▎ 摘　　要

We investigate the optical response of graphene via spectroscopic ellipsometry in the ultraviolet and visible ranges. The optical conductance of graphene is described by a Fano model. The parameters of this model are extracted from our spectroscopic ellipsometry measurements, and the complex refractive index of graphene is obtained. Graphene's dispersion relation shows that the density of states function has a logarithmic van Hove singularity corresponding to the M point of the Brillouin zone. The exciton binding energy is calculated as the difference between the resonant and the saddle point energies.