A vehicle seat includes a seat cushion, a seatback, an upholstery member that covers a surface of the seatback, and a striker. With this, when a registration operation is carried out with respect to a user authentication system, it is possible to prevent the fraud registration by the operator. In an updating procedure, first the relevant search tables are found and then reconverted to the associated prefix tables from which they were derived. The silica glass article may be further processed to form a complete optical fiber preform. The data conversion process is controlled by a control unit such that a pre-charge phase and an evaluation phase are performed alternately. Irradiation by the irradiation unit and movement of the original stage in the scan direction are carried out substantially in parallel with each other so as to remove a contaminant on the original.