Digital Processing Technology Research Articles

Large angle nonmechanical laser beam steering at 4.6 μm using a digital micromirror device

Large angle, nonmechanical beam steering is demonstrated at 4.62 μm using the digital light processing technology. A 42-deg steering range is demonstrated, limited by the field-of-view of the recollimating lens. The measured diffraction efficiency is 8.1% on-axis and falls-off with a sin2 dependence with the steering angle. However, within the 42-deg steering range, the power varied less than 25%. The profile of the steered laser beam is Gaussian with a divergence of 5.2 mrad. Multibeam, randomly addressable beam steering, is also demonstrated.

Optical diffraction tomography with fully and partially coherent illumination in high numerical aperture label-free microscopy [Invited

Quantitative label-free imaging is an important tool for the study of living microorganisms that, during the last decade, has attracted wide attention from the optical community. Optical diffraction tomography (ODT) is probably the most relevant technique for quantitative label-free 3D imaging applied in wide-field microscopy in the visible range. The ODT is usually performed using spatially coherent light illumination and specially designed holographic microscopes. Nevertheless, the ODT is also compatible with partially coherent illumination and can be realized in conventional wide-field microscopes by applying refocusing techniques, as it has been recently demonstrated. Here, we compare these two ODT modalities, underlining their pros and cons and discussing the optical setups for their implementation. In particular, we pay special attention to a system that is compatible with a conventional wide-field microscope that can be used for both ODT modalities. It consists of two easily attachable modules: the first for sample illumination engineering based on digital light processing technology; the other for focus scanning by using an electrically driven tunable lens. This hardware allows for a programmable selection of the wavelength and the illumination design, and provides fast data acquisition as well. Its performance is experimentally demonstrated in the case of ODT with partially coherent illumination providing speckle-free 3D quantitative imaging.

Sensors break out of the lab

Sensors break out of the lab

Discussion of Visual Technique for Seepage Experiment Based on Transparent Rock-Soil Material

Introduction:Due to the fact that the model experiment can simulate the flow process and movement law of fluid during the seepage experiment, seepage model experiment was widely applied to study the hydraulic characteristics of rock-soil mass and transportation of ground water and pollutants. While due to the opacity of the model medium in traditional seepage experiment, the flow process, diffusion law and occurrence state of fluid can not be observed intuitively during the experiment.Method:A new technique of seepage model experiment based on transparent rock-soil material (TRSM) was introduced in this paper, combined with optical observation method, digital imaging process technology and tracer technique, so as to realize the visual observation of seepage process.Results:The advantages and disadvantages compared with the traditional experiment were analyzed and the theoretical foundation for carrying out the seepage experiment based on TRSM was established.

High-speed high-accuracy three-dimensional shape measurement using digital binary defocusing method versus sinusoidal method

This paper presents our research findings on high-speed high-accuracy three-dimensional shape measurement using digital light processing (DLP) technologies. In particular, we compare two different sinusoidal fringe generation techniques using the DLP projection devices: direct projection of computer-generated 8-bit sinusoidal patterns (a.k.a., the sinusoidal method), and the creation of sinusoidal patterns by defocusing binary patterns (a.k.a., the binary defocusing method). This paper mainly examines their performance on high-accuracy measurement applications under precisely controlled settings. Two different projection systems were tested in this study: a commercially available inexpensive projector and the DLP development kit. Experimental results demonstrated that the binary defocusing method always outperforms the sinusoidal method if a sufficient number of phase-shifted fringe patterns can be used.

Distributed Piezoelectric Sensor System for Damage Identification in Structures Subjected to Temperature Changes.

Structural health monitoring (SHM) is a very important area in a wide spectrum of fields and engineering applications. With an SHM system, it is possible to reduce the number of non-necessary inspection tasks, the associated risk and the maintenance cost in a wide range of structures during their lifetime. One of the problems in the detection and classification of damage are the constant changes in the operational and environmental conditions. Small changes of these conditions can be considered by the SHM system as damage even though the structure is healthy. Several applications for monitoring of structures have been developed and reported in the literature, and some of them include temperature compensation techniques. In real applications, however, digital processing technologies have proven their value by: (i) offering a very interesting way to acquire information from the structures under test; (ii) applying methodologies to provide a robust analysis; and (iii) performing a damage identification with a practical useful accuracy. This work shows the implementation of an SHM system based on the use of piezoelectric (PZT) sensors for inspecting a structure subjected to temperature changes. The methodology includes the use of multivariate analysis, sensor data fusion and machine learning approaches. The methodology is tested and evaluated with aluminum and composite structures that are subjected to temperature variations. Results show that damage can be detected and classified in all of the cases in spite of the temperature changes.

