Abstract

A thickness measurement system is proposed for in-line inspection of thickness variation of flat glass panels. Multi-reflection on the surfaces of glass panel generates an interference signal whose phase is proportional to the thickness of the glass panel. For accurate and stable calculation of the phase value, we obtain quadrature interference signals using a current modulation technique. The proposed system can measure a thickness profile with high speed and nanometric resolution, and obtain higher accuracy through real-time nonlinear error compensation. The thickness profile, measured by a transmissive-type experimental setup, coincided with a comparative result obtained using a contact-type thickness measurement system within the range of ±40nm. The standard deviations of the measured thickness profiles and their waviness components were less than 3 nm with a scanning speed of 300mm/s.

© 2014 Optical Society of America

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References

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  1. J. C. Lapp, “AMLCD substrates trends in technology,” http://www.corning.com/WorkArea/showcontent.aspx?id=52639 .
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  4. V. Protopopov, S. Cho, K. Kim, S. Lee, H. Kim, and D. Kim, “Heterodyne double-channel polarimeter for mapping birefringence and thickness of flat glass panels,” Rev. Sci. Instrum. 77, 053107 (2006).
    [CrossRef]
  5. V. Protopopov, S. Cho, K. Kim, S. Lee, and H. Kim, “Differential heterodyne interferometer for measuring thickness of glass panels,” Rev. Sci. Instrum. 78, 076101 (2007).
    [CrossRef]
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    [CrossRef]
  8. G. R. Fowles, “Interference with multiple beams,” in Introduction to Modern Optics, 2nd ed. (Holt, Rinehart & Winston, 1975), pp. 86–90.
  9. C.-M. Wu, C.-S. Su, and G.-S. Peng, “Correction of nonlinearity in one-frequency optical interferometry,” Meas. Sci. Technol. 7, 520–524 (1996).
    [CrossRef]
  10. J.-A. Kim, J. W. Kim, C.-S. Kang, T. B. Eom, and J. Ahn, “A digital signal processing module for real-time compensation of nonlinearity in a homodyne interferometer using a field-programmable gate array,” Meas. Sci. Technol. 20, 017003 (2009).
    [CrossRef]
  11. A. Godina, B. Acko, and M. Druzovec, “New approach to uncertainty evaluation in the calibration of gauge block comparators,” Measurement 40, 607–614 (2007).
    [CrossRef]
  12. , Geometrical Product Specifications (GPS)—Surface texture: Profile method—Terms, definitions and surface texture parameters (1997).
  13. , Geometrical product specifications (GPS)—Filtration—Part 21: Linear profile filters: Gaussian filters (2011).

2014 (1)

2009 (1)

J.-A. Kim, J. W. Kim, C.-S. Kang, T. B. Eom, and J. Ahn, “A digital signal processing module for real-time compensation of nonlinearity in a homodyne interferometer using a field-programmable gate array,” Meas. Sci. Technol. 20, 017003 (2009).
[CrossRef]

2008 (2)

2007 (2)

V. Protopopov, S. Cho, K. Kim, S. Lee, and H. Kim, “Differential heterodyne interferometer for measuring thickness of glass panels,” Rev. Sci. Instrum. 78, 076101 (2007).
[CrossRef]

A. Godina, B. Acko, and M. Druzovec, “New approach to uncertainty evaluation in the calibration of gauge block comparators,” Measurement 40, 607–614 (2007).
[CrossRef]

2006 (1)

V. Protopopov, S. Cho, K. Kim, S. Lee, H. Kim, and D. Kim, “Heterodyne double-channel polarimeter for mapping birefringence and thickness of flat glass panels,” Rev. Sci. Instrum. 77, 053107 (2006).
[CrossRef]

2001 (1)

1996 (1)

C.-M. Wu, C.-S. Su, and G.-S. Peng, “Correction of nonlinearity in one-frequency optical interferometry,” Meas. Sci. Technol. 7, 520–524 (1996).
[CrossRef]

Acko, B.

A. Godina, B. Acko, and M. Druzovec, “New approach to uncertainty evaluation in the calibration of gauge block comparators,” Measurement 40, 607–614 (2007).
[CrossRef]

Ahn, J.

