| Comparing to digital holography,digital holographic microscopy(DHM)is a new type of three-dimensional(3D)microscopic imaging technology with higher resolution.It can ben widely used in the morphology measurement in the microscopic field,and microfluidic system is one of its important application fields in recent years.The microfluidic chip is the main operating platform of the microfluidic system,and the quality of its channel directly affects the operation of sample’s injection,separation and measurement in the microfluidic system.Therefore,the 3D topography detection of the microfluidic chip channel is of great significance to evaluate the quality of the microfluidic experimental system.According to the size and structure characteristics of the microfluidic chip channel,this thesis uses digital holographic microscopy to achieve high-resolution,high-quality 3D topography measurement of the microfluidic chip channel.The main research contents and achievements of this thesis are as following:(1)Based on the introduction of traditional optical holography and digital holography,digital holographic microscopy is systematically introduced,including amplification mode,optical path structure,recording and reconstruction principles of image plane digital holographic microscopy and two classical phase unwrapping algorithms.In addition,the actual magnification and transverse resolution of the digital holographic microscopy experimental system are calibrated.(2)The phase distortion correction method for low spatial frequency objects with large transverse size in the field of view in digital holographic microscopy is discussed.Based on the theoretical analysis,simulation and comparative analysis of experimental results of step standard sample,it is proposed that the two-step method is more suitable for phase distortion correction of this type of object than the surface fitting method.(3)Based on the theoretical analysis of dual-wavelength phase unwrapping,the effectiveness of dual-wavelength phase unwrapping is verified by simulation and segment difference standard slice experiment.In addition,a phase compensation algorithm based on image segmentation is proposed to solve the problem of phase compensation errors existing in traditional phase compensation methods in dualwavelength imaging systems.(4)A dual wavelength digital holographic micro measurement system with adjustable equivalent wavelength is designed and built.Based on the repeatability and stability evaluation of the measurement system,the high-quality 3D topography reproduction and the measurement of width and depth of the microfluidic chip channel are realized.The experimental results show that digital holographic microscopy provides a new way for fast and non-destructive measurement of microfluidic chip channels,which is of great significance for the quality evaluation of microfluidic experimental systems. |
