This paper develops a Bayesian motion estimation algorithm for motion-compensated temporally recursive filtering of moving low-dose X-ray images (X-ray fluoroscopy). These images often exhibit a very low signal-to-noise ratio. The described motion estimation algorithm is made robust against noise by spatial and temporal regularization. A priori expectations about the spatial and temporal smoothness of the motion vector field are expressed by a generalized Gauss-Markov random field. The advantage of using a generalized Gauss-Markov random field is that, apart from smoothness, it also captures motion edges without requiring an edge detection threshold. The costs of edges are controlled by a single parameter, by means of which the influence of the regularization can be tuned from a median-filter-like behaviour to a linear-filter-like one.
A layered motion estimation algorithm is proposed that permits quasi-simultaneous motion estimation/segmentation up to a fixed maximum number of layers. The estimation results in one motion parameter set per layer, and a segmentation map that assigns these sets to different parts of the image (motion layers). Motion in a layer is modelled with at maximum four parameters capable of describing pan, tilt and zoom. The concept shows some hierarchy, i.e. a ranking of the motion layers. In this way the motion parameter estimation concerning one layer excludes those parts of the image that have been described by a layer ranked higher in the hierarchy and are not polluted by parts of the image that are better described by layers ranked lower in the hierarchy. The concept results in a very low operations count. It has been shown to perform well even in critical scan rate conversion applications, particularly in picture rate up-conversion. A variant including three layers has been scheduled to run in real-time on a Philips TriMedia processor.
The technology as used for passive integration is discussed. The build-up of passive components (integrated resistors, capacitors, and inductors, including interconnect) and the (eventually) following mounting and assembly technologies are described. The adaptations of the basic technology are described using a number of demonstrator examples from differ ent application fields. Depending on these application areas, different constraints are valid. This is often related to the working frequencies of the devices and the modules, or the extra assembly of active components. Some results on the material characteristics are discussed, but the emphasis is on the description of technology.
The first thin film heads produced commercially by Philips were of the so-called sensor-first type, the sensor being processed on the substrate and the remaining parts of the head being processed on top of the sensor. This design has various drawbacks in comparison with a design where the sensor is processed at the end (sensor-last), such as a higher power consumption (low head efficiency) and limitations of use of high-temperature processes/materials. However, initially, topographic structures, step coverage and problems with wet chemical etching were obstacles in realizing the sensor-last design. The introduction of planarization in wafer processing technology opened the way to the sensor-last design. The design was introduced in heads for the DIGAMAX(TM) system and showed all the expected advantages in comparison with the sensor-first design. It also offers the possibility of applying new materials in the head, an option which is necessary for realizing new generations of recording systems.
Digital tape recording systems show the same trend as hard-disk drives: a large increase of storage density with time. The use of advanced media and highly sensitive thin-film heads with magnetoresistive (MR) readout will increase the storage density dramatically. Key improvements are narrower tracks, more sensitive MR elements attained by applying the giant magnetoresistance effect, high-saturation flux density pole materials, advanced metal powder tape, intimate head-to-tape contact, and accurate tracking. By increasing the number of channels in the multitrack thin-film head, high data rates can be obtained as well. The basics of digital magnetic recording are discussed and a short historical overview is given of the Philips activities on thin-film heads for tape recording. An outlook on future improvements is given.
An outlook is given on how the efficiency of future generation yoke-type magneto-resistive read heads may be improved through the use of oxidic layers. The effect of ferrite separation oxides, ferrite fluxguides and superconducting gap-oxides is discussed.
Miniaturisation and integration of passive components play an important role in today's components market. It can be achieved by applying thin-film technologies for capacitors, resistors and inductors; high component densities have been realised with 'Passive Only Networks'. The dielectric materials used for integrated thin-film capacitors ranging from Si3N4, Ta2O5, TiO2 to earth alkaline as well as lead perovskite layers are reviewed. The capacitor performances including temperature stability, insulation resistance, breakdown fields and endurance are discussed as a function of material composition.
