Estimation and correction of wavefront aberrations using the self-coherent camera: laboratory results
Estimation and correction of wavefront aberrations using the self-coherent camera: laboratory results
复制标题
使用自相干相机估计和校正波前像差：实验室结果
DOI：
--
复制
发表时间：
2013
期刊：
影响因子：
--
通讯作者：
G. Rousset
中科院分区：
文献类型：
--
作者：
J. Mazoyer;P. Baudoz;R. Galicher;M. Mas;G. Rousset
上下文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。目标。这些波前误差的主动校正使用的可变形反射镜上游的日冕是强制性的，但传统的自适应光学器件受到限制的衍射路径像差。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。方法.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ELD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，并提取相关的复场。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。结果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。焦平面2 ~ 12 =D的对比度优于10 6，7 ~ 11 =D的对比度达到3：10 7（RMS）。看起来对比度水平主要受到由可变形反射镜的表面和检测器的动态产生的幅度缺陷的限制。结论.这些结果是有希望的未来应用到一个专门的空间使命的系外行星的特性。已经确定了一些可能的改进。
Context. 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. Aims. An active correction of these wavefront errors using a deformable mirror upstream of the coronagraph is mandatory, but conventional adaptive optics are limited by dierential path aberrations. Dedicated techniques have to be implemented to measure phase and amplitude errors directly in the science focal plane. Methods. First, we propose a method for estimating phase and amplitude aberrations upstream of a coronagraph from the speckle complex eld 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 eld. 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. Results. 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 =D and even 3:10 7 (RMS) between 7 and 11 =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. Conclusions. These results are promising for a future application to a dedicated space mission for exoplanet characterization. A number of possible improvements have been identied.