Pub Date : 2024-10-16DOI: 10.1016/j.optlaseng.2024.108635
Zhuoran Xi , Yunong Sun , Huafan Zhang , Jianbin Liu , Hui Chen , Yu Zhou , Yuchen He , Huaibin Zheng , KuaiKuai Yu , Zhuo Xu , Yuan Yuan
Spectral imaging can obtain spatial and spectral information of an object and play an important role in many application scenarios. Computational spectral imaging through scattering media utilizes the spectrally sensitive properties of scattering media as a filter for spectral imaging. The spatial and spectral information are reconstructed simultaneously by deconvolution with point spread function (PSF). Invasive spectral imaging imposes stringent constraints on the measurement accuracy of PSF and application scenarios. Here, we demonstrate a non-invasive multispectral scattering imaging method via optical transfer function (OTF) retrieval. The method uses multi-frame speckles to non-invasively retrieve the OTF of imaging system. Similar to the spectral filter property of PSF in the space domain, OTF at different wavelengths can be employed to filter and reconstruct the multispectral information of mixed speckle in the frequency domain. Our method overcomes the need for invasive measurements and is applicable to a wide range of scenarios for static and dynamic objects, providing a new approach to multispectral imaging.
{"title":"Non-invasive multispectral scattering imaging via OTF retrieval","authors":"Zhuoran Xi , Yunong Sun , Huafan Zhang , Jianbin Liu , Hui Chen , Yu Zhou , Yuchen He , Huaibin Zheng , KuaiKuai Yu , Zhuo Xu , Yuan Yuan","doi":"10.1016/j.optlaseng.2024.108635","DOIUrl":"10.1016/j.optlaseng.2024.108635","url":null,"abstract":"<div><div>Spectral imaging can obtain spatial and spectral information of an object and play an important role in many application scenarios. Computational spectral imaging through scattering media utilizes the spectrally sensitive properties of scattering media as a filter for spectral imaging. The spatial and spectral information are reconstructed simultaneously by deconvolution with point spread function (PSF). Invasive spectral imaging imposes stringent constraints on the measurement accuracy of PSF and application scenarios. Here, we demonstrate a non-invasive multispectral scattering imaging method via optical transfer function (OTF) retrieval. The method uses multi-frame speckles to non-invasively retrieve the OTF of imaging system. Similar to the spectral filter property of PSF in the space domain, OTF at different wavelengths can be employed to filter and reconstruct the multispectral information of mixed speckle in the frequency domain. Our method overcomes the need for invasive measurements and is applicable to a wide range of scenarios for static and dynamic objects, providing a new approach to multispectral imaging.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"184 ","pages":"Article 108635"},"PeriodicalIF":3.5,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-16DOI: 10.1016/j.optlaseng.2024.108638
Hengli Feng , Hongyan Meng , Jia Liu , Xin Zhang , Shuang Yang , Hanmo Du , Yachen Gao
Terahertz refractive index (RI) sensor is an important tool for characterization of material properties. However, traditional immersion RI sensors suffer from issues of liquid contamination and low detection efficiency. Therefore, this study designs a non-contact multi-channel terahertz RI sensor based on metasurface which can produce vortex beam with focused orbital angular momentum (FOAM). Computing Spatially Weighted Variance (SWV) of the contours and intensities of the images resulting from different RI demonstrates that the RI value correlates uniquely with the weighted variance. Specifically, in the near-field metasurface (NF metasurface), by employing 3-bit phase binary (PB) encoding and convolution operations on vanadium dioxide (VO2) metasurfaces, we realized a high-purity FOAM with a focal length of f = 3500 μm. After fixing the sample under test at f = 3500 μm and analyzing the near-field FOAM amplitude images under various RI conditions using the SWV method, the RI detection sensitivity of the NF metasurface was calculated to be 15,775/RIU. To enhance detection efficiency and meet the requirements for far-field detection, we proposed a sensor capable of detecting multiple samples in the far-field. In the far-field metasurface (FF metasurface), when linearly polarized light is incident on this metasurface, the sensitivity of the FOAM to RI detection produced by this metasurface under the left circularly polarized (LCP) and right circularly polarized (RCP) components are 10,554/RIU and 13,292/RIU, respectively. The minimum change of the RI that can be detected by the near-field and far field sensors reaches 10−4 RIU. When VO2 transitions to its dielectric state, the metasurface switches to specular reflection, thereby endowing the sensor with switching functionality for RI detection. This approach overcomes issues of liquid-contaminated surfaces and enables simultaneous detection of multiple substances, offering broad application prospects across various sensing scenarios.
