Measurement technology for the machine-integrated determination of form deviations in optical surfaces

Quality inspection of ultra precise mold inserts is conducted outside the manufacturing machine by using phase-shifting interferometers (PSI). Reworking or a local correction of form deviations is difficult, because the mold inserts have to be repositioned in the machine tool. A promising way to overcome this problem is the machine-integration of the measurement system. But due to the sensitivity of PSI methods a direct integration into the machine tool is possible only to a limited extend. A FFT-based measurement technique was developed with reduced sensitivity. It was applied in a injection molding machine for form testing of a clamped mold insert with 80 degrees C process temperature.