Vehicle Headlights Research Articles

Using Self-Aligned Si Barrier to Enhance the Contrast Ratio and Performance of Pixelated Light Emitting Diode for Vehicle Headlamp

We investigate the effects of pixel distance and light emitting diode (LED) thickness on the luminance distribution and contrast ratio of a 16 × 16 blue and white LED array for vehicle headlamp application. With increasing pixel distance from 10 to 20 μm, the contrast ratio increased from 33:1 to 51:1 for white LEDs and from 37:1 to 48:1 for blue LEDs. As the LED thickness decreased from 4.5 to 2.0 μm, the contrast ratio increased from 37:1 to 62:1 for blue LEDs and from 33:1 to 97:1 for white LEDs. The blue LEDs fabricated with ultrathin-GaN and self-aligned Si barrier showed the contrast ratio of 48:1 and 39:1, respectively, while the white LEDs with ultrathin-GaN and self-aligned Si barrier yielded the contrast ratio of and 89:1 and 99:1. Further, LEDs with the self-aligned Si barrier had better luminance uniformity than those with the ultrathin-GaN. LED array with the self-aligned Si barrier exhibited narrower dark space than that with the ultrathin-GaN. At 60 mA, the LED with the self-aligned Si barrier gave 6% higher light output than that with the ultrathin-GaN. A headlamp unit using 16 × 16 LED array was demonstrated with the Si self-aligned barrier.

Forensic comparison analysis of plastic vehicle headlamp lens by gel permeation chromatography and statistical methods.

Comparison analysis of vehicle headlamp lens fragments can help establish links between the relevant vehicle with crime scenes or provide useful information to search the related vehicles. Headlamp lenses are mainly made of polycarbonate with very few signature additives, which makes them difficult to be discriminated by commonplace examination methods of infrared spectroscopy and scanning electron microscope coupled with energy dispersive X-ray spectroscopy. In this study, molecular weights (Mw) and the polydispersity index (PDI) value of 50 vehicle headlamp lens fragments from different vehicles were measured by gel permeation chromatography, and Hotelling's T2 statistical method was applied to facilitate interpretation of the data. Among the total pairs of comparisons between 50 samples, 62 pairs cannot be distinguished, resulting in a discrimination rate of 94.94%. It suggested that the method of gel permeation chromatography and Hotelling's T2 statistical analysis were powerful to make further discrimination between plastic vehicle headlamp lens fragments.

Impact of Vehicle Headlights Radiation Pattern on Dynamic Vehicular VLC Channel

This article develops a statistical large-scale fading (path loss) model of a dynamic vehicular visible light communication (VVLC) system. The proposed model combines the impact of inter-vehicle spacing and the radiation intensity distribution as a function of the irradiance angle which changes with the traffic conditions. Three models (Lambertian, Gaussian, and empirical) are utilized to examine the impact of vehicles headlights radiation pattern on the statistical path loss of VVLC system. The analytical model of channel path loss is validated by Monte Carlo simulation with the headlight model simulated with a raytracing software. The path loss values of the Gaussian model differ by 2 dB compared to the Lambertian model, irrespective of the traffic conditions while it differs by 24.6 dB during late night and 8.15 dB during rush hours compared to the empirical model of a Toyota Altis headlight. This variation shows that the radiation intensity distribution should be modelled for each vehicle's headlights from each manufacturer to ensure accurate VVLC channel model. The proposed Gaussian model provides a close approximation to describe such radiation pattern and can easily be adapted to model for different manufacturers' headlights.

Solution for a two-year renewal cycle of structured road markings

Road markings are a necessary safety feature that guides drivers. For visibility in darkness, when accident risk and severity are the highest, road markings must be reflectorised with glass beads to be visible when vehicle headlights shine on them. Renewal of thick-layer structured road markings that have lost retroreflectivity but have retained the structure mostly intact is performed through application of thin-layer paint coatings. Based on a field experiment, it was demonstrated that selection of premium glass beads profoundly extends the durability of the renewed markings, which could be further enhanced through the use of high-performance waterborne paint. Whereas the standard system based on solventborne paint and typically used glass beads failed after a single winter, the use of premium road marking system at least doubled the service life. The extended road marking service life translates to 50% savings in material consumption, 50-97% lower emissions of volatile organic compounds, and a decrease in long-term financial expense by 5-26%.

