US Patent 11833993 Postprocessing of seat belts for adding dye

Methods for marking a seat belt webbing with an infrared compound are described herein. The methods comprise ablating a surface of the seat belt webbing by directing one or more laser pulses toward the seat belt webbing; and coating the ablated surface of the seat belt webbing with the infrared compound, wherein the infrared compound increases absorptivity or reflectivity of the seat belt webbing to infrared radiation. Methods for optically monitoring operation of the seat belt webbing in a vehicle and distinguishing between proper positioning and improper positioning of the seat belt webbing are also disclosed.