Research on SNR of Point Target Image

There are many kinds of definition of SNR(Signal-Noise-Ratio)in image processing. We classified the definitions of SNR and summarized the correlation,calculation and applying range of them. Since the common methods for calculating the SNR have large errors,we proposed a parameter estimating method based on least-squares fitting. Firstly,estimation was made on mean and variance according to the total gray level of histogram. Then the non-background pixels that have high gray level were excluded by iteration,and thus the statistical range was reduced step by step. At last,the statistical parameters that have least square error were chosen as the estimation of background gray level and noise variance. Emulation experiment proved that: compared with the usual"local leaset variance method"and "below mean variance method",SNR calculated by the background noise parameters got from this method is more accurate and stable.