Manufacture of a Reflecting Slit Optical Element

The requirement for a reflecting slit optical element resulted from design of a visual/IR imaging spectrometer optical system for an earth remote sensing instrument. In this optical system, the reflecting slit is located at the focus of a Schmidt telescope and serves as a field lens, field flattener, and entrance aperture to a two band visual/IR imaging spectrometer. These multiple functions make the reflecting slit a critical element in the optical design. This and concern for the ability to manufacture such an optical element dictated that a breadboard slit be manufacturer and verified before proceeding further with the development of the optical design. The configuration of the optical system is shown in Fig. 1. Unlike the usual spectrometer arrangement, radiation at the focus of the telescope (fore-optic) is reflected, instead of transmitted, by the slit into the spectrometer.