Quantitative Phase Microscopy Based On Quadriwave Lateral Shearing Interferometry And Its Application

Quantitative phase microscopy(QPM)is a novel microscopic imaging technology,which can realize the quantitative measurement of the phase information of the object.It has the characteristics of non-contact,label-free and three-dimensional imaging and has been widely used in biomedical imaging,micro-morphology measurement and other fields.Compared with other common types of QPM,QPM based on quadriwave lateral shearing interferometry(QWLSI)has the advantages of no reference beam,simple configuration,high stability and fast imaging speed and so on.In this paper,the chessboard phase grating is used to realize quantitative phase imaging based on QWLSI.The influence of grating period and illumination wavelength on QWLSI is analyzed theoretically,the optimal matching relation between grating period and pixel size of detector is obtained,and the feasibility of quantitative phase imaging under the illumination of wide-spectrum source.A stable,practical and convenient quantitative phase microscopic observation device is constructed to measure the quantitative phase of microscopic samples.The refractive index decoupling method for three wavelength illumination quantitative phase imaging is proposed,and the feasibility of the method is verified by simulation and experimental results.The majority of research work are outlined as below:1.The principle of quadriwave lateral shearing interference recording and wavefront reconstruction is studied theoretically.The characteristics of cross grating,modified hartmann mask and chessboard phase grating is analyzed,and the following results are obtained: the cross grating has low energy utilization and diffraction efficiency,and needs to combine with the order selection mask to realize QWLSI with high adjustment accuracy;the modified hartmann mask can concentrate more than 80% of the diffraction energy on four first-order diffraction beams without order selection mask,but 5/9 of the incident energy is lost;the chessboard phase grating can concentrate over 65% of the incident energy in four first-order diffraction beams without loss of the incident energy.Finally,we choose the chessboard phase grating as the beam splitting element.The influence of grating period and illumination wavelength on shearing interference imaging is theoretically analyzed,and the optimal matching relation of grating period is 6times of the pixel size of detector is determined.It is concluded that the method is independent of illumination wavelength and can be illuminated by a wide-spectrum light source.2.A quantitative phase microscopic imaging setup based on QWLSI is constructed.The quantitative phase imaging of microlens array,polymethyl methacrylate(PMMA)beads and staphylococcus was achieved by using laser and wide-spectrum light source respectively,and the quantitative phase microscopic imaging performance of the system was verified.The experimental results show that the phase measurement error of the system is 1.8%,and the optical path difference fluctuation within 30 minutes is less than 1.88 nm.3.A refractive index decoupling method based on triple-wavelength illumination quantitative phase imaging is proposed.The quantitative phase distributions of the sample at three different wavelengths are obtained by using the quadriwave lateral shearing interferometer firstly,and then the thickness and refractive index of the measured sample can be calculated simultaneously with the help of Cauchy dispersion formula.No needs of special highly dispersive medium,additional assistant technology and manual operation did anymore as the existed methods.Both the simulation and the experimental results demonstrate the effectiveness and feasibility of the proposed method,and the refractive index measurement accuracy is better than 0.001.By using this method,microbeads with different materials are successful identified,which provides a new method and tool for optical material detection and material identification.