JP2659080B

PURPOSE:To improve the detecting accuracy of an abnormality by removing automatically a noise due to the natural phenomenon and adjusting suitably the threshold. CONSTITUTION:In a monitor to perform the differential operation for each picture element 6 for each prescribed time for the infrared ray image to show the temperature distribution of an object in a sight 3 of an infrared ray camera 2, perform a threshold processing 4 and detect the abnormality by detecting the hourly temperature change of the prescribe one or above, the picture element 6 to detect the hourly temperature change is counted, and at the time of the prescribed number or above, deciding is performed as a noise, and the processing as the abnormality is not performed. When the threshold is low and the noise due to the natural phenomenon is stationarily generated, the threshold is adjusted in the high direction, and when the threshold is high and the generation of the noise is too little, the threshold is adjusted in the low direction and the unsuitable threshold is automatically corrected.