Luminance Values Research Articles

Optimizing Optical Film Lamination to Enhance the Luminance of TFT-LCD Displays Using the Taguchi-NNGA Method.

Luminance is an essential quality of a TFT-LCD display. Manufacturers have attempted to improve the soft-to-hard lamination stage to enhance the luminance of their TFT-LCD displays. In addition, many customers have complained about the insufficient luminance of the TFT-LCD displays of the case company. While product engineers have kept tuning the control factors in the soft-to-hard lamination stage through the trial and error method, the improvement of the luminance was not good enough. This study aims to assist the product engineers to fine-tune the settings of the control factors using a new method composed of the Taguchi method, a neural network, and a genetic algorithm. The confirmation experiments showed that the proposed method had increased the average luminance of the TFT-LCD displays from 17.03 to 25.15, which was higher than the required luminance value of 25. As a result, the number of complaints on the TFT-LCD displays had been significantly reduced.

Stable Light‐Emitting Electrochemical Cells Using Hyperbranched Polymer Electrolyte

AbstractThe choice of an adequate electrolyte is a fundamental aspect in polymer light‐emitting electrochemical cells (PLECs) as it provides the in situ electrochemical doping and influences the performance of these devices. In this study, a hyperbranched polymer (Hybrane DEO750 8500) blended with a Li salt is used as a novel electrolyte in state‐of‐the‐art Super Yellow (a polyphenylenevinylene) based LECs. Due to the desirable properties of the hyperbranched polymer and the homogeneous and smooth films that it forms with the emitting polymer, PLEC with excellent electroluminescent properties are obtained using a pulsed current bias scheme. The devices are very stable, with lifetimes in excess of 2000 h with initial luminance values above 450 cd m−2, a peak efficiency of 12.6 lm W−1, and sub‐minute turn‐on times. The stability of the devices is also studied by measuring the photoluminescence (PL) of the semiconductor during electroluminescent operation. The findings suggest that it is possible to observe the quenching of the PL in vertically stacked devices due to the advancement of the doped fronts in the film and an immediate PL recovery when the bias is removed.

Highly efficient tandem PHOLEDs with lithium-doped BPhen/NDP-9-doped TAPC as a charge generation layer

The development of large-area organic light-emitting diode (OLED) displays requires a highly efficient tandem device architecture and an easily processable charge generation layer (CGL) with a low voltage drop and high optical transparency. In this study, we investigated and applied a doped organic n-CGL/p-CGL using thermal vacuum deposition in tandem OLED devices. A doping concentration of 1.0 wt.% for Li in 4, 7-Diphenyl-1, 10-phenanthroline (BPhen) was optimal for the n-CGL with 8 wt.% for 2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyrene-2-ylidene)-malononitrile (NDP-9)-doped N,N-bis(4-methylphenyl)benzenamine (TAPC) as a p-CGL. Maximum luminous efficiencies of 42.5 and 63.4 cd/A and a 4,000 cd/m2 current density for the target luminance values of 11.2 and 6.5 mA/cm2 were demonstrated for double-stack and triple-stack tandem blue phosphorescent OLED devices, respectively. Implementing these highly efficient tandem device structures will improve the overall lifetime of OLED displays by lowering their operating current density at the target luminance.

Development of a Surface Roughness Evaluation Method from Light and Shade Composition using Deep Learning

Many companies agree on the need to introduce smart factories that promote low-cost, high-efficiency operation by applying IoT technologies to manufacturing plants. To assist in efficient manufacturing, this paper proposes a system for evaluating surface roughness through deep learning AI methods from the distribution of shade on the surface of an object. This is thought to greatly relieve the meticulous and tedious process of manual quality control for precision-machined surfaces and assist in the establishment of smart manufacturing industries. To demonstrate the usefulness of the developed technique, 305 samples of paper were categorized into three classes based on Ra threshold values, and images of paper were taken using a microscope camera. Luminance values, standard deviations, mean values, and image histograms were used to train custom-designed CNN+ LSTM composite neural networks. Completely new samples of non-training data were used for validation, which showed an accuracy of 85.185%. The proposed method can be economical, efficient, and fast compared to conventional surface roughness evaluation procedures. It can be easily integrated into an assembly line and automate quality assurance processes. This method could also prove useful in reducing labor costs and streamlining quality assurance processes due to its flexible adaptability.

