Optical Acquisition System Research Articles

Solar position detection method by bionic polarized light compass.

To address the needs of polarized light navigation for accurate position information of feature points in the sky, an accurate solar position detection method based on an all-sky polarization pattern imaging system is proposed. Unlike the traditional spot-based solar position detection method, this method uses the polarization information inherent in the atmosphere to accurately measure solar position. This approach is characterized by simple detection, high accuracy, and wide application range. The optical acquisition system is composed of three miniature large-field camera modules and polarizers, which enables a more compact structure, smaller size, and lesser height. Based on this principle, the solar position solution algorithm was simulated and then verified in various weather environments using the optical acquisition system built as part of this study. Solar position was detected at different moments on the same day in clear weather, and the accuracy of the measured solar altitude and azimuth angles was 0.024° and 0.03°, respectively. The accuracy of the measured solar altitude and azimuth angles was 0.08° and 0.05°, respectively, when the sun was shielded by high-rise buildings and 0.3° and 0.1° when the sun was shielded by branches and tree leaves. Aerosol concentrations exceeding a certain amount destroyed the Rayleigh distribution pattern of polarized light, thus affecting solar position detection accuracy. It is concluded that this novel detection method can not only meet the needs of polarized light navigation for solar position, but also provide a new exploration idea for enthusiasts who are eager to explore the mysteries of the universe.

Trichel pulse characteristics and mechanism of negative corona discharge in sub-millimeter gaps

A negative corona discharge system of a needle-plate electrode suitable for sub-millimeter gaps is established to investigate Trichel pulse characteristics of negative corona discharge, in which an optical acquisition system is especially applied to timely observe a discharging corona. Electrostatics–hydrodynamics coupling simulations of air discharging in 100 μm-gaped needle-plate electrodes are performed to elucidate the micro-physical process of negative corona discharge. The impact ionization coefficient used for simulations and the experimentally recorded images of discharge corona are combined to characterize the active region of secondary electron emission. Dynamical distribution and transport of the charged particles are analyzed from multiphysics simulations to explain the microscopic mechanism for various stages of Trichel pulses. Even though the corona front near the plate electrode maintains a high rate of collision ionization and secondary electron excitation, the needle tip corona has not reached the threshold electric field of electron avalanche required for glow discharge, as manifested by discharge sawtooth waves comprised of corona and glow components. The amplitude and frequency of Trichel pulses increase, respectively, with impact ionization and secondary electron emission, which is evidently dependent on attachment coefficient and anion mobility. A higher attachment coefficient will lead to a significant reduction in amplitude of Trichel pulses. The present study provides a theoretical basis and experimental verification for micrometer discharges, which is the key point of insulation protections in microelectromechanical systems.

Drop Jump Performance Improves One Year Following Anterior Cruciate Ligament Reconstruction in Sportsmen Irrespectively of Psychological Patient Reported Outcomes

Our study aims to prospectively report the functional outcomes of 31 sportsmen following anterior cruciate ligament (ACL) reconstruction, up to 12 months after surgery, with regards to subjective tests and drop jump performance, and to investigate the correlations between these variables, to be used for determining the return to sports after ACL reconstruction. Lysholm score, Tegner activity level, and the ACL-Return to Sport after Injury (ACL-RSI) scale were evaluated preoperatively, at 6 months, and at 12 months after surgery. Drop vertical jump was recorded using an infrared optical acquisition system. Lysholm and ACL-RSI scores significantly improved at the 12-month follow-up compared to the baseline and 6-month evaluations (p < 0.001). Concerning Tegner activity level, no statistically significant differences were reported between pre- and post-operative status (p = 0.179). Drop jump limb symmetry index significantly improved at 12 months, with the mean value improving from 76.6% (SD: 32,4) pre-operatively to 90.2% (SD: 14.7; p < 0.001) at follow-up. Scarce positive correlation was reported between the ability to perform drop jumps and activity level in athletes one year after ACL reconstruction. In addition, subjective knee score and psychological readiness were not related to jumping performance.

