In a scan system, a lighting unit, a display, and a three-dimensional display that have all of high luminance, low power consumption, and high reliability of a circuit board are provided. A light modulation device bonded to a light guide plate is provided with a light modulation layer exhibiting scattering property or transparency to light propagating through the light guide plate. The light modulation layer is interposed between a lower electrode that is configured of a plurality of partial electrodes extending in a direction parallel to a light incident surface and a sheet-like upper electrode. A drive circuit sequentially drives the plurality of partial electrodes to scan a region exhibiting the scattering property of the light modulation layer in a direction orthogonal to the light incident surface.