This PDF file contains the front matter associated with SPIE Proceedings Volume 10554, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

In recent years, lots of attentions have been paid to micro-LED based display technology. For next-generation display applications, micro-LED-display is expected to be more efficient, having larger color gamut, much brighter and very flexible. What’s more, the micro LED display technology could allow the integration of circuit and sensors for much higher refresh rate and fingerprint identification. However, there are still many challenges need to be overcome before an ideal micro-LED-display can be demonstrated. Making a micro-LED-display involves two major processing works: one is to make an array of very small LED chip with very good uniformity on wavelength and brightness; while the other one is to transfer this LED array to a display backplane with very high yield and low cost. To make a highly uniform micro-LED chip array, it is critical to have a uniform LED wafer since the binning of micro LED chips is not possible. In this work, a highly uniform 6 inch wafer suitable for micro-LED-display will be demonstrated. The percentage of wafer usage will be calculated. On the other hand, micro-LED chips with low leakage current level and good crystal quality are fabricated based on this wafer. After applying mass transfer process to the wafer, a high brightness, high efficiency RGB micro-LED-display with driver will also be demonstrated.

Energy efficient generation of white light has become an important issue in recent years. Technology of white-light emitting diodes (LEDs) is one of the promising directions. The main challenges in the LED production are understanding scattering, absorption and emission from ab-initio, and obtain chromaticity independent emission directions. Physical understanding of multiple light scattering in the LED can provide us with simple tools for extracting optical parameters of this system. We have studied the transport of light through phosphor diffuser plates that are used in commercial solid-state lighting modules (Fortimo). These polymer plates contain YAG:Ce+3 phosphor particles that both elastically scatter light and Stokes shift light in the visible wavelength range (400-700 nm). We excite the phosphor with a narrowband light source, and measure spectra of the outgoing light. The Stokes shifted light is spectrally separated from the elastically scattered light in the measured spectra. Using this technique we isolate the elastic transmission of the plates. This result allows us to extract the transport mean free path ltr over the full wavelength range by employing diffusion theory. Simultaneously, we determine the absorption mean free path labs in the wavelength range 400 to 530 nm where YAG:Ce+3 absorbs. The diffuse absorption (µ_a=1/l_abs ) spectrum is qualitative similar to the absorption coefficient of YAG:Ce+3 in powder, with the diffuse spectrum being wider than the absorption coefficient. We propose a design rule for the solid-state lighting diffuser plates.

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.

We have developed an ion beam assisted deposition (IBAD) texturing process for biaxially aligned films as substrates for GaN epitaxy. The IBAD process enables low-cost, large-area flexible metal foil substrates to be used as potential alternatives to single-crystal sapphire and silicon for GaN electronic devices. Epitaxial GaN films are grown by the MOCVD process on these engineered flexible substrates. We have achieved epi GaN films of several microns on polycrystalline metal foils that have in-plane and out-of-plane alignment of less than 1° FWHM and typical threading dislocation densities of 4-8 x 10^8/cm^2. We use the epitaxial GaN films on IBAD/polycrystalline metal foil as a template to deposit epitaxial multi-quantum well light emitting diode (LED) InGaN structures. From these layered structures we have successfully fabricated LED devices. These are the first LED devices fabricated directly on metal foil. We observe photoluminescence intensities from the LED structures up to 70% of those fabricated on sapphire. We will present data on performance of such devices and how these LED devices could be printed using a roll-to-roll process. This work was supported by the Department of Energy ARPA-E agency.

By increasing the Mg-doping level and hence the hole concentration in the p-AlGaN electron-blocking layer, the polarization field in this layer can be screened for reducing the potential barrier of hole and hence enhancing the hole tunneling efficiency such that the overall LED emission efficiency is increased. The increase of Mg-doping level is implemented based on an Mg pre-flow growth technique, in which Mg source is supplied into the metalorganic chemical vapor deposition chamber for several minutes before the growth of p-AlGaN or p-GaN. Based on a simulation study, we observe that the energy difference between the valence band-edge and the quasi-Fermi level of hole in the EBL is reduced by increasing the Mg-doping level in this layer such that the total hole density in the quantum wells is increased for enhancing the LED emission efficiency. Based on this technique, the high performance of an LED with the total p-type thickness as small as 38 nm is demonstrated. The surface plasmon coupling effects, including the enhancement of internal quantum efficiency, increase of output intensity, reduction of efficiency droop, and increase of modulation bandwidth, among the thin p-type LED samples of different p-type thicknesses are compared. These advantageous effects are stronger as the p-type layer becomes thinner. With a circular mesa size of 10 micron in radius, we achieve the record-high modulation bandwidth of 625.6 MHz among c-plane GaN-based LEDs.

