Here - PMOD/WRC

spectrometer BOMEM DA3 is not necessarily optimal to
the task of blackbody characterization. Nevertheless, we
have been able to demonstrate the concept and obtain
useful results . For data processing we have employed an
algorithm 2 , which involves the spectral comparison of an
unknown source with two known sources.
Fourier
Transform
Spectrometer
Figure 3.
Schematic of the optical interface
Experimental Results
Measurements were performed according to the diagram
shown in Fig. 4. In the first stage of the experiment, we
performed spectral comparisons of heat pipe BBs with a
Figure 4.
Sequence of measurements
number of fixed-point BBs. As an example we show the
result of calibration of the Cs BB with the Al fixed-point
BB (Fig. 5). For ease of data analysis we show the
effective emissivity, which was always calculated using
the radiance temperature at 1550 nm as the true (reference)
temperature. The spectral radiance and the radiance
temperature data are also generated during data processing.
Figure 5.
Elliptic
Mirror
90 degrees
Port Lyot
Stop
b) 1.015
Effective emissivity
1.010
1.005
1.000
0.995
0.990
0.985
Folding
Mirror
Flat Pointing Mirror
with Aperture Stop
Rotation Stages
Field
Stop
Blackbodies
13.45 degrees
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Wavelength, μ m
Effective emissivity of the Cs heat pipe BB
Toroidal
Mirror
Alignment
Camera
After calibration of the Cs and Na heat pipe blackbodies,
they were used to calibrate customer blackbodies at
temperatures from 300 to 1000 C in 100 C steps. The
emissivity of one of these had a distinctive pattern evident
at all temperatures (600 C in Fig. 6)
Effective emissivity
1.005
1.000
0.995
0.990
0.985
Figure 6. Customer BB calibration result with a distinctive
spectral pattern
Discussion
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Wavelength, μ m
A systematic realization of an IR spectral radiance scale
has been performed. In the spectral band of 8 to 14 m, the
standard deviation of the mean for spectral radiance was
typically at the level of 0.1%. In the spectral band from 3
m to 5 m, scatter of the results for most temperatures is
substantially larger, possibly relating to use of a wide band
pyroelectric detector, and needs further attention. The
results show no systematic spectral features for the transfer
standard blackbodies but reveal some systematic features
for one of the customer BBs. The results will be used to
optimize the design of the dedicated facility for spectral
characterization of IR sources under construction at NIST.
References
1. Walker J. H., Saunders R. D., and Hattenburg A. T., Spectral
Radiance Calibrations, NBS Spec. Publ. 250-1, 1987.
2. Reesink A. L., Rowell N. L., and Steele A. G., Using Fourier-
Transform Blackbody Spectra to Determine Thermodynamic
Temperature in the 600 C to 1000 C Range, in
Temperature: Its Measurement and Control in Science and
Industry, Volume 7, ed. D.C. Ripple, AIP, 19-24, 2003.
3. Hanssen L.M., Mekhontsev S.N., Khromchenko V. B., Infrared
spectral emissivity characterization facility at NIST, Proc.
SPIE 5405, 1-12, 2004.
4. Mekhontsev, S., Khromchenko, V., Prokhorov, A., Hanssen, L.,
Emissivity evaluation of fixed-point blackbodies, Proc.
TEMPMEKO 2004 (in print).
5. Hanssen, L. M., Mekhontsev, S. N., Khromchenko, V. B.,
Prokhorov, A. V. and Zeng, J., Study of infrared emissivity of
a fixed-point blackbody cavity, Proc. NEWRAD 2005.
6. Noorma M., Mekhontsev S. N, Khromchenko V. B., Gura A.
V., Litorja M., Tsai B. K., Hanssen L. M., Transfer standard
pyrometers for radiance temperature measurements below the
freezing temperature of silver at NIST, NEWRAD 2005
7. Mekhontsev S.N. and Hanssen L.M., Low scatter optical
system for emittance and temperature measurements, in
Temperature: Its Measurement and Control in Science and
Industry, Volume 7, ed. D.C. Ripple, AIP, 693-698, 2003.
8. Revercomb, H. E., Buijs, H., Howell, H. B., LaPorte, D. D.,
Smith, W. L., and Sromovsky, L. A., Radiometric calibration
of IR Fourier transform spectrometers: Solution to a problem
with the High-Resolution Interferometer Sounder. Applied
Optics 27 (15), 3210-3218, 1988.
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