Optical design of the VLT/MUSE instrument

MUSE (Multi Unit Spectroscopic Explorer) is a second generation VLT panoramic integral field spectrograph developed for the European Southern Observatory (ESO), operating in the visible and Near Infrared wavelength range (0.465-0.93 μm) with a 1 arcmin square FoV sampled at 0.2arcsec. It is composed of a Calibration unit, a Fore-optics and a Splitting and relay system that feeds 24 identical Integral Field Units (IFU); each one incorporates an advanced image slicer associated with a classical spectrograph. This article will present the optical design choices that have been done to optimize the costs, size and performances of the instrument as well as a detailed ghost images analysis of the whole instrument.