Noncontact Measurement Of Central Lens Thickness

The production of high-quality optical lenses from glass or polymer materials is subject to tight specification tolerances. Critical lens parameters such as central thickness have to be monitored frequently, during the production process. A non-contact, fast and precise optical measuring setup based upon a confocal chromatic probe can be used to measure central lens thickness ranging from 30um up to 25mm. The only parameters that have to be known up front are the radius of curvature of one lens surface, and the material used. This paper presents the measurement technique, illustrating it with some examples.