A Image Enhancement Method For Night-Way Images

Image processing has a wide range of applications especially in our daily lives. Image processing is not common in sensitive industrial applications. Because of these applications, very high percentage of success is requested. Also these applications work in real-time. However, it can be widely used in many daily routines (driving, entrance to the workplace/ exit, control of multimedia devices, security applications, identification applications, etc.). Especially Advanced Driver Assistance Systems (ADAS) is a popular working area for image processing. Strip tracking systems, pedestrian detection systems, reading of traffic signs and signals are based on image processing. In this study, a new method has been developed to increase the visibility levels of road images at night driving. In these images, the brightness level is low because of insufficient of light sources (headlights and road lighting) which are often used to increase the driver's view. On the other hand, adversely affects the view of driver which the headlight of coming vehicles from opposite directions, poorly structured road lighting and etc. Especially the vehicle headlights coming from the opposite direction take the eye of the drivers and cause the level of view to decrease. Intense dark areas and light sources are in the image together. By so, special to these images requires the use of an adaptive improvement method. This is because, when classical image enhancement methods are used, the visibility levels of the dark areas are increased, and the shining regions are more likely to shine and the visibility level decreases in these regions. The developed method aims at enhancement these images that drivers be exposed to. For this purpose, the light sources in the image and the magnitudes of these light sources, the distance of the pixels to be calculated from the light sources, the value of the pixel itself and the neighboring pixels are used as separate parameters. Images are enhancement with the equations developed using these parameters. When the output images obtained with the use of the developed equations and the obtained Structural Similarity İndex Maps (SSIM) are examined, it is seen that the developed method gives good results.

Adaptive driving beam system with MEMS optical scanner for reconfigurable vehicle headlight

An adaptive driving beam (ADB) for vehicle headlights has been developed using a microelectromechanical systems optical scanner. A piezoelectric scanner is constructed using thin-film lead-zirconate-titanate oxide (PbZrTiO3, PZT) on a bonded silicon-on-insulator (SOI) wafer, respectively, processed by ion-milling and deep reactive ion etching. The PZT layer is laminated in metal films on the SOI layer to form a piezoelectric unimorph actuator, which are then arranged as a pair of twisting suspensions to drive the scanner at resonance. The same piezoelectric actuators are also arranged into another form of meandering suspensions to generate a large deflection angle. By the combination of these two mechanisms, two-dimensional optical scanner is constructed in a single chip. The scanner is used to draw a Lissajous pattern of a blue laser light on a phosphor material to create a structured light source that is projected forward for illumination. The lighting patterns and positions are electronically controlled and reconfigured depending upon the location of leading/oncoming vehicles, pedestrians, road signs, and the cruising speed of the vehicle. The paper discusses on the design of the piezoelectrically driven optical scanner along with the optomechanical performances. We also report on the road-test result of the developed on-vehicle ADB module.

A novel method for vehicle headlights detection using salient region segmentation and PHOG feature

In this paper, we explore an issue that is to detect vehicle headlights from the nighttime traffic surveillance images with highly reflections. In the night, reflections on the road (water) surface, vehicles bodies, or some reflective objects (such as lane markings, traffic signs) will interfere the headlight detection seriously. Although the existing methods have achieved good results, however, most of them failed to detect the headlight when headlights are far from camera. In order to solve the issue, we propose a novel method for vehicle headlights detection. The proposed method makes full use of the brightness and gradient information of the headlights in the night. First, we propose an effective region-of-interest (ROI) segmentation method which is based on multi-scale local saliency detection. The method pre-serve faint or small-sized objects and retain the original shape of the object to the greatest extent. Then, we compute the pyramid histogram of oriented gradients (PHOG) features, which are used to train support vector machine (SVM) classifier. Finally, the extracted bright blocks are classified according to the pre-trained SVM classifier. Experimental results and quantitative evaluations in different scenes demonstrate that our proposed method can achieve a better result compared with previous methods.

