High-resolution Charge-coupled Device Research Articles

Gamma Scientific Sets High Standards for Light Measurement

Gamma Scientific Sets High Standards for Light Measurement

Automatic Tunnel Crack Inspection Using an Efficient Mobile Imaging Module and a Lightweight CNN

Cracks in tunnel linings are the most common tunnel defects. As early indicators of structural deterioration, cracks represent critical problems for the safety of tunnels. Several mobile tunnel inspection systems (MTISs) have been developed for tunnel crack inspection. However, due to the weak signals of cracks, these MTISs require considerable exposure time to capture high-quality tunnel images, necessitating a low travel speed. Meanwhile, traditional crack detection methods encounter difficulties in processing tunnel crack images because of their low contrast and poor continuity. To overcome these challenges, this study presents a new MTIS for fast tunnel crack inspection that consists of a novel mobile imaging module and an automatic crack detection module. The imaging module is composed of an array of high-resolution charge-coupled device (CCD) cameras, a mobile laser scanner, and a lighting array. The core of the crack detection module is a novel lightweight convolutional neural network (CNN) designed for efficient tunnel crack detection, with an effective spatial constraint strategy to guarantee crack continuity. We collected a new tunnel crack dataset consisting of 1,218 images using our mobile imaging module at a driving speed of 80 km/h. Comprehensive experiments were conducted on this dataset to evaluate the performance of our proposed network. The results demonstrate that the presented CNN can effectively detect tunnel cracks with state-of-the-art performance, achieving an F1-score greater than 0.88 and an inference speed of 17 FPS with only 3.4M model parameters. The code and data are available at <uri xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">https://github.com/urban-informatics/LinkCrack</uri> .

Parametric Study of Proton Acceleration from Laser-Thin Foil Interaction

We experimentally investigated the accelerated proton beam characteristics such as maximum energy and number by varying the incident laser parameters. For this purpose, we varied the laser energy, focal spot size, polarization, and pulse duration. The proton spectra were recorded using a single-shot Thomson parabola spectrometer equipped with a microchannel plate and a high-resolution charge-coupled device with a wide detection range from a few tens of keV to several MeV. The outcome of the experimental findings is discussed in detail and compared to other theoretical works.

High-resolution Three-dimensional Surface Imaging Microscope Based on Digital Fringe Projection Technique

Abstract The three-dimensional (3-D) micro-scale surface imaging system based on the digital fringe projection technique for the assessments of microfiber and metric screw is presented in this paper. The proposed system comprises a digital light processing (DLP) projector, a set of optical lenses, a microscope, and a charge coupled device (CCD). The digital seven-step fringe patterns from the DLP projector pass through a set of optical lenses before being focused on the target surface. A set of optical lenses is designed for adjustment and size coupling of fringe patterns. A high-resolution CCD camera is employed to picture these distorted fringe patterns. The wrapped phase map is calculated by seven-step phase-shifting calculation from these distorted fringe patterns. The unwrapping calculation with quality guided path is introduced to compute the absolute phase values. The dimensional calibration methods are used to acquire the transformation between real 3-D shape and the absolute phase value. The capability of complex surface measurement for our system is demonstrated by using ISO standard screw M1.6. The experimental results for microfiber with 3 μm diameter indicate that the spatial and vertical resolutions can reach about 3 μm in our system. The proposed system provides a fast digital imaging system to examine the surface features with high-resolution for automatic optical inspection industry.

Research progress on solidification structure of alloys by synchrotron X-ray radiography: A review

Abstract The synchrotron radiation technology has recently emerged as a powerful tool to characterize the real-time microstructure evolution during solidification of alloys. Compared with other methods, the synchrotron radiation technology, along with its unique advantages of strong brightness, high energy, excellent resolution, and good monochromaticity, allows for capturing the dendrite evolution behavior of alloys in real time and can be dynamically coordinated with high-resolution CCD (Charge-coupled Device) imaging systems. This paper briefly reviews the recent advances in developing synchrotron radiation for solidification of alloys with low, medium, and high melting points, and under the external electric, magnetic, and ultrasonic fields. Furthermore, a series of microstructural features and behaviors such as dendrite morphology, growth orientation, dendrite fracture, and rotation are described in detail. Finally, the development trends and application prospects of synchrotron radiation technology in alloy solidification are forecasted.

