指纹识别的基本原理
<p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">指纹其实是比较复杂的。与人工处理不同，许多生物识别技术公司并不直接存储指纹的图像。多年来在各个公司及其研究机构产生了许多数字化的算法（美国有关法律认为，指纹图像属于个人隐私，因此不能直接处理指纹图像）。但指纹识别算法最终都归结为在指纹图像上找到并比对指纹的特征。 <span lang=EN-US><?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">指纹的特征<span lang=EN-US><o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 宋体">我们定义了指纹的两类特征来进行指纹的验证：总体特征和局部特征。在考虑局部特征的情况下，英国学者</span><span lang=EN-US style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">E.R.Herry</span><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">认为，只要比对<span lang=EN-US>13</span>个特征点重合，就可以确认为是同一个指纹。<span lang=EN-US> <o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">总体特征<span lang=EN-US><o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体"> 总体特征是指那些用肉眼直接就可以观察到的特征，包括：<span lang=EN-US><o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 宋体; mso-bidi-font-family: Tahoma; mso-ascii-font-family: ˎ̥; mso-hansi-font-family: ˎ̥">纹形</span><span style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">：</span></p><span style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'"></span><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span lang=EN-US style="FONT-SIZE: 10pt; COLOR: black"><o:p><img src="http://host1.rdzjw.com/2007UpFile/2007-7/200772813349.gif" border=0 /></o:p></span></p><span lang=EN-US style="FONT-SIZE: 10pt; COLOR: black"><o:p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">其他的指纹图案都基于这三种基本图案。仅仅依靠纹形来分辨指纹是远远不够的，这只是一个粗略的分类，通过更详细的分类使得在大数据库中搜寻指纹更为方便快捷。<span lang=EN-US> <o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><b style="mso-bidi-font-weight: normal"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">模式区（<span lang=EN-US>Pattern Area</span>）<span lang=EN-US><o:p></o:p></span></span></b></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><img src="http://host1.rdzjw.com/2007UpFile/2007-7/2007728133433.gif" border=0 /> </p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">模式区是指指纹上包括了总体特征的区域，即从模式区就能够分辨出指纹是属于那一种类型的。有的指纹识别算法只使用模式区的数据。<span lang=EN-US> SecureTouch</span>的指纹识别算法使用了所取得的完整指纹而不仅仅是模式区进行分析和识别。<span lang=EN-US><o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><b style="mso-bidi-font-weight: normal"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">核心点（<span lang=EN-US>Core Point</span>）<span lang=EN-US><o:p></o:p></span></span></b></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><img src="http://host1.rdzjw.com/2007UpFile/2007-7/200772813359.gif" border=0 /></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">核心点位于指纹纹路的渐进中心，它在读取指纹和比对指纹时作为参考点。许多算法是基于核心点的，既只能处理和识别具有核心点的指纹。核心点对于<span lang=EN-US>SecureTouch</span>的指纹识别算法很重要，但没有核心点的指纹它仍然能够处理。<span lang=EN-US><o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><b style="mso-bidi-font-weight: normal"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">三角点（<span lang=EN-US>Delta</span>）<span lang=EN-US><o:p></o:p></span></span></b></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><img src="http://host1.rdzjw.com/2007UpFile/2007-7/2007728133539.gif" border=0 /></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">三角点位于从核心点开始的第一个分叉点或者断点、或者两条纹路会聚处、孤立点、折转处，或者指向这些奇异点。三角点提供了指纹纹路的计数跟踪的开始之处。<span lang=EN-US><o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><b style="mso-bidi-font-weight: normal"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">纹数（<span lang=EN-US>Ridge Count</span>）<span lang=EN-US><o:p></o:p></span></span></b></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><img src="http://host1.rdzjw.com/2007UpFile/2007-7/200772813368.gif" border=0 /></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">指模式区内指纹纹路的数量。在计算指纹的纹数时，一般先在连接核心点和三角点，这条连线与指纹纹路相交的数量即可认为是指纹的纹数。<span lang=EN-US><o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><b style="mso-bidi-font-weight: normal"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">局部特征<span lang=EN-US><o:p></o:p></span></span></b></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span lang=EN-US style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体"></span><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">局部特征是指指纹上的节点的特征，这些具有某种特征的节点称为特征点。两枚指纹经常会具有相同的总体特征，但它们的局部特征<span lang=EN-US>--</span>特征点，却不可能完全相同。