Embodiments include a method of detecting obscuration of an optical window in an IR imaging system, the IR imaging system comprising processing circuitry and a plurality of spatially and spectrally distinct optical channels, each optical channel including a set of lenses that focus incident IR light on a respective portion of an optical detector system, the method comprising: with the processing circuitry, analyzing a first image and a second image, received from respective first and second optical channels of the plurality of spatially and spectrally distinct optical channels, to detect obscuration that may degrade operation of the IR imaging system; with the processing circuitry, creating first and second gradient images from the first and second images, respectively; with the processing circuitry, cross-correlating the first and second gradient images; and with the processing circuitry, determining that at least one cross-correlation between the first and second gradient images exceeds a first window obscuration threshold and that the first and second gradient images exceed a second window obscuration threshold and, in response, providing an alert that the optical window is obscured.