The objective of this study is to investigate a high performance and lower cost compact gamma camera module for a multi-head small animal SPECT system. A compact camera module was developed using a thin Lutetium Oxyor...The objective of this study is to investigate a high performance and lower cost compact gamma camera module for a multi-head small animal SPECT system. A compact camera module was developed using a thin Lutetium Oxyorthosilicate （LSO） scintillation crystal slice coupled to a Hamamatsu H8500 position sensitive photomultiplier tube （PSPMT）. A two-stage charge division readout board based on a novel subtractive resistive readout with a truncated center-of-gravity （TCOG） positioning method was developed for the camera. The performance of the camera was evaluated using a flood 99roTe source with a four-quadrant bar-mask phantom. The preliminary experimental results show that the image shrinkage problem associated with the conventional resistive readout can be effectively overcome by the novel subtractive resistive readout with an appropriate fraction subtraction factor. The response output area （ROA） of the camera shown in the flood image was improved up to 34%, and an intrinsic spatial resolution better than 2 mm of detector was achieved. In conclusion, the utilization of a continuous scintillation crystal and a flat-panel PSPMT equipped with a novel subtractive resistive readout is a feasible approach for developing a high performance and lower cost compact gamma camera.展开更多
Small-section hydraulic tunnels are characterized by small spaces and various section forms,under complex environments,which makes it difficult to carry out an inspection by the mobile acquisition equipment.To resolve...Small-section hydraulic tunnels are characterized by small spaces and various section forms,under complex environments,which makes it difficult to carry out an inspection by the mobile acquisition equipment.To resolve these problems,an arbitrarily adjustable camera module deployment method and the corresponding automatic image acquisition equipment with multi-area array cameras are proposed and developed.Such method enables the acquisition of full-length surface images of the hydraulic tunnels with different cross-section forms and diameters by a one-way travel,and the overlap rate and accuracy of the acquired image sets meet the requirements of three-dimensional reconstruction and panoramic image generation.In addition,to improve the speed and accuracy of traditional algorithms for tunnel surface defects detection,this paper proposes an improved YOLOv5s-DECA model.The algorithm introduces DenseNet to optimize the backbone feature extraction network and incorporates an efficient channel attention ECA module to make a better extraction of features of defects.The experimental results show that mAP,and F1-score of YOLOv5-DECA are 73.4%and 74.6%,respectively,which are better than the common model in terms of accuracy and robustness.The proposed YOLOv5-DECA has great detection performance for targets with variable shapes and can solve the problem of classification imbalance in surface defects.Then,by combining YOLOv5-DECA with the direction search algorithm,a“point-ring-section”method is established to allow rapid identification of common surface defects by detecting them layer by layer with the bottom image of the stitched panorama as the seed.The presented method in this paper effectively solves the problem that a single image fails to show the overall distribution of the defects and their accurate positioning in a whole large tunnel section and the effective features of defects in an excessively large panoramic image size are difficult to be captured by the neural network.Field applications demonstrated that the presented method is adequate for high-precision and intelligent surface defect detection and positioning for different small-section hydraulic tunnels such as circular,arch-wall,and box-shaped hydraulic tunnels.展开更多
A phase-diffractive optical element is designed to measure the topological charge of optical vortices. We use the scalar diffraction theory to calculate the far-field diffraction patterns. The simulation results show ...A phase-diffractive optical element is designed to measure the topological charge of optical vortices. We use the scalar diffraction theory to calculate the far-field diffraction patterns. The simulation results show that almost all of the power of the incident beams is diffracted to the same diffraction order, and this approach is also effective for multi-ring optical vortices. We upload this phase-diffractive optical element on the liquid crystal spatial light modulator to do the experiment. The observed far-field diffraction patterns fit well with the simulation results.展开更多
We propose a simple gradation representation method using a binary-weighted computer-generated hologram（CGH） to be displayed on a high-speed spatial light modulator that can be controlled by the pulse-width modulati...We propose a simple gradation representation method using a binary-weighted computer-generated hologram（CGH） to be displayed on a high-speed spatial light modulator that can be controlled by the pulse-width modulation technique. The proposed method uses multiple bit planes comprising binary-weighted CGHs with various pulse widths. The object points of a three-dimensional（3D） object are assigned to multiple bit planes according to their gray levels. The bit planes are sequentially displayed in a time-division-multiplexed manner.Consequently, the proposed method realizes a gradation representation of a reconstructed 3D object.展开更多
基金Supported by National Natural Science Foundation of China (30570520, 10875162)
文摘The objective of this study is to investigate a high performance and lower cost compact gamma camera module for a multi-head small animal SPECT system. A compact camera module was developed using a thin Lutetium Oxyorthosilicate （LSO） scintillation crystal slice coupled to a Hamamatsu H8500 position sensitive photomultiplier tube （PSPMT）. A two-stage charge division readout board based on a novel subtractive resistive readout with a truncated center-of-gravity （TCOG） positioning method was developed for the camera. The performance of the camera was evaluated using a flood 99roTe source with a four-quadrant bar-mask phantom. The preliminary experimental results show that the image shrinkage problem associated with the conventional resistive readout can be effectively overcome by the novel subtractive resistive readout with an appropriate fraction subtraction factor. The response output area （ROA） of the camera shown in the flood image was improved up to 34%, and an intrinsic spatial resolution better than 2 mm of detector was achieved. In conclusion, the utilization of a continuous scintillation crystal and a flat-panel PSPMT equipped with a novel subtractive resistive readout is a feasible approach for developing a high performance and lower cost compact gamma camera.