<span lang=EN-US> <o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span lang=EN-US style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体"></span><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">指纹纹路并不是连续的、平滑笔直的，而是经常出现中断、分叉或打折。这些断点、分叉点和转折点就称为<span lang=EN-US>“</span>特征点<span lang=EN-US>”</span>。就是这些特征点提供了指纹唯一性的确认信息。指纹上的节点有四种不同特性：<span lang=EN-US> <o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">特征点的分类<span lang=EN-US><o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span lang=EN-US style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体"></span><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">有以下几种类型，最典型的是终结点和分叉点：<span lang=EN-US><o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><img src="http://host1.rdzjw.com/2007UpFile/2007-7/2007728133837.gif" border=0 /> <span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">终结点（<span lang=EN-US>Ending</span>）<span lang=EN-US> -- </span>一条纹路在此终结。</span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><img src="http://host1.rdzjw.com/2007UpFile/2007-7/2007728134046.gif" border=0 /> <span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">分叉点（<span lang=EN-US>Bifurcation</span>）<span lang=EN-US> -- </span>一条纹路在此分开成为两条或更多的纹路。</span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><img src="http://host1.rdzjw.com/2007UpFile/2007-7/2007728134114.gif" border=0 /> <span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">分歧点（<span lang=EN-US>Ridge Divergence</span>）<span lang=EN-US> -- </span>两条平行的纹路在此分开。</span></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><img src="http://host1.rdzjw.com/2007UpFile/2007-7/2007728134152.gif" border=0 /> <span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">孤立点（<span lang=EN-US>Dot or Island</span>）<span lang=EN-US> -- </span>一条特别短的纹路，以至于成为一点。</span></span></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体"><span lang=EN-US><o:p><img src="http://host1.rdzjw.com/2007UpFile/2007-7/2007728134223.gif" border=0 /> <span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">环点（<span lang=EN-US>Enclosure</span>）<span lang=EN-US> -- </span>一条纹路分开成为两条之后，立即有合并成为一条，这样形成的一个小环称为环点。</span></o:p></span></span></span></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体"><span lang=EN-US><o:p><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><img src="http://host1.rdzjw.com/2007UpFile/2007-7/2007728134255.gif" border=0 /> <span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">短纹（<span lang=EN-US>Short Ridge</span>）<span lang=EN-US> -- </span>一端较短但不至于成为一点的纹路。</span></span></o:p></span></span></span></span></span></p><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><span style="FONT-SIZE: 10.5pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体"><span lang=EN-US><o:p><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-bidi-font-family: 'Times New Roman'; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体"></span> </p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">方向（<span lang=EN-US>Orientation</span>）<span lang=EN-US><o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span lang=EN-US style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">-- </span><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">节点可以朝着一定的方向。<span lang=EN-US> <o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">曲率（<span lang=EN-US>Curvature</span>）<span lang=EN-US><o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span lang=EN-US style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">-- </span><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">描述纹路方向改变的速度。<span lang=EN-US> <o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">位置（<span lang=EN-US>Position</span>）<span lang=EN-US><o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><span lang=EN-US style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">-- </span><span style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体">节点的位置通过（<span lang=EN-US>x, y</span>）坐标来描述，可以是绝对的，也可以是相对于三角点或特征点的。<span lang=EN-US><o:p></o:p></span></span></p><p class=MsoNormal style="MARGIN: 0cm 0cm 0pt"></span></span></o:p></span></span> </p></span></span></span></o:p></span> 太复杂了,真专业.
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