利用偏微分方程原理，建立二阶、四阶及TV模型对指静脉图像进行去噪处理，提升图像清晰度，以便于后续特征提取及识别。(Based on the principle of partial differential equation, the second-order, fourth-order and TV models are established to denoise the digital vein image, so as to improve the image clarity and f