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Improved detector technology in the past two decades has opened a new era in detector metrology of optical radiation measurements. Lower calibration and measurement uncertainties can be achieved with modern detector/radiometer standards than traditionally used source standards (blackbodies and lamps). The achievable lower uncertainties provided the motivation to decrease the gap between the 0.02% (k=2) relative expanded uncertainty of cryogenic radiometer measurements and the two to three orders of magnitude higher uncertainties of field-level optical radiation measurements. Thus, the role of modern detector/radiometer standards is increasing to lower calibration and measurement uncertainties compared to traditionally used source standards.
Standard detector/radiometer developments from the ultraviolet to the infrared
To decrease the large measurement-uncertainty gap between cryogenic radiometer measurements (such as those made by the NIST Primary Optical Watt Radiometer) and field measurements, a large variety of transfer and working standard radiometers are being developed. These radiometers are designed to work in different radiometric and photometric measurement modes and satisfy diverse requirements in different scale realizations, scale propagations, and field applications. The radiometers are optically and electronically characterized and verified so that the scale uncertainty is dominated by the scale realization procedure and not by the performance of the radiometers.
For examples, see Transfer and working standard radiometers and photometers and NIST Technical Note 1438: Optical radiation measurement with selected detectors and matched electronic circuits between 200 nm and 20 μm (14 MB pdf).
Detector-based scales
New radiometric, radiance temperature, photometric, and color scales have been realized based on the spectral responsivity of standard detectors and radiometers. These reference responsivity scales have been transferred to other NIST calibration facilities to realize and maintain more fundamental detector-based scales and decrease calibration and measurement uncertainties.
Representative papers, published by the Optical Technology Division from 1996 to present, have been collected in the NIST Technical Note 1621. These papers describe the conversion of the high-performance optical radiometers into standards and the realization the new improved spectral-responsivity based scales. For more details, see NIST Technical Note 1621: Optical radiation measurements based on detector standards.