Dwell Time Algorithm Of Multi-mode Technique For Fabrication Of Large Aspherics

Aspheric optics can improve performance of optical systems, simplify thesystem architecture, improve image quality, and have a wide range of applications inmodern optical system. According to the diffraction theory, increasing the diameter ofthe optical system is an effective means to improve system resolution. With thedevelopment of optical technology, aspheric optical components used in the newgeneration of optical system increasingly large caliber, and put a higher demand foroptical processing technology. In this paper some technologies are researched indepth in order to improve the fabrication efficiency and accuracy during polishinglarge diameter aspheric reflect mirror.So far, internationally used method CCOS(Computer Controlled OpticalSurfacing) is based on Preston equation. Large aspheric mirror processing largeamount of material removal, so we require the CCOS process not only have highersurface convergence but also faster material removal efficiency. The removalefficiency of the traditional single processing method can not meet the processingdemands of the large caliber aspheric mirrors。This paper presents a multi-modecomposite processing methods to improve surface error convergence efficiency andmaterial removal efficiency at the same time to improve the processing efficiency oflarge-diameter aspherical optical mirror grinding and polishing stages. The papercompleted the research as following.1. Completion of the mathematical modeling of multi-mode processing technology analysis. Change the mathematical model of CCOS from deconvolutionprocess to matrix process. According to the characteristics of the multi-modetechnology established different algorithm based on Tikhonov regular method, leastsquares method, gradient descent method to solve dwell time problem. Baced onmatrix operations, optimize a plurality machining cycles simultaneously. Extend thetraditional single removing function optimization，achieve multi-removing functionoptimize solution process. Extend the range of dwell time, made the lager lap andthe smaller lap complementary during machining process. Simulated with realsurface error map，the results show that solving algorithm compared with theconventional single machining, the processing efficiency increased obviously. Andthe RMS convergence is almost the same. This technology can shorten theprocessing cycle and has strong practicability.2. Multi-objective optimization parameters introduced into the dwell timesolving process. Two aspects of the processing efficiency analysis based on theprocessing characteristics of large-aperture aspherical: efficiency of the materialremoval efficiency and surface error convergence. Researched the reason of middle、high frequency error of the surface and it’s affect to optical system. RaiseSlope-RMS as a parameter to evaluate surface quality. Use Slope-RMS in dwelltime algorithm. So we can establish a more effective tactics.In the end analyzed thesize of tool in TIF（tool influence function） library.