Abstract

We propose a paintmeter for noncontact and remote monitoring of the thickness and drying progress of a paint film based on the time-of-flight measurement of the echo signal of a terahertz (THz) electromagnetic pulse. The proposed method is effectively applied to two-dimensional mapping of the painting thickness distribution for single-layer and multilayer paint films. Furthermore, adequate parameters for the drying progress are extracted from the THz pulse-echo signal and effectively applied to monitor the wet-to-dry transformation. The THz paintmeter can be a powerful tool for quality control of the paint film on the in-process monitoring of car body painting.

© 2005 Optical Society of America

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References

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  1. For example, see http://www.kett.co.jp/e/products/pro3/lu200.html .
  2. For example, see http://www.kett.co.jp/e/products/pro3/lh200c.html .
  3. For example, see http://www.kett.co.jp/e/products/pro3/le200c.html .
  4. J. Ying, F. Liu, P. P. Ho, R. R. Alfano, “Nondestructive evaluation of incident corrosion in a metal beneath paint by second-harmonic tomography,” Opt. Lett. 25, 1189–1191 (2000).
    [CrossRef]
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    [CrossRef]
  6. D. M. Mittleman, R. H. Jacobsen, M. C. Nuss, “T-ray imaging,” IEEE J. Sel. Top. Quantum Electron. 2, 679–692 (1996).
    [CrossRef]
  7. D. M. Mittleman, S. Hunsche, L. Boivin, M. C. Nuss, “T-ray tomography,” Opt. Lett. 22, 904–906 (1997).
    [CrossRef] [PubMed]
  8. T. Yasui, T. Araki, “Dependence of terahertz electric field on electric bias and modulation frequency in pulsed terahertz emission from electrically-modulated photoconductive antenna detected with free-space electro-optic sampling,” Jpn. J. Appl. Phys. 44, 1777–1780 (2005).
    [CrossRef]
  9. D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, J. G. Fujimoto, “Optical coherence tomography,” Science 254, 1178–1181 (1991).
    [CrossRef] [PubMed]
  10. T. Yasui, T. Mitsunari, T. Araki, “Measurement of thickness and dry-state of the paint film using THz electromagnetic pulse,” in Abstract of the Ninth International Workshop on Femtosecond Technology, M. Nakazawa, ed. (Femtosecond Technology Research Association, 2002), p. 182.
  11. T. Yasui, T. Yasuda, T. Araki, “Real-time two-dimensional terahertz tomography,” in Proceedings of the Joint 30th International Conference on Infrared and Millimeter Waves and 13th International Conference on Terahertz Electronics, K. J. Button, ed. (IEEE, 2005), p. 580–581.
  12. T. Yasuda, T. Yasui, T. Araki, E. Abraham, “Real-time two-dimensional terahertz tomography for in-process terahertz paintmeter,” submitted to Opt. Lett.
  13. T. Yasui, E. Saneyoshi, T. Araki, “Asynchronous optical sampling terahertz time-domain spectroscopy for ultrahigh spectral-resolution and rapid data acquisition,” Appl. Phys. Lett. 87061101 (2005).
    [CrossRef]

2005

T. Yasui, T. Araki, “Dependence of terahertz electric field on electric bias and modulation frequency in pulsed terahertz emission from electrically-modulated photoconductive antenna detected with free-space electro-optic sampling,” Jpn. J. Appl. Phys. 44, 1777–1780 (2005).
[CrossRef]

T. Yasui, E. Saneyoshi, T. Araki, “Asynchronous optical sampling terahertz time-domain spectroscopy for ultrahigh spectral-resolution and rapid data acquisition,” Appl. Phys. Lett. 87061101 (2005).
[CrossRef]

2000

1997

1996

D. M. Mittleman, R. H. Jacobsen, M. C. Nuss, “T-ray imaging,” IEEE J. Sel. Top. Quantum Electron. 2, 679–692 (1996).
[CrossRef]

1991

D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, J. G. Fujimoto, “Optical coherence tomography,” Science 254, 1178–1181 (1991).
[CrossRef] [PubMed]

1984

D. H. Auston, K. P. Cheung, P. R. Smith, “Picosecond photoconducting Hertzian dipoles,” Appl. Phys. Lett. 45, 284–286 (1984).
[CrossRef]

Abraham, E.

