Matthieu Piniard, B. Sorrente, Gilles Hug, P. Picart
Over the past two decades, laser beam melting has emerged as the leading metal additive manufacturing process for producing small- and medium-size structures. However, a key obstacle for the application of this technique in industry is the lack of reliability and qualification mainly because of melt pool instabilities during the laser-powder interaction, which degrade the quality of the manufactured components. In this paper, we propose multiwavelength digital holography as a proof of concept for in situ real-time investigation of the melt pool morphology. A two-wavelength digital holographic setup was co-axially implemented in a laser beam melting facility. The solidified aluminum tracks and melt pools during the manufacturing of 316L were obtained with full-field one-shot acquisitions at short exposure times and various scanning velocities. The evaluation of the complex coherence factor of digital holograms allowed the quality assessment of the phase reconstruction. The motion blur was analyzed by scanning the dynamic melt pool.
{"title":"Melt pool monitoring in laser beam melting with two-wavelength holographic imaging","authors":"Matthieu Piniard, B. Sorrente, Gilles Hug, P. Picart","doi":"10.37188/lam.2022.011","DOIUrl":"https://doi.org/10.37188/lam.2022.011","url":null,"abstract":"Over the past two decades, laser beam melting has emerged as the leading metal additive manufacturing process for producing small- and medium-size structures. However, a key obstacle for the application of this technique in industry is the lack of reliability and qualification mainly because of melt pool instabilities during the laser-powder interaction, which degrade the quality of the manufactured components. In this paper, we propose multiwavelength digital holography as a proof of concept for in situ real-time investigation of the melt pool morphology. A two-wavelength digital holographic setup was co-axially implemented in a laser beam melting facility. The solidified aluminum tracks and melt pools during the manufacturing of 316L were obtained with full-field one-shot acquisitions at short exposure times and various scanning velocities. The evaluation of the complex coherence factor of digital holograms allowed the quality assessment of the phase reconstruction. The motion blur was analyzed by scanning the dynamic melt pool.","PeriodicalId":56519,"journal":{"name":"光:先进制造(英文)","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69983485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Parallax limitations in digital holography: a phase space approach","authors":"U. Schnars, C. Falldorf","doi":"10.37188/lam.2022.028","DOIUrl":"https://doi.org/10.37188/lam.2022.028","url":null,"abstract":"","PeriodicalId":56519,"journal":{"name":"光:先进制造(英文)","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69983519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shiyi Luan, Fei Peng, Guoxing Zheng, Chengqun Gui, Yi Song, and Sheng Liu
{"title":"High-speed, large-area and high-precision fabrication of aspheric micro-lens array based on 12-bit direct laser writing lithography","authors":"Shiyi Luan, Fei Peng, Guoxing Zheng, Chengqun Gui, Yi Song, and Sheng Liu","doi":"10.37188/lam.2022.047","DOIUrl":"https://doi.org/10.37188/lam.2022.047","url":null,"abstract":"","PeriodicalId":56519,"journal":{"name":"光:先进制造(英文)","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69983996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Pahl, Lucie Hüser, Sebastian Hagemeier, P. Lehmann
To improve the lateral resolution in microscopic imaging, microspheres are placed close to the object’ s surface in order to support the imaging process by optical near-field information. Although microsphere-assisted measurements are part of various recent studies, no generally accepted explanation for the effect of microspheres exists. Photonic nanojets, enhancement of the numerical aperture, whispering-gallery modes and evanescent waves are usually named reasons in context with microspheres, though none of these effects is proven to be decisive for the resolution enhancement. We present a simulation model of the complete microscopic imaging process of microsphere-enhanced interference microscopy including a rigorous treatment of the light scattering process at the surface of the specimen. The model consideres objective lenses of high numerical aperture providing 3D conical illumination and imaging. The enhanced resolution and magnification by the microsphere is analyzed with respect to the numerical aperture of the objective lenses. Further, we give a criterion for the achievable resolution and demonstrate that a local enhancement of the numerical aperture is the most likely reason for the resolution enhancement.
