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- 摘要
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- 实验方案
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Process control and quality assurance in remote laser beam welding by optical coherence tomography
摘要： Remote laser beam welding significantly outperforms conventional joining techniques in terms of flexibility and productivity. This process benefits in particular from a highly focused laser radiation and thus from a well-defined heat input. The small spot sizes of high brilliance laser beam sources, however, require a highly dynamic and precise positioning of the beam. Also, the laser intensities typically applied in this context result in high process dynamics and in demand for a method to ensure a sufficient weld quality. A novel sensor concept for remote laser processing based on optical coherence tomography (OCT) was used for both quality assurance and edge tracking. The OCT sensor was integrated into a 3D scanner head equipped with an additional internal scanner to deflect the measuring beam independently of the processing beam. With this system, the surface topography of the process zone as well as the surrounding area can be recorded. Fundamental investigations on aluminum, copper, and galvanized steel were carried out. Initially, the influence of the material, the angle of incidence, the welding position within the scanning field, and the temperature on the OCT measuring signal were evaluated. Based on this, measuring strategies for edge tracking were developed and validated. It was shown that orthogonal measuring lines in the advance of the process zone can reliably track the edge of a fillet weld. By recording the topography in the trailing area of the process zone, it was possible to assess the weld seam quality. Comparing the results to microscopic measurements, it was shown that the system is capable of clearly identifying characteristic features of the weld seam. Also, it was possible to observe an influence of the welding process on the surface properties in the heat-affected zone, based on the quality of the measuring signal.
关键词： inline quality assurance,optical coherence tomography,remote laser beam welding,process control
更新于2025-11-28 14:24:20
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Advanced methods for the optical quality assurance of silicon sensors
摘要： We describe a setup for optical quality assurance of silicon microstrip sensors. Pattern recognition algorithms were developed to analyze microscopic scans of the sensors for defects. It is shown that the software has a recognition and classification rate of >90% for defects like scratches, shorts, broken metal lines etc. We have demonstrated that advanced image processing based on neural network techniques is able to further improve the recognition and defect classification rate.
关键词： video microscope,silicon sensors,neural networks,optical quality assurance
更新于2025-09-23 15:23:52
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Suggestion for Comprehensive Quality Assurance of Medical Linear Accelerator in Korea
摘要： ????????? ???? ???????? ????? ?? ????(Task Group: TG) 40 ???? 1994? ??? ??? ?????????, ????????, ? ????????? ?? ??? ?????? ??? ?????? ?? ????? ???? ?? 2010?? AAPM TG-142? ?????. ??? ?? ????? ?? ????? ?? ????? ???? ?? ????????? ?????????? ?2015-005? "????? ???????? ?? ????"? ?????. ???????????? ? ?????? ????????? ?? ???? ?? ? ??, ????? ??? ??, ???? ??/??/???? ? ???? ?? ? ???? ?? ?? ??? ??? ???????? ???? ????? ????? ???? ??. ?? ?? ??????? 3?? ?????????, ?????????, ???????? ?? ?? ????????(Non-IMRT, IMRT, SRS/SBRT)? ???????? ?? ???? ??, ?? ? ????? ????, ??? ???? ?? ?? ???? ??? ??? ?? ????? ????? ??. ??? ???? ?????? ???? ????? ??? ? ?? ???? ?? ??? ?? ???? ?? ? ?????? ?? ?? ????? ??, ?? ? ????? ???? ????? ???? ?? ????. ???? ? ????? ?????? ??? ? ???? ???? ?? ???????? ?? ? TG-142? ??? ?? ??? ??? ?????? ?? ?????? ?? ?? ?? ?????. ??? ?????? ?? ???? ??? ?? ??? ??????? ?? ???? ?? ???? ??? ? ??? ????.
关键词： TG-142,Linear accelerator,NSSC Notification,Quality assurance
更新于2025-09-23 15:23:52
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Automated Verification of IGRT-based Patient Positioning
摘要： A system for automated quality assurance in radiotherapy of a therapist’s registration was designed and tested in clinical practice. The approach compliments the clinical software’s automated registration in terms of algorithm configuration and performance, and constitutes a practical approach for ensuring safe patient setups. Per our convergence analysis, evolutionary algorithms perform better in finding the global optima of the cost function with discrepancies from a deterministic optimizer seen sporadically.