Evaluation of disability glare caused by headlights of most common vehicles in Iran

Background and Objectives: Road traffic accident is one of the leading causes of death in some countries such as Iran. Disability glare due to headlights of vehicles can increase the risk of crashes and make dangerous conditions. This study aimed to investigate the level of glare induced by the headlights of most common vehicles in Iran. Materials and Methods: This cross-sectional study was conducted in a suburban road of Ilam province in 2019. The disability glare resulted from the headlights of Pride Saba GTX, Pride 131SL, Samand Soren, Peugeot 405, Megan, and Peugeot Pars was measured at the distances of 10–100 m away from the headlights. The Threshold Elevation index under the high-beam and low-beam conditions (headlight's operation modes) was obtained for the background luminance condition including 1 and 50 cd/m2 for the age groups of 20, 35, 70, and 83 years old. Results: When the background luminance was 1 cd/m2, the mean glare level caused by the high-beam mode of illumination exceeded the recommended disability glare thresholds of all age groups. When the background luminance was 50 cd/m2, at certain longitudinal distances, glare level exceeded the disability glare thresholds of the elderly drivers (aged 70 and 83 years). At the background luminance of 1 cd/m2, low-beam mode of illumination caused disability glare at certain distances but not in general. At the background luminance of 50 cd/m2, low-beam mode of illumination did not cause disability glare at any distance. Conclusion: The results showed the mutual effect of luminance and the angle of line of sight with respect to glare source on the emergence of disability glare. The age also exhibited a significant association with the disability glare, as the highest glare levels were obtained for older drivers.

Vision-based On-Road Nighttime Vehicle Detection and Tracking Using Taillight and Headlight Features

An important and challenging aspect of developing an intelligent transportation system is the identification of nighttime vehicles. Most accidents occur at night owing to the absence of night lighting conditions. Vehicle detection has become a vital subject for research to ensure safety and avoid accidents. New vision-based on-road nighttime vehicle detection and tracking system are suggested in this survey paper using taillight and headlight features. Using computer vision and some image processing techniques, the proposed system can identify vehicles based on taillight and headlight features. For vehicle tracking, a centroid tracking algorithm has been used. Euclidean Distance method has been used for measuring the distances between two neighboring objects and tracks the nearest neighbor. In the proposed system two flexible fixed Region of Interest (ROI) have been used, one is the Headlight ROI, and another is the Taillight ROI that could adapt to different resolutions of the images and videos. The achievement of this research work is that the proposed two ROIs can work simultaneously in a frame to identify oncoming and preceding vehicles at night. The segmentation techniques and double thresholding method have been used to extract the red and white components from the scene to identify the vehicle headlights and taillights. To evaluate the capability of the proposed process, two types of datasets have been used. Experimental findings indicate that the performance of the proposed technique is reliable and effective in distinct nighttime environments for detection and tracking of vehicles. The proposed method has been able to detect and track double lights as well as single light such as motorcycle light and achieved average accuracy and average processing time of vehicle detection about 97.22% and 0.01 s per frame respectively.

Development of thermal insulation sandwich panels containing end-of-life vehicle (ELV) headlamp and seat waste

Recycling automotive waste has increasingly become an alternative solution towards producing sustainable materials given the rising issue of raw material shortages and waste management challenges at global level. The improper end-of-life vehicle (ELV) waste management poses detrimental impacts on the environment. This paper proposes a novel method to develop thermal insulation sandwich panels using ELV waste, motivated by the critical needs of creating high-performance thermal insulation for buildings. Six sandwich panels (P1-P6) of different weight and ratio of shredded ELV particles were manufactured. The sandwich panels structure was made of three layers: a core, and a glass face sheet bonded to each side. The core structure composed of Polycarbonate (PC) from headlamp lenses and polyurethane (PU) from seat, bonded using resin casting approach. Thermal conductivity of the samples was measured using guarded hot-plate apparatus. Results corroborated that thermal conductivity of ELV-based sandwich panels reduced remarkably compared to panel without ELVs, recorded at 15.51% reduction. Composition gives the best thermal performance was made of mixed ELV core materials of ratio 50%PC:50%PU, it has a thermal conductivity value of 0.1776 W/mK. The transparency data were obtained using Haze-gard plus haze meter. The best luminous transmittance value was exhibited by P2 (100% PC), 67.47%. The best clarity value and haze value were shown by P6 (25% PC: 75% PU), 55.13% and 52.6% respectively. ELV waste can be recycled to develop useful sustainable thermal insulation to improve thermal and optical transparency performance of buildings as a substitute for conventional materials which have a relevance for future façade concepts.

