Abstract: In this paper, grating diffraction is employed to investigate the equivalent grating structure of optical discs. By contrasting the measurement outcomes of reflection diffraction and transmission diffraction, a comprehensive analysis of the measurement errors using lasers of different wavelengths is conducted. This enables the identification of the optical discs microstructure and the rationale behind the absence of tangential spots. Building on these findings, the storage capacity of CDs and DVDs is accurately determined via transmission diffraction experiments and polar coordinate algorithms. The minimum errors in the storage capacity of CDs and DVDs are 0.0014% and 0.38%, respectively.

Key words: lasers, optical disc, grating constant, storage capacity