Abstract

A two-dimensional noncontact optical fiber water droplet sensor that uses the fluorescence from a laser-diode-pumped Tm3+:YAG and that uses a single fiber bundle for the probe fiber has been constructed. The sensor is based on absorption spectroscopy but has the significant advantage that the residual pump light works for the reference signal. The water depth can be evaluated from the minimum intensity ratio between the fluorescence signal and the reference signal when the probe is scanned in plane. The sensor can also estimate both the size and the position of a water droplet. A high degree of discrimination of a water droplet from other perturbations such as oil and surface irregularities has been demonstrated. An approximate calculation in a hemispherical model of a water droplet was carried out and is shown to be in good agreement with experimental results.

© 1998 Optical Society of America

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References

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    [CrossRef]
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    [CrossRef]
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1995 (2)

1994 (1)

S. Muto, H. Sato, T. Hosaka, “Optical humidity sensor using fluorescent plastic fiber and its application to breathing-condition monitor,” Jpn. J. Appl. Phys. 33, 6060–6064 (1994).
[CrossRef]

1993 (1)

1990 (1)

1989 (1)

J. B. Gruber, M. E. Hills, R. M. Macferlane, G. J. Quarles, G. J. Kintz, L. Esterowitz, “Spectra and energy levels of Tm3+:Y3Al5O12,” Phys. Rev. B 40, 9464–9478 (1989).
[CrossRef]

1988 (1)

Tso Yee Fan, G. Huber, R. L. Byer, P. Mitzscherlich, “Spectroscopy and diode laser-pumped operation of Tm, Ho:YAG,” IEEE J. Quantum Electron. 24, 924–933 (1988).
[CrossRef]

1951 (1)

Boer, J. H. W. G.

Byer, R. L.

Tso Yee Fan, G. Huber, R. L. Byer, P. Mitzscherlich, “Spectroscopy and diode laser-pumped operation of Tm, Ho:YAG,” IEEE J. Quantum Electron. 24, 924–933 (1988).
[CrossRef]

Curcio, J. A.

Esterowitz, L.

R. C. Stoneman, L. Esterowitz, “Efficient, broadly tunable, laser-pumped Tm:YAG and Tm:YSGG,” Opt. Lett. 15, 486–488 (1990).
[CrossRef] [PubMed]

J. B. Gruber, M. E. Hills, R. M. Macferlane, G. J. Quarles, G. J. Kintz, L. Esterowitz, “Spectra and energy levels of Tm3+:Y3Al5O12,” Phys. Rev. B 40, 9464–9478 (1989).
[CrossRef]

Fan, Tso Yee

Tso Yee Fan, G. Huber, R. L. Byer, P. Mitzscherlich, “Spectroscopy and diode laser-pumped operation of Tm, Ho:YAG,” IEEE J. Quantum Electron. 24, 924–933 (1988).
[CrossRef]

Gruber, J. B.

J. B. Gruber, M. E. Hills, R. M. Macferlane, G. J. Quarles, G. J. Kintz, L. Esterowitz, “Spectra and energy levels of Tm3+:Y3Al5O12,” Phys. Rev. B 40, 9464–9478 (1989).
[CrossRef]

Hemert, H. V.

Hills, M. E.

J. B. Gruber, M. E. Hills, R. M. Macferlane, G. J. Quarles, G. J. Kintz, L. Esterowitz, “Spectra and energy levels of Tm3+:Y3Al5O12,” Phys. Rev. B 40, 9464–9478 (1989).
[CrossRef]

Hoog, F. J.

Hop, E.

Hosaka, T.

S. Muto, H. Sato, T. Hosaka, “Optical humidity sensor using fluorescent plastic fiber and its application to breathing-condition monitor,” Jpn. J. Appl. Phys. 33, 6060–6064 (1994).
[CrossRef]

Huber, G.

Tso Yee Fan, G. Huber, R. L. Byer, P. Mitzscherlich, “Spectroscopy and diode laser-pumped operation of Tm, Ho:YAG,” IEEE J. Quantum Electron. 24, 924–933 (1988).
[CrossRef]

Kintz, G. J.

J. B. Gruber, M. E. Hills, R. M. Macferlane, G. J. Quarles, G. J. Kintz, L. Esterowitz, “Spectra and energy levels of Tm3+:Y3Al5O12,” Phys. Rev. B 40, 9464–9478 (1989).
[CrossRef]

Kroesen, G. M. W.

Luinge, H. J.

MacCraith, B. D.

F. J. McAleavey, B. D. MacCraith, “Diode-pumped thulium-doped zirconium fluoride fibre as a fluorescent source for water sensing,” Electron. Lett. 31, 1379–1380 (1995).
[CrossRef]

Macferlane, R. M.

J. B. Gruber, M. E. Hills, R. M. Macferlane, G. J. Quarles, G. J. Kintz, L. Esterowitz, “Spectra and energy levels of Tm3+:Y3Al5O12,” Phys. Rev. B 40, 9464–9478 (1989).
[CrossRef]

McAleavey, F. J.

F. J. McAleavey, B. D. MacCraith, “Diode-pumped thulium-doped zirconium fluoride fibre as a fluorescent source for water sensing,” Electron. Lett. 31, 1379–1380 (1995).
[CrossRef]

Mitzscherlich, P.

Tso Yee Fan, G. Huber, R. L. Byer, P. Mitzscherlich, “Spectroscopy and diode laser-pumped operation of Tm, Ho:YAG,” IEEE J. Quantum Electron. 24, 924–933 (1988).
[CrossRef]

Muto, S.

