The present invention relates to an optical device including a display panel configured to display an image and a phase retardation plate disposed on the display panel. An optical modulation device is disposed on the phase retardation plate. The optical modulation device includes a first substrate and a second substrate facing the first substrate. The first and second substrates include a plurality of unit regions. A liquid crystal layer is disposed between the first substrate and the second substrate. The liquid crystal layer includes a plurality of liquid crystal molecules. The first substrate includes a plurality of lower electrodes including a first electrode and a second electrode. and the first substrate includes a first aligner. The second substrate includes an upper electrode and a second aligner. An alignment direction of the first aligner and an alignment direction of the second aligner are substantially parallel to each other.