An optical state modulation unit is provided to apply an optical intensity modulation in temporal domain on a display image generated from an inputted image signal for different gray scale values such that the optical intensity modulation performed at least one of the gray scale values of the display image falls into a region at which the flicker is perceptible to human vision when a recorded image obtained by image-capturing the display image is viewed, while remaining imperceptible when the display image is directly viewed. The optical state modulation unit provides the optical intensity modulation such that the average optical intensity of the display image based on the image signal with the optical intensity modulation is the same as that of the display image generated from the image signal without the optical intensity modulation at each gray scale value.