J.-A. Kim, J. W. Kim, C.-S. Kang, T. B. Eom, and J. Ahn, “A digital signal processing module for real-time compensation of nonlinearity in a homodyne interferometer using a field-programmable gate array,” Meas. Sci. Technol. 20, 017003 (2009).
[CrossRef]

Cho, S.

V. Protopopov, S. Cho, K. Kim, S. Lee, and H. Kim, “Differential heterodyne interferometer for measuring thickness of glass panels,” Rev. Sci. Instrum. 78, 076101 (2007).
[CrossRef]

V. Protopopov, S. Cho, K. Kim, S. Lee, H. Kim, and D. Kim, “Heterodyne double-channel polarimeter for mapping birefringence and thickness of flat glass panels,” Rev. Sci. Instrum. 77, 053107 (2006).
[CrossRef]

Druzovec, M.

A. Godina, B. Acko, and M. Druzovec, “New approach to uncertainty evaluation in the calibration of gauge block comparators,” Measurement 40, 607–614 (2007).
[CrossRef]

Eom, T. B.

J.-A. Kim, J. W. Kim, T. B. Eom, J. Jin, and C.-S. Kang, “Vibration-insensitive measurement of thickness variation of glass panels using double-slit interferometry,” Opt. Express 22, 6486–6494 (2014).
[CrossRef]

J.-A. Kim, J. W. Kim, C.-S. Kang, T. B. Eom, and J. Ahn, “A digital signal processing module for real-time compensation of nonlinearity in a homodyne interferometer using a field-programmable gate array,” Meas. Sci. Technol. 20, 017003 (2009).
[CrossRef]

Fowles, G. R.

G. R. Fowles, “Interference with multiple beams,” in Introduction to Modern Optics, 2nd ed. (Holt, Rinehart & Winston, 1975), pp. 86–90.

Godina, A.

A. Godina, B. Acko, and M. Druzovec, “New approach to uncertainty evaluation in the calibration of gauge block comparators,” Measurement 40, 607–614 (2007).
[CrossRef]

Jin, J.

Kang, C.-S.

J.-A. Kim, J. W. Kim, T. B. Eom, J. Jin, and C.-S. Kang, “Vibration-insensitive measurement of thickness variation of glass panels using double-slit interferometry,” Opt. Express 22, 6486–6494 (2014).
[CrossRef]

J.-A. Kim, J. W. Kim, C.-S. Kang, T. B. Eom, and J. Ahn, “A digital signal processing module for real-time compensation of nonlinearity in a homodyne interferometer using a field-programmable gate array,” Meas. Sci. Technol. 20, 017003 (2009).
[CrossRef]

Kim, D.

V. Protopopov, S. Cho, K. Kim, S. Lee, H. Kim, and D. Kim, “Heterodyne double-channel polarimeter for mapping birefringence and thickness of flat glass panels,” Rev. Sci. Instrum. 77, 053107 (2006).
[CrossRef]

Kim, H.

V. Protopopov, S. Cho, K. Kim, S. Lee, and H. Kim, “Differential heterodyne interferometer for measuring thickness of glass panels,” Rev. Sci. Instrum. 78, 076101 (2007).
[CrossRef]

V. Protopopov, S. Cho, K. Kim, S. Lee, H. Kim, and D. Kim, “Heterodyne double-channel polarimeter for mapping birefringence and thickness of flat glass panels,” Rev. Sci. Instrum. 77, 053107 (2006).
[CrossRef]

Kim, J. W.

J.-A. Kim, J. W. Kim, T. B. Eom, J. Jin, and C.-S. Kang, “Vibration-insensitive measurement of thickness variation of glass panels using double-slit interferometry,” Opt. Express 22, 6486–6494 (2014).
[CrossRef]

J.-A. Kim, J. W. Kim, C.-S. Kang, T. B. Eom, and J. Ahn, “A digital signal processing module for real-time compensation of nonlinearity in a homodyne interferometer using a field-programmable gate array,” Meas. Sci. Technol. 20, 017003 (2009).
[CrossRef]

Kim, J.-A.