Assessment of STI dry etch process variability by means of dynamic time warping technique

Numerical data of two in situ optical acquisition systems were used in machine learning algorithm to evaluate an shallow trench isolation dry etch process in a dataset of more than 200 etched wafers processed during a year. Though overall recipe performance was according to specifications, the observed parameter fluctuations were characterized to check for correlation patterns in processing data by means of machine learning. Thus, dynamic time wrapping was used to analyze time series datasets to get characteristics of minimum distance’s path between signals coming of each individual wafer. Such metrics of distances could help clustering groups of wafers that appear to be in proximity. Out of eight analyzed channels, we observed the largest distance variability was in the Si main etch for spectral reflectometer dataset, which we compared to optical emission spectroscopy channels. Based on correlation assessment of distances to the etch depth uniformity data, we showed that the selected approach is a good means to analyze time series datasets of e.g. dry etch processes for monitoring process stability.

Relationships between Jumping Performance and Psychological Readiness to Return to Sport 6 Months Following Anterior Cruciate Ligament Reconstruction: A Cross-Sectional Study.

Investigating the relationship between functional capacity and psychological readiness is of paramount importance when planning sport resumption following knee surgery. The aim of this study was to prospectively assess clinical and functional outcomes in athletes 6 months after primary anterior cruciate ligament (ACL) reconstruction and to evaluate whether jumping ability is related to psychological readiness to return to sport following ACL surgery. Patients who underwent ACL reconstruction were prospectively enrolled and evaluated pre-operatively and 6 months after surgery. Assessment included Lysholm score, International Knee Documentation Committee (IKDC) Subjective Knee Form, Tegner activity level, and the ACL-Return to Sport after Injury (ACL-RSI) scale. Jumping ability was instrumentally assessed by an infrared optical acquisition system using a test battery including mono- and bipodalic vertical jump and a side hop test. Patients were dichotomized by ACL-RSI into two groups: group A (ACL-RSI &gt; 60), and group B (ACL-RSI &lt; 60). Overall, 29 males and two females from the original study group of 37 patients (84%) were available for clinical evaluation. Mean age at surgery was 34.2 years (SD 11.3). Mean body mass index (BMI) was 25.4 (SD 3.7). Mean overall Lysholm, IKDC, and ACL-RSI scores increased from pre-operatively (p &lt; 0.001). No differences in Tegner score were reported (p = 0.161). Similarly, improvement in most variables regarding jumping ability were observed at follow-up (p &lt; 0.05). According to ACL-RSI, 20 subjects were allocated in group A (ACL-RSI &gt; 60), while 11 were allocated in group B (ACL-RSI &lt; 60). A statistically significant difference in favor of patients in group A was recorded for the post-operative Lysholm and Tegner score, as well as Side Hop test LSI level (p &lt; 0.05), while a trend for IKDC was observed without statistical significance (p = 0.065). Patients with higher values of ACL-RSI scores showed better functional and clinical outcomes as well as improved performance 6 months after ACL reconstruction.

C-rate related diffusion process of the graphite electrode by in situ experiment and analysis

The diffusion process and mechanism play important roles in the lithium storage performance of electrode materials, which directly affects the electrochemical performance of lithium-ion batteries. In this paper, we propose an in situ experimental method based on the phase evolution to observe the diffusion process. An optical acquisition system with an electrochemical battery as the core was constructed. Using the electrochromic characteristics of graphite electrodes, the phase evolution information is displayed in real time. Based on the above experimental method, diffusion process observation experiments at different charge/discharge rates (C-rates) were carried out, and it was found that there was a rate-dependent corresponding relationship among the potential, phase transition, and lithium content. The results show that a high C-rate accelerates the phase evolution process, reduces the formation potential of the new phase, shortens the duration of the phase transition, and results in a multiphase coexistence state in the electrode. In addition, the effect of acceleration induced by a high C-rate on the diffusion process in the electrode is staged: the early and middle acceleration is significant, but the later acceleration is slow. From the perspective of the energy, this is because there is competition between the diffusion-driving energy and the energy barrier. Therefore, optimization with a balance between the battery capacity and lithiation rate is proposed.