Micro-light-emitting diodes (µLEDs) have attracted much attention in recent decades on account of their diverse applications, such as light sources for transparent displays, a headlamp for automobiles, a head-up display for military and aerospace areas. However, µLEDs suffered from a trade-off between fill factor (the ratio of emission area to pixel size) and the current density because each pixel of µLEDs is screened by p-electrode for current injection, reducing the effective emission area. We can expand the emission area by reducing the p-type electrode area, but it decreases the current density of the µLED. During the past few decades, many efforts have been attempted to enhance the light output power of the µLED by changing the size and shape of the pixel. However, there have been few fundamental breakthroughs in this trade-off issue. In this study, we offered the so-called ‘glass electrodes’ to solve this problem in µLEDs. AlN rod-shaped glass electrodes with high transmittance and local current path (nanofilaments) were applied as top electrodes of the µLEDs, to improve the fill factor by enhancing the light emission of the µLED. The current path in AlN thin film was produced by an electrical breakdown process. Compared to the µLEDs with ITO electrodes, our µLEDs with AlN rod-shaped electrodes exhibited higher light output power density (105 % at 300 mA) and brighter light emission per area (110 % at 10 mA). More details including the ohmic transport mechanism for current injection and analysis of nanofilament will be presented at the conference.

Nitride semiconductors are the key materials for solid-state lighting. Point defects may act as compensating centers, charge traps, or radiative or nonradiative recombination centers. Unintentional impurities often play an equally important role; for instance, carbon that is unavoidably incorporated during metal-organic chemical vapor deposition can act as a source of yellow luminescence. Theoretical advances now enable us to calculate the energetics as well as electronic and optical properties of point defects with unprecedented accuracy. We have developed a first-principles methodology to determine nonradiative carrier capture coefficients. Accurate calculations of electron-phonon coupling, combined with results for defect formation energies and charge-state transition levels, enable the calculation of nonradiative capture rates for electrons and holes and the evaluation of Shockley-Read-Hall coefficients. This approach allows us to identify specific defects that play a key role in limiting the efficiency of nitride semiconductor devices. ---Work performed in collaboration with A. Alkauskas, C. Dreyer, A. Janotti, J. Lyons, J. Shen, J. Speck, and D. Wickramaratne, and supported by DOE and NSF.

A strong limitation for the quantum efficiency of group III-nitride based light emitters is the spatial electron-hole separation due to the quantum-confined Stark effect (QCSE). To overcome this problem, Hönig et al. [1] proposed a concept, the Internal-Field-Guarded-Active-Region Design (IFGARD), which enables quasi electric-field free active regions in polar heterostructures. Here, we show how the encapsulation of the active region by additional guard layers results in a strong reduction of the built-in electric field in c-plane wurtzite nanostructures. In particular, we demonstrate experimental evidence for the successful realization of an IFGARD structure based on GaN/AlN heterostructures embedded in GaN nanowires. By means of power-dependent and time-resolved µ-photoluminescence (µ-PL) we experimentally proof the validity of the IFGARD structure. We managed to tune the emission of 4-nm-thick GaN nano-discs up to 3.32 eV at low excitation powers, which is just 150 meV below the bulk GaN bandgap [2]. Our results demonstrate an almost complete elimination of the QCSE in comparison to conventional structures which show approximately 1 eV red-shifted emission. The reduction of the QCSE results in a significant increase of the radiative exciton decay rates by orders of magnitude and demonstrates the potential of IFGARD structures for future light sources based on polar heterostructures. [1] Hönig et al., Phys. Rev. Applied 7, 024004 (2017) [2] Schlichting et al., arXiv:1707.06882 (2017).

Despite of only having 25 years so far, the efficiency of GaN-based light-emitting diodes (LEDs) has multiplied many times, which has been able to produce six times more efficiency than traditional incandescent light bulbs. As the great prospect of next-generation solid-state lighting, their external-quantum efficiency (EQE) still requires further improvement. Currently, the single growth method by patterned-sapphire substrates (PSSs) can not only improve internal-quantum efficiency (IQE) but also enhance light-extraction efficiency (LEE). However, few paper reports the epitaxial critical point for GaN on commercial PSSs, at which residual strain starts relaxing along with defect generation in epitaxial film. In this work, a complete study on material properties of GaN on the commercial PSS is reported through the use of Raman, etch pit density (EPD), XRD and TEM. We demonstrate that the accuracy of Raman measurement is pretty good. Edge- and screw-mixed threading dislocations measured with EPD are strongly correlated to E2-high and A1-LO’s FWHM of the Raman method, respectively. The XRD-measured lattice constants can be calculated through the Raman shift of E2-high and A1-LO, individually. Through the investigation of TEM, the increase in the 3D growth of GaN on the commercial PSS accumulates residual strain inside it, followed by strain saturation in GaN when it approaches to the 2D growth. After reaching the summit of residual strain inside GaN, called the epitaxial critical point, it starts releasing strain in it and forcefully bends threading dislocation to the surface of the commercial PSS.

