Design Of The Full-field Optical Coherence Tomography System

In most countries,including China,malignant tumors have become one of the major diseases that seriously damage health of human,so it is necessary to quickly diagnose malignancies.In modern clinical medicine,biopsy is regarded as an important method for diagnosing lesions,the preoperative section-making process of which is complicated,time-consuming and prone to delayed diagnosis,the intraoperative section-making results with poor resolution of which are prone to missed diagnosis and misdiagnosis.As a cutting-edge biomedical imaging technology,Full field optical coherence tomography(FFOCT)has the ability to distinguish between normal tissue and cancerous tissue.Its imaging characteristics of real-time,non-destructive,submicron resolution lay the foundation for replacing traditional biopsy for rapid assistant diagnosis.In this study,a large field of view FFOCT system is designed to improve the imaging speed,aiming at the problem of mismatch of pupil and small field of view of the existing optical coherence tomography system prototype.The main work of the paper is summarized as follows:(1)The low coherence interference theory of FFOCT system and the scattering characteristics of biological tissue are discussed.On the basis of keeping the basic structure and main parameters of the FFOCT experimental system unchanged,the imaging and illuminating optical paths are designed separately by using ZEMAX software through pupil matching and image quality optimization.The design results show that the system has an image quality close to the diffraction limit for the tissue with a field of view diameter of 0.675 mm,which is 82.75% larger than the imaging field area of the experimental system.The designed concentrator group is converted to non-sequential mode,and the improved K?hler illumination system composed of condenser lens and ideal microscope objective is simulated.The simulation results show that the edge of the spot is clear and uniform,thereby achieving uniform illumination of the surface to be measured.The imaging light path and the illumination light path are combined to obtain the FFOCT whole system,and the interference fringes of light and dark are obtained.(2)The tolerance analysis of the imaging optical path and the illumination optical path of the FFOCT system is carried out respectively.The results show that 80% of the simulation results of the imaging optical path within the corrected tolerance range meet the expected requirements,and the image quality of illumination optical paths does not change significantly under the tolerance of medium accuracy.In addition,the engineering results of template matching,optical part drawing and optical system drawing are carried out on the design results of the FFOCT system.The results show that the system has engineering application level.(3)The main stray light of the FFOCT system is analyzed as ghost image and extra-field stray light.The path and energy data of the secondary ghost image of the imaging optical path are obtained in the sequence mode of ZEMAX and CODE V,the image plane distribution of the secondary ghost image is generated in the nonsequential mode of ZEMAX.The tracePro software is used to model the optomechanical system and simulate the stray light outside the field of view,and the point source transmittance at different off-axis angles is calculated.The results show that FFOCT system has no obvious ghost image,and has a certain ability to suppress the stray light outside the field of view,which meets the requirements of optical coherence tomography.