Redesign of the trajectory within a complex intersection for visible light communication ready connected cars

To serve the changing needs of road traffic control, the road space and road structure surrounding an intersection have evolved into complex forms. The redesign of the trajectories, though complex, can be accomplished by the application of methods for navigation, guidance, and combination of expert knowledge of road traffic control of vehicles, using a concept of request/response in a two-way-to-way traffic light-controlled crossroad. The communication between the infrastructures and the vehicles (I2V), between vehicles (V2V), and from the vehicles to the infrastructures (V2I) is performed through visible light communication (VLC) using the street lamps and the traffic signaling to broadcast the information. Vehicle headlamps and taillights are used to transmit data to other vehicles or infrastructures allowing digital safety and data privacy. Data are encoded, modulated, and converted into light signals emitted by the transmitters. Tetra-chromatic white sources are used providing a different data channel for each chip. As receivers and decoders, silicon/carbon wavelength division multiplexer devices, with light filtering properties, are used. The primary objective is to control the arrival of vehicles to an intersection and schedule them to cross at times that minimize delays. A further objective is to allocate delays between left-turns and forward movements, moderating the speed and slot between vehicles traveling in these directions, maintaining a safe distance from one to another. Pedestrians and bicycles are incorporated. A I2V2V2I traffic scenario is established. A phasing traffic flow is developed as a proof of concept. The experimental results confirm the cooperative VLC architecture showing that communication between connected cars is optimized.

Dynamic Adjustment and Distinguishing Method for Vehicle Headlight Based on Data Access of a Thermal Camera

In recent years, more and more traffic accidents have been caused by the illegal use of high beams. Therefore, the distinguishing of the vehicle headlight is vital for night driving and traffic supervision. And then, a method for distinguishing vehicle headlight based on data access of a thermal camera was proposed in this paper. There are two steps in this method: The first step is thermal image dynamic adjustment. In thermal image dynamic adjustment, the details of thermal images were enhanced by adjusting the temperature display dynamically and fusing features of multi-sequence images. The second step is vehicle headlight dynamic distinguishing, and features of vehicle headlight were extracted by YOLOv3. Then, the high beam and low beam were further distinguished by the filter based on the position and proportion relationship between the halo and the beam size of vehicle headlights. In addition, the accessed thermal image dataset during the night was used for training purposes. The results showed that the precision of this method was 94.2% and the recall was 78.7% at a real-time speed of 9 FPS. Compared with YOLOv3 on the RGB image, the precision was further improved by 11.1%, and the recall was further improved by 5.1%. Dynamic adjustment and distinguishing method was also applied in SSD network which has good performance in small object detection. Compared with SSD network on the RGB image, the precision was improved by 8.2% and the recall was improved by 4.6% when SSD network was improved by this method.

Recognition Method for Speed Limit Signs and its Applicability in Recognition of Vehicle Entry Prohibition Signs at Night

Recently, cameras with sensing technology have been used in vehicles to prevent traffic accidents. Although vehicle drivers can visually notice road signs, a recent study developed a recognition system for road signs to prevent traffic accidents. However, this system does not always perform the intended operation and encounters issues if the vehicle is driven at night, the road environment is bad, or the sign is discolored due to aging. Furthermore, the death rate due to speed violations at night is higher compared with that due to other traffic violations. The drivers and existing systems may have difficulties recognizing these signs as they are susceptible to other lights on the roads, such as traffic lights, streetlights, and vehicle headlights at night. Therefore, we propose a recognition method for speed limit signs that are difficult for drivers to recognize at night. In addition, the proposed method is applied to recognize vehicle entry prohibition signs at night. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Beam Pre-Shaping Methods Using Lenslet Arrays for Area-Based High-Resolution Vehicle Headlamp Systems

