证明了在连续蒸镀两层高、低折射率介质膜过程中，当第一层厚度不足／４厚时，刚开始蒸镀第二层膜时其反射率变化趋势与第一层膜相同。并由此展开，说明两层厚度不足／４的薄膜在很大程度上等价于一层／４厚的薄膜。 The results show that when the thickness of the first layer is less than 4 mm thick, the change of reflectivity of the second layer is just the same as that of the first layer during the successive deposition of two layers of high and low refractive index dielectric films. And thus unfolded, indicating that a film thickness of less than 4 per two layers is largely equivalent to a film of a 4-by-4 thickness.