Street Lighting Glare: A Study using the measurement of light scatter and fMRI

眩光一直被认为是街道照明中的一个问题。路灯和汽车前大灯的眩光会使驾车者和行人感到不适，并降低物体的显眼程度。有一些证据表明，目前的理论可能不能完全解释与眩光来源的大小和颜色有关的视觉表现的变化。从理论上讲，光在眼睛中的散射和像差的影响对视网膜图像质量有很大影响。散射会由于不适、注意力分散和对比度敏感度降低而导致视觉性能损失。在照明设计术语中，这些效果被称为眩光。这个问题通常被细分为不适和失能的眩光。最近，评估眼睛的散布已经成为可能。这项新技术包括使用成像技术直接估计眼睛中的光散射。它不仅快速，而且有望比传统技术更准确。这项技术对于进一步研究残疾眩光至关重要，因为它使研究人员能够收集一组受试者，对于这些受试者，任何给定场景中的面纱亮度都可以精确地计算出来。功能磁共振成像是最近开发的另一种新工具，它可以在眩光研究中发挥作用。自问世以来，功能磁共振成像(FMRI)已经成为绘制人脑神经活动图的常规方法。这一建议的关键是，先前的功能磁共振研究表明，随着刺激亮度对比度的增加，视觉皮质(V1区)内的激活水平增加。区域V1和V2/V3也已被证明对均匀表面的亮度变化作出可靠和强烈的响应。这些大脑皮层区域被认为是代表感知亮度维度的可能候选者。该项目将解决以下几点，以提高我们对眩光相关问题的理解：当眩光存在时，眼睛内的光散射是视觉表现变化的很好的预测指标。这将通过在实验室中评估一些受试者眼睛的光散射特性来进行测试，然后将受试者带到露天测试中心，并向他们提供一系列具有代表性的任务，这些任务代表了行人和司机在不同水平的眩光下在夜间所进行的任务。不适眩光是光源大小的函数。这一点将通过一系列实验室实验来测试，以设定不同光源颜色、大小和几何形状的舒适/不舒适阈值，并通过对室外环境中不同照明方案的主观评估来进行测试。不舒适的眩光会降低视觉表现。有人认为，不适眩光和分心之间存在联系；如果是这样的话，不适眩光可能会扰乱复杂视觉任务的处理。为了测试这一点，我们将在实验室进行一系列实验，受试者必须执行一系列视觉任务，每个任务都相对容易看到，但很难同时完成所有任务。通过使用一系列不同的眩光来源，我们将评估不适眩光的影响。这将通过在帕梅拉实验室进行面部识别任务来检查，仔细设置不同程度的不适眩光，以便提供类似程度的残疾眩光。不适眩光是一种真实现象，可以在大脑中检测到。为了测试这一想法，我们将从我们的受试者队列中选择一组对眩光有不同耐受性的人。我们将研究这组人的大脑活动，同时给他们不同程度的不适眩光所做的各种视觉任务。从fMRI扫描中，我们希望找到与眩光感觉相关的大脑活动的特定模式。

Glare has long been recognised as a problem in street lighting. Glare from street lamps and vehicle headlamps can cause discomfort and a reduction in the conspicuity of objects for both motorists and pedestrians. There is some evidence that the current theory may not explain fully the changes in visual performance that relate to the size and the colour of the glare source. Theoretically the effects of scattering of light and aberrations in the eye have a major impact on retinal image quality. Scattering can cause a loss of visual performance due to discomfort, distraction and reduction in contrast sensitivity. In lighting design terms these effects are known as glare. The problem is usually subdivided into discomfort and disability glare.Recently it has become possible to assess scatter in the eye. The new technique involves direct estimates of light scatter in the eye using imaging techniques. It is both rapid and promises to be significantly more accurate than conventional techniques. This technique is critical to the further investigation of disability glare as it gives the researcher the ability to collect together a group of subjects for whom the veiling luminance in any give scene can be calculated precisely.fMRI is another new tool that has recently been developed to the point where it could be useful in the study of glare. Since its introduction, functional magnetic resonance imaging (fMRI) has become a routine method for mapping neural activity in the human brain. Of key importance to this proposal is that previous fMRI studies have shown an increase in the activation levels within the visual cortex (area V1) with increasing stimulus luminance contrast . Areas V1 and V2/V3 have also been shown to respond reliably and strongly to changes in the luminance of uniform surfaces. These cortical areas are regarded as possible candidates for representing the dimension of perceived brightness.The project will address the following points in order to improve our understanding of the issues associated with glare:Light scatter within the eye is a good predictor of the change in visual performance when glare is present. This will be tested by assessing the light scattering properties of the eyes of a number of subjects in the laboratory and then taking the subjects to the open air test centre and giving them a series of tasks representative of those carried out by pedestrians and drivers at night under different levels of glare.Discomfort glare is a function of source size. This will be tested with a series of laboratory experiments to set the comfort/discomfort threshold for various light source colours, sizes and geometries, and by subjective assessment of different lighting schemes in the outdoor environment.Discomfort glare can reduce visual performance. It has been suggested that there is a relationship between discomfort glare and distraction; if this is the case then discomfort glare may disrupt the processing of complex visual tasks. To test this we will run a series of experiments in the laboratory where the subject has to perform a series of visual tasks that are each relatively easy to see but it is hard to do them all simultaneously. By using a series of different glare sources we will assess the impact of discomfort glare. This will be checked by doing facial recognition tasks in the PAMELA laboratory with different levels of discomfort glare carefully set up so that they provide similar levels of disability glare.Discomfort glare is a real phenomenon and can be detected in the brain. To test this idea we will select from our cohort of subjects a group with differing tolerance to glare. We will study the brain activity the group whilst they are given various visual tasks to do with different levels of discomfort glare. From the fMRI scans we hope to find certain patterns of brain activity that are associated with the sensation of glare.