Correction Algorithm For Fiber Images With Non-uniform Illumination

In the fiber image analysis and automatic recognition system, close imaging technology is required. But acquisition system uses spot lightening, that causes non-uniform illumination. The direction of lightening is upright in the center, but direction bias occurs in the other parts. When the image is contaminated by such interference, the image contrast and the gray level changes. That will affect the performance of the following algorithm in fiber recognition.It is expected that the non-uniform illumination should be alleviated and the useful information be preserved in the non-uniform illumination correction algorithm. Both in the spatial domain and frequent domain, the portion of non-uniform illumination and useful information overlap. Therefore, it is important to identify the useful information from the background interference in proposed algorithm.In the paper, several non-uniform illumination correction algorithms are studied. These algorithms can be classified to two types, i.e., spatial domain and frequent domain. In the spatial domain, the calculation is performed to each pixel. While in frequency domain algorithm, signal can be transformed form spatial domain to frequent domain and the further processing is implemented in the frequency domain. Both of them have their own shortcomings. In order to obtain satisfactory result, much calculation is required in spatial domain. While in frequent domain, filters cause rings on the results. Moreover, there is no objective standard to classify the performance of such algorithms.In this paper, a new non-uniform illumination correction algorithm based on linear iteration is proposed to deal with such shortcomings. First, the signal's deviation from the mean formula is calculated with iteration and characteristic point sets are calculated. For such characteristic points, the average value is used instead to minimize the influence near the edge points in the image. The experimental results show that the proposed algorithm is fast and the useful information is well preserved. The influence of non-uniform illumination is also well controlled.