To surely prevent saturation or trouble of an infrared detection element, while protecting an ND (Neutral Density) filter, even when receiving strong interference laser.

This device includes the infrared detection element 3 for acquiring an infrared detection signal corresponding to an infrared ray entering through an imaging lens 2; a filter driving control part 9 for driving and arranging the ND filter 5 on a dimming position on a light receiving axis of the infrared detection element 3 in order to dim the infrared ray, when the infrared detection signal exceeds a saturation level threshold; a temperature sensor 13 for detecting the temperature of the ND filter 5; and a shutter driving control part 12 for detecting a present temperature of the ND filter 5 arranged on the dimming position on the light receiving axis, and driving and arranging the shutter 6 on the dimming position in order to dim the infrared ray to the ND filter 5 and the infrared detection element 3, when the present temperature of the ND filter 5 exceeds a heat-resistant temperature threshold.