Banknote Sorter: Multispectral Imaging and Mechatronics
A Banknote Sorter is a high-speed mechatronic device used by banks and casinos to count, authenticate, and grade the physical fitness of currency.
1. Multispectral Authentication
As notes pass through at speeds up to $1,000$ notes per minute, they are scanned using UV, IR, and Visible Light spectrums. The system looks for "Security Threads," fluorescent inks, and "Infrared Meta-merism" (ink that disappears under IR light) to identify counterfeits.
2. Magnetic and Ultrasonic Sensing
To detect "Taped" or "Composed" notes (made from two different bills), the sorter uses Ultrasonic Sensors to measure the thickness of the paper at every point. Magnetic sensors scan for the presence of iron-oxide inks used in specific denominations.
3. Fitness Sorting and Soil Detection
The sorter evaluates the "Fitness" of the note—checking for holes, tears, or "soiling" (dirt accumulation). Using Image Processing Algorithms, the device determines if a note should be returned to circulation or "shredded" by the central bank.