VDT作业中屏面背景亮度与对比度的交互作用

VDT的亮度对比度和屏面亮度在对操作者视觉功能的影响中,存在着交互作用。VDT的最佳对比度和适宜对比度范围随屏面亮度水平而变化,提高屏面亮度可以使最佳对比度值和适宜对比度范围向低对比度端偏移。评价VDT显示质量,主观评价法具有与作业绩效指标同样的价值。     

视觉显示终端屏面亮度水平和对比度对视疲劳的影响

本实验研究了VDT不同屏面亮度与对比度对视疲劳的影响。实验中采用远近视点的眼肌调节时间变化率作指标,对VDT作业的不同时段进行视疲劳测定。屏面亮度取20、30、40Cd/m~2三种水平,对比度取3:1至15:1,分成七等。实验结果表明,在本实验所取的屏面亮度范围内:(1)9:1～11:1对比度所引起的视疲劳最轻,对比度愈趋近高低两端所引起的视疲劳愈深;(2)不同水平的屏面亮度对视疲劳有不同程度的影响。对比度小于7:1时,高亮屏所引起的视疲劳程度比低亮屏的轻;对比度大于7:1时,高亮屏比低亮屏更易引起疲劳。     

计算机显示终端CRT亮度对比度对视觉功能的影响

本实验用作业效绩与眼肌调节时间变化率作指标,研究了计算机终端CRT显示的亮度对比度对视觉功能的影响。结果表明,在屏面背景亮度20cd/m~2左右时,8:1—12:1范围的对比度具有最佳的视觉功能。对比度偏离这个范围时,视觉功能水平随偏离程度而降低。4:1—18:1是CRT亮度对比的宽容度范围。     

DVT背景色的视觉工效比较研究

本研究考察了黑、白两种VDT背景颜色对视觉工效的影响。结果表明,VDT背景颜色列视觉工效有影响,其影响由VDT的字符色和背景色间的颜色对比和背景效应等因素决定。较高的浅白色背景亮度导致视疲劳增加。VDT黑色背景显示的视觉工效优于白色背景。     

不同屏面背景亮度下正确辨认荧光屏(CRT)颜色字符亮度对比度阈的实验研究

本研究的目的是了解屏面背景亮度与正确辩认CRT 红、绿、蓝三种颜色字符所需亮度对比度阈间的变化关系。结果表明:(1)CRT 颜色字符的视觉辩认绩效与屏面背景亮度和字符亮度对比度有关。随背景亮度的提高,正确辩认CRT 红、绿、蓝三种颜色字符的亮度对比度阈均随之下降,且在一定的作业绩效水平上,背景亮度与字符亮度对比度阈间存在“代偿关系”以及“代偿比例转换”的关系;(2)在同等背景亮度下,正确辩认CRT 红、绿、蓝三种颜色字符的亮度对比度阈间存在一定差异,其中,红色字符的亮度对比度阈明显低于蓝色字符。     

不同环境照度下手机屏幕亮度最优参数研究－以三星某手机为例

已有研究表明环境照度、计算机显示器的屏幕亮度和对比度会影响用户的任务操作绩效。本研究采用视觉搜索任务,从行为绩效、主观评价以及眼睛疲劳度指标来考察环境照度、手机屏幕亮度对视觉搜索绩效的影响,并提出在不同的环境照度下手机屏幕亮度的最优值设置参数。结果表明：（1）当手机屏幕亮度保持不变时,不同环境亮度下的搜索绩效差异显著。（2）当环境照度为0lx时,手机屏幕亮度的最优值在11cd/m2左右;环境照度为100lx时,手机屏幕亮度的最优值是68cd/m2左右,环境照度为500lx时,手机屏幕亮度最优值是257cd/m2左右。     

照度和对比度对于视觉显示终端视觉功能的影响

本研究试图通过视觉显示终端的视觉功能研究,了解图象在荧光屏上的亮度对比度、荧光屏照度以及不同光源对于视觉功能的作用。图象在荧光屏上的亮度对比是影响阅读速度的重要因素,同时,荧光屏照度增加时,阅读速度降低。为了提高工作效率,可以提高图象在荧光屏上的亮度对比,也可以降低荧光屏照度。我们似乎可以推荐合适的荧光屏照度为50—200Lux。这时水平工作面照度是70—340Lux。     

照明水平、亮度对比和视标大小对视觉功能的影响

本研究在不同背景照度条件下对不同大小、不同对比度的兰道尔环的辨认进行了实验。主要结果表明:(1)视觉作业水平的提高依赖于视标大小、对比度和背景照度这三个变量及其相互间的关系;在视觉作业水平一定时,视标大小、对比度和背景照度存在着两两对应的代偿关系;(2)以中国人为被试的RCS结果与国外欧美人为被试的CIE推荐的结果基本一致,但前者在低亮度范围内要明显高于后者。     

红光照明条件下VDT不同显示色的视觉效果比较

本研究以VDT上持续进行的视觉作业速度和眼的调节辐合时间作为指标,对红光照明条件下VDT显示的红、黄、绿、蓝、白五种字符色的视觉效果进行了比较.实验中,VDT背景光的主波长为630nm.结果表明,五种字符色在两项指标上均表现出显著差异;绿色显示的视觉效果最好,红色显示的效果最差,黄、白、蓝三色处于中间.     

