Design Of Dual-wavelength Near Infrared Vein Imaging Light Source

With the development of near infrared(NIR)imaging technology,the research of near infrared venography based on the absorption difference between subcutaneous veins and surrounding skin tissue has been carried out continuously.According to the analysis on the venous imaging systems and research results in recent decades,the differences in the environment and the physiological factors of individual subjects have great impact on the image of the venous imaging system,which is largely due to the system light source.Aiming to solve the problem by improving the light source of the venous imaging system,a dualwavelength NIR vein imaging light source is designed in this thesis,in which a closed-loop control mechanism is introduced to adjust the luminance automatically by using image evaluation feedback,and a dual wavelength image fusion algorithm is applied to enhance the contrast of subcutaneous veins image as well.The main works are as following:1.An adaptive dual-wavelength lighting source is presented to realize illumination adjustment according to individuals.The captured subcutaneous vein images are used as a feedback to regulate the light intensity automatically.The contrast of subcutaneous veins image can be improved by fusing vein image originated from dual wavelength vein images.2.The dual-wavelength near-infrared light source system for vein imaging device is designed and accomplished,including system structure,lighting module circuit,light source control module and adaptive feedback module.The dual-wavelength near-infrared light source prototype is completed.3.An adaptive light intensity closed-loop control algorithm based on two-dimensional entropy evaluation of vein images is proposed and implemented,which includes: the local two-dimensional entropy evaluation algorithm and the adaptive light intensity adjustment parameter feedback calculation on host computer;the light control program on hypogynous control station;and communication interface between the host and the hypogynous station.4.The processing and fusion algorithm for the dual wavelength near-infrared vein image is designed and completed,including image denoising,ROI extraction,image enhancement and vein extraction,in which the gray-scale modulation method is used to fuse the dualwavelength NIR images.The experiments conducted on multiple subjects is designed and the enhanced vein images are evaluated using FDR.The experimental results show that the information entropy and FDR of the processed images have increased comparing to the original images,which indicate that the dual wavelength NIR light intensity adaptive control system can work stably.The theoretical analysis and experimental results show that the dual-wavelength vein imaging system in this thesis can adaptively adjust the light intensity according to individuals' physiological factors and can provide uniform and good illumination for the venous imaging system.After the fusion of dual-wavelength vein images,the contrast of subcutaneous veins image is improved,which can lay a good foundation for catheter insertion and vein identification.