As use of aspheric elements has enabled opticians to fabricate optical systems with high performance, lightweight and compact size, the application of aspheric elements has been increasing rapidly in the recent years. The development of techniques for fabricating qualified products at a lower cost has thus become an urgent and challenging task to manufacturers. Like spherical and other optical elements, aspheric elements require both accurate figure and smooth surface simultaneously, but the changing curvature radius makes it impossible to apply the conventional global polishing method used for spherical elements. Usually the combination of loose abrasive polishing with an elastic polisher and compensation machining with a subaperture tool is employed in the final process and has been proved to be effective, but its low efficiency increases the costs of aspheric elements. Though use of computer as a controller has improved efficiency considerably and eliminates the need to depend on human skills, there are still limits imposed by loose abrasive polishing. Further advancements should therefore be made. In our research, metal-resin bonded diamond wheel was employed as tool for fixed abrasive polishing. By the application of electrolytic interval dressing, very smooth surface with a roughness of 1.0-1.6nmRa, 1.2-2.0nmRq was obtained for an aspheric surface made of BK7. The effects on figure accuracy improvement were also investigated in this study.
展开▼
