Abstract

Unlike X-ray systems, a terahertz imaging system can distinguish low-density materials in a food matrix. For applying this technique to food inspection, imaging resolution and acquisition speed ought to be simultaneously enhanced. Therefore, we have developed the first continuous-wave sub-terahertz transmission imaging system with a polygonal mirror. Using an f-theta lens and a polygonal mirror, beam scanning is performed over a range of 150 mm. For obtaining transmission images, the line-beam is incorporated with sample translation. The imaging system demonstrates that a pattern with 2.83 mm line-width at 210 GHz can be identified with a scanning speed of 80 mm/s.

© 2015 Optical Society of America

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References

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2014 (2)

G. Ok, H. J. Kim, H. S. Chun, and S. W. Choi, “Foreign-body detection in dry food using continuous sub-terahertz wave imaging,” Food Contr. 42, 284–289 (2014).
[Crossref]

G. Ok, K. Park, H. J. Kim, H. S. Chun, and S. W. Choi, “High-speed terahertz imaging toward food quality inspection,” Appl. Opt. 53(7), 1406–1412 (2014).
[Crossref] [PubMed]

2013 (3)

G. Ok, S. W. Choi, K. H. Park, and H. S. Chun, “Foreign object detection by sub-terahertz quasi-Bessel beam imaging,” Sensors (Basel) 13(1), 71–85 (2013).
[Crossref] [PubMed]

K. Kim, D.-G. Lee, W.-G. Ham, J. Ku, S.-H. Lee, C.-B. Ahn, J.-H. Son, and H. Park, “Adaptive compressed sensing for the fast terahertz reflection tomography,” IEEE Trans. THz, Sci. Tech. (Paris) 4, 395–401 (2013).

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 Contr. 30(2), 531–535 (2013).
[Crossref]

2012 (2)

Y. K. Lee, S. W. Choi, S. T. Han, D. H. Woo, and H. S. Chun, “Detection of foreign bodies in foods using continuous wave terahertz imaging,” J. Food Prot. 75(1), 179–183 (2012).
[Crossref] [PubMed]

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(1), 40–46 (2012).
[Crossref]

2011 (3)

2009 (2)

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(10), 2019–2022 (2009).
[Crossref]

J.-H. Son, “Terahertz electromagnetic interactions with biological matter and their applications,” J. Appl. Phys. 105(10), 102033 (2009).
[Crossref]

2008 (2)

C. Jördens and M. Koch, “Detection of foreign bodies in chocolate with pulsed terahertz spectroscopy,” Opt. Eng. 47(3), 037003 (2008).
[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]

2007 (1)

M. C. Edwards, M. F. Stringer, and The Breakdowns in Food Safety Group, “Observations on patterns in foreign material investigations,” Food Contr. 18(7), 773–782 (2007).
[Crossref]

2006 (1)

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

2000 (1)

Ahn, C. B.

B.-M. Hwang, S. H. Lee, W.-T. Lim, C. B. Ahn, J.-H. Son, and H. Park, “A fast spatial-domain terahertz imaging using block-based compressed sensing,” J. Infrared, Millimeter, Terahertz Waves 32(11), 1328–1336 (2011).
[Crossref]

S. H. Cho, S. H. Lee, C. Nam-Gung, S. J. Oh, J. H. Son, H. Park, and C. B. Ahn, “Fast terahertz reflection tomography using block-based compressed sensing,” Opt. Express 19(17), 16401–16409 (2011).
[Crossref] [PubMed]

Ahn, C.-B.

K. Kim, D.-G. Lee, W.-G. Ham, J. Ku, S.-H. Lee, C.-B. Ahn, J.-H. Son, and H. Park, “Adaptive compressed sensing for the fast terahertz reflection tomography,” IEEE Trans. THz, Sci. Tech. (Paris) 4, 395–401 (2013).

Cho, G. C.

Cho, S. H.

Choi, S. W.