基金funded by the Hunan Provincial Natural Science Foundation Project(Grant No.2023JJ30672)the Science and Technology Research and Development Program Project of China Railway Group Limited(Grant No.2021-Special-08(A))+1 种基金the Science and Technology Research and Development Plan Project of China National Railway Group Co.Ltd.(Grant No.L2022G003)the Open Foundation of National Engineering Laboratory for High-speed Railway Construction(No.HSR202005).
文摘Small-section hydraulic tunnels are characterized by small spaces and various section forms,under complex environments,which makes it difficult to carry out an inspection by the mobile acquisition equipment.To resolve these problems,an arbitrarily adjustable camera module deployment method and the corresponding automatic image acquisition equipment with multi-area array cameras are proposed and developed.Such method enables the acquisition of full-length surface images of the hydraulic tunnels with different cross-section forms and diameters by a one-way travel,and the overlap rate and accuracy of the acquired image sets meet the requirements of three-dimensional reconstruction and panoramic image generation.In addition,to improve the speed and accuracy of traditional algorithms for tunnel surface defects detection,this paper proposes an improved YOLOv5s-DECA model.The algorithm introduces DenseNet to optimize the backbone feature extraction network and incorporates an efficient channel attention ECA module to make a better extraction of features of defects.The experimental results show that mAP,and F1-score of YOLOv5-DECA are 73.4%and 74.6%,respectively,which are better than the common model in terms of accuracy and robustness.The proposed YOLOv5-DECA has great detection performance for targets with variable shapes and can solve the problem of classification imbalance in surface defects.Then,by combining YOLOv5-DECA with the direction search algorithm,a“point-ring-section”method is established to allow rapid identification of common surface defects by detecting them layer by layer with the bottom image of the stitched panorama as the seed.The presented method in this paper effectively solves the problem that a single image fails to show the overall distribution of the defects and their accurate positioning in a whole large tunnel section and the effective features of defects in an excessively large panoramic image size are difficult to be captured by the neural network.Field applications demonstrated that the presented method is adequate for high-precision and intelligent surface defect detection and positioning for different small-section hydraulic tunnels such as circular,arch-wall,and box-shaped hydraulic tunnels.
基金supported by the National Basic Research Program of China(973 program)under Grant Nos.2014CB340002 and 2014CB340004
文摘A phase-diffractive optical element is designed to measure the topological charge of optical vortices. We use the scalar diffraction theory to calculate the far-field diffraction patterns. The simulation results show that almost all of the power of the incident beams is diffracted to the same diffraction order, and this approach is also effective for multi-ring optical vortices. We upload this phase-diffractive optical element on the liquid crystal spatial light modulator to do the experiment. The observed far-field diffraction patterns fit well with the simulation results.
基金supported by the Japan Society for the Promotion of Science through a Grantin-Aid for Scientific Research(C)15K00153+1 种基金a Grant-in-Aid for Scientific Research(A)25240015
文摘We propose a simple gradation representation method using a binary-weighted computer-generated hologram（CGH） to be displayed on a high-speed spatial light modulator that can be controlled by the pulse-width modulation technique. The proposed method uses multiple bit planes comprising binary-weighted CGHs with various pulse widths. The object points of a three-dimensional（3D） object are assigned to multiple bit planes according to their gray levels. The bit planes are sequentially displayed in a time-division-multiplexed manner.Consequently, the proposed method realizes a gradation representation of a reconstructed 3D object.
