This is a Dall-Kirkham optical design with coatings that are optimized to transmit in infrared or ultra violet wavelengths. It is diffraction limited across a 20mm image circle at the focal plane. There are no refractive lens, only reflective components to the design. For IR application, reflectives coatings are a protected gold which give better than 98% reflectivity from .65 micron (650nm) to 5 micron (5000nm). This design is ideal for infrared astronomy or LIDAR applications. UV optimized coatings can also be used at an additional cost.
The DK is available in the three different apertures 12.5 ", 20", 24" and 28".