Study Of Colony Species Detection Technology Based On Terahertz Time-Domain Spectrum

Terahertz wave refers to the electromagnetic wave whose frequency is within the range of 0.1-10THz(wavelength is 30-3000 ?m).Combining the advantages of electronics and optics,it has the characteristics of safety,fingerprinting,penetration,water absorption,high signal-to-noise ratio and so on.Terahertz time-domain spectroscopy(THz-TDS)is a technology that uses femtosecond pulses to generate picosecond time-resolved terahertz electric field,so as to obtain the amplitude and phase information of Terahertz signals,and further calculate the absorption parameters of samples.Because of its non-invasive and non-ionizing characteristics,terahertz wave has a very broad application prospect in medical imaging,nondestructive testing,and material identification.This paper first introduces the relevant theories of terahertz,then attempts to build the THz-TDS system,and studies the terahertz time-domain spectrum imaging system and terahertz time-domain spectrum detection technology through the work of colony nondestructive survival state assessment and strain identification.Firstly,the terahertz time-domain spectrum images with different optical parameters were compared,discussed and analyzed,and the colony nondestructive survival status was evaluated by intensity and reflectivity images to study the terahertz time-domain spectrum imaging technology.The intensity and reflectance imaging of the sample colony were performed using the reflection imaging mode,and the intensity and reflectance images were comprehensively compared and analyzed,and the intensity and reflectance data were selected to analyze the intensity and reflectance spectrum lines of the four species within the frequency range of 0.2-2 THz.Record the colony image of each time period and growth rate,moisture content and mortality and a series of quantitative analysis,the calculation for parameters of the final results:image intuitive observation and colonies actual statistical data,high reflectivity image and visible light image edge fitting,more suitable for the colony nondestructive survival condition assessment.The second is to extract fingerprint information such as refraction coefficient and absorption coefficient of samples through terahertz time domain spectrum,and classify strains with support vector machine to study terahertz time domain spectrum detection technology.In the THz band,the absorption and dispersion characteristics of the material are fingerprinting.Using terahertz time domain spectrum detection technology to detect bacteria is to directly take the colony as the experimental object,simplify the sample preparation process,and shorten the sample preparation time by more than 5 times.The influence of water on the terahertz time domain spectrum was reduced by heating and drying the samples and pressing the plates.Conclusion:Although the treated samples still contain water(THz wave absorption rate is high)and the samples are complex mixtures,which cannot meet the requirements of THz fingerprint spectrum,the intensity spectrum and reflectance spectrum of the four strains are significantly different,including the specific information of the strains.The Support Vector Machine(SVM)model was used to classify and identify the strength spectrum of four strains.When the radius parameter was greater than or equal to 0.3(?2?0.3)and regularization coefficient was greater than or equal to 0.9(??0.9),the accuracy rate could reach 100%,which proved that THz strength spectrum contained the characteristics of different colonies and also verified the feasibility of THz-TDS system for the direct identification of colonies.