G. Ok, H. J. Kim, H. S. Chun, and S. W. Choi, “Foreign-body detection in dry food using continuous sub-terahertz wave imaging,” Food Contr. 42, 284–289 (2014).
[Crossref]

G. Ok, K. Park, H. J. Kim, H. S. Chun, and S. W. Choi, “High-speed terahertz imaging toward food quality inspection,” Appl. Opt. 53(7), 1406–1412 (2014).
[Crossref] [PubMed]

G. Ok, S. W. Choi, K. H. Park, and H. S. Chun, “Foreign object detection by sub-terahertz quasi-Bessel beam imaging,” Sensors (Basel) 13(1), 71–85 (2013).
[Crossref] [PubMed]

Y. K. Lee, S. W. Choi, S. T. Han, D. H. Woo, and H. S. Chun, “Detection of foreign bodies in foods using continuous wave terahertz imaging,” J. Food Prot. 75(1), 179–183 (2012).
[Crossref] [PubMed]

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 Contr. 30(2), 531–535 (2013).
[Crossref]

Chun, H. S.

G. Ok, H. J. Kim, H. S. Chun, and S. W. Choi, “Foreign-body detection in dry food using continuous sub-terahertz wave imaging,” Food Contr. 42, 284–289 (2014).
[Crossref]

G. Ok, K. Park, H. J. Kim, H. S. Chun, and S. W. Choi, “High-speed terahertz imaging toward food quality inspection,” Appl. Opt. 53(7), 1406–1412 (2014).
[Crossref] [PubMed]

G. Ok, S. W. Choi, K. H. Park, and H. S. Chun, “Foreign object detection by sub-terahertz quasi-Bessel beam imaging,” Sensors (Basel) 13(1), 71–85 (2013).
[Crossref] [PubMed]

Y. K. Lee, S. W. Choi, S. T. Han, D. H. Woo, and H. S. Chun, “Detection of foreign bodies in foods using continuous wave terahertz imaging,” J. Food Prot. 75(1), 179–183 (2012).
[Crossref] [PubMed]

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, M. F. Stringer, and The Breakdowns in Food Safety Group, “Observations on patterns in foreign material investigations,” Food Contr. 18(7), 773–782 (2007).
[Crossref]

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 Contr. 30(2), 531–535 (2013).
[Crossref]

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(1), 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]

Ham, W.-G.

K. Kim, D.-G. Lee, W.-G. Ham, J. Ku, S.-H. Lee, C.-B. Ahn, J.-H. Son, and H. Park, “Adaptive compressed sensing for the fast terahertz reflection tomography,” IEEE Trans. THz, Sci. Tech. (Paris) 4, 395–401 (2013).

Han, P. Y.

Han, S. T.

Y. K. Lee, S. W. Choi, S. T. Han, D. H. Woo, and H. S. Chun, “Detection of foreign bodies in foods using continuous wave terahertz imaging,” J. Food Prot. 75(1), 179–183 (2012).
[Crossref] [PubMed]

Heinen, B.

Hwang, B.-M.

B.-M. Hwang, S. H. Lee, W.-T. Lim, C. B. Ahn, J.-H. Son, and H. Park, “A fast spatial-domain terahertz imaging using block-based compressed sensing,” J. Infrared, Millimeter, Terahertz Waves 32(11), 1328–1336 (2011).
[Crossref]

Jördens, C.

C. Jördens and M. Koch, “Detection of foreign bodies in chocolate with pulsed terahertz spectroscopy,” Opt. Eng. 47(3), 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]

Katletz, S.

Kemp, M. C.

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

Kim, H. J.

G. Ok, H. J. Kim, H. S. Chun, and S. W. Choi, “Foreign-body detection in dry food using continuous sub-terahertz wave imaging,” Food Contr. 42, 284–289 (2014).
[Crossref]

G. Ok, K. Park, H. J. Kim, H. S. Chun, and S. W. Choi, “High-speed terahertz imaging toward food quality inspection,” Appl. Opt. 53(7), 1406–1412 (2014).
[Crossref] [PubMed]

Kim, K.

K. Kim, D.-G. Lee, W.-G. Ham, J. Ku, S.-H. Lee, C.-B. Ahn, J.-H. Son, and H. Park, “Adaptive compressed sensing for the fast terahertz reflection tomography,” IEEE Trans. THz, Sci. Tech. (Paris) 4, 395–401 (2013).

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(23), 23042–23053 (2011).
[PubMed]

C. Jördens and M. Koch, “Detection of foreign bodies in chocolate with pulsed terahertz spectroscopy,” Opt. Eng. 47(3), 037003 (2008).
[Crossref]

Ku, J.

