In Micro-Reflector optical disc systems, multi-layer index modulation distribution causes wavefront fluctuation in the
light beam passing through the layers. Generally, the Merecial's criterion 0.07λrms is widely used as a figure of merit
for the wavefront quality of a light beam for readout. However, due to the fine structure of the wavefront fluctuation by
the recorded marks, the decay of readout signal is less comparing to the general case.