本文利用光栅衍射研究了光盘的等效光栅结构，通过对比反射衍射与透射衍射的测量结果，详细分析了使用不同波长激光器的测量误差，从而探明了光盘的微观结构，并且分析了切向光斑未出现的原因.在此基础上，利用透射衍射实验，并使用极坐标算法精确测得光盘的存储容量，最终测得CD和DVD的存储容量与其标准值的最小误差分别为0.0014%和0.38%.

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.