太赫兹折射率（RI）传感器是表征材料特性的重要工具。然而，传统的浸入式 RI 传感器存在液体污染和检测效率低的问题。因此，本研究设计了一种基于元表面的非接触式多通道太赫兹折射率传感器，它能产生具有聚焦轨道角动量（FOAM）的涡流束。计算不同 RI 产生的图像轮廓和强度的空间加权方差（SWV）表明，RI 值与加权方差具有独特的相关性。具体来说，在近场元表面（NF 元表面）中，通过对二氧化钒（VO2）元表面进行 3 位二进制相位（PB）编码和卷积操作，我们实现了焦距为 f = 3500 μm 的高纯度 FOAM。将被测样品固定在 f = 3500 μm 处，使用 SWV 方法分析各种 RI 条件下的近场 FOAM 幅值图像，计算出 NF 元表面的 RI 检测灵敏度为 15,775/RIU 。为了提高检测效率并满足远场检测的要求，我们提出了一种能够在远场检测多个样本的传感器。在远场元表面（FF 元表面）中，当线性偏振光入射到该元表面时，FOAM 对该元表面在左圆偏振（LCP）和右圆偏振（RCP）分量下产生的 RI 检测灵敏度分别为 10 554/RIU 和 13 292/RIU。近场和远场传感器能检测到的最小 RI 变化达到 10-4 RIU。当 VO2 转变为介电状态时，元表面就会转为镜面反射，从而赋予传感器检测 RI 的切换功能。这种方法克服了液体污染表面的问题，可同时检测多种物质，在各种传感场景中具有广阔的应用前景。
{"title":"Non-contact multi-channel terahertz refractive index detecting via focused orbital angular momentum","authors":"Hengli Feng , Hongyan Meng , Jia Liu , Xin Zhang , Shuang Yang , Hanmo Du , Yachen Gao","doi":"10.1016/j.optlaseng.2024.108638","DOIUrl":"10.1016/j.optlaseng.2024.108638","url":null,"abstract":"<div><div>Terahertz refractive index (RI) sensor is an important tool for characterization of material properties. However, traditional immersion RI sensors suffer from issues of liquid contamination and low detection efficiency. Therefore, this study designs a non-contact multi-channel terahertz RI sensor based on metasurface which can produce vortex beam with focused orbital angular momentum (FOAM). Computing Spatially Weighted Variance (SWV) of the contours and intensities of the images resulting from different RI demonstrates that the RI value correlates uniquely with the weighted variance. Specifically, in the near-field metasurface (NF metasurface), by employing 3-bit phase binary (PB) encoding and convolution operations on vanadium dioxide (VO<sub>2</sub>) metasurfaces, we realized a high-purity FOAM with a focal length of <em>f</em> = 3500 μm. After fixing the sample under test at <em>f</em> = 3500 μm and analyzing the near-field FOAM amplitude images under various RI conditions using the SWV method, the RI detection sensitivity of the NF metasurface was calculated to be 15,775/RIU. To enhance detection efficiency and meet the requirements for far-field detection, we proposed a sensor capable of detecting multiple samples in the far-field. In the far-field metasurface (FF metasurface), when linearly polarized light is incident on this metasurface, the sensitivity of the FOAM to RI detection produced by this metasurface under the left circularly polarized (LCP) and right circularly polarized (RCP) components are 10,554/RIU and 13,292/RIU, respectively. The minimum change of the RI that can be detected by the near-field and far field sensors reaches 10<sup>−4</sup> RIU. When VO<sub>2</sub> transitions to its dielectric state, the metasurface switches to specular reflection, thereby endowing the sensor with switching functionality for RI detection. This approach overcomes issues of liquid-contaminated surfaces and enables simultaneous detection of multiple substances, offering broad application prospects across various sensing scenarios.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"184 ","pages":"Article 108638"},"PeriodicalIF":3.5,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-16DOI: 10.1016/j.optlaseng.2024.108643
Dong Yang , Zhongming Yang , Yanfeng Zhang
