Imaging the planets that orbit around other stars requires blocking the host star which is usually 8 to 10 orders of magnitude brighter than the planets. This is achieved with the help of a stellar coronagraph. In the current work, a concept of a new type of stellar coronagraph is introduced where the star light is blocked by a linear polarizer in the collimated beam. It is based on differential rotation between the linear polarization state of planet light and that of star light. This is achieved with the help of a set of thick birefringent crystals in the collimated beam of a telescope where the planet light is made to travel extra optical path length compared to star light. By adjusting the orientation and thickness of the crystal, the optical path length can be made to cause a phase difference of π, just enough to rotate the initial plane of polarization by 90 deg for planet-light without affecting the star light. Theoretical calculations involving the phase difference due to birefringent crystals are presented along with the basic configuration and design. It is shown that the design blocks the star light identically at all wavelengths. Application of this concept for detecting Earth-like extrasolar planet is discussed using a 1-m class telescope.

中文翻译：

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消色差恒星日冕仪的概念及其在探测系外行星中的应用

对围绕其他恒星运行的行星进行成像需要遮挡通常比行星亮 8 到 10 个数量级的主恒星。这是在恒星日冕仪的帮助下实现的。在目前的工作中，引入了一种新型恒星日冕仪的概念，其中星光被准直光束中的线性偏振器阻挡。它基于行星光的线性偏振态与星光的线性偏振态之间的差动旋转。这是在望远镜准直光束中一组厚双折射晶体的帮助下实现的，与星光相比，行星光在其中传播了额外的光程长度。通过调整晶体的取向和厚度，可以使光路长度产生π的相位差，刚好足以将行星光的初始偏振平面旋转 90 度，而不会影响星光。涉及由于双折射晶体引起的相位差的理论计算与基本配置和设计一起呈现。结果表明，该设计在所有波长下均相同地阻挡了星光。使用 1 米级望远镜讨论了这一概念在探测类地系外行星方面的应用。