{"title":"FEM-based modeling of microsphere-enhanced interferometry","authors":"T. Pahl, Lucie Hüser, Sebastian Hagemeier, P. Lehmann","doi":"10.37188/lam.2022.049","DOIUrl":"https://doi.org/10.37188/lam.2022.049","url":null,"abstract":"To improve the lateral resolution in microscopic imaging, microspheres are placed close to the object’ s surface in order to support the imaging process by optical near-field information. Although microsphere-assisted measurements are part of various recent studies, no generally accepted explanation for the effect of microspheres exists. Photonic nanojets, enhancement of the numerical aperture, whispering-gallery modes and evanescent waves are usually named reasons in context with microspheres, though none of these effects is proven to be decisive for the resolution enhancement. We present a simulation model of the complete microscopic imaging process of microsphere-enhanced interference microscopy including a rigorous treatment of the light scattering process at the surface of the specimen. The model consideres objective lenses of high numerical aperture providing 3D conical illumination and imaging. The enhanced resolution and magnification by the microsphere is analyzed with respect to the numerical aperture of the objective lenses. Further, we give a criterion for the achievable resolution and demonstrate that a local enhancement of the numerical aperture is the most likely reason for the resolution enhancement.","PeriodicalId":56519,"journal":{"name":"光:先进制造(英文)","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69984049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"55 Years of Holographic Non-Destructive Testing and Experimental Stress Analysis: Is there still Progress to be expected?","authors":"W. Osten, G. Pedrini","doi":"10.37188/lam.2022.008","DOIUrl":"https://doi.org/10.37188/lam.2022.008","url":null,"abstract":"","PeriodicalId":56519,"journal":{"name":"光:先进制造(英文)","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69983396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Three-dimensional (3D) printing, also known as additive manufacturing (AM), has undergone a phase of rapid development in the fabrication of customizable and high-precision parts. Thanks to the advancements in 3D printing technologies, it is now a reality to print cells, growth factors, and various biocompatible materials altogether into arbitrarily complex 3D scaffolds with high degree of structural and functional similarities to the native tissue environment. Additionally, with overpowering advantages in molding efficiency, resolution, and a wide selection of applicable materials, optical 3D printing methods have undoubtedly become the most suitable approach for scaffold fabrication in tissue engineering (TE). In this paper, we first provide a comprehensive and up-to-date review of current optical 3D printing methods for scaffold fabrication, including traditional extrusion-based processes, selective laser sintering, stereolithography, and two-photon polymerization etc. Specifically, we review the optical design, materials, and representative applications, followed by fabrication performance comparison. Important metrics include fabrication precision, rate, materials, and application scenarios. Finally, we summarize and compare the advantages and disadvantages of each technique to guide readers in the optics and TE communities to select the most fitting printing approach under different application scenarios.
