Grating experiment is an important optical experiment in physics, which helps people to understand the interference and diffraction of light. Generally, replication grating or holographic grating is used in the experiment, and sodium lamp and mercury are used as light sources. Other instruments include spectrometers, collimators, telescopes and flat mirrors. The experimental principle is shown in figure 1. After the light source passes through a single slit, it forms a parallel beam through a collimator. Vertical illumination will spread in all directions and interfere with each other after passing through a lens (telescope), forming a series of bright stripes separated by quite wide dark areas with different intervals on the focal plane of the lens.