Pantograph Arc Detection of Urban Rail Based on Photoelectric Conversion Mechanism

According to the solar-blind characteristic of the pantograph arc spectrum distribution, an arc detection method based on the photoelectric conversion mechanism for urban rail was proposed, and the design of each part of the arcing detection system was completed. Through the analysis of arc spectral distribution, the 275-285 nm band was determined as the detection characteristic waveband. The optical acquisition system located on the roof of the train collects the arc characteristic light and transmits it to the photoelectric conversion module, which converts the received optical signal into the corresponding current signal linearly. After amplification, comparison and screening in this module, the optical signal is sent to the data processing module for output display. Finally, a field test conducted on an urban rail transit line shows that this arc detection system can effectively detect the pantograph arc phenomenon and reflect the arc intensity linearly avoiding the influence from natural light, train load and train running direction.

Glare removal as an ill-conditioned problem

Glare is always present in optical acquisition systems, such as photocameras or the eye-bulb. As a consequence, images captured by sensors do not represent an accurate reproduction of the scene, but rather a combination of scene content and glare. We discuss the reasons why this unwanted addition of spread light cannot be removed from an acquired image. To this aim, we cast the problem of glare-removal into an estimation task and focus on the aspects that make the unfolding of glare an ill-posed or ill-conditioned problem—such as nonlinearity, information loss, or eye model uncertainty. For each mechanism of glare formation, we point to the corresponding influence in terms of ill-posedness and ill-conditioning of the problem. We do not aim at proposing or reviewing solutions to the glare problem but rather at identifying more precisely the challenges it poses.

Cost Effective Quality Assessment in Industrial Parts Manufacturing via Optical Acquisition

We tackle the problem of dimensional verification via optical acquisition systems in the context of industrial manufacturing processes. Optical methods for quality inspection play a crucial part in the transition process to industry 4.0 and, despite the lack of international standardization, several solutions are available to industries that need to provide dimensional verification to their customers. Unfortunately most of these solutions are still economically unavailable to the majority of small or medium companies. In this paper we present an optical system based on low-cost components and we demonstrate that it provides useful and reliable information in quality inspection procedures.

Effects of a Body-Weight Supporting Kite on Sprint Running Kinematics in Well-Trained Sprinters.

Data of elite sprinters indicate that faster athletes realize shorter ground contact times compared with slower individuals. Furthermore, the importance of the so-called "front side mechanics" for elite sprint performance is frequently emphasized by researchers and coaches. Recently, it was demonstrated that using a body-weight supporting kite during full-effort sprints in highly trained sprinters leads to a reduction in ground contact time. The aim of this study was to investigate possible negative effects of this body-weight supporting device on sprint running kinematics, which was not clarified in previous studies. Eleven well-trained Austrian sprinters performed flying 20-m sprints under 2 conditions: (a) free sprint (FS); and (b) body-weight supported sprint (BWS). Sprint cycle characteristics were recorded during the high-speed phase by a 16 camera 3D-system (Vicon), an optical acquisition system (Optojump-next), and a high-speed camera. Paired sample t-tests and Cohen's d effect size were used to determine differences between sprinting conditions. Compared with FS, BWS caused a decrease in ground contact time by 5.6% and an increase in air time by 5.5% (both p < 0.001), whereas stride length and rate remained unchanged. Furthermore, a reduced hip joint extension at and after take-off, an increased maximal hip joint flexion (i.e., high knee position), and a smaller horizontal distance of the touchdown to the center of gravity could be observed (all p < 0.01). These results indicate no negative effects on front side mechanics during BWS and that sprinting with a body-weight supporting kite seems to be a highly specific method to reduce ground contact time in well-trained sprinters.

Surface reconstruction from microscopic images in optical lithography.

