### Abstract

Reference 1 contains a serious error that renders most of the results inapplicable to grazing-incidence telescopes and creates an incorrect impression as to the polarization properties of grazing-incidence telescopes. The errors arise from an incorrect application of the sign convention for the Fresnel equations. The Fresnel equations are correct as stated in Eqs. (2) and (3) but are incorrectly assembled into the Jones matrix in Eq. (8), where the minus sign of ap should be removed. This equation is at the heart of the technical development, causing errors in many of the remaining equations. The retardance is incorrectly calculated by Eq. (5) and is plotted incorrectly in Fig. 4. Near grazing incidence, the linear retardance associated with reflection from metals, approaches zero (δ → 0) as the angle approaches grazing incidence (i → 90°). The paper incorrectly states that δ → π rad. Thus a grazing-incidence mirror acts as a nonpolarizing element, not as a half-wave linear retarder.

Original language | English (US) |
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Pages (from-to) | 4236-4237 |

Number of pages | 2 |

Journal | Applied optics |

Volume | 32 |

Issue number | 22 |

DOIs | |

State | Published - Aug 1993 |

Externally published | Yes |

### ASJC Scopus subject areas

- Atomic and Molecular Physics, and Optics
- Engineering (miscellaneous)
- Electrical and Electronic Engineering

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## Cite this

*Applied optics*,

*32*(22), 4236-4237. https://doi.org/10.1364/AO.32.004236