Comparing Filters for Correction of Second Order Diffraction Effects in Hyperspectral Imagers

Second order diffraction effects often occur in hyperspectral instruments with dispersive elements. These second (and higher) order diffractions are typically unwanted, and should therefore be removed. One way of achieving this is by using a filter to block parts of the spectrum, calculate the second order light efficiency, and further use this to remove the estimated second order light in all datasets. Here, data from four different filters (two longpass and two shortpass) with three different types of illumination (a radiometric calibration source, cloudy sky and sunny sky) are compared. The short-pass filters used with the sunny sky give best results, while the longpass filters prove useful for validation purposes. A natural light source such as the Sun is shown to be beneficial compared to the calibration source (low intensity in UV) due to differences in spectra from real life measurements.