Abstract

We have developed a low-temperature optical-fiber-based two-color infrared thermometer. A single 700-μm-bore hollow glass optical fiber collects and transmits radiation that is then modulated and split into two paths by a reflective optical chopper. Two different thermoelectrically cooled mid-infrared HgCdZnTe photoconductors monitor the chopped signals that are recovered with lock-in amplification. With the two previously obtained blackbody calibration equations, a computer algorithm calculates the true temperature and emissivity of a target in real time, taking into account reflection of the ambient radiation field from the target surface. The small numerical aperture of the hollow glass fiber and the fast response of the detectors, together with the two-color principle, permit high spatial and temporal resolution while allowing the user to dynamically alter the fiber-to-target distance.

© 1998 Optical Society of America

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References

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  1. X. Maldague, M. Dufour, “Dual imager and its applications to active vision robot welding, surface inspection, and two-color pyrometry,” Opt. Eng. 28(8), 872–880 (1989).
  2. K. Crane, P. J. Beckwith, “I.R. radiation pyrometer,” U.S. patent4,470,710 (11September1984).
  3. O. Eyal, A. Katzir, “Temperature measurements utilizing two-bandpass fiber optic radiometry,” Opt. Eng. 34(2), 470–473 (1995).
    [CrossRef]
  4. A. S. Tenney, “Radiation ratio thermometry,” in Theory and Practice of Radiation Thermometry, D. P. Dewitt, G. D. Nutter, eds. (Wiley, New York, 1988), pp. 459–494.
    [CrossRef]
  5. J. Brownson, K. Gronokowski, E. Meade, “Two-color imaging radiometry for pyrotechnic diagnostics,” in Selected Papers on Temperature Sensing: Optical Methods, R. D. Lucier, ed., Vol. MS116 of SPIE Milestone Series (SPIE, Bellingham, Wash., 1987), pp. 525–532.
  6. M. Alaluf, J. Dror, A. Katzir, N. Croitoru, “Infrared radiometry measurements using plastic hollow waveguides,” J. Phys. D: Appl. Phys. 26(7), 1036–1040 (1993).
  7. S. J. Saggese, J. A. Harrington, G. H. Sigel, “Hollow sapphire waveguides for remote radiometric temperature measurements,” Electron. Lett. 27(9), 707–709 (1991).
    [CrossRef]
  8. O. Eyal, A. Zur, O. Shenfeld, M. Gilo, A. Katzir, “Infrared radiometry using silver halide fibers and a cooled photonic detector,” Opt. Eng. 33(2), 502–509 (1994).
    [CrossRef]
  9. T. Abel, J. Hirsch, J. A. Harrington, “Hollow glass waveguides for broadband infrared transmission,” in Biomedical Fiber Optic Instrumentation, J. A. Harrington, D. M. Harris, A. Katzir, F. P. Milanovich, eds., Proc. SPIE2131, 11–17 (1994).
    [CrossRef]
  10. T. Abel, J. Hirsch, J. A. Harrington, “Hollow glass waveguides for broadband infrared transmission,” Opt. Lett. 19, 1034–1036 (1994).
    [CrossRef] [PubMed]

1995 (1)

O. Eyal, A. Katzir, “Temperature measurements utilizing two-bandpass fiber optic radiometry,” Opt. Eng. 34(2), 470–473 (1995).
[CrossRef]

1994 (2)

O. Eyal, A. Zur, O. Shenfeld, M. Gilo, A. Katzir, “Infrared radiometry using silver halide fibers and a cooled photonic detector,” Opt. Eng. 33(2), 502–509 (1994).
[CrossRef]

T. Abel, J. Hirsch, J. A. Harrington, “Hollow glass waveguides for broadband infrared transmission,” Opt. Lett. 19, 1034–1036 (1994).
[CrossRef] [PubMed]

1993 (1)

M. Alaluf, J. Dror, A. Katzir, N. Croitoru, “Infrared radiometry measurements using plastic hollow waveguides,” J. Phys. D: Appl. Phys. 26(7), 1036–1040 (1993).

1991 (1)

S. J. Saggese, J. A. Harrington, G. H. Sigel, “Hollow sapphire waveguides for remote radiometric temperature measurements,” Electron. Lett. 27(9), 707–709 (1991).
[CrossRef]

1989 (1)

X. Maldague, M. Dufour, “Dual imager and its applications to active vision robot welding, surface inspection, and two-color pyrometry,” Opt. Eng. 28(8), 872–880 (1989).

