The Effect Of Display Brightness On Visual Function For Young And Old Drivers

Nowadays outdoor advertising displays have become popular. Bright displays near the roads could cause drivers to experience disability or discomfort glare, especially at night. Disability glare increases with age, but discomfort glare thresholds are independent of age. The aim of the study was to assess a luminance level of displays, which causes glare for younger and older subjects. 24 young subjects age of 20 to 24 years and 13 older subjects age of 55 to 69 years participated in the study. The task was by using the method of adjustment to find out the acceptable level of display brightness when the recognition of high (>90%) contrast objects was comfortable. Measurements were done in a photopic and mesopic lighting conditions. Results showed that discomfort glare were larger in mesopic than in photopic lighting conditions (p < 0.001) for both age groups. Preferred display brightness in both lighting conditions did not significantly differ between age groups (p > 0.05). We can conclude that discomfort glare thresholds for displays with textual elements are independent of age.

Luminosity thresholds of colored surfaces are determined by their heuristic upper-limit luminances in the visual system

Some objects in the real world themselves emit a light, and we typically have a fairly good idea as to whether a given object is self-luminous or illuminated by a light source. However, it is not well understood how our visual system makes this judgement. This study aimed to identify determinants of luminosity threshold, a luminance level at which the surface begins to appear self-luminous. We specifically tested a hypothesis that our visual system knows a maximum luminance level that a surface can reach under the physical constraint that surface cannot reflect more lights that incident lights and apply this prior to determine the luminosity thresholds. Observers were presented a 2-degree circular test field surrounded by numerous overlapping color circles, and luminosity thresholds were measured as a function of (i) the chromaticity of the test field, (ii) the shape of surrounding color distribution and (iii) the color of illuminant lighting surrounding colors. We found that the luminosity thresholds strongly depended on test chromaticity and peaked around the chromaticity of test illuminants and decreased as the purity of the test chromaticity increased. However, the locus of luminosity thresholds over chromaticities were nearly invariant regardless of the shape of surrounding color distribution and generally well resembled the locus drawn from theoretical upper-limit luminance but also the locus drawn from the upper boundary of real objects. These trends were particularly evident for test illuminants on blue-yellow axis and curiously did not hold under atypical illuminants such as magenta or green. Based on these results, we propose a theory that our visual system empirically internalizes the gamut of surface colors under illuminants typically found in natural environments and a given surface appears self-luminous when its luminance exceeds this heuristic upper-limit luminance.

Use of Pupil Area and Fixation Maps to Evaluate Visual Behavior of Drivers inside Tunnels at Different Luminance Levels—A Pilot Study

This study reports the results of a pilot study on spatiotemporal characteristics of drivers’ visual behavior while driving in three different luminance levels in a tunnel. The study was carried out in a relatively long tunnel during the daytime. Six experienced drivers were recruited to participate in the driving experiment. Experimental data of pupil area and fixation point position (at the tunnel’s interior zone: 1566 m long) were collected by non-intrusive eye-tracking equipment at three luminance levels (2 cd/m2, 2.5 cd/m2, and 3 cd/m2). Fixation maps (color-coded maps presenting distributed data) were created based on fixation point position data to quantify changes in visual behavior. The results demonstrated that luminance levels had a significant effect on pupil areas and fixation zones. Fixation area and average pupil area had a significant negative correlation with luminance levels during the daytime. In addition, drivers concentrated more on the front road pavement, the top wall surface, and the cars’ control wheels. The results revealed that the pupil area had a linear relationship with the luminance level. The limitations of this research are pointed out and the future research directions are also prospected.

Investigating Arousal, Saccade Preparation, and Global Luminance Effects on Microsaccade Behavior

Microsaccades, small saccadic eye movements occurring during fixation, have been suggested to be modulated by various sensory, cognitive, and affective processes relating to arousal. Although the modulation of fatigue-related arousal on microsaccade behavior has previously been characterized, the influence of other aspects of arousal, such as emotional arousal, is less understood. Moreover, microsaccades are modulated by cognitive processes (e.g., voluntary saccade preparation) that could also be linked to arousal. To investigate the influence of emotional arousal, saccade preparation, and global luminance levels on microsaccade behavior, emotional auditory stimuli were presented prior to the onset of a fixation cue whose color indicated to look either at the peripheral stimulus (pro-saccade) or in the opposite direction of the stimulus (anti-saccade). Microsaccade behavior was found to be significantly modulated by saccade preparation and global luminance level, but not emotional arousal. In the pro- and anti-saccade task, microsaccade rate was lower during anti-saccade preparation as compared to pro-saccade preparation, though microsaccade dynamics were comparable during both trial types. Our results reveal a differential role of arousal linked to emotion, fatigue, saccade preparation, and global luminance level on microsaccade behavior.

