A technique for resolving the spectral response of a wide-band infrared measuring instrument from measurements without the need for a spectrally tuneable radiation source

Abstract

A technique is presented in which the spectral response of a wide-band infrared measuring instrument is obtained by means of calibration type measurements of a blackbody at various temperature settings and the application of a mathematical technique to these measurements. Successful application of the developed technique is enabled by Tikhonov regularization, which ensures a stable solution to the ill-posed problem of the Fredholm integral equation of the first kind describing the blackbody measurements made by the instrument. The quality of the solution strongly depends, however, on the accuracy of the measurements and the accuracy of the modelled spectrum in describing the emission from the blackbody source.

The technique is studied by means of an application to modelled results of instrument measurements, and is then applied to actual measurements made with an infrared camera. It is shown that the technique can, in the absence of specific manufacturer supplied information of the instrument and specialized equipment, be an alternative to the theoretical calculation of the instrument response spectrum or to an experimental determination of the instrument spectral response during which measurements are made of a spectrally tuneable radiation source like a blackbody and monochromator.