Electromagnetic Scanning Research Articles

Large area direct-write focused ion-beam lithography with a dual-beam microscope

The authors have investigated the performance of focused ion-beam (FIB) direct-write lithography for large area (multiple write-field) patterning in an FEI Nova Nanolab 600 dual-beam microscope. Their system is configured with a 100 nm resolution X-Y stage and a RAITH ELPHY LITHOGRAPHY control interface, with its own integrated 16 bit DAC pattern generator and software. Key issues with regard to configuration, process parameters, and procedures have been addressed. Characterization of stitching errors, pattern repeatability, and drift were performed. Offset lithography (multiple exposures with offset write fields) and in-field registration marks were evaluated for correcting stitching errors, and a test microfluidic device covering an area of 1×1.4 mm2 was successfully fabricated. The authors found that by using a combination of offset lithography and in-field registration mark correction methods, the stitching errors can be kept well below 100 nm. They also found that due to higher beam deflection speed provided by the electrostatic scanning in FIB systems versus the wide-spread electron-beam systems with electromagnetic scanning, FIB lithography can be just as fast as electron-beam lithography for typical mill depths down to about 200–500 nm (material dependent). This opens the door for a large suite of applications for materials where pattern transfer is difficult or impossible by reactive methods.

Dynamic Analysis of 2D Electromagnetic Resonant Optical Scanner Using 3D Finite Element Method

The optical scanner is a scanning device in which a laser beam is reflected by a mirror that can be rotated or oscillated. In this paper, we propose a new 2D electromagnetic resonant optical scanner that employs electromagnets and leaf springs. Torque characteristics and resonance characteristics of the scanner are analyzed using the 3D finite element method. The validity of the analysis is shown by comparing the characteristics inferred from the analysis with the characteristics of the prototype. Further, 2D resonance is investigated by introducing a superimposed-frequency current in a single coil.

Development for 2-axis Electromagnetic Driving MEMS Mirror

We propose a new 2- axis electromagnetic scanning mirror that utilizes radial magnetic fields. By positioning magnets under the mirror, we were able to develop a greatly miniaturized mirror device. This device volume is 300 mm3. Moreover, the mirror driving magnetic induction can be enlarged by forming the closed magnetic field with the york and the magnets. To assemble it easily, the upper part of all magnets was assumed to be N pole. To optimize the composition of the yoke and the magnets, the magnetic induction of the space was calculated using magnetic simulation. We made the mirror using the bulk micromachining process, and did the driving experiment. The mirror scanning angle is 10 degrees at 100 mAP-P for a resonant frequency of 6 kHz, and the frame scanning angle is 1 degree at 100 mAP-P for a non-resonant frequency of 60 Hz. The calculation and the measurement result were almost the same.

Nano-positioning of an electromagnetic scanner with a MEMS capacitive sensor

This paper presents the control design and experimentation of a prototype electromagnetic X/Y scanner for small form factor probe storage. An array of probe heads is to be precisely positioned in tracking, scanning and rotation directions so that high areal density (>1 terabit/in 2) and high data throughput can be achieved. The scanner has X/Y motion capabilities with a linear stroke of about 300 μ m . It can also generate rotational motion with offset actuators to compensate for disturbances, mechanical tolerance and nonlinearities. System characterization, modeling, MIMO control design and simulation, and preliminary experimental results are presented. The feasibility of rotation control with the capacitive sensor and offset actuators is experimentally confirmed.

Nanoprecision MEMS Capacitive Sensor for Linear and Rotational Positioning

This paper presents a microelectromechanical systems (MEMS) capacitive position sensor for nanopositioning applications in Probe storage systems. The objective of the sensor system design is to develop a high-precision <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</i> linear and rotational position sensor with a minimum sensor area and a large range of movements at high speed. To achieve this, first, a simple sensor noise model scalable with a sensor area was developed, in which all the parasitic capacitances are taken into account. Furthermore, a signal-processing solution was developed to compensate for the nonlinearities caused by rotational disturbances and, at the same time, to generate a rotational position signal for active rotation-control purposes. A MEMS capacitive sensor prototype was constructed with the design of a 13-mum pitch, a 300-mum peak-to-peak linear stroke, and a 3.46-mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> sensor area at a 3-mum gap. The measured sensor noise was 0.2 nm 1sigma, which corresponds to 12 mudeg 1sigma for the fabricated prototype sensor, at 25-kHz bandwidth. Furthermore, the signal linearity was significantly enhanced by the proposed sensor signal processing, with a measured sensor signal nonlinearity of 0.78% for an 80-mum peak-to-peak stroke at 200 Hz. Finally, the capacitive sensor-based dynamic closed-loop <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</i> linear and rotational position control of an electromagnetic scanner was successfully demonstrated.

