A task group of CCT-WG5 (radiation thermometry) was established in May 2008 to write text for the mise-en-pratique for the definition of the kelvin (MeP-K) for high temperatures. This task group reviewed and gave summaries for the existing techniques for filter radiometry as a means of determining the absolute radiance, and hence the thermodynamic temperature of a blackbody source. Three approaches were described-the radiance method, which calibrates the radiation thermometer for radiance responsivity, the irradiance method, which calibrates a filter radiometer for irradiance responsivity and then measures the source through two apertures, and the hybrid method that introduces a lens to the irradiance method. In the "hybrid method" the radiation thermometer consists of a filter radiometer, a double aperture system, and a lens. The lens allows the instrument to view a small area blackbody source. The system is calibrated "in parts"-i.e., the filter radiometer is calibrated for irradiance responsivity, and the transmittance of the lens and the geometric factor are determined separately. The main drawbacks of this single lens instrument are its high size-of-source effect (∼0.2 %), and that this effect has to be determined in an "absolute" sense-relative to a theoretical infinite source. However, although the correction is large, with careful evaluation, the associated uncertainty can be made sufficiently small to measure the temperature of fixed-point cell transitions with low uncertainties. This article reviews the hybrid method and gives a comprehensive discussion of the associated uncertainty components.
The solar ultraviolet spectrum captured by commercially available diode-array spectroradiometers is dominated by stray light from longer wavelengths with higher intensity. The implementation of a digital micromirror device in an array spectroradiometer has the potential to enable the precise selection of desired wavelengths as well as the ability to reduce spectral intensity of some wavelengths via selective mirror modulation, both reducing long wavelength stray light. A prototype consisting of off-the-shelf components has been assembled to verify the validity of the base concept, and initial measurements have been performed to confirm the throughput and image qualities such as spectral resolution and astigmatism.
Abstract. For spectroradiometers, the characterisation of their
wavelength scale and spectral bandwidth underpins the quality
of measured data substantially. This characterisation can be performed using
metrology-grade tuneable monochromatic sources, which are currently
available only in a few laboratories worldwide. Yet in numerous
applications, only the in-field calibration is a feasible solution. We have
designed and developed a tuneable and portable radiation source (TuPS) in
the wavelength range from 300 to 350 nm for the in-field characterisation
of Dobson spectrometers' wavelength scale and slit function, with standard
uncertainties better than 0.02 nm in wavelength and with the bandwidth of
emitted radiation smaller than 0.13 nm full width at half maximum (FWHM). The TuPS is designed such that only minor modifications of its optical system extend/shift its spectral range towards visible and near-infrared spectral regions and thus expand its
application for characterisation of any spectroradiometers in the relevant
spectral region of interest.
For spectrometers the characterisation of their wavelength scale and spectral bandwidth underpins the quality of their measured data. This characterisation can be performed using metrology-grade tuneable monochromatic sources, which are currently available only in a few laboratories world-wide. Yet in numerous applications only the in-field calibration is a feasible solution. We have designed and developed a Tuneable and Portable radiation Source (TuPS) in the wavelength range from 300 nm to 350 nm for the in-field characterization of Dobson and Brewer spectrometers wavelength scale and slit-function with uncertainties better than 0.02 nm in wavelength with emitted radiation bandwidth smaller than 0,1 nm. The TuPS is designed such that only minor modification of its optical system extends/shifts its spectral range towards visible and near-infrared spectral regions and thus expand its application for spectral characterisation of any spectrometers in the relevant spectral region of interest.
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