| 摘要 |
<p>A calibration standard for use with an infrared optical absorption measurement gauge comprises an assembly comprising an optical interference filter (22) and one or more optical elements. The interference filter has spectrally selective properties so that all but a selected spectral band is reflected by the filter towards the detectors of the gauge (not shown). The transmitted band is selectively absorbed by the optical element(s) which are spectrally unselective and also directed towards the detectors of the gauge. The position and strength of the selected band can thereby be adjusted to simulate an absorption spectrum, i.e. a corresponding spectral band which is characteristic of the absorption spectrum of a material (7) under measurement. The standard is used to calibrate the absorption measurement gauge.</p> |
