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The nonuniformity in the response of the infrared imager, caused by the pixel-to-pixel responsivity variation, is determined with the help of the DRM. The DRM is based on at least three successively taken images of a radiation source. A first image (primary image) is taken from the source, then a second image is taken from the source with the field of view of the imager purposely shifted in the direction represented by the rows of the FPA and, finally, a third image is taken with the field of view of the imager purposely shifted in the direction represented by the columns of the FPA in relation to the primary image. From these three images a result matrix is generated which yields the respective differences between the radiance temperature responsivity values of all detector pixels of the FPA to a user-selected reference pixel. For the application of this method we distinguish between infrared imagers with actively cooled and/or actively temperaturestabilized FPAs on the one hand and infrared imagers with non-temperature-stabilized FPAs on the other hand, as the later ones generally exhibit larger temporal drifts in their detected radiance temperatures. |
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