Smart Lighting and Visual Safety

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Transportation and Future Mobility".

Deadline for manuscript submissions: 29 February 2024 | Viewed by 10861

Special Issue Editors

Department of Illuminating Engineering & Light Sources, School of Information Science and Technology, Fudan University, Shanghai 200438, China
Interests: visual comfort; visual safety; smart lighting; image processing; colour sicence
Dr. Minchen Wei
E-Mail Website
Guest Editor
Department of Building Environment and Energy Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong
Interests: image processing; colour sicence

Special Issue Information

Dear Colleagues,

Smart lighting describes an interdisciplinary field of modern closed-loop luminaires applied for exterior, interior, personal or public lighting and also special cases such as interactive design. Connected research fields started from real mechanical, electronical or optical design, sensing and data collection/evaluation for lamp control strategies until theoretical simulations or modelling with self-learning control algorithms out of the field of machine learning. Strategies from energy saving and light efficiency boosters are included as well. Visual safety describes the potential risk by uncontrolled lamps for people’s habit perceived by our visual- and non-visual system. For reference, the first results can be roughly named physiological or psychological glare, or distractive lighting and projection for modern transportation and mobility.

The goal of this research is to present within this Special Issue knowledge from both fields in theories and applications for humans to improve smart lighting and visual safety, especially in the field of transportation and future mobility, also suitable for other applications involved with the scientific theory of vision and lighting.

Prof. Dr. Yandan Lin
Dr. Minchen Wei
Guest Editors

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Keywords

  • smart lighting
  • visual safety
  • human-centric lighting
  • smart design
  • interactive design
  • light pollution
  • illumination modelling
  • light booster

Published Papers (10 papers)

