大芯径光纤出射环形斑谱线分析
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摘要
光纤光谱的效率损失主要来源之一是光纤的焦比退化,并且往往还在光谱成像时因焦比退化产生环形出射斑,从而使得光纤传输效率降低,并影响色散之后的谱线轮廓。实验获取郭守敬望远镜调试阶段的大芯径光纤因焦比退化产生的出射环型斑貌,结合CCD光谱图像特点实施轮廓拟合抽谱方法,把二维CCD光谱图像转换成一维光谱,选取望远镜红端数据进行模拟,采样点在500~600 nm波段范围,在该波段中有铁的发射线。通过与获得的环形斑轮廓卷积研究焦比变化对铁发射线峰的影响。最后,正确阐明在正式巡天观测时主镜前悬挂平场漫反射屏消除环形斑引发的偏差的效果。
The introduction of optical fiber into astronomical telescope observation combined with big data technology has improved the development of astronomy.Multi-target optical fiber measurement technology is mainly affected by the optical fiber transmittance and focal radio degradation( FRD) characteristics.During the rotation of the telescope,the fiber will be flexural deformed between the focal plane and the spectrograph,meanwhile,if the convergence center of the beam from the telescope is not aligned with the main axis of optical fiber,the FDR will be changing with it,which greatly affect the reception of the spectrograph.One of the main sources of fiber spectral efficiency loss is caused by FRD of the fiber,which often results in ringshaped emergent image.In this paper,we obtained the ring-shaped emergent images produced by FRD of large diameter fibers in Guo Shou-Jing( LAMOST) telescope during the commissioning.According to the character CCD image,we applied spectral extraction method based on profile fitting to convert the two-dimensional CCD image into one-dimensional spectrum.We selected LAMOST spectra in wavelength range around 500-600 nm,in which there were Fe emission lines.Then we studied the effect of the FRD on the Fe emission line peaks through convoluting with the obtained ring-shaped emergent profile.Finally,we discussed using flat diffuse screen before the main mirror Mb to eliminate annular plaque-induced deviation caused by the effect of ringshaped emergent profile.
The introduction of optical fiber into astronomical telescope observation combined with big data technology has improved the development of astronomy.Multi-target optical fiber measurement technology is mainly affected by the optical fiber transmittance and focal radio degradation( FRD) characteristics.During the rotation of the telescope,the fiber will be flexural deformed between the focal plane and the spectrograph,meanwhile,if the convergence center of the beam from the telescope is not aligned with the main axis of optical fiber,the FDR will be changing with it,which greatly affect the reception of the spectrograph.One of the main sources of fiber spectral efficiency loss is caused by FRD of the fiber,which often results in ringshaped emergent image.In this paper,we obtained the ring-shaped emergent images produced by FRD of large diameter fibers in Guo Shou-Jing( LAMOST) telescope during the commissioning.According to the character CCD image,we applied spectral extraction method based on profile fitting to convert the two-dimensional CCD image into one-dimensional spectrum.We selected LAMOST spectra in wavelength range around 500-600 nm,in which there were Fe emission lines.Then we studied the effect of the FRD on the Fe emission line peaks through convoluting with the obtained ring-shaped emergent profile.Finally,we discussed using flat diffuse screen before the main mirror Mb to eliminate annular plaque-induced deviation caused by the effect of ringshaped emergent profile.
引文
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[2]Horton A J,Blandhawthorn J.Coupling light into optical fibres near the diffraction limit[C]//Proceedings of SPIE.2006.
[3]Luo A L,Zhang H T,Zhao Y H,et al.Data release of the LAMOST pilot survey[J].Research in Astronomy and Astrophysics,2012,12(9):1243-1246.
[4]涂洋,张彦霞,赵永恒,等.光谱分析软件在天文学研究中的应用[J].天文研究与技术,2016,13(1):124-132.Tu Yang,Zhang Yanxia,Zhao Yongheng,et al.Application of spectral analysis softwares in Astronomy[J].Astronomical Research&Technology,2016,13(1):124-132.
[5]王森,朱冰.大芯径光谱传光光纤焦比退化特性研究[J].光电工程,2011,38(7):17-27.Wang Sen,Zhu Bing.Focal ratio degradation of large core spectrum light-transmitting optical fiber[J].Opto-Electronic Engineering,2011,38(7):17-27.
[6]穆丹丹,朱永田,张凯.天文光纤机械扰模器调制环形光场实验研究[J].应用光学,2012,33(5):997-999.Mu Dandan,Zhu Yongtian,Zhang Kai.Modulation of annular light distribution by mechanical fiber scrambler[J].Journal of Applied Optics,2012,33(5):997-999.
[7]Bryant J J,Bland-Hawthorn J,Fogarty L M R,et al.Focal ratio degradation in lightly fused hexabundles[J].Monthly Notices of the Royal Astronomical Society,2014,438(1):869-877.
[8]Yan Y X,Wang R C,Sun W M,et al.Investigation of focal ratio degradation caused by stress in large-core astronomical fibers[C]//2013 International Conference on Optoelectronics and Microelectronics.2013:174-176.
[9]陈建军,白仲瑞,李广伟,等.光纤转动引起光纤光谱效率变化与改正[J].光谱学与光谱分析,2015,35(4):1099-1102.Chen Jianjun,Bai Zhongrui,Li Guangwei,et al.Correction of fiber throughput variatioon due to the focal ratio degradation[J].Spectroscopy and Spectral Analysis,2015,35(4):1099-1102.
[10]Yan R B,Tremonti C,Bershady M A,et al.SDSS-IV/MaNGA:spectrophotometric calibration technique[J].The Astronomical Journal,2016,151(1):8(18pp).
[11]董健,王坚,邓小超,等.LAMOST观测控制系统用户界面设计[J].天文研究与技术---国家天文台台刊,2011,8(3):272-278.Dong Jian,Wang Jian,Deng Xiaochao,et al.Design of user interfaces for the LAMOSTobservatory control system[J].Astronomical Research&Technology---Publications of National Astronomical Observatories of China,2011,8(3):272-278.
[12]汪梦欣,陈笑然,罗阿理,等.前照条件下LAMOST焦面板光纤单元定位精度检测系统设计[J].天文研究与技术---国家天文台台刊,2014,11(2):157-164.Wang Mengxin,Chen Xiaoran,Luo Ali,et al.Design of a system for measuring positioning accuracies of optical-fiber units on the LAMOST focal plane using front light sources[J].Astronomical Research&Technology---Publications of National Astronomical Observatories of China,2014,11(2):157-164.
[13]Sun W M,Yan Y X,Wang J,et al.Phase disturbing speckle-suppressing method in fiber metrology under coherent illumination[C]//Proceedings of SPIE.2015.