A device comprising a transparent window, an imaging unit, and a computing element coupled to said imaging unit, wherein said device is configured to allow soiling particles to accumulate on a surface of said transparent window, said imaging unit is configured to capture an image of said surface, and said computing element is configured to perform analysis of said image to determine a soiling level of said transparent window, wherein a surface of said transparent window may include reference marks enabling calibration of said image during said analysis. Additionally, a method of performing said analysis.