With the effective spectrum of hybrid source shown in Fig. 4, the proposed explanation estimates the location of the distinctive feature is around 0.88 mm away from the zero OPD location. With simulation and physical experiment, the location of the distinctive feature is found to be around 0.8 mm away from the zero OPD location. The estimation by the proposed explanation (which is 0.88 mm) agrees with the simulation and experiment results (which are around 0.8 mm), see Fig. 5.