The passive terahertz imaging human body security technology has begun to be applied in dense pedestrian flow security fields such as subways and public venues. However, passive terahertz imaging systems directly generate terahertz images, which have problems such as low signal-to-noise ratio and poor resolution. For the identification of suspicious objects hidden under human clothing, the naked eye observation method by security personnel is difficult to distinguish suspicious objects, with a high error rate and slow speed. To balance the accuracy and speed of detecting suspicious objects hidden under human clothing in security scenarios, taking into account terahertz image quality and target detection accuracy, a DeepLabV3+ deep learning model is used to detect targets, achieving object detection and recognition based on passive terahertz imaging human security systems.
{"title":"Terahertz detection and recognition of suspicious objects hidden in the human body based on DeepLabV3+ deep learning model","authors":"Yaoyao Xue, Qiqi Li, Mingyang Jiang, Jiusheng Li","doi":"10.1117/12.3005284","DOIUrl":"https://doi.org/10.1117/12.3005284","url":null,"abstract":"The passive terahertz imaging human body security technology has begun to be applied in dense pedestrian flow security fields such as subways and public venues. However, passive terahertz imaging systems directly generate terahertz images, which have problems such as low signal-to-noise ratio and poor resolution. For the identification of suspicious objects hidden under human clothing, the naked eye observation method by security personnel is difficult to distinguish suspicious objects, with a high error rate and slow speed. To balance the accuracy and speed of detecting suspicious objects hidden under human clothing in security scenarios, taking into account terahertz image quality and target detection accuracy, a DeepLabV3+ deep learning model is used to detect targets, achieving object detection and recognition based on passive terahertz imaging human security systems.","PeriodicalId":298662,"journal":{"name":"Applied Optics and Photonics China","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138965031","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}
Yuexing Wang, Chuangang Xu, Jianzhong Su, Jinwen Tian
With the advancement of drone technology, object detection from the perspective of drones has found extensive applications in various fields, including surveillance, search operations, and reconnaissance tasks. Currently, most drones in the market are equipped with visible light imagers, while some high-end drones are equipped with infrared imaging detectors capable of performing infrared object detection tasks. Infrared imaging utilizes a passive imaging mode, enabling it to detect thermal radiation emitted by objects. As a result, it offers the distinct advantage of continuous operation without being restricted by daylight conditions. In comparison to visible imaging, infrared imaging uses longer wavelengths and possesses a certain level of penetration capability through clouds and smoke. Consequently, infrared object detection represents a significant research area within the field of object detection. However, detecting infrared objects, especially small ones, remains challenging due to the complexity of background information, lower resolution compared to visible images, and the lack of shape and texture information in infrared images. In response to these challenges, this study proposes a real-time drone-perspective infrared (IR) object detection method based on the YOLOv5 framework, known as DIR-YOLOv5. To effectively address the challenge of infrared vehicles occupying fewer pixels in the drone’s perspective image and making objects difficult to detect, the coordinate attention (CA) for feature enhancement is introduced. we also introduce a Spatial-Channel dynamic and query-aware sparse attention mechanism (SCBiFormer), which is optimized based on BiFormer. Additionally, we redefine the loss function as the Repulsion Loss function to tackle the problem of infrared vehicle objects gathering and overlapping occlusion in scenarios like parking lots. Furthermore, we expand the ISVD infrared image object detection dataset to include multiple scenarios and conduct experiments using this dataset. The experimental results demonstrate the excellent performance of the proposed method in infrared image object detection tasks, showing improved object detection accuracy and reduced false detection rate compared to current mainstream methods.
