System Of Polarization-sensitive Optical Coherence Tomography Base On Single Camera And Its Application

Optical coherence tomography(OCT)is a non-invasive imaging modality with high resolution,which has been widely used in many fields,especially in biomedical applications.There is a variety of functional imaging OCT types.Polarization-sensitive OCT(PS-OCT)is one of the important technologies.PS-OCT could not only acquire intensity image but also detect tissue polarization properties that are not provided by a conventional OCT.Previous PS-OCT system was used to detect two images with two orthogonal polarization states in order to acquire sample birefringence properties,and dual spectrometer cameras were utilized to detect the horizontal-channel and vertical-channel respectively.The method made the system cost rise obviously,and needed complex software and larger-sized apparatuses.Several PS-OCT techniques have been developed,but they all have some flaws.In this dissertation,a new configuration with a single line-scan camera is demonstrated to achieve the polarization sensitive imaging based on time divided detection.The main works are summarized as follows:1.The PS-OCT was based on spectral domain OCT(SD-OCT),so a SD-OCT system with reliable performance has to be constructed first.The SD-OCT system at 1310 nm wavelength based on Michelson interferometer is developed.It is combined with new spectrometer phase calibration technology which does not require direct scaling of the wavelength.This enables us to construct the system so easily.Through the preparation of imaging software and to optimize the data processing process,the system was built successfully.With the maximum A-scan rate of 76KHz,the system axial imaging range is 5.8 mm,the axial resolution is 12um,which is capable for real time in vivo imaging of biological tissue samples.In this paper,the imaging speed is 20 fps,and each frame contains 1000 A-scans.The 3d images after post-date processing are also acquired 2.A new configuration with a single line-scan camera is demonstrated to achieve the polarization sensitive imaging based on a free space SD-OCT.Two reference arms and a quarter-wave plate(QWP)on sample arm were used to provide a reliable orthogonal polarization state of light.And an electronic control light shutter was positioned in the front of the mirror of the two reference arms.Only one polarization image could be detected in one moment when the two LS take turns to switch.Therefore,it means that the two orthogonally polarized images could be detected by time divided detection.In other words,it only needs single line-scan camera for the PS-OCT system.The imaging speed of the system is 15 frames per second.In order to verify the system performance,the retardance of the quarter wavelength plate is measured,resulting in(87±2)°.It demonstrated that the current system could be capable of acquiring polarization sensitive images reliably.Polarization imaging of biological tissue samples was carried out and the birefringence was measured quantitatively.3.A single camera PS-OCT system based on polarization-maintaining(PM)fiber was proposed,which was based on orthogonal channels by time divided detection.The method of using dual reference arms combined with optical switches so as to solve the issue of optical path inconsistency in traditional PS-OCT by adjusting optical length independently in the dual reference arms.Polarization tester was introduced to the polarization detection and adjustment of the orthogonal polarization channels.It can minimize the crosstalk between the fast and slow axis of PM fiber.The imaging speed of PM fiber PS-OCT system based on optical switch is dependent on the speed of optical switch and the camera.With the help of the different speed of the optical switch between 2KHz-1MHz,different data acquisition method was utilized.In this dissertation,the B-scan images of two orthogonal chanels were detected by turns.The retardance of the quarter wavelength plate is measured to verify the system performance.Biological tissue sample was also used to be imaged by the PS-OCT system.The result of the birefringence is consistent with the free space PS-OCT system.Finally,the mueller's image of a composite sample was measured,which consisted of biological tissue and non-biological material.In conclusion,a simple SD-PSOCT technology using a single line-scan camera based on orthogonal channels by time divided detection is demonstrated.Through this approach,a PS-OCT system could be constructed conveniently based on conventional SDOCT with a slight change of hardware and software.This reliable system is capable of acquiring polarization sensitive images at high speed.The PM fiber type PS-OCT is important to the system portable and stability,and it is also helpful to clinical applications.