Analyzing noncircular wavefront aberration require reconstructing orthonormal Zernike polynomials over noncircular pupils using Gram-Schmidt orthogonalization and nonrecursive matrix approach. However, these methods are computationally complex and time-consuming. We proposed a modal wavefront reconstruction method for noncircular pupils by Schwarz-Christoffel mapping and Zernike circle polynomials. Schwarz-Christoffel mapping is used to conformally transform the noncircular wavefront into a disk-shaped domain, enabling the mapped circular wavefronts to be fitted by Zernike circle polynomials. Experimental results demonstrate excellent agreement with measurements obtained from a commercial Fizeau interferometer. Furthermore, compared to the traditional orthonormal polynomials fitting method, the reconstruction accuracy of our method is higher than 90 %, and the time consuming is reduced by 2–5 times. This study presents a reliable modal wavefront reconstruction technique for noncircular pupils.
{"title":"Modal wavefront reconstruction by Schwarz-Christoffel mapping and Zernike circle polynomials for noncircular pupils","authors":"Dong Yang , Zhongming Yang , Yanfeng Zhang","doi":"10.1016/j.optlaseng.2024.108643","DOIUrl":"10.1016/j.optlaseng.2024.108643","url":null,"abstract":"<div><div>Analyzing noncircular wavefront aberration require reconstructing orthonormal Zernike polynomials over noncircular pupils using Gram-Schmidt orthogonalization and nonrecursive matrix approach. However, these methods are computationally complex and time-consuming. We proposed a modal wavefront reconstruction method for noncircular pupils by Schwarz-Christoffel mapping and Zernike circle polynomials. Schwarz-Christoffel mapping is used to conformally transform the noncircular wavefront into a disk-shaped domain, enabling the mapped circular wavefronts to be fitted by Zernike circle polynomials. Experimental results demonstrate excellent agreement with measurements obtained from a commercial Fizeau interferometer. Furthermore, compared to the traditional orthonormal polynomials fitting method, the reconstruction accuracy of our method is higher than 90 %, and the time consuming is reduced by 2–5 times. This study presents a reliable modal wavefront reconstruction technique for noncircular pupils.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"184 ","pages":"Article 108643"},"PeriodicalIF":3.5,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-16DOI: 10.1016/j.optlaseng.2024.108637
Yi Hou , Zhisong Li , Xin Tang
The development of optical systems requires high-precision inspection technology, which supports the manufacturing and integration of optical systems. Currently, the method commonly used for high-precision optical plane inspection is interferometry based on the reference plane, however, its inspection accuracy is constrained by the accuracy of the reference plane. Therefore, this paper proposes an absolute detection method based on multi-signal phase extraction, which simplifies the detection process and effectively improves the detection accuracy. Firstly, the method detects the planes by utilizing the rotational translation method, secondly, the multi-surface separation technique is utilized to extract and separate the face shapes of the three surfaces in the rotational translation method, and lastly, the reference plane error is calibrated and excluded from the measurement results to accurately obtain the surface morphology of the component under test. The experimental results show that the present method reduces the PV of the residual error by about 25 % and reduces the RMS of the residual error by about 30 % compared to the existing absolute detection methods. The experimental results show that the present method reduces the PV of the residual error by about 25 % and reduces the RMS of the residual error by about 30 % compared to the existing absolute detection methods.
