Study Of Portable Microscope Based On Tapered Fiber-Optic Array

Optical microscopes have been widely used in biomedical detection in various fields such as cytology,oncology,genetic engineering,and botany.The traditional high-resolution optical microscope has the disadvantages of large volume,high price,and professional operation in the laboratory,which limits the application of micro-detection technology applied to individual users and the point-of-care test(POCT).Therefore,the development of a portable microscope with micron-level resolution and small distortion is of great significance and has broad application prospects.To address this need,optical lens is widely used as a solution for commercial portable microscope due to their stable performance and low cost.They can meet with the general needs of industrial and biomedical detection,but there are disadvantages such as low resolution,large distortion,and small field of view(FOV).To cover up these deficiencies and provide supplementary solutions,this thesis introduces a tapered fiber-optic array(FOA)that can be used for distortionless imaging in a portable microscope.Three prototypes including relay-FOA,coupled FOA,and coupled FOA with pre-lens have been designed and developed.Meanwhile,their performances including the resolution,FOV,distortion and volume are investigated.Finally,by using of pattern recognition and image preprocessing,the microscope based on the coupled FOA is applied to the yeast classification,which further expands the application of portable microscope in biomedical detection.The main contents and contributions of this thesis are as follows:1.Development of a sleeve microscope with relay-FOA and lens.Objective lens has the deficiencies that higher-magnification objective with high distortion,and the lower-magnification objective with lower resolution.Allowing for the characteristics of high numerical aperture(NA)in the FOA,distortion-free magnification and high coupling efficiency,the prototype with low-magnification objective(4 X)and the FOA(6 X)is designed to obtain higher resolution and smaller distortion at the same time.The results prove that no visible distortion is found.However,the microscope resolution was still 4.4?m after adding the FOA,which failed to achieve the purpose of improving the resolution.Meanwhile,the detailed information of blood cells could not be recognized by the microscopic observation.2.Development of a portable microscope based on coupled FOA(FOA microscope).A portable microscope based on the coupled FOA is designed and developed.The FOA is attached(coupled)to the surface of the CMOS image sensor in the smartphone.The microscope with no visible distortion and chromatic aberration,can achieve a resolution of up to 3?m,which is equivalent to that of an objective-based microscope(10 ×,NA=0.25).The field of view(FOV)is 0.64 mm2,which is 4 times that of the objective microscope(10×).Because there is no lens used in the structure,no focusing is required,and the volume is greatly reduced.The microscope tube is only 32mm in height and 25mm in diameter.3.Analysis the factors that affecting the coupling efficiency of the FOA microscope,and proposition of corresponding improvement measures.The geometric optical transmission path of light in the coupled FOA microscope was analyzed.The factors that affect the coupling efficiency and signal-to-noise ratio(SNR)are the NA of the FOA,the effective fill factor,the reflectivity of the surface,and the refractive index of the coupling medium.The key parameters and corresponding designing measures during the microscope processing are proposed,which provide theoretical guidance to improve the resolution of the FOA microscope.4.Development of a portable high-resolution microscope based on coupling FOA and pre-lens.To further improve the resolution,a pre-amplification lens(40 X)was added in front of the FOA.The lens overcomes the defect of under-sampling limited by the size of the fiber core in the FOA,and improves the resolution from 3?m to 1?m.The contour and structure of the yeast can be recognized in real time.The FOV is 140 ?m×100?m,and the distortion is 0.19%,which is only 0.06%larger than that of FOA microscope.This distortion rate is still much lower than most portable lens-based microscopes on the market.5.Usage of the FOA microscope with the pattern recognition algorithm for class.To address the needs of yeast fermentation status monitoring in baking and winemaking,a solution based on the FOA microscope is proposed.First of all,the adaptive histogram equalization(AHE)is used to improve the uneven illumination and the artifact caused by the"fiber island" in the microscopic image.Secondly,a matching convolution detection window is designed for the morphology and gray distribution of live and dead cells,respectively.The image can be scanned by the above convolution window row-by-row and line-by-line to obtain the distribution and number of yeast cells.The results proved that the percentage of the dead and live cells correctly identified are 92.8%and 85%,respectively.This solution has the advantages of simple operation,low cost,and high accuracy compared with the methods based on the machine learning.