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UV-Vis-NIR SIRCUS
The basic SIRCUS calibration setup is shown in figure 1 below. The output from a tunable laser is sent through an intensity stabilizer, then through a ‘speckle removal system’ (typically an ultrasonic bath for fiber-coupled systems like in the UV-Vis-NIR SIRCUS) and into the integrating sphere. Beamsplitters send some of the laser radiation into a spectrum analyzer and a wavemeter to monitor the spectral properties and the wavelength of the light. The irradiance is measured first by the reference instrument and the radiometric quantity is measured by the Radiometer Under Test. A monitor detector on the wall of the integrating sphere accounts for any laser intensity changes between the two measurements. A linear encoder records the position of the radiometer stage and is used to radiometrically determine the distance between the sphere and the irradiance detector reference plane (using the inverse square law). A computer controls the measurement sequence and records the data.

Schematic diagram of the SIRCUS calibration facility

Figure 1. Schematic diagram of the SIRCUS calibration facility.

In figure 2, the lasers and output powers used in the UV-Vis-NIR SIRCUS are given. Several different tunable lasers are used, as shown below. The UV region (200 nm to 400 nm) is covered by a frequency-multiplied Ti-Sapphire laser, which operates in quasi-cw mode (76 MHz repetition rate), with user-selectable pulse widths of 10 psec, 2 psec, or 200 fsec. The pulsed lasers been verified as equivalent to continuous-wave (cw) lasers for standard detector calibrations.

Image showing lasers and powers available on UV-Vis-NIR SIRCUS

Figure 2. Lasers and powers available on UV-Vis-NIR SIRCUS.

The SIRCUS facility provides the state-of-the-art low uncertainty calibration for various optical radiometers and instruments used in many applications. Currently an expanded uncertainty of 0.08 % (k=2) is achievable for an irradiance responsivity calibration in the visible and near IR region for high-quality instruments. The primary uncertainty components and their estimated magnitude are listed below.
Schematic for a SIRCUS calibration with primary uncertainty components highlighted

Figure 3. Experimental setup for a SIRCUS calibration with primary uncertainty components highlighted. 		   Nominal uncertainty budget for an irradiance meter in the visible or near IR spectral region

Figure 4. Nominal uncertainty budget for an irradiance meter in the visible or near IR spectral region.


The facility also has advantages of negligible bandwidth and large dynamic range compared with the SCF. These characteristics enable filter radiometers to be calibrated with highest possible accuracy. Figure 5 compares the spectral responsivity of a narrow band filter radiometer measured on SIRCUS and the SCF. The left hand figure shows the comparison results on a linear scale, the right hand figure on a log scale. Note that there are several overlying SIRCUS measurements on the rising and falling edges of the response.
Relative spectral responsivity of the PEP filter radiometer measured on SIRCUS and the SCF.

Figure 5. Relative spectral responsivity of the PEP filter radiometer measured on SIRCUS and the SCF.

Example Applications:

References:

  1. Facility for spectral iradiance responsivity calibrations using uniform sources, (843 kB PDF)
    S.W. Brown, G.P. Eppeldauer, and K.R. Lykke,
    Appl. Opt. 45(32), 8218-8237 (2006).

  2. Simple Spectral Stray Light Correction Method for Array Spectroradiometers, (843 kB PDF)
    Y. Zong, S.W. Brown, B.C Johnson, K.R. Lykke, and Y. Ohno,
    Appl. Opt. 45(6), 1111-1119 (2006).

  3. Realization and application of a detector-based tristimulus color scale at the National Institute of Standards and Technology, USA.
    G.P. Eppeldauer, S.W. Brown, K.R. Lykke, and Y. Ohno,
    AIC Colour 05 – 10th Congress of the International Colour Association, Proc. Part I (ed. by J.L. Nieves and J. H-Andres), pp. 693-696 (2005).

  4. Spectral irradiance and radiance responsivity calibrations using uniform sources (SIRCUS) facility at NIST,
    S.W. Brown, G.P. Eppeldauer, J.P. Rice, J. Zhang, and K.R. Lykke,
    Proc. SPIE 5542, 363-374 (2004).

  5. Stray light correction of the Marine Optical Optical Buoy.
    S.W. Brown, B.C. Johnson, S.J. Flora, M.E. Feinholz, M.A. Yarbrough, R.A. Barnes, Y.S. Kim, K.R. Lykke and D.K. Clark,
    Chapter 2-6 in NASA Technical Memorandum Ocean Optics Protocols for Satellite Ocean Color Sensor Validation, Rev. 4, (NASA’s Goddard Space Flight Center, Greenbelt, MD 20771), ed. by J. Mueller and G. Fargion (2004).

