Accuracy of various approximations to exchange and correlation for the electron density distribution in atoms and small molecules

The general usefulness of various local and non-local approximations to the exchange-correlation potential in density functional theory is studied by comparing resulting electron density distributions to essentially exact results for light atoms. The correlation contribution to the electron density in CO and H2O is compared with CI results. It is concluded that density functional theory provides a viable alternative to HF and CI approaches for the calculation of deformation densities, although the response of the electron density to the correlation potential is only moderately accurate

Electron-optics of the Fast Intelligent Tracking (F!T) tube: A CRT without a shadow mask

In this paper, we describe the electron-optics involved in realizing a maskless CRT based on tracking the electron beams along horizontally aligned phosphor lines. We discuss the boundary conditions in order for the system to function. Emphasis is placed on the requirements of color purity, beam current, and spot size. A dedicated electron gun has been designed and tested. Results indicate that the spot-size requirements for the feasibility of the concept can be met. The depth of focus, in terms of the allowed mismatch of the dynamic focusing voltage, is small. Inter-beam space-charge repulsion turns out to be unproblematic. The cathode drive is shown to lead to beam displacements that cannot be corrected. Consequently, a grid-1 drive has to be used. Keywords: CRT; tracking; electron gun; spot siz

Injecting light of high-power LEDs into thin light guides

A new method using a thin-film multilayer filter is described to couple light from high-power LEDs into a thin light guide such as an LCD backlight. Light emitted below the critical angle is reflected back to the LED and recycled. Largeangle emitted light passes the filter and is transported by total internal reflection in the light guide. The light guide can be as thin as 0.3mm for an LED of 1x1mm2, and the best coupling efficiency is estimated to be around 80%. With this approach, a backlight system can be greatly simplified but also compact collimators can be realized. In this paper the optical design and testing of the filter is described, and a 1mm thick, 6.5mm diameter collimator is presented that emits in a cone of 2x13o. Measurements on prototypes show good agreement with the designed characteristicsOptics Research GroepApplied Science

Ray-tracing simulations of liquid-crystal gradient-index lenses for three-dimensional displays

For the first time, to our knowledge, we report ray-tracing simulations of an advanced liquid-crystal gradientindex lens structure for application in switchable two-dimensional/three-dimensional (3D) autostereoscopic displays. We present ray-tracing simulations of the angular-dependent lens action. From the results we conclude that the lens action of the advanced optical design corresponds to the desired performance for small viewing angles. For oblique viewing angles of approximately 30° and higher, the lens action becomes significantly weaker compromising the 3D performance of an autostereoscopic display. The general approach and the advanced ray-optics analysis procedures presented form a useful tool in the search for improvements for high viewing angles and enable a better understanding of the liquid-crystal technology discussed.Imaging Science and TechnologyApplied Science

The Fast Intelligent Tracking (F!T) tube: A CRT without a shadow mask

The F!T tube is a new type of CRT without a shadow mask. The primary function of the mask, color selection, is taken over by an electronic control system that guides the electron beams over the correct phosphor lines. The position of the beams is detected by means of dedicated structures on the faceplate. Proof of the principle has been shown in single- and triple-beam 17- and 32-in. tubes. \Keywords: CRT;shadow mask;Fast Intelligent Tracking (F!T);F!T inde