Research On The CCOS Polishing Theory And Technology Of Optical Aspheric Surface

The modern optical systems are developing into the direction of ultra-precision,large-caliber,aspheric surfaces and off-axis surfaces.And the requirements for optical components are getting higher and higher.The widespread application of precision optical components has played a significant role in promoting the development of ultraprecision polishing.Due to the numerous advantages and strategic status of highsurface-accuracy optical curved elements,how to use ultra-precision polishing methods to fabricate optical curved elements with excellent surface quality has become a key research direction of scholars in various countries.As an important branch of ultra-precision polishing,computer-controlled optical surfacing technology(CCOS)is widely used,with relatively mature technologies,high fabricating accuracy and efficiency.As the theoretical basis of CCOS technology,Preston equation and Hertz contact theory have been recognized by most scholars after decades of verification.However,in actual polishing processes,the trajectory generation algorithm and the form of the trajectory have various scenarios due to different curvature changes of different curved surfaces and different shape of tool heads.The main task of this paper is to deeply study the trajectory generation algorithm and trajectory form,and propose reasonable and targeted polishing trajectories for rotating aspheric and off-axis parabolic surfaces.The research content of this article includes the following sections:1.The CCOS technology generally controls the removal of track points by controlling the dwell time of track points on the workpiece surface under the premise of setting process parameters such as polishing pressure and tool head speed.However,the machine tool directly controls the spindle feed speed.For machine tools using speed control mode,during the process of moving polishing,controlling the spindle feed speed is more accurate than controlling the dwell time of track points.In view of this situation,a mobile polishing material removal model based on the dwell length integral method was derived in this paper.2.The transition area of many tracks often exceeds the preset polishing amount due to multiple polishing by the tool head,which affects the surface accuracy.In view of the trajectories with right-angle corners,such as the scanning trajectory and Hilbert trajectory,this paper researched the removal of the spherical tool head in the right-angle transition area in three cases,and summarized the right-angle transition area removal model.3.In view of the problem that the spatial row spacing of adjacent trajectories is not unreasonably distributed by projecting the Archimedes spiral trajectory and the concentric circle trajectory onto the three-dimensional surface,this paper proposed the equal dwell length trajectory generation algorithm and planed on the rotating aspheric surface the adaptive spatial line spacing spiral trajectory and the adaptive spatial line spacing concentric circle trajectory based on the algorithm generated.4.For the case that the ratio of the vertical height and diameter of the off-axis paraboloid is too large to be suitable for direct polishing,the coordinate transformation method is applied in this paper to significantly reduce the ratio of the vertical height and diameter,which makes the off-axis paraboloid easy to polish.In view of the asymmetry of curvature change of off-axis paraboloid,this paper planed an adaptive spatial line spacing ellipse trajectory.5.The polishing experiment of off-axis paraboloid was carried out.And the polishing allowance calculation model was established based on MATLAB software.Finally,the polishing removal effect of off-axis paraboloid was verified by the adaptive spatial line spacing ellipse trajectory.