The uniqueness and stability of fingerprints make it one of the widely used biometric identification technologies. I love the scheme of smart home fingerprint identification access control system introduced by F3 fingerprint recognition system, combined with Linux design, can Achieve accurate and fast authentication to achieve the function of opening and closing the door and the fast alarm function.
Before we introduce the design, let's review the principles of fingerprint recognition technology.
First, the technical principle of fingerprint recognition
The technical principle of fingerprint recognition is to find out whether the fingerprint data matches the fingerprint collection from the fingerprint database, and achieve the purpose of switching the door lock by distinguishing the identity. The basic principle is shown in Figure 1. The fingerprint identification system consists of fingerprint image acquisition, fingerprint image preprocessing, fingerprint feature extraction, fingerprint feature matching, and feature database. Fingerprint image preprocessing uses Gabor filtering method to perform grayscale filtering to denoise. After filtering the image, it is binarized to filter out or correct various noises. The fingerprint feature extraction is based on the statistical analysis of the neighbors of the point 8. The feature points are obtained by calculating the CN (Croosing Number). The process of fingerprint feature matching is a process of calculating the similarity degree of two fingerprints. Before fingerprint matching, different fingerprint images must be calibrated to find the best transformation between the input feature point set and the template feature point set.
The fingerprint identification system can be roughly divided into two parts: fingerprint registration and fingerprint comparison. Fingerprint registration mainly includes fingerprint collection, fingerprint image preprocessing, feature point extraction and feature value storage. The first 3 steps of the fingerprint comparison are exactly the same as the fingerprint registration. After the feature points are extracted, the generated fingerprint feature values ​​will be matched with the feature values ​​stored in the fingerprint feature database, and the matching result will be output.
Figure 1 Basic principles of fingerprint recognition technology
Second, fingerprint recognition access control hardware principle
The fingerprint identification access control system designed in this paper is mainly composed of FPI fingerprint identification module, Raspberry Pi main control module and AVR module. The hardware structure is shown in Figure 2.
The three-party communication realizes the fingerprint input and matching of the user, and the switch of the door lock, and monitors the state of the door lock by sending an email.
·FPI fingerprint recognition module's powerful image processing function is very sensitive to fingerprint recognition, timely processing received fingerprint information, and communicating with Raspberry Pi;
Raspberry Pi module, on the one hand, controls the AVR to detect the switch status of the door and switch the door lock, on the other hand controls FPI fingerprint entry and matching, and establishes a database to record user information on the Raspberry Pi;
The controller AVR feeds back to the switch state of the Raspberry Pi door and controls the motor to open and close the door lock, which enhances the hardware expansion and can monitor the door in more aspects through hardware.
In addition, the wireless communication module is used to avoid the damage of the original door lock structure caused by excessive wiring, and the hardware composition of the system is convenient and fast.
Figure 2 Hardware structure of the fingerprint identification system
Fingerprint identification module
The fingerprint module is based on TI's TMS320VC5509 advanced digital DSP processor as the main core, and the chip structure block diagram is shown in Figure 3. High-precision optical acquisition head (TFS-D0307), high-speed, stable; standard UART interface communication, standard 8-byte communication protocol, FPI finish processing the received fingerprint information, and communicate with the Raspberry Pi main control module.
Figure 3 fingerprint identification chip FPI
Shenzhen Joy LED Display Co., Ltd. , https://www.joe-led.com