The galvanometer parts of the photoelectric analog galvanometer and the grating digital galvanometer are similar, the biggest analog and digital systems use different encoders. The photoelectric analog galvanometer uses the photoelectric encoder. When the galvanometer drives the baffle to rotate, the area covered by the baffle will change, and the photocurrent generated will also change. Thus, the corresponding relation between the photocurrent and the galvanometer deflection Angle is formed. A grating digital galvanometer uses a grating encoder. When the galvanometer drives the grating size to rotate, Sin/Cos signals will be generated on the reading head. The phase of Sin/Cos signals corresponds to the deflection Angle of the galvanometer