<title>Characteristics of contrast and application for small-target detection</title>

Abstract

The detection of small targets, especially of a target within a single frame of data, is an important problem in image processing. A lot of work have already been proposed for this problem. Of them, nonlinear morphology-based methods have shown their advantages than traditional linear methods in target detection. Many of these methods are based on local background estimate and threshold computation. A thresholding procedure is required for the methods. However, none of them shows how to get an appropriate threshold and what is the relation between a threshold and the detection performance of the detector. In this paper, we use the contrast between target and local background to be the measurement of characteristic of targets and background. Here, the contrast between target and local background is the ratio of target residual, which is acquired by subtracting local background estimate from the original image, and local background estimate. By analyzing the difference between the contrast between target and local contrast between background and local background, we can determine an appropriate threshold which can achieve high probability of detection while produce very small probability of false alarm. Experiments on a large read sea- surface ship images prove the effectiveness of the method presented in this paper.