Method for limiting the amount of radiation impinging on a radiation sensitive detector (RSD) responsive to signals having infrared wavelengths of approximately 3 to 14 microns. Method includes: directing radiation signal through prism toward RSD; permitting radiation signal to impinge upon RSD when radiation is below predetermined threshold; and directing radiation associated with radiation signal but of different wavelengths from signals of interest on path external to prism, to initiate limiting of radiation impinging upon RSD when predetermined threshold is exceeded. Also, Total Internal Reflection device including prism having thin film coated on back surface of prism. Material making up prism and thin film are selected so that, in presence of radiation having intensity less than certain threshold, refractive index of thin film is lower than that of prism, and when radiation has intensity higher than that certain threshold, refractive index of thin film is higher than that of prism.