MidOpt® Bandpass filters can be used in conjunction with a 365nm UV light source to capture fluorescence emissions at a given wavelength range. In this case, a seal on a credit card emits light back to the sensor at roughly 450-470nm (Blue). A MidOpt® BP470 Blue Bandpass Filter is then used to isolate only the blue fluorescence while darkening everything else in the image, creating excellent contrast.