  Optical conductivity spectra of single crystals of Ca_1-xSr_xVO_3 have been
studied to elucidate how the electronic behavior depends on the strength of the
electron correlation without changing the nominal number of electrons per
vanadium atom. The effective mass deduced by the analysis of the Drude-like
contribution do not show critical enhancement, even though the system is close
to the Mott transition. Besides the Drude-like contribution, two anomalous
features were observed in the optical conductivity spectra of the intraband
transition within the 3d band. These features can be assigned to transitions
involving the incoherent and coherent bands near the Fermi level. The large
spectral weight redistribution in this system, however, does not involve a
large mass enhancement.
