Study On Several Key Techniques For Improving Resolution Of Optical Coherence Tomography

Optical coherence tomography(OCT)is a new imaging technique,it has some good qualities such as: non-invasion,non-radiation,high resolution and high sensitiveness.This makes it great potential in many areas.For example:clinical medicine and industrial inspection.The resolution of OCT is a key technique to affect the imaging.In order to improve the resolution of OCT imaging,several other key techniques are studied in this paper.The main contents of this paper are as follows:(1)Study on OCT synthetic light source which is composed of several infrared LEDs.In this project,We select the LED which center wavelength from 850 nm to 890 nm,and the the frequency interval of adjacent two LED is10 nm,to form a synthetic light source.And made a theoretical analysis of it.Then,use the optical software Virtuallab to model the OCT system,and import the light source with different LED combination into the light source,then,compared the coherent waveforms of different combination.The results show that the resolution of 3 to 5 light source can respectively reach 8.68 um,7.48 um and 6.63 um,reach the level of resolution one SLD light source.(2)Design of LED lens group: In order to make the light of each LED focus into the OCT fiber optic system,the coupling lens is the key element.On the basis of the effect of collimation focusing from TIR lens and the non spherical lens,three kinds of lens:spherical lens,self focusing lens and micro lens,are used to assistant the TIR lens and the non spherical lens.Then use the optical software ZEMAX to optimize the three system,to make each of them the maximum coupling effect.the results showed that the coupling efficiency of micro lens is the best,the efficiency is 70.1%.(3)Study on the formation mechanism of speckle.Using OCT image of pig stomach and foam plastic tube as the object,four kinds of mature image processing algorithms are used to deal with the OCT images: the medianfiltering,Wiener filtering,wavelet filtering and anisotropic diffusion method.After the images are processed.The SNR,ENL and speckle index are used to quantitativly analysis the effect of noise reduction.through the three indicators of the four algorithms,the anisotropic diffusion method to get the best effect.(4)Suppression of sidelobe interference of non Gauss source in coherent waveforms.Based on the simulation results of the interference spectrum of synthetic light source,Four window functions are used to cut the toe of interference spectrum,Then the best window function is selected from the post processing coherent waveforms,and the sidelobe suppression of the non Gauss source is realized.