We review recent advances in the understanding of the green gap phenomenon, the drastic reduction of quantum efficiency of c-plane InGaN/GaN light-emitting diodes (LEDs) towards the green spectral region. In particular, we have decoupled the contributions of Shockley-Read-Hall recombination, quantum-confined Stark effect and hole localization in the random alloy. We show that the latter, significantly increasing with Indium content, plays a crucial role in the reduction of efficiency, as localized holes do not only possess lower overlap with delocalized electrons in the quantum well, but also appear to enhance Auger recombination. For our study we use an electro-optical pump and probe scheme[1], which is most suitable to obtain differential carrier lifetimes in device operating conditions. In combination with conventional pulsed electroluminescence measurements, the internal quantum efficiency and recombination rates of the different processes can be determined. Temperature-dependent analyses then allow to assign recombination losses to the different underlying limitations (i.e. random alloying, polarity, defect density)[2]. [1] F. Nippert et al., Japanese Journal of Applied Physics 55, 05FJ01 (2016) [2] F. Nippert et al., Applied Physics Letters 109, 161103 (2016)

Near-ultraviolet (NUV) light-emitting diodes (LEDs) have found many applications in the areas such as UV curing, bio-chemical sensors etc. However, the internal quantum efficiency (IQE) of NUV-LEDs show relatively lower value than blue LEDs. In previous research, asymmetric triangular MQWs with gallium face-oriented inclination in the blue wavelength band are demonstrated to have higher emission efficiency and lower efficiency droop. In this study, we surprisingly found different trend in NUV-LEDs. Compared to blue LEDs, NUV-LEDs tend to have shallower quantum wells and less ability to localize holes. In the simulation results, holes are more confined within nitrogen face-oriented inclination than that in MQWs with gallium face-oriented inclination and the IQE are improved about 10%.

TiO₂ nanoparticles dispersion was used to fabricate three dimensional (3D) composite structures on the surface of various substrate materials as well as on the surface of nitride light emitting diodes (LEDs). Optical power enhancements in the range of ~1.4-2.1 were measured.

While quantum heterostructures are typically achieved via growth, here in this paper we would like to demonstrate InGaN quantum nanodisks in nanopillars fabricated by dry etching of InGaN/GaN MQWs. The fabricated quantum nanodisks of sub-30 nm dimension are investigated using micro-photoluminescence measurements and time-resolved photoluminescence studies. Changes in quantum confinement have been successfully demonstrated by microphotoluminescence studies with a reduction of the PL bandwidth of over 54% after fabrication of the quantum nanodisks. The quantum confinement effect of the nanodisk is further verified using TRPL measurement, which demonstrated a reduction of over 80% of TRPL lifetime. The reduction in lifetime implies an increase in radiative recombination rate and thus better quantum efficiencies.

The aim of this work is to analyze the degradation in (In)AlGaN-based UV-B LEDs, with a nominal emission wavelength of 310 nm, submitted to constant current stress at a high current density of 350 A/cm². We observed two main degradation mechanisms that were studied by investigating the evolution of the main emission peak from the quantum well (QW) and of a parasitic peak centered at 340 nm. In the first 50 hours of stress the main peak decreases and the parasitic peak (probably related to radiative recombination in the quantum barrier next to the electron blocking layer) increases at drive currents between 5 mA and 50 mA. Secondly, after 50 hours of stress both the main and the parasitic peak decrease. The first degradation mode could be related to carrier escape from the QWs, since the increase in the parasitic peak is correlated with the decrease in the main peak. After 50 hours of stress, we observed that the current below the turn-on voltage at V = 2 V increases with a square-root of time dependence. This behavior indicates the presence of a diffusion process, probably by point defects causing an increase of non-radiative recombination in the LED.