{"title":"Absolute detection method based on multi-signal phase extraction and separation","authors":"Yi Hou , Zhisong Li , Xin Tang","doi":"10.1016/j.optlaseng.2024.108637","DOIUrl":"10.1016/j.optlaseng.2024.108637","url":null,"abstract":"<div><div>The development of optical systems requires high-precision inspection technology, which supports the manufacturing and integration of optical systems. Currently, the method commonly used for high-precision optical plane inspection is interferometry based on the reference plane, however, its inspection accuracy is constrained by the accuracy of the reference plane. Therefore, this paper proposes an absolute detection method based on multi-signal phase extraction, which simplifies the detection process and effectively improves the detection accuracy. Firstly, the method detects the planes by utilizing the rotational translation method, secondly, the multi-surface separation technique is utilized to extract and separate the face shapes of the three surfaces in the rotational translation method, and lastly, the reference plane error is calibrated and excluded from the measurement results to accurately obtain the surface morphology of the component under test. The experimental results show that the present method reduces the PV of the residual error by about 25 % and reduces the RMS of the residual error by about 30 % compared to the existing absolute detection methods. The experimental results show that the present method reduces the PV of the residual error by about 25 % and reduces the RMS of the residual error by about 30 % compared to the existing absolute detection methods.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"184 ","pages":"Article 108637"},"PeriodicalIF":3.5,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A hollow flat-topped Gaussian beam (HFTGB) embedded multi-vortex singularities is put forward in this paper. Its propagation dynamics under the different cases of topological charge, singularity number and location are investigated by means of numerical simulation and experiment. Especially, the evolution of the HFTGB carrying different fractional topological charges is also examined. In addition, the radiation force on a Rayleigh microsphere induced the HFTGB embedded multi-vortex singularities are analyzed and discussed in detail. The results demonstrate that, combined with the advantages of multiple singularities, the HFTGBs have a higher degree of regulatory freedom for trapping or manipulating Rayleigh particles. This work will contribute to the more precise and flexible use of HFTGBs in optical manipulation, optical communication, and other application scenarios.
{"title":"Propagation dynamics and radiation force of the hollow flat-topped Gaussian beam carrying multi-vortex singularities","authors":"Jian Yu , Shandong Tong , Shuaiqi Geng , Bowen Dong , Zhe Zhang , Min Zhou , Peichao Zheng","doi":"10.1016/j.optlaseng.2024.108644","DOIUrl":"10.1016/j.optlaseng.2024.108644","url":null,"abstract":"<div><div>A hollow flat-topped Gaussian beam (HFTGB) embedded multi-vortex singularities is put forward in this paper. Its propagation dynamics under the different cases of topological charge, singularity number and location are investigated by means of numerical simulation and experiment. Especially, the evolution of the HFTGB carrying different fractional topological charges is also examined. In addition, the radiation force on a Rayleigh microsphere induced the HFTGB embedded multi-vortex singularities are analyzed and discussed in detail. The results demonstrate that, combined with the advantages of multiple singularities, the HFTGBs have a higher degree of regulatory freedom for trapping or manipulating Rayleigh particles. This work will contribute to the more precise and flexible use of HFTGBs in optical manipulation, optical communication, and other application scenarios.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"184 ","pages":"Article 108644"},"PeriodicalIF":3.5,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142539710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-14DOI: 10.1016/j.optlaseng.2024.108634
Wei Liang , Xiaodong Hong , Dichang Huang , Linnan Chen , Jianfeng Zhong , Qiukun Zhang , Jiewen Lin , shuncong Zhong , Tao Li
Accurate rotational speed measurement is a prerequisite for realizing the condition monitoring and fault diagnosis of rotating equipment. This study proposes a novel rotational speed measurement method based on optical coherent displacement measurement. An optical coherence system is used to measure the relative depth of the shaft surface with uniformly etched micro-indentations on the circumferential surface. Fast Fourier transform (FFT) and the Hanning window energy centrobaric method (HnWECM) are used to process the collected photoelectric signals to obtain depth information and thereby realize the measurement of surface micro-indentations. During the operation, the rotational speed of the shaft is obtained by calculating the ratio of the angular difference between the relative depth of the rectangular pulses of the surface and the time interval. The experimental validation of the response is performed. The experimental results show that in the range of 0 rpm to 60 rpm, the indication error is <1 %, the nonlinearity error is <0.3584 %, and the repeatability error is <0.28 %. In the range of 0 rpm to 600 rpm, the rotational speed measurement method performed well with an indication error of <0.5 %, a maximum nonlinear error of 0.22 %, and a repeatability error of no >0.28 %. Compared with the results reported in existing literature, the proposed method offers advantages in terms of accuracy, linearity, and repeatability.
