Differential Confocal Microscopy Based On Radial Birefringent Pupil Filtering

In the field of microscopy measurement, the accurate detection of themorphology and structure of microscopy objects is becoming one of the concernsof modern science and technology. Accompanied by the rapid development ofsemiconductor technology, biomedical technology and quantum technology, thereis more and more demand for the detection of ultra-precision machining andmicro-structure. It is one of the urgent problems to be solved to find a newapproach to simplify the complex structure of system with capability of highefficiency and high-resolution.The paper “Differential confocal microscopy based on radial birefringentpupil filtering”, is to solve the problem of three-dimensional high-resolution inconfocal microscopy measurements. On the basis of the birefringent filter theoryand the principle of confocal microscopy imaging, we combine them and introducethe differential confocal theory into the confocal system with radial birefringentpupil filter to realize3D high-resolution optical measuring, in order to solve thekey issues in the development of modern confocal microscopy. The results of theresearch can be applied to the field of biological engineering, microelectronics,ultra-precision optical processing to achieve high spatial resolution detection andimaging.The paper is organized as follows:First of all, carry out researches on radial birefringent pupil filtering method,optimize and produce the birefringent filter, and thus effectively reduce the lateralwidth of the main lobe, and finally gain a filter whose super resolutioncharacteristics can be modulated continuously. Characteristics of axial and lateralresolution can be changed with its own parameters. At the same time, the structurebeing simple, the production does not involve a phase change. It is easy tomanufacture with a low cost, and provides a feasible method for the confocalmicroscopy measurement.Secondly, to seek for a confocal measurement method with3D superresolution characteristic, combine radial birefringent pupil filtering technologywith differential confocal measurement, therefore, to obtain a confocal microscopymeasuring principle with high lateral and axial resolutions.Then, study characteristics of confocal microscopy imaging method based onradial birefringent pupil filtering. Further optimize parameters of the filter in thetwo systems. The results show that the lateral width of the main lobe of the system reduces by18%after combining the optimized birefringent pupil filter withconfocal system.Finally, the confocal microscopy system is established based on radialbirefringent pupil filtering, and its principle is verified by experiments. Theexperiment results show that, the axial resolution of system is3nanometers in thecase of NA=0.65and wavelength equals632.8nanometers, and the error of themeasured lateral line width is less than0.077micrometer in comparison to thecalibration value of the standard gratings, the relative error is5.133%; and innormal confocal system without radial birefringent pupil filtering, the errordecreases0.107μm, that is to say the relative error is reduced by7.134%.Meanwhile, the differential confocal microscopy device is founded according toradial birefringent pupil filtering, and the theoretical characteristicsare verifiedand analyzed by experiments. Experiment results show that, in the conditions ofNA=0.65, λ=632.8nm, the system can achieve an axial resolution of3nm, andthe error of the measured lateral line width is less than0.083micrometer, therelative error is6.100%; and in normal confocal system without radial birefringentpupil filtering, the error decreases0.058μm, that is to say, the relative error isreduced by1.933%.