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    Fabrication technology of astronomical mirror with large aperture and high accuracy
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    Update time: 2009-09-01
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     Astronomical mirror become much more larger in size,much more thiner in thickness and much more deeper in asphericity as well as much more higher in accuracy in orde to meet the demand of modern astronomical optical telescope。The subject research fabrication method of thinner mirror with large aperture and apply active optics technology to fabrication of mirror with deeper asphericity。That will make China catch up with march of the world on astronomical optical fabrication technology。

       It is a national key project in the Ninth-Five Year plan period funded by NSFC。

       The project group firstly developed computer-controlled active polishing technogy and fabricated polishing machine applied this technogy in China and successfully fabricated diameter 450mm active polishing disc as well as diameter 910mm paraboidal mirror with F ratio=2 and with surface accuracy of 1/30 wavelength(RMS)。Difficult problem for high spacial frequence error of surface during mirror fabrication of large aperture and deep asphericity as well as difficult problem during fabrication of large aperture tilted-axis aspherical mirror were solved。

       The project group firstly developed fabrication technogy of very thiner mirror with flexible supporting and fabrication method of large aperture very thiner mirror with computer-controlled close-loop active optics technogy。Very thiner hexagonal plano mirror with 1100mm of diagonal,25mm in thickness (applied to LAMOST) was successfully fabricared。Adopting similar fabrication method as that of diameter 4-8 meter mirror,very thinner spherical mirror which is 1035mm in diameter and 26mm in thickness with surface accuracy of 1/27 wavelength(RMS) was successfully fabricared。That indicates that difficult problem of lower rigidity during fabrication of very thinner mirror is successfully solved。

      

    Nanjing Institute of Astronomical Optics & Technology ,National Astronomical Observatories ,CAS