LED Headlamp Research Articles

Refractive blur’s influence on discomfort glare perception from white LED headlights at night

This study examined the effects of refractive blur on discomfort perception caused by peripheral glare from white LED passing (low)-beam headlights at night. The study compared two levels of binocular blur (+0.50 diopter [D] and +1.00D) against a baseline of optimal refractive correction. Thirty participants (mean age 21.3±1.6 years; range 20–24 years) simulating a driving position assessed discomfort from glare sources (headlights of oncoming vehicles) located at 40 and 20 m distances using the de Boer scale. The study found that, with a blur of +0.50D, discomfort glare from white LED headlights did not significantly differ from the baseline regarding de Boer scores. However, with a blur of +1.00D, de Boer scores significantly decreased, indicating increased discomfort glare compared with the baseline for all distances (P=0.004). These results suggest that refractive blur may contribute to an increased perception of discomfort glare during nighttime driving.

Some biological and morphological aspects of Eriphia verrucosa (Forskål, 1775) in the eastern Adriatic Sea

Aim: To investigate and describe the length-weight relationship and sex ratio of the species Eriphia verrucosa in the eastern Adriatic and to determine whether there is external dimorphism by morphometric analysis of the body. Methods: All samples were collected in the coastal area in the intertidal zone of Kaštela Bay (Split-Dalmatia County, Croatia). The sample catching was done at night after 10 p.m. with a hand net and an LED headlamp; afterwards, each specimen was weighed, prepared for further processing and frozen. The processing of each specimen included sex determination and detailed morphometric measurements. In females, a total of eight morphometric measures were measured and additionally the length of the gonopods in males. For each morphometric measure except gonopod length (GL), the average value and the corresponding 95% confidence interval were determined. Results: A total of 73 individual specimens of E. verrucose were sampled, of which 35 were males and 38 were females. The gender ratio was 0.92:1 in favor of females (P = 0.726). The largest body weight measured during this research was a male with a mass of 263.6 g, and the smallest was also a male with a weight of 7.3 g. The largest number of individuals belonged to the length class of 45–50 mm. Sexual dimorphism between males and females was recorded for all morphometric measures. According to the b coefficient of length-weight yield, the growth of E. verrucosa can be characterized as negatively allometric. Conclusions: In this research, the biological characteristics of the species E. verrucosa in the eastern Adriatic were analyzed. The length-weight ratio (CL-W) for the total sample was W = 0.0076 × CL2.5086, for males W = 0.0078 × CL2.5116 and for females W = 0.0169 × CL2.2911. Based on the length-weight ratio, sex ratio and the morphometric analysis of the body, sexual dimorphism is documented, which was not previously found for the warty crab in that area.

Relationship of Braking Distance and Rear Headlight on Highways

It is known that the rear headlights have a direct effect on the braking distance on highways. Because when drivers see the braking light of the taillight, they enter the reaction process and apply the braking in the vehicle they are in. The sooner they receive the warning, the sooner they can braking. Since the current regulations do not consider the time, it takes for the rear headlight to reach the driver’s eyes, the braking times of the flocks differ in the face of LED, halogen, and xenon headlights. Even a small delay at high speeds increases the risk of hitting the vehicle in front. LED headlights give instant light, while halogen headlights 0.2 s and xenon headlights respond up to 1 s later. This study investigated the variation of braking distance for these headlight types. Accordingly, it has been concluded that the use of halogen and xenon headlights in taillights poses a danger to life and property safety and that such lamps contribute negatively to rearend collisions.

