Research On Wave-front Errors Modification Technique With Ion Beam Figuring

Along with the development of science and technology, the performance of theoptical systems continues to rise, and has more stringent requirements on the imagequality. The wave-front errors affect the performance of the optical systems, which existin the systems inevitably. Currently, the primary means of compensation wave-fronterrors are the adaptive optics and the diffraction optical element correcting techniques.Wave-front errors modification technique is a method to compensate the static errorsthat the key optical components in the system are modified with high-precision opticalprocessing means. In order to compensate the wave-front errors, arbitrary shapes maybe required to process on the surfaces of the key optical components. As a novelnon-contact technique, Ion beam figuring is widely used in the processing ofhigh-precision optics because of the ability to achieve the removal at atomic level. Thepaper studies on wave-front errors modification technique with the means of ion beamfiguring. The major research efforts include the following points:1. The method to determinate the compensation surfaces from wave-front errors isanalyzed, the characteristics of the compensation surfaces is summed up, andZernike fitting method for the compensation surfaces is presented.2. Wave-front errors modification techniques with ion beam figuring are studied andsimulated. Firstly the Gaussian of BRF and fitting method for it is discussed. Achoice is made for scanning path base on the calculation characteristics. Thenaiming at the characteristics of compensation surfaces, two methods for solving thedwell time are discussed and analyzed by comparative simulation, RL convolutioniterative algorithm is proved its superiority in the process. Finally, the edgeextension in the convolution iterative process is optimized to improve the accuracyof processing, improving the capacity to restrain serious edge errors emerging in theprocessing of complex shapes.3. For the characteristics of wave-front errors modification for optical components with large relative aperture, the relationship between RBF and the angle ofincidence is analyzed, the polynomial fitting method is presented to establish themodel for the relationship based on experiments, and a reasonable compensation ismade for the wave-front errors modification of large relative aperture opticalcomponents.4. The compensation surfaces in the wave-front errors modification may be acomposition of various frequency bands, so the reasonable choices must be madebased on the processing capacity of RBF in modification. The processing capacityof RBF for the surface with any single frequency is analyzed theoretically, and aconclusion is drawn that Gaussian RBF achieves modification for any frequency atthe expense of the extra removal rate. From the point of the processing efficiency,the relationship between dwell time and frequency of the surface processed isanalyzed, providing a new basis for the choice of RBF in the processing of arbitrarysurfaces.5. Aiming at the wide-band distribution characteristics of compensation surfaces, afiltering optimization of surface errors is proposed based on the analysis ofprocessing capacity of RBF. In this method, the surfaces errors are filtered byGaussian low-pass, and the effects for dwell time are reduced, which are caused bythe high frequency sections beyond the RBF efficiency, thus to improve theefficiency of wave-front errors modification with ion beam figuring.6. Based on the theories and methods established, experiments for the low order, highorder wave-front errors modification with ion beam figuring are done, the processcapacity of ion beam figuring for low order surfaces is verified well in thewave-front errors modification, and for the high order ones, the process capacityalso is verified at a certain extent.