T. Yasuda, T. Yasui, T. Araki, E. Abraham, “Real-time two-dimensional terahertz tomography for in-process terahertz paintmeter,” submitted to Opt. Lett.

Alfano, R. R.

Araki, T.

T. Yasui, T. Araki, “Dependence of terahertz electric field on electric bias and modulation frequency in pulsed terahertz emission from electrically-modulated photoconductive antenna detected with free-space electro-optic sampling,” Jpn. J. Appl. Phys. 44, 1777–1780 (2005).
[CrossRef]

T. Yasui, E. Saneyoshi, T. Araki, “Asynchronous optical sampling terahertz time-domain spectroscopy for ultrahigh spectral-resolution and rapid data acquisition,” Appl. Phys. Lett. 87061101 (2005).
[CrossRef]

T. Yasui, T. Yasuda, T. Araki, “Real-time two-dimensional terahertz tomography,” in Proceedings of the Joint 30th International Conference on Infrared and Millimeter Waves and 13th International Conference on Terahertz Electronics, K. J. Button, ed. (IEEE, 2005), p. 580–581.

T. Yasuda, T. Yasui, T. Araki, E. Abraham, “Real-time two-dimensional terahertz tomography for in-process terahertz paintmeter,” submitted to Opt. Lett.

T. Yasui, T. Mitsunari, T. Araki, “Measurement of thickness and dry-state of the paint film using THz electromagnetic pulse,” in Abstract of the Ninth International Workshop on Femtosecond Technology, M. Nakazawa, ed. (Femtosecond Technology Research Association, 2002), p. 182.

Auston, D. H.

D. H. Auston, K. P. Cheung, P. R. Smith, “Picosecond photoconducting Hertzian dipoles,” Appl. Phys. Lett. 45, 284–286 (1984).
[CrossRef]

Boivin, L.

Chang, W.

D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, J. G. Fujimoto, “Optical coherence tomography,” Science 254, 1178–1181 (1991).
[CrossRef] [PubMed]

Cheung, K. P.

D. H. Auston, K. P. Cheung, P. R. Smith, “Picosecond photoconducting Hertzian dipoles,” Appl. Phys. Lett. 45, 284–286 (1984).
[CrossRef]

Flotte, T.

D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, J. G. Fujimoto, “Optical coherence tomography,” Science 254, 1178–1181 (1991).
[CrossRef] [PubMed]

Fujimoto, J. G.

D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, J. G. Fujimoto, “Optical coherence tomography,” Science 254, 1178–1181 (1991).
[CrossRef] [PubMed]

Gregory, K.

D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, J. G. Fujimoto, “Optical coherence tomography,” Science 254, 1178–1181 (1991).
[CrossRef] [PubMed]

Hee, M. R.

D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, J. G. Fujimoto, “Optical coherence tomography,” Science 254, 1178–1181 (1991).
[CrossRef] [PubMed]

Ho, P. P.

Huang, D.

D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, J. G. Fujimoto, “Optical coherence tomography,” Science 254, 1178–1181 (1991).
[CrossRef] [PubMed]

Hunsche, S.

Jacobsen, R. H.

D. M. Mittleman, R. H. Jacobsen, M. C. Nuss, “T-ray imaging,” IEEE J. Sel. Top. Quantum Electron. 2, 679–692 (1996).
[CrossRef]

Lin, C. P.

D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, J. G. Fujimoto, “Optical coherence tomography,” Science 254, 1178–1181 (1991).
[CrossRef] [PubMed]

Liu, F.

Mitsunari, T.

T. Yasui, T. Mitsunari, T. Araki, “Measurement of thickness and dry-state of the paint film using THz electromagnetic pulse,” in Abstract of the Ninth International Workshop on Femtosecond Technology, M. Nakazawa, ed. (Femtosecond Technology Research Association, 2002), p. 182.

Mittleman, D. M.

D. M. Mittleman, S. Hunsche, L. Boivin, M. C. Nuss, “T-ray tomography,” Opt. Lett. 22, 904–906 (1997).
[CrossRef] [PubMed]

D. M. Mittleman, R. H. Jacobsen, M. C. Nuss, “T-ray imaging,” IEEE J. Sel. Top. Quantum Electron. 2, 679–692 (1996).
[CrossRef]

Nuss, M. C.

