| Optical coherence tomography(OCT)is a novel biomedical detection technology.Because of its non-invasive,high-resolution,real-time imaging,it is often used in biomedical and industrial fields.The OCT technique continues to develop and it has been used to measure the internal structure of biological samples.By measuring backscattered light,two-dimensional or three-dimensional imaging of the internal microstructure of biological tissue is performed,and real-time imaging of living biological tissue is realized.The most common application of OCT is ophthalmology.Since the OCT technology is high-resolution,non-invasive imaging,it has great application prospects in retinal structure observation.In addition,OCT can also be used for the detection of optical thin films.Analyzing the interference spectrum collected by the spectrometer can obtain the structural information of the thin film,and further,the characteristics such as the thickness and refractive index of the film can be obtained.The main content of this paper includes two aspects: optimizing the data processing process of interference signals collected by spectral domain OCT(SD-OCT)system;and detection technology based on SD-OCT system,while simultaneously measuring the thickness / refractive index of the thin film.In terms of data processing:(1)The advantages and disadvantages of the three wavelength calibration techniques are compared in this paper.The analysis of the results shows that the calibration method based on the phase of the interference signal has the highest sensitivity of 2.336 dB / mm.(2)The effect of wavenumber nonlinearity on the half-height width of the coherence function is analyzed.After re-sampling the signal through cubic spline interpolation and zero-fill interpolation,the system maintains a good axial resolution within the detectable depth range,and improves the system's sensitivity and signal-to-noise ratio.(3)Two curve Gaussian fitting methods are studied,and finally a method of Gaussian spectrum shaping combined with spectral windowing is proposed to suppress the side lobes of the system by 8.89 dB and the signal-to-noise ratio of 33.32 dB.The system axial resolution is 6.7058?m.Finally,the system was used to perform imaging experiments on infrared cards and finger skins.The results show that after using the optimized algorithm,the image quality of the system is effectively improved.In the detection aspect,two methods are used to simultaneously measure the film thickness and the refractive index:(1)Optical path difference method,this method is suitable for single-layer film systems,the experimental steps are simple,little calculation,and low cost,this method is insensitive to group velocity dispersion in the sample,the measurement accuracy depends on the resolution of the system.(2)The Fresnel coefficient method directly uses the interference signal collected by the OCT system without performing Fourier transform.This method requires high stability of the light source and is suitable for the measurement of weak scattering media.The accuracy of the membrane system still needs to be improved because it ignores multiple scattering inside the membrane layer. |
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