Investigations on the production of optical freeforms applying the advanced wheel polishing process

Abstract

The growing interest in providing additional degrees of freedom to the design of high-end optical systems has led to an increased demand for freeform optical elements. The efficient fabrication of such elements requires a polishing process that provides high removal rates and a stable removal function while working with a relatively small spot size. Taking these constraints into consideration this paper focuses on the successful implementation of polishing processes applying the A-WPT (Advanced Wheel Polishing Tool) technology. Addressing the requirements regarding its removal characteristics as mentioned before, it represents an appropriate choice for providing an efficient pre-polishing as well as corrective polishing technique. In order to maintain perpendicularity towards the freeform surface to be polished, the A-WPT is run on a 5-axis simultaneous machining system. First investigations of the achieved surface accuracy after pre-polishing were carried out as well as an assessment of residual surface features within different spatial frequency regions. In addition, the polished surface is being checked for remaining SSD using an OCT technique.