  6. The realization and the dissemination of the detector-based kelvin.
    H.W. Yoon, et al.
    in Proc. Tempmeko 04 (Dubrovnik, Croatia), 2004.

  7. Advances in Radiometry for Ocean Color.
    S.W. Brown, et al.,
    in NASA Technical Memorandum Volume VI Rev. 4: Special Topics in Ocean Optics Protocols and Appendices. (NASA’s Goddard Space Flight Center, Greenbelt, MD 20771), ed. by J.L. Mueller and G.S. Fargion (2004), pp. 8-35.

  8. Temperature scales using radiation thermometers calibrated from absolute irradiance and radiance responsivity.
    Yoon, H.W., et al.
    in NCSL International Workshop and Symposium (Orlando, FL), 2003.

  9. Stray light correction algorithm for spectrographs. ( 130kB PDF)
    S.W. Brown, B.C. Johnson, M.E. Feinholz, M.A. Yarbrough, S.J. Flora, K.R. Lykke, and D.K. Clark.
    Metrologia 40, S81-S84 (2003).

  10. Geometric area measurements of circular apertures for radiometry at NIST.
    J. Fowler and M. Litorja,
    Metrologia 40, S9-S12 (2003).

  11. Comparison of laser-based and conventional calibrations of sun photometers.
    N. Souaidia, et al.,
    Proc. SPIE 4481, 61-72 (2003).

  12. Comparison of cryogenic radiometry and thermal radiometry calibrations at NIST using multichannel filter radiometers. (57 kB PDF)
    B.C. Johnson, S.W. Brown, K.R. Lykke, C.E. Gibson, G. Fargion, G. Meister, S.B. Hooker, B. Markham, and J.J. Butler,
    Metrologia 40, S216-S218 (2003).

  13. Improved Accuracy Photometric and Tristimulus-Color Scales Based On Spectral Irradiance Responsivity.
    G. Eppeldauer, S.W. Brown, C.C. Miller, and K.R. Lykke,
    Proc. 25th Session of the CIE (San Diego, CA), pp. 30-33 (2003).

  14. A comparison of laser-based and conventional calibrations of sun photometers.
    N. Souaidia, C. Pietras, S. Brown, B.C. Johnson, and G. Fargion,
    in SIMBIOS Project 2002 Annual Report, NASA Technical Memorandum TM-2003-21622, (NASA’s Goddard Space Flight Center, Greenbelt, MD 20771), ed. by G.S. Fargion and C.R. McClain (2002).

  15. NIST facility for Spectral Irradiance and Radiance Responsivity Calibrations with Uniform Sources (210 kB).
    S.W. Brown, G.P. Eppeldauer, and K.R. Lykke,
    Metrologia 37, 579-582 (2000).

  16. Realization of a spectral radiance responsivity scale with a laser-based source and Si radiance meters (158 kB).
    G.P. Eppeldauer, S.W. Brown, T.C. Larason, M. Racz, and K.R. Lykke,
    Metrologia 37, 531-534 (2000).

  17. Spectral response based calibration method of tristimulus colorimeters.
    G.P. Eppeldauer,
    J. Res. Natl. Inst. Stands. Technol. 103, 615-619 (1998).

  18. Highly stable, monochromatic and tunable optical radiation source and its application to high accuracy spectrophotometry.
    V.E. Anderson, N.P. Fox, and D.H. Nettleton,
    Appl. Opt. 31, 536-545 (1992).

  19. Absolute spectral radiometric determination of the thermodynamic temperatures of the melting/freezing points of gold, silver, and aluminium.
    N.P. Fox, J.E. Martin, and D.H. Nettleton,
    Metrologia 28, 357-374 (1991).

  20. Spectroradiometric determination of the freezing temperature of gold.
    K.D. Mielenz, R.D. Saunders, and J.B. Shumaker,
    J. Res. Natl. Inst. Stands. Technol. 95, 49-67 (1990).

  21. Intercomparison between independent irradiance scales based on silicon photodiodes physics, gold-point blackbody radiation, and synchrotron radiation.
    A.R. Schaefer, R.D. Saunders, and L.R. Hughey,
    Opt. Eng. 25, 892-896 (1986).

  22. Spectrophotometric tests using a dye-laser-based radiometric characterization facility.
    A.R. Schaefer and K.L. Eckerle,
    Appl. Opt. 23, 250-256 (1984).
Return to SIRCUS

For technical information or questions, contact:
Steve Brown
Phone: 301-975-5167
Fax: 301-840-8551
Email: steven.brown@nist.gov

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Online: March 2007   -   Last updated: February 2008