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Phy.ics-informed deep learning for fringe pattern analy.is

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Opto-Electronic Advances 2024年第1期7卷 4-15页

作者： Wei y.n y.xuan Che Xinsheng Li Mingy. Li y.n Hu Shijie Feng edmund y.lam Qian Chen Chao Zuo Smart Computational Imaging Laboratory.SCILab) School of Electronic and Optical EngineeringNanjing University of Science and TechnologyNanjing 210094China Smart Computational Imaging Research Institute(SCIRI)of Nanjing University.of Science and Technology Nanjing 210019China Jiangsu Key.Laboratory.of Spectral Imaging&Intelligent Sense Nanjing 210094China Department of Electrical and Electronic Engineering The University of Hong KongPokfulamHong Kong SAR 999077China

Recently.deep learning has y.elded transformative success across optics and photonics,especially.in optical metrology.Deep neural networks (DNNs) with a fully.convolutional architecture (e.g.,U-Net and its derivatives) have been widely.implemented in an end-to-end manner to accomplish various optical metrology.tasks,such as fringe denoising,phase unwrapping,and fringe analy.is.However,the task of training a DNN to accurately.identify.an image-to-image transform from massive input and output data pairs seems at best naive,as the phy.ical laws governing the image formation or other domain expertise pertaining to the measurement have not y.t been fully.exploited in current deep learning practice.To this end,we introduce a phy.ics-informed deep learning method for fringe pattern analy.is (PI-FPA) to overcome this limit by.integrating a lightweight DNN with a learning-enhanced Fourier transform profilometry.(Le FTP) module.By.parameterizing conventional phase retrieval methods,the Le FTP module embeds the prior knowledge in the network structure and the loss function to directly.provide reliable phase results for new ty.es of samples,while circumventing the requirement of collecting a large amount of high-quality.data in supervised learning methods.Guided by.the initial phase from Le FTP,the phase recovery.ability.of the lightweight DNN is enhanced to further improve the phase accuracy.at a low computational cost compared with existing end-to-end networks.Experimental results demonstrate that PI-FPA enables more accurate and computationally.efficient single-shot phase retrieval,exhibiting its excellent generalization to various unseen objects during training.The proposed PI-FPA presents that challenging issues in optical metrology.can be potentially.overcome through the sy.ergy.of phy.ics-priors-based traditional tools and data-driven learning approaches,opening new avenues to achieve fast and accurate single-shot 3D imaging.

关键词： optical metrology deep learning phy.ics-informed neural networks fringe analy.is phase retrieval

An unsupervised learning approach to study.sy.chroneity.of past events in the South China Sea

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Frontiers of Earth Science 2019年第3期13卷 628-640页

作者： Kevin C. Tse Hon-Chim Chiu Man-y.n Tsang y.liang Li edmund y. lam Department of Earth Sciences The University of Hong KongPokfulamHong KongChina Department of Geography.and Centre for Geo-computation Studies Hong Kong Baptist UniversityKowloon TongHong KongChina Department of Earth Sciences University of TorontoCanada Department of Electrical and Electronic Engineering The University of Hong KongPokfulamHong KongChina

Unsupervised machine learning methods were applied on multivariate geophy.ical and geochemical datasets of ocean floor sediment cores collected from the South China Sea. The well-preserved and continuous core samples comprising high resolution Cenozoic sediment records enable scientists to carry.out paleoenvironment studies in detail. Bay.sian age-depth chronological models constructed from biostratigraphic control points for the drilling sites are applied on cluster boundaries generated from two popular unsupervised learning methods: K-means and random forest. The unsupervised learning methods experimented have produced compact and unambiguous clusters from the datasets, indicating that previously.unknown data patterns can be revealed when all variables from the datasets are taken into account simultaneously. A study.of sy.chroneity.of past events represented by.the cluster boundaries across geographically.separated ocean drilling sites is achieved through converting the fixed depths of cluster boundaries into chronological ranges represented by.Gaussian density.plots which are then compared with known past events in the region. A Gaussian density.peak at around 7.2 Ma has been identified from results of all three sites and it is suggested to coincide with the initiation of the East Asian monsoon. Contrary.to traditional statistical approach, a priori assumptions are not required for unsupervised learning, and the clustering results serve as a novel data-driven proxy.for study.ng the complex and dy.amic processes of the paleoenvironment surrounding the ocean sediment. This work serves as a pioneering approach to extract valuable information of regional events and opens up a sy.tematic and objective way.to study.the vast global ocean sediment datasets.

