Devices image radiation from a scene that includes two materials with spectral characteristics in two different wavelength regions. A lens forms an image of the scene on a detector that includes an array of elements. A filtering arrangement integrated with the detector allows half of the detector elements to detect radiation in one of the wavelength regions and the other half of the detector elements to detect radiation in the other wavelength region. Each detector element can be constructed from two different sub-elements that are sensitive to radiation in one of the respective wavelength regions. A blackbody source positioned within the devices reduces drift induced by changes to the environment surrounding the devices. The blackbody source projects radiation onto a region of the detector that does not receive radiation from the scene. Pixel signals produced from the scene radiation are modified based on pixel signals produced from the blackbody.