The advance of automated vehicles imposes increasing requirements on the sensor system of vehicles. Besides the ongoing development of perception algorithms, different hardware approaches exist in order to improve the detection of infrastructure and road users. In the far-field in front of the vehicle, the detection of infrastructure and road users relies on camera and LiDAR systems. However, the reliability of both systems is influenced by weather conditions, especially due to reflections from snow, rain, or fog and the camera by the ambient lighting as well. Optimized algorithms are implemented to improve the vision of both systems but limitations remain. RaDAR is proven to work more reliably in adverse weather conditions but struggles in providing sufficient data for detailed object classification. In combination with data fusion, the sensor systems can provide a partly redundant perception of the road and its users. This paper aims to provide a proof of concept for the improvement of the vision of camera systems in low light by using active NIR illumination. For this purpose, the spectral emission of visible and near-infrared sources is compared with the sensitivity of a camera. Considering regulatory emission limits, an optimal wavelength for additional NIR lighting is determined. Based on the determined wavelength we research the correlation between the output power of the sources and the camera’s perceived brightness and introduce possible applications for the additional NIR illumination
Additive Manufacturing of glass opens up new possibilities for the design and integration of optical components. By varying the shape and size of optical elements, optical systems specifically adapted to various applications can be fabricated cost-effectively. The Laser Glass Deposition (LGD) process uses a CO2 laser with a wavelength of 10.6 μm to locally generate temperatures above 2000 °C in fused silica fibers. This enables the Additive Manufacturing and Rapid Prototyping of glass by melting and then layer-by-layer deposition of fibers. However, these high temperatures can result in very high residual stress in the material. The development of a coaxial LGD process aims for a more uniform heating of the glass fiber during the printing process in order to enable a direction-independent process and to reduce the residual stresses within the printed components. In this work, a novel concept for the coaxial LGD process and its successful experimental application is presented. Further, a numerical simulation model is developed to describe the temperature distribution in the glass fiber during the coaxial LGD process. Based on experimental results and on the numerical simulation, the potentials and challenges of the coaxial LGD process are discussed.
Due to their exibility, highly transparent silicone materials offer potentials for the development of adjustable optics. Previously realized mechanisms for changing the focal length of a solid silicone lens applied discrete points of force to mechanically deform the geometry. This article describes an approach to adjust the focal length of silicone lenses quickly and precisely. The chosen approach aims for a minimal number of moving components to provide reliability and reduced complexity. A contactless and stepless adjustment is realized by using electromagnetic control. To determine the functionality of the lens, the tunable range of the focal length will be investigated.
Matrix-LED systems offer different functionalities to increase road safety, e.g. glare-free high beam and marking light. Shortly after their introduction, efforts have been made to increase the amount of pixels. One of the results is the EVIYOS LED consisting of 1024 individually controllable pixels, which practically set the stage for pixel light systems. Current efforts to implement high-resolution pixel light systems are focused towards the exploration of an efficient light source in combination with the use of spatial light modulators. One approach to implement high-resolution pixel light systems is the use of LED arrays as a light source to illuminate a DLP. Unlike video projectors which require a homogeneous illumination of the DLP in order to obtain a homogeneous projection, headlamps require an inhomogeneous light distribution with high illuminance in the center. In order to receive a high system efficiency preforming the desired illuminance onto the active area of the modulator is advantageous. To further increase the systems efficiency an imaging illumination of the DLP, where the images of the emission surfaces of the LEDs are superposed onto the active area of the DLP, is worthwhile. In this paper, concepts for imaging and non-imaging illumination strategies of a DLP for high resolution headlamps will be introduced. For both illumination strategies the most promising concept will be selected to set up an optical system to illuminate a DLP. The paper concludes with a comparative analysis of the imaging and non-imaging optical system with regards to the system architecture and system efficiency.
Research reveals that visual information forms the major portion of the received data for driving. At night -owing to the, sometimes scarcity, sometime inhomogeneity of light- the human physiology and psychology experiences a dramatic alteration. It is found that although the likelihood of accident occurrence is higher during the day due to heavier traffic, the most fatal accidents still occur during night time. How can road safety be improved in limited lighting conditions using DMD-based high resolution headlamps?
