An illumination unit of an embodiment of the present technology includes: an illumination optical system configured to generate illumination light; and a plurality of lenses configured to reduce a divergence angle of the illumination light. The illumination optical system includes: a light source (20) configured to apply light onto an end surface of one of a first substrate and a second substrate; and a light modulation layer (30) provided in a gap between the first substrate and the second substrate. The illumination optical system includes an electrode configured to generate an electric filed that generates, in the light modulation layer (30), a plurality of linear scattering regions (30B) in a three-dimensional mode, and to generate an electric field that generates, in the light modulation layer, a planar scattering region in a two-dimensional display mode. The lenses are arranged side by side in a direction in which the linear scattering regions extend, and are also arranged side by side in a direction intersecting with the direction in which the linear scattering regions extend.