We adapt the hyperspectral imaging technique for detecting the spatially-resolved electroluminescence of GaNbased light-emitting diodes. Featuring a hyperspectral camera and a microscope, this microscopic-hyperspectral imaging (MHI) capture the image of chip surface within single exposure. Each pixel of MHI image contains the EL spectrum over the visible range, instead of mere RGB intensities as images of regular cameras do. The spatially-resolved EL information can be further processed into multiple representations, e.g. mappings of intensity, peak energy, etc., which allow us to analysis the lateral variations in the key optical parameters from different aspects. In this work, we present a demo of the application of MHI on LED measurement. For GaN green LEDs which are being subjected to high-current stress, we take the MHI images on several aging stages. The evolutions on the EL mappings recover the changes in injection lateral distributions, a possible result of the persistent interplay between carriers and crystalline imperfections. The spatially-resolved EL mapping provides a new tool for studying the carrier-lattice dynamics, as a promising complement to the current optical characterization.

The phosphor excitation by blue laser diode and an influence of its irradiation on the material were investigated. Two types of materials were elaborated to perform these experiments – yellow phosphor (YAG) and green phosphor mixed with nitride phosphor (GYAG). These phosphors were packaged into silicone plates, having different thickness and concentration in silicon resin. The results from exciting the phosphor by blue laser present that emission of converted light increases when concentration and thickness increases. Also the dependency of these two parameters on optical power shows certain behavior. Subsequently, the concentration and thickness was replaced by particle number in sample. It revealed that the dependency of the particle numbers on the optical power can replace the conventional parameters as thickness or concentration. Results show that correlated color temperature finds it dependency on number of particles also. In addition, it turned out, that for each of the material, there might exist an optimal particle number for the maximum luminous power. Finally, the influence of the irradiation of blue laser diode on the materials was investigated. After intensive irradiation for 30 minutes, we observed efficiency of light conversion decreases. It can be caused by damages made by laser on particles. Results show parts of nitride (650nm) conversion decrease less than yellow or green phosphor. Less affection of irradiation can be explained by nitride being very covalent material, more resistant to modification. Also, we found that there is no fundamental modification of material structure because of no changing in spectrum shape of converted light.

UV LEDs are usually mounted in flip-chip technology by soldering or thermocompression bonding to allow the UV light to be emitted through the sapphire substrate. The thermal conductivity of solders is considerably smaller than that of the typical metals used for packaging such as Cu, Ag or Au. For thermosonic- or thermocompression bonding pure metals can be used, however, the contact area is reduced in comparison to soldered contacts. Thermal simulations with different ratios of the number and size of stud bumps to the total area illustrate the direct influence of these parameters on the thermal resistance. The deformation during the bonding process as a function of the processing temperature and the applied force is discussed together with the influence of preprocessing, e.g. coining. Approaches are presented to increase the bonding area to 70 % of the total pad area of the chip. The improvements in the thermal resistance are demonstrated by lock-in-thermography and SEM investigations.

Light Spectrum Glazes has been granted a patent for the novel process of expanding and completing the spectral light array emitted by LED bulbs with transparent colors filters. Non-luminescent, low-cost, stable, and highly durable color filters are used to expand the jagged LED spectral emission into a full, true white light array. Transparent colors are applied in combination with existing manufacturing technologies as a final color-tuning step in bulb design. The quantity of emitted light that can be color filtered is adjustable from 1% to 100% of emitted light, creating a custom balance of light quantity with light quality. This invention recognizes that: (1) approximately 1/3 of people do not have trichromatic vision, (2) a robust white light spectrum of light is necessary to avoid metameric failure, and (3) "better light" quality is often as important or more important than "brighter light" quantity in the consumer marketplace.

AlGaN-based UV-C LEDs (260-300 nm) remain inefficient compared to InGaN visible LEDs due to optically absorptive layers limiting light extraction, optical polarization, and poor material quality. Sapphire, the most popular substrate material, is transparent and inexpensive but has many disadvantages in material quality and device performance. In contrast, SiC has small lattice mismatch with AlN (~1%), similar crystal structure, more chemically stable and contains no oxygen, which degrades the IQE and compensates holes. We report low threading dislocations density (TDD) AlN on SiC (TDD < 7x10⁸cm^-2) by metalorganic chemical vapor deposition (MOCVD). We demonstrate innovative thin-film flipchip (TFFC) LEDs with 7.8 mW at 95 mA at 278.5 nm grown on AlN/SiC with TDD~1x10⁹ cm^-2. (Respectively, EQE and WPE are 1.8% and 0.6%.) We also demonstrate that KOH roughening does not impact the IV voltage of TFFC LED. KOH roughening enhanced the light extraction efficiency (LEE) by 100% and ~180% for UV LEDs with 10 nm p-GaN and 5 nm p-GaN, respectively.

