Processing Flow of Optical Fabrication for Correcting Lenses

This paper presents the processing flow and results of optical fabrication for an optical correcting lens with a free-form surface, namely a free-form lens. Because a correcting lens has no rotation axes of symmetry and its surface cannot be expressed by a continuity equation, its processing technology is different with that of general aspheric lenses. The correcting lens was firstly formed from a glass workblank with flat face using diamond abrasion wheel with spherical shape, and then loose abrasive lapped and polished with oblique axis spherical tools to decrease the surface roughness and increase the surface accuracy based on the measuring result after forming. At the lapping and polishing stages, two processing methods are employed. One is to control the processing pressure, and the other is based on dwell time. Since high precision fabrication is closely related with high precision measuring, this paper also presents a high precision non-contact optical measuring method based on image transforming for correcting lenses. The effectiveness of the processing flow and technology is confirmed by an experiment in which a workblank is processed into a satisfying correcting lens.