| 摘要 |
PROBLEM TO BE SOLVED: To provide an infrared crime prevention device that can suppress the saturation of a conversion voltage in a voltage conversion part that converts a conversion current of a reception part into a conversion voltage, even when excess light irradiates an infrared light receiving element as disturbance light in the reception part, in a structure in which a transmission part transmits pulsed infrared rays of a predetermined carrier frequency, the reception part having the infrared light receiving element receives the infrared rays, the voltage conversion part converts a conversion current of the infrared rays received by the reception part into a conversion voltage, a frequency component extraction means extracts the carrier frequency component from the conversion voltage, and a determination part determines that there is an intruder if the magnitude of the carrier frequency component is not larger than a specified value. SOLUTION: The voltage conversion part 3 is provided with an LC resonance circuit 4 for substantially maximizing the conversion efficiency of a carrier frequency component 30a of a conversion voltage 30 and substantially minimizing the conversion efficiency of a direct current component 30b when a conversion current of infrared rays 1 received by the reception part 2 is converted into the conversion voltage 30. COPYRIGHT: (C)2006,JPO&NCIPI
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