Understanding Cu Sintering and Its Role on Corrosion Behaviour for High-Temperature Microelectronic Application

There has been a significant rise in interest from academic and industry communities on copper nano and micro-particles-based sinter pastes for harsh environment die attach. However, sintering these particles is a complex process which is affected by many parameters, such as (i) particles size, shape, and distribution, (ii) sintering temperature, pressure, environment, and (iii) organic compounds used for the paste formulation. In literature, various research groups demonstrated that sintered copper layer can achieve good electrical conductivity and high strength. In our previous research [1, 2], we explained that microscale etched flakes are also capable of shear strength >30Mpa while sintering with 10 MPa bonding pressure at 275°C for just 1 minute with negligible paste cost (in comparison to silver paste). However, very limited knowledge exists on literature about corrosion behaviour in sintered copper interconnects. This, from experience in the industry with silver sintering has proven to be critical to applications. For examples in high power LED headlamp applications, minor exposure to residual Sulphur emerging from vulcanized rubber seals has been observed to cause corrosion in silver sintered interconnects. Therefore, corrosion and its impact on performance and reliability must be considered, especially for safety critical applications. For this reason, we have studied the relationship between copper sintered samples and corresponding corrosion behaviours and compared again to pure copper (conventionally produced). The corrosion resistance of the samples in salt water was assessed via various electrochemical analysis techniques and correlated with sintered microstructure. Sample produced better corrosion resistance when fabricated with higher density (less porosity). However, in case of the microscale copper flakes-based interconnects, a pitting behaviour was observed. The sintered copper paste samples showed to be nobler than commercial copper. In addition, copper oxide and its role in accelerating/preventing oxidation is also studied.

Smart Headlight Dimmer using Raspberry Pi

Abstract: Driving in low-lighting conditions can raise several challenges that may affect your safety at night. Due to darkness, low visibility is the most frequent issue that drivers have at night. It will be difficult to see obstacles, pedestrians and vehicles on the road and another important problem is glare of Oncoming headlights from high intensity beams of xenon or LED headlights of the front facing vehicles. This will lead to temporary blindness for the drivers. In this situation driving the vehicle is a challenging task. It will be difficult to drive with the traditional headlights in such conditions. It poses a serious threat, and many accidents are caused by temporary blindness. According to the Indian statistics, more than 60% of accidents occur during night time and the main reasons behind those accidents is headlights problems. The abrupt brightness experienced by the travellers is known as the Troxler Effect. However, there is an option in every vehicle weather to keep the headlight either high or low when the vehicle is coming from the front side and this is called as upper and dipper system. Some of the drivers do follow this system as the car approaches them at night but a lot of them do not. Due to which it led to the problem of lack of visibility on the road due to constant glare of the headlights. Heavy vehicle’s (like trucks and buses) have extremely powerful headlights which produce very high intensity lights that in turn result in fatal accidents. Truck and bus drivers will ignore to reduce the headlight intensity when small vehicles are approaching them. As we analyse the current highway situation, most of the goods and passenger transportation occur during night. In lots of time These vehicles jeopardise the safety of other people. There is no such system available which can automatically high and low beam those headlights of heavy vehicles and even high beams of small vehicles. To resolve this problem, The System should be developed so that when a car or bike approaches another vehicle then there should be automatic change in the upper and dipper mode of the lights and reduce the light intensity. So that accidents due to headlights can be reduced.

Visual and non-visual responses of drivers to simulated LED headlights varying in correlated colour temperature

This study aimed to investigate the impact of automotive headlights of different correlated colour temperatures (CCT) on the visual and non-visual performance of drivers. Forty drivers participated in the study, driving in a simulated night road for 45 min in three sessions. The LED headlights had CCTs of 3176 K, 4358 K and 6923 K, with an illuminance of 5 lx perpendicular to the participants’ eyes. Heart rate variability (HRV), psychomotor vigilance task and Karolinska sleepiness scale were measured before and after driving. At the end of the trials, achromatic far and near visual acuity tests, as well as achromatic far and near contrast sensitivity tests, were conducted. The study revealed that CCT did not affect achromatic far and near visual acuity. However, CCT had an impact on achromatic near and far contrast sensitivity, with higher CCT resulting in improved achromatic contrast sensitivity. As the CCT decreased, participants exhibited increased reaction time, made more errors, and reported higher sleepiness. The most significant physiological changes in HRV, including alterations in low frequency (LF), high frequency (HF) and LF/HF, were observed at lower CCT. The findings of this study suggest that both the visual and non-visual performance of drivers were enhanced when high CCTs were used for automotive LED headlights.

