A thermal imager is used to measure the temperature of a target surface (ε = 1) in the test section of a wind tunnel. The thermal imager must view the target though a window. The temperature of the target varies between 300 and 700 K. We want to be able to determine the target temperature but we know we must correct the camera measurements for the effects of window reflection (ρ = 0.05 - 0.3) of the surrounding room, window transmission, and window emission (i.e. if the target is cold and the window is hot the camera will sense a false high temperature for the target).

The camera has a perfect flat response curve between 3 and 4.5 µm but outside this range it sees nothing. The camera sees the surface through a window made of a material that has a transmissivity of 0.6 - 0.95 in the spectral range of 3-4.5 µm. The window temperature varies between 400 and 800 K. The surroundings are at 300 K. Determine the correction curves that convert the camera indicated target temperature to the true target temperature for the above range of parameters.