In order to use pre-operative images during an intervention for navigation, they must be registered to the patient's co-ordinate system in the operating theatre or to an intra-operative image. For the registration to be valid in the case of patient movements, the registration must be updated or the patient movement must be tracked. One problem in this area is the registration of intra-operatively acquired X-ray fluoroscopies with 3D CT images obtained before the intervention as well as motion tracking for this setup. The result can be used to support the placement of pedicle screws in spine surgery or aortic endoprostheses in transfemoral endovascular aneurysm management (TEAM). The different approaches to 2D/3D registration are discussed and a novel voxel-based method is presented: using a small part of the CT image covering only the vertebra of interest, pseudo-projections are computed and the resulting vertebra template is compared to the X-ray projection using a new similarity measure which is called pattern intensity. Application, performance and registration accuracy are discussed and demonstrated by application to images of a TEAM procedure and of a spine phantom.
Although Magnetic Resonance Imaging (MRI) has faced a dramatic increase in real-time capabilities over the last year, acceptable image quality still limits the actually achievable acquisition speed. This paper presents a motion-compensated noise filter that, on the basis of hierarchical motion estimation and edge-preserving adaptive weighted averaging, has been integrated into a segmented radial MR acquisition scheme. In several studies of moving joints, the proposed approach led to significant reductions in the noise level without introducing motion blur. The improved image quality would, in principle, allow more than double the acquisition speed, retaining the original image quality.
Polymer light-emitting diodes have become feasible when suitable materials were available. The various relevant properties are interrelated parameters. The solubility can be improved in various ways but here the introduction of side-chains has been found most successful. Colour tuning is achieved by attaching electron withdrawing or donating side-chains. Some polymer defects in PPV are shown. Special functionalities can be built-in. As an example a self-doped PPV is given.
The luminescence efficiency of polymer light-emitting diodes is determined by the efficiency of radiative recombination of excitons. In a joint research programme, Leiden University and Philips Research are conducting a theoretical investigation on the dynamics of excitons in conjugated polymers. This article reviews part of the results obtained so far, describing the following phenomena: spectral diffusion, electric field-induced quenching, photobleaching and defect quenching.
The sensitivity of magnetoresistive read heads can be increased by using layered magnetic materials showing the giant magnetoresistance effect, instead of a single magnetic film showing the anisotropic magnetoresistance effect. For this purpose, exchange-biased spin-valve layered structures are very suitable. For well-chosen compositions and nanometer-scale layer thicknesses these materials combine a fair giant magnetoresistance effect with a very small field interval in which the resistance change takes place. In this paper we give an overview of aspects which determine the functioning of materials of this class in read heads, including their preparation, magnetotransport properties and the magnetic interactions which determine the magnetization reversal process.
Functional polymers are increasingly being used in the electronics industry. The advantages are ease of processing, tailor-made materials and unique properties. The technology used is spin-coating of PPV derivatives which are made soluble by side chains attached to the polymer. The polymer light-emitting diode build-up is discussed as well as some typical results for brightness, efficiency and stability. On this basis, extension to application areas where larger flat devices are required, is considered. Of most direct importance are LCD backlights and displays based on the light-emitting polymer itself. Upon comparison with existing technologies, light-emitting polymers turn out to yield most promising solutions.
In this paper, we report on the lifetime of polymer LEDs fabricated at Philips Research. For single-layer LEDS, we find that the operational lifetime in nitrogen gas is limited by the stability of the indium-tin-oxide (ITO) anode. By using a polymeric capping layer for the ITO, we obtain more stable devices. In air, the lifetime is limited by black spot formation. Small pinholes in the cathode layer are the origins of the black spots. Water or oxygen may diffuse through these pinholes and react with the cathode, causing degradation. By encapsulating the devices we can prevent black spot formation. Our present 8 cm2 devices have lifetimes of many thousands of hours at daylight visibility under ambient conditions.
