IR Opto-Mechanical Design
Syntec develops many IR opto-mechanical designs during its investigation process after the camera applications are reviewed. Material selection is key, germanium (Ge), which has almost twice the index of refraction compared to ZnS (i.e. 4 to 2.2). The two-element Ge design provides a significant improvement in imaging when compared to the ZnS solution, see MTF plots. The IR opto-mechanical design contains four aspheric surfaces and no diffractive surface. The Ge dispersion is small enough that no chromatic correction is required, which also helps the fabrication costs. Diffractive surfaces are more difficult to generate than aspheres and the diffractive surface actual performance will typically have some level of spurious light that degrades the imaging. One potential use for a diffractive surface in the Ge design is to help athermalize the solution.