Projection device and projection-type video display device

An illumination device comprising:

• an optical element comprising a hologram recording medium capable of diffusing a coherent light beam, the hologram recording medium comprising a plurality of hologram recording medium regions, each hologram recording medium region diffusing a coherent light beam to an illuminated region corresponding to the hologram recording medium region;
• and
• an irradiation device including a light source configured to generate the coherent light beam and a scan device configured to distribute the coherent light beam from the light source to the plurality of hologram recording medium regions included in the hologram recording medium, the irradiation device being configured to irradiate the plurality of hologram recording medium regions with the coherent light beam distributed from the light source to the plurality of hologram recording medium regions so as to allow the coherent light beam to scan the plurality of hologram recording medium regions,
• wherein each hologram recording medium region comprises a plurality of positions in such hologram recording medium region, and for each hologram recording medium region, each coherent light beam incident to a position in such hologram recording medium region is diffused to an entirety of the respective illuminated region corresponding to the hologram recording medium region in order to illuminate the entirety of the illuminated region.