We report a new (to the best of our knowledge) ellipsometric measurement scheme called spatially polarization-modulated ellipsometry (SPME), which is based on the vectorial optical field and digital imageprocessing. ...
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We report a new (to the best of our knowledge) ellipsometric measurement scheme called spatially polarization-modulated ellipsometry (SPME), which is based on the vectorial optical field and digital imageprocessing. A zero-order vortex half-wave retarder (ZVHR) is employed to generate the vectorial optical field and analyze the elliptically polarized light reflected by a thin film;further, an analyzer is set after the ZVHR to form an hourglass intensity pattern due to the spatially polarization modulation;then, the film's ellipsometric angles can be obtained by processing the hourglass intensity image. By analyzing the working principle of SPME, we have found that the film's ellipsometric angles are determined by the bright areas' azimuth angle and contrast of the modulated images, and their mathematical relationships have been deduced and provided. To reduce the adverse effects of image noise and improve the measurement precision, an improved operation mode of SPME is presented by processing the modulated images with their bright areas' azimuth locating at near 45 degrees or 135 degrees and 0 degrees or 90 degrees. Numerical analyzing studies have been carried out on the SiO2 films to validate the feasibility of SPME, and the simulation experiments indicate that the SPME can operate well, even though obvious noise has been added to the modulated intensity image and the measuring error of film thickness and refractive index were less than 0.1 nm and 0.001, respectively. (C) 2020 Optical Society of America
Ball grid array (BGA) packaging is a high-density surface mount technology with the advantages of small size, good heat dissipation, and electrical properties, and is widely applied in the production of large-scale in...
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Ball grid array (BGA) packaging is a high-density surface mount technology with the advantages of small size, good heat dissipation, and electrical properties, and is widely applied in the production of large-scale integrated circuits. With the rapid development of IC integration, devices assembled using BGA technology generally have greater complexity. However, BGA defects can seriously affect device performance and bring difficulties to product quality inspection. More importantly, in the process of BGA defect inspection, the high complexity of the device brings unprecedented challenges to the precise location of defects, which means that corresponding inspection methods should be improved. To this end, this paper proposes an automatic detection method for BGA defects based on x-ray imaging. First, x-ray imaging technology is utilized to achieve non-destructive detection of the BGA area inside the device and generate image data. On this basis, a set of algorithms including threshold separation, detection filling, and closing operation is designed to complete automatic detection of BGA defects. Furthermore, to objectively evaluate the effectiveness and performance of the proposed method, we conduct a series of comparative experiments using simulated and real data, and generate visual outputs. Through these experiments and analyses, we confirm that the proposed method plays an active and effective role and has robust performance in BCA defect detection. In particular, our method shows the expected performance in precisely finding BGA edge defects and subtle defects. (C) 2022 Optica Publishing Group
We introduce an imaging-based passive on-axis technique for measuring the distance of individual objects in complex scenes. Two axially separated pupil positions acquire images (can be realized simultaneously or seque...
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We introduce an imaging-based passive on-axis technique for measuring the distance of individual objects in complex scenes. Two axially separated pupil positions acquire images (can be realized simultaneously or sequentially). Based on the difference in magnification for objects within the images, the distance to the objects can be inferred. The method avoids some of the disadvantages of passive triangulation sensors (e.g., correspondence, shadowing), is easy to implement and offers high lateral resolution. Due to the principle of operation it is especially suited for applications requiring only low to medium axial resolution. Theoretical findings, as well as follow-up experimental measurements, show obtainable resolutions in the range of few centimeters for distances of up to several meters.
In this work, a quantum imageprocessing algorithm is developed using the edge extraction method together with the Kirsch operator. In our approach, novel enhanced quantum representation (NEQR) is employed as the imag...
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In this work, a quantum imageprocessing algorithm is developed using the edge extraction method together with the Kirsch operator. In our approach, novel enhanced quantum representation (NEQR) is employed as the image representation model for processing quantum image, which generates results of edge extraction using the Kirsch operator. The proposed algorithm can perform real-time imageprocessing with high accuracy. We carry out the design, analyses, and simulations of quantum circuits based on our approach, which shows that the imageprocessing speed and acuracy are much better than the classical edge extraction algorithms. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
We introduce an optical and a digital averaging technique that considerably improves edge localization performance. Especially for high quality images, the optical method achieves measurement uncertainties down to lev...