K. Kim, D.-G. Lee, W.-G. Ham, J. Ku, S.-H. Lee, C.-B. Ahn, J.-H. Son, and H. Park, “Adaptive compressed sensing for the fast terahertz reflection tomography,” IEEE Trans. THz, Sci. Tech. (Paris) 4, 395–401 (2013).

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 Contr. 30(2), 531–535 (2013).
[Crossref]

Lee, D.-G.

K. Kim, D.-G. Lee, W.-G. Ham, J. Ku, S.-H. Lee, C.-B. Ahn, J.-H. Son, and H. Park, “Adaptive compressed sensing for the fast terahertz reflection tomography,” IEEE Trans. THz, Sci. Tech. (Paris) 4, 395–401 (2013).

Lee, S. H.

B.-M. Hwang, S. H. Lee, W.-T. Lim, C. B. Ahn, J.-H. Son, and H. Park, “A fast spatial-domain terahertz imaging using block-based compressed sensing,” J. Infrared, Millimeter, Terahertz Waves 32(11), 1328–1336 (2011).
[Crossref]

S. H. Cho, S. H. Lee, C. Nam-Gung, S. J. Oh, J. H. Son, H. Park, and C. B. Ahn, “Fast terahertz reflection tomography using block-based compressed sensing,” Opt. Express 19(17), 16401–16409 (2011).
[Crossref] [PubMed]

Lee, S.-H.

K. Kim, D.-G. Lee, W.-G. Ham, J. Ku, S.-H. Lee, C.-B. Ahn, J.-H. Son, and H. Park, “Adaptive compressed sensing for the fast terahertz reflection tomography,” IEEE Trans. THz, Sci. Tech. (Paris) 4, 395–401 (2013).

Lee, Y. K.

Y. K. Lee, S. W. Choi, S. T. Han, D. H. Woo, and H. S. Chun, “Detection of foreign bodies in foods using continuous wave terahertz imaging,” J. Food Prot. 75(1), 179–183 (2012).
[Crossref] [PubMed]

Lim, W.-T.

B.-M. Hwang, S. H. Lee, W.-T. Lim, C. B. Ahn, J.-H. Son, and H. Park, “A fast spatial-domain terahertz imaging using block-based compressed sensing,” J. Infrared, Millimeter, Terahertz Waves 32(11), 1328–1336 (2011).
[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(10), 2019–2022 (2009).
[Crossref]

Nam-Gung, C.

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 Contr. 30(2), 531–535 (2013).
[Crossref]

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]

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(1), 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(1), 40–46 (2012).
[Crossref]

Oh, S. J.

Ok, G.

G. Ok, H. J. Kim, H. S. Chun, and S. W. Choi, “Foreign-body detection in dry food using continuous sub-terahertz wave imaging,” Food Contr. 42, 284–289 (2014).
[Crossref]

G. Ok, K. Park, H. J. Kim, H. S. Chun, and S. W. Choi, “High-speed terahertz imaging toward food quality inspection,” Appl. Opt. 53(7), 1406–1412 (2014).
[Crossref] [PubMed]

G. Ok, S. W. Choi, K. H. Park, and H. S. Chun, “Foreign object detection by sub-terahertz quasi-Bessel beam imaging,” Sensors (Basel) 13(1), 71–85 (2013).
[Crossref] [PubMed]

Park, H.

K. Kim, D.-G. Lee, W.-G. Ham, J. Ku, S.-H. Lee, C.-B. Ahn, J.-H. Son, and H. Park, “Adaptive compressed sensing for the fast terahertz reflection tomography,” IEEE Trans. THz, Sci. Tech. (Paris) 4, 395–401 (2013).

S. H. Cho, S. H. Lee, C. Nam-Gung, S. J. Oh, J. H. Son, H. Park, and C. B. Ahn, “Fast terahertz reflection tomography using block-based compressed sensing,” Opt. Express 19(17), 16401–16409 (2011).
[Crossref] [PubMed]

B.-M. Hwang, S. H. Lee, W.-T. Lim, C. B. Ahn, J.-H. Son, and H. Park, “A fast spatial-domain terahertz imaging using block-based compressed sensing,” J. Infrared, Millimeter, Terahertz Waves 32(11), 1328–1336 (2011).
[Crossref]

Park, K.