关键词： verification,quality assurance
更新于2025-09-23 15:22:29
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Use of a commercial ion chamber detector array for the measurement of high spatial-resolution photon beam profiles
摘要： Linear accelerator (linac) commissioning and quality assurance measurements are time‐consuming tasks that often require a water tank scanning system to acquire pro?le scans for full characterization of dosimetric beam properties. To increase ef?ciency, a method is demonstrated to acquire variable resolution, photon beam pro?le data using a commercially available ion chamber array (0.5 cm detector spacing). Field sizes of 2 × 2, 5 × 5, 10 × 10, and 15 × 15 cm2 were acquired at depths in solid water of dmax, 5 cm, and 10 cm; additionally, beam pro?les for ?eld sizes of 25 × 25 and 40 × 40 cm2 were acquired at 5 cm depth in solid water at x‐ray energies of 6 and 23 MV. 1D composite pro?les were generated by combining discrete point measurements made at multiple couch positions. The 1D composite pro?le dataset was evaluated against a commissioning dataset acquired with a 3D water tank scan system utilizing (a) 0.125 cc ion chamber for 5 × 5, 10 × 10, 15 × 15, 25 × 25, and 40 × 40 ?eld sizes and (b) a solid state detector for 2 × 2 cm2 ?eld size. The two datasets were compared to the gamma criteria at 1%/1 mm and 2%/2 mm tolerance. Almost all pass rates exceeded 95% at 2%/2 mm except for the 6 MV 2 × 2 cm2 ?eld size at dmax. Pass rates at 1%/1 mm ranged from 51% to 99%, with an average pass rate of 82%. A fourfold reduction in MU was achieved for scans larger than 15 × 15 cm2 using this method compared to the water tank scans. Further, dynamic wedge measurements acquired with the ion chamber array showed reasonable agreement with the treatment planning system. This method opens up new possibilities for rapid acquisition of variable resolution 2D–3D dosimetric data mitigating the need for acquiring all scan data with in‐water measurements.
关键词： photon beam pro?les,gamma analysis,quality assurance,ion chamber array
更新于2025-09-23 15:21:21
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Hybrid Plasmonic Waveguide based 3??3 Multimode Interferometer for Compact 120?° Optical Hybrid
摘要： The Kinect system is arguably the most popular 3-D camera technology currently on the market. Its application domain is vast and has been deployed in scenarios where accurate geometric measurements are needed. Regarding the PrimeSense technology, a limited amount of work has been devoted to calibrating the Kinect, especially the depth data. The Kinect is, however, inevitably prone to distortions, as independently confirmed by numerous users. An effective method for improving the quality of the Kinect system is by modeling the sensor’s systematic errors using bundle adjustment. In this paper, a method for modeling the intrinsic and extrinsic parameters of the infrared and colour cameras, and more importantly the distortions in the depth image, is presented. Through an integrated marker- and feature-based self-calibration, two Kinects were calibrated. A novel approach for modeling the depth systematic errors as a function of lens distortion and relative orientation parameters is shown to be effective. The results show improvements in geometric accuracy up to 53% compared with uncalibrated point clouds captured using the popular software RGBDemo. Systematic depth discontinuities were also reduced and in the check-plane analysis the noise of the Kinect point cloud was reduced by 17%.
关键词： 3D/stereo scene analysis,quality assurance,quantization,camera calibration,Kinect
更新于2025-09-23 15:21:01
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Texture analysis for automated evaluation of Jaszczak phantom SPECT system tests
摘要： Purpose: Routine quarterly quality assurance (QA) assessment of single photon emission computed tomography (SPECT) systems includes analysis of multipurpose phantoms containing spheres and rods of various sizes. When evaluated by accreditation agencies, criteria applied to assess image quality are largely subjective. Determining a quantified image characteristic metric that emulates human reader impressions of image quality could be quite useful. Our investigation was conducted to ascertain whether image texture analysis metrics, such as those applied to PET scans to detect neoplasms, could prove helpful in linking qualitative statements of phantom sphere and rod visibility to quantified parameters. Because it is not obvious whether it is preferable to submit reconstructions to accrediting agencies performed using typical clinical (CLIN) protocol processing parameters or to follow agencies' filtered backprojection (FBP) suggestions we applied texture analysis metrics to determine the degree to which these choices affect equipment capability assessment.
