Research And Implementation Of FPGA-based Finger Vein Detection Device

Finger vein recognition as a living identification technology has the advantage of high security and confidentiality.In order to capture high quality finger vein images,improve the recognition rate of identity verification and reduce the false recognition rate,a hardware device based on FPGA finger vein image detection is designed and implemented in this paper.The main work is as follows:1.The structure of the finger vein detection device is studied and designed.Based on the analysis of the characteristics of three different lighting methods,the top-transmitted lighting method is used in this design.By analyzing the absorption effect of different body components on different wavelengths of NIR light,850 nm wavelength NIR LED was selected as the imaging light source.The NP850 infrared filter is selected to reduce the influence of visible light on the imaging quality of finger veins.In the imaging process,in order to achieve the maximum clarity of the vein image,the lens focal length,aperture,field of view angle and depth of field were analyzed in the actual design,and the final focus distance of 3 cm was determined,and the finger imaging length was about 3.8 cm.2.In order to realize the acquisition and real-time observation of vein image data,the overall system of finger vein image detection device is designed.For the hardware part,the circuit design of the finger vein system is carried out;for the software part,the RTL coding of the communication of each module of FPGA is carried out using Verilog to realize the functions of finger vein image data acquisition,processing and transmission,and the image transmission rate can reach 95MB/s.In order to observe the finger vein image in real time,Visual Studio In order to observe the finger vein image in real time,Visual Studio 2017 is used for upper computer software development,and good results are achieved.3.In order to achieve high quality vein image acquisition,an image quality assessment algorithm is integrated in the host software using image quality assessment indexes such as contrast,information entropy,equivalent visual number,blur,etc.,to ensure that the acquired vein images are of high quality;to improve the imaging quality of vein images,an adaptive dimming algorithm based on histogram light intensity assessment is designed.Through histogram statistics,we analyze the pixel area share,image mean value and local exposure of finger vein images to get the evaluation result of light intensity,and compare the evaluation result with the expected result to calculate PWM output and complete adaptive dimming.The algorithm is experimentally proven to have good applicability.The comprehensive experiment proves that the FPGA-based finger vein detection device developed in this paper can complete adaptive dimming and acquire finger vein images with 640×480 resolution according to different fingers;it takes less than 10% of FPGA resources to achieve the function of each module of the device;the image quality can be identified and high quality vein images can be saved by the upper computer software.