Study Of Detection Technology Based On Terahertz Time-Domain Spectrum

With the terahertz time-domain spectroscopy technology,time-domain spectrum of matter could be obtained,related optical parameters such as refractive index spectrum,absorption spectrum and dielectric constant could be calculated by optical parameters calculation model,and the main structure of the materials,the composition and chemical properties could be further analyzed also.Terahertz time-domain spectroscopy technology is widely used in the field of material identification and composition analysis.THz time-domain spectroscopy imaging technology can be not only used in the security inspection of public places such as train station,bus station and airport,but also can used in the defect detection of non-polar material such as foam,fiber and integrated circuit palte.THz imaging technology provides a new way for the existing security inspection technology and defect detection technology.Main text was listed in following:(1)Designed a set of two-dimensional platform for imaging which based on terahertz time-domain spectroscopy,the platform controller based on ARM processor were designed,meanwhile,THz automatic scanning software and THz image processing software that fit the imaging system were developed based on VC++ software,and automatic scanning imaging and processing were realized successfully.(2)The THz time-domain spectroscopy of synthetic pigment amaranth were obtained.Based on the optical parameters calculation model,the refractive index spectrum and absorption spectrum in THz wave band were obtained also.It offers a new way for the pigment detection in the field of food additives detection.The source of absorption peak of amaranth molecules were analyzed and simulated with the method of molecular density functional simulation.Compared the simulation result and experimental result,identifying of the source of absorption peak of amaranth,laid the theoretical basis for the realization of the Terahertz imaging technology and the Terahertz time-domain spectroscopy.(3)Material classification and recognition based on THz characteristic spectrum were further studied.The terahertz time-domain spectroscopy of amaranth,tartrazine,flour,tartaric acid,ascorbic acid,lactic acid,VB16,candesartan and hydrochloric acid rosiglitazone these nine kinds of standard analysis product were obtained through the terahertz time-domain device,and based on the optical parameters calculation model,the absorption spectrum of these nine kinds standard analysis product were obtained respectively,on the basis of the optical parameter information,the corresponding characteristics of THz spectrum library were established,it provides a theoretical basis for material classification and recognition.Finally,the LS-SVM was used for the analysis and modeling of the established THz spectrum characteristics library,and a set of material online detection and identification system based on THz characteristics spectrum library were developed using VC++ and Matlab mixed programming technology.Successfully realized the on-line detection and recognition.(4)The imaging principle and imaging method based on terahertz time-domain spectroscopy were studied in depth.Metal knives and defective wires were used as the research object,THz image of metal knives hidden in the kraft paper and wires with complete appearance and broken internal were got respectively by using the improved terahertz time-domain device and THz imaging auxiliary software.Then THz image processing software developed independently was used for gray,filtering,binarization and other conventional image processing,in order to enhance effective information of the target,reduce the effect of noise,background and other factors on the target,to make it easy to quickly identify the target.Knives hidden in the kraft paper and the defective location of wires were defected successfully in the experiment.This provides a new model for the method used in security field and defect detection field.