{"title":"Advanced Optical Methods and Materials for Fabricating 3D Tissue Scaffolds","authors":"Xiaobo Li, Wanping Lu, Xiayi Xu, Yintao Wang, Shih-Chih Chen","doi":"10.37188/lam.2022.026","DOIUrl":"https://doi.org/10.37188/lam.2022.026","url":null,"abstract":"Three-dimensional (3D) printing, also known as additive manufacturing (AM), has undergone a phase of rapid development in the fabrication of customizable and high-precision parts. Thanks to the advancements in 3D printing technologies, it is now a reality to print cells, growth factors, and various biocompatible materials altogether into arbitrarily complex 3D scaffolds with high degree of structural and functional similarities to the native tissue environment. Additionally, with overpowering advantages in molding efficiency, resolution, and a wide selection of applicable materials, optical 3D printing methods have undoubtedly become the most suitable approach for scaffold fabrication in tissue engineering (TE). In this paper, we first provide a comprehensive and up-to-date review of current optical 3D printing methods for scaffold fabrication, including traditional extrusion-based processes, selective laser sintering, stereolithography, and two-photon polymerization etc. Specifically, we review the optical design, materials, and representative applications, followed by fabrication performance comparison. Important metrics include fabrication precision, rate, materials, and application scenarios. Finally, we summarize and compare the advantages and disadvantages of each technique to guide readers in the optics and TE communities to select the most fitting printing approach under different application scenarios.","PeriodicalId":56519,"journal":{"name":"光:先进制造(英文)","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69983425","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kaiyuan Zheng, Shoulin Jiang, Feifan Chen, Yan Zhao, Shou-fei Gao, Ying‐ying Wang, H. Ho, W. Jin
We report all-optical mid-infrared phase and intensity modulators based on the photo-thermal effect in an acetylene-filled anti-resonant hollow-core fiber. Optical absorption of the control beam promotes the gas molecules to a higher energy level, which induces localized heating through non-radiative relaxation and modulates the refractive index of the gas material and hence the accumulated phase of the signal beam propagating through the hollow-core fiber. By modulating the intensity of the control beam, the phase of the signal beam is modulated accordingly. By use of a 1.53 μm near-infrared control beam, all-optical phase modulation up to 2.2π rad is experimentally demonstrated at the signal wavelength of 3.35 μm. With the phase modulator placed in one arm of a Mach-Zehnder interferometer, intensity modulation with on-off ratio of 25 dB is achieved. The gas-filled hollow-core-fiber modulators could operate over an ultra-broad wavelength band from nearto midinfrared and have promising application in mid-infrared photonic systems.
{"title":"Mid-infrared all-optical modulators based on an acetylene-filled hollow-core fiber","authors":"Kaiyuan Zheng, Shoulin Jiang, Feifan Chen, Yan Zhao, Shou-fei Gao, Ying‐ying Wang, H. Ho, W. Jin","doi":"10.37188/lam.2022.050","DOIUrl":"https://doi.org/10.37188/lam.2022.050","url":null,"abstract":"We report all-optical mid-infrared phase and intensity modulators based on the photo-thermal effect in an acetylene-filled anti-resonant hollow-core fiber. Optical absorption of the control beam promotes the gas molecules to a higher energy level, which induces localized heating through non-radiative relaxation and modulates the refractive index of the gas material and hence the accumulated phase of the signal beam propagating through the hollow-core fiber. By modulating the intensity of the control beam, the phase of the signal beam is modulated accordingly. By use of a 1.53 μm near-infrared control beam, all-optical phase modulation up to 2.2π rad is experimentally demonstrated at the signal wavelength of 3.35 μm. With the phase modulator placed in one arm of a Mach-Zehnder interferometer, intensity modulation with on-off ratio of 25 dB is achieved. The gas-filled hollow-core-fiber modulators could operate over an ultra-broad wavelength band from nearto midinfrared and have promising application in mid-infrared photonic systems.","PeriodicalId":56519,"journal":{"name":"光:先进制造(英文)","volume":"171 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69984061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Since its invention, holography has been mostly applied at visible wavelengths in a variety of applications. Specifically, non-destructive testing of manufactured objects was a driver for developing holographic methods and all related ones based on the speckle pattern recording. One substantial limitation of holographic non-destructive testing is the setup stability requirements directly related to the laser wavelength. This observation has driven some works for 15 years: developing holography at wavelengths much longer than visible ones. In this paper, we will first review researches carried out in the infrared, mostly digital holography at thermal infrared wavelengths around 10 micrometers. We will discuss the advantages of using such wavelengths and show different examples of applications. In nondestructive testing, large wavelengths allow using digital holography in perturbed environments on large objects and measure large deformations, typical of the aerospace domain. Other astonishing applications such as reconstructing scenes through smoke and flames were proposed. When moving further in the spectrum, digital holography with so-called Terahertz waves (up to 3 millimeters wavelength) has also been studied. The main advantage here is that these waves easily penetrate some materials. Therefore, one can envisage Terahertz digital holography to reconstruct the amplitude and phase of visually opaque objects. We review some cases in which Terahertz digital holography has shown potential in biomedical and industrial applications. We will also address some fundamental bottlenecks that prevent fully benefiting from the advantages of digital holography when increasing the wavelength.