{"title":"DIR-YOLOv5: a real-time drone-perspective infrared object detection method based on YOLOv5","authors":"Yuexing Wang, Chuangang Xu, Jianzhong Su, Jinwen Tian","doi":"10.1117/12.2692731","DOIUrl":"https://doi.org/10.1117/12.2692731","url":null,"abstract":"With the advancement of drone technology, object detection from the perspective of drones has found extensive applications in various fields, including surveillance, search operations, and reconnaissance tasks. Currently, most drones in the market are equipped with visible light imagers, while some high-end drones are equipped with infrared imaging detectors capable of performing infrared object detection tasks. Infrared imaging utilizes a passive imaging mode, enabling it to detect thermal radiation emitted by objects. As a result, it offers the distinct advantage of continuous operation without being restricted by daylight conditions. In comparison to visible imaging, infrared imaging uses longer wavelengths and possesses a certain level of penetration capability through clouds and smoke. Consequently, infrared object detection represents a significant research area within the field of object detection. However, detecting infrared objects, especially small ones, remains challenging due to the complexity of background information, lower resolution compared to visible images, and the lack of shape and texture information in infrared images. In response to these challenges, this study proposes a real-time drone-perspective infrared (IR) object detection method based on the YOLOv5 framework, known as DIR-YOLOv5. To effectively address the challenge of infrared vehicles occupying fewer pixels in the drone’s perspective image and making objects difficult to detect, the coordinate attention (CA) for feature enhancement is introduced. we also introduce a Spatial-Channel dynamic and query-aware sparse attention mechanism (SCBiFormer), which is optimized based on BiFormer. Additionally, we redefine the loss function as the Repulsion Loss function to tackle the problem of infrared vehicle objects gathering and overlapping occlusion in scenarios like parking lots. Furthermore, we expand the ISVD infrared image object detection dataset to include multiple scenarios and conduct experiments using this dataset. The experimental results demonstrate the excellent performance of the proposed method in infrared image object detection tasks, showing improved object detection accuracy and reduced false detection rate compared to current mainstream methods.","PeriodicalId":298662,"journal":{"name":"Applied Optics and Photonics China","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138965077","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}
A composite piezoelectric deformable mirror (DM) with woofer-tweeter configuration is proposed for astronomy applications. This DM consists of unimorph DM and piezoelectric actuators array. Compared with conventional DM, the composite piezoelectric DM has a characteristic of both large stroke and high bandwidth, which is suitable for correcting those aberrations introduced by atmospheric turbulence in real time. The prototype of the composite DM is prepared, and an adaptive optical testing system based on Shack-Hartmann sensor is established. Experimental results indicate that the woofer–tweeter DM has the capability to compensate for the first 20 terms of Zernike aberrations with normalized RMS wavefront errors less than 15%. The proposed composite piezoelectric DM has good performance and great potential in astronomical applications.
{"title":"A composite piezoelectric deformable mirror with woofer-tweeter configuration","authors":"Kaiye Bao, Licheng Yu, Jianqiang Ma","doi":"10.1117/12.3007361","DOIUrl":"https://doi.org/10.1117/12.3007361","url":null,"abstract":"A composite piezoelectric deformable mirror (DM) with woofer-tweeter configuration is proposed for astronomy applications. This DM consists of unimorph DM and piezoelectric actuators array. Compared with conventional DM, the composite piezoelectric DM has a characteristic of both large stroke and high bandwidth, which is suitable for correcting those aberrations introduced by atmospheric turbulence in real time. The prototype of the composite DM is prepared, and an adaptive optical testing system based on Shack-Hartmann sensor is established. Experimental results indicate that the woofer–tweeter DM has the capability to compensate for the first 20 terms of Zernike aberrations with normalized RMS wavefront errors less than 15%. The proposed composite piezoelectric DM has good performance and great potential in astronomical applications.","PeriodicalId":298662,"journal":{"name":"Applied Optics and Photonics China","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138965155","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}
Jiongbin Deng, Jia Ye, Lian-shan Yan, W. Pan, Xihua Zou
Radio over fiber (RoF) has become a promising alternative for 5G mobile fronthaul due to its inherent advantages of large bandwidth, low susceptibility to radio frequency interference, and high flexibility. In traditional RoF system, analog signals are transmitted through optical fiber, which is susceptible to nonlinearity and dispersion. However, digitized radio over fiber (DRoF) can effectively mitigate these defects by digitizing the analog signals. This paper explores FPGA-based real-time DRoF transceiver technology, which utilizes varying numbers of quantization bits for real-time vector quantization across different modulation formats. This approach helps prevent the reduction of system spectral efficiency caused by excessive quantization bits. The simulation results demonstrate that, after real-time vector quantization and transmission with 8 and 10 quantization bits, the EVM performance of QPSK and 16-QAM signals stabilizes at 11.8% and 6.7%, respectively, thereby confirming the effectiveness of the proposed scheme.
