The DDL optics was designed and procured by the Max-Plank Institute for Astronony of Heidelberg.
The DDL optical concept is a cat’s eye retro-reflector with three mirrors, five reflections. Since the DDL is operated in vacuum, the windows are part of the optical design. In order to re-image the input pupils, which are at different positions for the four DDLs, the magnification is defined by a corresponding radius of the M3 mirror, which therefore varies but all other optical parameter are identical for all DDLs.