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We introduce an optical and a digital averaging technique that considerably improves edge localization performance. Especially for high quality images, the optical method achieves measurement uncertainties down to levels of millipixels. The approach uses an optical replication scheme based on a computer-generated hologram to reduce noise and discretization errors. The second method is based on a neural network denoising architecture and is especially suited for high levels of photon noise. Edge localization can be improved by up to 60% while preserving high lateral and temporal resolution. The methods are first tested using high quality images obtained by a scientific CMOS sensor imaging a razor blade mounted on a mechanical stage. Then, the laboratory results are tested for larger distances to validate the methods for building deformation measurements.
Around 177,757 people worldwide lose their lives to oral cancer each year, the most prevalent type of head and neck cancer. A 75-90% chance of survival for oral cancer is achieved with early identification. However, t...
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Terahertz waves are electromagnetic waves located at 0.1-10 THz, and terahertz imaging technology can be applied to security inspection, biomedicine, non-destructive testing of materials, and other fields. At present,...
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Terahertz waves are electromagnetic waves located at 0.1-10 THz, and terahertz imaging technology can be applied to security inspection, biomedicine, non-destructive testing of materials, and other fields. At present, terahertz images have unclear data and rough edges. Therefore, improving the resolution of terahertz images is one of the current hot research topics. This paper proposes an efficient terahertz image super-resolution model, which is used to extract low-resolution (LR) image features and learn the mapping of LR images to high-resolution (HR) images, and then introduce an attention mechanism to let the network pay attention to more information features. Finally, we use sub-pixel convolution to learn a set of scaling filters to upgrade the final LR feature map to an HR output, which not only reduces the model complexity, but also improves the quality of the terahertz image. The resolution reaches 31.67 db on the peak signal-to-noise ratio (PSNR) index and 0.86 on the structural similarity (SSIM) index. Experiments show that the efficient sub-pixel convolutional neural network used in this article achieves better accuracy and visual improvement compared with other terahertz image super-resolution algorithms. (C) 2022 Optica Publishing Group .
The refractive index of the scintillation crystal is a key parameter in the design of Positron Emission Tomography (PET) devices. However, existing methods to measure the refractive index always suffer from problems s...
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The refractive index of the scintillation crystal is a key parameter in the design of Positron Emission Tomography (PET) devices. However, existing methods to measure the refractive index always suffer from problems such as the complexity of optical path adjustment, long time cost, or high equipment consumption. To overcome these problems, we propose a method that can obtain the refractive index of the scintillation crystal with high accuracy in real time. In this method, we employ the Mach-Zehnder interferometer to generate the interference pattern when one beam of light passes through the scintillation crystal, which encodes the value of refractive index into the width of pattern. To obtain the width of interference pattern, we calculate the width pixels of dark/bright stripes in pattern with threshold, respectively, and finally get the average number of pixels of the pattern;this strategy can eliminate the coherent interference signal and random noise effectively. The optical path need not adjust during the whole measurement. Thus, the refractive index of scintillation crystals can be measured with reliability and efficiency. To validate the effectiveness of the proposed method, we measure different batches of BGO crystal and Ce:LYSO crystal samples. The results show that the proposed method can measure refractive indices with high accuracy and high efficiency, providing a reliable crystal refractive index measurement procedure for the PET detector module design. The proposed method is also suitable for refractive index measurements of transparent materials in visible light bands.
Solar and wind energy systems, without storage, cannot satisfy variable load demands, but their combined use can help to solve the problem of the balance between generation and consumption. Energetic complementarity s...
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Solar and wind energy systems, without storage, cannot satisfy variable load demands, but their combined use can help to solve the problem of the balance between generation and consumption. Energetic complementarity studies are useful to evaluate the viability of the use of two or more renewable energy sources with high variability in a specific interval of time in a determined region. In this paper, the monthly energetic complementarity study of solar and wind resources of Colombia is carried out. A novel approach to conduct the study is proposed. A dataset with the average monthly solar radiation and wind speed values is obtained from high-resolution images of renewable resources maps, using image processing algorithms. Then, the dataset is used to calculate the energetic complementarity of the sources employing the negative of the Pearson correlation coefficient. The obtained values are transformed to energetic complementarity maps, previously eliminating the protected areas. The obtained results show that there is a good energetic complementarity in the north and northeastern regions of the country throughout the year. The results indicate that projects related to the joint use of solar and wind generation systems could be developed in these regions.
A self-supervised pretext task is developed based on flow profile and motion extraction for cell detection in a lensless imaging flow cytometer. It reduces the annotation burden, automatically selects usable frames, a...
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