Precision glass molding has a well-documented effect of a decrease in the index of refraction of the glass during the molding process. This index drop has such significant value that optical designs for molded lenses must take into account the index drop to accurately determine the optical performance of the final lens. Widespread adoption of chalcogenide glasses for molded infrared optics has raised a series of questions as to the behavior of these glasses under molding conditions. This paper will investigate the index of refraction changes in two different chalcogenide glasses and determine if these changes are significant enough for optical designers to consider in their designs.
The growing demand for thermal imaging sensors and cameras has focused attention on the need for larger volumes of lower cost optics in this infrared region. A major component of the cost of thermal imaging lenses is the germanium content. As 40 Se 60 was developed as a moldable, germanium-free chalcogenide glass that can serve as a low cost alternative to germanium and other infrared materials. This material also has promising characteristics for improved optical performance, especially with regard to reduced thermal sensitivity. As 40 Se 60 has found acceptance as a material to be diamond turned or polished, but it is only now emerging as a legitimate candidate for precision glass molding. This paper will review chalcogenide molding and characterize As 40 Se 60 for widespread use in highvolume thermal imaging optics. The relative advantages and disadvantages of As 40 Se 60 as compared to other chalcogenide glasses will also be discussed.
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