The colorful lines on the back of disc are well known, but the physics behind them are rarely explored. Starting from the special phenomena observed in daily life, in this paper experiments are designed to systematically study the characteristics of color lines and stripes behind disc and to find out the fringe bending phenomenon that is different from the traditional empirical law. Creatively, the theory of OPDfield is proposed to explain it in combination with the unique structural characteristics of disc. Then it is verified quantitatively by Matlab simulation and experiment. Finally, the concept of traditional grating is enriched from the symmetry point of view and the physical connotation behind the empirical law of grating diffraction is revealed, which provides a new way to study the spectral effect of grating diffraction and enriches the teaching content．