The absolute calibration of mid-infrared transmittance standards Original Research Article

The National Physical Laboratory (NPL) uniquely has 40 years’ experience in pioneering, developing instruments and exploiting the spectroscopic advantages of the Fourier transform technique. This has allowed an objective and knowledgeable appraisal of the Fourier transform technique for ordinate standards work. At present not enough is known of the ways in which the many and complicated categories of systematic error in such instruments can be identified, separated, evaluated and corrected for. Thus at NPL grating spectrophotometers are still used to determine, maintain and disseminate transmittance standards for the mid-infrared spectral region. This allows well-established methods developed in UV/visible region work to be adapted and used to minimise and where necessary correct for the residual systematic errors.