{"title":"Real-time digitized RoF transceiver technology based on FPGA","authors":"Jiongbin Deng, Jia Ye, Lian-shan Yan, W. Pan, Xihua Zou","doi":"10.1117/12.3005659","DOIUrl":"https://doi.org/10.1117/12.3005659","url":null,"abstract":"Radio over fiber (RoF) has become a promising alternative for 5G mobile fronthaul due to its inherent advantages of large bandwidth, low susceptibility to radio frequency interference, and high flexibility. In traditional RoF system, analog signals are transmitted through optical fiber, which is susceptible to nonlinearity and dispersion. However, digitized radio over fiber (DRoF) can effectively mitigate these defects by digitizing the analog signals. This paper explores FPGA-based real-time DRoF transceiver technology, which utilizes varying numbers of quantization bits for real-time vector quantization across different modulation formats. This approach helps prevent the reduction of system spectral efficiency caused by excessive quantization bits. The simulation results demonstrate that, after real-time vector quantization and transmission with 8 and 10 quantization bits, the EVM performance of QPSK and 16-QAM signals stabilizes at 11.8% and 6.7%, respectively, thereby confirming the effectiveness of the proposed scheme.","PeriodicalId":298662,"journal":{"name":"Applied Optics and Photonics China","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138963473","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}
Aiming at the problem that the measurement of strong laser far-field focal spot based on side lobe beam diffraction inversion cannot extract the smallest measurable signal in the periphery of the side lobe image, this paper proposes a method for detecting the peak parameters of the weak signal region in the side lobe based on neighborhood vector principal component analysis (NVPCA) image enhancement. The main optimization measures are as follows: First, treat each pixel in the sidelobe image and its 8 neighborhood pixels as a column vector to construct a 9-dimensional data cube, and the first dimensional data after PCA transformation is an NVPCA image; Secondly, using angle transformation to transform the detection object, the various peak parameters of the one-dimensional sidelobe curve in all directions are detected, thereby obtaining the quantified energy distribution characteristics of the weak signal area of the sidelobe beam; Then, search for the maximum position points of each sidelobe peak in all directions, connect all position points to generate a maximum ring for each sidelobe peak, and calculate the grayscale mean of each maximum ring; Finally, the grayscale mean of the maximum rings that is greater than the LCM target separation threshold and the smallest is selected as the minimum measurable sidelobe peak signal of the entire sidelobe beam. The experimental results show that the sidelobe weak signal detection method based on NVPCA image enhancement can separate and extract the minimum measurable signal from the fifth peak ring on the periphery of the sidelobe image, increasing the dynamic range ratio by 1.528 times, improving the calculation accuracy of the dynamic range ratio, and laying a foundation for the future accurate measurement of strong laser far field in large scientific devices.