Design of Multi-module LED Headlamp of Vehicle Under Federal Motor Vehicle Safety Standard

Design of Multi-module LED Headlamp of Vehicle Under Federal Motor Vehicle Safety Standard

Influence of Ambient Temperature on Optical Characteristics and Power Consumption of LED Lamp for Automotive Headlamp

In this study, the authors propose a method for evaluating the influence of ambient temperature (Ta) on the optical characteristics and power consumption of a LED lamp used for the automotive headlamp, which helps the designer to figure out the acceptable range of the ambient temperature for the LED lamps to work well in the practical case. The LED lamp was fixed on the test holder and placed in a fixed position in the air circulation temperature control oven to measure the illuminance, spectrum in three different directions, and power consumption under various Ta. The experimental results indicate that Ta has little effect on the correlated color temperature (CCT), chromaticity coordinates, and angular distribution of the emitting light. In contrast, Ta has a significant effect on the lamp’s resistance, thus affecting illuminance and power consumption. When the Ta increased from 30 °C to 60 °C, the illuminance of the low beam and high beam decreased on average by 16.6% and 21.7%, respectively, while the power consumption of the low beam and high beam decreased on average by 21.4% and 22.2%, respectively. The drop in the luminous flux output indicates the probability of originally qualified automotive LED headlamps becoming unqualified in high Ta.

Analysis and Comparison of Sliding Mode Controller for the Boost Driver in LED Headlamps

In this paper, the performance of several sliding mode control strategies used for the boost driver in LED headlamps is analysed and compared. At first the topology, control framework, and mathematical model of the boost LED driver is presented. Based on the mathematical model, a traditional differential sliding mode control law, a terminal sliding mode control law with finite convergence time, and a 2nd-order sliding mode control law with the Super-Twisting algorithm are derived and designed. Finally the simulation models of these sliding mode control laws are built. Simulation results show that the terminal sliding mode control has a faster convergence speed than the traditional differential sliding mode control. And the 2nd-order sliding mode control has a fastest convergence speed and low chattering, but the control result has a certain overshoot.

Spectroscopic Performance of Otoscopes during Otoscopic Examination by LED Headlight

Spectroscopic Performance of Otoscopes during Otoscopic Examination by LED Headlight

Spectroscopic Performance of Otoscopes during Otoscopic Examination by LED Headlight

Spectroscopic Performance of Otoscopes during Otoscopic Examination by LED Headlight

Effect of headlamps on the irradiation characteristics of automotive headlights

In this study, we investigated and analyzed the correlation between high beam and low beam and the low beam irradiation characteristics of LED head lamps using a headlight tester based on each inspection standard for automotive headlights. From the experimental results, it was confirmed that the irradiation characteristics switched to the low beam did not fully satisfy the inspection criteria with respect to the appropriate irradiation direction and luminosity of the high beam. It was also found that when the halogen lamp was changed to the LED head lamp in the low beam of the 4-lamp type headlight, the change in the irradiation direction was small, but the increase in the irradiation light intensity differed depending on the vehicle.

Determination of Speed-Dependent Roadway Luminance for an Adequate Feeling of Safety at Nighttime Driving

The purpose of this work is to determine as a function of velocity the minimal roadway luminance that is required to be judged as being bright enough for a driver to perform a nighttime driving task with an adequate feeling of safety. In this context, it shall also be evaluated which areas of the vehicle forefield are most crucial for the driver’s general brightness perception. A field study with 23 subjects and dimmable LED headlights was conducted, in which the subjects were given the task to assess their perceived brightness for different luminance levels caused by the headlights’ low-beam distribution in the vehicle’s forefield on a 5-step rating scale. The experiments were repeated for three different driving velocities of 0 km h−1 (static case), 30 km h−1, and 60 km h−1, respectively. Results for the static case indicate that, for the roadway to be perceived as bright enough by 50% of the subjects, an average roadway luminance of 0.88 cd m−2 is required in an area up to 32 m in front of the vehicle. Furthermore, a significant effect of driving speed is observed. For example, at 60 km h−1, the luminance must be increased to 1.54 cd m−2 to be still perceived as sufficiently bright by 50% of the subjects.

