92 research outputs found
Lighting with laser diodes
Contemporary white light-emitting diodes (LEDs) are much more efficient than compact fluorescent lamps and hence are rapidly capturing the market for general illumination. LEDs are also replacing halogen lamps or even newer xenon based lamps in automotive headlamps. Because laser diodes are inherently much brighter and often more efficient than corresponding LEDs, there is great research interest in developing laser diode based illumination systems. Operating at higher current densities and with smaller form factors, laser diodes may outperform LEDs in the future. This article reviews the possibilities and challenges in the integration of visible laser diodes in future illumination systems. © 2013 Thoss Media & De Gruyter
Case study of liquid cooling of automotive headlights with hollow fiber heat exchanger
Thermal performance of small liquid cooling systems based on polymeric hollow fibers was experimentally studied for the cooling of automotive lighting components integrated with high power Light Emitting Diodes (LEDs). Firstly, the tests with control electric heaters on a printed circuit board (PCB) were performed to precisely measure the thermal performance. The cooling effect of liquid cooling system installed on the PCB board of Skoda Octavia 4 (SK38) and Skoda Enyaq (SK316) was tested as the second step. Results of the testing show that the proposed plastic radiators ensure efficient and uniform cooling of the PCBs and keep the LEDs operation temperature much below the recommended 110 C. As the heat generation is relatively small for liquid cooling (tens of watts), there is only 3–10 l/h flow rate of coolant needed, allowing to operate the plastic radiator with low velocity and pressure drops (below 1 kPa). Additionally, apart from excellent cooling, the tested polymeric radiators are about ten times lighter than their aluminium passive finned competitors
Temperature issues with white laser diodes, calculation and approach for new packages
Bright white light sources are of significant importance for automotive front lighting systems. Today's upper class systems mainly use HID or LED light sources. As a further step laser diode based systems offer a high luminance, efficiency and allow the realization of new dynamic and adaptive light functions and styling concepts. The use of white laser diode systems in automotive applications is still limited to laboratories and prototypes even though announcements of laser based front lighting systems have been made. But the environment conditions for vehicles and other industry sectors differ from laboratory conditions. There for a model of the system's thermal behavior is set up. The power loss of a laser diode is transported as thermal flux from the junction layer to the diode's case and on to the environment. There for its optical power is limited by the maximum junction temperature (for blue diodes typically 125 - 150°C), the environment temperature and the diode's packaging with its thermal resistances. In a car's headlamp the environment temperature can reach up to 80°C. While the difference between allowed case temperature and environment temperature is getting small or negative the relevant heat flux also becomes small or negative. In early stages of LED development similar challenges had to be solved. Adapting LED packages to the conditions in a vehicle environment lead to today's efficient and bright headlights. In this paper the need to transfer these results to laser diodes is shown by calculating the diodes lifetimes based on the presented model. © 2015 SPIE
Simulation of headlight cover lens de-icing and its application in automotive industry
Práce se zabývá výzkumem v oblasti odmrazování světlometu. Jejím cílem je vytvoření numerického simulačního modelu, který dokáže předpovídat průběh odmrazování, zároveň tak může odhalit nedostatky při návrhu světlometu. Na simulační modelu jsou testovány proměnlivé parametry, výsledkem práce je nalezení optimálních podmínek, které zajistí validní výsledky simulace při současné úspoře výpočetního času.The thesis will engage in research in headlight de-icing area. The aim is to create a numerical simulation model which is able to predict the course of a de-icing process as well as revealing shortcomings in the headlamp design. Variable parameters are tested on the simulation model, the aim of the thesis is to find the optimal conditions that will ensure valid simulation results while saving computational time.
A Survey of Positioning Systems Using Visible LED Lights
© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.As Global Positioning System (GPS) cannot provide satisfying performance in indoor environments, indoor positioning technology, which utilizes indoor wireless signals instead of GPS signals, has grown rapidly in recent years. Meanwhile, visible light communication (VLC) using light devices such as light emitting diodes (LEDs) has been deemed to be a promising candidate in the heterogeneous wireless networks that may collaborate with radio frequencies (RF) wireless networks. In particular, light-fidelity has a great potential for deployment in future indoor environments because of its high throughput and security advantages. This paper provides a comprehensive study of a novel positioning technology based on visible white LED lights, which has attracted much attention from both academia and industry. The essential characteristics and principles of this system are deeply discussed, and relevant positioning algorithms and designs are classified and elaborated. This paper undertakes a thorough investigation into current LED-based indoor positioning systems and compares their performance through many aspects, such as test environment, accuracy, and cost. It presents indoor hybrid positioning systems among VLC and other systems (e.g., inertial sensors and RF systems). We also review and classify outdoor VLC positioning applications for the first time. Finally, this paper surveys major advances as well as open issues, challenges, and future research directions in VLC positioning systems.Peer reviewe
Modelling and characterization of Quantum Dots as QLED devices for automotive lighting systems
This work reports the design, manufacturing and numerical simulation approach of an electroluminescent quantum dot light emitting device (QLED) based on quantum dots as an active layer. In addition, the electrical I-V curve was measured, observing how the fabrication process and layer thickness have an influence in the shape of the plot.
This experimental device enabled us to create a computational model for the QLED based on the Transfer Hamiltonian approach to calculate the current density J(mA/cm2), the band diagram of the system and the accumulated charge distribution. Thanks to the QLED simulator developed, it would be possible to model the device and anticipate the electrical performance in a theoretical design step before going to QLED manufacturing at the laboratory.
Eventually, particular automotive lighting system demonstrators were designed to integrate the theoretical and experimental research carried out in an industrial automotive product.Tesis Univ. Granada
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Prognostics and health management of light emitting diodes
Prognostics is an engineering process of diagnosing, predicting the remaining useful life and estimating the reliability of systems and products. Prognostics and Health Management (PHM) has emerged in the last decade as one of the most efficient approaches in failure prevention, reliability estimation and remaining useful life predictions of various engineering systems and products. Light Emitting Diodes (LEDs) are optoelectronic micro-devices that are now replacing traditional incandescent and fluorescent lighting, as they have many advantages including higher reliability, greater energy efficiency, long life time and faster switching speed. Even though LEDs have high reliability and long life time, manufacturers and lighting systems designers still need to assess the reliability of LED lighting systems and the failures in the LED.
This research provides both experimental and theoretical results that demonstrate the use of prognostics and health monitoring techniques for high power LEDs subjected to harsh operating conditions. Data driven, model driven and fusion prognostics approaches are developed to monitor and identify LED failures, based on the requirement for the light output power. The approaches adopted in this work are validated and can be used to assess the life of an LED lighting system after their deployment based on the power of the light output emitted. The data driven techniques are only based on monitoring selected operational and performance indicators using sensors whereas the model driven technique is based on sensor data as well as on a developed empirical model. Fusion approach is also developed using the data driven and the model driven approaches to the LED. Real-time implementation of developed approaches are also investigated and discussed
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