Li Chen

Guangdong University of Technology

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Yihua Hu

Guangdong University of Technology

Ziyang Chen

Northwestern Polytechnical University

Kunhua Wen

Guangdong University of Technology

Jiaqi Xiao

Shandong Academy of Sciences

Wenyang Cai

Guangdong University of Technology

Jixiong Pu

Huaqiao University

Rakesh Kumar Singh

Banaras Hindu University

Weitao Lin

Fuzhou University

Kai Chen

University of Otago

Jixiong Pu

Huaqiao University

Cooperative Institutions

South China Normal University

Chinese Academy of Sciences

Guangdong University of Technology

Huaqiao University

Huazhong University of Science and Technology

University of Chinese Academy of Sciences

Wuhan National Laboratory for Optoelectronics

Chongqing University

Sun Yat-sen University

Beijing Institute of Technology

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Speckle reduction in digital holography with low-dimensional reconstruction

Applied Optics (2021)

Weitao Lin Li Chen Wenyang Cai Yihua Hu Kunhua Wen

Speckle reduction is a crucial technique since the presence of speckle disturbs the quality of the reconstruction in digital holography. In this paper, we present an easy, fast, and efficient single-shot method to reduce speckle noise in digital holography. The method reconstructs subholograms from a single hologram. Then, sub-reconstruction images are randomly shuffled and divided into several groups and low-dimensional noise-reduced images can be achieved by averaging sub-reconstruction image groups by groups. Next, these low-dimensional noise-reduced images are combined to obtain a noise-reduced image. Finally, the noise-reduced image is processed by a mean filter to obtain a final image, which has substantially less speckle noise while preserving the dimensions of the original image. The experimental results demonstrate the effectiveness of the proposed method and indicate its potential in real-time digital holography.

Speckle noise

Digital holography

Digital Holographic Microscopy

Image noise

10.1364/ao.414773

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Citations (3)

Measurement of Charge and Refractive Indices in Optically Trapped and Ionized Living Cells

Tomography (2022)

Endris Muhammed Daniel Erenso Ying Gao Li Chen Michele Kelley

The post-ionization dynamics of chemo-treated and untreated 4T1 breast cancer cells ionized by laser trapping techniques are studied. We have determined each cell’s charge and refractive index by developing a theoretical model for the forces determining the post-ionization dynamics. The shift in a cell’s refractive index due to an intense oscillating electric field was studied, and the results are reported here. We observed that a trapped cell, as it becomes charged, will eventually exit the trap perpendicular to the beam’s direction; this means that the electric force of the cell overcomes the trapping force. As a result, the cell’s conductivity changes due to the oscillating field, causing a decrease in the cell’s refractive index.

10.3390/tomography9010007

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Citations (2)

Label-free hematology analysis method based on defocusing phase-contrast imaging under illumination of 415 nm light

Biomedical Optics Express (2022)

Duan Chen Ning Li Xiuli Liu Shaoqun Zeng Xiaohua Lv

Label-free imaging technology is a trending way to simplify and improve conventional hematology analysis by bypassing lengthy and laborious staining procedures. However, the existing methods do not well balance system complexity, data acquisition efficiency, and data analysis accuracy, which severely impedes their clinical translation. Here, we propose defocusing phase-contrast imaging under the illumination of 415 nm light to realize label-free hematology analysis. We have verified that the subcellular morphology of blood components can be visualized without complex staining due to the factor that defocusing can convert the second-order derivative distribution of samples' optical phase into intensity and the illumination of 415 nm light can significantly enhance the contrast. It is demonstrated that the defocusing phase-contrast images for the five leucocyte subtypes can be automatically discriminated by a trained deep-learning program with high accuracy (the mean F1 score: 0.986 and mean average precision: 0.980). Since this technique is based on a regular microscope, it simultaneously realizes low system complexity and high data acquisition efficiency with remarkable quantitative analysis ability. It supplies a label-free, reliable, easy-to-use, fast approach to simplifying and reforming the conventional way of hematology analysis.

Hematology

10.1364/boe.466162

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Citations (4)

High-accuracy mode recognition method in orbital angular momentum optical communication system

Chinese Optics Letters (2021)

Lin Zhao Yuan Hao Li Chen Wenyi Liu Meng Jin

Vortex optical communication has been a hot research field in recent years. A key step is mode recognition in the orbital angular momentum (OAM) free-space optical (FSO) communication system. In this article, we propose an OAM mode recognition method based on image recognition technology, which uses the interferogram between the vortex beam and the Gaussian beam to identify the OAM mode. In order to resist the influence of atmospheric turbulence on the recognition accuracy, we added a Gaussian smoothing filter into the recognition process. Moreover, we used random phase screens to generate interferogram sets at distances of 1 km and 2 km. The verification result shows that the proposed scheme produces high identification accuracy for the distorted optical field. The average accuracy can reach 100% and 87.78% under the conditions of medium- and strong-turbulence levels, respectively. It is anticipated that these results might be helpful for improving the reliability of the OAM-FSO communication system in the future.

Free-Space Optical Communication

Mode (computer interface)

Optical vortex

Gaussian filter

Gaussian beam

Smoothing

10.3788/col202220.020601

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Citations (14)

Single-shot speckle reduction by elimination of redundant speckle patterns in digital holography

Applied Optics (2020)

Weitao Lin Li Chen Yonghao Chen Wenyang Cai Yihua Hu

Speckle reduction is a crucial technique, since the presence of speckle disturbs the quality of the reconstruction in digital holography. In this paper, we present a redundant speckle elimination method to suppress the speckle noise. For the same position in each of the reconstructed sub-images, we consider pixels with the same gray value as information with the same speckle distribution. Therefore, a speckle-suppressed gray value can be obtained by extracting pixels with different gray values and then averaging. Through theoretical analysis and experiments, we demonstrate that speckle contrast can be decreased significantly by using the proposed method. Moreover, we show that the despeckle strength of the proposed method highly depends on the number of binary masks. These results indicate the potential of the proposed method for various applications.

