Systems, devices, and methods for detecting a contaminant on a substrate are discussed herein. Variations of such systems, devices, and methods may include one or more illumination sources that emit illumination at one or more desired wavelength ranges to illuminate one or more areas on the substrate； where the desired wavelength range is one that is absorbed by the contaminant while causing the substrate to fluoresce. Such fluorescence may be detected with a visible-spectrum detector, which will also detect the contaminant as a darker contrast area against the fluorescence. In some variations, an illumination source includes a broad-spectrum light source and a waveband filtering device that filters all but the desired illumination waveband out of the broad-spectrum light generated by the broad-spectrum light source.
