A scheme for producing computer generated holograms in which a motion vector of each object to be displayed is detected, objects are classified according to their motions, a hologram fringe pattern for each classified group of objects is calculated separately by image processing stored basic patterns, and a hologram to be displayed is produced, by synthesizing all separately calculated hologram fringe patterns. In another aspect, a gaze point of the observer is determined, and a hologram to be displayed is produced by using high resolution hologram fringe patterns for objects located at the gaze point and low resolution hologram fringe patterns for regions other than the gaze point. In another aspect, a distance between each display target object and a hologram plane is obtained, a region of calculations for interference fringes due to each display target object is limited according to the obtained distance, interference fringes due to each display target object are separatedly calculated within the limited region of calculations, and a hologram to be displayed is produced by synthesizing separately calculated interference fringes due to all display target objects.