To provide an intrusion detector, capable of surely detecting an intruder without being affected by a disturbance noise and giving an alarm that causes the light receiving surface of a sensor to be covered.
Infrared image sensors 2 to 4 detect a thermal image in a prescribed area inside a cabin. A microcomputer 12 detects the intrusion of a person by obtaining a temperature change point, based on thermal image data according to detection signals from the infrared image sensors 2 to 4. When the temperature change point appears, the microcomputer 12 increments a movement counter; and when the temperature change point disappears, the microcomputer resets the movement counter. When the movement counter becomes N or larger, an alarm is emitted. A temperature dispersion value is obtained based ion the thermal image data, and when the temperature dispersion value is a prescribed value or smaller, the detector judges that the front face of the infrared image sensors 2 to 4 are closed, and emits the alarm.
ASAKURA FUMIO
SHIMOMURA TOSHIO
NIPPON SOKEN