Abel, T.

T. Abel, J. Hirsch, J. A. Harrington, “Hollow glass waveguides for broadband infrared transmission,” Opt. Lett. 19, 1034–1036 (1994).
[CrossRef] [PubMed]

T. Abel, J. Hirsch, J. A. Harrington, “Hollow glass waveguides for broadband infrared transmission,” in Biomedical Fiber Optic Instrumentation, J. A. Harrington, D. M. Harris, A. Katzir, F. P. Milanovich, eds., Proc. SPIE2131, 11–17 (1994).
[CrossRef]

Alaluf, M.

M. Alaluf, J. Dror, A. Katzir, N. Croitoru, “Infrared radiometry measurements using plastic hollow waveguides,” J. Phys. D: Appl. Phys. 26(7), 1036–1040 (1993).

Beckwith, P. J.

K. Crane, P. J. Beckwith, “I.R. radiation pyrometer,” U.S. patent4,470,710 (11September1984).

Brownson, J.

J. Brownson, K. Gronokowski, E. Meade, “Two-color imaging radiometry for pyrotechnic diagnostics,” in Selected Papers on Temperature Sensing: Optical Methods, R. D. Lucier, ed., Vol. MS116 of SPIE Milestone Series (SPIE, Bellingham, Wash., 1987), pp. 525–532.

Crane, K.

K. Crane, P. J. Beckwith, “I.R. radiation pyrometer,” U.S. patent4,470,710 (11September1984).

Croitoru, N.

M. Alaluf, J. Dror, A. Katzir, N. Croitoru, “Infrared radiometry measurements using plastic hollow waveguides,” J. Phys. D: Appl. Phys. 26(7), 1036–1040 (1993).

Dror, J.

M. Alaluf, J. Dror, A. Katzir, N. Croitoru, “Infrared radiometry measurements using plastic hollow waveguides,” J. Phys. D: Appl. Phys. 26(7), 1036–1040 (1993).

Dufour, M.

X. Maldague, M. Dufour, “Dual imager and its applications to active vision robot welding, surface inspection, and two-color pyrometry,” Opt. Eng. 28(8), 872–880 (1989).

Eyal, O.

O. Eyal, A. Katzir, “Temperature measurements utilizing two-bandpass fiber optic radiometry,” Opt. Eng. 34(2), 470–473 (1995).
[CrossRef]

O. Eyal, A. Zur, O. Shenfeld, M. Gilo, A. Katzir, “Infrared radiometry using silver halide fibers and a cooled photonic detector,” Opt. Eng. 33(2), 502–509 (1994).
[CrossRef]

Gilo, M.

O. Eyal, A. Zur, O. Shenfeld, M. Gilo, A. Katzir, “Infrared radiometry using silver halide fibers and a cooled photonic detector,” Opt. Eng. 33(2), 502–509 (1994).
[CrossRef]

Gronokowski, K.

J. Brownson, K. Gronokowski, E. Meade, “Two-color imaging radiometry for pyrotechnic diagnostics,” in Selected Papers on Temperature Sensing: Optical Methods, R. D. Lucier, ed., Vol. MS116 of SPIE Milestone Series (SPIE, Bellingham, Wash., 1987), pp. 525–532.

Harrington, J. A.

T. Abel, J. Hirsch, J. A. Harrington, “Hollow glass waveguides for broadband infrared transmission,” Opt. Lett. 19, 1034–1036 (1994).
[CrossRef] [PubMed]

S. J. Saggese, J. A. Harrington, G. H. Sigel, “Hollow sapphire waveguides for remote radiometric temperature measurements,” Electron. Lett. 27(9), 707–709 (1991).
[CrossRef]

T. Abel, J. Hirsch, J. A. Harrington, “Hollow glass waveguides for broadband infrared transmission,” in Biomedical Fiber Optic Instrumentation, J. A. Harrington, D. M. Harris, A. Katzir, F. P. Milanovich, eds., Proc. SPIE2131, 11–17 (1994).
[CrossRef]

Hirsch, J.

