We have measured the pseudo-dielectric functions of pseudomorphic Si1-xGex (0 less than or equal to x less than or equal to 0.45) alloys grown on Si substrates using spectroscopic ellipsometry. The E-1, E-1 + Delta(1), and E-0' gaps were determined by performing lineshape analysis on the second derivative spectra of the pseudo-dielectric functions. The change of these higher gaps were studied as a function of the Ge composition. Compared to the E-1 gap of relaxed SiGe/Si reported in literature, our data show that the E-1 gap decreases slightly with increasing strain, although classical elasticity theory predicts a small increase of the E-1 gap based on the deformation potentials of silicon and germanium available from the literature.