Butt Welding of 2205/X65 Bimetallic Sheet and Study on the Inhomogeneity of the Properties of the Welded Joint

The explosively welded 2205 duplex stainless steel/X65 pipe steel bimetallic sheets were butt jointed by multilayer and multi-pass welding (gas tungsten arc welding for the flyer and gas metal arc welding for the transition and parent layers of the bimetallic sheets). The microstructure and mechanical properties of the welded joint were investigated. The results showed that in the thickness direction, microstructure and mechanical properties of the welded joint exhibited obvious inhomogeneity. The microstructures of parent filler layers consisted of acicular ferrite, widmanstatten ferrite, and a small amount of blocky ferrite. The microstructure of the transition layer and flyer layer consisted of both austenite and ferrite structures; however, the transition layer of weld had a higher volume fraction of austenite. The results of the microhardness test showed that in both weld metal (WM) and heat-affected zone (HAZ) of the parent filler layers, the average hardness decreased with the increasing (from parent filler layer 1 to parent filler layer 3) welding heat input. The results of hardness test also indicated that the hardness of the WM and the HAZ for the flyer and transition layers was equivalent. The tensile test combined with Digital Specklegram Processing Technology demonstrated that the fracturing of the welded joint started at the HAZ of the flyer, and then the fracture grew toward the base metal of the parent flyer near the parent HAZ. The stratified impact test at −5 °C showed that the WM and HAZ of the flyer exhibited lower impact toughness, and the fracture mode was ductile and brittle mixed fracture.

AUTOMATIC TREE DATA REMOVAL METHOD FOR TOPOGRAPHY MEASUREMENT RESULT USING TERRESTRIAL LASER SCANNER

Abstract. Recently, laser scanning has been receiving greater attention as a useful tool for real-time 3D data acquisition, and various applications such as city modelling, DTM generation and 3D modelling of cultural heritage sites have been proposed. And, former digital data processing were demanded in the past digital archive techniques for cultural heritage sites. However, robust filtering method for distinguishing on- and off-terrain points by terrestrial laser scanner still have many issues. In the past investigation, former digital data processing using air-bone laser scanner were reported. Though, efficient tree removal methods from terrain points for the cultural heritage are not considered. In this paper, authors describe a new robust filtering method for cultural heritage using terrestrial laser scanner with "the echo digital processing technology" as latest data processing techniques of terrestrial laser scanner.

Aplicaţii ale unor tehnologii aditive în medicina dentară

Aim. Untill now CAD/CAM technologies meant exclusively milled dental restorations. With the development of 3D. Printing technologies they are penetrating in the medical field. The purpose of this paper is to illustrate the application of additive technologies in dentistry. Materials and methods. On a maxillary first molar preparation two metal copings were made for fixed metal-ceramic partial restorations using additive technologies: Direct MetalLaser Sintering (DMLS) and Selective Laser Melting (SLM). Digital light processing technology (DLP) was used to produce a surgical guide for insertion of a post-extraction dental implant and also for a long-term temporary restoration. Results. Innovative additive technologies used in dental technology shows numerous advantages over classical technologies slip-casting and milling procedures for alloys and polymerization for resin materials, resulting prosthetic parts with a different internal structure, faster, with less cost, with a huge development potential. Conclusions. The benefits of using CAD/CAM technology includes reduced treatment time, superior accuracy and precise visualization of the final result of the treatment.

High-Speed CMOS Frequency Dividers with Symmetric In-Phase and Quadrature Waveforms

Frequency dividers are used in frequency synthesizers to generate specific frequencies or clock (CK) waveforms. As consequences of their operating principles, frequency dividers often produce output waveforms that exhibit duty cycles other than 50%. However, some circuits and systems, including dynamic memory systems and data converters, which accommodate frequency divider outputs, may need symmetric or 50%-duty-cycle clock waveforms to optimize timing margins or to obtain sufficient timing reliability. In this review paper, design principles and methods are studied to produce symmetric waveforms for the in-phase (I) and quadrature (Q) outputs of high-speed CMOS frequency dividers with design considerations from the logic gate level down to the transistor level in terms of speed, reliability, noise, and latency. A compact and robust multi-gigahertz frequency divider with moduli 12, 14, and 16 to provide I and Q outputs with 50% duty cycle is proposed and designed using a 90-nm digital CMOS process technology with 1.2-V supply.

A novel approach for custom three-dimensional printing of a zirconia root analogue implant by digital light processing.

