To provide the signal generator which generates a solid (three- dimensional surface) including an array of tiles having random amplitudes.

A horizontal and a vertical dimension are defined by an H-size generator 10 and a V-size generator 12 which define the borders of titles. Those generators include a pseudo-random number generator which randomizes the dimensions. They control another pseudo-random number generator 14 which defines random amplitudes of titles. The titles can be flickered at an adjustable rate defined by making a comparison 20 between a control signal of a flicker rate FR and a pseudo-random number generated by another pseudo-random number generator 18.