The purpose of the present invention is to make it possible to reduce the influence of liquid crystal inversion without increasing the drive frequency of a liquid crystal dimmer element. A plurality of liquid crystal layers sandwiched between two electrodes, both serving as end electrodes, drive liquid crystal dimmer elements arranged side by side in an optical axis direction of a transmitted light. In this case, a drive signal reversing at a predetermined cycle is applied to both end electrodes of each liquid crystal layer. This drive signal of multiple systems is set as a signal having phases deviated from the relationship of in phase or reverse phase, preventing the inversion timing of each liquid crystal layer from coinciding.