{"title":"The detection method of sidelobe peaks parameter in weak signal regions based on NVPCA image enhancement","authors":"Zhengzhou Wang, Jitong Wei, Li Wang","doi":"10.1117/12.3009387","DOIUrl":"https://doi.org/10.1117/12.3009387","url":null,"abstract":"Aiming at the problem that the measurement of strong laser far-field focal spot based on side lobe beam diffraction inversion cannot extract the smallest measurable signal in the periphery of the side lobe image, this paper proposes a method for detecting the peak parameters of the weak signal region in the side lobe based on neighborhood vector principal component analysis (NVPCA) image enhancement. The main optimization measures are as follows: First, treat each pixel in the sidelobe image and its 8 neighborhood pixels as a column vector to construct a 9-dimensional data cube, and the first dimensional data after PCA transformation is an NVPCA image; Secondly, using angle transformation to transform the detection object, the various peak parameters of the one-dimensional sidelobe curve in all directions are detected, thereby obtaining the quantified energy distribution characteristics of the weak signal area of the sidelobe beam; Then, search for the maximum position points of each sidelobe peak in all directions, connect all position points to generate a maximum ring for each sidelobe peak, and calculate the grayscale mean of each maximum ring; Finally, the grayscale mean of the maximum rings that is greater than the LCM target separation threshold and the smallest is selected as the minimum measurable sidelobe peak signal of the entire sidelobe beam. The experimental results show that the sidelobe weak signal detection method based on NVPCA image enhancement can separate and extract the minimum measurable signal from the fifth peak ring on the periphery of the sidelobe image, increasing the dynamic range ratio by 1.528 times, improving the calculation accuracy of the dynamic range ratio, and laying a foundation for the future accurate measurement of strong laser far field in large scientific devices.","PeriodicalId":298662,"journal":{"name":"Applied Optics and Photonics China","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138963651","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}
Zhe Chen, Xinnan Li, Zibo Jiang, Chen Xu, Ran Duan
Abrasive water jet processing technology is a processing method developed in recent decades using highenergy beams, which is suitable to removal and processing different materials, because its processing process has its own cooling effect and has incomparable advantages in other processing methods. Process studies involving multiple materials in the same area have not been reported. In this paper, the influence of abrasive water jet processing technology parameters on the removal rate of different materials in a small area is studied experimentally, and the removal rate of high-purity quartz glass, doped quartz glass and epoxy resin adhesive layer is tested by single factor and orthogonal test method. Experiments show that within a certain range of process parameters, jet pressure, nozzle diameter and nozzle height have obvious effects on the removal rate, while abrasive particle size have the lowest impact. Experiments are used to derive optimal process parameters for simultaneous removal of different materials.
{"title":"Experimental study on multi-material composite surface polishing by abrasive water jet","authors":"Zhe Chen, Xinnan Li, Zibo Jiang, Chen Xu, Ran Duan","doi":"10.1117/12.3007778","DOIUrl":"https://doi.org/10.1117/12.3007778","url":null,"abstract":"Abrasive water jet processing technology is a processing method developed in recent decades using highenergy beams, which is suitable to removal and processing different materials, because its processing process has its own cooling effect and has incomparable advantages in other processing methods. Process studies involving multiple materials in the same area have not been reported. In this paper, the influence of abrasive water jet processing technology parameters on the removal rate of different materials in a small area is studied experimentally, and the removal rate of high-purity quartz glass, doped quartz glass and epoxy resin adhesive layer is tested by single factor and orthogonal test method. Experiments show that within a certain range of process parameters, jet pressure, nozzle diameter and nozzle height have obvious effects on the removal rate, while abrasive particle size have the lowest impact. Experiments are used to derive optimal process parameters for simultaneous removal of different materials.","PeriodicalId":298662,"journal":{"name":"Applied Optics and Photonics China","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138963723","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}
Zhuoyuan Shi, Huan Tang, Yuan Zhang, Renxian Li, Bing Wei, I. Minin, O. Minin, Bing Yan
The resonance scattering caused by the interaction between a dielectric cylinder rotating at a steady angular velocity and a plane wave are studied using the method of separation of variables and the multipole expansion method. In addition, the effect of resonance on curved photonic nanojets (PNJ) is also analyzed. During the study, the critical value of resonance scattering is found by changing the dimensionless and dimensional parameters of the medium cylinder. It is found that the rotation of particles can create and destroy resonance phenomena. The resonance scattering of rotating dielectric cylinders produced by plane waves provides a new direction for the study of PNJ and whispering gallery mode (WGM), as well as the design and application of ultra-sensitive sensors and resonators