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Research

15 pages, 4022 KiB  
Article
An Analysis of Visibility Requirements and Reaction Times of Near-Field Projections
Appl. Sci. 2024, 14(2), 872; https://doi.org/10.3390/app14020872 - 19 Jan 2024
Viewed by 419
Abstract
Successful communication between highly automated vehicles and vulnerable road users will be crucial in the future. In addition to the technical requirements of the communication system, the projected content is also essential to ensure successful communication. For this purpose, previous studies have investigated [...] Read more.
Successful communication between highly automated vehicles and vulnerable road users will be crucial in the future. In addition to the technical requirements of the communication system, the projected content is also essential to ensure successful communication. For this purpose, previous studies have investigated the necessary technical requirements for near-field projections. However, the impact of the presentation content, whether symbol- or text-based, on the technological domain, has yet to be investigated. Therefore, a psychophysical subject study investigated the necessary detection probability for symbol- and text-based projection in the near-field of a vehicle. The visibility of symbol- and text-based projections were analyzed by the subject’s detection rate of the tested projection in an ambient lighting scenario of 20 lx at two different distances. Additionally, the corresponding reaction time of the subjects was measured. The results of the subject study showed that, contrarily, an arbitrary increase does not reduce the reaction time and thus saturates at a level of 650 ms before the 90% detection threshold for both projection contents. The observed detection contrast indicates that symbol-based projections need approximately 25% less contrast level than text-based projections to reach a 90% detection rate. Full article
(This article belongs to the Special Issue Smart Lighting and Visual Safety)
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16 pages, 7559 KiB  
Article
Parallax of Head-Up Displays and Visual Safety for Driving
Appl. Sci. 2023, 13(24), 13189; https://doi.org/10.3390/app132413189 - 12 Dec 2023
Viewed by 594
Abstract
Head-up displays (HUDs), a novel form of virtual display, are characterized by their optical structure as a typical binocular virtual display system. This structure exhibits the effect of binocular parallax on visual perception, especially when diverse depth information is displayed on a screen, [...] Read more.
Head-up displays (HUDs), a novel form of virtual display, are characterized by their optical structure as a typical binocular virtual display system. This structure exhibits the effect of binocular parallax on visual perception, especially when diverse depth information is displayed on a screen, which makes the eyes switch between different parallax conditions, and easily affects visual tasks, and induces visual fatigue. Augmented reality HUDs (AR-HUDs) have a wider field of view and are more susceptible to parallax effects. In this study, to determine the acceptable parallax threshold in a two-dimensional virtual display system for HUDs, especially for adjacent positions, and to provide a reference for HUD design, visual comfort and task performance were experimentally evaluated by simulating the overall parallax effect and with step changes on the screen. Specifically, the effects of overall and stepped horizontal and vertical parallaxes on visual fatigue and task performance were evaluated under different conditions. The results showed that the overall horizontal and vertical parallaxes had no significant effect on visual fatigue and task performance. However, stepped horizontal parallax had a significant effect on task performance (p < 0.05), with a parallax value of 3.31 mrad between adjacent positions serving as an acceptable threshold for stepped horizontal parallax as a reference. Significant differences (p < 0.05) in the concentration and fluctuation ratios of the results caused by vertical stepped parallax were found, and an acceptable stepped parallax threshold of 2.24 mrad was obtained. Further, experiments revealed that stepped vertical parallax was more likely to lead to reading misalignments, halos, and distortions. In addition, an exponentially varying relationship between stepped parallax and the error rate of visual performance was observed, and a model was built to predict the degree of influence on visual performance caused by horizontal stepped parallax in virtual displays. This study provides a reference for parallax control between neighboring display icons in AR-HUDs. Full article
(This article belongs to the Special Issue Smart Lighting and Visual Safety)
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14 pages, 762 KiB  
Article
A Novel Way of Optimizing Headlight Distributions Based on Real-Life Traffic and Eye-Tracking Data Part 2: Analysis of Real-World Traffic Environments Data in Germany
Appl. Sci. 2023, 13(17), 9911; https://doi.org/10.3390/app13179911 - 01 Sep 2023
Viewed by 563
Abstract
In order to find optimized headlight distributions based on real traffic data, a three-step approach has been chosen. Since the complete investigations are too extensive to fit into one single publication, this paper is the second of three papers. Over the course of [...] Read more.
