Philips Journal of Research最新文献

The basic mechanism of electron transport in vacuum through insulating structures is discussed. The transport is based on a self-regulating secondary electron emission process. A general description of the transport process is presented. Three methods to model steady-state transport are briefly reviewed. The features are discussed in the light of application in displays. Also, non-steady-state effects and the role of space charge are addressed.

It is shown that the overall performance of Zeus displays is quite good, as illustrated by photographs of operating panels displaying ‘CRT-quality’ TV pictures. Results of measurements of all relevant performance parameters are presented, as well as an analysis of these data in relation to the design and operation of the displays. Measurements of the luminance as a function of the screen current density and of the screen voltage of Zeus displays are reported. A white D₆₅ luminance of 1000 Cd/m² is obtained at a screen voltage of 4.5 kV and a screen current density of about 9 μA/cm². The luminous efficacy of the phosphor screen in the panels is found to be 12 lm/W (in the absence of saturation) for white D₆₅. The efficacy of a 17″ Zeus panel (including transport power dissipation, cathode heating power and addressing power) is about 4 lm/W. The factors determining the internal contrast and colour purity of Zeus panels are discussed. Experiments to determine the relevant contrast parameters are described as well as the results of direct measurements of the internal contrast, colour purity and colour selectivity. Internal contrast values of more than 1000 have been obtained, and a colour selectivity better than 700. The available colour gamut is close to that of CRTs. Preliminary measurements of the external contrast of 17″ panels with a black matrix and front glass with 50% optical transmission yield a contrast value of 60 at an ambient light level of 100 lux. The factors determining the picture uniformity in Zeus displays are discussed. Several panels with good uniformity have been realized. No artefacts associated with moving pictures occur, the only significant artefact is caused by charge transfer effects. The visibility of this effect can be sufficiently reduced by using suitable ‘flush’ pulses and by optimizing the geometry. The displays used for the performance measurements have a quincunx dot arrangement and dot pitches 0.5 × 0.6mm, giving PAL resolution on 28″ panels. Small experimental panels with pitches of 0.3 × 0.5 mm and 0.25 × 0.30 mm have been realized and operate satisfactorily. The viewing angle of Zeus displays is close to 180 degrees. Preliminary tests show that lifetimes well over 10,000 h are possible if the glass surfaces hit by electrons are covered with an MgO coating and if the blue phosphor is coated with a very thin calcium polyphosphate layer.

In this paper an introduction is given to secondary electron emission properties. It is shown that the reduced secondary emission yield $\text{δ}\text{δ}{}_{\mathrm{m}}$ as a function of the reduced primary energy $\text{E}{}_{\mathrm{p}}\text{E}{}_{\mathrm{m}}$ can be described by a universal curve. It is found that it is easier to use the measurement of the maximum secondary electron emission δ_m and the energy E_m at which this maximum is reached to determine the suitability of a coating for use in the display than direct measurement of the first crossover energy E_I. The value of δ_m and E_m can be used to derive E_I. Furthermore, it is observed that in any material the elastic fraction of the secondary electrons exhibits a universal behaviour as a function of E_p. Fits to δ(E_p) and the energy distribution of the secondary electrons are proposed which can be used in Monte Carlo simulations.

In the coming years, the current analog television distribution will be replaced by digital distribution. Standards for digital transmission via satellite and cable have been developed for this purpose, and a standard for digital terrestrial is on its way. In this paper, the technical details of digital terrestrial television broadcasting will be described.

An automatic silicon wafer direct-bonding apparatus, a vacuum stack-bonding apparatus, a parallel polishing machine and a method for measuring a high level of parallelism of silicon wafers are described. These items are essential to wafer preparation and geometrical quality control for direct-bonding applications.

Attention is then turned to silicon direct-bonded to a second compound, which presents a wealth of feasible or potential applications, such as silicon-on-silicon for a permeable-base transistor; silicon-on-insulator, prepared for special silicon integrated circuit applications. In addition, silicon bonded to metal, to interdiffusing solids, to superconductors, diamond, a ferroelectric and to polymers for various (potential) applications is discussed.

The possibilities of fabricating integrated optical components on an InP substrate are demonstrated by a number of devices that have been made in recent years. These components can have a major impact on evolving communication networks by facilitating new techniques for increasing capacity such as wavelength division multiplexing and soliton transmission.

Four examples of direct bonding in non-silicon applications will be considered. Fusing, locally by laser scribing or integrally by annealing, gives an increased bond strength, since a chemical reaction or interdiffusion process takes place at the interface. Direct bonding of magnetic materials is a special case due to the contribution of magnetic forces to the bond strength. This process has been used to design an optimized axial-field motor. Direct bonding of an optical-fibre plate and a fluorescent-garnet substrate makes it possible to achieve an electron-microscopic detector with a high resolving power. A polymer direct-bonded to a superfinish-polished metal can be used in an x-ray reflector as a surface-protective element.

This paper gives an overview of the Philips Research system for continuous-speech recognition. The recognition architecture is based on an integrated statistical approach. The system has been successfully applied to various tasks in American English and German, ranging from small vocabulary tasks to very large vocabulary tasks and from recognition only to speech understanding. Here, we concentrate on phoneme-based continuous-speech recognition for large vocabulary recognition as used for dictation, which covers a significant part of our research work on speech recognition. We describe this task and report on experimental results. In order to allow a comparison with the performance of other systems, a section with an evaluation on the standard North American Business news (NAB²) task (dictation of American English newspaper text) is supplied.

This article describes the Philips automatic train timetable information system which enables the user to call up accurate information about train connections between 1200 German cities over the telephone. In contrast to most of the inquiry systems available so far, the caller can talk to our system in unrestricted, natural and fluent speech, very much like talking to a human operator. No instructions are given beforehand.

The system consists of four main components: speech recognition, speech understanding, dialogue control, and speech output. They are separated into independent modules and executed sequentially. The speech recogniser creates a word graph from the spoken input. This word graph is then passed to the understanding component which computes the meaning, using an attributed stochastic context-free grammar. A dialogue manager analyses the results and either accesses the database or comes up with another question if necessary.

The system has been made available to the general public in an ongoing field test, both to gather speech data and to evaluate its performance.