D. M. Mittleman, S. Hunsche, L. Boivin, M. C. Nuss, “T-ray tomography,” Opt. Lett. 22, 904–906 (1997).
[CrossRef] [PubMed]

D. M. Mittleman, R. H. Jacobsen, M. C. Nuss, “T-ray imaging,” IEEE J. Sel. Top. Quantum Electron. 2, 679–692 (1996).
[CrossRef]

Puliafito, C. A.

D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, J. G. Fujimoto, “Optical coherence tomography,” Science 254, 1178–1181 (1991).
[CrossRef] [PubMed]

Saneyoshi, E.

T. Yasui, E. Saneyoshi, T. Araki, “Asynchronous optical sampling terahertz time-domain spectroscopy for ultrahigh spectral-resolution and rapid data acquisition,” Appl. Phys. Lett. 87061101 (2005).
[CrossRef]

Schuman, J. S.

D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, J. G. Fujimoto, “Optical coherence tomography,” Science 254, 1178–1181 (1991).
[CrossRef] [PubMed]

Smith, P. R.

D. H. Auston, K. P. Cheung, P. R. Smith, “Picosecond photoconducting Hertzian dipoles,” Appl. Phys. Lett. 45, 284–286 (1984).
[CrossRef]

Stinson, W. G.

D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, J. G. Fujimoto, “Optical coherence tomography,” Science 254, 1178–1181 (1991).
[CrossRef] [PubMed]

Swanson, E. A.

D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, J. G. Fujimoto, “Optical coherence tomography,” Science 254, 1178–1181 (1991).
[CrossRef] [PubMed]

Yasuda, T.

T. Yasui, T. Yasuda, T. Araki, “Real-time two-dimensional terahertz tomography,” in Proceedings of the Joint 30th International Conference on Infrared and Millimeter Waves and 13th International Conference on Terahertz Electronics, K. J. Button, ed. (IEEE, 2005), p. 580–581.

T. Yasuda, T. Yasui, T. Araki, E. Abraham, “Real-time two-dimensional terahertz tomography for in-process terahertz paintmeter,” submitted to Opt. Lett.

Yasui, T.

T. Yasui, E. Saneyoshi, T. Araki, “Asynchronous optical sampling terahertz time-domain spectroscopy for ultrahigh spectral-resolution and rapid data acquisition,” Appl. Phys. Lett. 87061101 (2005).
[CrossRef]

T. Yasui, T. Araki, “Dependence of terahertz electric field on electric bias and modulation frequency in pulsed terahertz emission from electrically-modulated photoconductive antenna detected with free-space electro-optic sampling,” Jpn. J. Appl. Phys. 44, 1777–1780 (2005).
[CrossRef]

T. Yasui, T. Mitsunari, T. Araki, “Measurement of thickness and dry-state of the paint film using THz electromagnetic pulse,” in Abstract of the Ninth International Workshop on Femtosecond Technology, M. Nakazawa, ed. (Femtosecond Technology Research Association, 2002), p. 182.

T. Yasui, T. Yasuda, T. Araki, “Real-time two-dimensional terahertz tomography,” in Proceedings of the Joint 30th International Conference on Infrared and Millimeter Waves and 13th International Conference on Terahertz Electronics, K. J. Button, ed. (IEEE, 2005), p. 580–581.

T. Yasuda, T. Yasui, T. Araki, E. Abraham, “Real-time two-dimensional terahertz tomography for in-process terahertz paintmeter,” submitted to Opt. Lett.

Ying, J.

Appl. Phys. Lett.

T. Yasui, E. Saneyoshi, T. Araki, “Asynchronous optical sampling terahertz time-domain spectroscopy for ultrahigh spectral-resolution and rapid data acquisition,” Appl. Phys. Lett. 87061101 (2005).
[CrossRef]

D. H. Auston, K. P. Cheung, P. R. Smith, “Picosecond photoconducting Hertzian dipoles,” Appl. Phys. Lett. 45, 284–286 (1984).
[CrossRef]

IEEE J. Sel. Top. Quantum Electron.

D. M. Mittleman, R. H. Jacobsen, M. C. Nuss, “T-ray imaging,” IEEE J. Sel. Top. Quantum Electron. 2, 679–692 (1996).
[CrossRef]

Jpn. J. Appl. Phys.

T. Yasui, T. Araki, “Dependence of terahertz electric field on electric bias and modulation frequency in pulsed terahertz emission from electrically-modulated photoconductive antenna detected with free-space electro-optic sampling,” Jpn. J. Appl. Phys. 44, 1777–1780 (2005).
[CrossRef]

Opt. Lett.