High-resolution light distributions are lately in demand for vehicle headlamp systems as an innovative lighting approach. This lighting approach can realize functionalities, such as precise glare avoidance and on-road projection, which are useful for improving traffic comfort and safety. For achieving the required high-resolution light distribution, area-based projection technologies, such as DMD, LCD, and LCoS, are considered to be integrated into such headlamps. These projection devices demand rectangular illumination areas with specific light distributions to fulfill the requirements for illumination efficiency and performance in headlamp systems. Lenslet arrays, based on the principle of Köhler illumination, can effectively homogenize the light and shape it into rectangular shapes simultaneously. Such components are widely used in projection applications. However, they also show functional potentialities to be applied in high-resolution headlamps. This paper explains the design principles and methods of lenslet arrays for beam pre-shaping in headlamp systems. It validates the homogenization using a self-designed and manufactured lenslet array in a demonstrator in the first place. Afterward, this paper introduces two new methods for the centralized beam shaping required by some headlamps. These methods are validated by optical simulations.

Haar와 Lab 색상 특징 기반의 야간 차량 전조등 및 후미등 감지 알고리즘

온로드 차량 감지는 지능형 운송 시스템에서 중요한 기술이다. 일광 상태에서 차량감지 시스템은 색상, 모양 또는 일반적인 차량 패턴과 같은 차량의 외관 정보를 활용하여 높은 정확도를 얻을 수 있다. 그러나, 야간에는 대부분의 차량 외관 특징들은 차량감지를 하기에는 불충분하고 신뢰성이 낮아, 전조등 및 후미등이 차량감지를 위한 신뢰할 수 있는 특징이 된다. 본 논문에서는 야간 차량 전조등 및 후미등 영역을 모두 검출하는 방법을 제안한다. 감지의 처음 단계로 회색조 이미지를 사용하는 Haar 특징과 Lab 색상 특징을 결합한다. 이후 결합된 두 특징은 Multi-Adaboost를 통하여 훈련된다. 제안된 감지 알고리즘은 실험을 통하여 전조등과 후미등 감지 성능에서 우수함을 증명하였다.

A Case study on Automatic Smart Headlight System for Accident Avoidance

The recent developments in the sensors and the IoT (Internet of Things) technologies are transforming many of the devices smart and to act independently or with minimum human intervention. The researchers are identifying many existing systems and trying to address the current problems in the functionalities or limitation of these existing devices. The researchers are also working to discover the technologies which are very expensive and not in the reach of the common man so that it would be possible to bring out the better solution for the ever-growing mankind with suitable affordability.
 The functionalities of IoT are not limited to a specific field and outweigh the other traditional methodologies; it is being used in many of the life saving applications in recent days including health care, emergency care, accident-aids and many more. The recent survey reveals that the accidents percentage is high between evening 6 to morning 6 compared to the day time. The top most reason for these accidents are temporary blindness of the drivers caused by the headlights of the opposite side vehicles. Another study shows that the accident chances are high during raining or foggy season than a normal day. To avoid these accidents, we are mainly depending on the fog lights. There are few technologies already existing with the luxury cars but these are highly expensive to be adopted in the economy cars. 
 This paper proposes the technology which can be used to make the headlight system to be smart to avoid many existing reasons for the night time or bad weather accidents on road. The researchers’ main objective is to design an economic Automatic Smart Headlight system which can be used by the automobile industry. The second main objective is to design the headlight system for the two and three wheelers also, which is not actually considered by many of the researchers or the automobile industries.

