PURPOSE: To attain a small-sized, lightweight device at low power consumption and to improve the reliability by using plural infrared ray solidstate image pickup elements having different infrared ray spectral sensitivity characteristic so as to image pickup the same thermal ray image of an object thereby obtaining the temperature distribution and absolute temperature value of the object from a picture signal.

CONSTITUTION: The infrared ray solid-state image pickup elements 10, 11 and 12 have different infrared ray spectral sensitivity characteristic from each other by infrared ray band pass filters 13, 14 and 15. Then a picture signal I1 of an infrared ray image having λ1±Δλ1/2 is outputted to a signal processing circuit 16 from the infrared ray solid-state image pickup element 10, a picture signal I2 of the infrared ray image having λ2±Δλ2 is outputted to the signal processing circuit 16 from the element 11 and a picture signal I3 of the infrared ray image having λ3±Δλ3 is outputted to the signal processing circuit 16 from the element 12. The signal processing circuit 16 converts the picture signals I1, I2 and I3 outputted from the infrared ray solid-state image pickup elements 10, 11 and 12 into a picture signal I representing the temperature distribution of the object 50, a signal representing the absolute temperature T of the object 50 and a signal representing the radiation factor of the object 50 and outputs them.