T. Abel, J. Hirsch, J. A. Harrington, “Hollow glass waveguides for broadband infrared transmission,” Opt. Lett. 19, 1034–1036 (1994).
[CrossRef] [PubMed]

T. Abel, J. Hirsch, J. A. Harrington, “Hollow glass waveguides for broadband infrared transmission,” in Biomedical Fiber Optic Instrumentation, J. A. Harrington, D. M. Harris, A. Katzir, F. P. Milanovich, eds., Proc. SPIE2131, 11–17 (1994).
[CrossRef]

Katzir, A.

O. Eyal, A. Katzir, “Temperature measurements utilizing two-bandpass fiber optic radiometry,” Opt. Eng. 34(2), 470–473 (1995).
[CrossRef]

O. Eyal, A. Zur, O. Shenfeld, M. Gilo, A. Katzir, “Infrared radiometry using silver halide fibers and a cooled photonic detector,” Opt. Eng. 33(2), 502–509 (1994).
[CrossRef]

M. Alaluf, J. Dror, A. Katzir, N. Croitoru, “Infrared radiometry measurements using plastic hollow waveguides,” J. Phys. D: Appl. Phys. 26(7), 1036–1040 (1993).

Maldague, X.

X. Maldague, M. Dufour, “Dual imager and its applications to active vision robot welding, surface inspection, and two-color pyrometry,” Opt. Eng. 28(8), 872–880 (1989).

Meade, E.

J. Brownson, K. Gronokowski, E. Meade, “Two-color imaging radiometry for pyrotechnic diagnostics,” in Selected Papers on Temperature Sensing: Optical Methods, R. D. Lucier, ed., Vol. MS116 of SPIE Milestone Series (SPIE, Bellingham, Wash., 1987), pp. 525–532.

Saggese, S. J.

S. J. Saggese, J. A. Harrington, G. H. Sigel, “Hollow sapphire waveguides for remote radiometric temperature measurements,” Electron. Lett. 27(9), 707–709 (1991).
[CrossRef]

Shenfeld, O.

O. Eyal, A. Zur, O. Shenfeld, M. Gilo, A. Katzir, “Infrared radiometry using silver halide fibers and a cooled photonic detector,” Opt. Eng. 33(2), 502–509 (1994).
[CrossRef]

Sigel, G. H.

S. J. Saggese, J. A. Harrington, G. H. Sigel, “Hollow sapphire waveguides for remote radiometric temperature measurements,” Electron. Lett. 27(9), 707–709 (1991).
[CrossRef]

Tenney, A. S.

A. S. Tenney, “Radiation ratio thermometry,” in Theory and Practice of Radiation Thermometry, D. P. Dewitt, G. D. Nutter, eds. (Wiley, New York, 1988), pp. 459–494.
[CrossRef]

Zur, A.

O. Eyal, A. Zur, O. Shenfeld, M. Gilo, A. Katzir, “Infrared radiometry using silver halide fibers and a cooled photonic detector,” Opt. Eng. 33(2), 502–509 (1994).
[CrossRef]

Electron. Lett. (1)

S. J. Saggese, J. A. Harrington, G. H. Sigel, “Hollow sapphire waveguides for remote radiometric temperature measurements,” Electron. Lett. 27(9), 707–709 (1991).
[CrossRef]

J. Phys. D: Appl. Phys. (1)

M. Alaluf, J. Dror, A. Katzir, N. Croitoru, “Infrared radiometry measurements using plastic hollow waveguides,” J. Phys. D: Appl. Phys. 26(7), 1036–1040 (1993).

Opt. Eng. (3)

O. Eyal, A. Zur, O. Shenfeld, M. Gilo, A. Katzir, “Infrared radiometry using silver halide fibers and a cooled photonic detector,” Opt. Eng. 33(2), 502–509 (1994).
[CrossRef]

X. Maldague, M. Dufour, “Dual imager and its applications to active vision robot welding, surface inspection, and two-color pyrometry,” Opt. Eng. 28(8), 872–880 (1989).

O. Eyal, A. Katzir, “Temperature measurements utilizing two-bandpass fiber optic radiometry,” Opt. Eng. 34(2), 470–473 (1995).
[CrossRef]

Opt. Lett. (1)

Other (4)

T. Abel, J. Hirsch, J. A. Harrington, “Hollow glass waveguides for broadband infrared transmission,” in Biomedical Fiber Optic Instrumentation, J. A. Harrington, D. M. Harris, A. Katzir, F. P. Milanovich, eds., Proc. SPIE2131, 11–17 (1994).
[CrossRef]

A. S. Tenney, “Radiation ratio thermometry,” in Theory and Practice of Radiation Thermometry, D. P. Dewitt, G. D. Nutter, eds. (Wiley, New York, 1988), pp. 459–494.
[CrossRef]

J. Brownson, K. Gronokowski, E. Meade, “Two-color imaging radiometry for pyrotechnic diagnostics,” in Selected Papers on Temperature Sensing: Optical Methods, R. D. Lucier, ed., Vol. MS116 of SPIE Milestone Series (SPIE, Bellingham, Wash., 1987), pp. 525–532.