J.-A. Kim, J. W. Kim, T. B. Eom, J. Jin, and C.-S. Kang, “Vibration-insensitive measurement of thickness variation of glass panels using double-slit interferometry,” Opt. Express 22, 6486–6494 (2014).
[CrossRef]

J.-A. Kim, J. W. Kim, C.-S. Kang, T. B. Eom, and J. Ahn, “A digital signal processing module for real-time compensation of nonlinearity in a homodyne interferometer using a field-programmable gate array,” Meas. Sci. Technol. 20, 017003 (2009).
[CrossRef]

Kim, K.

V. Protopopov, S. Cho, K. Kim, S. Lee, and H. Kim, “Differential heterodyne interferometer for measuring thickness of glass panels,” Rev. Sci. Instrum. 78, 076101 (2007).
[CrossRef]

V. Protopopov, S. Cho, K. Kim, S. Lee, H. Kim, and D. Kim, “Heterodyne double-channel polarimeter for mapping birefringence and thickness of flat glass panels,” Rev. Sci. Instrum. 77, 053107 (2006).
[CrossRef]

Kim, M. J.

Kim, S.

Lee, B. H.

Lee, S.

V. Protopopov, S. Cho, K. Kim, S. Lee, and H. Kim, “Differential heterodyne interferometer for measuring thickness of glass panels,” Rev. Sci. Instrum. 78, 076101 (2007).
[CrossRef]

V. Protopopov, S. Cho, K. Kim, S. Lee, H. Kim, and D. Kim, “Heterodyne double-channel polarimeter for mapping birefringence and thickness of flat glass panels,” Rev. Sci. Instrum. 77, 053107 (2006).
[CrossRef]

Li, Z.-H.

Liu, C.-H.

Na, J.

Nen, J.

Peiponen, K. E.

Peng, G.-S.

C.-M. Wu, C.-S. Su, and G.-S. Peng, “Correction of nonlinearity in one-frequency optical interferometry,” Meas. Sci. Technol. 7, 520–524 (1996).
[CrossRef]

Protopopov, V.

V. Protopopov, S. Cho, K. Kim, S. Lee, and H. Kim, “Differential heterodyne interferometer for measuring thickness of glass panels,” Rev. Sci. Instrum. 78, 076101 (2007).
[CrossRef]

V. Protopopov, S. Cho, K. Kim, S. Lee, H. Kim, and D. Kim, “Heterodyne double-channel polarimeter for mapping birefringence and thickness of flat glass panels,” Rev. Sci. Instrum. 77, 053107 (2006).
[CrossRef]

Su, C.-S.

C.-M. Wu, C.-S. Su, and G.-S. Peng, “Correction of nonlinearity in one-frequency optical interferometry,” Meas. Sci. Technol. 7, 520–524 (1996).
[CrossRef]

Wu, C.-M.

C.-M. Wu, C.-S. Su, and G.-S. Peng, “Correction of nonlinearity in one-frequency optical interferometry,” Meas. Sci. Technol. 7, 520–524 (1996).
[CrossRef]

Appl. Opt. (2)

Meas. Sci. Technol. (2)

C.-M. Wu, C.-S. Su, and G.-S. Peng, “Correction of nonlinearity in one-frequency optical interferometry,” Meas. Sci. Technol. 7, 520–524 (1996).
[CrossRef]

J.-A. Kim, J. W. Kim, C.-S. Kang, T. B. Eom, and J. Ahn, “A digital signal processing module for real-time compensation of nonlinearity in a homodyne interferometer using a field-programmable gate array,” Meas. Sci. Technol. 20, 017003 (2009).
[CrossRef]

Measurement (1)

A. Godina, B. Acko, and M. Druzovec, “New approach to uncertainty evaluation in the calibration of gauge block comparators,” Measurement 40, 607–614 (2007).
[CrossRef]

Opt. Express (2)

Rev. Sci. Instrum. (2)

V. Protopopov, S. Cho, K. Kim, S. Lee, H. Kim, and D. Kim, “Heterodyne double-channel polarimeter for mapping birefringence and thickness of flat glass panels,” Rev. Sci. Instrum. 77, 053107 (2006).
[CrossRef]

V. Protopopov, S. Cho, K. Kim, S. Lee, and H. Kim, “Differential heterodyne interferometer for measuring thickness of glass panels,” Rev. Sci. Instrum. 78, 076101 (2007).
[CrossRef]

Other (4)

, Geometrical Product Specifications (GPS)—Surface texture: Profile method—Terms, definitions and surface texture parameters (1997).