照度变化对视觉辨认的影响

前 言 近年来,关于工业企业和民用照明视觉功能的探讨逐渐多起来,这方面的研究对于制定照度标准和保护视力有着现实意义。我国过去的研究虽获得不少有益结果,但大多是在一般照明环境中、照度一般在几百勒克斯以下,以阅读视力表作为视觉功能指标。本研究是在比较严格控制的近似等效球照度的实验条件下,在1.7-2160Lux照度范围内,控制观察时间,探讨照度变化对视觉辨认的影响。此外,我们还研究了两种背景(亮和暗)对视觉辨认的影响。     

照明环境与LCD显示界面背景饱和度的交互效应对视觉绩效的影响

摘 要 采用E-prime编排认知实验研究照明环境与TFT-LCD视觉显示终端界面背景饱和度的交互效应对视觉绩效的影响。依据字母视力表设计原理制作认知材料,以认知速度与准确率为视觉绩效评价指标。结果发现,照度与饱和度的交互效应对视觉绩效存在显著影响,色温与饱和度的交互效应仅对准确率存在显著影响,三因素交互作用对准确率存在显著影响。结果表明,不同照度、色温下,通过调节显示终端界面背景饱和度可改善视觉绩效。     

The phantom illumination illusion

A novel brightness illusion in planar patterns is reported. The illusion occurs, for example, when surfaces with a luminance ramp shaded from black to white are positioned on a black homogeneous background, so that each white end of the surfaces faces a single point of the plane of the pattern. The illusion consists of the enhancement of the brightness of the background in a relatively wide area around the white ends of the surfaces. A parametric study was conducted in which participants were asked to rate the difference in brightness between the parts of the background inside and outside a virtual circle formed by disks with different luminance ramps. The results show that mean ratings of brightness depended on the luminance of the background, the luminance range of ramps, and the kind of ramp. Discussion of these results with reference to other brightness illusions (assimilation, neon color spreading, anomalous surfaces, visual phantoms, grating induction, and the glare effect) shows that t hephantom illumination illusion derives from processes producing the perception of ambient illumination.     

Impossible shadows and lightness constancy

The intersection between an illumination and a reflectance edge is characterised by the 'ratio-invariant' property, that is the luminance ratio of the regions under different illumination remains the same. In a CRT experiment, we shaped two areas, one surrounding the other, and simulated an illumination edge dividing them in two frames of illumination. The portion of the illumination edge standing on the surrounding area (labelled contextual background) was the contextual edge, while the portion standing on the enclosed area (labelled mediating background) was the mediating edge. On the mediating background, there were two patches, one per illumination frame. Observers were asked to adjust the luminance of the patch in bright illumination to equate the lightness of the other. We compared conditions in which the luminance ratio at the contextual edge could be (i) equal (possible shadow), or (ii) larger (impossible shadow) than that at the mediating edge. In addition, we manipulated the reflectance of the backgrounds. It could be higher for the contextual than for the mediating background; or, vice versa, lower for the contextual than for the mediating background. Results reveal that lightness constancy significantly increases when: (i) the luminance ratio at the contextual edge is larger than that at the mediating edge creating an impossible shadow, and (ii) the reflectance of the contextual background is lower than that of the mediating one. We interpret our results according to the albedo hypothesis, and suggest that the scission process is facilitated when the luminance ratio at the contextual edge is larger than that at the mediating edge and/or the reflectance of the including area is lower than that of the included one. This occurs even if the ratio-invariant property is violated.     

