Here - PMOD/WRC
Here - PMOD/WRC
Here - PMOD/WRC
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
spectrometer BOMEM DA3 is not necessarily optimal to<br />
the task of blackbody characterization. Nevertheless, we<br />
have been able to demonstrate the concept and obtain<br />
useful results . For data processing we have employed an<br />
algorithm 2 , which involves the spectral comparison of an<br />
unknown source with two known sources.<br />
Fourier<br />
Transform<br />
Spectrometer<br />
Figure 3.<br />
Schematic of the optical interface<br />
Experimental Results<br />
Measurements were performed according to the diagram<br />
shown in Fig. 4. In the first stage of the experiment, we<br />
performed spectral comparisons of heat pipe BBs with a<br />
Figure 4.<br />
Sequence of measurements<br />
number of fixed-point BBs. As an example we show the<br />
result of calibration of the Cs BB with the Al fixed-point<br />
BB (Fig. 5). For ease of data analysis we show the<br />
effective emissivity, which was always calculated using<br />
the radiance temperature at 1550 nm as the true (reference)<br />
temperature. The spectral radiance and the radiance<br />
temperature data are also generated during data processing.<br />
Figure 5.<br />
Elliptic<br />
Mirror<br />
90 degrees<br />
Port Lyot<br />
Stop<br />
b) 1.015<br />
Effective emissivity<br />
1.010<br />
1.005<br />
1.000<br />
0.995<br />
0.990<br />
0.985<br />
Folding<br />
Mirror<br />
Flat Pointing Mirror<br />
with Aperture Stop<br />
Rotation Stages<br />
Field<br />
Stop<br />
Blackbodies<br />
13.45 degrees<br />
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20<br />
Wavelength, μ m<br />
Effective emissivity of the Cs heat pipe BB<br />
Toroidal<br />
Mirror<br />
Alignment<br />
Camera<br />
After calibration of the Cs and Na heat pipe blackbodies,<br />
they were used to calibrate customer blackbodies at<br />
temperatures from 300 to 1000 C in 100 C steps. The<br />
emissivity of one of these had a distinctive pattern evident<br />
at all temperatures (600 C in Fig. 6)<br />
Effective emissivity<br />
1.005<br />
1.000<br />
0.995<br />
0.990<br />
0.985<br />
Figure 6. Customer BB calibration result with a distinctive<br />
spectral pattern<br />
Discussion<br />
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17<br />
Wavelength, μ m<br />
A systematic realization of an IR spectral radiance scale<br />
has been performed. In the spectral band of 8 to 14 m, the<br />
standard deviation of the mean for spectral radiance was<br />
typically at the level of 0.1%. In the spectral band from 3<br />
m to 5 m, scatter of the results for most temperatures is<br />
substantially larger, possibly relating to use of a wide band<br />
pyroelectric detector, and needs further attention. The<br />
results show no systematic spectral features for the transfer<br />
standard blackbodies but reveal some systematic features<br />
for one of the customer BBs. The results will be used to<br />
optimize the design of the dedicated facility for spectral<br />
characterization of IR sources under construction at NIST.<br />
References<br />
1. Walker J. H., Saunders R. D., and Hattenburg A. T., Spectral<br />
Radiance Calibrations, NBS Spec. Publ. 250-1, 1987.<br />
2. Reesink A. L., Rowell N. L., and Steele A. G., Using Fourier-<br />
Transform Blackbody Spectra to Determine Thermodynamic<br />
Temperature in the 600 C to 1000 C Range, in<br />
Temperature: Its Measurement and Control in Science and<br />
Industry, Volume 7, ed. D.C. Ripple, AIP, 19-24, 2003.<br />
3. Hanssen L.M., Mekhontsev S.N., Khromchenko V. B., Infrared<br />
spectral emissivity characterization facility at NIST, Proc.<br />
SPIE 5405, 1-12, 2004.<br />
4. Mekhontsev, S., Khromchenko, V., Prokhorov, A., Hanssen, L.,<br />
Emissivity evaluation of fixed-point blackbodies, Proc.<br />
TEMPMEKO 2004 (in print).<br />
5. Hanssen, L. M., Mekhontsev, S. N., Khromchenko, V. B.,<br />
Prokhorov, A. V. and Zeng, J., Study of infrared emissivity of<br />
a fixed-point blackbody cavity, Proc. NEWRAD 2005. <br />
6. Noorma M., Mekhontsev S. N, Khromchenko V. B., Gura A.<br />
V., Litorja M., Tsai B. K., Hanssen L. M., Transfer standard<br />
pyrometers for radiance temperature measurements below the<br />
freezing temperature of silver at NIST, NEWRAD 2005<br />
7. Mekhontsev S.N. and Hanssen L.M., Low scatter optical<br />
system for emittance and temperature measurements, in<br />
Temperature: Its Measurement and Control in Science and<br />
Industry, Volume 7, ed. D.C. Ripple, AIP, 693-698, 2003.<br />
8. Revercomb, H. E., Buijs, H., Howell, H. B., LaPorte, D. D.,<br />
Smith, W. L., and Sromovsky, L. A., Radiometric calibration<br />
of IR Fourier transform spectrometers: Solution to a problem<br />
with the High-Resolution Interferometer Sounder. Applied<br />
Optics 27 (15), 3210-3218, 1988.<br />
316