{"title":"Novel rotational speed measuring method based on micro-indentation-shaft detected by optical coherent system","authors":"Wei Liang , Xiaodong Hong , Dichang Huang , Linnan Chen , Jianfeng Zhong , Qiukun Zhang , Jiewen Lin , shuncong Zhong , Tao Li","doi":"10.1016/j.optlaseng.2024.108634","DOIUrl":"10.1016/j.optlaseng.2024.108634","url":null,"abstract":"<div><div>Accurate rotational speed measurement is a prerequisite for realizing the condition monitoring and fault diagnosis of rotating equipment. This study proposes a novel rotational speed measurement method based on optical coherent displacement measurement. An optical coherence system is used to measure the relative depth of the shaft surface with uniformly etched micro-indentations on the circumferential surface. Fast Fourier transform (FFT) and the Hanning window energy centrobaric method (HnWECM) are used to process the collected photoelectric signals to obtain depth information and thereby realize the measurement of surface micro-indentations. During the operation, the rotational speed of the shaft is obtained by calculating the ratio of the angular difference between the relative depth of the rectangular pulses of the surface and the time interval. The experimental validation of the response is performed. The experimental results show that in the range of 0 rpm to 60 rpm, the indication error is <1 %, the nonlinearity error is <0.3584 %, and the repeatability error is <0.28 %. In the range of 0 rpm to 600 rpm, the rotational speed measurement method performed well with an indication error of <0.5 %, a maximum nonlinear error of 0.22 %, and a repeatability error of no >0.28 %. Compared with the results reported in existing literature, the proposed method offers advantages in terms of accuracy, linearity, and repeatability.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"184 ","pages":"Article 108634"},"PeriodicalIF":3.5,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142433990","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-14DOI: 10.1016/j.optlaseng.2024.108633
Svetlana Shmavonyan, Aleksandr Khanbekyan, Marina Movsisyan, Aram Papoyan
We present a spatial scanning technique for optical transmission imaging of strongly-scattering objects based on spatially-selective registration of ballistic photons originating from modulated (pulsed) laser radiation. The registration system counts the number of transmitted pulses at any pixel, forming a grayscale image. By choosing modulation regime, it is possible to record a real analog image or to outline contours of the image features, without necessity of software image processing. The developed system is tested on model scattering object (stack of paper) and biological object (human hand). Due to the automatic adjustment of the signal level, realized by the appropriate laser modulation mode, formation of an image with a structure uniformly pronounced across the aperture has been attained, even under conditions of significant changes in background transmission.
