ISSN:1071-0922    

DOI:10.1889/1.1985107

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—The effects of etchant specific gravity (Baumé), temperature, and etch time upon etch factors for shadow masks made from aluminum killed (AK) steel were examined utilizing ferric chloride spray etching. Etch factors are initially high at small depths of etch or etch deltas and gradually decrease, becoming constant as etching progresses. Etch factors are Baumé‐ and temperature‐dependent when the AK steel is etched roughly, whereas they are independent of Baumé and temperature for smoothly etched steel. A multiple‐step etching process was developed based on these etch factor studies. In multiple‐step etching, two substantially different etching conditions are used to produce quality shadow masks with higher productivity than can be realized by using eith

ISSN:1071-0922    

DOI:10.1889/1.1985108

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—Retinal‐illuminance distributions are the inputs of vision and of vision models, yet there has not until now been a model to compute retinal‐illuminance distributions from externally measured luminance distributions. The problematic part of the luminance‐to‐illuminance transformation is that retinal illuminance is proportional to pupil diameter, and pupil diameter has not been connected analytically to the spatiotemporal distribution of light. To remedy this deficiency, the present paper outlines a pupil‐diameter model that is currently part of an image‐quality metric. The model, a generalization of the model of Trezona with dynamics adapted from Stark, allows easy computation of retinal illuminance from measured luminance distributions in s

ISSN:1071-0922    

DOI:10.1889/1.1985109

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—The apparent size of a simple stimulus was measured in order to quantify the effect of viewing distance on the perception of real (i.e., uncollimated) CRT imagery. The viewing distances tested were those used in several operational, real‐image flight simulators. All identifiable distance cues to object distance except for ocular vergence and accommodation were eliminated. For six observers, it was found that perceived size changed significantly with changes in stimulus distance between 800 cm and either 61 cm or 94 cm, or vice versa. The data are consistent with the changes in perceived size reported for other stimuli and viewing conditions, and suggest that simulator imagery presented within about 1 m of the observer must be magnified by 15–25% in order to provide size cues consistent with those provided by objects located at optical infinity. For two of the six observers, measured vergence levels were consistent with the viewing distances tested, whereas measured accommodation levels were less than expected. Thus, at least for these two observers, it appears that differences in the level of ocular vergence were primarily responsible for the observed changes in perceived

ISSN:1071-0922    

DOI:10.1889/1.1985110

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—This paper proposes a novel binocular‐disparity three‐dimensional (3‐D) display with accommodative compensation (3DDAC) to achieve fatigue‐free viewing. The display principle is based both on detecting gaze points and moving the display screen to the gaze depth in real time. Gaze detection is discussed with respect to whether eyeball rotation occurs or not, and screen motion is discussed with respect to whether the screen is real or a virtual image. In an experimental setup, a 3‐D computer‐graphics image was produced to evaluate the accommodation effect. The gaze position was fixed at the center of the field of view, and the display depth was controlled by az‐buffer value of the pixel focused on. The display screen was then moved, as a virtual image, by back‐and‐forth movements of a relay lens. It was determined that the perceived sharpness of the image increased for the pr

ISSN:1071-0922    

DOI:10.1889/1.1987395

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—When moving images are displayed on matrix displays which reproduce gray levels utilizing pulse‐number/width‐modulation techniques, degradation of the gray levels and colors are often observed. The degradation originates from a temporal non‐uniformity of the light‐emission pattern, which is transformed into a spatial non‐uniformity of the light emission due to an after‐image effect of the eyes, which follow the image motion. The degradation becomes appreciable when the product of the speed of the viewing point on a screen and the light‐emission period of a pixel is greater than the pixel pitch. The degree of degradation is also affected by the pixel arrangement; disturbances for the stripe arrangement are worse than those for the triangle arrangement. The temporal uniformity is degraded when the major light‐emitting blocks of the pulse‐number/width‐modulation change. The uniformity can be improved by dividing the blocks of the major bits. It was analytically verified that the perceived luminance of periodic light emission is proportional to the emission duty factor (which coincides with Talbot‐Plateau's law) and also to the integral off(t)dtfrom zero to infinity, independent of decay shape,f

ISSN:1071-0922    

DOI:10.1889/1.4731175

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—Results on fluorescent transient and photoconductivity measurements in Ce3+‐doped thiogallate materials are presented. Lifetime measurements were performed using a combination of time‐resolved photon counting and laser techniques on both cold‐pressed powder and melt‐grown crystal materials. The photoconductivity measurements were performed on the melt‐grown crystal at both room and liquid‐nitrogen

ISSN:1071-0922    

DOI:10.1889/1.4731176

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—Excitation spectroscopy and photoluminescence investigations have been carried out to evaluate the luminescence properties of SrS:Ce‐based thin films. The results are compared with those obtained on efficient powders. The application of a model developed for cathodoluminescence leads to the assumption that the defect density in the thin films is much higher than in powders. These defects act as killers leading to a reduced photoluminescence yield. The nature of the defects is not clearly identified; however, Ce doping‐induced Sr vacancies are proposed as possible candidates. As a consequence, Mn co‐doping has been applied, leading to a significantly improved PL and EL performance of the luminescent layers. An EL efficacy of 1.8 lm/W at 1‐μC/cm2transferred charge and 60‐Hz driving frequency has b

ISSN:1071-0922    

DOI:10.1889/1.4731177

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—The chemical bonding state of Ce in un‐doped and oxygen‐doped Ca0.55Sr0.45Ga2S4: Ce has been investigated with x‐ray photoelectron spectroscopy (XPS). The XPS analysis shows that the Ce in the un‐doped and the oxygen‐doped samples has a (+3) valence state. However, the oxygen‐doped XPS spectra have substantially larger low‐energy shoulders on the Ce 3d peaks. The low‐energy shoulders correspond to a charge‐transfer state of Ce (i.e., (5d6s)04f23d9O[S]2p5[3p5]) which suggests that the charge‐transfer state is more favorable for the oxygen ligandvs.the sulfur ligand. Thermodynamic calculations predict that the replacement of Ce‐S bonds with Ce‐O bonds is thermodynamically possible. Electroluminescent (EL) emission spectra were taken for un‐doped and oxygen‐doped samples and show that the peak emission shifts to lower wavelengths (blue shift) with increasing oxygen concentration. It is suggested that oxygen ligands locally change the ionicity of the Ce+3luminescent centers which shifts the emission to lower wavelengths accordin

ISSN:1071-0922    

DOI:10.1889/1.4731178

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract—The time‐resolved electroluminescence, EL spectrum, UV‐ and blue‐excited photoluminescence, and transferred charge of high‐efficiency blue SrS:Ce ac‐driven thin‐film electroluminescent (ACTFEL) devices were measured over the temperature range of 15–300K. The purpose of this work was to determine the mechanisms of both optical and electrical excitation/de‐excitation in these structures. We found that two thermally activated processes, a strong one around 100K and a weaker one around 200K, drastically reduce the Ce3+luminescent efficiency and limit the overall EL performance. Even though the total transferred charge increases with temperature, these two thermal de‐activation processes wipe out any luminescent gains due to increased transferred charge. The fact that a large trailing‐edge emission still exists at 15K indicates that space charge in the form of ionized Ce3+atoms caused by field‐induced delocali

ISSN:1071-0922    

DOI:10.1889/1.4731179

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY