The invention provides a viewing angle control element capable of realizing high information concealment without damaging brightness of transmitted light and dynamically changing a viewing angle in accordance with need or no need of information concealment. Afterwhich, a logical AND step is performed on the set of retrieved bit vectors; and a determination is made as to whether the resultant bit vector is comprised of all zeros or not. The source video images are up-scaled to match the display resolution of the display device.