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arXiv 1306.5561astro-ph.IM
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用自相干相机估算和校正波前像差:实验室结果

Estimation and correction of wavefront aberrations using the self-coherent camera: laboratory results

J. Mazoyer, P. Baudoz, R. Galicher, M. Mas, G. Rousset

摘要:

对系外行星的直接成像需要非常高的对比度,这是使用日冕仪获得的。但是残留的准静态像差在日冕下游的焦平面上产生了斑点,掩盖了行星。这个问题出现在地面仪器和空间望远镜中。在日冕镜上游使用可变形反射镜对这些波前误差进行主动校正是强制性的,但是传统的自适应光学受到差分路径像差的限制。必须采用专用技术直接在科学焦平面上测量相位和振幅误差。首先,我们提出了一种方法,用于估计相位和振幅像差上游的日冕从散斑复杂的领域在下游焦平面。然后,我们提出了自相干相机,它利用光的相干性对焦平面散斑进行空间编码,并恢复相关的复场。这使我们能够在闭环中估计和补偿日冕上游的像差。我们进行了数值模拟以及实验室测试,使用四象限相位掩模和32 x32致动器变形镜。我们在实验室中展示了我们实现稳定闭环并补偿相位和幅度准静态像差的能力。我们确定了最适合的参数值来实现我们的技术。在焦平面中,在2和12 λ/D之间的对比度优于10-6,在7和11 λ/D之间的对比度甚至达到3.10-7(RMS)。对比度水平似乎主要受到可变形镜表面产生的振幅缺陷和检测器动态的限制。这些结果是有希望的未来应用到一个专门的空间任务的系外行星的特性。已经确定了一些可能的改进。

英文摘要:

Direct imaging of exoplanets requires very high contrast levels, which are obtained using coronagraphs. But residual quasi-static aberrations create speckles in the focal plane downstream of the coronagraph which mask the planet. This problem appears in ground-based instruments as well as in space-based telescopes. An active correction of these wavefront errors using a deformable mirror upstream of the coronagraph is mandatory, but conventional adaptive optics are limited by differential path aberrations. Dedicated techniques have to be implemented to measure phase and amplitude errors directly in the science focal plane. First, we propose a method for estimating phase and amplitude aberrations upstream of a coronagraph from the speckle complex field in the downstream focal plane. Then, we present the self-coherent camera, which uses the coherence of light to spatially encode the focal plane speckles and retrieve the associated complex field. This enable us to estimate and compensate in a closed loop for the aberrations upstream of the coronagraph. We conducted numerical simulations as well as laboratory tests using a four-quadrant phase mask and a 32x32 actuator deformable mirror. We demonstrated in the laboratory our capability to achieve a stable closed loop and compensate for phase and amplitude quasi-static aberrations. We determined the best-suited parameter values to implement our technique. Contrasts better than 10-6 between 2 and 12 lambda/D and even 3.10-7 (RMS) between 7 and 11 lambda/D were reached in the focal plane. It seems that the contrast level is mainly limited by amplitude defects created by the surface of the deformable mirror and by the dynamic of the detector. These results are promising for a future application to a dedicated space mission for exoplanet characterization. A number of possible improvements have been identified.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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