(a) CSLDV velocity output of a beam at a sinusoidal excitation frequency of 111 Hz, and the X-mirror feedback signal with a sinusoidal input signal; (b) in-phase and quadrature ODS components from the polynomial method with γ = 0 deg; and (c) in-phase and quadrature ODS components from the polynomial method with the optimal γ = 62.56 deg