Two-dimensional Fourier-domain Coherence Tomography System And Its Applications

Optical coherence tomography(OCT)is a technology that uses low-coherence light source and the Michelson interferometer as the technique core device,it's a high-resolution interference imaging technique which obtains the structural information of samples by detecting the reflected or backscattered lights from the detected samples.OCT technique has the advantages of non-destruction,non-contact and high-resolution.The Fourier-domain OCT(FD-OCT)is developing faster and faster,because of its advantages of high imaging acquisition speed and low noise.FD-OCT system can be used for two-dimension imaging of biological tissue,which can present the internal structural information of biological tissue clearly,like thickness and so on,which is of great help for diagnose of pathological changes of tissues.The technique has offered medical diagnose a new high-precision testing and measuring method,which has remedied the defect of traditional medical testing.In recent years,OCT has also been used for industrial non-destructive testing,mechanical vibration and other non-medical fields.However,the traditional single-point OCT system needs to scan the samples point-by-point to get its two-dimensional images,resulting in slower imaging speed.To this end,the dissertation studies the two-dimensional FD-OCT system and its applications,from the following aspects:The theory of OCT technology is deeply analyzed in the dissertation.The system structure and the imaging principles of the system have been demonstrated briefly,the core parameters of the OCT system have also been analyzed.Two dimensional FD-OCT system has been designed and constructed autonomously,the core affection parameters of light source part,spectrometer part and so no on the performance of the system,like detecting depth,resolution and SNR has also been analyzed.With the use of single-frequency laser,the dissertation mainly utilizes the optical principles like the reversibility of light path,optical reflection,optical path difference doubling to insure the concentricity and perpendicularity of instrument in system,and make sure the travel direction of reference light and the sample light accords to each other.Compared to traditional FD-OCT which needs to make transverse scanning,the two-dimensional FD-OCT system can capture the two dimensional structural information through single scanning.The developed FD-OCT system has improvement in performance indicators and imaging speed compared with the traditional OCT,which can provide some reference value for OCT application.In view of the calibration accuracy of the spectrometer has a direct influence on system SNR,dynamic range and resolution in FD-OCT.The method of spectral calibration based on interference fringes has been raised innovatively,the spectral bandwidth and the abscissa regularities of distribution have been demarcated precisely,the precision is better than the traditional method.Experimental results show that the resolution and the SNR of the OCT system could be greatly improved after the wavelength calibration.For the problem of that the image contains the structural information,besides,the self-coherence noise,the direct current noise,the complex conjugate disturbance also contained.To solve these drawbacks,the method of two phase filtering using PZT and the method of five phase shift have been employed,the needless noise has been filtered off,and greatly improved the OCT image quality.In the application field,various samples in different fields have been tested using the developed FD-OCT system,including industrial materials such as,the toughened membrane,solar battery,mouse eyeballs and other biological tissues.In particular,the OCT system can quickly and clearly image the mouse's cornea,iris,lens and retina and other parts of the structure.The results of the experiments have manifested that the system has a better resolution and reliability.It can provide experimental support and reference for engineering and medical applications.