| Plane mirror is a kind of optical component with simpler structure in the mirrorfamily, and it is applied in various optical field. This article did some investigation onsome plane mirror properties, mainly focused on the flatness inspection, flatnesscontrol in polishing process and the flatness change impacted by coating process.Firstly, about the mirror flatness inspection tester, most of the local and foreigncompanies select ZYGO laser interferometer as the first choice. We investigated thecorrelation between the traditional inspection method, testplate inspection, and theZYGO interferometer method, including the correlation between POWER, PV, SAG,IRR and N, N.Secondly, about the method used for plane mirror polishing, we focused on thetraditional polishing technique considering the matureness, stability and cost. Wediscussed different steps in traditional polishing, including mould making, polishpowder and slurry selection, polishing, clean and demould. And we also demonstratedthe different mould repair skill under different flatness.Finally, we studied the flatness change after film coating. There are many factorswhich may impact the mirror flatness after film coating, we mainly discussed it in thefollowing four items:1.The residual stress of thin film makes the flatness of mirror substrate changed. Wecan delegate some coater to run different level of substrate flatness to reduce theimpact of flatness of substrate, and SiO2film also can be coated on mirror backsideto adjust the amount of flatness change.2.Sometimes the faults in the film design makes the flatness measure value cannotrepresent the actual flatness of the mirror after coating. The film stake design mustbe adjusted by some experiment to eliminate the impact.3.The impact of coating fixture step to the flatness was investigated. There is asolution of increasing the substrate length and modifying the coating fixture.4.The impact of substrate position on the fixture also was discussed. |
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