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指纹识别系统

摘要

指纹的唯一性和不变性决定了它在身份认证中的重要地位。它是模式识别领域中使用最早，也是应用最广的生物鉴定技术。随着低价位指纹采集仪的出现和高可靠性算法的实现，自动指纹识别技术越来越深入到人们的生活和工作当中。另一方面，由于数字信号处理器(DSP)的迅猛发展，已经可以满足图像处理中的运算量要求。

本文首先介绍了指纹识别系统的发展现状，以及指纹识别技术面临的难点和发展方向，分析了三种指纹采集技术的优劣，完成了指纹芯片的选型。

接下来讨论了指纹识别的有关概念及常规算法，然后在此基础上介绍了一种利用小波变换的指纹识别新算法，该算法利用指纹的子带小波变换系数近似服从广义高斯分布这一特点，从而仅使用两个参数就可代表指纹小波子带的特征，并以此为指纹识别的特征进行匹配。该算法的优点在于:预处理算法简单、处理速度快;算法的数据存储量小(存储6个数，存储量为24字节。近似于现阶段“ID+密码”方式的数据量)，适合实际应用。

最后介绍了半导体指纹传感器MRB200的基本功能，并使用AVR mega16做为上位机实现指纹识别系统的设计。

关键词：自动指纹识别 特征提取 小波变换 AVR应用

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Fingerprint Identification System

Abstract

Fingerprint has important state in identity verification for its exclusivity and invariability. Along with the emergence of the low cost fingerprint sensor and the realization of the highly reliable algorithm, the automated fingerprint identification technique is applied more and more in our life and work. On the other hand, because of the fast development of the digital signal processor (DSP), the DSP already can satisfy the request of abounding computing in image processing.

First, this paper introduces the developing actuality, difficulties and direction on fingerprint identification technology, and analyses the advantages and disadvantages of the technology of fingerprint capturing; and at last selects the fingerprint sensor.

So then, This paper discusses the relevant concept and the traditional algorithm of fingerprint verification, then put forward a new fingerprint verification algorithm based on wavelet transformation. This algorithm is on the base of the character that the wavelet subband coefficient approximately obedient to the generalized Gaussian density. So two parameters can represent the wavelet subband and can be used to match fingerprints as fingerprint's character. The algorithm's advangtage is simplity of pre-processing algorithm, fast processing speed; small data memory needed by the algorithm (need to save 6 data, 24 byte. Be close to the capacity of `ID+password'), which suit real application.

Finally, this article introduces basic functions of the semiconductor fingerprint sensor MBF200, and uses AVR mega16 as upper machine to realize the design of fingerprint identification system.

Key words: Automated fingerprint identification, Feature extraction, Wavelet transformation, AVR application

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目录

第一章 绪论 .......................................................................................................... 1

1.1 引言 ......................................................................................................... 1 1.2 指纹识别技术的研究背景 ..................................................................... 2 1.3 指纹识别原理 ......................................................................................... 4 1.4 指纹识别技术面临的难点以及发展方向 ............................................. 5 1.5 指纹采集技术比较 ................................................................................. 7 1.6 特征提取与匹配 ..................................................................................... 9 1.7 性能评价 ................................................................................................. 9 1.8 本文所做工作及论文结构 ....................................................................11 第二章 指纹识别算法 ........................................................................................ 13

2.1 指纹识别的基本知识 ........................................................................... 13

2.1.1 总体特征 .................................................................................... 13 2.1.2 局部特征 .................................................................................... 14 2.2 指纹的特征提取与匹配算法 ............................................................... 15

2.2.1基于特征点的特征提取与匹配算法 ......................................... 16 2.2.2 基于指纹纹理特性的新算法 .................................................... 17 2.3 指纹奇异点检测算法 ........................................................................... 23

2.3.1 指纹主向图的求取 .................................................................... 24 2.3.2 指纹奇异点的提取 .................................................................... 27

第三章 指纹识别系统的硬件设计 .................................................................... 31

3.1 MRB200指纹模块简介 ......................................................................... 31

3.1.1 系统特点 ...................................................................................... 31 3.1.2 接口定义 ...................................................................................... 32 3.1.3 安装连接 ...................................................................................... 32 3.1.4 命令格式 .................................................................................... 33 3.2 ATmega16 单片机介绍 ......................................................................... 34 3.3 指纹识别系统的硬件设计 ................................................................... 35 3.4 指纹识别系统的软件设计 ................................................................... 41 第四章 总结与展望 ............................................................................................ 43

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