An optical modulation device comprising: a first plate and a second plate facing the first plate; and a liquid crystal layer between the first plate and the second plate and comprising a plurality of liquid crystal molecules, wherein the first plate comprises a plurality of first electrodes (191, 191a, 191b) and a first alignment layer, the main surface of the first plate facing the liquid crystal molecules defining an azimuthal plane which contains an x-axis; wherein the second plate comprises at least one second electrode (290, 291) and a second alignment layer, the first alignment layer and the second alignment layer being vertical alignment layers, wherein an alignment direction of the first alignment layer is substantially parallel to an alignment direction of the second alignment layer, and wherein the optical modulation device is adapted to be divided in units of the first plate, the second plate, and the liquid crystal layer sandwiched between the first and second plates (100, 200) over which the azimuthal angle of the long axis of the liquid crystal molecules changes by 180 degrees along the x axis direction, when a voltage is applied between the first and second plates (100, 200), wherein, when no electric field is applied to the liquid crystal layer, the pre-tilt direction of the liquid crystal molecules adjacent to the first plate is symmetrical to the pre-tilt direction of the liquid crystal molecules adjacent to the second plate with respect to a center line between the first and second plates and extending in parallel to the first plate; characterized in that when an electric field is applied to the liquid crystal layer, the optical modulation device is configured to increase the voltage supplied to the plurality of first electrodes (191, 191a, 191b) not abruptly, in a stepwise manner. a first plate and a second plate facing the first plate; and a liquid crystal layer between the first plate and the second plate and comprising a plurality of liquid crystal molecules, wherein the first plate comprises a plurality of first electrodes (191, 191a, 191b) and a first alignment layer, the main surface of the first plate facing the liquid crystal molecules defining an azimuthal plane which contains an x-axis; wherein the second plate comprises at least one second electrode (290, 291) and a second alignment layer, the first alignment layer and the second alignment layer being vertical alignment layers, wherein an alignment direction of the first alignment layer is substantially parallel to an alignment direction of the second alignment layer, and wherein the optical modulation device is adapted to be divided in units of the first plate, the second plate, and the liquid crystal layer sandwiched between the first and second plates (100, 200) over which the azimuthal angle of the long axis of the liquid crystal molecules changes by 180 degrees along the x axis direction, when a voltage is applied between the first and second plates (100, 200), wherein, when no electric field is applied to the liquid crystal layer, the pre-tilt direction of the liquid crystal molecules adjacent to the first plate is symmetrical to the pre-tilt direction of the liquid crystal molecules adjacent to the second plate with respect to a center line between the first and second plates and extending in parallel to the first plate; characterized in that when an electric field is applied to the liquid crystal layer, the optical modulation device is configured to increase the voltage supplied to the plurality of first electrodes (191, 191a, 191b) not abruptly, in a stepwise manner.