Data Processing In Optical Coherence Tomography With Double Reflection Interferometer

Compared with X-ray medical imaging technology,the optical tomography technology using ordinary light waves as the information carrier is to use the absorption,scattering,reflection and other effects of biological tissue to change the amplitude,phase and polarization of light waves to obtain the internal information of biological tissue,which is safe.The advantages of lossless,high sensitivity and high resolution.Extracting biological tissue information from optical signals is the key to optical tomography.Optical coherence tomography technology uses low-coherence interference to accurately obtain light change information in a medium,and has been widely used in clinical diagnosis and material testing.Axial resolution is an important index to measure the performance of optical coherence tomography system,which is mainly determined by the spectral width of the light source.The method of increasing the axial resolution by increasing the spectral width of the light source will greatly increase the cost of the system,and limited by the working band of the material,the improvement of the axial resolution of the system is limited.In order to improve the performance of optical tomography,our research group preprocesses the interference data of the double reflection interferometer optical tomography system to reduce interference,and uses data processing methods to widen the spectral width of the light source to improve the axial resolution of the system.Rate.The main work of this thesis is to establish a double reflection interference optical tomography system based on low coherence technology,and to process the data to improve the imaging quality of the system.Firstly,the principle of low coherence interferometry is summarized in combination with Michelson interferometer,the structure and principle of several different optical coherence tomography systems are introduced,and the influencing factors of the axial resolution of the tomography system are analyzed.The deficiencies of the existing methods for improving the axial resolution are pointed out,and a method of data processing is proposed to widen the bandwidth of the light source,thereby improving the axial resolution.Based on the time-domain optical coherence tomography system,a double interference reflection optical tomography system is established.The effect of different devices on system performance.Then,according to the systematic analysis of the causes and characteristics of the trend items and noise in the signal,the tomographic data were processed by different methods.The processing results show that the least squares is not suitable for the extraction of the trend items of the data in this system,while the Savitzky-Golay filter can extract the trend items in the tomographic data more accurately,but it will lose some useful information.reduce the loss of useful information;for noise removal,wavelet threshold denoising has a better effect,while least squares adaptive filtering will lose part of the interference signal,normalized least squares adaptive filtering can be used to a certain extent.To reduce the loss of interference signal;the envelope extracted by the Hilbert transform method is not smooth and has burrs,and the envelope obtained by the interpolation method of the extreme point of the interference signal is relatively smooth.Finally,the principle of the adaptive nonlinear prediction method is deduced.In order to verify the feasibility of the method of improving the axial resolution of the system,the nonlinear adaptive prediction method is used to predict and simulate different types of signals.The results show that the nonlinear adaptive prediction method is more accurate for the prediction of periodic signals,but for the signal that decays too fast,a large error will occur with the increase of the number of data points.