查看更多>>摘要：In order to meet the requirements of high-precision measurement, the method of improving camera calibration is studied. In the calibration process, the quality of the calibration image, the extraction accuracy of the calibration image corner and the nonlinear optimization effect of the camera linear parameters directly affect the calibration accuracy. First of all, in order to solve the problems in image acquisition, especially in the case of over exposure, an adaptive gamma correction method is designed to automatically adjust the image brightness, and enhance the contrast of black and white grid to improve the image acquisition quality. Secondly, a sub-pixel corner extraction algorithm based on homography matrix mapping is designed, which overcomes the error and omission of Harris corner extraction algorithm, and improves the accuracy of corner extraction. At last, adaptive weight and mutation particle swarm optimization algorithm are studied to optimize the camera parameters. Compared with other optimization algorithms, this optimization algorithm needs less parameter settings, fast convergence speed, and can obtain more accurate camera parameters. The average calibration error is 0.038 pixels.
查看更多>>摘要：A smartphone integrated microfluidic lab-on-chip device was developed for the real-time detection, counting and sizing of living algae in simulated ballast water samples. The device consists of a microfluidic chip, a customer made fluorescence imaging platform and a smartphone. When living algae pass the laser illumination region of the microfluidic chip, chlorophyll fluorescence is emitted and shown in the smartphone. An algorithm in the smartphone detects, counts and sizes the detected living algae. As a proof of concept, two different sizes of algae were tested and a detection accuracy of larger than 92% was achieved. The sizing accuracy is 94%. The largest moving velocity allowed for detection is determined by the diameter of the algae and the frame per second (fps) of the smartphone. The device is simple in structure and operation and suitable for on-site evaluating the living status of algae in treated ship's ballast water.
查看更多>>摘要：Acoustic microscopy has found various applications from nondestructive testing (NDT) to medical imaging for quantitative information. Scanning acoustic microscope (SAM) used for imaging and sample preparation have significant bearing on the conclusions drawn. In most cases while scanning the sample, there appear lots of artifacts due to the presence of an inclination offset between the focal plane and the sample surface, which often leads to wrong conclusions. In this paper, we have demonstrated a novel algorithm which can correct this offset in post-processing, which contributes to more accurate quantitative information and qualitatively better images of the sample. The correction is performed for both the amplitudes as well as the time-of-flight. The proposed algorithm was tested in simulation as well as through experimentation for sensitivity and accuracy. The results are presented and they indicate significant correction of inclination with small error margins. The application of these algorithms can be found in real-time image processing a lot of industries as well as in research.
查看更多>>摘要：Integration of graphene with the existing fabrication lines may be possible only if the growth process fulfills the high purity requirements of the front-end-of-line integration approaches. While many analytical techniques may provide information about the concentration of contaminants, their dimensional sensitivity is usually poor and thus it is not possible to assess which contaminants are located above/below graphene and which are incorporated into its structure. In this work, an optimized secondary ion mass spectrometry measurement procedure that combines excellent detection limits (0.8-2.9 ppm) and subnanometer depth resolution is presented. It confirms the presence of sodium and sulfur at the surface of the graphene layer, the formation of graphene-copper composite, and allows the detection of molybdenum and tungsten at the interface between graphene and the germanium substrate. Such precision may prove to be valuable for further optimization of the growth process of 2D materials.
Brown, Richard J. C.Janssen, Jan-TheodoorWright, Louise
3页
查看更多>>摘要：There has been a significant quantity of debate recently about how metrology and the SI should embrace the emerging societal and scientific trends of digitalisation and the open data movement. Much of this discussion has focussed on 'how' this transition will be implemented, and recent conferences and significantly advanced this understanding (International Bureau of Weights and Measures, 2021 [1]). However, there has been little if any reflection on 'why' this transition is required. This deficiency is worth addressing to provide the evidence base for the 'why' and so drive forward faster progress with the 'how'. Analogy is drawn between the recent revision of the SI and the need to provide a similar step change in end users' experience of the benefits that digitalisation should bring.