Lightness constancy: Ratio invariance and luminance profile

The term simultaneous lightness constancy describes the capacity of the visual system to perceive equal reflecting surfaces as having the same lightness despite lying in different illumination fields. In some cases, however, a lightness constancy failure occurs; that is, equal reflecting surfaces appear different in lightness when differently illuminated. An open question is whether the luminance profile of the illumination edges affects simultaneous lightness constancy even when the ratio invariance property of the illumination edges is preserved. To explore this issue, we ran two experiments by using bipartite illumination displays. Both the luminance profile of an illumination edge and the luminance ratio amplitude between the illumination fields were manipulated. Results revealed that the simultaneous lightness constancy increases when the luminance profile of the illumination edge is gradual (rather than sharp) and homogeneous (rather than inhomogeneous), whereas it decreases when the luminance ratio between the illumination fields is enlarged. The results are interpreted according to the layer decomposition schema, stating that the visual system splits the luminance into perceived lightness and apparent illumination components. We suggest that illumination edges having gradual and homogeneous luminance profiles facilitate the luminance decomposition process, whereas wide luminance ratios impede it.     

The influence of depth segmentation on colour constancy

In real scenes, surfaces in different depth planes often differ in the luminance and chromatic content of their illumination. Scene segmentation is therefore an important issue when considering the compensation of illumination changes in our visual perception (lightness and colour constancy). Chromatic adaptation is an important sensory component of colour constancy and has been shown to be linked to the two-dimensional spatial structure of a scene (Werner, 2003 Vision Research 43 1611 - 1623). Here, the question is posed whether this cooperation also extends to the organisation of a scene in depth. The influence of depth on colour constancy was tested by introducing stereo disparity, whereby the test patch and background were perceived in either the same or one of five different depth planes (1.9-57 min of arc). There were no additional cues to depth such as shadows or specular highlights. For consistent illumination changes, colour constancy was reduced when the test patch and background were separated in depth, indicating a reduction of contextual influences. An interaction was found between the influences of stereo depth and spatial frequency on colour constancy. In the case of an inconsistent illumination change, colour constancy was reduced if the test patch and background were in the same depth plane (2-D condition), but not if they were separated in depth (3-D condition). Furthermore, colour constancy was slightly better in the 3-D inconsistent condition than in the 2-D inconsistent condition. It is concluded that depth segmentation supports colour constancy in scenes with inconsistent illumination changes. Processes of depth segmentation are implemented at an early sensory stage of colour constancy, and they define visual regions within which the effects of illuminant changes are discounted for separately. The results support recent models that posit such implementation of scene segmentation in colour constancy.     

Straightness as a cue for luminance edge interpretation

In order to determine the reflectance of a surface, it is necessary to discount luminance changes produced by illumination variation, a process that requires the visual system to respond differently to luminance changes that are due to illumination and reflectance. It is known that various cues can be used in this process. By measuring the strength of lightness illusions, we find evidence that straightness is, used as a cue: When a boundary is straight rather than curved, it has a greater tendency to be discounted, as if it were an illumination edge. The strongest illusions occur when a boundary has high contrast and has multiple X-junctions that preserve a consistent contrast ratio.     

Photometric, geometric, and perceptual factors in illumination-independent lightness constancy

It has been shown that lightness constancy depends on the articulation of the visual field (Agostini & Galmonte, 1999). However, among researchers there is little agreement about the meaning of "articulation." Beyond the terminological heterogeneity, an important issue remains: What factors are relevant for the stability of surface color perception? Using stimuli with two fields of illumination, we explore this issue in three experiments. In Experiment 1, we manipulated the number of luminances, the number of reflectances, and the number of surfaces and their spatial relationships; in Experiment 2, we manipulated the luminance range; finally, in Experiment 3 we varied the number of surfaces crossed by the illumination edge. We found that there are two relevant factors in optimizing lightness constancy: (1) the lowest luminance in shadow and (2) the co-presence of patches of equal reflectance in both fields of illumination. The latter effect is larger if these patches strongly belong to each other. We interpret these findings within the albedo hypothesis.     

When figure-ground segmentation modulates brightness: the case of phantom illumination

In the phantom illumination illusion, luminance ramps ranging from black to white induce a brightness enhancement on an otherwise homogeneous dark background. The strength of the illusion was tested with regard to the extension of the brightness inducing perimeter, surrounding the target area by manipulating the number of inducers (exp. 1) and the size of the inducers (exp. 2). Participants' task was to rate the difference in brightness between the target area and the background. Results show that the illusion occurs only when the target area is not completely segregated from the background by luminance ramps; vice versa, when the target area is delimited by a continuous gradient, it appears darker than the background. These findings suggest a major role of figure-ground organization in the appearance of the illusion. This hypothesis was tested in a rating task experiment with three types of target area shapes circumscribed by four types of edges: luminance contours, illusory contours, no contours, and ambiguous contours. Illusory contours, just as luminance contours, hinder the illusion and produce a darkening of the target area. A control experiment measured the brightness of the previous stimuli without luminance ramps: all configurations resulted in a darkening of the target area. Results from all experiments suggest that figure-ground segmentation plays a major role in the determination of both illumination and lightness in stimuli with luminance gradients.