Optical System And Synchronization For Endoscopic 3D OCT Imaging

Optical Coherence Tomography(OCT)utilizes the coherence principle of the scattered light to construct the tomographic image of living biological tissues.Because of its advantages of no damage,micrometer scale resolution and high speed,OCT is of great significance and application value in many research fields,such as biology,medicine,material science and forensic science.Endoscopic OCT imaging technology uses the endoscope to deliver the light into the human body for imaging.It has many important applications in clinical applicaton.However,there are still some challenges in endoscopic OCT.Its imaging quality needs further improvement.On the one hand,the probe is easily affected by polarization and dispersion mismatch,which leads to unsable image and the declining of image quality.On the other hand,although the three-dimensional data for fast OCT imaging is acquirable,accurate synchronization is still not applicable for the tiny endoscopic probe,leading to an unstable display of the actual image.To solve the problem of dispersion and polarization mismatch,an SD-OCT system,based on a spectrometer that is only composed of reflective optics,is designed.This new optical detection system can reduce the influence of dispersion and is expected to be applied to OCT imaging based on broadband light illumination to obtain high resolution image.Furthermore,we optimize the optical system of the reference arm and the sample arm,and we design a common-path endoscopic probe.The common-path probe can keep the same path of the reference arm and the sample arm,so the image is insensitive to the polarization and dispersion changes of the light path.Therefore,the stability and quality of the image can be greatly improved.For the synchronization method of 3D OCT imaging,we designa synchronous trigger both in optical and electronical ways.Because the return light of the endoscopic probe is not synchronized with the electrical signal of the imaging device,one of the solutions in the optical way is to extract part of the return light of the sample arm as the synchronous light signal through the optical fiber coupler and convert it to electronical trigger via electric circuit.Then the computer can draw stable 3D images based on the trigger.Another solution is to introduce a polarized light as the indicator light and get its reflection through a polarizing mirror at the end of the endoscopic probe.This reflection may generate a periodic the feedback of light signal,which may convert to the synchronous signal.We have finished the design of the special structure of this new probe.In addition,for the trigger signal in the ultrahigh speed OCT system,we also designed the digital circuits to provide the start-stop triggers to enhance the stability of the imaging display.To conclude,this work has optimized the optical system design for endoscopic OCT to eliminate the severe influence due to dispersion and plorization and proposed an effective synchronous trigger scheme for 3D OCT imaging for better stability of image display.This work may greatly enhance the performance of the OCT system and is of big importace for the clinical application.