Spatial IF shift as a function of the angle of incidence for reflection off gold at a wavelength of 820 nm as obtained from the closed-form expression of Eq. (32) (curves) and polarization ray tracing (data points). The shift is shown for an incident beam of light that is completely unpolarized, 100% linearly polarized with various angles of linear polarization χ, and 100% right-handed (V = 1) or left-handed (V = −1) circularly polarized. The shifts for χ = 67.5° and χ = 157.5° are not shown, but are very close to the shifts for χ = 22.5° and χ = 112.5^°, respectively. The colors indicate different polarization states than in Figs. 7 and 8.