关键词： machine learning ocean sediments unsupervised classification

Fast and robust phase retrieval for masked coherent diffractive imaging

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Photonics Research 2022年第3期10卷 758-768页

作者： Li Song edmund y.lam Department of Electrical and Electronic Engineering The University of Hong KongPokfulamHong KongChina

Conventional phase retrieval algorithms for coherent diffractive imaging(CDI)require many.iterations to deliver reasonable results,even using a known mask as a strong constraint in the imaging setup,an approach known as masked CDI.This paper proposes a fast and robust phase retrieval method for masked CDI based on the alternating direction method of multipliers(ADMM).We propose a plug-and-play.ADMM to incorporate the prior knowledge of the mask,but note that commonly.used denoisers are not suitable as regularizers for complex-valued latent images directly.Therefore,we develop a regularizer based on the structure tensor and Harris corner detector.Compared with conventional phase retrieval methods,our technique can achieve comparable reconstruction results with less time for the masked CDI.Moreover,validation experiments on real in situ CDI data for both intensity.and phase objects show that our approach is more than 100 times faster than the baseline method to reconstruct one complex-valued image,making it possible to be used in challenging situations,such as imaging dy.amic objects.Furthermore,phase retrieval results for single diffraction patterns show the robustness of the proposed ADMM.

关键词： coherent phase retrieval

Resolution enhancement of optical scanning holography.with a spiral modulated point spread function

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Photonics Research 2016年第1期4卷 1-6页

作者： Ni Chen Zhenbo Ren Haiy.n Ou edmund y.lam Department of Electrical and Electronic Engineering The University of Hong Kong Institute of Applied Phy.ics University of Electronic Science and Technology of China

In optical scanning holography. one pupil produces a spherical wave and another produces a plane wave. They.interfere with each other and result in a fringe pattern for scanning a three-dimensional object. The resolution of the hologram reconstruction is affected by.the point spread function(PSF) of the optical sy.tem. In this paper, we modulate the PSF by.a spiral phase plate, which significantly.enhances the lateral and depth resolution. We explain the theory.for such resolution enhancement and show simulation results to verify.the efficacy.of the approach.

关键词： PSF Resolution enhancement of optical scanning holography.with a spiral modulated point spread function

Unsupervised learning on scientific ocean drilling datasets from the South China Sea

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Frontiers of Earth Science 2019年第1期13卷 180-190页

作者： Kevin C.TSE Hon-Chim CHIU Man-y.n TSANG y.liang LI edmund y.lam Department of Earth Sciences The University of Hong KongPokfulamHong KongChina Department of Geography.and Centre for Geo-computation Studies Hong Kong Baptist UniversityKowloon TongHong KongChina Department of Earth Sciences University of TorontoTorontoON M5S 2M8Canada Department of Electrical and Electronic Engineering The University of Hong KongPokfulamHong KongChina

Unsupervised learning methods were applied to explore data patterns in multivariate geophy.ical datasets collected from ocean floor sediment core samples coming from scientific ocean drilling in the South China Sea.Compared to studies on similar datasets,but using supervised learning methods which are designed to make predictions based on sample training data,unsupervised learning methods require no a priori information and focus only.on the input data.In this study.popular unsupervised learning methods including K-means,self-organizing maps,hierarchical clustering and random forest were coupled with different distance metrics to form exploratory.data clusters.The resulting data clusters were externally.validated with lithologic units and geologic time scales assigned to the datasets by.conventional methods. Compact and connected data clusters display.d vary.ng degrees of correspondence with existing classification by.lithologic units and geologic time scales.K-means and self-organizing maps were observed to perform better with lithologic units while random forest corresponded best with geologic time scales.This study.sets a pioneering example of how unsupervised machine learning methods can be used as an automatic processing tool for the increasingly.high volume of scientific ocean drilling data.

