EMIR is a intermediate resolution near infrared (1.0 - 2.5 microns) multiobject spectrograph with image capabilities, to be mounted on the Gran Telescopio Canarias (GTC). EMIR is being built by a consortium of Spanish, French and British institutions, led by the Instituto de Astrofísica de Canarias. EMIR is being funded by GRANTECAN and the Plan Nacional de Astronomía y Astrofísica (National Plan for Astronomy and Astrophysics, Spain) as one of the first common user instruments for the GTC. The instrument shall deliver images and spectra from a large FOV (6x6 arcmin in imaging mode, and 6x4 arcmin in multislit spectroscopic mode). Due to the telescope image scale (1 arcmin = 52 mm) and the spectral resolution required (around 4000), one of the major challenges of the instrument is the optical design and the manufacture. The detailed optical design and its expected performance will be presented. In particular the main risk areas will be identified and our risk control strategy will be outlined.