• M-transform;
  • photon shot noise;
  • noise reduction;
  • image sensor


We propose a novel approach for the reduction of photon shot noise in image sensors, inspired by the M-transform method. In the proposed method, the photon shot noise is transferred to small-amplitude random signals. Then the small-amplitude random signals are removed by an ϵ filter. The Sobel method was used for edge detection, and edges were preserved by not applying the ϵ filter on the edge. After noise reduction, the signals are restored to the image by a reverse M-transform. We compared our method with the smoothing filter, the median filter, and the Wiener filter. In photon shot noise based on the Poisson distribution, we changed the number of incident photons and created the noise image by using a simulation. In cases where the maximum number of incident photons was 128 (illumination of about 2 lux), the proposed technique was subjectively confirmed as better than the smoothing filter, based on the effect of edge preservation even in a dark environment. As a result, the proposed method is confirmed to be effective for reducing photon shot noise. © 2011 Wiley Periodicals, Inc. Electron Comm Jpn, 95(1): 55–62, 2012; Published online in Wiley Online Library ( DOI 10.1002/ecj.10344