The Drive towards Optimization of Road Lighting Energy Consumption Based on Mesopic Vision—A Suburban Street Case Study

This paper presents the research of optimization of road lighting energy consumption by utilizing the fact of human twilight and night vision (mesopic vision) dependency on luminance level and lamp’s light spectral composition. The research was conducted for a suburban street illuminated by smart LED road luminaires with a luminous flux control system with which different luminance levels can be achieved on the road. This road is an access road leading to a town located on the outskirts of Warsaw which is the capital of Poland and a large metropolitan area. Therefore, the traffic here is quite heavy on this road in the morning and in the evening and it is very light at other times of the day. In accordance with EN 13201 standard, lighting control can be applied to illuminate this road. This paper compares energy consumption for different lighting scenarios of the road in question. In the first scenario, the road luminance is compliant with M4, M5, and M6 lighting class requirements depending on the time of the day. In the second scenario, for each M lighting class, the values of luminance levels provided by EN 13201 standard have been reduced to the values resulting from their conversion to the corresponding mesopic luminance values. The conducted research has shown that a 15% saving per year in electricity consumption on the road is possible with such a conversion. Therefore, energy efficiency of a lighting installation can be improved by matching the lighting levels provided by the standard to the mesopic vision.

Simulation and Analysis of Floodlighting Based on 3D Computer Graphics

The paper presents the opportunities to apply computer graphics in an object floodlighting design process and in an analysis of object illumination. The course of object floodlighting design has been defined based on a virtual three-dimensional geometric model. The problems related to carrying out the analysis of lighting, calculating the average illuminance, luminance levels and determining the illuminated object surface area are also described. These parameters are directly tied with the calculations of the Floodlighting Utilisation Factor, and therefore, with the energy efficiency of the design as well as the aspects of light pollution of the natural environment. The paper shows how high an impact of the geometric model of the object has on the accuracy of photometric calculations. Very often the model contains the components that should not be taken into account in the photometric calculations. The research on what influence the purity of the geometric mesh of the illuminated object has on the obtained results is presented. It shows that the errors can be significant, but it is possible to optimise the 3D object model appropriately in order to receive the precise results. For the example object presented in this paper, removing the planes that do not constitute its external surface has caused a two-fold increase in the average illuminance and average luminance. This is dangerous because a designer who wants to achieve a specific average luminance level in their design without optimizing the model will obtain the luminance values that will actually be much higher.

Preliminary Result on the Direct Assessment of Perceptible Simultaneous Luminance Dynamic Range

The human visual system is capable of adapting across a very wide dynamic range of luminance levels; values up to 14 log units have been reported. However, when the bright and dark areas of a scene are presented simultaneously to an observer, the bright stimulus produces significant glare in the visual system and prevents full adaptation to the dark areas, impairing the visual capability to discriminate details in the dark areas and limiting simultaneous dynamic range. Therefore, this simultaneous dynamic range will be much smaller, due to such impairment, than the successive dynamic range measurement across various levels of steady-state adaptation. Previous indirect derivations of simultaneous dynamic range have suggested between 2 and 3.5 log units. Most recently, Kunkel and Reinhard reported a value of 3.7 log units as an estimation of simultaneous dynamic range, but it was not measured directly. In this study, simultaneous dynamic range was measured directly through a psychophysical experiment. It was found that the simultaneous dynamic range is a bright-stimulus-luminance dependent value. A maximum simultaneous dynamic range was found to be approximately 3.3 log units. Based on the experimental data, a descriptive log-linear model and a nonlinear model were proposed to predict the simultaneous dynamic range as a function of stimulus size with bright-stimulus luminance-level dependent parameters. Furthermore, the effect of spatial frequency in the adapting pattern on the simultaneous dynamic range was explored. A log parabola function, representing a traditional Contrast Sensitivity Function (CSF), fitted the simultaneous dynamic range data well.

Luxotonic signals in human prefrontal cortex: A possible substrate for effects of light on mood and cognition

Light impacts mood and cognition of humans and other animals in ways we are only beginning to recognize. These effects are thought to depend upon a specialized retinal output signal arising from intrinsically photosensitive retinal ganglion cells (ipRGCs) that is being dedicated to a stable representation of the intensity of environmental light. Insights from animal studies now implicate a previously unknown pathway in the effects of environmental light on mood. A subset of ipRGCs transmits light-intensity information to the dorsothalamic perihabenular nucleus, which in turn, innervates the medial prefrontal cortex that plays a key role in mood regulation. While the prefrontal cortex has been implicated in depression and other mood disorders, its ability to encode the level of environmental light (luminance) has never been reported. Here, as a first step to probing for a similar retino-thalamo-frontocortical circuit in humans, we used functional magnetic resonance imaging (fMRI) to identify brain regions in which activity depended on luminance level where activity was modulated either transiently or persistently by light. Twelve brain regions altered their steady-state activity according to luminance level. Most were in the prefrontal cortex or in the classic thalamocortical visual pathway; others were found in the cerebellum, caudate, and pineal. Prefrontal cortex and pineal exhibited reduced BOLD signal in bright light, while the other centers exhibited increased BOLD signals. The light-evoked prefrontal response was affected by light history and closely resembled those of ipRGCs. Although we did not find clear correspondence between the luxotonic regions in humans and those in mice, the persistence and luxotonic nature of light-evoked responses in the human prefrontal cortex may suggest that it receives input from ipRGCs, just like in the mouse. We also found seventeen regions in which activity varied only transiently with luminance level. These regions, which are involved in visual processing, motor control, and cognition, were in the cerebral cortex, diverse subcortical structures, and cerebellum. Therefore, our results demonstrate the effects of light on diverse brain centers that contribute to motor control, cognition, emotion, and reward processing.