Application scope of three-element compound achromatic λ/4 wave-plate

In order to find the achromatic scope of three-element compound λ/4 wave-plate,mathematical analysis was performanced and experiments at the center wavelength of 600nm was executed.In the experiment the spectrum range was between 540nm~680nm when the deviation is less than 2%.It is concluded that the achromatic scope is only near the center wavelength,which is very important for practiceal prism selection.