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 (Basel) 13(1), 71–85 (2013).
[Crossref] [PubMed]

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(10), 2019–2022 (2009).
[Crossref]

Scherger, B.

Son, J. H.

Son, J.-H.

K. Kim, D.-G. Lee, W.-G. Ham, J. Ku, S.-H. Lee, C.-B. Ahn, J.-H. Son, and H. Park, “Adaptive compressed sensing for the fast terahertz reflection tomography,” IEEE Trans. THz, Sci. Tech. (Paris) 4, 395–401 (2013).

B.-M. Hwang, S. H. Lee, W.-T. Lim, C. B. Ahn, J.-H. Son, and H. Park, “A fast spatial-domain terahertz imaging using block-based compressed sensing,” J. Infrared, Millimeter, Terahertz Waves 32(11), 1328–1336 (2011).
[Crossref]

J.-H. Son, “Terahertz electromagnetic interactions with biological matter and their applications,” J. Appl. Phys. 105(10), 102033 (2009).
[Crossref]

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(10), 2019–2022 (2009).
[Crossref]

Stringer, M. F.

M. C. Edwards, M. F. Stringer, and The Breakdowns in Food Safety Group, “Observations on patterns in foreign material investigations,” Food Contr. 18(7), 773–782 (2007).
[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. K. Lee, S. W. Choi, S. T. Han, D. H. Woo, and H. S. Chun, “Detection of foreign bodies in foods using continuous wave terahertz imaging,” J. Food Prot. 75(1), 179–183 (2012).
[Crossref] [PubMed]

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(10), 2019–2022 (2009).
[Crossref]

Zhang, X. C.

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(10), 2019–2022 (2009).
[Crossref]

Appl. Opt. (1)

Food Contr. (3)

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 Contr. 30(2), 531–535 (2013).
[Crossref]

M. C. Edwards, M. F. Stringer, and The Breakdowns in Food Safety Group, “Observations on patterns in foreign material investigations,” Food Contr. 18(7), 773–782 (2007).
[Crossref]

G. Ok, H. J. Kim, H. S. Chun, and S. W. Choi, “Foreign-body detection in dry food using continuous sub-terahertz wave imaging,” Food Contr. 42, 284–289 (2014).
[Crossref]

IEEE Trans. THz, Sci. Tech. (Paris) (1)

K. Kim, D.-G. Lee, W.-G. Ham, J. Ku, S.-H. Lee, C.-B. Ahn, J.-H. Son, and H. Park, “Adaptive compressed sensing for the fast terahertz reflection tomography,” IEEE Trans. THz, Sci. Tech. (Paris) 4, 395–401 (2013).

J. Appl. Phys. (1)

J.-H. Son, “Terahertz electromagnetic interactions with biological matter and their applications,” J. Appl. Phys. 105(10), 102033 (2009).
[Crossref]

J. Food Prot. (1)

Y. K. Lee, S. W. Choi, S. T. Han, D. H. Woo, and H. S. Chun, “Detection of foreign bodies in foods using continuous wave terahertz imaging,” J. Food Prot. 75(1), 179–183 (2012).
[Crossref] [PubMed]

J. Infrared, Millimeter, Terahertz Waves (1)

B.-M. Hwang, S. H. Lee, W.-T. Lim, C. B. Ahn, J.-H. Son, and H. Park, “A fast spatial-domain terahertz imaging using block-based compressed sensing,” J. Infrared, Millimeter, Terahertz Waves 32(11), 1328–1336 (2011).
[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(10), 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(3), 037003 (2008).
[Crossref]

Opt. Express (2)

Opt. Lett. (1)

Proc. SPIE (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]

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

Sensors (Basel) (1)

G. Ok, S. W. Choi, K. H. Park, and H. S. Chun, “Foreign object detection by sub-terahertz quasi-Bessel beam imaging,” Sensors (Basel) 13(1), 71–85 (2013).
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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(1), 40–46 (2012).
[Crossref]

Other (4)

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

J.-H. Son, ed., Terahertz Biomedical Science & Technology (CRC Press, Boca Raton, FL., 2014).