{"title":"Resonance scattering by a rotating cylinder","authors":"Zhuoyuan Shi, Huan Tang, Yuan Zhang, Renxian Li, Bing Wei, I. Minin, O. Minin, Bing Yan","doi":"10.1117/12.3007429","DOIUrl":"https://doi.org/10.1117/12.3007429","url":null,"abstract":"The resonance scattering caused by the interaction between a dielectric cylinder rotating at a steady angular velocity and a plane wave are studied using the method of separation of variables and the multipole expansion method. In addition, the effect of resonance on curved photonic nanojets (PNJ) is also analyzed. During the study, the critical value of resonance scattering is found by changing the dimensionless and dimensional parameters of the medium cylinder. It is found that the rotation of particles can create and destroy resonance phenomena. The resonance scattering of rotating dielectric cylinders produced by plane waves provides a new direction for the study of PNJ and whispering gallery mode (WGM), as well as the design and application of ultra-sensitive sensors and resonators","PeriodicalId":298662,"journal":{"name":"Applied Optics and Photonics China","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138963727","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}
Tunable and low-power microcavities play a vital role in facilitating the development of large-scale photonic integrated circuits. Among various tuning methods, thermal tuning has gained significant popularity due to its convenience and stability, especially in the fields of optical neural networks and quantum information processing. In recent years, graphene thermal tuning has emerged as a promising technique, offering both tunability and power efficiency by eliminating the need for thick spacers to prevent light absorption. In this study, we propose and fabricate a silicon-based on-chip Fano resonator with graphene nano-heaters. This innovative Fano structure incorporates a scattering block and can be easily manufactured in large quantities. Experimental results demonstrate that the resonator exhibits desirable characteristics, including a high quality factor of approximately 31000 and a low state-switching power consumption of around 1 mW. The temporal responses of the microcavity exhibit satisfactory modulation speed, with a rise time of 9.8 μs and a fall time of 16.6 μs. The findings of this research offer an alternative solution for the future development of large-scale tunable and low-power-consumption optical networks, with potential applications in optical filters and switches.
{"title":"Thermally tunable high Q-factor and low-power silicon resonators using graphene transparent electrodes","authors":"Qilin Hong, Ping Xu, Wei Xu, Zhihong Zhu","doi":"10.1117/12.3006019","DOIUrl":"https://doi.org/10.1117/12.3006019","url":null,"abstract":"Tunable and low-power microcavities play a vital role in facilitating the development of large-scale photonic integrated circuits. Among various tuning methods, thermal tuning has gained significant popularity due to its convenience and stability, especially in the fields of optical neural networks and quantum information processing. In recent years, graphene thermal tuning has emerged as a promising technique, offering both tunability and power efficiency by eliminating the need for thick spacers to prevent light absorption. In this study, we propose and fabricate a silicon-based on-chip Fano resonator with graphene nano-heaters. This innovative Fano structure incorporates a scattering block and can be easily manufactured in large quantities. Experimental results demonstrate that the resonator exhibits desirable characteristics, including a high quality factor of approximately 31000 and a low state-switching power consumption of around 1 mW. The temporal responses of the microcavity exhibit satisfactory modulation speed, with a rise time of 9.8 μs and a fall time of 16.6 μs. The findings of this research offer an alternative solution for the future development of large-scale tunable and low-power-consumption optical networks, with potential applications in optical filters and switches.","PeriodicalId":298662,"journal":{"name":"Applied Optics and Photonics China","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138965148","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}
The successful achievement of the scientific objectives of the Visible Telescope (VT) in the Space Multi-band Variable Object Monitor (SVOM) mission relies heavily on high-precision quantum efficiency calibration. The calibration process for the VT CCD presents a challenge due to the requirement for extremely low radiation levels given the long integration time of the CCD. To address the difficulty in accurately measuring such low radiance, a two-step calibration method is employed. This method involves the use of two photodiodes, one positioned at the CCD location and the other in an integrating sphere. In the first step, the proportional relationship between the measured illuminance values of the two photodiodes is calibrated under high illumination conditions. This step establishes a reliable reference for subsequent calibrations. In the second step, the CCD is calibrated using the integrating sphere photodiode under low illumination conditions. The measured illuminance is then converted to the CCD position. Experimental results have demonstrated the effectiveness of this two-step calibration method, achieving a quantum efficiency calibration uncertainty of 1.7%. This approach provides a reliable and accurate means of calibrating the quantum efficiency of the CCD in the VT instrument.
