Complex method for speckle noise reduction in the sonar image from a small underwater target

A complex method for speckle noise reduction in the sonar image from a small underwater target is proposed. In the method, the logarithmic transformation of the image is operated, and then the transformed image is processed by the multilevel median filter, and then the processed image is reprocessed by the rough sets weighted mean filter, and then the final image is obtained by the exponential transformation of the reprocessed image. A full description of the principle and process and experimental results of the proposed method is given. The experimental results show that the proposed method is effective on speckle noise reduction and image edge preservation.