关键词： phantom,image texture analysis,accreditation,inter-observer agreement,gamma camera,automated,quality assurance
更新于2025-09-23 15:21:01
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[IEEE 2020 IEEE 20th Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems (SiRF) - San Antonio, TX, USA (2020.1.26-2020.1.29)] 2020 IEEE 20th Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems (SiRF) - 28 Gbps Bang-Bang CDR for 100G PSM4 with Independently Tunable Proportional and Integral Parameters of the Loop Filter in $0.25\ \mu \mathrm{m}$ Photonic BiCMOS Technology
摘要： The Kinect system is arguably the most popular 3-D camera technology currently on the market. Its application domain is vast and has been deployed in scenarios where accurate geometric measurements are needed. Regarding the PrimeSense technology, a limited amount of work has been devoted to calibrating the Kinect, especially the depth data. The Kinect is, however, inevitably prone to distortions, as independently confirmed by numerous users. An effective method for improving the quality of the Kinect system is by modeling the sensor’s systematic errors using bundle adjustment. In this paper, a method for modeling the intrinsic and extrinsic parameters of the infrared and colour cameras, and more importantly the distortions in the depth image, is presented. Through an integrated marker- and feature-based self-calibration, two Kinects were calibrated. A novel approach for modeling the depth systematic errors as a function of lens distortion and relative orientation parameters is shown to be effective. The results show improvements in geometric accuracy up to 53% compared with uncalibrated point clouds captured using the popular software RGBDemo. Systematic depth discontinuities were also reduced and in the check-plane analysis the noise of the Kinect point cloud was reduced by 17%.
关键词： 3D/stereo scene analysis,quality assurance,quantization,camera calibration,Kinect
更新于2025-09-23 15:19:57
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A deep learning-based model for defect detection in laser-powder bed fusion using in-situ thermographic monitoring
摘要： Additive manufacturing of metal components with laser-powder bed fusion is a very complex process, since powder has to be melted and cooled in each layer to produce a part. Many parameters influence the printing process; however, defects resulting from suboptimal parameter settings are usually detected after the process. To detect these defects during the printing, different process monitoring techniques such as melt pool monitoring or off-axis infrared monitoring have been proposed. In this work, we used a combination of thermographic off-axis imaging as data source and deep learning-based neural network architectures, to detect printing defects. For the network training, a k-fold cross validation and a hold-out cross validation were used. With these techniques, defects such as delamination and splatter can be recognized with an accuracy of 96.80%. In addition, the model was evaluated with computing class activation heatmaps. The architecture is very small and has low computing costs, which means that it is suitable to operate in real time even on less powerful hardware.
关键词： Additive manufacturing,Convolutional neural networks,Machine learning,Quality assurance
更新于2025-09-23 15:19:57
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A novel phantom for characterization of dual energy imaging using an on-board imaging system
摘要： Dual-energy (DE) imaging using planar imaging with an on-board imager (OBI) is being considered in radiotherapy. We describe here a custom phantom designed to optimize DE imaging parameters using the OBI of a commercial linear accelerator. The phantom was constructed of lung-, tissue- and bone-equivalent material slabs. Five simulated tumors located at two different depths were encased in the lung-equivalent materials. Two slabs with bone-equivalent material inserts were constructed to simulate ribs, which overlap the simulated tumors. DE bone suppression was performed using a weighted logarithmic subtraction based on an iterative method that minimized the contrast between simulated bone- and lung-equivalent materials. The phantom was subsequently used to evaluate different combinations of high-low kV x-ray pairs of images based on the signal-difference-to-noise ratio (SDNR) metric. The results show a strong correlation between tumor visibility and selected energy pairs, where higher energy separation leads to larger SDNR values. To evaluate the effect of image post-processing methods on tumor visibility, an anti-correlated noise reduction (ACNR) technique and adaptive kernel scatter correction method were applied to subsequent DE images. Application of the ACNR technique approximately doubled the SDNR values, hence increasing tumor visibility, while scatter correction had little effect on SDNR values. This phantom allows for quick image acquisition and optimization of imaging parameters and weighting factors. Optimized DE imaging increases soft tissue visibility and may allow for markerless motion tracking of lung tumors.
关键词： custom phantom,quality assurance,dual energy imaging
更新于2025-09-23 15:19:57