{"title":"Research on quantum efficiency calibration of SVOM VT CCDs","authors":"Yue Pan, Lijun Dan, Zhonghan Sun, Chao Huang, Wei Li, Fengtao Wang, Hui Zhao, Jian Zhang","doi":"10.1117/12.3007801","DOIUrl":"https://doi.org/10.1117/12.3007801","url":null,"abstract":"The successful achievement of the scientific objectives of the Visible Telescope (VT) in the Space Multi-band Variable Object Monitor (SVOM) mission relies heavily on high-precision quantum efficiency calibration. The calibration process for the VT CCD presents a challenge due to the requirement for extremely low radiation levels given the long integration time of the CCD. To address the difficulty in accurately measuring such low radiance, a two-step calibration method is employed. This method involves the use of two photodiodes, one positioned at the CCD location and the other in an integrating sphere. In the first step, the proportional relationship between the measured illuminance values of the two photodiodes is calibrated under high illumination conditions. This step establishes a reliable reference for subsequent calibrations. In the second step, the CCD is calibrated using the integrating sphere photodiode under low illumination conditions. The measured illuminance is then converted to the CCD position. Experimental results have demonstrated the effectiveness of this two-step calibration method, achieving a quantum efficiency calibration uncertainty of 1.7%. This approach provides a reliable and accurate means of calibrating the quantum efficiency of the CCD in the VT instrument.","PeriodicalId":298662,"journal":{"name":"Applied Optics and Photonics China","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138965199","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}
Xinggui Xu, Hong Li, Yue-Jie Zhang, Weihe Ren, Tao Zhang
Background oriented system (BOS) technology is widely used for measuring flow field density information. The fingerprint information of high-speed target flow field can be calculated with the digital image correction (DIC) method. However, these traditional DIC algorithms are unable to obtain large-scale features of target flow fields and costing high computational complexity. To deal with those problems, a method combination of dual tree complex wavelet transform and optical flow (DTCWT-OF) is proposed. The proposed method adopts a much sparser gradient divergence regularization to obtain much more sparse statistical characteristics of the target flow field, and utilize the prior knowledge of the target flow field fingerprint information. Meanwhile, the reconstruction method is processed in the wavelet transform domain. Compared to traditional DIC methods, the experimental results show that the proposed method improves the SNR by 5dB and can achieve quasi real-time reconstruction.
{"title":"Target flow field reconstruction based on dual tree complex wavelet transform and optical flow","authors":"Xinggui Xu, Hong Li, Yue-Jie Zhang, Weihe Ren, Tao Zhang","doi":"10.1117/12.3006467","DOIUrl":"https://doi.org/10.1117/12.3006467","url":null,"abstract":"Background oriented system (BOS) technology is widely used for measuring flow field density information. The fingerprint information of high-speed target flow field can be calculated with the digital image correction (DIC) method. However, these traditional DIC algorithms are unable to obtain large-scale features of target flow fields and costing high computational complexity. To deal with those problems, a method combination of dual tree complex wavelet transform and optical flow (DTCWT-OF) is proposed. The proposed method adopts a much sparser gradient divergence regularization to obtain much more sparse statistical characteristics of the target flow field, and utilize the prior knowledge of the target flow field fingerprint information. Meanwhile, the reconstruction method is processed in the wavelet transform domain. Compared to traditional DIC methods, the experimental results show that the proposed method improves the SNR by 5dB and can achieve quasi real-time reconstruction.","PeriodicalId":298662,"journal":{"name":"Applied Optics and Photonics China","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138965276","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：