FIGS. 4A and 4B is a diagram for explaining an example of the PN code generation clock signal PNCLK generated in the PN code generation clock signal generating means 151A. As shown in FIGS. 4A, and 4B in this embodiment, the PN code generation clock signal PNCLK is generated with reference to the front edge (rising edge) of the vertical synchronous signal V (FIG. 4A)