In the manufacturing process of aspheric glass lenses the grinding step plays a key role both in respect of the final quality of the polished lens as well as in respect of manufacturing costs. Therefore, the form of the grinded surface must be measured with high precision. The typically used tactile measuring machines provide sufficient precision regarding depth resolution but suffer from limited lateral resolution. In particular it is not possible to detect surface and sub-surface damages which essentially influence the duration of the subsequent polishing process. In order to detect these damages we set up and tested a scanning short-coherence interferometer very similar to optical coherence tomography. The aspheric lens under test is mounted on a rotation stage which can be translated in the lateral direction. The sensor beam of the interferometer is focused onto the sample and can be moved along the axial direction. The precision of the depth measurement is 0.25μm, the lateral positioning precision is 2μm. The system is used to optimize the grinding process for aspheric lenses to minimze sub-surface damages and therefore to maximize processing speed.

Date Published: 14 September 2007
PDF: 10 pages
Proc. SPIE 6671, Optical Manufacturing and Testing VII, 66710X (14 September 2007); doi: 10.1117/12.732019

Published in SPIE Proceedings Vol. 6671:
Optical Manufacturing and Testing VII
James H. Burge; Oliver W. Faehnle; Ray Williamson, Editor(s)