1. An infrared imaging device, comprising: an optical system including an infrared lens; an infrared solid state image sensing device for detecting a light radiated from an object, focused by the optical system, the infrared solid state image sensing device having an image area where first infrared detectors for detecting infrared image signals are arranged in a two-dimensional array form; infrared detecting means being arranged on the infrared solid state image sensing device outside the image area and comprising infrared detector groups for extracting an optical system contributory component, the infrared detector groups including at least two kinds of second infrared detectors having respectively different sensitivity characteristics to obtain at least two kinds of output signals; and processing means for carrying out a calculation processing of the infrared image signals output from the first infrared detectors within the image area on the basis of basic data previously prepared as characteristics of said at least two kinds of the output signals obtained by the second infrared detectors of the infrared detecting means, so as to remove the optical system contributory component.