, Geometrical product specifications (GPS)—Filtration—Part 21: Linear profile filters: Gaussian filters (2011).

G. R. Fowles, “Interference with multiple beams,” in Introduction to Modern Optics, 2nd ed. (Holt, Rinehart & Winston, 1975), pp. 86–90.

J. C. Lapp, “AMLCD substrates trends in technology,” http://www.corning.com/WorkArea/showcontent.aspx?id=52639 .

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Figures (7)

Fig. 1.
Fig. 1.

Multiple reflections on both surfaces of an uncoated glass panel generate a sinusoidal interference signal of the transmitted beams.

Fig. 2.
Fig. 2.

Quadrature interference signals can be obtained by switching the wavelength of the laser using current modulation. At each data acquisition step (m=1,2), the interference signals are acquired synchronously with the current modulation signal, and then collected separately to construct the complete quadrature signals. The interference signals obtained at the (2m1)th (red circle) and (2m)th (blue square) acquisition step compose IT2 (upper dotted line) and IT1 (lower dotted line), respectively.

Fig. 3.
Fig. 3.

Schematic of the experimental setup. LD, laser diode; OF, optical fiber; CL, collimation lens; L1, L2, lens composing relay optics; GP, glass panel; MS, motorized stage; PH, pinhole; PD, photodiode; SA, scaling amplifier; PC, personal computer; and FPGA board, field-programmable gate array board.

Fig. 4.
Fig. 4.

(a) Exemplary quadrature interference signals according to thickness variation of a glass plate. (b) Wrapped and unwrapped phases obtained using the quadrature signals.

Fig. 5.
Fig. 5.

(a) Variation of the parameter values of the quadrature interference signals when incorrect initial values are assigned intentionally. The dotted lines show the comparative parameter values calculated using the elliptical fitting method. (b) Lissajous figures plotted with the compensated quadrature signals before and after the start of real-time compensation.

Fig. 6.
Fig. 6.

Comparison of thickness profiles and filtered profiles obtained by the quadrature interferometer and the contact-type thickness measurement system; (a) thickness profiles and difference and (b) filtered thickness profiles and differences.

Fig. 7.
Fig. 7.

Comparison of thickness profiles and filtered profiles measured when the glass plate was translated with speeds of 10mm/s and 300mm/s; (a) thickness profiles and differences and (b) filtered thickness profiles and differences.

Equations (12)

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

IT=I0T2(1R)211+Fsin2ϕ2=2I0T2(2+F)(1R)211F2+Fcosϕ,
IT2I0T2(2+F)(1R)2(1+F2+Fcosϕ).
ϕ=4πndλ,
4πn2dλ2=4πn1dλ1π2,
IT1=2I01T2(2+F)(1R)2(1+F2+Fcos4πn1dλ1),
IT2=2I02T2(2+F)(1R)2(1+F2+Fcos4πn2dλ2)=2I02T2(2+F)(1R)2(1+F2+Fsin4πn1dλ1).
Δλλ¯28n¯d,
IT1=A1+B1cos(ϕ+δ2),
IT2=A2+B2sin(ϕδ2).
ϕ=tan1[tanδ2B2(IT1A1)+B1(IT2A2)B2(IT1A1)+tanδ2B1(IT2A2)].
IT1,i=A1[1+(F2+F)cos(ϕi+δ2)+(F2+F)2cos2(ϕi1+δ2)],
IT2,i=A2[1+(F2+F)sin(ϕiδ2)+(F2+F)2sin2(ϕi1δ2)],

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