Design of a high frame rate driver circuit for a 22 M-pixel high-resolution large-area array CCD camera and its nonuniformity correction

When using a high-resolution full-frame area array charge-coupled device (CCD) FTF4052M as the aerial image sensor of a camera, the frame rate is generally below 1 frame / second (fps), which cannot meet the requirements of applications with high frame rates. First, the FTF4052M drive circuit is introduced. Next, an improved driver circuit of the CCD 4052M is proposed. Using the CCD to output four amplifiers simultaneously yielded a maximum frame rate of 3.4 fps. Then, the timing of the CCD driver, the front-end processing circuit, the DC bias circuit, and the interface circuit of the four outputs are designed. The improved driver circuit could meet the application requirements of various aerial cameras. In addition, the FTF4052M nonuniformity is analyzed, and a nonuniformity response detection system is established. Using this system, the FTF4052M array’s nonuniformity among the four quadrants and among the pixels is tested. Based on the CCD’s linear responsivity, two correction algorithms are proposed to correct the nonuniformity. Finally, using the correction, the four quadrants’ standard deviations of the response sensitivity are reduced by a factor of 1 / 13, and the responsive nonuniformity among all pixels is reduced by a factor of 1 / 10. Through the reshooting of the identified rate board, it is found that the nonuniformity of the CCD array is markedly improved.

43- and 50-Mp High-Performance Interline CCD Image Sensors

This paper describes the design and performance of two new high-resolution interline charge-coupled device image sensors for use in industrial, machine vision, and aerial photography applications. These sensors feature 4.5- $\mu \text{m}$ pixels, 4 outputs, fast dump gate, horizontal lateral overflow drain, and vertical electronic shutter. The 43-Mp sensor has a 35-mm optical format and the 50-Mp sensor has a larger format with a 2.175:1 aspect ratio that matches many modern mobile phone displays. This paper discusses the challenges and solutions to manufacture such large sensors with superior image quality such as uniformity, read noise, dark current, smear, transfer gate blooming, lag, and so on.

Uniaxial compression of calcite single crystals at room temperature: insights into twinning activation and development

Abstract. E-twinning is a common plastic deformation mechanism in calcite deformed at low temperature. Strain rate, temperature and confining pressure have negligible effects on twinning activation which is mainly dependent on differential stress. The critical resolved shear stress (CRSS) required for twinning activation is dependent on grain size and strain hardening. This CRSS value may obey the Hall–Petch relation, but due to sparse experimental data its actual evolution with grain size and strain still remains a matter of debate. In order to provide additional constraints on twinning activation and development, new mechanical tests were carried out at room temperature on unconfined single crystals of calcite, with different sizes and crystallographic orientations. Uniaxial deformation was performed at a controlled displacement rate, while the sample surface was monitored using optical microscopy and a high-resolution CCD (charge-coupled device) camera. The retrieved macroscopic stress–strain behavior of the crystals was correlated with the surface observations of the deformation process. Results show (1) the onset of crystal plasticity with the activation of the first isolated mechanical twins during the strain hardening stage, and (2) the densification and thickening of twin lamellae during the steady-state flow stress stage. Such thickening of twin lamellae at room temperature emphasizes that calcite twin morphology is not controlled solely by temperature. The different values for the CRSS obtained for the activation of isolated twins and for the onset of twin densification and thickening raises questions regarding the appropriate value to be considered when using calcite twin data for stress inversion purposes.

Surgical Anatomy of Rats for the Training of Microvascular Anastomosis

Microvascular anastomosis is an essential procedure in neurosurgery, but the opportunity to perform the surgery has gradually decreased for neurosurgeons. Therefore, training is necessary for obtaining and maintaining the skills required for the procedure. We describe the detailed anatomy of cervical and femoral regions in rats and discuss the advantages for practicing microvascular anastomosis. Cervical regions of Sprague-Dawley rats were dissected under intraperitoneal anesthesia. The step-by-step anatomic description was documented using a high-resolution charge-coupled device image sensor and recording systems. Using this model, temporal occlusion time and patency were measured, and these measures were compared between the trainee and trainer groups. The number of times the training needs to be completed to attain competency in the bypass procedure was estimated. After exposing the carotid triangle, a half-ring was created by end-to-side anastomosis. Anastomosis was performed at the common carotid artery using the contralateral side of the carotid artery as a graft. The cutoff value for the temporal occlusion time was 79.3 minutes in the receiver operating characteristic curve based on a target temporal occlusion time for beginners determined during the training. Using a living animal model, a trainee has the opportunity to learn not only anastomotic techniques but also hemostatic control as well as overcoming mental strain during surgery. Living animal models are important in training because the fidelity of a living animal model is superior to nonliving models. Applying training using a half-ring model contributes to safe and efficient surgery.