Influence of Background Spectral Distribution on Perceptions of Discomfort Glare

<div class="section abstract"><div class="htmlview paragraph">The advent of light-emitting diode (LED) technology for automotive lighting allows flexibility of the spectral distribution of forward headlighting systems, while meeting current requirements for “white” illumination. As vehicle headlights have become whiter (with more short-wavelength light output) over the past several decades, their potential impacts on visual discomfort for oncoming and preceding drivers have been hotly debated. It is known that a greater proportion of short-wavelength energy increases discomfort glare, and that increasing the background light level (e.g., through roadway lighting) will decrease perceptions of discomfort. More recently it has been demonstrated that the visual system exhibits enhanced short-wavelength sensitivity for perceptions of scene brightness. As a result, roads illuminated by light sources with higher correlated color temperatures (CCTs) will be judged as appearing to be brighter than those illuminated to the same light level by sources with lower CCTs. The present laboratory study was conducted to identify whether the increased scene brightness of a road illuminated with greater short-wavelength light helps to mitigate discomfort glare more than the same scene illuminated to the same light level, but with less short-wavelength light. The results indicate that the spectral distribution of the background plays little role in the degree to which it lessens discomfort glare. The implications of these results for vehicle and road lighting practices are discussed.</div></div>

Development and implementation of a laser headlight system for electro‐optic characteristic measurement and comparison

SummaryIn this study, a laser headlight driving controller (LHDC) using the controller area network (CAN)‐bus communication system was developed and implemented for vehicle headlight applications. To observe temperature variations that influence the forward‐bias voltage and optical power of laser diodes, the laser diode was placed in an ambient temperature‐testing chamber to measure the electro‐optic characteristics and calculate the electro‐optic conversion efficiencies. The optical power and conversion efficiency values obtained at different temperatures (from negative to positive temperatures) when optical power adjustment was executed using analog and pulse‐width modulation technologies were compared. Moreover, a human‐machine operating interface was developed using the LabVIEW software. Therefore, the LHDC and laser optical power can be controlled using a computer through the CAN‐bus communication system to control the LHDC and monitor it.

Optimization of InGaN-based LED Package Structure for Automotive Adaptive Driving Beam Headlamp

We investigated the luminance, thermal, and thermo-mechanical properties of vertical (V)-LED and flip-chip (FC)-LED packages with different white silicones for a vehicle head lamp application. The FC-LED package showed higher equivalent maximum stress than the V-LED package. For example, the equivalent maximum stresses for the FC-LED package with white silicone (WR-3020) were 6.05 and 2.45 MPa at −45 and 125 °C, respectively, whereas those for the V-LED one with WR-3001 were 1.09 and 1.56 MPa. Irrespective of currents, the V-LED packages exhibited lower thermal resistance (Rth) than the FC-LED package. The V-LED package showed 25.3% lower Rth value (junction to PCB) at 1000 mA than the FC-LED package. The FC-LED packages illustrated higher luminous flux drop-rate at 85 °C than the V-LED package. The V-LED packages revealed lower surface temperature than the FC-LED package. The contrast ratio depended on the package structures and white silicone coating widths. The packages with the wider edge-coating width had higher luminance and the V-LED packages exhibited higher luminance. The luminous flux maintenance rate was degraded by 0.9%–2.9% after 1000 h. The V-LED package with WR-3001 showed the best performance, while the FC-LED package with WR-3020 displayed the lowest performance.

Improved Leakage and Output Characteristics of Pixelated LED Array for Headlight application

We investigated the effects of etching conditions on the performance of light-emitting diodes (LEDs) of various sizes aimed at vehicle headlamp applications. Photoluminescence (PL) images showed that after wet etching, the percentage of bad LED arrays significantly increased from 75% to 94%, and the leakage current at −5 V significantly increased from 1.14 × 10−9 A to 5.02 × 10−6 A. It was shown that plasma etching turned an Ag layer into Ag particles, the size and density of which depended on the treatment time and Ag layer thickness. These Ag particles served as micro-masks during dry etching. Plasma etching produced relatively uniform hillocks of diameters 0.9–1.43 μm and heights 0.85–2.5 μm. Moreover, the PL images showed that dry etching did not degrade the LED arrays. Furthermore, the light output power of the dry-etched LEDs was higher than that of the wet-etched LEDs. For example, the output power levels of the dry-etched LEDs (chip sizes: 240 × 290 μm2, 240 × 490 μm2, and 490 × 1190 μm2) at 100 mA were 20.4%, 15.0%, and 11.2% higher than those of the corresponding wet-etched LEDs, respectively. Moreover, we demonstrated a vehicle headlamp unit consisting of Ag-particle-based plasma-etched LEDs.