GoingStick® technology and electromagnetic induction scanning for naturally-turfed sports surfaces

This paper describes the underlying technology of the GoingStick, a ground assessment device developed by Cranfield University, UK, in collaboration with the TurfTrax Group. An analysis of the data produced from environmental characterization trials show that the GoingStick offers potential as a tool to assist in irrigation scheduling for the horseracing industry. The wider applications of the GoingStick in conjunction with electromagnetic scanning are discussed.

Localização especial de estímulos sonoros em indivíduos cegos congênitos: estudo comparativo da posição tridimensional da cabeça em adultos cegos congênitos e indivíduos videntes

A capacidade para localizar objetos fixos ou em movimento no espaço tridimensional depende da função visual. No indivíduo cego, as modalidades sensoriais remanescentes, nomeadamente a audição, poderiam compensar a visão na localização espacial. O objetivo deste estudo foi analisar o papel da audição no mecanismo de localização espacial por meio da habilidade de orientar de forma precisa a cabeça face à fonte sonora. Cinco adultos cegos congênitos foram comparados com cinco sujeitos videntes vendados. A tarefa consistiu na orientação da cabeça ao estímulo sonoro, emitido por sete fontes diferentes, com localização fixa. A posição tridimensional da cabeça e tronco foi registrada por um sistema de varredura eletromagnético (Flock of Birds System). Para cada som produzido foi calculado o "erro de localização". Esta medida correspondeu à diferença entre o registro da posição obtido durante o teste e durante uma posição de controle. Os resultados revelaram que nos indivíduos cegos congênitos a magnitude de erro de localização dos estímulos auditivos foi superior aos indivíduos videntes. Conclui-se que a representação mental formada com base na visão constitui um dos pré-requisitos para um bom desempenho nas tarefas espaciais.

Nano-Positioning of a Electromagnetic Scanner with a MEMS Capacitive Sensor

This paper presents the control design and experimentation of a prototype electromagnetic scanner with an integrated capacitive linear and rotational position sensor for small form factor probe storage. An array of probe heads is to be precisely positioned in X/Y linear and rotation directions so that high areal density (>1 terabit/in2) and high data throughput can be achieved. The scanner has X/Y motion capabilities with a linear stroke of about 300 µm. It can also generate rotational motion with offset actuators to compensate for disturbances, mechanical tolerance and nonlinearities. System characterization, modeling, MIMO control design and simulation, and preliminary experimental results are presented. The feasibility of rotation control with the developed capacitive sensor and offset actuators is experimentally confirmed.

Electromagnetic scanning in an Australian offshore basin with complex geology

Electromagnetic scanning in an Australian offshore basin with complex geology

Optimal Design of a Hybrid Winding Structure for Planar Contactless Battery Charging Platform

Planar contactless battery charging platform is an emerging technology that has the potential of unifying the charging protocols of portable consumer electronic products. In this paper, a new hybrid structure which consists of a coil and a spiral winding is proposed for improving the uniform magnetic field distribution over the charging surface. An analysis into an optimal design of the number of turns and the dimension of the spiral winding is presented for a given concentrated coil. The uniform magnetic field distribution of the designed prototype is measured by an electromagnetic compatibility scanner and by an energy-receiving coil. Based on circuit modeling and analysis, the inverter circuit topology and particularly the resonant compensation tank is designed for maximizing power transfer for multiload applications. A design procedure is proposed and verified by the experiments. An efficiency of about 80% has been achieved for the coupled structures when four loads are charged on the platform simultaneously.

GoingStick®technology and electromagnetic induction scanning for naturally‐turfed sports surfaces

GoingStick^®technology and electromagnetic induction scanning for naturally‐turfed sports surfaces

Electromagnetic Two-Dimensional Scanner Using Radial Magnetic Field

In this paper, we present the design, fabrication, and measurement results of a two-dimensional electromagnetic scanning micromirror actuated by radial magnetic field. The scanner is realized by combining a gimbaled single-crystal-silicon micromirror with a single turn electroplated metal coil, with a concentric permanent magnet assembly composed of two concentric permanent magnets and an iron yoke. The proposed scanner utilizes the radial magnetic field rather than using a lateral magnetic field oriented 45° to the horizontal and vertical scan axes to achieve a biaxial magnetic actuation. The single turn coil fabricated with electroplated copper achieves a nominal resistance of 1.2Ω. A two-dimensional scanner with mirror size of 1.5mm in diameter was fabricated. Maximum optical scan angle of 8.8° in horizontal direction and 8.3° in vertical direction were achieved. Forced actuation of the gimbal at 60 Hz and resonant actuation of the micromirror at 19.1-19.7kHz provide slow vertical scan and fast horizontal scan, respectively. The proposed scanner can be used in raster scanning laser display systems and other scanner applications.