The comparison of vehicle headlamps

The aim of this article is the comparison of vehicle headlamps in terms of pedestrians' visibility at nighttime conditions. The study was designed to gain results, which could serve as a basis for the pedestrian-vehicle accident analysis in terms of visibility during night drive. For this study were used comparable vehicles (same vehicle type and model year) with different headlamps type. Three different headlamps (halogen, xenon and LED headlamps) were used for the analysis. Experiments were carried out under similar conditions (straight road, nighttime, no disturbing factors). During a series of static tests, the vehicle approached at predefined distances to the figurant - pedestrian standing on the right side of the roadway. For the luminance analysis were used Luminance Distribution Analyser LumiDISP - software for analysing the luminance conditions based on evaluation of image data from digital photos.

Automatic (Headlight) Beam Controlling module for two-wheelers

Abstract: Automatic High Beam controller is a device made due to the rising number of accidents at night because of LED headlamps temporarily affecting the vision of the driver on the opposite lane. According to AAA, LED lights do a much better job of illuminating the roadway, particularly in the low-beam application versus a halogen reflector at 150 feet more during testing. But, still, that brings the max vehicle speed to about 52 miles an hour, which is still falling short of highway speeds. So, the users are suggested to drive with high beam on if there is no oncoming traffic within a reasonable distance and the roadway is improperly lit. But in practice most people drive with the high beam settings in places with or without traffic great from the user's standpoint. However, even on low beam, they have such a high intensity that on 2-lane roads, especially when the oncoming driver of a car or small pickup approaches the LED equipped truck at night, in rain, fog, or snow the oncoming driver is blinded at a level equal to or greater than if the LED equipped vehicle were using conventional halogen high beams. This device is made without distance or ambient lighting being deciding factors and entirely based on user’s discretion. The transmitter model is fitted with a button that sends a signal to the receiver model using nrf24L01 modules and AT Mega 8 microcontroller (programmed using Arduino UNO). The pressing of button causes the state of the button to be set to HIGH. This signals the receiving circuit to set the LED pin to LOW. Therefore, the High Beam is set to Low Beam for 5 seconds when the impulse is received. Due to the use of H4 C6 headlamps which are rated for 36W with a minimum power requirement of 12W an adapter was connected to convert 220V AC supply to 12V, 3A DC supply for the LED and the rest of the circuit.

색온도가변 LED 전조등이 악천후 조건에서 차량과 노면 표적의 시인성에 미치는 영향

A quantitative measurement was conducted to find out the effect of CCT tunable LED headlamp on the targets of vehicle and road surface under artificial weather environment. For this, a CCT tunable headlamp with different CCT from 3500K to 6500K and diverse targets like vehicle reflectors, a license plate, and lanes were used. Experimental weather conditions consisted of clear, light fog, heavy fog, light rain, and heavy rain. We measured the luminance of the targets and backgrounds, and then calculated the contrast ratio based on their luminance. The result showed that the low CCT headlamp was better for the visibility of the targets on vehicle and road surface, particularly in reflectors, than the high CCT headlamp. We discussed the influence of target visibility by CCT tunable headlamps and their applicability to vehicles in adverse weather conditions.