{"title":"Scanning technique for direct optical transmission imaging of highly-scattering objects","authors":"Svetlana Shmavonyan, Aleksandr Khanbekyan, Marina Movsisyan, Aram Papoyan","doi":"10.1016/j.optlaseng.2024.108633","DOIUrl":"10.1016/j.optlaseng.2024.108633","url":null,"abstract":"<div><div>We present a spatial scanning technique for optical transmission imaging of strongly-scattering objects based on spatially-selective registration of ballistic photons originating from modulated (pulsed) laser radiation. The registration system counts the number of transmitted pulses at any pixel, forming a grayscale image. By choosing modulation regime, it is possible to record a real analog image or to outline contours of the image features, without necessity of software image processing. The developed system is tested on model scattering object (stack of paper) and biological object (human hand). Due to the automatic adjustment of the signal level, realized by the appropriate laser modulation mode, formation of an image with a structure uniformly pronounced across the aperture has been attained, even under conditions of significant changes in background transmission.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"184 ","pages":"Article 108633"},"PeriodicalIF":3.5,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142434074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-12DOI: 10.1016/j.optlaseng.2024.108625
Jiashu Wang, Quan Yang, Xiaochen Wang, Xing Mao
Metal pipes are extensively utilized in various industries. However, uneven wall thickness resulting from aging, corrosion, and other factors can pose safety hazards. While traditional inspection methods have limitations, laser ultrasonic technology provides non-contact, long-distance detection, making it suitable for online inspection in challenging environments. In this study, laser ultrasonic technology is employed to detect the wall thickness of metal pipes, overcoming challenges such as same-side detection and signal processing. A signal processing method based on the differential algorithm successfully extracted a clear and stable longitudinal wave signal while effectively suppressing noise interference. Additionally, a new wall thickness calculation model considering the pipe's geometry is developed. Experimental validation demonstrated that the calculation results of the model are in good agreement with the actual measured values, with a relative error of 2.19%. These results confirm the high accuracy and reliability of the laser ultrasonic method in the wall thickness inspection of metal pipes and demonstrate its potential in this field.
{"title":"Laser ultrasonic system for metal pipe wall thickness measurement: Differential signal processing and geometric compensation calculation model","authors":"Jiashu Wang, Quan Yang, Xiaochen Wang, Xing Mao","doi":"10.1016/j.optlaseng.2024.108625","DOIUrl":"10.1016/j.optlaseng.2024.108625","url":null,"abstract":"<div><div>Metal pipes are extensively utilized in various industries. However, uneven wall thickness resulting from aging, corrosion, and other factors can pose safety hazards. While traditional inspection methods have limitations, laser ultrasonic technology provides non-contact, long-distance detection, making it suitable for online inspection in challenging environments. In this study, laser ultrasonic technology is employed to detect the wall thickness of metal pipes, overcoming challenges such as same-side detection and signal processing. A signal processing method based on the differential algorithm successfully extracted a clear and stable longitudinal wave signal while effectively suppressing noise interference. Additionally, a new wall thickness calculation model considering the pipe's geometry is developed. Experimental validation demonstrated that the calculation results of the model are in good agreement with the actual measured values, with a relative error of 2.19%. These results confirm the high accuracy and reliability of the laser ultrasonic method in the wall thickness inspection of metal pipes and demonstrate its potential in this field.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"184 ","pages":"Article 108625"},"PeriodicalIF":3.5,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418704","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Laser speckle imaging, known for its ability to capture object surface features with simple setup and reduced sensitivity to ambient light, is of significant research interest for coal and gangue recognition. However, the complex surface structures of minerals in practical settings pose challenges in improving recognition accuracy over large sample sizes and extended periods using manual feature design. To address this issue, we propose a coal and gangue recognition method that integrates laser speckle imaging with deep learning. Based on objective speckle imaging theory, we designed a coal and gangue laser speckle image acquisition system and curated a dataset encompassing diverse lighting conditions for speckle imaging. We developed a lightweight YOLOv5s model to extract rich surface information from mineral laser speckle images, achieving high-precision coal and gangue detection while reducing computational demands. Experimental results demonstrate significant improvements in model size, training effectiveness, feature extraction, and recognition accuracy by lightening the YOLOv5s model. Furthermore, our method exhibits improved accuracy and stability in coal and gangue recognition under varying lighting conditions compared to manual feature design approach. Additionally, our model strikes a balance between complexity and accuracy, offering practical advantages over existing models for industrial applications. These findings provide valuable technical support for the future realization of intelligent coal and gangue recognition.