Time-of-Flight Sensor in a Book Reader System Design for Persons With Visual Impairment and Blindness

This paper integrates a time-of-flight (ToF) sensor to a high-resolution charge-coupled device camera in a new and fully automated book reader design for individuals with visual impairment and blindness. This cost-effective and portable book reader design integrates, in a unique way, a 3-D map extracted by a low-resolution ToF sensor and a high-resolution image as means to correct the page curvature of bound books. This is achieved by a seamless registration process of two imaging modalities, so that the low-resolution ( $160 \times 120$ pixels) depth map accurately reflects the entire book spread as captured by the high-resolution camera ( $3072 \times 2304$ pixels). As part of the automated registration process, the book reader will give the user a warning message if the book is misplaced within its field of view. The reading accuracy is further improved by a mathematical framework formulating the flattening and extension operations, which together optimally dewarp the book spread images. This correction process is resilient to potential misplacement of the book within the book reader platform. The testing phase led to a reading accuracy of over 95%, involving an unprecedented acquisition and processing of 200 pages. A database consisting of all the 200 high-resolution book spread images together with their respective extracted depth maps are made available to the research community for further developments.

A Static Displacement Monitoring System for VLBI Antenna Using Close-Range Photogrammetry

In this study, a static displacement monitoring program was developed to maintain the accurate performance of a Very Long Baseline Interferometry (VLBI) antenna by monitoring its structural stability. The monitoring program was designed to measure static displacement, among the many displacements of the antenna’s main reflector, which can directly affect its performance. The program measures the position of a monitored object with mm-level accuracy through close-range photogrammetry that uses high-resolution Charge Coupled Device (CCD) cameras. The developed program will be used to evaluate the structural soundness of an antenna based on continuous displacement measurements, which can also be used as basic data for repair and reinforcement work in the future.

Tomographic PIV investigation on 3D wake structures for flow over a wall-mounted short cylinder

Tomographic particle image velocimetry (TPIV) measurement with six high-resolution charge-coupled device (CCD) cameras is conducted to investigate flow structures over a finite circular cylinder with an aspect ratio of 2 ($h/d=2$). This short wall-mounted cylinder is fully immersed in a thick turbulent boundary layer ($\unicode[STIX]{x1D6FF}/h=1.025$). Focus is placed on the three-dimensional instantaneous vortex structures and their dynamic characteristics in the wake flow fields. Based on the present results, a refined topological model of the mean wake field behind the finite circular cylinder is proposed, where the spatial locations of the typical vortex structures and their interactions are described in more detail. Among the reported typical vortex structures (i.e. the horseshoe, tip, base, trailing and arch vortex), emphasis is laid on discussion of the tip and arch vortex. The instantaneous 3D M-shape arch vortex and an alternating large-scale streamwise vortex are first found in the present experiment, and their developments are also discussed. Therefore, it is suggested that the instantaneous finite-cylinder wake is dominated by the arch vortex system and the large-scale streamwise vortices. Moreover, in the instantaneous volumetric flow fields, both the antisymmetric and the symmetric wake behaviours are observed. With proper orthogonal decomposition (POD) analysis, the dynamic characteristics of the wake field are clarified. Different from the flow around an infinite cylinder without control, the third and fourth POD modes are characterized by low-frequency symmetric shedding. The low-frequency feature shown in the second mode pair is observed and associated with the occurrence of instantaneous symmetric 3D wake behaviour triggered by the low-aspect-ratio effect and the extension of the separated shear layer. The low frequency seems be attributed to the flapping phenomenon, i.e. oscillation of the recirculation in the backward-facing step flow. It is found that the flapping motion has a modulating effect on the occurrence of the antisymmetric shedding vortex and thus the large-scale streamwise vortex.

Design and Development of Instrumentations for the Preparation of Platinum Single Crystals for Electrochemistry and Electrocatalysis Research. Part 2: Orientation, Cutting, and Annealing

In this contribution, which is the second paper in a series, we report on the design and development of several pieces of equipment, which facilitate the preparation of a hemispherical single crystal with a desired crystallographic surface structure starting with a spherical Pt single crystal. The pieces of equipment include a dual, high-resolution charge-coupled device (CCD)-based camera for acquiring Laue X-ray back-scattering patterns to orient spherical single crystals, a precision custom-designed jig for cutting and polishing pre-oriented single crystals, and an induction annealing system with controlled gaseous atmosphere for obtaining well-ordered and defect-free single crystal surfaces. Firstly, the paper describes the dual CCD camera setup, which allows acquiring, processing, and analyzing Laue back-scattering patterns in a digital format. The single crystal holder comprising a goniometer, the CCD-based detection system, and an optomechanical system together allow simple, adaptable, quick, and accurate single crystal orientation. Secondly, the paper presents details of a high-precision jig used in the cutting and polishing of single crystals. The jig setup includes a goniometer supporting a holder in which a single crystal is mounted and two micrometers. It maintains the desired single crystal surface parallel to the polishing disk on which abrasive materials are dispersed and polishing cloths are mounted. The micrometers allow monitoring the polishing rate and maintaining the desired single crystal surface exactly parallel to the polishing disk. Thirdly, the paper describes details of the annealing system. It consists of an induction-annealing furnace with a custom-made coil, a custom-designed quartz cell that facilitates single crystal annealing under controlled atmosphere conditions. Optimization of the induction annealing parameters and conditions, which determine the final quality of single crystal surfaces, is described in detail. Finally, the paper explains the unique aspects of this setup and methodically describes the operating procedures required to obtain a hemispherical single crystal with an atomically flat surface.