K. Crane, P. J. Beckwith, “I.R. radiation pyrometer,” U.S. patent4,470,710 (11September1984).

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Figures (8)

Fig. 1
Fig. 1

Configuration of the two-color infrared thermometer. The radiation transmitted by the fiber is either passed or reflected by the chopper, simultaneously modulating the radiation for lock-in amplification and splitting the radiation into two detection paths.

Fig. 2
Fig. 2

Detector calibration curves. The lock-in signals from the two detectors were measured as a function of the temperature of a blackbody and were fit with the exponential function (solid curve) in Eq. (7).

Fig. 3
Fig. 3

Theoretical and experimental temperature response of the detectors. The offset is subtracted from the experimental curves. Division of each experimental curve by a constant representing system losses shows that the experimentally determined calibration equations agree with those derived theoretically.

Fig. 4
Fig. 4

Normalized detector voltages as a function of scan distance across an interface between black anodized and white spray-painted aluminum for various fiber heights. The interface is located at x = 0, with the black surface on the left and the white surface on the right.

Fig. 5
Fig. 5

Gaussian 1/e half-width fit parameter as a function of fiber height above the target surface. As D approaches zero, w approaches approximately the bore radius, and the linear fit is no longer valid. The multimode broadband propagation in the hollow fiber results in a 1/e half-width that is only slightly smaller than the 350-μm-bore radius at D = 0. (In the case of single-mode propagation, the 1/e half-width would be much smaller than the bore radius.) The error bars represent the upper and lower bounds on the values for w that could fit the scans in Fig. 4.

Fig. 6
Fig. 6

Difference between the two-color temperature and the actual (silicon sensor) temperature versus the actual temperature for a blackbody target. The two temperatures agree to within the accuracy of the silicon sensor at all temperatures between the cool and warm blackbody calibration points. A systematic bias of +1 °C is apparent. The noise at lower temperatures is a result of the lower SNR in the detectors and the singularity when T targ = T bg.

Fig. 7
Fig. 7

Two-color temperature and emissivity versus fiber-to-target distance for a uniformly heated target. The data points represent average values and the error bars represent minimum and maximum values over the 10-s measurement interval.

Fig. 8
Fig. 8

Comparison of two-color and brightness (single detector, 2–6 μm) calculated temperatures for two materials of different emissivity at the same temperature. Measurements were acquired for 1 min for each material. Unlike the two-color temperature, the brightness temperature obtained from the 2–6-μm photoconductor is inaccurate for the low-emissivity target.

Equations (13)

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W b λ ,   T = 2 π hc 2 λ 5 1 exp hc / λ kT - 1 ,
V b T =   d A f d A t cos 2   θ R 2 λ min λ max d λ   W b λ ,   T π   F λ S λ ,
V b T = D 2 π 0 a t d R t 0 a f d R f 0 2 π d ϕ f 0 2 π d ϕ t × R f R t R f 2 + R t 2 - 2 R f R t   cos   ϕ f + D 2 2 × λ min λ max d λ W b λ ,   T F λ S λ ,
V b T = π a f 2 NA 2 λ min λ max d λ W b λ ,   T F λ S λ ,
W λ ,   ε ,   T = ε W b λ ,   T ,
V ε ,   T targ = ε V b T targ + 1 - ε V b T bg ,
V lock - in T b ,   T h = V o T h + exp a + b T b + cT b ,
V b T b = V lock - in T b ,   T h - V o T h = exp a + b T b + cT b .
V lock - in ε ,   T targ - V o = ε   exp a + b T targ + cT targ + 1 - ε exp a + b T bg + cT bg .
erf x w = 2 π 0 x / w exp - t 2 d t ,
V x = V white white   H R t d A + V black black   H R t d A ,
H R t = exp - R t w 2 ,
H R t = exp - R t 0.0375 D 2 ,

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