In order to find optimized headlight distributions based on real traffic data, a three-step approach has been chosen. Since the complete investigations are too extensive to fit into one single publication, this paper is the second of three papers. Over the course of these papers, a novel way to optimize automotive light distributions based on real-life traffic and eye-tracking data is presented. Over all three papers, 119 test subjects participated in the studies, with over 15,000 km of driving, including recordings of gaze behavior, light data, detection distances and other objects in traffic. In the first paper, an ideal headlight distribution for straight roads with no other road users was identified. The second paper aims to collect the data required to modify this idealized headlight distribution for use on real roads. The first step is to find the extent to which real roads differ from an ideal, straight road. To do this, the German traffic space was analyzed. A new test vehicle recorded video and GPS data over a selected route. The video data were then evaluated by a machine learning algorithm. Object recognition software was used to find different traffic participants and road signs. Camera calibrations were used to find the exact angles of these objects. Using publicly available road data combined with the recorded GPS data, the video data were split into different road categories, and traffic object distributions were calculated for urban roads, country roads and motorways. The resulting analyses provided representative distributions of vehicles and highway signs along different types of roadways and roadway geometries. The GPS data were also used to find the curvature distributions along the selected route. These data were then used to optimize segment sizes for an adaptive driving beam. Overall, increasing the number of segments above 100 did not have appreciable benefits. These data will also be used in the third paper, where along the same route, the gaze distribution of drivers was recorded and analyzed. Full article
(This article belongs to the Special Issue Smart Lighting and Visual Safety)
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12 pages, 562 KiB  
Article
A Novel Way of Optimizing Headlight Distributions Based on Real Life Traffic and Eye Tracking Data Part 1: Idealized Baseline Distribution
Appl. Sci. 2023, 13(17), 9908; https://doi.org/10.3390/app13179908 - 01 Sep 2023
Viewed by 573
Abstract
In order to find optimized headlight distributions based on real traffic data, a three-step approach is chosen. Since the complete investigations are too extensive to fit into a single publication, this paper is the first in a series of three publications. Over three [...] Read more.
In order to find optimized headlight distributions based on real traffic data, a three-step approach is chosen. Since the complete investigations are too extensive to fit into a single publication, this paper is the first in a series of three publications. Over three papers, a novel way to optimize automotive headlight distributions based on real-life traffic and eye-tracking data is presented, based on 119 test subjects who participated in over 15,000 km of driving, including recordings of gaze behavior, light data, detection distances, and other objects in traffic. In the present paper, a baseline headlight distribution is derived from a series of detection tests conducted under ideal conditions, with a total of three tests, each with 19–30 subjects, conducted within the same test environment. In the first test, the influence of low beam intensity on the detection of pedestrians on the sidewalk (5.0 m from the center of the driving lane) is investigated. In the second test, the influence of different high beam intensities was investigated for the same detection task. In the third test, the headlight distribution and intensity are kept constant at a representative high beam level, but the detection task is changed. In this test, the pedestrian detection target is placed along different detection angles, ranging from immediately adjacent to the road (2.5°) to 15.5 m away from the center of the driving lane (8.0°). As mentioned, all of these tests were conducted under ideal conditions, with the studies taking place on an airfield with a 1.2 km long straight road and normal road markings, but without oncoming traffic, tasks other than keeping the vehicle with cruise control within its lane, or other distracting objects present. The tests yielded two sets of data; the first is the intensity, based on the first two studies, needed to ensure sufficient intensity to detect objects under ideal conditions at distances needed for different driving speeds. The last test then uses these intensities and necessary variations in the required intensity to create an idealized, symmetric headlight distribution as a baseline for subsequent publications. Although the distribution applies only to passenger vehicles like the one used in the test, the same approach could be applied to other vehicle types. The second paper of this series will focus on real traffic objects and their distributions within the traffic space in order to identify relevant areas in headlight distribution when driving under real traffic conditions. The third paper of this series will analyze driver gaze distributions during real driving scenarios. The data from all three papers are used to create optimized headlight distributions, thereby showing how such an optimized distribution relates to current headlight distributions in terms of luminous flux, intensity, and overall distribution. Full article
(This article belongs to the Special Issue Smart Lighting and Visual Safety)
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11 pages, 1561 KiB  
Article
A Novel Way of Optimizing Headlight Distributions Based on Real-Life Traffic and Eye Tracking Data Part 3: Driver Gaze Behaviour on Real Roads and Optimized Light Distribution
Appl. Sci. 2023, 13(17), 9898; https://doi.org/10.3390/app13179898 - 01 Sep 2023
Viewed by 630
Abstract
In order to find optimized headlight distributions based on real traffic data, a three-step approach has been chosen. The complete investigations are too extensive to fit into a single paper; this paper is the last of a three part series. Over the three [...] Read more.