This paper presents a method to reconstruct 3D surfaces of silicon wafers from 2D images of printed circuits taken with a scanning electron microscope. Our reconstruction method combines the physical model of the optical acquisition system with prior knowledge about the shapes of the patterns in the circuit; the result is a shape-from-shading technique with a shape prior. The reconstruction of the surface is formulated as an optimization problem with an objective functional that combines a data-fidelity term on the microscopic image with two prior terms on the surface. The data term models the acquisition system through the irradiance equation characteristic of the microscope; the first prior is a smoothness penalty on the reconstructed surface, and the second prior constrains the shape of the surface to agree with the expected shape of the pattern in the circuit. In order to account for the variability of the manufacturing process, this second prior includes a deformation field that allows a nonlinear elastic deformation between the expected pattern and the reconstructed surface. As a result, the minimization problem has two unknowns, and the reconstruction method provides two outputs: 1) a reconstructed surface and 2) a deformation field. The reconstructed surface is derived from the shading observed in the image and the prior knowledge about the pattern in the circuit, while the deformation field produces a mapping between the expected shape and the reconstructed surface that provides a measure of deviation between the circuit design models and the real manufacturing process.

Sprint Running With a Body-Weight Supporting Kite Reduces Ground Contact Time in Well-Trained Sprinters

It is well founded that ground contact time is the crucial part of sprinting because the available time window to apply force to the ground diminishes with growing running velocity. In view of this knowledge, the purpose of this study was to investigate the effects of body-weight support during full-effort sprints on ground contact time and selected stride parameters in 19 Austrian male elite sprinters. A kite with a lifting effect combined with a towing system to erase drag was used. The subjects performed flying 20-m sprints under 3 conditions: (a) free sprint; (b) body-weight supported sprint-normal speed (BWS-NS); and (c) body-weight supported sprint-overspeed (BWS-OS). Sprint cycle characteristics were recorded during the high-speed phase by an optical acquisition system. Additionally, running velocity was derived from the 20-m sprint time. Compared with the fastest free sprint, running velocity, step length, and step frequency remained unchanged during BWS-NS, whereas ground contact time decreased (-5.80%), and air time increased (+5.79%) (both p < 0.001). Throughout, BWS-OS ground contact time (-7.66%) was reduced, whereas running velocity (+2.72%), air time (+4.92%), step length (+1.98%) (all p < 0.001), and step frequency (+1.05%; p < 0.01) increased. Compared with BWS-NS, BWS-OS caused an increase in running velocity (+3.33%), step length (+1.92%) (both p < 0.001), and step frequency (+1.37%; p < 0.01), whereas ground contact time was diminished (-1.97%; p < 0.001). In summary, sprinting with a body-weight supporting kite appeared to be a highly specific method to simulate an advanced performance level, indicated by higher running velocities requiring reduced ground contact times. The additional application of an overspeed condition led to a further reduction of ground contact time. Therefore, we recommend body-weight supported sprinting as an additional tool in sprint training.

Detecting Fabric Defects with a Neural Network Using Two Kinds of Optical Patterns

In this work, we present a new direct approach to automatic fabric inspection based on an optical acquisition system and an artificial neural network (ANN) to analyze the acquired data. Defect detection and classification are based both on gray levels and 3D range profile data of the sample. These patterns are simultaneously fed into a feed-forward neural network without further transformation. The ANN is trained to classify three different categories: normal fabric, defect with a marked 3D component, and defect with no 3D component. The good classification rate obtained shows that the double set of patterns acquired basically includes relevant information on the textile sample. Since no further transformation of the data is needed before classification, the response of this system can be very fast and thus suitable for on-line monitoring of fabric defects at a high inspection rate.

Decentralized Fiber Optic Acquisition System

The paper describes a decentralized data acquisition system installed for a long term on-site test at a French power plant. Two local autonomous stations acquire the information from 24 channels ; the data are continuously transmitted to a concentrator through two 600 m long optical cables at a rate of 0.96 Mbits/sec.. An error ratio lower than 10” on transmission, made possible through the use of optical fiber, allows testing to be performed in an industrial environment using only very simple error detection technique. The optical cables which follow interchangeable paths inside and outside the station, and operate in a temperature range of between -20°C and +60°C, are operational transmission media, which, during testing on large sites, eliminate the constraints related to the location of central computer facilities.