Infrared imaging device

An infrared imaging device comprising:

• an imaging element that receives infrared light emitted from an imaging target region including a subject and a background and outputs an electric signal according to intensity of the infrared light;
• an ADC that converts the electric signal into a digital signal;
• a frame memory that stores the digital signal as a thermal image;
• a background information memory that stores background information calculated based on the thermal image;
• a state determination circuitry that determines whether a subtraction value obtained by subtracting the background information from the thermal image is greater than thA that is a positive threshold for each pixel;
• a background information update circuitry that updates and stores in the background information memory as new background information, a value obtained by calculating a function f(a, T, B) in which a ratio of T between the T and B increases in association with increase of a while setting a value of the thermal image as the T, setting a value of the background information as the B, and using a number a, for each pixel;
• and
• a thermal image generation circuitry that subtracts the background information from the thermal image for each pixel and outputs the result as a corrected thermal image,
• wherein the state determination circuitry sets a value of the a in a case where it is determined that the subtraction value is greater than the thA as a1, and sets the value of the a in a case where it is determined that the subtraction value is not greater than the thA as a2, and the a1 and the a2 satisfy an expression a1<a2.