Science

D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, J. G. Fujimoto, “Optical coherence tomography,” Science 254, 1178–1181 (1991).
[CrossRef] [PubMed]

Other

T. Yasui, T. Mitsunari, T. Araki, “Measurement of thickness and dry-state of the paint film using THz electromagnetic pulse,” in Abstract of the Ninth International Workshop on Femtosecond Technology, M. Nakazawa, ed. (Femtosecond Technology Research Association, 2002), p. 182.

T. Yasui, T. Yasuda, T. Araki, “Real-time two-dimensional terahertz tomography,” in Proceedings of the Joint 30th International Conference on Infrared and Millimeter Waves and 13th International Conference on Terahertz Electronics, K. J. Button, ed. (IEEE, 2005), p. 580–581.

T. Yasuda, T. Yasui, T. Araki, E. Abraham, “Real-time two-dimensional terahertz tomography for in-process terahertz paintmeter,” submitted to Opt. Lett.

For example, see http://www.kett.co.jp/e/products/pro3/lu200.html .

For example, see http://www.kett.co.jp/e/products/pro3/lh200c.html .

For example, see http://www.kett.co.jp/e/products/pro3/le200c.html .

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Figures (9)

Fig. 1
Fig. 1

Principle of the THz paintmeter. (a) Single-layer paint film and (b) temporal waveform of THz pulse echo.

Fig. 2
Fig. 2

Experimental setup. ML Ti:S laser, mode-locked Ti:sapphire laser; BS, beam splitter; L, lens; PCA, photoconductive antenna; SiL, hemispherical silicon lens; OAP1, OAP2, and OAP3, off-axis parabolic mirrors; ZnTe, zinc telluride crystal; FODL, fast optical delay line; CR, corner reflector; P, polarizer; λ/4, quarter-wave plate; RP, Rochon prism; AB-PD, autobalanced photoreceiver; LIA, lock-in amplifier; OSC, oscillator; AMP, amplifier.

Fig. 3
Fig. 3

Relationship between painting thickness and delay time of THz pulse echoes (or optical thickness). The solid lines were obtained from the linear approximation of the data as y = αx, where y is the optical thickness, α is the slope constant (group refractive index), and x is the painting thickness (geometric thickness).

Fig. 4
Fig. 4

Pulse-echo signal of a single-layer metallic paint film. (a) THz paintmeter and (b) OCT. The thickness of the paint film samples is 436 µm for the THz paintmeter and 103 µm for the OCT.

Fig. 5
Fig. 5

Shown is the 2D distribution of the painting thickness for a single-layer WE paint film. PX and PY indicate the X and Y coordinates of the sample position, respectively.

Fig. 6
Fig. 6

Shown is the 2D distribution of painting thickness for a two-layer paint film on a nonmetal substrate. (a) Sample, (b) impulse response of the THz echo-pulse train, (c) 2D distribution of the individual painting thickness. The difference of the ng values at the air–BA, BA–WE, and WE–substrate boundaries are approximately 0.8.

Fig. 7
Fig. 7

Detection of the partial paint-off area. (a) Sample and (b) 2D distribution of the paint-off area. The paint-off area with the maximum air gap of 555 µm is observed within the area PX = 2.5−10 mm.

Fig. 8
Fig. 8

Temporal evolution of a THz pulse-echo signal before and after painting. The drying process is almost completed after 10 min.

Fig. 9
Fig. 9

Monitoring of the drying process. (a) Parameter of THz pulse-echo signal; (b) temporal change of t1, t2, and (t2t1) values; (c) temporal change of pulse-echo contrast (PEC). The t1, and (t2t1) values relate to the geometric thickness and optical thickness of the paint film, respectively. The PEC value is defined as PEC = (E2Ebottom)/(E2 + Ebottom).

Tables (3)

Tables Icon

Table 1 Applicability of Conventional Thickness Meters

Tables Icon

Table 2 Basic Performance of the Present System

Tables Icon

Table 3 Components of Resin and Pigment, Applicability of THz Paintmeter and OCT, and Group Refractive Indices in the THz Region with Respect to Five Kinds of Car Body Paints

Equations (2)

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Δ t = ( 2 n g d ) / c ,
d min = ( c Δ T ) / ( 2 n g ) ,

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