Speckle noise

Digital holography

Speckle imaging

10.1364/ao.390500

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Citations (8)

Speckle reduction in digital holography with non-local means filter based on the Pearson correlation coefficient and Butterworth filter

Optics Letters (2021)

Kai Chen Li Chen Xiao Jia-qi Jinyang Li Yihua Hu

This Letter presents a non-local means filter based on the Pearson correlation coefficient and Butterworth high-pass filter. In the method, the new gray value of the denoising pixel is equal to the weighted sum of the surrounding pixel values. We use the Pearson correlation coefficient between the pixels to calculate the weight of the surrounding pixels to the denoising pixel, then use Butterworth high-pass filter to optimize. Experimental results show that the method effectively reduces the speckle noise of digital holography and the image details are also very rich. At the same time, its performance is still better when compared with methods such as BM3D.

Butterworth filter

Non-Local Means

Speckle noise

10.1364/ol.444769

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Citations (11)

A Study on Real Time Estimation Viability of Cells Based on DIC

IEEE/ICME International Conference on Complex Medical Engineering (2007)

Jianwen Xiong Li Chen Hua Xiao Zhenxi Zhang

Based on the morphological differences between normal, apoptosis and necrosis cell, a method on real time estimation viability of cells based on DIC(differential interference contrast) microscopy is presented in the paper. The Jurkat cell samples were used for investigation the relationship between morphological parameters and cell viabilities in the paper. According to the scatter charts of Jurkat cell roundness, radius ratio and area, the cell areas were mainly distributed from 40 μm ² to 80 μm ² . And the areas of apoptosis and necrosis cell were distributed in other range, i.e. larger areas or fewer areas. Not any chemical medicaments need to add in the samples by the method presented in the paper in order to get the viability of cells. The survival rate of Jurkat cells and the percentages of death cells in different death modes after ALA-PDT was estimated by the method presented in the paper. The experiment results showed that not only the results of survival rate of Jurkat cells estimated by the method presented in the paper were consistent with the results estimated by accepted MTT method, but also the percentages of death cells in different death modes can be got on real time by the method presented in the paper.

Jurkat cells

Viability assay

10.1109/iccme.2007.4381908

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Generation of a sub-diffraction hollow ring by shaping an azimuthally polarized wave

Scientific Reports (2016)

Gang Chen Zhixiang Wu Anping Yu Zhihai Zhang Zhongquan Wen

Abstract The generation of a sub-diffraction optical hollow ring is of great interest in various applications, such as optical microscopy, optical tweezers, and nanolithography. Azimuthally polarized light is a good candidate for creating an optical hollow ring structure. Various of methods have been proposed theoretically for generation of sub-wavelength hollow ring by focusing azimuthally polarized light, but without experimental demonstrations, especially for sub-diffraction focusing. Super-oscillation is a promising approach for shaping sub-diffraction optical focusing. In this paper, a planar sub-diffraction diffractive lens is proposed, which has an ultra-long focal length of 600 λ and small numerical aperture of 0.64. A sub-diffraction hollow ring is experimentally created by shaping an azimuthally polarized wave. The full-width-at-half-maximum of the hollow ring is 0.61 λ, which is smaller than the lens diffraction limit 0.78 λ, and the observed largest sidelobe intensity is only 10% of the peak intensity.

10.1038/srep37776

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Citations (33)

Estimating topological charge of propagating vortex from single-shot non-imaged speckle

Chinese Optics Letters (2021)

Li Chen Rakesh Kumar Singh Aristide Dogariu Ziyang Chen Jixiong Pu

Encoding information using the topological charge of vortex beams has been proposed for optical communications. The conservation of the topological charge on propagation and the detection of the topological charge by a receiver are significant in these applications and have been well established in free-space. However, when vortex beams enter a diffuser, the wavefront is distorted, leading to a challenge in the conservation and detection of the topological charge. Here, we present a technique to measure the value of the topological charge of a vortex beam obscured in the randomly scattered light. The results of the numerical simulations and experiments are presented and are in good agreement. In particular, only a single-shot measurement is required to detect the topological charge of vortex beams, indicating that the method is applicable to a dynamic diffuser.

Optical vortex

Light beam

10.3788/col202119.022603

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Citations (9)

Elimination of abnormal phase fluctuation in digital holography

Applied Optics (2022)

Wenyang Cai Li Chen Jiaqi Xiao Jinyang Li Yihua Hu

In digital holography, the phase is most important, and the quality of the reconstructed phase determines the final reconstructed image effect. However, noise is inevitably introduced in the process of recording the hologram. For regions without object light, the phase has a random distribution, which affects the final phase quality. This kind of noise is called abnormal phase fluctuations in this paper. The correlation between amplitude and phase in digital holography is used to judge whether there is useful phase information. Through structural similarity and the light-dark relationship, a credible probability mask is introduced to extract the phase that needs to be preserved. The simulation and experimental results show that abnormal phase fluctuations are successfully removed, and the useful phase information is retained.

Digital holography

Digital Holographic Microscopy

Similarity (geometry)

Ptychography

10.1364/ao.448986

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Citations (1)