Image courtesy of U Max UK Ltd.
Scanners use lights and colour filters on image sensors, or coloured lights (e.g. LEDs) to analyze the colours in reflection print or transparency originals. Some scanners can also scan colour film negatives, and either "print" them to create a pleasing image on the reference sRGB display (the most common approach), or estimate scene colours and encode them as scRGB.
The IEC has specified a method for the characterization of colour scanners for multimedia applications, to facilitate the creation of standard colour image data.