When we process PolSAR data by machine learning to analyze vegetation, it is necessary to know how polarization changes by scattering. In order to clarify the physical mechanisms of scattering in PolInSAR (polarimetric interferometric synthetic aperture radar), we examine how polarization changes by PPO-BD (Pixel-by-Pixel Optimization considering Baseline Difference), which is an adaptive filter of InSAR images. By using scattering sphere we propose, we find that the features of the scattering mechanisms are enhanced after polarization is optimized by PPO-BD. It means that PPO-BD performs the phase optimization by taking into account the differences in the scattering mechanisms among pixels. We find that, when PPO-BD optimizes the phase to reduce singular points by utilizing polarimetric data, it also emphasizes the polarimetric mechanism information pixel by pixel.