In order to find optimized headlight distributions based on real traffic data, a three-step approach has been chosen. The complete investigations are too extensive to fit into a single paper; this paper is the last of a three part series. Over the three papers, a novel way to optimize automotive headlight distributions based on real-life traffic and eye tracking data is presented. Across all three papers, a total of 119 test subjects participated in the studies with over 15,000 km of driving, including recordings of gaze behaviour, light data, detection distances, and other objects in traffic. In this third paper, driver gaze behaviour is recorded while driving a 128 km round course, covering urban roads, country roads, and motorways. This gaze behaviour is then analysed and compared to prior work covering driver gaze behaviour. Comparing the gaze distributions with roadway object distributions from part two of this series, Analysis of Real-World Traffic Data in Germany and combining them with the idealized baseline headlight distribution from part one, different optimized headlight distributions can be generated. These headlight distributions can be optimized for different driving requirements based on the data that is used and weighting the different road types differently. The resulting headlight distribution is then compared to a standard light distribution in terms of the required luminous flux, angular distribution, and overall shape. Nonetheless, it is the overall approach that has been taken that we see as the primary novel outcome of this investigation, even more than the actual distribution resulting from this effort. Full article
(This article belongs to the Special Issue Smart Lighting and Visual Safety)
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14 pages, 3420 KiB  
Article
Investigation of Text-Background Lightness Combination on Visual Clarity Using a Head-Up Display under Various Surround Conditions and Different Age Groups
Appl. Sci. 2023, 13(10), 6037; https://doi.org/10.3390/app13106037 - 14 May 2023
Viewed by 985
Abstract
Up until now, head-up displays (HUDs) have been installed in front of the driver’s seat to provide drivers with auxiliary information. It may be used in various surroundings, ranging from very dark to very bright environments, such as daylight. A suitable text-background lightness [...] Read more.
Up until now, head-up displays (HUDs) have been installed in front of the driver’s seat to provide drivers with auxiliary information. It may be used in various surroundings, ranging from very dark to very bright environments, such as daylight. A suitable text-background lightness combination can improve the driver’s visual clarity and efficiency when identifying displayed information to raise driving safety. Although many kinds of HUDs are designed to improve visual clarity by adjusting brightness, few studies have investigated the influence of the text-background lightness combination of a HUD on visibility, especially as the lighting level of the driving condition changes dramatically. In the study, 60 observers, comprising 20 young, 20 middle-aged, and 20 older participants, evaluated the visual clarity of 20 text-background lightness combinations on a HUD using paired comparison methods under dark and daylight surroundings (i.e., 300, 1500, and 9000 lx conditions). As a result, the combination of white text on a black background and black text on a white background presented the most significant preference and the best visual clarity under dark and daylight surroundings, respectively, improving visual safety when driving. Full article
(This article belongs to the Special Issue Smart Lighting and Visual Safety)
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17 pages, 3818 KiB  
Article
Required Visibility Level for Reliable Object Detection during Nighttime Road Traffic in Non-Urban Areas
Appl. Sci. 2023, 13(5), 2964; https://doi.org/10.3390/app13052964 - 25 Feb 2023
Cited by 3 | Viewed by 1090
Abstract
Motor vehicle headlamps are the only light sources that create visibility conditions for the driver in nighttime non-urban traffic. Therefore, a suitable design of these lighting systems is of the highest relevance to allow the driver an early detection of obstacles so that [...] Read more.
Motor vehicle headlamps are the only light sources that create visibility conditions for the driver in nighttime non-urban traffic. Therefore, a suitable design of these lighting systems is of the highest relevance to allow the driver an early detection of obstacles so that an appropriate reaction is possible. In order to provide a design basis for the headlamps, this article deals with the determination of the minimum required lighting conditions for reliable object detection. For this purpose, studies with drivers were conducted in a light tunnel on a closed test site, and the Visibility Level (VL) required for reliable object detection was considered. Gray cards with a reflectance of 4% were positioned on different positions of measurement grids, and the intensity of the low beam and high beam of a test vehicle was increased step by step until the drivers had detected the gray card. The results demonstrate that a Visibility Level of at least 13.35 is required in non-urban areas in order to reliably detect objects. In addition, the required Visibility Level depends on the eccentricity angle. Thus, the required Visibility Level reaches its maximum value in the foveal area of the field of view and decreases in a Gaussian shape in the periphery. Full article
(This article belongs to the Special Issue Smart Lighting and Visual Safety)
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21 pages, 16803 KiB  
Article
Influence of Headlight Level on Object Detection in Urban Traffic at Night
Appl. Sci. 2023, 13(4), 2668; https://doi.org/10.3390/app13042668 - 19 Feb 2023
Cited by 1 | Viewed by 2220
Abstract
