变迹光瞳Lyot冠状放大器的微点变迹器的设计、分析和测试
Design, analysis and test of a microdots apodizer for the Apodized Pupil Lyot Coronagraph
摘要：
日冕测量技术需要用未来的超大望远镜来探测系外行星。一个概念，变迹光瞳Lyot冠状（APLC），是结合在入口孔径和焦平面Lyot不透明掩模的变迹。本文介绍了一种针对近红外优化的微点切趾器的制造和测试。这项工作的目的是证明二元切趾器用于APLC的可行性和性能。这项研究也是相关的任何冠状动脉使用振幅瞳孔变迹。使用半色调点处理设计了一种二进制变迹器，其中计算具有0%或100%透射率的像素的二进制阵列以适应所需的连续透射率，即通过改变不透明像素和透明像素的相对密度来获得局部透射率控制。使用误差扩散算法来优化最接近所需场传输的像素分布。该原型在近红外条件下进行了日冕仪测试，其透射轮廓与理论形状的一致性在3%以内，并且是消色差的。观察到的切趾和日冕图像与理论一致。然而，二进制切趾器引入作为像素大小的函数的高频噪声。数值模拟被用来指定像素大小，以尽量减少这种影响，并通过实验验证。本文证明了二元切趾器非常适合用于高对比度成像日冕仪。像素大小的正确选择很重要，必须考虑到科学的视野。
英文摘要：
Coronagraphic techniques are required to detect exoplanets with future Extremely Large Telescopes. One concept, the Apodized Pupil Lyot Coronagraph (APLC), is combining an apodizer in the entrance aperture and a Lyot opaque mask in the focal plane. This paper presents the manufacturing and tests of a microdots apodizer optimized for the near IR. The intent of this work is to demonstrate the feasibility and performance of binary apodizers for the APLC. This study is also relevant for any coronagraph using amplitude pupil apodization. A binary apodizer has been designed using a halftone dot process, where the binary array of pixels with either 0% or 100% transmission is calculated to fit the required continuous transmission, i.e. local transmission control is obtained by varying the relative density of the opaque and transparent pixels. An error diffusion algorithm was used to optimize the distribution of pixels that best approximates the required field transmission. The prototype was tested with a coronagraphic setup in the near IR. The transmission profile of the prototype agrees with the theoretical shape within 3% and is achromatic. The observed apodized and coronagraphic images are consistent with theory. However, binary apodizers introduce high frequency noise that is a function of the pixel size. Numerical simulations were used to specify pixel size in order to minimize this effect, and validated by experiment. This paper demonstrates that binary apodizers are well suited for being used in high contrast imaging coronagraphs. The correct choice of pixel size is important and must be adressed considering the scientific field of view.
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