Nulling stellar coronagraph using liquid-crystal device
Nulling stellar coronagraph using liquid-crystal device
复制标题
使用液晶装置的恒星日冕仪归零
DOI：
10.1117/12.457651
复制
发表时间：
2003
影响因子：
9.2
通讯作者：
N. Hashimoto
中科院分区：
文献类型：
--
作者：
N. Murakami;N. Baba;T. Ishigaki;N. Hashimoto
零星日冕仪被提出用来探测离亮点状恒星非常近的暗淡物体，特别是太阳系外的行星。零星日冕仪的原理是对来自恒星的光线造成破坏性干涉。已经提出了几种使干涉法归零的方法。零位干涉术的关键是如何在较宽的波长范围内产生π相移。本文提出了一种利用偏振干涉实现消色差π相移的方法。当两束光束通过不同的偏振器时，当这些偏振器被放置在相互正交的偏振器和检偏器之间时，它们之间的相位差为π弧度。我们采用铁电液晶(FLC)器件来转换入射光束的偏振方向。该器件被视为具有延迟π的双折射器件，即半波片。FLC器件形成四象限结构，放置在偏振器和分析器之间。通过适当固定四象限FLC的光轴，可以使入射的线偏振光部分旋转正负45°。
Nulling stellar coronagraph has been proposed to detect faint objects very close to a bright point-like star, especially extra-solar planets. The principle of the nulling stellar coronagraph is to cause destructive interference for the light from a star. There have been proposed several methods for nulling interferometry. The key point of the nulling interferometry is the way to produce π-phase shift over wide range of wavelength. Here we propose a method for realizing achromatic π-phase shift utilizing polarization interference. The phase difference between two light beams that pass through different polarizers is π radians when these polarizers are placed between mutually orthogonal polarizer and analyzer. We adopt a ferroelectric liquid-crystal (FLC) device to convert the polarization direction of the incident beam. The FLC device is regarded as a birefringent device with retardation π, namely a half wave plate. The FLC device forms four-quadrant structure and is placed between the polarizer and the analyzer. By fixing the optic axes of the four-quadrant FLC suitably, it can rotate the incident linearly polarized light in parts by plus/minus 45°.