Experimental investigation on active heat sink with heat pipe assistance for high-power automotive LED headlights

Compared with traditional halogen headlights, LED has obvious advantages in energy consumption, photoelectric efficiency, luminous flux, and life span. However, the thermal management of LEDs is usually limited by space. This paper proposes a novel design of a heat pipes assisted compact heat sink (HPACHS) for LEDs to reduce the LED junction temperature. The thickness of the double-sided LED can be reduced to 1.5 mm since there is no multilayer structure, and the double-sided LED headlight can emit more concentrated light. The results show that HPACHS can cool the 34 W LED substrate to 100.32 °C at an ambient temperature of 26 °C, with a cooling fan power of only 0.267 W and a thermal resistance from the LED base to the environment of 2.17 °C/W. The minimum thermal resistance of HPACHS is 1.86 °C/W, with a heat load of 18 W. The heat sink is 71 mm long and the maximum outer diameter is 38 mm. Therefore, as an efficient and high-power LED cooling device, this compact active radiator has sufficient application prospects and can be applied to the thermal management of automobile headlights.

Design and implementation of VLC-based smart barrier gate systems

In this paper, an innovative and smart Visible Light Communication (VLC)-based Intelligent Transportation System (ITS) is designed. The proposed system uses vehicle LED headlamps as a remote controller. Differential Pulse Position Modulation (DPPM) is utilized for the sake of its asynchronicity. The system features an innovative optical interference cancellation mechanism to address the unwanted variable DC component and AC line noise in the received signal. The feasibility of the proposed system is demonstrated experimentally in day and night conditions using an off-the-shelf LED headlights. The Bit Error Rate (BER) performance of the system in terms of angular position of the vehicle with respect to the VLC receiver at different link ranges is evaluated. The prototype successfully demonstrates the smart control over the barrier gate using the ATmega microcontrollers family for the outdoor environment. BER of lower than 10-3 is achieved for a maximum link range of 4.4 meters.

High-Resolution Pixel LED Headlamps: Functional Requirement Analysis and Research Progress

High-resolution pixel LED headlamps are lighting devices that can produce high-resolution light distribution to adapt to road and traffic conditions, intelligently illuminate traffic areas, and assist drivers. Due to the complexity of roads and traffic conditions, the functional diversity of high-resolution pixel LEDs headlamps and traffic safety has come into question and is the subject of in-depth research conducted by car manufacturers and regulators. We summarize the current possible functions of high-resolution pixel LED headlamps and analyze ways in which they could be improved. This paper also discusses the prospect of new technologies in the future.

Minimum achievable height of a single-module LED low-beam projection headlamp.

Since the first full LED headlamp was introduced in 2007, technology has evolved townow provide enhanced performance, improved security, and memorable aesthetics. Further miniaturization has been continuously pursued to allow more advanced design options, but LED headlamp height has been stalled at around 40-60 mm for some years. Recently a total internal reflection-based low-beam module achieved an optical opening down to 20 mm. However, the small opening came with a housing envelope height that was larger than 40-60 mm. Conventional LED single modules are still more attractive in terms of cost and overall compactness, especially for low-cost, low-beam headlamps. A demanding question remains about the minimum achievable limit of a single-module LED low-beam projection headlamp consisting of an LED source, an elliptical reflector, a cutoff baffle, and a projection lens. Here, we answer that question using an analytical approach rather than attempt to base it on current applied design trials or parametric studies. First, we analytically investigated the baseline optical properties of an LED low-beam module in terms of geometrical optics and photometrical luminance transfer. During the analysis, we employed the ratio of the focal distances (m) of the elliptical reflectors as a design variable to efficiently consider geometrical similarities. Then we confirmed and extended the analytical results by numerical simulation, using ray-tracing software. Based on the results from the analytical and numerical analysis with low-beam regulations, we finally determined a suitable range of m (0.15-0.17), which satisfied the regulations, and found the best achievable height of a single module when m∼0.15 is 46 mm. The precise number will differ depending on the geometrical and ray-emitting properties of the LED applied, but our study provides a valid general framework for designing LED-based low-beam headlamps.