This study aimed to explore the feasibility of fabrication of three-dimensional (3D)-printed zirconia root analogue implant (RAI) through digital light processing (DLP) technology. One partially edentulous mandibular human cadaver was scanned with a cone-beam computed tomography (CBCT) system. The scan volumes and data sets were used to create computer-aided design (CAD) model of the RAI. A high-end DLP 3D printing technology was used to fabricate the RAI from the CAD model. Within this approach, solid 3D objects are built using a DLP projector to translate voxel data so it is reproduced in liquid photopolymer dispersed with a commercial ceramic, thereby light polymerizing the resin to solid. Optical scanning technology was used to measure the tooth and 3D-printed RAI. To validate the accuracy of the printed zirconia RAI, the optical surface model of the original tooth and CAD model were superimposed. The differences between the optical scans of the RAI and original tooth are most noticeable towards the apical foramen, showing a disparity for the RAI with a maximum deviation of 0.86mm. When setting a maximum threshold of 0.5mm for the 3D-printed RAI surface to be deviating from the original tooth model and CAD model, measurements show 1.55% and 4.86% of the surface areas are exceeding the threshold distance, respectively. With the use of currently available technology, it is well feasible to 3D print in zirconia a custom RAI.

Single pass fiber laser butt welding of explosively welded 2205/X65 bimetallic sheets and study on the properties of the welded joint

In this study, the explosively welded 2205 duplex stainless steel/X65 pipe steel bimetallic sheets were butt welded by a fiber laser in single pass. The microstructure, mechanical, and corrosion properties of the laser butt welded (LBW) joint were investigated. The results show that the upper fusion zone (FZ) is composed of the martensite and bainite phases, while the lower FZ is composed of austenite (A) and ferrite (F). Energy dispersive spectroscopy (EDS) test results indicate that only a small amount of Cr, Ni, and Mo migrated from the lower FZ to the upper FZ, whereas a small amount of Fe has been moved from the upper FZ to the lower FZ. During the tensile test process, The digital specklegram processing technology test results demonstrated that the fracturing of the specimens started at the lower FZ, and then the fracture grew towards the parent plates near the upper FZ. The face and root bend tests were carried out, and no separation, tearing, or fracture was observed around the joint. Accelerated corrosion test results show that the LBW joint has the superior corrosion resistance, but it has poor pitting corrosion resistance.

Digital Control System for the MEMS Tuning Fork Gyroscope Based on Synchronous Integral Demodulator

This paper presents a demodulation algorithm based on the synchronous integrator circuit for the MEMS tuning fork gyroscope utilizing the digital processing technology. The synchronous integral demodulator (SID) is adopted to demodulate the drive-detection signal and sense-axis output signal separately. Combining with automatic gain control and phase-locked loop technology, the closed-loop control of drive mode has been implemented, and high precision output of the gyroscope has been achieved. The simulation results have verified the effectiveness of the synchronous integrator circuit, which is in good agreement with the theoretical analysis. Compared with other demodulation algorithms, the SID has the advantages of the lower noise level, a better ability to attenuate the harmonics, and the best hardware efficiency. The frequency characteristic of the synchronous integrator is also analyzed, which is vital to the bandwidth of gyroscope. The print circuit board based on field-programmable gate array digital circuit is manufactured and the corresponding experiment is carried out. The experimental results show that the SID algorithm of digital control system for the gyroscope developed in our laboratory has achieved a good performance. The bias instability of tested gyroscope is measured to be 0.2°/h with the angle random walk of 0.14°/ $\surd \text{h}$ and the nonlinearity of the scale factor is <60 ppm with the measurement range of ±100°/s.

Tailoring light with a digital micromirror device

A digital micromirror device (DMD) is a product of micromechanics. The DMD employs numerous micromirrors as the actuating components to switch small portions of light on and off. During the past few decades, such devices have been widely applied in digital light processing technology. The expanding range of applications makes the DMD increasingly important in various research aspects. Recent advances demonstrate that the DMD is potentially better than the traditional liquid crystal spatial light modulator in speed, spectrum sensitivity, and polarization modulation. These characteristics have been verified in a series of recently reported experiments. This review summarizes the related theory, experimental techniques, and applications for wavefront shaping with DMDs in both statically shaping various spatial modes and dynamically compensating for wavefront distortion caused by the scattering medium. image