Epitaxial lateral overgrowth can be implemented using patterned sapphire substrates (PSS) and SiO₂ nanorod arrays (NR). Both PSS and SiO₂ arrays are fabricated using nanoimprint lithography. In this paper, we study patterned sapphire substrate width and period and SiO₂ nanorod array z position to optimize GaN LED light extraction and improve the device efficiency. First, we compare our simulation with pervious experimental data from other group. The simulation results match the experimental results in the trend. Second, we investigate PSS design and optimization, and find that by setting the period and width of PSS to 2μm and 1.3μm respectively, the light extraction can be increased by 47.9%. We also optimize the z-position of the SiO₂ nanorod array to 7.1μm increases the light extraction by 51.8%, which is much better improvement prediction compared to the published experimental data. Finally, we find that the appearance of the reflection layer has major effects on light extraction. Ag layer can increase or decrease the light extraction efficiency. From these simulations we find a maximum increase in light extraction of 128% for a l LED with an Ag reflection layer compared to a conventional LED.

Publisher’s Note: This paper, originally published on 14 February, 2018, was replaced with a corrected/revised version on 30 March, 2018. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance. General discussion on the development of portable and miniaturized instrumentation for High Performance Liquid Chromatography (HPLC) is given, specifically the design of UV absorbance detector for field applications. UV/Vis absorption detectors are the most commonly used detector in HPLC for the identification of organic compounds, detection of peptides, proteins and nucleic acids. Opportunities for miniaturization arise from trends which focus on ease of use, portability, and application-specific instruments for example in environmental applications - detection of phenols (water pollutant) and contaminants. Further usage is such as detection of polycyclic aromatic hydrocarbons (PAHs) and carcinogens in edible oils and growth promoter residues in meat. Significant improvement in size and complexity were realized using a simplified optical configuration, efficient low-power LED driver circuit and detector electronics. Firstly, the detector’s optical configuration is discussed as an essential part of the miniature fixed-wavelength design. UV-LED with different wavelengths can be installed interchangeably without the need for complicated assembly and precise alignment process. In the second part, each functional block of the detector hardware design are also discussed. The electronics consist of mainly sample photodiode and reference photodiode, Log-ratio amplifier and signal conditioning electronics built with precision analog design techniques and low-noise electronic components. Finally, baseline noise and drift measurements and chromatography performance are presented and the results are compared with conventional detector under identical conditions as benchmark. The advantages of miniaturized HPLC system are portability for onsite analysis, increased efficiency, lower solvent requirements and fully integrated separation and detection system.

A combination of light-emitting diodes (LEDs) with freeform optics has been recently investigated widely for energy efficient illumination due to its high optical performance and compact size. The freeform optics design methods are application specific. The transformation of the light source into the target irradiance distribution using freeform optics usually leads to solving an inverse problem, which can be formulated by using a point light source, geometrical optics, monotonic ray bending and lossless system. Here, a customized algorithm is proposed to design freeform lenses for both LED source based simple uniform rectangular illumination and collimated light source based complex image target irradiance distributions by numerically solving the elliptic Monge-Ampère equation. The optical performance of the lenses is examined theoretically by using commercial ray tracing software.

Additive manufacturing (also called as 3D printing), a layer-by-layer printing of patterned material, is considered as novel option for low-cost and rapid manufacturing of optics. Recently, 3D printed ISO-standard ophthalmic lenses have been produced using Printoptical® technology (US Patent No. 13/924,974): a modified ink-jet printing technology that deposits micro-droplets Opticlear, which is a PMMA-like UV-curable polymer. In our work, the Printoptical® technology is further extended to freeform lenses using Opticlear, which is a PMMA like UV-curable polymer. The metrology of the freeform lenses is studied using white-light interferometry and VR-3000 series 3D surface profile macroscope.

Luminescent epitaxial β-FeSi₂ films were grown on the Ag-layer pre-coated Si(111) substrates by metal-organic chemical vapor deposition method. These epitaxial β-FeSi₂ films had (101)/(110)-preferred orientation and were constructed with a triple-domain structure. The photoluminescence intensity of this (101)/(110)-orientated epitaxial β-FeSi₂ films grown at 700°C was larger than that of β-FeSi₂ films at the other deposition temperature, indicating the decreasing of the density of non-radiative recombination centers in β-FeSi₂ film. The thermal equilibrium Si vacancy is considered to act as the non-radiative recombination centers in β-FeSi₂.

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.

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.