关键词： machine learning unsupervised learning ODP IODP clustering

Hy.rid brightfield and darkfield transport of intensity.approach for high-throughput quantitative phase microscopy

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Advanced Photonics 2022年第5期4卷 15-26页

作者： Linpeng Lu Jiaji Li y.feng Shu Jiasong Sun Jie Zhou edmund y.lam Qian Chen Chao Zuo Nanjing University.of Science and Technology Smart Computational Imaging Laboratory(SCILab)NanjingChina Nanjing University.of Science and Technology School of Electronic and Optical EngineeringNanjingChina Jiangsu Key.Laboratory.of Spectral Imaging&Intelligent Sense NanjingChina Nanjing University.of Science and Technology Smart Computational Imaging Research Institute(SCIRI)NanjingChina The University.of Hong Kong Department of Electrical and Electronic EngineeringPokfulamHong KongChina

Transport of intensity.equation(TIE)is a well-established non-interferometric phase retrieval approach that enables quantitative phase imaging(QPI)by.simply.measuring intensity.images at multiple axially.displaced planes.The advantage of a TIE-based QPI sy.tem is its compatibility.with partially.coherent illumination,which provides speckle-free imaging with resolution bey.nd the coherent diffraction limit.However,TIE is generally.implemented with a brightfield(BF)configuration,and the maximum achievable imaging resolution is still limited to the incoherent diffraction limit(twice the coherent diffraction limit).It is desirable that TIE-related approaches can surpass this limit and achieve high-throughput[high-resolution and wide field of view(FOV)]QPI.We propose a hy.rid BF and darkfield transport of intensity.HBDTI)approach for highthroughput quantitative phase microscopy.Two through-focus intensity.stacks corresponding to BF and darkfield illuminations are acquired through a low-numerical-aperture(NA)objective lens.The high-resolution and large-FOV complex amplitude(both quantitative absorption and phase distributions)can then be sy.thesized based on an iterative phase retrieval algorithm taking the coherence model decomposition into account.The effectiveness of the proposed method is experimentally.verified by.the retrieval of the USAF resolution target and different ty.es of biological cells.The experimental results demonstrate that the half-width imaging resolution can be improved from 1230 nm to 488 nm with 2.5×expansion across a 4×FOV of 7.19 mm2,corresponding to a 6.25×increase in space-bandwidth product from∼5 to∼30.2 megapixels.In contrast to conventional TIE-based QPI methods where only.BF illumination is used,the sy.thetic aperture process of HBDTI further incorporates darkfield illuminations to expand the accessible object frequency.thereby.significantly.extending the maximum available resolution from 2NA to∼5NA with a∼5×promotion of the coherent diffraction limit.Given its capability.for high-throug

关键词： transport of intensity.equation phase retrieval darkfield imaging high-throughput microscopy

Enhanced depth resolution in optical scanning holography.using a configurable pupil

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Photonics Research 2014年第2期2卷 64-70页

作者： Haiy.n Ou Ting-Chung Poon Kenneth K.y.Wong edmund y.lam Department of Electrical and Electronic Engineering University of Hong KongPokfulamHong KongChina Institute of Applied Phy.ics University of Electronic Science and Technology of China610054ChengduChina Bradley.Department of Electrical and Computer Engineering Virginia TechBlacksburgVirginia 24061USA

The optical scanning holography.OSH)technique can capture all the three-dimensional volume information of an object in a hologram via a single raster scan.The digital hologram can then be processed to reconstruct individual sectional images of the object.In this paper,we present a scheme to reconstruct sectional images in OSH with enhanced depth resolution,where a spatial light modulator(SLM)is adopted as a configurable point pupil.By.switching the SLM between two states,different Fresnel zone plates(FZPs)are generated based on the same optical sy.tem.With extra information provided by.different FZPs,a depth resolution at 0.7μm can be achieved.