Electromagnetic prospect scanning moves seabed logging from risk reduction to opportunity creation

Dave Ridyard, Tor Atle Wicklund, and Bjorn Petter Lindhom of Norwegian company Electromagnetic Geoservices (emgs) describe an adaptation of conventional controlled source electromagnetic surveying aimed at marine hydrocarbon exploration in frontier areas. In the past four years emgs has conducted over 200 seabed-logging surveys. This method is now well established as an effective technique for verifying the presence of hydrocarbons in prospects initially identified by seismic analysis. Surveys can be designed to measure the resistivity of subsurface bodies in a growing number of geological settings. In the hands of a skilled interpreter, survey data can help to determine whether or not a structure contains hydrocarbons and, if it does, to delineate the reservoir. A new application of this technique, known as ‘scanning’, provides a means of identifying prospects in frontier areas working only from basin-scale knowledge. In this article, we introduce the concept of scanning and discuss some of the issues concerning survey design and application. What is scanning? The traditional approach to exploring a frontier area requires considerable effort in seismic imaging and drilling before there is any real evidence that hydrocarbons are present. In contrast, electromagnetic (EM) prospect scanning identifies prospective areas much earlier in the process. By acquiring data from a grid of seabed-logging receivers, areas containing significant resistive anomalies can be identified, and exploration efforts can then be focused on those leads. An exploration workflow that includes EM prospect scanning in this way can dramatically reduce the overall time and effort required to find a new reservoir. The difference between scanning and a conventional sea-bed-logging survey is that scanning data is acquired on a relatively sparse grid (compared with the typically 1 km receiver spacing used in traditional seabed logging). As a result, large areas can be scanned quickly. Because preliminary data analysis is also quite quick, it may be possible to identify potential reservoirs before the survey vessel leaves the area. This provides the option to undertake a more detailed infill characterization of the potential reservoir. Then, after seismic imaging, drilling can be targeted on the most prospective areas. This approach may reduce typical field development times by up to a year. The technique can also be applied in more mature areas to identify by-passed pay, which can extend the life of the field using existing production infrastructure. Another opportunity for the use of scanning is in areas where permits for seismic acquisition can be hard to obtain, such as areas of environmental sensitivity. Scanning is most effective when used to survey large areas, so collaboration between several oil companies and licensing authorities can create the greatest value.

Elimination of scanning electron microscopy image periodic distortions with digital signal‐processing methods

Electromagnetic interference is one of the main distortion sources in scanning electron microscopy. Electromagnetic interference-generated scanning electron microscopy image distortions are usually visible as edge blur (at low scan rates) or vibration (at high scan rates). Hardware solutions to this problem, e.g. electrostatic and magnetic shielding, are expensive and, in some cases, difficult to implement. The current investigations led to a significant decrease in the periodic distortions by a novel adaptation of software-based digital signal processing to scanning electron microscopy problems, without any hardware modification.

Polymer magnetic scanners for bar code applications

Resonant mode polymer-based electromagnetic scanners are developed for barcode reading applications. The electromagnetic scanner consists of a mirror suspended by a polymer cantilever beam, a permalloy sheet attached to the mirror, and an external coil to generate the driving magnetic field. The simple fabrication process involves polymer molding and electroplating of magnetic material, yielding inexpensive devices suitable for high volume manufacturing. Mechanical and magnetic modeling of the device as well as analytical, numerical and experimental results are presented. A barcode reading system is demonstrated successfully using this inexpensive, easy to manufacture scanner. Fabricated cantilever scanners achieve an optical θ· D product of 123° mm at 56.5 Hz, consuming an actuation power of 168 mW. 2D actuation of the cantilever scanners is also demonstrated.

TU-D-224A-07: Image-Guided IMRT and Very High Energy Electrons (VHEE)

Purpose: To evaluate the feasibility of very high-energy electron beams (VHEE, 150 – 300 MeV) for radiotherapy. The specific goal is to exploit fast scanning capabilities of pencil VHEE beams for better targeting of moving tumor tissue and moving sensitive organs in 4D image guided intensity modulated radiation therapy (IGIMRT). Method and Materials: VHEE have dosimetric characteristics comparable, and for some applications superior, to photon beams. The dosimetry of the VHEE treatments can be verified by means of Monte Carlo simulations. The dosimetry of the VHEE treatments for moving tissues requires the knowledge of body geometries in subsequent phases of cyclical motions of regions of patient body that undergo treatment. The mutual interaction of doses delivered at different phases allows for optimal treatment in 4D radiation therapy. Therefore, optimization of 4D radiation therapy involves calculating jointly the set of all intensities at all phases of the cyclical tissue motion. This in turn means that optimal 4D IGIMRT plans require delivery of intensity maps that appropriately distribute given fractions of intensity maps over particular phases of moving tissues. Existing delivery systems for IMRT therapy (step and shoot IMRT and/or DMLC IMRT) are not capable of efficient delivery of predetermined by 4D IGIMRT planning “intensity map rates”. In contrast, fast scanning beam of VHEE electrons provides ideal tool for 4D IGIMRT delivery. Results: A sequence of dose calculations for representative VHEE beams are presented and compared with traditional photon beam irradiations. Examples illustrating VHEE intensity rate maps for delivery of optimal 4D IGIMRT are presented and their delivery discussed in the context of MLC and electromagnetic pencil beam scanning capabilities of radiation devices. Conclusion: VHEE devices, capable to provide fast, electromagnetic scanning of pencil beams, are capable to efficiently deliver “intensity rate maps” of truly optimized 4D IGIMRT treatments.

