中文摘要：

依据射影不变性提出5个描述多边形拓扑和几何特征的特征向量，以这些特征向量作为约束条件给出在射影变换下两个多边形为类似形的定义；基于类似形原理，提出了一种新的识别平面多边形的方法。用拓扑结构定性分析类似形对图象中的噪声不敏感，用几何特征进行定量分析能反应图象的细小差别。该识别算法不仅能识别不同形状的目标，而且还可以区分形状相同但大小、比例不同的目标。

英文摘要：

Troblems are researched. Firstly we propose five topology characteristics and geometry characteristics that are invariant under perspective transformation to describe polygon. Then, the definition of homograph is given in terms of these characteristics; On the basis of this definition, a new algorithm is proposed for recognizing if two polygons are homograph based on the principle of homograph. We introduced the topological structure to analyze homograph qualitatively, therefore the algorithm is insensitive to noises; and employ geometrical structure to analyze homograph quantitatively, thus the algorithms can show fine discrimination between polygons. It can not only recognize objects of different shape but also distinguish between objects that are of the same shape but their size and scale different.