Transmission-type screen, projection-type display device, and image displaying method

An image displaying method for displaying an image by radiating image light from a light emitter onto a transmission-type screen from a rear-surface side thereof, which is an opposite side to an image display side, the image displaying method comprising:

• a first step of inflecting the image light from the light emitter toward the display side using a Fresnel optical element formed on a rear-surface side, which is a light-entering-surface side of the image light;
• a second step of diffusing the image light from the Fresnel optical element using a first light diffusing unit that is provided on the display side with respect to the Fresnel optical element;
• and
• a third step of diffusing the image light from the first light diffusing unit using a second light diffusing unit and causing the diffused image light to exit toward the display side, while changing a relative position between the second light diffusing unit and the first light diffusing unit, the relative position being changed such that a moving light diffusing unit of the first light diffusing unit and the second light diffusing unit is moved in a circular path with respect to a stationary light diffusing unit of the first light diffusing unit and the second light diffusing unit, the circular path being parallel to a plane of a surface of the moving light diffusing unit, and a degree of haze of the moving light diffusing unit is less than a degree of haze of the stationary light diffusing unit, the second light diffusing unit being held by a substrate, being provided on a rear-surface side with respect to the substrate, and being provided on the display side with respect to the first light diffusing unit.