Research On The Key Technology Of3D Fingerprint Device

As an unique, lifelong and easily acquired biometric, fingerprint recognition developmenthas been always concerned on over the years. Biomatric identification that based on thefingerprint is considerred to be the most universal identity authentication method. Withinformation technology development, fingerprint has been widely applied to ID card, accesscontrol, border control, and criminal investigation to name a few. The traditional fingerprintrecognition method is to get the2D (Two Dimensional) fingerprint image, analyze and processthem. But fingerprint is3D (Three Dimensional) biological characteristics, from three to twodimensions， it must lose one dimensional information and simultaneously there must benonlinear distortion. Therefore it is getting more and more important to obtain3D fingerprintinformation with no distortion or ghost. While with the development of computer and3Dimaging measurement techniques,3D imaging measurement techniques based on the fringeprojection has been studied in academics and utilized in many application fields because of theadvantages of universality, uniqueness, permanency and acceptability.3D imaging systems basedon fringe projection technique have been actively studied in academia and widely applied inindustry because of the advantages of non-contact, full field, high accuracy, fast acquisition andautomatic data processing.In this paper, a novel3D fingerprint device is presented by using fringe projection technique.The principle of3D fingerprint sensor is introduced to obtain the absolute phase data (3D shape).The paper presents hardware and software of the3D sensor system and their assembling. Someexperimental results on fingerprints demonstrate the feasibility of the proposed3D fingerprintdevice. The thesis mainly includes the following contents.1. Hardware structure design of the3D fingerprint device. Based on the principle ofmeasurement，how is to choose a compact projector and a CCD camera. Assembling theprojector and the CCD camera together into a mobile and portable mechanical supporter. Itreduces adjustment workloads, saves time and improves efficiency. Making the adjustment of theprojector and camera relative position rapidly and accurately, so as to realize the acqusition oftarget images fast and accurately.2. The software development of3D fingerprint device. The software system was developed inVC++environment based on the provided development program of the CCD camera. The acquisition function includes the following parts: parameter controlling of the CCD camera,parameter controlling of the DLP projector, lively displaying the captured image, and saving theimages. Realizing fringe pattern images processing, analysis and3D fingerprint data display etc.3. Using the designed checkerboard having black and white square and white plate havinghollow rings, the paper studies how to calibrate the3D fingerprint device by establishing therelationship between the phase value of each pixel point and three-dimensional space coordinates.And finally the3D fingerprint data of finger can be obtained.4. The experimental data on the index fingers surface show that the proposed3D fingerprintdevice correctly obtains not only3D shape data, but the corresponding colour textureinformation of fingerprints. Thus it provides technical support and experimental platform forsubsequent high precision fingerprint recognition theory research and practical application.