  Spectroscopic ellipsometry is used to determine the dielectric function of
the superconducting LaFeAsO$_{0.9}$F$_{0.1}$ ($T_c$ = 27 K) and undoped LaFeAsO
polycrystalline samples in the wide range 0.01-6.5 eV at temperatures 10 $\leq
T \leq$ 350 K. The free charge carrier response in both samples is heavily
damped with the effective carrier density as low as 0.040$\pm$0.005 electrons
per unit cell. The spectral weight transfer in the undoped LaFeAsO associated
with opening of the pseudogap at about 0.65 eV is restricted at energies below
2 eV. The spectra of superconducting LaFeAsO$_{0.9}$F$_{0.1}$ reveal a
significant transfer of the spectral weight to a broad optical band above 4 eV
with increasing temperature. Our data may imply that the electronic states near
the Fermi surface are strongly renormalized due to electron-phonon and/or
electron-electron interactions.