S. Muto, H. Sato, T. Hosaka, “Optical humidity sensor using fluorescent plastic fiber and its application to breathing-condition monitor,” Jpn. J. Appl. Phys. 33, 6060–6064 (1994).
[CrossRef]

Petty, C. C.

Quarles, G. J.

J. B. Gruber, M. E. Hills, R. M. Macferlane, G. J. Quarles, G. J. Kintz, L. Esterowitz, “Spectra and energy levels of Tm3+:Y3Al5O12,” Phys. Rev. B 40, 9464–9478 (1989).
[CrossRef]

Sato, H.

S. Muto, H. Sato, T. Hosaka, “Optical humidity sensor using fluorescent plastic fiber and its application to breathing-condition monitor,” Jpn. J. Appl. Phys. 33, 6060–6064 (1994).
[CrossRef]

Stoneman, R. C.

Appl. Opt. (1)

Appl. Spectrosc. (1)

Electron. Lett. (1)

F. J. McAleavey, B. D. MacCraith, “Diode-pumped thulium-doped zirconium fluoride fibre as a fluorescent source for water sensing,” Electron. Lett. 31, 1379–1380 (1995).
[CrossRef]

IEEE J. Quantum Electron. (1)

Tso Yee Fan, G. Huber, R. L. Byer, P. Mitzscherlich, “Spectroscopy and diode laser-pumped operation of Tm, Ho:YAG,” IEEE J. Quantum Electron. 24, 924–933 (1988).
[CrossRef]

J. Opt. Soc. Am. (1)

Jpn. J. Appl. Phys. (1)

S. Muto, H. Sato, T. Hosaka, “Optical humidity sensor using fluorescent plastic fiber and its application to breathing-condition monitor,” Jpn. J. Appl. Phys. 33, 6060–6064 (1994).
[CrossRef]

Opt. Lett. (1)

Phys. Rev. B (1)

J. B. Gruber, M. E. Hills, R. M. Macferlane, G. J. Quarles, G. J. Kintz, L. Esterowitz, “Spectra and energy levels of Tm3+:Y3Al5O12,” Phys. Rev. B 40, 9464–9478 (1989).
[CrossRef]

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Figures (12)

Fig. 1
Fig. 1

Fluorescence spectrum of Tm3+:YAG and absorption spectrum of liquid water.

Fig. 2
Fig. 2

Experimental setup for the optical fiber water-droplet sensor: LD, laser diode; TEC, thermoelectric cooler; BS, beam splitter; Si-PD, silicon photodiode; DVM’s, digital volt meters; PC’s, personal computers.

Fig. 3
Fig. 3

Dependence of (a) intensities of fluorescent light I F and reference laser diode light I L and (b) intensity ratio I F /I L on the relative probe position for two water droplets on a copper plate. Diameters and top heights of water droplets 1 and 2 are 5.5 and 1.6 mm, and 2.0 and 0.3 mm, respectively.

Fig. 4
Fig. 4

Dependence of (a) I F and I L and (b) I F /I L on the relative probe positions for a water droplet and a machine-oil drop on a copper plate. Diameters and top heights of the water droplet and the oil drop are 4.0 and 2.0 mm, and 5.0 and 0.3 mm, respectively.

Fig. 5
Fig. 5

Dependence of (a) I F and I L and (b) I F /I L on the relative probe position for surface irregularities on a copper plate. The concave irregularity is 2.0 mm in diameter and 0.4 mm in depth; the convex irregularity is 3.0 mm in diameter and 0.5 mm in top height.

Fig. 6
Fig. 6

Dependence of (a) I F and I L and (b) I F /I L on the relative probe position for a water droplet on a wood plate. The diameter and the top height of the droplet are 7.5 and 1.8 mm, respectively.

Fig. 7
Fig. 7

Two-dimensional mapping of contour curves of I F /I L for three water droplets (1, 2, and 3), whose diameters and top heights are 4.0 and 2.0 mm, 3.0 and 1.3 mm, and 2.0 and 0.3 mm, respectively.

Fig. 8
Fig. 8

Two-dimensional mapping of contour curves of I F /I L for three kinds of material on a copper plate. Diameters and top heights of water droplets 1 and 2 are 4.0 and 1.5 mm, and 3.0 and 1.0 mm, respectively. Diameters and top heights of cooking oils 1 and 2 are 5.0 and 0.5 mm, and 4.0 and 0.3 mm, respectively. Diameters and top heights of machine oils 1 and 2 are 4.0 and 0.4 mm, and 3.0 and 0.3 mm, respectively.

Fig. 9
Fig. 9

Model for theoretical calculation. (a) Geometry for scanning of the fiber probe above the water droplet along the diameter, (b) geometry of reflected lights 1–3.

Fig. 10
Fig. 10

Measured and calculated intensities of (a) I F and (b) I L and (c) I F /I L for a water droplet. The diameter and the top height of the measured water droplet are 4.2 and 2.0 mm, respectively.

Fig. 11
Fig. 11

Measured height dependence of minimum I F /I L in a water droplet for a copper plate and a wood plate.

Fig. 12
Fig. 12

Dependence of the measured width from an I F /I L curve on the width of a sample water droplet on a copper plate.

Equations (5)

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

I 1 x ,   y = R 1 x ,   y T C 1 x ,   y I 0 ,
I 2 x ,   y = T 1 x ,   y R 2 x ,   y T 3 x ,   y T C 2 x ,   y × exp - α eff L x ,   y I 0 ,
I 3 x ,   y = R 5 x ,   y T C 3 x ,   y I 0 ,
L x ,   y = R   cos   θ 1 + d x ,   y cos θ 1 - θ 2 .
I = x , y area   A   I 1 x ,   y + x , y area   A   I 2 x ,   y + x , y area   B   I 3 x ,   y .

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