Image display apparatus

An image display apparatus comprising:

• a luminescent layer;
• an excitation source which excites the luminescent layer;
• a front layer which obtains display light by transmitting light generated by the luminescent layer excited by the excitation source;
• and
• a periodic structure provided between the front layer and the luminescent layer, the periodic structure including a periodic refractive index distribution in a surface parallel to the front layer,
• wherein the periodic structure is configured to attenuate reflection of outside light incident into the front layer,
• wherein the periodic structure satisfies a relation of a following expression (1) and a periodic interval of the periodic structure is equal to or greater than 1 μm and equal to or less than 3 μm,
• wherein said expression (1) is given by,
• 1<Nsub≦Neff
• where
• Neff denotes an effective refractive index of the periodic structure, and
• Nsub denotes a refractive index of a medium constituting the front layer,
• wherein the periodic structure has a two-dimensional periodic refractive index distribution in the surface parallel to the front layer,
• wherein the periodic structure has a refractive index distribution in a triangular lattice shape, a square lattice shape, or a rectangular lattice shape, and
• wherein the periodic structure has a structure in which in a layer comprised of a first medium, cylindrical structures comprised of a second medium different from the first medium are periodically arranged and has, the structure satisfying a relation of a following expression (7),
• wherein said expression (7) is given by,
• D>0.5*w
• where
• D denotes a length of the cylindrical structure in a direction perpendicular to the front layer, and
• w denotes a diameter of the cylindrical structure in a surface parallel to the front layer.