Joseph, W. J. Gorveatt, J. Waldman, R. Giles, and W. E. Nixon, “1.56  terahertz 2-frames per second standoff imaging,” Proc. SPIE 6893, 68930J (2008).
[Crossref]

Wiesauer, K.

Woo, D. H.

Y. Lee, S. Choi, S. Han, D. H. Woo, and H. S. Chun, “Detection of foreign bodies in foods using continuous wave terahertz imaging,” J. Food Prot. 75, 179–183 (2012).
[Crossref]

Xu, J.

N. Karpowicz, H. Zhong, J. Xu, K. I. Lin, J. S. Hwang, and X. C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20, S293–S299 (2005).
[Crossref]

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. S. Hwang, J. Xu, and X. C. Zhang, “Compact continuous-wave sub-terahertz system for inspection applications,” Appl. Phys. Lett. 86, 054105 (2005).
[Crossref]

Zhang, C.

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. S. Hwang, J. Xu, and X. C. Zhang, “Compact continuous-wave sub-terahertz system for inspection applications,” Appl. Phys. Lett. 86, 054105 (2005).
[Crossref]

Zhang, C. L.

Q. Song, Y. J. Zhao, A. R. Sanchez, C. L. Zhang, and X. H. Liu, “Fast continuous terahertz wave imaging system for security,” Opt. Commun. 282, 2019–2022 (2009).
[Crossref]

Zhang, X. C.

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. S. Hwang, J. Xu, and X. C. Zhang, “Compact continuous-wave sub-terahertz system for inspection applications,” Appl. Phys. Lett. 86, 054105 (2005).
[Crossref]

N. Karpowicz, H. Zhong, J. Xu, K. I. Lin, J. S. Hwang, and X. C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20, S293–S299 (2005).
[Crossref]

P. Y. Han, G. C. Cho, and X. C. Zhang, “Time-domain transillumination of biological tissues with terahertz pulses,” Opt. Lett. 25, 242–244 (2000).
[Crossref]

Zhao, Y. J.

Q. Song, Y. J. Zhao, A. R. Sanchez, C. L. Zhang, and X. H. Liu, “Fast continuous terahertz wave imaging system for security,” Opt. Commun. 282, 2019–2022 (2009).
[Crossref]

Zhong, H.

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. S. Hwang, J. Xu, and X. C. Zhang, “Compact continuous-wave sub-terahertz system for inspection applications,” Appl. Phys. Lett. 86, 054105 (2005).
[Crossref]

N. Karpowicz, H. Zhong, J. Xu, K. I. Lin, J. S. Hwang, and X. C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20, S293–S299 (2005).
[Crossref]

Appl. Phys. Lett. (1)

N. Karpowicz, H. Zhong, C. Zhang, K. Lin, J. S. Hwang, J. Xu, and X. C. Zhang, “Compact continuous-wave sub-terahertz system for inspection applications,” Appl. Phys. Lett. 86, 054105 (2005).
[Crossref]

Chem. Phys. Lett. (1)

L. Thrane, R. H. Jacobsen, P. Uhd Jepsen, and S. R. Keiding, “THz reflection spectroscopy of liquid water,” Chem. Phys. Lett. 240, 330–333 (1995).
[Crossref]

Food Control (2)

M. C. Edwards and M. F. Stringer, and the Breakdowns in Food Safety Group, “Observations on patterns in foreign material investigations,” Food Control 18, 773–782 (2007).

M. S. Nielsen, T. Lauridsen, L. B. Christensen, and R. Feidenhans’l, “X-ray dark-field imaging for detection of foreign bodies in food,” Food Control 30, 531–535 (2013).