The purpose of this work is to determine the influence of the low beam intensity of motor vehicle headlights on detection conditions in urban traffic. For this purpose, studies with fourteen subjects are conducted on three differently illuminated test roads, in which the [...] Read more.
The purpose of this work is to determine the influence of the low beam intensity of motor vehicle headlights on detection conditions in urban traffic. For this purpose, studies with fourteen subjects are conducted on three differently illuminated test roads, in which the low beam intensity is dimmed from off to fully on. At each dimming level, the subjects indicate whether or not they have detected the object, which is realized by a flat target and occurs at sixteen different positions in front of the vehicle. In addition, considerations of the contrast curve and the visibility level are made in order to determine the influence of switched off and fully switched on headlights. The results show that the negative contrast created by the existing street lighting creates detection conditions at least as good as full low beam intensity in almost all cases. The results further indicate that the influence of the low beam intensity increases with decreasing distance to the object and decreasing illumination levels. The results of this work show that an increase in low beam intensity initially leads to poorer detection conditions; thus, the option of reducing low beam intensity should be considered in urban traffic space. Full article
(This article belongs to the Special Issue Smart Lighting and Visual Safety)
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13 pages, 4085 KiB  
Article
Lawn Lamp Design Based on Fuzzy Control and Secondary Optical Optimization
Appl. Sci. 2023, 13(3), 1631; https://doi.org/10.3390/app13031631 - 27 Jan 2023
Viewed by 1292
Abstract
With the emergence of new technologies, the design of urban infrastructure is constantly being innovated, and the lawn lamp as urban lighting infrastructure is an important part of urban infrastructure. For the current lawn lamp function, there are single, large power consumption, low [...] Read more.
With the emergence of new technologies, the design of urban infrastructure is constantly being innovated, and the lawn lamp as urban lighting infrastructure is an important part of urban infrastructure. For the current lawn lamp function, there are single, large power consumption, low light energy utilization and other shortcomings. Combined with deep learning and optical design, this paper constructs an adaptive lighting control system based on the technology of the Internet. Considering the nonlinear and time-varying characteristics of external factors, a fuzzy control model with ambient light level and pedestrian flow as input and dimming coefficient K (0 < K < 1) as output is proposed to adjust the brightness of the light source and achieve energy savings. In order to improve the light energy utilization of the luminaire and reduce the glare index of the luminaire, a free-form total internal reflection (TIR) lens was designed by finding the optimal curvature of the lens through the polycurved edge light principle. The light source of the lawn lamp was simulated by TracePro, and the results showed that the light energy utilization reached 90%. Finally, the ambient illumination and pedestrian flow data of Dalian ZT Park were measured for different time periods at the site, and the data were normalized using the min-max normalization algorithm. The adaptive dimming capability of the system was verified through simulation tests and field tests, and the results showed that the lighting energy efficiency under the control system was 38%. Full article
(This article belongs to the Special Issue Smart Lighting and Visual Safety)
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14 pages, 2319 KiB  
Article
Resolution Aspects for Near-Field Projections
Appl. Sci. 2023, 13(2), 1039; https://doi.org/10.3390/app13021039 - 12 Jan 2023
Cited by 1 | Viewed by 1351
Abstract
This work intends to define the resolution requirements for near-field projections in a psycho-physical study design to evaluate the participants’ perception under the influence of different ambient lighting levels and various viewing distances. The variation in ambient lighting and viewing distances relates to [...] Read more.
This work intends to define the resolution requirements for near-field projections in a psycho-physical study design to evaluate the participants’ perception under the influence of different ambient lighting levels and various viewing distances. The variation in ambient lighting and viewing distances relates to various daytime and critical distances in urban environments. The application of near-field projections increases the popularity of communication- or safety-relevant projections, such as for automated vehicles. However, previous studies in the filming industry have shown that the resolution requirements differ depending on the application. In this work, a field study design presents an experimental approach to define a perceived resolution on the street surface in the near field around the vehicle. Furthermore, the study evaluates the influence of viewing distance, ambient lighting and projection content on the perceived resolution in detail. The results reveal a significant dependency on ambient lighting (p < 0.05). Furthermore, this work states that the symbol-based projection has lower resolution requirements, e.g., a viewing distance of 1 m and 3 m results in a 2 pixels per degree resolution compared to the text-based projection in the parking garage scenario. Nevertheless, in the dusk/dawn scenario, the perceived resolution can be grouped for viewing distances above 1 m for content-independent projections. Full article
(This article belongs to the Special Issue Smart Lighting and Visual Safety)
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