为了研究Lyot改进型退偏器对单色光的退偏性能，采用多光束叠加的方法，得到该退偏器的退偏度关于入射线偏振光振动方位角和总延迟量的表达式。分析表明，在退偏器的楔角达到一定值的前提下，总延迟量δ=（N+ 1/2）π（N为整数）时，所有方位角入射的线偏振光都有理想的退偏效果；δ=Nπ时，方位角对退偏度的影响最大；δ为其他值时，方位角对退偏度的影响介于以上二者之间。采用405 nm的激光光源，经过扩束准直，对楔角为6°的石英晶体Lyot改进型退偏器的退偏度进行了实验测试，结果验证了理论分析；通过调节入射角使总延迟量δ接近（N+ 1/2）π，此时退偏度超过98.8%。

In order to study the depolarization performance for monochromatic light of improved Lyot depolarizer, the method of superposition of multiple beam is proposed. The formula for depolarization degree D that is the function of vibration azimuth angle (VAA) and total retardation is deduced. It is shown by theoretical analysis that D is ideal for any VAA when retardation δ=（N+ 1/2）π (N is integer) on the basis of large enough wedge angle. And when δ=Nπ, VAA makes greatest impact on D. When δ is assigned to the other values, the impact on D made by VAA is between the former two. Using 405 nm diode laser whose beam is expanded and collimated, experiments to measure D of sample whose wedge angle is 6° are conducted. The theoretical results are well verified by experiments. D is over 98.8% when total retardation δ is nearly (N+ 1/2)π by changing incident angle.