The true zero-order wave plate, the wavelength sensitivity of the delay amount is low, the temperature stability is high, the effective Angle of acceptance is large, and the performance is greatly compared with the other two wave plates. However, the true zero-order wave plate is often very thin, taking quartz as an example, its birefringence coefficient in the visible light part is about 0.0092. A true zero-order quartz wave plate with 550nm as the center wavelength is only 15um thick. Such a thin wave plate in the manufacture and use will encounter many difficulties. The thickness of a multistage wave plate is equal to multiple full-wave thicknesses (n×waves) plus a desired delay thickness. Multistage wave plates are relatively easy to manufacture, but the disadvantage is that they are sensitive to wavelength, temperature, and Angle of incident.