Experimental Study On Spectral-domain Optical Coherence Tomography For Microfluidic Chip Detection

Optical coherence tomography(OCT)is a novel optical diagnostic technology with non-contact,non-damaging imaging,which enables fast,real-time and high-resolution optical imaging detection of the internal structure of scattering tissue.Spectral-domain optical coherence tomography(SD-OCT)based on the combination of Michelson interferometer and spectrometer system is an important branch of frequency-domain optical coherence tomography(FD-OCT),referred as the second generation of OCT technology.Compared with time-domain optical coherence tomography(TD-OCT)that is the first generation OCT technology,frequency-domain OCT has higher sensitivity and faster imaging speed,and has important clinical applications in biomedicine.In this thesis,we investigate some issues about measurement of micro-channels by spectral-domain optical coherence tomography.The spectral domain OCT imaging methods for microfluidic chip detection are studied.The spectral-domain OCT imaging experiments on microfluidic chips,glass tubes filled with different liquids,and microchannels filled with flowing liquid are performed.The thesis mainly includes the following contents:Firstly,the configuration and function of spectrum domain OCT system are described,and the experimental setup is optimized for microfluidic chip experiments.Secondly,the spectral domain OCT imaging experiment of micro-channels of microfluidic chip is carried out,and a method for measuring the depth dimension of micro-channels of microfluidic chip by SD-OCT system is described.The interference spectrum image about cross-sectional image of microfluidic chip channel is acquired by continuous B-scan with a pair of scanning galvanometers in SD-OCT system,and then the high quality tomographic images are obtained by digital processing of noise removal and dispersion compensation for the acquired interference spectrum image.Further,the depth size of the microchannel is calculated with the size of CCD pixels and the number of pixels occupied by the microchannel.A multiple A-line-scanning superposition imaging mode is proposed to improve imaging quality and measurement accuracy.The experimental results show that compared with typical single A-linescanning imaging mode,the multiple A-line-scanning superposition imaging not only improves the lateral resolution,but also significantly improves the axial resolution of the depth information.Further,the experiments for imaging the capillary glass tubes and the microfluidic channels are carried out in the SD-OCT system,and the factors affecting the imaging quality are analyzed.The SD-OCT tomographic images of glass tubes filled with liquids of different refractive indices and different concentrations are obtained,respectively.The effects of refractive index and concentration on the results of tomography are analyzed.The capillary glass tube filled with flowing liquid is also imaged,and the Doppler shift signal of flowing liquid in the capillary glass tube is verified by using high-pass filtering deviation method.In addition,the effect of dynamic light scattering on tomographic images are analyzed,and denoising effects with different denoising algorithms are compared.The results show that the morphological denoising image processing method is more suitable for removing dynamic speckle noise.