Laser color marking with color monitoring

Laser color marking on metal surface is a one step process which has high potential for product marking and decoration. Lasers are used for creating permanent colors without using any coatings or chemicals. Product differentiation and customization is achieved with programmable multi-color designs where design can be changed easily in marking software. Highly intricate design patterns can be generated using this technology. The principle of generating colors using lasers is formation of thin oxide layers by heating metal surface uniformly and reflection of white light from different thickness oxide layers which is perceived as different colors by the viewer. Although the laser color marking process is simple and flexible, one challenge that hinders its wider adoption is way to monitor generated color for consistency over marked area and repeatability from one surface to the another. This paper discusses laser color marking using pulsed IR disc laser. Colors across a broad spectrum has been successfully generated such as violet, blue, green, red, orange, brown, metallic colors such as gold and silver and shades of gray. An integrated camera based color monitoring system has been developed that can provide information on laser marked color consistency and repeatability using image processing techniques and its results will be presented.