Design considerations for an unconventional infrared prism with a 90 degree ray deviation

摘要

In this study, the optical performance of a 90 degree prism working in the mid-wave infrared region with the purpose of carrying a beam of light from one optical system to another in an unconventional way is discussed. First, a group of mirrors is considered as a design alternative to lower the overall cost of the system. However, using mirrors greatly increases the diameter of the beam due to the rays coming from wide field of view angles. Another drawback of mirrors is that having separate mirrors requires precise alignment for the system to work at full performance which is difficult for the given application. However, these alignment issues are not valid for a single piece prism. Therefore, a single piece prism is the preferred option and has been taken into account in this study. Material selection is important, especially in the mid-wave infrared region where the index of refraction differs greatly from material to material. Silicon and Germanium are the materials preferred because of their high index of refraction and transmission characteristics. Aside from optical properties, these materials are also considered in terms of manufacturability. Also, options for the coatings to be applied to reflecting surfaces of the prism are discussed with regard to the transmission loss within the system. In order to have total internal reflection within a prism, coatings must be chosen carefully to handle transmission loss at the reflecting surfaces. All of the system parameters are examined using sequential and non-sequential modes of ZEMAX OpticStudio software.