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公开(公告)号：US5926555A
公开(公告)日：1999-07-20
申请号：US834547
申请日：1997-04-03
CPC分类号： G06K9/0008 , G06K9/00067 , G07C9/00158
摘要： A fingerprint identification system from a gray scale image of the fingerprint includes the steps of converting fingerprint image into a digitized gray scale image, enhancing gray scale to provide uniform contrast over entire fingerprint image, down-sampling the contrast enhanced image to limit the number of pixels analyzed, generating a gradient map of the fingerprint image, defining a calculation kernel over which ridge angle determination is made by reference to gradient map, causing the calculation kernel to traverse over gradient map in a predetermined increment over pixels comprising the fingerprint image, smoothing the ridge angle map using the process of Fourier filtering, and smoothing the image quality map using the process of erosion and dilation. The ridge angle map and image quality maps are recorded. The frequency of ridges of a fingerprint image is determined by establishing at each selected pixel a line perpendicular to ridge flow, establishing a plurality of lines parallel to perpendicular line placed on both sides of perpendicular line of selected pixel, sampling a predetermined number of pixels along the perpendicular lines, averaging sample of each line, determining frequency of ridges by calculating power spectrum from a Fourier transform.
摘要翻译： 来自指纹灰度图像的指纹识别系统包括将指纹图像转换为数字化灰度图像的步骤，增强灰度级以提供整个指纹图像的均匀对比度，对比度增强图像的下采样以限制 像素分析，生成指纹图像的梯度图，定义计算核，通过参考梯度图确定脊角，使计算核以规定的增量遍历超过了包含指纹图像的像素的梯度图，平滑化 使用傅里叶滤波处理的脊角图，并使用侵蚀和扩张过程平滑图像质量图。 记录脊角图和图像质量图。 通过在每个选定的像素处建立垂直于脊流的线来确定指纹图像的脊的频率，建立与放置在所选像素的垂直线的两侧上的垂直线平行的多条线，对预定数量的像素进行采样 垂直线，每条线的平均采样，通过从傅里叶变换计算功率谱确定脊的频率。
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公开(公告)号：US5659626A
公开(公告)日：1997-08-19
申请号：US326757
申请日：1994-10-20
CPC分类号： G06K9/0008 , G06K9/00067 , G07C9/00158
摘要： A method for locating minutia in a gray scale image of a fingerprint using a pair of filters, called "Gabor" and "Minutia" filters, includes determining direction and spacing of ridges at regularly spaced pixels, aligning filters by ridge direction, determining outputs of filters where Gabor Filter has high level output when in parallel ridge flow and, due to phase discontinuity at a minutia, low level output when in neighborhood of a minutia. The Minutia filter exhibits opposite phenomenon, having low level output in parallel ridge flow and high output in neighborhood of a minutia. A method for creating a state map of a fingerprint includes determining image quality, identifying minutia locations, determining areas of good quality where minutia are present, areas of good quality where no minutia are present and areas where quality is below a predetermined value to reliably determine presence or absence of minutia. A method for determining location of, associating, and determining number of ridges between cores and deltas in digitized gray scale of a fingerprint image by Direct Estimation of Orientated Patterns includes determining ridge angle and frequency at regularly spaced pixels, computing gradients of ridge angles, ordering gradient according to size, creating vector field of image, measuring curling of vector field, locating cores and deltas, tracing path of constant value ridge angle between deltas and cores, calculating line integral of vector frequency along straight line from delta to core.
摘要翻译： 使用称为“Gabor”和“Minutia”滤波器的一对滤波器在指纹的灰度图像中定位细节的方法包括确定规则间隔的像素处的脊的方向和间隔，通过脊方向对准滤波器，确定 滤波器，其中Gabor滤波器在平行脊流时具有高电平输出，并且由于在细节处的相位不连续性，在细节附近时的低电平输出。 Minutia滤波器具有相反的现象，平行的脊流具有低水平的输出以及在细节附近的高输出。 用于创建指纹的状态图的方法包括确定图像质量，识别细节位置，确定存在细节的良好质量的区域，没有细节存在的质量好的区域和质量低于预定值的区域以可靠地确定 存在或不存在细节。 用于通过定向模式的直接估计来确定指纹图像的数字化灰度级中的核心和三角形之间的脊数的位置，关联和确定数量的方法包括以规则间隔的像素确定脊角和频率，计算脊角的梯度，排列 根据大小梯度，创建矢量场图像，测量矢量场的卷曲，定位磁芯和三角形，三角形和磁芯之间的恒定值脊角的跟踪路径，计算从三角形到核心的直线向量频率的线积分。
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公开(公告)号：US5799098A
公开(公告)日：1998-08-25
申请号：US835053
申请日：1997-04-03
CPC分类号： G06K9/0008 , G06K9/00067 , G07C9/00158
摘要： In a method for comparing one fingerprint to another, there is recorded for each fingerprint the location and angle of minutiae along with a quality measure of each minutiae, and the core and delta location along with the local average image. An image state map defining high quality image areas with and without minutiae and areas of low image quality is also recorded. In matching fingerprints, ridge angle maps are used to align fingerprint images, then state maps are compared, followed by a comparison of minutiae locations. Fingerprints are scored according to closeness of match using a dual hypothesis technique where corresponding areas on file prints and candidate prints are provided with a positive score based when there is correspondence between good quality areas containing minutiae and good quality areas containing no minutiae, and a negative score is generated when minutiae are present in a good quality area in one fingerprint and where no minutiae are present in the corresponding good quality area in the other fingerprint.
摘要翻译： 在将一个指纹与另一个指纹进行比较的方法中，记录每个指纹的位置和角度以及每个细节的质量测量，以及核心和三角洲位置以及局部平均图像。 还记录了定义具有和不具有细节的高质量图像区域和低图像质量区域的图像状态图。 在匹配指纹中，使用脊角图对准指纹图像，然后比较状态图，然后比较细节位置。 使用双重假设技术，根据匹配的接近度对指纹进行评分，其中，当在包含细节的优质区域和不含细节的优质区域之间存在对应关系时，在文件打印和候选印刷品上的相应区域被提供有肯定的分数，而负的 当细节存在于一个指纹中的良好质量区域并且在另一个指纹中相应的优质区域中没有细节时，产生分数。
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