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arXiv 1404.7201astro-ph.IM
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用于相位掩模日冕仪的Lyot低阶波前传感器:原理、模拟与实验

Lyot-based Low Order Wavefront Sensor for Phase-mask Coronagraphs: Principle, Simulations and Laboratory Experiments

Garima Singh, Frantz Martinache, Pierre Baudoz, Olivier Guyon, Taro Matsuo, Nemanja Jovanovic, Christophe Clergeon

摘要:

高性能的日冕照相成像的微弱结构周围的明亮的恒星在小的角间距需要精细的控制,倾斜,倾斜和其他低阶像差。当这种误差发生在日冕仪的上游时,它们会导致星光泄漏,从而降低仪器的动态范围。这个问题以前已经解决了掩星日冕仪通过感知星光之前或在日冕仪焦平面。一种这样的解决方案,日冕仪低阶波前传感器(CLOWFS)使用部分反射焦平面掩模来测量Lyot型日冕仪的指向误差。为了解决低内工作角相位掩模日冕仪中没有反射焦平面掩模的指向误差,我们采用了CLOWFS技术。这种新概念依赖于由焦平面相位掩模衍射的星光被Lyot光阑反射到传感器,该传感器可靠地测量低阶像差,例如倾斜和倾斜。这种基于Lyot的反射式波前传感器是一种线性重建器,它可以通过相位掩模日冕仪提供高灵敏度的倾斜误差测量。仿真结果表明,采用真实的后自适应光学残差,瞄准误差的测量精度约为100%。对于四象限相位掩模,λ = 1.6微米时每模10^-2 λ/D。此外,我们还在实验室中演示了四象限相位掩模在638 nm处的开环测量指向精度为10^-2 λ/D。

英文摘要:

High performance coronagraphic imaging of faint structures around bright stars at small angular separations requires fine control of tip, tilt and other low order aberrations. When such errors occur upstream of a coronagraph, they results in starlight leakage which reduces the dynamic range of the instrument. This issue has been previously addressed for occulting coronagraphs by sensing the starlight before or at the coronagraphic focal plane. One such solution, the coronagraphic low order wave-front sensor (CLOWFS) uses a partially reflective focal plane mask to measure pointing errors for Lyot-type coronagraphs. To deal with pointing errors in low inner working angle phase mask coronagraphs which do not have a reflective focal plane mask, we have adapted the CLOWFS technique. This new concept relies on starlight diffracted by the focal plane phase mask being reflected by the Lyot stop towards a sensor which reliably measures low order aberrations such as tip and tilt. This reflective Lyot-based wavefront sensor is a linear reconstructor which provides high sensitivity tip-tilt error measurements with phase mask coronagraphs. Simulations show that the measurement accuracy of pointing errors with realistic post adaptive optics residuals are approx. 10^-2 lambda/D per mode at lambda = 1.6 micron for a four quadrant phase mask. In addition, we demonstrate the open loop measurement pointing accuracy of 10^-2 lambda/D at 638 nm for a four quadrant phase mask in the laboratory.

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