长基线恒星光干涉技术中延迟线系统地设计与

吴桢等:长基线恒星光干涉技术中延迟线系统的设计与实验中国科学:物理学力学天文学2012年第42卷第2期图7实验系统示意图Figure7Schematicdiagramofexperimentalsystem.本预计采用装调好后的系统(如图6)进行实验;实验发现从双频激光干涉仪出来的光束经抛物面反射镜反射后其偏振特性被改变,双频激光干涉仪无法探测到,因此我们只好将双频激光干涉仪自带的平面反射镜直接安装在PZT系统上(如图7),但是工作原理是一样的.采用这样的实验系统,我们首先测试了精密运动平台的跟踪误差.只有精密运动平台更新运动速度、PZT不动的情况下,测试结果如图4,表明精密运动平台的跟踪误差为5m.假设观测中心波长为500nm,带宽为5nm,为了使条纹可见度的损失小于1%,延迟补偿的精度应好于相干长度的十分之一,则光程差应该维持在±3m内.小车的跟踪速度每秒钟更新一次,PZT系统补偿频率每秒钟40次对上述的运动曲线进行跟踪.图8为最终的跟踪误差,从图8中可以看出,除了个别点的跟踪误差比较大(三角所示,大约为1m),整个系统的跟踪精度是非常高的.这样的跟踪精度满足±3m的要求.5结论通过实验,在PZT校正频率为40Hz时,其跟踪误差在短时间内基本处于±1m以内,满足了实际观测的要求.由于软件采用动态链接库方式获取数据,图8系统跟踪误差(单位:counts,1counts为50nm)Figure8Trackingerrorofthesystem(unit:counts,1countsis50nm).并通过网络方式进行数据传输,经过测试,网络传输的时延会到达10ms以上,动态链接库获取位置数据的程序段,执行时间也在几个ms级,因此限制了整个控制系统的带宽,无法再大幅度提高控制频率,因此在现有的软实时控制模式下要进一步提高跟踪精度,难度很大.国外已经建成的干涉仪延迟线控制系统都是基于硬实时来实现的,控制频率几千Hz.延迟线要达到理想控制目标,应该考虑硬实时的方法.本课题的研究表明我们采用的二级补偿系统是可行的,下一步我们将继续提高精密运动平台的跟踪精度以及运动的稳定性;改变控制系统,采用硬件实时控制.参考文献王正明,徐家岩,萧金宏,等.天文光干涉测量.北京:科学出版社,1996LawsonPR,ThompsonBJ.SelectedPapersonLongBaselineStellarInterferometry.Bellingham,WA:SPIEOpticalEngineeringPress,1997GarciaPJV,HenningT,GlindemannA.TheveryLargeTelescopeInterferometer––ChallengesfortheFuture.Dordrecht:Springer,2007LawsonPR.Principlesoflongbaselinestellarinterferometry.CourseNotesfromthe1999MichelsonSummerSchool.Pasadena:NationalAeronauticsandSpaceAdministration,JetPropulsionLaboratory,CaliforniaInstituteofTechnology,1999MonnierJD.Opticalinterferometryinastronomy.RepProgPhys,2003,66:789–857JankovS.Astronomicalopticalinterferometry1.MethodsandInstrumentation.SerbAstronJ,2010,181:1–17MartinC.RecentastrophysicalresultsfromtheVLTI.Messenger,2005,121:52–55LawsonPR.Advancesinsciencewithstellarinterferometers2004–2006.ProcSPIE,2006:626801MonnierJD,ZhaoM,PedrettiE,etal.Imagingthesurfaceofaltair.Science,2007,317(5836):342–345ZhaoM,GiesD,MonnierJD,etal.FirstresolvedimagesoftheeclipsingandinteractingBinarybLyrae.AstrophysJ,2008,684:L95–L98YoungJS,BaldwinJE,BasdenAG,etal.AstrophysicalresultsfromCOAST.ProcSPIE,2001,4838:369–378Karovska

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Designandexperimentofthedelaylinesystemforlongbaselinestellarinterferometry†WUZhen1,2*,LIChao1,2,3,LINXieJia1,2,3,ChenYi1,2&WANGJiaNing1,21NanjingInstituteofAstronomicalOptics&Technology,NationalAstronomicalObservatories,ChineseAcademyofSciences,Nanjing210042,China;

2KeylaboratoryofCASforAstronomicalopticsandtechnology,ChineseAcademyofSciences,Nanjing210042,China;

3GraduateUniversityofChineseAcademyofSciences,Beijing100049,ChinaOpticaldelaylinesystemusedtocompensatethegeometricopticalpathdifferenceisoneofkeysubsystemofthelongbaselinestellarinterferometer.AtwostagescompensationdelaylinesystemdevelopedbyNanjingIns