From the very beginning Philips has participated in inventing, developing and manufacturing semiconductor devices. In consumer electronics silicon, initially discrete, devices rapidly made electron tubes a museum curiosity. Their specific properties and the facility to be scaled down to microscopie dimensions gave rise to the development of integrated circuits and the ensuing redesigned consumer electronics and digital computer applications. Lamps were the initial products that formed, over a century ago, the basis of Philips industrial manufacturing. Today, there is hardly an application oflight for which Philips does not have a product in store. Increasingly electronic circuits are being used in the lighting set-ups and within Philips between these two synergy is not an empty word. An interesting property of semiconductor materials is that they can generate light. In a diode, made of an appropriately chosen semiconductor material and drawing a forward current, the injected electrons and holes may recombine with the emission of light. For physical reasons the material to be used for such light-emitting diodes (LED) is not silicon, but compounds of the much more difficult to handle so-called III-V materials, like GaAs, InP, or combinations of these. The colour of the emitted light depends on the combinations chosen. Philips has been actively engaged in producing such materials and inventing new combinations and manufacturing methods. In all respects Silicon beats III-V compounds and if ever it seems different, that does not last long. Secondly, it is in the nature of a semiconductor diode that it is a small device. Exploiting this facility in the direction of making ever smaller devices has been highly profitable. However, extending in the direction of much larger-areas light-generating devices like displays, would also be highly desirable. The desire to get rid of the bulky structure of a TV tube and to use a flat, thin display has always been there. Less ambitious applications include the type of smaller displays that actually use liquid crystals.
Metal-films for precision resistors combine a very low temperature dependence of the electrical resistance with a tolerance of the resistance of only 0.1%. Corrosion resistance and adhesion to the substrate are of major importance. There are different classes of materials being utilised. For low ohmic applications, we use Cu-Ni alloys with a composition of about 65 at. % (atomic percent) of Cu. For this special alloy, the low temperature coefficient of the resistance (TCR) is a stable, intrinsic property. For most alloys, however, annealing is essential to approach the state of zero TCR. This is the case for the NiCrAl alloys, used for the mid-range of resistances and for SiCrN for high ohmic applications. In high ohmic films, metals are often combined with non-metallic substances like oxides or nitrides. Variation of alloy composition, sputtering conditions and annealing procedures are important for obtaining optimum thin-film properties. Important tools for thin-film characterisation are electron microscopy and related techniques together with high-temperature resistance measurement.
The diagnostic value of medical images significantly depends on the signal-to-noise ratio (SNR). Especially in fluoroscopic tomography, the SNR is limited by the radiation dose (Computer Tomography), or by the suitable acquisition techniques (Magnetic Resonance Imaging). The purpose of this paper is to introduce a projection-based method for the motion-compensated SNR enhancement applied in Radon space. It is based on a projection-based motion estimation with subsequent motion-compensated, edge-preserving filtering of the measured projections. The effect of temporal filtering as well as spatial filtering will be presented. In contrast to the recently introduced image-based approach, this method allows a very efficient computational implementation, likely to be used in real time imaging. It will be shown that a significant increase of the SNR can be achieved without introducing additional motion artifacts or blurring in the reconstructed images. The proposed technique has the potential to be used for SNR enhancement in low-dose fluoroscopy applications in CT as well as for SNR improvements in MR fluoroscopy using projection reconstruction based techniques.
The trend of miniaturization of electronic products has had an effect on the development of passive components. A solution to the problems that are generated by size reduction of discrete passive components is to integrate resistors, capacitors and inductors into a functional passive circuit on one substrate. Various conditions have to be fulfilled in order to justify this integration. Important aspects are manufacturing cost, assembly cost, miniaturization, reliability, functionality and performance. Thin film technology can offer many advantages in all these aspects.
This paper describes the outline of a method for simulating the electromagnetic behaviour of ICs fabricated in the RF passive integration process. The theory is an extension of that used in the CAD package Fasterix. This is modified to take account of the losses and other aspects of the IC process. The new theory is then applied to the design of a power amplifier for a mobile phone handset, and the results presented demonstrate its accuracy, speed and flexibility. Further results demonstrate that use of this powerful new model can lead to improved electrical performance of real RF applications.
An improved version of motion-adapted gating useful in MR imaging is presented. Compared to other gating approaches, this advances method shows an improved ability to suppress motion artefacts at a reduced scan time. It is based on a k-space dependent weighting function and a real-time system feedback. During MR data acquisition patient motion is monitored and only those profiles are accepted whose respiratory motion induced displacements are below a pre-defined threshfold (gating) function. The displacements are measured relative to a reference position, which is automatically determined during the initial phase of the MR scan. While MR data are acquired, the object motion is statistically analysed in parallel by calculating the histogram of the displacement distribution for consecutive time intervals. This information can be used to interfere with the measurement process in the case that motion statistics changes during the scan. Initial in-vivo results are presented and compared to conventional techniques.
