In the past decade, scales for infrared spectral regular (specular) transmittance and reflectance have been established at the National Institute of Standards and Technology (NIST). Recently, we have developed an error budget based on direct evaluation of the sources of error in the measurement process. These include the detection system non-linearity, spatial non-uniformity of the detector, misalignment of components, inter-reflection between components, asymmetry of sample and reference measurements, and source polarization effects. Here we describe the evaluation of the linearity of our measurement system that includes a Fourier transform spectrophotometer, integrating sphere and MCT detector. From the linearity results, relative responsivity curves are also established.
|