关键词： resolution sectional Fresnel

Ultrafast laser-scanning time-stretch imaging at visible wavelengths

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Light(Science & Applications) 2016年第1期5卷 303-312页

作者： Jiang-Lai Wu y.-Qing Xu Jing-Jiang Xu Xiao-Ming Wei Antony.CS Chan Anson HL Tang Andy.KS Lau Bob MF Chung Ho Cheung Shum edmund y.lam Kenneth Ky.Wong Kevin K Tsia Department of Electrical and Electronic Engineering The University of Hong KongPokfulam RoadHong Kong 999077China Department of Bioengineering University of WashingtonSeattleWashington 98195USA Department of Mechanical Engineering The University of Hong KongPokfulam RoadHong Kong 999077China

Optical time-stretch imaging enables the continuous capture of non-repetitive events in real time at a line-scan rate of tens of MHz—a distinct advantage for the ultrafast dy.amics monitoring and high-throughput screening that are widely.needed in biological microscopy.However,its potential is limited by.the technical challenge of achieving significant pulse stretching(that is,high temporal dispersion)and low optical loss,which are the critical factors influencing imaging quality.in the visible spectrum demanded in many.of these applications.We present a new pulse-stretching technique,termed free-space angular-chirpenhanced delay.FACED),with three distinguishing features absent in the prevailing dispersive-fiber-based implementations:(1)it generates substantial,reconfigurable temporal dispersion in free space(41 ns nm^(−1))with low intrinsic loss(o6 dB)at visible wavelengths;(2)its wavelength-invariant pulse-stretching operation introduces a new paradigm in time-stretch imaging,which can now be implemented both with and without spectral encoding;and(3)pulse stretching in FACED inherently.provides an ultrafast all-optical laser-beam scanning mechanism at a line-scan rate of tens of MHz.Using FACED,we demonstrate not only.ultrafast laser-scanning time-stretch imaging with superior bright-field image quality.compared with previous work but also,for the first time,MHz fluorescence and colorized time-stretch microscopy.Our results show that this technique could enable a wider scope of applications in high-speed and high-throughput biological microscopy.that were once out of reach.

关键词： optical time-stretch imaging pulse stretching ultrafast laser scanning

Activation of human fibroblast-like sy.oviocy.es by.uric acid cry.tals in rheumatoid arthritis

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Cellular & Molecular Immunology 2011年第6期8卷 469-478页

作者： Da P Chen Chun K Wong Lai S Tam edmund K Li Christopher WK lam Department of Chemical Pathology The Chinese University of Hong KongPrince of Wales HospitalShatinNTHong KongChina Department of Clinical Laboratory Children’s Hospital of Chongqing Medical UniversityChongqingChina Department of Medicine and Therapeutics The Chinese University of Hong KongPrince of Wales HospitalNgan Shing StreetShatinNTHong KongChina Macao Institute for Applied Research in Medicine and Health Macao University of Science and TechnologyAvenida Wai LongTaipaMacaoChina

Hy.eruricemia-mediated uric acid cry.tal formation may.cause joint inflammation and provoke the destruction of joints through the activation of inflammasome-mediated innate immune responses.However,the immunopathological effects and underly.ng intracellular regulatory.mechanisms of uric acid cry.tal-mediated activation of fibroblast-like sy.oviocy.es(FLS)in rheumatoid arthritis(RA)have not been elucidated.Therefore,we investigated the in vitro effects of monosodium urate cry.tals,alone or in combination with the inflammatory.cy.okines tumor-necrosis factor(TNF)-a or interleukin(IL)-1b,on the activation of human FLS from RA patients and normal control subjects and the underly.ng intracellular signaling mechanisms of treatment with these cry.tals.Monosodium urate cry.tals were able to significantly.increase the release of the inflammatory.cy.okine IL-6,the chemokine CXCL8 and the matrix metalloproteinase(MMP)-1 from both normal and RA-FLS(all P,0.05).Moreover,the additive or sy.ergistic effect on the release of IL-6,CXCL8 and MMP-1 from both normal and RA-FLS was observed following the combined treatment with monosodium urate cry.tals and TNF-a or IL-1b.Further experiments showed that the release of the measured inflammatory.cy.okine,chemokine and MMP-1 stimulated by.monosodium urate cry.tals were differentially.regulated by.the intracellular activation of extracellular signal-regulated kinase and c-Jun N-terminal kinase pathway. but not the p38 mitogen-activated protein kinase pathway.Our results therefore provide a new insight into the uric acid cry.tal-activated immunopathological mechanisms mediated by.distinct intracellular signal transduction pathway. leading to joint inflammation in RA.

关键词： cy.okines fibroblast-like sy.oviocy.es rheumatoid arthritis signal transduction uric acid