Dynamic Mapping of Rice Growth Parameters Using HJ-1 CCD Time Series Data

The high temporal resolution (4-day) charge-coupled device (CCD) cameras onboard small environment and disaster monitoring and forecasting satellites (HJ-1A/B) with 30 m spatial resolution and large swath (700 km) have substantially increased the availability of regional clear sky optical remote sensing data. For the application of dynamic mapping of rice growth parameters, leaf area index (LAI) and aboveground biomass (AGB) were considered as plant growth indicators. The HJ-1 CCD-derived vegetation indices (VIs) showed robust relationships with rice growth parameters. Cumulative VIs showed strong performance for the estimation of total dry AGB. The cross-validation coefficient of determination ( R C V 2 ) was increased by using two machine learning methods, i.e., a back propagation neural network (BPNN) and a support vector machine (SVM) compared with traditional regression equations of LAI retrieval. The LAI inversion accuracy was further improved by dividing the rice growth period into before and after heading stages. This study demonstrated that continuous rice growth monitoring over time and space at field level can be implemented effectively with HJ-1 CCD 10-day composite data using a combination of proper VIs and regression models.

The Characterization and Coatings on 304 Stainless Steel by Laser Induced Fluorescence Spectroscopy using the High Resolution Charge Coupled Device

The Characterization and Coatings on 304 Stainless Steel by Laser Induced Fluorescence Spectroscopy using the High Resolution Charge Coupled Device

Evaluation and Detection of Dysplasia in IBD: the Role of Chromoendoscopy and Enhanced Imaging Techniques.

Patients with ulcerative colitis (UC) and Crohn's disease (CD) colitis are at significantly higher risk for the development of colitis-associated colorectal cancer (CAC), a risk associated with increased duration and extent of disease [1]. CAC in patients with ulcerative colitis and Crohn's colitis arises from dysplastic tissue in the background of mucosal inflammatory changes. Regular surveillance by colonoscopy is a recommended cancer prevention strategy endorsed by the US and European GI societies [2-4]. Until recently, random sampling of the mucosa throughout the colon has been the mainstay of this conventional surveillance. This requires multiple biopsies to be taken and processed, a practice which is time consuming, expensive, and has a low diagnostic yield. The growth pattern of dysplastic tissue is often multifocal and diffuse, and thus, its detection may not be optimal with the use of traditional white light colonoscopy. According to recent studies, most dysplastic lesions appear to be visible to careful endoscopic inspection [5-7]. Thus, the approach focusing on targeted biopsies of any mucosal abnormalities instead of only random biopsies has been advocated [8]. In addition, the detection and further delineation of any mucosal abnormalities are thought to be improved by the application of dyes that highlight more subtle abnormalities known as chromoendoscopy (CE) as well as a new generation endoscopic system with high-definition white light endoscopy (HDWL). The application of CE in patients with long-term UC was deemed to be beneficial based upon the results of previous clinical trials comparing CE with standard definition white light endoscopy (SDWL) [9•, 10•]. However, there are limited data available comparing CE with the currently broadly used high-definition colonoscopies (HDWL) [11•, 12•, 13•]. High-definition (HD) endoscopy uses a high-definition monitor and a high-resolution CCD (charge-coupled device) providing images of substantially higher resolution than standard video endoscopy. Thus, HDWL colonoscopy may be an alternative to CE in IBD surveillance without the need for the extra time and required experience with CE. Further longitudinal studies are necessary to determine the ultimate advantage of chromoendoscopy or lack of the advantages of chromoendoscopy over that of high-definition colonoscopy in detection of dysplasia. Once lesions are identified by HDWL and CE, they can be further evaluated with evolving technologies to perform in vivo microscopy. Small-field technologies such as confocal endomicroscopy (CLE) permit in vivo microscopic assessment of the colonic mucosa. This evolving technology can be utilized in combination with HDWL and CE in selected cases to further define the lesions and assess their histology, and thus, facilitate real-time in vivo diagnosis and decisions regarding resection of lesions. Further studies to determine the applicability of these newer enhanced technologies in evaluation of dysplasia in routine clinical practice are needed.

