Precision Glass Moulding - Metrology and Quality Assurance

Metrology and Quality Assurance

Once process and tool have been developed, precision glass moulding has a great advantage over conventional production techniques. The majority of the lens quality characteristics are tool-bound. This means that lenses, which are pressed with the same tool and process, usually have only insignificantly small deviations. For example, an important characteristic of a lens is the form of the optical surface. In the case of aspherical lenses the measurement of optical surfaces is very difficult and connected to high efforts. Additionally, when working with tactile measurement systems there is always a risk that the optical surface might be scratched. For precision moulded lenses such measurements are only necessary for a small amount of sample lenses in order to qualify the tool. The series production can then be executed without further need for measurements. In this case, only the cleanliness of the optical surface has to be monitored. Another advantage is that the lens' center thickness can be estimated from the easily measurable edge thickness or by applying a contactless measurement system.