Image display device and image display medium

An image display device comprising a plurality of image cells arranged two-dimensionally and including a hologram layer, the hologram layer including a diffraction grating in which a one-dimensional grating pattern extending in a first direction is located repeatedly in a second direction perpendicular to the first direction, wherein

• the plurality of image cells, comprising a first image cell group, a second image cell group, and a third image cell group, each image cell group comprising image cells that are aligned in the second direction and associated with a single color, and
• each image cell group includes a section in which a spatial frequency f of the diffraction grating of the image cell group and a wavelength λ of light of the single color satisfy an equation (1):
• f =(sin α−sin β)/λ(α>β) (1)
• such that the image cells forming the image cell group display a common color when a viewpoint is located at a predetermined angle relative to the image display device, where
• an incident angle α is an incident angle of illumination light relative to the image display device, and
• a diffraction angle β is a diffraction angle of one of diffraction light beams diffracted by the diffraction grating patterns that passes through the viewpoint;
• and the first image cell group comprises image cells that are associated with a first color and the first image cell group comprises a section in which the spatial frequency f of the diffraction grating of the first image cell group and the wavelength λ of light of the first color satisfy the equation (1),
• and the second image cell group comprises image cells that are associated with a second color and the second image cell group comprises a section in which the spatial frequency f of the diffraction grating of the second image cell group and the wavelength λ of light of the second color satisfy the equation (1),
• and the third image cell group comprises image cells that are associated with a third color and the third image cell group comprises a section in which the spatial frequency f of the diffraction grating of the third image cell group and the wavelength λ of light of the third color satisfy the equation (1).