J. Food Prot. (1)

Y. Lee, S. Choi, S. Han, D. H. Woo, and H. S. Chun, “Detection of foreign bodies in foods using continuous wave terahertz imaging,” J. Food Prot. 75, 179–183 (2012).
[Crossref]

Nat. Photonics (1)

M. Tonouchi, “Cutting-edge terahertz technology,” Nat. Photonics 1, 97–105 (2007).
[Crossref]

Opt. Commun. (1)

Q. Song, Y. J. Zhao, A. R. Sanchez, C. L. Zhang, and X. H. Liu, “Fast continuous terahertz wave imaging system for security,” Opt. Commun. 282, 2019–2022 (2009).
[Crossref]

Opt. Eng. (1)

C. Jördens and M. Koch, “Detection of foreign bodies in chocolate with pulsed terahertz spectroscopy,” Opt. Eng. 47, 037003 (2008).
[Crossref]

Opt. Express (1)

Opt. Lett. (2)

Proc. SPIE (2)

M. C. Kemp, “Millimetre wave and terahertz technology for the detection of concealed threats–a review,” Proc. SPIE 6402, 64020D (2006).
[Crossref]

T. M. Goyette, J. C. Dickinson, K. J. Linden, W. R. Neal, C. S. Joseph, W. J. Gorveatt, J. Waldman, R. Giles, and W. E. Nixon, “1.56  terahertz 2-frames per second standoff imaging,” Proc. SPIE 6893, 68930J (2008).
[Crossref]

Rept. Progr. Phys. (1)

W. L. Chan, J. Deibel, and D. M. Mittleman, “Imaging with terahertz radiation,” Rept. Progr. Phys. 70, 1325–1379 (2007).
[Crossref]

Semicond. Sci. Technol. (1)

N. Karpowicz, H. Zhong, J. Xu, K. I. Lin, J. S. Hwang, and X. C. Zhang, “Comparison between pulsed terahertz time-domain imaging and continuous wave terahertz imaging,” Semicond. Sci. Technol. 20, S293–S299 (2005).
[Crossref]

Sensors (1)

G. Ok, S. W. Choi, K. H. Park, and H. S. Chun, “Foreign object detection by sub-terahertz quasi-Bessel beam imaging,” Sensors 13, 71–85 (2013).

Trends Food Sci. Technol. (1)

A. A. Gowen, C. O’Sullivan, and C. P. O’Donnell, “Terahertz time domain spectroscopy and imaging: emerging techniques for food process monitoring and quality control,” Trends Food Sci. Technol. 25, 40–46 (2012).
[Crossref]

Other (2)

M. Edwards, ed. Detecting Foreign Bodies in Food (Woodhead, 2004).

L. F. Marshall, ed. Handbook of Optical and Laser Scanning (Marcel Dekker, 2004).

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Figures (6)

Fig. 1.
Fig. 1.

(a) Ray-tracing layout of the f -theta scanning lens for CW terahertz imaging. (b) Spot diagram of the f -theta scanning lens (black line circles denote the Airy disks).

Fig. 2.
Fig. 2.

(a) Field curvature and f -theta distortion of the f -theta scanning lens. (b) Cross-sectional plot of the Huygens point spread function (PSF) of the beam spot.

Fig. 3.
Fig. 3.

High-speed CW terahertz imaging setup using an f -theta scanning lens and a galvanometer scanner (reflection geometry). Here, X and Y denote the sample (or chart) translation direction and the beam-scanning direction, respectively.

Fig. 4.
Fig. 4.

Focused beam profiles measured along the y axis and curve fitting.

Fig. 5.
Fig. 5.

(a) Schematic of the custom-made resolution chart (aluminum tape on a 1 mm thick acrylic plate; dimensions: mm). (b) and (c) Reflection images of the custom-made resolution chart with the 5 and 6 mm patterns (b) parallel to the beam-scanning direction and (c) perpendicular to the beam-scanning direction. A single image with a 100 mm × 150 mm scan area and 1 mm / pixel resolution can be obtained in 15 s. Here, X and Y denote the chart translation direction and the beam-scanning direction, respectively. The color scale illustrates the intensity in normalized units.

Fig. 6.
Fig. 6.

(a) Digital photograph of a peanut attached to the acrylic holder, (b) terahertz reflection image of one peanut in a shell, (c) terahertz reflection image of an empty shell, and (d) terahertz reflection image of two peanuts in a shell. The color scale illustrates the intensity in normalized units.

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