Thermal Debinding of Ceramic-Filled Photopolymers

Within the large variety of different additive manufacturing technologies stereolithography excels in high precision and surface quality. Using the Digital Light Processing (DLP) Technology a stereolithography-based system was developed, which is specifically designed for the processing of highly filled photopolymers.The powder-filled suspension enables the 3D-fabrication of a so called ceramic green part. In order to get a dense ceramic structure, subsequent thermal processing steps after the 3D-printing process are necessary. First, the polymer-ceramic composites heated up to 400°C. During this processing step, called debinding, the organic components are burned out. The resulting part, consisting of powder particles stabilized by physical interactions, is further heated to sinter the particles together, and the final, fully dense ceramic part is obtained.The debinding step is the most critical process. The used components have different evaporation or decomposition temperatures and behaviors. Thereby a reduction in weight and also in dimension occurs, which depends on the portion and composition of the organic components and especially on the temperature cycle. Furthermore, the physical characteristics of the ceramic powder, such as the particle size and the size distribution influence the debinding behavior. To measure the changes in weight and dimension a thermo-gravimetric (TGA) and a thermo-mechanical analysis (TMA) can be used. To avoid too high internal gas pressures inside the green parts a preferably constant gas evolution rate is seeked. Also the ‘surface-to-volume ratio’ affects the debinding characteristics. Therefore, optimized debinding cycles for specific geometries allow the crack-free debinding of parts with a wall thickness up to 20 mm.

Ways of improving the accuracy of digital aerial photography by the railway transport inventory

The development of railway sector around the world has always been a vital issue, as it plays important social, financial and economical role and influences the development of the country a lot. Because of constant growth and modernizing of the railway sector all processes and items of land and property fund have to be monitored. On the basis of the world experience, trends in the development of methods and technologies of area mapping it has been established that for the inventory of land and property fund objects cartographic material at 1 : 500 or 1 : 1000 scales suits the most. With the large amounts of work (for example area of mapping and number of railroad objects) it is reasonable to use digital aerial photography and technology of digital data processing, in particular methods of digital photogrammetry. In order to increase the accuracy of creating the cartographic component, the authors suggest, when choosing the parameters of aerial photography, taking into account spatial resolution of camera system, its geometrical properties, the influence of external factors and first of all the atmospheric refraction. It has been proved that by highly precise aerial photography the accuracy of fixation of angular elements of camera orientation with the help of Inertial Navigation Systems (INS) may be insufficient. Therefore it is recommended to thicken core network using block phototriangulation. This paper presents the description and results of experimental work, which helped to create cartographic material from digital images at 1 : 3000 scale with an accuracy of 4–5 cm, which fully meets the requirements for holding inventory, monitoring, maintenance, design and construction.

STRUCTURE AND TECHNOLOGY OF THE NUMERICAL RELAY PROTECTION IN THE POWER SYSTEMS

Abstract. Numerical relays permit development of new functions as well as development of adaptive relaying schemes. Digital relays, providing flexibility to the user and to electromagnetic and static relays are superior advanced microprocessors, and economic empowerment, increased attention to the supply and use of microprocessor-based protective relays were. This paper introduces the technology of power system relay protection. Refers to the generation of protective relays and upgrade them and eventually to relay the new generation of digital signal processing technology deals.

Untrimmed Low-Power Thermal Sensor for SoC in 22 nm Digital Fabrication Technology

Thermal sensors (TS) are essential for achieving optimized performance and reliability in the era of nanoscale microprocessor and system on chip (SoC). Compiling with the low-power and small die area of the mobile computing, the presented TS supports a wide range of sampling frequencies with an optimized power envelope. The TS supports up to 45 K samples/s, low average power consumption, as low as 20 μW, and small core Si area of 0.013 mm2. Advanced circuit techniques are used in order to overcome process variability, ensuring inaccuracy lower than ±2 °C without any calibration. All this makes the presented thermal sensor a cost-effective, low-power solution for 22 nm nanoscale digital process technology.

Graphic User Interface for Memory Polynomial Based Digital Pre-Distortion of RF Power Amplifiers

The availability of fast and cost effective digital processing technology makes digital pre-distortion attractive for power amplifier linearization since it promises high power efficiency and flexibility. Digital pre-distortion task can be divided into three sub tasks: modeling of the power amplifier (PA), adaptive identification of the model parameters, and development of the pre-distorter. The memory polynomial model, which is reduced form of Volterra series, is most widely used by researchers. The accuracy of memory polynomial based digital pre-distortion depends on the memory depth and order of memory polynomial. In this work a generalized graphic user interface has been developed for modeling of power amplifier and digital pre-distorter. The memory depth and order of memory polynomial can be changed and experimentation can be done for different values of memory depth and order of memory polynomial.

Seeing through a mask

seeing through a mask