In a control apparatus for use in a multiple light projection type image display apparatus, the control apparatus includes a light source driver part configured to drive a plurality of light sources; and an apparatus controller configured to control the light source driver part. The second plate can slide with respect to the first plate and preferably slides along the surface of the main unit to cause the first and second key sections of the main unit to be covered and exposed by the display unit. A method for conducting measurements with an appropriate tomographic measuring system is also disclosed. The purpose of the data processing is to find out the virtual key positionfunction that the received reflection data corresponds to. The acoustic signals input by the user are automatically transformed into the predetermined data communication format and are communicated to the Internet site in this predetermined data communication format.