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

E. F. Glynn, “efg's Tech Note: USAF 1951 and Microcopy Resolution Test Charts,” http://www.efg2.com/Lab/ImageProcessing/TestTargets/#USAF1951

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Figures (9)

Fig. 1
Fig. 1

(a) Spot diagram of an f-theta lens (black circles denote the Airy disks, and the units are μm). (b) Field curvature and f-theta distortion of the f-theta lens (the vertical axis units are degrees, and the maximum value is 22.5°).

Fig. 2
Fig. 2

(a) A geometrical configuration of a polygonal mirror (facet number N = 6). (b) Perspective view of the polygonal mirror scanner combined with an f-theta lens and a driving brushless direct current (BLDC) motor (N = 4) at a field angle of 0°.

Fig. 3
Fig. 3

Experimental setup for the characterization of the polygonal mirror scanner, which consists of an f-theta lens and a polygonal mirror (N = 4). BLDC: brushless direct current.

Fig. 4
Fig. 4

High-performance continuous-wave (CW) sub-THz transmission imaging system, based on the f-theta scanning lens and the polygonal mirror (N = 4). (a) Right view and (b) front view. PE: polyethylene.

Fig. 5
Fig. 5

The focused beam intensity profiles measured along the Z-axis at 5 different field angles. Here, the x axis in the beam profiles is the vertical direction shown in Fig. 3, corresponding to a slow scan axis, and the y axis is the horizontal direction shown in Fig. 3, corresponding to a fast scan axis. The color of each pixel in the figures represents the beam intensity, with white denoting maximum intensity, black denoting minimum intensity, and yellow and red denoting the in-between values, as shown in the upper color bar and the legend values. These were sequentially used for illustrating the beam intensity in terms of arbitrary units.

Fig. 6
Fig. 6

(a) The best focused beam profile at Z = 164 mm and 0° field (40 × 40 pixels2 with 0.5 mm/pixel resolution), where the beam intensity value is given in arbitrary units. (b) The beam cross sections with their Gaussian fit curves and Huygens point spread function (PSF) cross section, which was calculated by the ray-tracing software.

Fig. 7
Fig. 7

(a) Custom-made resolution chart: chromium patterns on a 2.5 mm thick soda-lime glass. (b) Transmission image (250 × 180 pixels2 with 1.15 mm/pixel resolution) of the custom-made resolution test chart, where intensity values are normalized by the reference signals and the units are percentages. Note that the vertical direction in the transmission images is the fast scan axis, and the horizontal direction is the slow scan axis.

Fig. 8
Fig. 8

Digital photograph of (a) the crickets (35 mm and 50 mm in length, and 5.5 mm and 7 mm in thickness) and (b) the crickets buried in noodle flour. (c) Clipped image from a continuous-wave (CW) sub-THz transmission image by the polygonal mirror scanning method (full-width at half-maximum [FWHM] of a focused beam: 4.13 mm, Frame rate: 0.32 frame/s over 250 × 180 pixels2 with 1.15 mm/pixel resolution), where a unit of the intensity legend is a percentage. (d) A CW sub-THz transmission image obtained by conventional motorized point scanning method (FWHM of a focused beam: 2.65 mm, frame rate: 0.024 frame/min over 160 × 110 pixels2 with 0.5 mm/pixel resolution), where a unit of the intensity legend is arbitrary.

Fig. 9
Fig. 9

(a) Digital photograph of a wrapped chocolate product (packaging material: polyethylene (PE)). (b) Clipped image from a continuous-wave (CW) sub-THz transmission image by the polygonal mirror scanning method, where the intensity legend was skipped for better comparison with its visible image. (c) Digital photograph of the chocolate (138 mm × 50 mm × 5 mm) after removing the wrapper, where some parts of the chocolate are melted.

Equations (8)

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ST=2rsin( A 2 )=2rsin( 180 N ),
η=1 arcsin[ D/ (2rcosβ) ] 180°/N .
Z P = r cosβ [ cos( 180° N )cos2β+ sin 2 β 1 { sin[ ( 180° N )(1η) ] } 2 ],
Y P =rsinβ[ 2cos( 180° N ) 1 { sin[ ( 180° N )(1η) ] } 2 ],
Z G =rcosβ 1 { sin[ ( 180° N )(1η) ] } 2 ,
Y G =rsinβ 1 { sin[ ( 180° N )(1η) ] } 2 .
r= D 2cosβsin[(Aδ)/2] .
DOF=2 z R = 2π ω 0 2 λ =74.84 mm.

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