Integrating sphere reflectometry

Another approach was chosen at INRiM, using an integrating sphere reflectometry technique in which the sample reflectivity was measured relative to a reference material of known reflectivity. By applying KirchofFs law to the result, the normal spectral emittance cm be determined [84,10]. 

As in the case of DT, diffuse reflectance (DR) can be measured in the mid-IR region with an integrating sphere [131, 141]. However, this technique is used mainly in reflectometry, where repeatable measurements with full hemispherical collection of radiation are needed [142]. Better performances, up to 12% efficiency, can be obtained using accessories with the so-called biconical optical configuration, which focuses the reflected radiation onto the IR detector. The SNR of such spectra is sufficient if such an accessory is used in conjunction with a FTIR spectrometer. The first DRIFT S accessory was described by Fuller and Griffiths in 1978 [143]. After that many forms of the DRIFTS accessories... 

This review is limited to reflectometers based on specular conic mirrors and it includes several unanticipated results. To our knowledge, this chapter represents the first comprehensive review of such devices. Previous reviews of reflectance instrumentation contain only a limited discussion of conic mirror devices (6, 7). It has been prompted by new developments that expand the scope of conic mirrors used for reflectometry. During the past decade, inexpensive PC- and workstation-based raytracing programs have become available that allow one to easily model the performance of both conic mirror and integrating sphere reflectometers. In this review we... 

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