PURPOSE: To display an optical image in PPI display by storing once an optical signal with a narrow width obtained through the utilization of a vertical scanning line over wide directions and reading and displaying it in high speed.

CONSTITUTION: A radar signal received by an antenna 1 is led to a radar memory 13 via an amplification detection circuit 11 and an A/D converting circuit 12. The memory 13 has address areas of 1∼N in the direction of the distance (r) and of prescribed number in the azimuth θ and the address is designated by using calculation values θ, r from the azimuth counter 6 and a distance counter 10 via a switch 14 and the result is inserted to a memory 13. The optical signal with a narrow width obtained by one scanning is led to a camera memory 17 via an A/D coversion circuit 16, the memory 17 has the same capacity as the memory 13 in the azimuth direction and a capacity of 1∼M/2-N in the scanning direction and the address designation is inserted to the memory 17 by the count value from a scanning counter 18 and the counter 6 via a switch 19.