{"title":"Holography in the invisible. From the thermal infrared to the terahertz waves: outstanding applications and fundamental limits","authors":"M. Georges, Yuchen Zhao, J. Vandenrijt","doi":"10.37188/lam.2022.022","DOIUrl":"https://doi.org/10.37188/lam.2022.022","url":null,"abstract":"Since its invention, holography has been mostly applied at visible wavelengths in a variety of applications. Specifically, non-destructive testing of manufactured objects was a driver for developing holographic methods and all related ones based on the speckle pattern recording. One substantial limitation of holographic non-destructive testing is the setup stability requirements directly related to the laser wavelength. This observation has driven some works for 15 years: developing holography at wavelengths much longer than visible ones. In this paper, we will first review researches carried out in the infrared, mostly digital holography at thermal infrared wavelengths around 10 micrometers. We will discuss the advantages of using such wavelengths and show different examples of applications. In nondestructive testing, large wavelengths allow using digital holography in perturbed environments on large objects and measure large deformations, typical of the aerospace domain. Other astonishing applications such as reconstructing scenes through smoke and flames were proposed. When moving further in the spectrum, digital holography with so-called Terahertz waves (up to 3 millimeters wavelength) has also been studied. The main advantage here is that these waves easily penetrate some materials. Therefore, one can envisage Terahertz digital holography to reconstruct the amplitude and phase of visually opaque objects. We review some cases in which Terahertz digital holography has shown potential in biomedical and industrial applications. We will also address some fundamental bottlenecks that prevent fully benefiting from the advantages of digital holography when increasing the wavelength.","PeriodicalId":56519,"journal":{"name":"光:先进制造(英文)","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69983314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Holographic augmented reality display with conical holographic optical element for wide viewing zone","authors":"Y. Sando, Kazuo Satoh, D. Barada, T. Yatagai","doi":"10.37188/lam.2022.012","DOIUrl":"https://doi.org/10.37188/lam.2022.012","url":null,"abstract":"","PeriodicalId":56519,"journal":{"name":"光:先进制造(英文)","volume":"45 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69983502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Imaging through random media continues to be a challenging problem of crucial importance in a wide range of fields of science and technology, ranging from telescopic imaging through atmospheric turbulence in astronomy to microscopic imaging through scattering tissues in biology. To meet the scope of this anniversary issue in holography, this review places a special focus on holographic techniques and their unique functionality, which play a pivotal role in imaging through random media. This review comprises two parts. The first part is intended to be a mini tutorial in which we first identify the true nature of the problems encountered in imaging through random media. We then explain through a methodological analysis how unique functions of holography can be exploited to provide practical solutions to problems. The second part introduces specific examples of experimental implementations for different principles of holographic techniques, along with their performance results, which were taken from some of our recent work.
{"title":"Holographic 3D Imaging through Random Media: Methodologies and Challenges","authors":"Mitsuo Takeda, W. Osten, E. Watanabe","doi":"10.37188/lam.2022.014","DOIUrl":"https://doi.org/10.37188/lam.2022.014","url":null,"abstract":"Imaging through random media continues to be a challenging problem of crucial importance in a wide range of fields of science and technology, ranging from telescopic imaging through atmospheric turbulence in astronomy to microscopic imaging through scattering tissues in biology. To meet the scope of this anniversary issue in holography, this review places a special focus on holographic techniques and their unique functionality, which play a pivotal role in imaging through random media. This review comprises two parts. The first part is intended to be a mini tutorial in which we first identify the true nature of the problems encountered in imaging through random media. We then explain through a methodological analysis how unique functions of holography can be exploited to provide practical solutions to problems. The second part introduces specific examples of experimental implementations for different principles of holographic techniques, along with their performance results, which were taken from some of our recent work.","PeriodicalId":56519,"journal":{"name":"光:先进制造(英文)","volume":"36 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69983556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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