The invention provides: a code generation and data assignment circuit that sets the order in which a confidential image and a reversed image are displayed, based on an orthogonal code; and a shutter glass control signal generation circuit that controls so that during a period when an image signal of an image including at least part or all of the confidential image is outputted, the shutter glasses disposed between the succeeding display apparatus and the user's eyes are set in a light transmission state and during a period when another image is displayed, the shutter glasses are set in a light shielding state. The image signal of the confidential image and the image signal of the reversed image are in a relationship such that when the brightness values of the images are added together for each pixel, the resultant image has no correlation with the first output image.