DMD-based pixel light systems, utilizing HID and LED light sources, are able to address hundreds of thousands of pixels individually. Using camera information, this capability allows 'glare-free' light distributions that perfectly adapt to the needs of all road users. What really enables these systems to stand out however, is their on-road image projection capability. This projection functionality may be used in co-operation with other driver assistance systems as an assist feature for the projection of navigation data, warning signs, car status information etc. Since contrast sensitivity constitutes a decisive measure of the human visual function, here is then a core question: what distributions of luminance in the projection space produce highly visible on-road image projections?
This work seeks to address this question. Responses on sets of differently illuminated projections are collected from a group of participants and later interpreted using statistical data obtained using a luminance camera. Some aspects regarding the correlation between contrast ratio, symbol form and attention capture are also discussed.
Highly adaptive light sources such as LED arrays have been surpassing conventional light sources (halogen, xenon) for automotive applications. Individual LED arrangements within the array, high durability and low energy consumption of the LEDs are some of the reasons. With the introduction of Audi's Matrix beam system, efforts to increase the quantity of pixels were already underway and the stage was practically set for pixel light systems. Current efforts are focused towards the exploration of an optimal LED array density and the use of spatial light modulators.
In both cases, one question remains - What arrangement of LEDs is the most suitable in terms of light output efficiency for a given lens geometry? The radiation characteristics of an LED usually shows a Lambertian pattern. Following from the definition of luminous efficacy, this characteristic property of LEDs has a decisive impact on the lens geometry in a given array. Due to the proportional correlation between the lens diameter and the distance of LEDs emission surface to the lens surface. Assuming a constant viewing angle an increase of the distance leads to an increase of the lens diameter.
In this paper, two different approaches for an optimized LED array with regards to the LED arrangement will be presented. The introduced designs result from one imaging and one non-imaging optical system, which will be investigated. The paper is concluded with a comparative analysis of the LED array design as a function of the LED pitch and the luminous efficacy.
High-resolution vehicle headlamps represent a future-oriented technology that increases traffic safety and driving comfort in the dark. A further development to current matrix beam headlamps are LED-based pixellight systems which enable additional lighting functions (e.g. the projection of navigation information on the road) to be activated for given driving scenarios. The image generation is based on spatial light modulators (SLM) such as digital micromirror devices (DMD), liquid crystal displays (LCD), liquid crystal on silicon (LCoS) devices or LED arrays. For DMD-, LCD- and LCoSbased headlamps, the optical system uses illumining optics to ensure a precise illumination of the corresponding SLM. LED arrays, however, have to use imaging optics to project the LED die onto an intermediate image plane and thus create the light distribution via an apposition of gapless juxtapositional LED die images. Nevertheless, the lambertian radiation characteristics complex the design of imaging optics regarding a highefficiency setup with maximum resolution and luminous flux. Simplifying the light source model and its emitting characteristics allows to determine a balanced setup between these parameters by using the Etendue and to ´ calculate the maximum possible efficacy and luminous flux for each technology in an early designing stage. Therefore, we present a calculation comparison of how simplifying the light source model can affect the Etendue ´ conservation and the setup design for two high-resolution technologies. The shown approach is evaluated and compared to simulation models to show the occurring deviation and its applicability.
HID, LED and laser-based high resolution automotive headlamps, as of late known as ‘pixel light systems’, are at the
forefront of the developing technologies paving the way for autonomous driving. In addition to light distribution
capabilities that outperform Adaptive Front Lighting and Matrix Beam systems, pixel light systems provide the possibility
of image projection directly onto the street. The underlying objective is to improve the driving experience, in any given
scenario, in terms of safety, comfort and interaction for all road users. The focus of this work is to conduct a short survey
on this state-of-the-art image projection functionality.
A holistic research regarding the image projection functionality can be divided into three major categories: scenario
selection, technological development and evaluation design. Consequently, the work presented in this paper is divided into
three short studies. Section 1 provides a brief introduction to pixel light systems and a justification for the approach adopted
for this study. Section 2 deals with the selection of scenarios (and driving maneuvers) where image projection can play a
critical role. Section 3 discusses high power LED and LED array based prototypes that are currently under development.
Section 4 demonstrates results from an experiment conducted to evaluate the illuminance of an image space projected
using a pixel light system prototype developed at the Institute of Product Development (IPeG).
Findings from this work can help to identify and advance future research work relating to: further development of pixel
light systems, scenario planning, examination of optimal light sources, behavioral response studies etc.
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