Patent ID: 7071812

Claim:
A detector for detecting a target object approaching inside detection areas, said detector comprising: a wave outputting device for outputting waves at a specified transmission timing; a transmission antenna for transmitting transmission waves outputted by said wave outputting device as electromagnetic waves into space; a reception antenna for receiving the electromagnetic waves transmitted from said transmission antenna and reflected from said target object; a plurality of wave detection circuit parts with delay circuits for setting different sampling timings with delays from said specified transmission timing according to distances between said detector and specified detection areas, mixing wave detection signals corresponding to said transmission waves with signals received by said reception antenna at said different sampling timings and outputting the mixed signals; and a plurality of judging circuit parts each corresponding to different one of said wave detection circuit parts and serving to switch on a detection output based on the outputted signals from said wave detection circuit parts to indicate that said target object is approaching; wherein said detection areas have different sizes for each of said judging circuit parts corresponding to said different sampling timings of said wave detection circuit parts.