Q6Digital Image Processing
Question
What are the different types of noise found in images?
Answer
Image noise is classified by its statistical distribution and physical source, including Gaussian, salt-and-pepper, Rayleigh, and speckle noise.
Gaussian noise, caused by electronic circuit noise and sensor thermal effects, follows a normal probability distribution and affects every pixel with varying amplitude. Salt-and-pepper (impulse) noise appears as randomly scattered white and black pixels caused by faulty sensor elements or transmission errors, and is best removed with a median filter rather than averaging. Rayleigh and Erlang (gamma) noise arise in range imaging and low-light photon-limited sensing. Speckle noise, a multiplicative noise seen in coherent imaging systems like ultrasound and SAR (synthetic aperture radar), arises from random interference of coherent wavefronts. Poisson (shot) noise results from the discrete, quantum nature of photon arrival at low light levels.