長(zhǎng)基線恒星光干涉技術(shù)中延遲線系統(tǒng)地設(shè)計(jì)與

吳楨等:長(zhǎng)基線恒星光干涉技術(shù)中延遲線系統(tǒng)的設(shè)計(jì)與實(shí)驗(yàn)中國(guó)科學(xué):物理學(xué)力學(xué)天文學(xué)2012年第42卷第2期圖7實(shí)驗(yàn)系統(tǒng)示意圖Figure7Schematicdiagramofexperimentalsystem.本預(yù)計(jì)采用裝調(diào)好后的系統(tǒng)(如圖6)進(jìn)行實(shí)驗(yàn);實(shí)驗(yàn)發(fā)現(xiàn)從雙頻激光干涉儀出來(lái)的光束經(jīng)拋物面反射鏡反射后其偏振特性被改變,雙頻激光干涉儀無(wú)法探測(cè)到,因此我們只好將雙頻激光干涉儀自帶的平面反射鏡直接安裝在PZT系統(tǒng)上(如圖7),但是工作原理是一樣的.采用這樣的實(shí)驗(yàn)系統(tǒng),我們首先測(cè)試了精密運(yùn)動(dòng)平臺(tái)的跟蹤誤差.只有精密運(yùn)動(dòng)平臺(tái)更新運(yùn)動(dòng)速度、PZT不動(dòng)的情況下,測(cè)試結(jié)果如圖4,表明精密運(yùn)動(dòng)平臺(tái)的跟蹤誤差為5m.假設(shè)觀測(cè)中心波長(zhǎng)為500nm,帶寬為5nm,為了使條紋可見(jiàn)度的損失小于1%,延遲補(bǔ)償?shù)木葢?yīng)好于相干長(zhǎng)度的十分之一,則光程差應(yīng)該維持在±3m內(nèi).小車(chē)的跟蹤速度每秒鐘更新一次,PZT系統(tǒng)補(bǔ)償頻率每秒鐘40次對(duì)上述的運(yùn)動(dòng)曲線進(jìn)行跟蹤.圖8為最終的跟蹤誤差,從圖8中可以看出,除了個(gè)別點(diǎn)的跟蹤誤差比較大(三角所示,大約為1m),整個(gè)系統(tǒng)的跟蹤精度是非常高的.這樣的跟蹤精度滿足±3m的要求.5結(jié)論通過(guò)實(shí)驗(yàn),在PZT校正頻率為40Hz時(shí),其跟蹤誤差在短時(shí)間內(nèi)基本處于±1m以內(nèi),滿足了實(shí)際觀測(cè)的要求.由于軟件采用動(dòng)態(tài)鏈接庫(kù)方式獲取數(shù)據(jù),圖8系統(tǒng)跟蹤誤差(單位:counts,1counts為50nm)Figure8Trackingerrorofthesystem(unit:counts,1countsis50nm).并通過(guò)網(wǎng)絡(luò)方式進(jìn)行數(shù)據(jù)傳輸,經(jīng)過(guò)測(cè)試,網(wǎng)絡(luò)傳輸?shù)臅r(shí)延會(huì)到達(dá)10ms以上,動(dòng)態(tài)鏈接庫(kù)獲取位置數(shù)據(jù)的程序段,執(zhí)行時(shí)間也在幾個(gè)ms級(jí),因此限制了整個(gè)控制系統(tǒng)的帶寬,無(wú)法再大幅度提高控制頻率,因此在現(xiàn)有的軟實(shí)時(shí)控制模式下要進(jìn)一步提高跟蹤精度,難度很大.國(guó)外已經(jīng)建成的干涉儀延遲線控制系統(tǒng)都是基于硬實(shí)時(shí)來(lái)實(shí)現(xiàn)的,控制頻率幾千Hz.延遲線要達(dá)到理想控制目標(biāo),應(yīng)該考慮硬實(shí)時(shí)的方法.本課題的研究表明我們采用的二級(jí)補(bǔ)償系統(tǒng)是可行的,下一步我們將繼續(xù)提高精密運(yùn)動(dòng)平臺(tái)的跟蹤精度以及運(yùn)動(dòng)的穩(wěn)定性;改變控制系統(tǒng),采用硬件實(shí)時(shí)控制.參考文獻(xiàn)王正明,徐家?guī)r,蕭金宏,等.天文光干涉測(cè)量.北京:科學(xué)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