CODEX is a high resolution spectrograph for the ESO E-ELT. A classical spectrograph can only achieve a resolution of
about 120.000 on a 42 m telescope with extremely large echelle gratings and cameras. This paper describes in detail the
optical concept of CODEX, which uses only optical elements size similar to those in current high resolution
spectrographs. This design is based on slicers, anamorphic beams and slanted VPHG as cross dispersers. In this new
version of the CODEX design, no special expensive materials as calcium fluoride or abnormal dispersion glasses are
needed. The optical quality is excellent and compatible with 10K x 10K detectors with 10 μm pixels.