Palm Vein Enhancement Algorithm

Palm vein image as a cutting-edge technology of biometric trick identification, it has the characteristics of trueprint, non-contact and unforgeability during the identification, so it becomes the research hotspot of authentication. But the problems of the noise and image error often appear in the process of the acquisition and transmission for palm vein. In order to provide the credible characteristic basis for the system of palm vein identification, it is necessary to enhance the collected images of palm vein and implement the noise reduction.Contourlet transformation as a new multi-scale analysis method, it not only has the multi-resolution and time-frequency analysis features, but also has good anisotropy and directional selectivity, and it can express the smooth curve with less coefficients, which is a true of sparse representation of two-dimensional images. This paper revolves around Contourlet transformation in the application of noise reduction and enhancement for palm vein image. The main tasks are as follows:(1) Described the basic principle of Contourlet transformation and Contourlet transformation of non-down-sampling in detail, which lay the foundation for the next study of the noise reduction and enhancement algorithms.(2) Analyze the noise of palm vein image. According to the "over kill" phenomenon of the traditional threshold denoising method, a noise reduction algorithm of palm vein image based on Contourlet transform is proposed. The shrinkage factor is used to distinct the information coefficient and noise coefficient in the approximate area. The semi-soft threshold is used to denoise in the detail weight of images. So the over-kill information phenomenon is avoided. The experimental results show that the algorithm has good effect of de-noising.(3) Analyze the quality maldistribution of the palm vein image. Because the enforcement effect of the equalization algorithm of the traditional local histogram is not obvious, an improved algorithm of it is proposed. This algorithm is applied to the Contourlet transformation of non-down-sampling and an enhancement algorithm of palm vein image is proposed. At last, the lines of the palm vein are enhanced by Gabor filter. The experimental results show that the enhancement effect of this algorithm is more obvious.