Analysis of DVD diffraction patterns under oblique light illumination

When an optical disc is illuminated by an incandescent lamp, a bright colored line can be observed on its surface, and the color of the bright line varies with the observer's position. Based on the optical reflection grating structure of a Digital Versatile Disc (DVD), we first establish an optical path model of a source-disc-observer system. Then, we derive an analytic equation describing the relationship between the wavelength of the bright lines and the observation angles by applying the scalar diffraction theory. Finally, an experimental investigation is conducted, confirming the reliability of the theoretical model. This study can be applied to physics experimental teaching in universities, providing a compelling teaching example for students to deeply understand the optical structures and diffraction properties of optical discs.