Design And Implementation Circular Dichromatic Microscopic Imaging System With Discrete Modulation

Circular dichroism(hereinafter referred to as CD)spectroscopy is an important tool in the study of chiral molecular structure.It can help provide useful information about the conformation and rotation of the constituent molecules and their interaction with solvents.At present,CD spectroscopy techniques are almost always in solution.Measured.Solid-state spectroscopy provides valuable information about the structure and supramolecular properties of the solid phase,which cannot be obtained from the solution phase.But so far,there are few reports on the measurement of solid chirality.This is because it is very difficult to measure the chirality of a solid using a commercial CD spectrometer.For general solid samples,in order to obtain true CD and circular birefringence(CB)spectra,we must remove parasitic artifacts from the observed spectrum,or design a very special technique to detect artifact-free signals.In this work,we have developed a circular dichroism(CD)imaging microscope,equipped with a device that suppresses the mixing of linear birefringence(LB)and linear dichroism(LD)signals.If irradiated with pure circularly polarized light,there is no linear polarization contribution,and the CD signal is not affected by the mixing of LD and LB in principle.The CD imaging method in this study can be widely used in medical and biological research.This imaging technique can help identify the chirality of chromatin structures in biological cells.Discretely modulated CD microscopic imaging system can focus microscopic imaging in a small range,eliminate artifact signals,and perform single-particle measurement.This topic uses the Muller matrix method to analyze the physical meaning and artifact sources of the measured signals in the traditional polarization modulation method,and then develops a CD microscope that can be used for solid materials based on a new polarization modulation method combined with scanning microscopy imaging technology Imaging system.This topic uses Jones matrix to compare the output signal of the circular polarization modulated imaging system with the signal modulated by the traditional photoelastic modulator.It is found that the final output signal of the circular dichroic spectrometer based on the photoelastic modulator is in addition to the CD and LD signal we want to measure,there are also coupling items related to the linear polarization component.However,the final output signals of the circular dichromatic microscopic imaging system based on discrete modulation are only CD and LD signals that we want to measure,and there is no artifact signal generation.This topic built a discrete modulation polarization modulation system by using chopper and beam displacer,and then through the continuous optimization of the optical system and the calibration of CD and LD signals,the scanning imaging of two-dimensional materials and chiral materials is improved.The system realizes the single particle measurement of spiral gold nanoparticles,which can accurately obtain the CD value and period of a single particle.