Noise in thermal infrared images is more complex than noise in visible light images. Random disturbances in the external environment and random changes in physical quantities inside the imaging system may form thermal infrared image noise. The basic noise of infrared detector output includes thermal noise, composite noise, photon noise, shot noise and 1/f noise. The imaging system itself also generates noise, such as scanning noise generated by a line scan system, random noise generated by a staring system, etc. With the random interference of the external environment, it is also an important source of thermal infrared image noise.

 

Thermal infrared images themselves have random flickering grain noise and banding noise. The random flickering particle noise mainly comes from the photon fluctuation of the infrared background radiation, the noise generated by the photoelectric conversion of the infrared detector, and the additional noise during the signal readout and processing circuit. Banded noise mainly comes from the non-uniform response rate of infrared detectors, imaging defects and clutter interference. The diversity of noise sources and noise types makes the noise distribution of thermal infrared images difficult to predict, so each denoising method is only suitable for filtering out one or several kinds of noise, and it is impossible to completely filter out the noise in the image.