{"title":"A lightweight object detection algorithm for coal and gangue with laser speckle imaging","authors":"Hequn Li, Ling Ling, Yufei Zheng, Hanxi Yang, Yun Liu, Mingxing Jiao","doi":"10.1016/j.optlaseng.2024.108630","DOIUrl":"10.1016/j.optlaseng.2024.108630","url":null,"abstract":"<div><div>Laser speckle imaging, known for its ability to capture object surface features with simple setup and reduced sensitivity to ambient light, is of significant research interest for coal and gangue recognition. However, the complex surface structures of minerals in practical settings pose challenges in improving recognition accuracy over large sample sizes and extended periods using manual feature design. To address this issue, we propose a coal and gangue recognition method that integrates laser speckle imaging with deep learning. Based on objective speckle imaging theory, we designed a coal and gangue laser speckle image acquisition system and curated a dataset encompassing diverse lighting conditions for speckle imaging. We developed a lightweight YOLOv5s model to extract rich surface information from mineral laser speckle images, achieving high-precision coal and gangue detection while reducing computational demands. Experimental results demonstrate significant improvements in model size, training effectiveness, feature extraction, and recognition accuracy by lightening the YOLOv5s model. Furthermore, our method exhibits improved accuracy and stability in coal and gangue recognition under varying lighting conditions compared to manual feature design approach. Additionally, our model strikes a balance between complexity and accuracy, offering practical advantages over existing models for industrial applications. These findings provide valuable technical support for the future realization of intelligent coal and gangue recognition.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"184 ","pages":"Article 108630"},"PeriodicalIF":3.5,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study introduces an optically equivalent system for a programmable linear retarder, capable of arbitrarily changing the fast axis and phase retardation without any mechanical rotation apparatus. The programmable linear retarder comprises a quarter-wave plate and a pair of liquid crystal variable retarders, paired with a retroreflection scheme for implementation. The non-ideal characteristics of the non-polarizing beamsplitter in the optical system were recognized and corrected to ensure that the linear phase retardation and fast axis orientation of the programmable linear retarder closely match the design values. Additionally, the programmable linear retarder was employed for incident light's polarization conversion. Experimental results illustrate that the actual measured linear phase retardation, fast axis orientation, and the emergent light's polarization state after polarization conversion closely align with the design and theoretical values, confirming the proposed method's validity.
{"title":"Programmable linear retarder using liquid crystal variable retarders with calibration for non-ideal beam splitter properties","authors":"Chien-Yuan Han , Zhen-Xiang Chao , Yi-Hsin Chan , Chih-Jen Yu","doi":"10.1016/j.optlaseng.2024.108623","DOIUrl":"10.1016/j.optlaseng.2024.108623","url":null,"abstract":"<div><div>This study introduces an optically equivalent system for a programmable linear retarder, capable of arbitrarily changing the fast axis and phase retardation without any mechanical rotation apparatus. The programmable linear retarder comprises a quarter-wave plate and a pair of liquid crystal variable retarders, paired with a retroreflection scheme for implementation. The non-ideal characteristics of the non-polarizing beamsplitter in the optical system were recognized and corrected to ensure that the linear phase retardation and fast axis orientation of the programmable linear retarder closely match the design values. Additionally, the programmable linear retarder was employed for incident light's polarization conversion. Experimental results illustrate that the actual measured linear phase retardation, fast axis orientation, and the emergent light's polarization state after polarization conversion closely align with the design and theoretical values, confirming the proposed method's validity.</div></div>","PeriodicalId":49719,"journal":{"name":"Optics and Lasers in Engineering","volume":"184 ","pages":"Article 108623"},"PeriodicalIF":3.5,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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