A Low-Jitter Fast-Locking Multi-phase Clock for High Resolution CCD Processor

ABSTRACTA multi-phase clock circuit for a 14 bit 80 MHz charge-coupled device (CCD) signal processor is designed based on the Delay-Locked Loop (DLL) structure. To accelerate the DLL locking time, a new fast locking controller circuit is proposed in this paper. Besides, a low jitter delay cell circuit is used to reduce the influence of the jitter generated by multiple phase clock generating circuit on the performance of correlated double sampling (CDS) and A/D conversion in the high resolution CCD signal processor. A clock signal with adjustable phase for the CCD signal processor can be obtained by changing the value of the edge selected register. The proposed clock circuit implemented and simulated with SMIC 0.18 μm 3.3 V 1P6M mixed CMOS process and the area of layout is 1000 × 350 μm. Under the condition of TT/3.3V/27 °C, the simulation results with the input clock frequency of 80 MHz show that the DLL locking time is 1.3 μs. Besides, the peak-to-peak jitter is 1.09 ps and the RMS jitter is 182 fs.

Design of a hardware/software FPGA-based driver system for a large area high resolution CCD image sensor

A hardware/software field programmable gate array (FPGA)-based driver system was proposed and demonstrated for the KAF-39000 large area high resolution charge coupled device (CCD). The requirements of the KAF-39000 driver system were analyzed. The structure of “microprocessor with application specific integrated circuit (ASIC) chips” was implemented to design the driver system. The system test results showed that dual channels of imaging analog data were obtained with a frame rate of 0.87 frame/s. The frequencies of horizontal timing and vertical timing were 22.9 MHz and 28.7 kHz, respectively, which almost reached the theoretical value of 24 MHz and 30 kHz, respectively.

Automated geometric correction of multispectral images from High Resolution CCD Camera (HRCC) on-board CBERS-2 and CBERS-2B

China–Brazil Earth Resource Satellite (CBERS) imagery is identified as one of the potential data sources for monitoring Earth surface dynamics in the event of a Landsat data gap. Currently available multispectral images from the High Resolution CCD (Charge Coupled Device) Camera (HRCC) on-board CBERS satellites (CBERS-2 and CBERS-2B) are not precisely geo-referenced and orthorectified. The geometric accuracy of the HRCC multispectral image product is found to be within 2–11km. The use of CBERS-HRCC multispectral images to monitor Earth surface dynamics therefore necessitates accurate geometric correction of these images. This paper presents an automated method for geo-referencing and orthorectifying the multispectral images from the HRCC imager on-board CBERS satellites. Landsat Thematic Mapper (TM) Level 1T (L1T) imagery provided by the U.S. Geological Survey (USGS) is employed as reference for geometric correction. The proposed method introduces geometric distortions in the reference image prior to registering it with the CBERS-HRCC image. The performance of the geometric correction method was quantitatively evaluated using a total of 100images acquired over the Andes Mountains and the Amazon rainforest, two areas in South America representing vastly different landscapes. The geometrically corrected HRCC images have an average geometric accuracy of 17.04m (CBERS-2) and 16.34m (CBERS-2B). While the applicability of the method for attaining sub-pixel geometric accuracy is demonstrated here using selected images, it has potential for accurate geometric correction of the entire archive of CBERS-HRCC multispectral images.

Nanobioceramic Composites: A Study of Mechanical, Morphological, and Thermal Properties

The aim of this study was to explore the incorporation of biomass carbon nanofillers (CNF) into advanced ceramic. Biomass from bamboo, bagasse (remains of sugarcane after pressing), and oil palm ash was used as the predecessor for producing carbon black nanofillers. Furnace pyrolysis was carried out at 1000 °C and was followed by ball-mill processing to obtain carbon nanofillers in the range of 50 nm to 100 nm. CNFs were added to alumina in varying weight fractions and the resulting mixture was subjected to vacuum sintering at 1400 °C to produce nanobioceramic composites. The ceramic composites were characterized for mechanical, thermal, and morphological properties. A high-resolution Charge-coupled device (CCD) camera was used to study the fracture impact and the failure mechanism. An increase in the loading percentage of CNFs in the alumna decreased the specific gravity, vickers hardness (HV), and fracture toughness values of the composite materials. Furthermore, the thermal conductivity and the thermal stability of the ceramic composite increased as compared to the pristine alumina.