A drive controller for electrode group A obtains a disc type, a current layer, and a temperature of the liquid crystal element, and based on contents of the information, it obtains drive voltage values to be applied to the electrodes of the group of electrodes A from the set value table. When the drive voltages to be applied to the group of electrodes A are determined, the drive controller for electrode group A finishes the process, and the process flow goes to a process performed by the drive controller for electrode group B. The drive controller for electrode group B performs initialization of segment numbers. Then, it determines how a phase correction quantity of an electrode Am has changed along with an increase of a radius of the liquid crystal element by using graphs and data, so as to determine the drive voltages to be applied to the group of electrodes B by different calculating methods for different areas in which the electrode Am is disposed.