193 Excimer Laser Machined Electromagnetic Optical Scanning Mirror for a Laser Projection Display

Electromagnetic optical scanning mirrors for both horizontal and vertical scanning of a Laser Projection Display have been proposed. Electromagnetic actuation is selected because of the millimeter-sized mirror. For low cost reason, the glass and PMMA films are respectively used as the main structure of horizontal and vertical scanning mirrors. A mathematical model considering the operation frequency of the Laser Projection Display has been derived to fast design the geometry of the scanning mirror. In order to machine scanning mirrors with high quality geometry, the 193 nm excimer laser is used as the major machine tool. Different control circuits have been developed to control both horizontal and vertical scanning. The scanning frequencies, 4.15 kHz and 260 Hz respectively for horizontal and vertical scanning mirrors, have been measured by laser Doppler vibrometer. Comparing to other optical scanners, 193 nm excimer laser machined optical scanning mirrors have advantages in low cost and easy to fabricate. In this paper, a Laser Projection Display consisting of the horizontal and vertical scanning mirrors has also been built to show the application potential. A 2-D single color image with resolution of 46 × 32 pixels, 4.15 kHz of horizontal scanning frequency and 60Hz of regulated vertical scanning frequency has been demonstrated.

Silicon scanning mirror of two DOF with compensation current routing

An electromagnetic scanning mirror with two DOF using a single permanent magnet is proposed. In the radial magnetic field, driving currents produce Lorentz forces about two axes of rotation. For an electromagnetic scanning mirror, it is very important to reduce the crosstalk in the current carrying lines. The scanning mirror uses compensation current routing to reduce the crosstalk and enable independent simultaneous control of each axis of rotation. Two independent current flows produce torque from the Lorentz force in the external magnetic field from a single permanent magnet under the mirror. The mirror is 3.5 mm × 3.5 mm and the movable frame 5.7 mm × 5.7 mm. The measured resonance frequency of the mirror is 2190 Hz and that of the movable frame is 920 Hz. In the resonance mode the angle of rotation of the mirror is ±1.51° for an applied ac current of 20 mArms and for the movable frame it is ±5.71° for the same current. The system has a reduced disturbance sensitivity of 9.93 × 10−6, which is the ratio of angle of rotation of the movable frame due to the mirror. The scanning mirror can be applied to conventional imaging systems, scanning systems, etc.

Near-field three-dimensional coherent imaging: Theory and simulations

This work presents a rigorous mathematical derivation of an effective approximate solution to the three-dimensional inverse scattering/imaging problem that is applicable for all imaging zones ranging from the near to the far field. Simulation results for the point spread function illustrate the range and cross-range resolution as a function of the optical f number. The model system operates in a synthetic aperture type mode, where the coherent signals are transmitted, and the scattered signals are subsequently received at individual transmitters and receivers. Potential applications of this technology include: Medical ultrasound, foliage penetrating synthetic aperture radar, ground penetrating radar for land mine detection, and electromagnetic millimeter-wave scanning for concealed weapon detection.

Development of a MEMS electromagnetic optical scanner for a commercial laser scanning microscope

A microelectromechanical system electromagnetic optical scanner for horizontal scanning in a commercial laser scanning microscope has been developed. Major specifications include mirror size: 4.5×3.3 mm2, resonant frequency: 4 kHz, changeable scan angle: 2.1-16°, mirror flatness: <244 nm, and scan angle stability: <0.1%. Initial development started with prototyping a scanner with polyimide hinge, but the stiffness and the Q-factor of polyimide hinge were found insufficient to realize the required resonant frequency and scan angle. On the other hand, a scanner with single crystal silicon hinge has been successfully developed. The electromagnetic scanner has an electroplated copper driving coil to reduce power consumption. A scanner controller using the output signal from an integrated sensing coil was also developed, and sufficient scan angle stability was obtained. The scanner has survived the life test of over 140 billion cycles. It has successfully satisfied all the specifications including not only the fundamentals such as resonant frequency and maximum scan angle but also the ones for commercial products such as scanning stability and durability. It has been commercialized as a part of our product OLS1100 (later remodeled as OLS1200).