查看更多>>摘要：On-machine areal surface topography measuring instruments are required for fast and accurate measurement of parts inside production machines without reducing production rates. This paper presents the design and development of a compact focus variation microscopy sensor that can be integrated into various types of machine tools. The paper focuses on the development of the linear stage of the sensor, which was the major engineering challenge. The overall developed sensor has dimensions of 78 mm diameter and 200 mm length, with a 20 mm travel range. Simulations of tolerance stack-ups for the sensor assembly were performed before the manufacturing of the sensor's linear motion components to assure they can be appropriately assembled. The linear motion accuracy of the sensor is 2 mu m, calibrated using laser interferometry. From measurement in a controlled laboratory, the measurement noise of the sensor is 0.4 mu m. Finally, demonstrations of calibrated artefact measurements with the sensor are presented. A single image field measurement with the sensor requires less than 20 s.
查看更多>>摘要：The plane motion that composed of dynamic displacement and angle is the basis of six-degree-of-freedom motion, and its accurate measurement is especially important for the applications of inertial navigation, pose estimation, and bridge structural healthy analysis. Currently, the commonly used measurement strategies include the laser interferometry, grating ruler-based method, and sensor-based method. However, they are always difficult to accomplish the high-accuracy and efficiency measurement in a broad low-frequency range due to the limitation of their performances. In this study, a monocular vision-based method is investigated to measure the plane motion, which can get the displacement and angle as well as orbit simultaneously by using the Zernike moment method with sub-pixel accuracy and decoupling model. The measurement uncertainties of dynamic displacement and angle are 0.266% and 0.098 degrees, and the resolutions can highly reach to 0.1 um and 0.0001 degrees, respectively. Comparison experiments with the laser interferometry and circular grating method demonstrate the investigated method can accomplish high-accuracy displacement and angle measurements in the ranges of 0.05-20 Hz and 0.001-10 Hz. Meanwhile, the different plane motion orbits can also be measured by the investigated method.
查看更多>>摘要：Coherent LIDAR is a potential and effective technology to detect and identify space debris. However, for the highspeed space debris, the large Doppler frequency shift (DFS) generated by high-speed relative motion challenges the bandwidth of the photoelectric detection system and increases the difficulty of data sampling and processing. In this paper, we propose an effective method to compensate this large DFS adaptively by using an optical phase locked loop (OPLL), and thus the relative velocity between the target and LIDAR platform can be obtained. A laboratory experiment for moving targets with our OPLL method has been conducted, and it revealed that our method worked well to compensate for 64 MHz frequency difference, thus the relative velocity is about 26 m/s based on the compensated DFS. And the beat frequency is always locked to the reference frequency, while the DFS generated by variable speed motion is compensated adaptively. The proposed compensation method could improve the performance of coherent LIDAR significantly, especially when detecting high-speed target.
查看更多>>摘要：Aimed at the problems of strong dependence on target and light conditions in vision-based methods, a new method of analyzing bridge vibration by tracking a laser stripe is proposed. Specifically, the laser line is projected to the surface of the beam and continuous images are recorded. Through sub-pixel tracking of the laser stripe center-line position in the image, the bridge displacement time-history curve can be obtained, and then the dynamic parameters can be identified. A hammer impact test of a simply supported beam model was conducted in the laboratory. A Sony camera, a linear variable differential transformer displacement sensor, and seven accelerometers were used to collect data. The maximum error of displacement and maximum error of the first- and second-order frequencies obtained by the camera were 5.47% and 1.81%, respectively. Then, field tests of a track beam were conducted. This method provides a new non-contact technique for measuring bridge vibration.
查看更多>>摘要：In this paper, delay and Doppler parameters of multiple moving targets are estimated by exploring Compressed Sensing (CS) which enables the reconstruction of a sparse signal from a small set of measurements. No Side lobes appear with CS and hence no false alarms can occur. Also closely spaced targets could be detected with high resolution than traditional Matched Filter (MF). Deterministic DFT measurement matrix is employed, that is multiplied with the received echo signal and down sampled to obtain compressed measurements. For this deterministic sub-sampling is done by choosing first m rows rather than random selection of rows (random subsampling), so that matrix can be regenerated during reconstruction without the necessity for storage. Reconstruction algorithm Step Wise regression using False Discovery Rate (SWFDR) stopping rule could effectively optimize noise that leads to reduction in storage space and high rate ADC requirement drastically even in the presence of noise.
NSTL
Elsevier