Luminance Calibration and Linearity Correction Method of Imaging Luminance Measurement Devices

This paper presents that the opto-electrical characteristic of a typical CCD based digital camera is nonlinear. It means that digital electric signal of the camera's CCD detector - is not a linear function of the luminance value on camera's lens. The opto-electrical characteristic feature of a digital camera needs to be transformed into a linear function if this camera is to be used as a luminance distribution measurement device known as Imaging Luminance Measurement Device (ILMD). The article presents the methodology for obtaining the opto-electrical characteristic feature of a typical CCD digital camera and focuses on the non- linearity correction method. Full Text: PDF ReferencesD. Wüller and H. Gabele, "The usage of digital cameras as luminance meters," in Digital Photography III, 2007, p. 65020U CrossRef P. Fiorentin and A. Scroccaro, "Detector-Based Calibration for Illuminance and Luminance Meters-Experimental Results," IEEE Transactions on Instrumentation and Measurement, vol. 59, no. 5, pp. 1375-1381, 2010 CrossRef M. Shpak, P. Kärhä, G. Porrovecchio, M. Smid, and E. Ikonen, "Luminance meter for photopic and scotopic measurements in the mesopic range," Meas. Sci. Technol, vol. 25, no. 9, p. 95001, 2014, CrossRef P. Fiorentin, P. Iacomussi, and G. Rossi, "Characterization and calibration of a CCD detector for light engineering," IEEE Transactions on Instrumentation and Measurement, vol. 54, no. 1, pp. 171-177, 2005, CrossRef I. Fryc and E. Czech, "Application of optical fibers and CCD array for measurement of luminance distribution," in Proc. SPIE 5064, Lightmetry 2002: Metrology and Testing Techniques Using Light, 2003, pp. 18-21, CrossRef I. Fryc, "Accuracy of spectral correction of a CCD array for luminance distribution measurement," in Proc. SPIE 5064, Lightmetry 2002: Metrology and Testing Techniques Using Light, 2003, pp. 38-42, CrossRef I. Fryc, "Analysis of the spectral correction errors of illuminance meter photometric head under the influence of the diffusing element," Optical Engineering, vol. 40, no. 8, pp. 1636-1640, 2001. CrossRef D. Czyzewski, "Monitoring of the subsequent LED lighting installation in Warsaw in the years 2014-2015," in Proceedings of 2016 IEEE Lighting Conference of the Visegrad Countries, Lumen V4 2016, 2016, pp. 1-4, CrossRef M. Sielachowska, D. Tyniecki, and M. Zajkowski, "Measurements of the Luminance Distribution in the Classroom Using the SkyWatcher Type System," in 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4), 2018, pp. 1-5, CrossRef W. Malska and H. Wachta, "Elements of inferential statistics in a quantitative assessment of illuminations of architectural structures," in 2016 IEEE Lighting Conference of the Visegrad Countries (Lumen V4), 2016, pp. 1-6, CrossRef T. Kruisselbrink, R. Dangol, and A. Rosemann, "Photometric measurements of lighting quality: An overview," Building and Environment, vol. 138, pp. 42-52, 2018. CrossRef A. Borisuit, M. Münch, L. Deschamps, J. Kämpf, and J.-L. Scartezzini, "A new device for dynamic luminance mapping and glare risk assessment in buildings," in Proc. SPIE 8485. Nonimaging Optics: Efficient Design for Illumination and Solar Concentration IX, 2012, vol. 8485, p. 84850M, CrossRef I. Lewin and J. O'Farrell, "Luminaire photometry using video camera techniques," Journal of the Illuminating Engineering Society, vol. 28, no. 1, pp. 57-63, 1999, CrossRef D. Czyżewski, "Research on luminance distributions of chip-on-board light-emitting diodes," Crystals, vol. 9, no. 12, pp. 1-14, 2019, CrossRef K. Tohsing, M. Schrempf, S. Riechelmann, H. Schilke, and G. Seckmeyer, "Measuring high-resolution sky luminance distributions with a CCD camera," Applied optics, vol. 52, no. 8, pp. 1564-1573, 2013. CrossRef D. Czyzewski, "Investigation of COB LED luminance distribution," in Proceedings of 2016 IEEE Lighting Conference of the Visegrad Countries, Lumen V4 2016, 2016, pp. 1-4, CrossRef A. de Vries, J. L. Souman, B. de Ruyter, I. Heynderickx, and Y. A. W. de Kort, "Lighting up the office: The effect of wall luminance on room appraisal, office workers' performance, and subjective alertness," Building and Environment, 2018 CrossRef D. Silvestre, J. Guy, J. Hanck, K. Cornish, and A. Bertone, "Different luminance- and texture-defined contrast sensitivity profiles for school-aged children," Nature. Scientific Reports, vol. 10, no. 13039, 2020, CrossRef H. Wachta, K. Baran, and M. Leśko, "The meaning of qualitative reflective features of the facade in the design of illumination of architectural objects," in AIP Conference Proceedings, 2019, vol. 2078, no. 1, p. 20102. CrossRef CIE, "Technical raport CIE 231:2019. CIE Classification System of Illuminance and Luminance Meters.," Vienna, Austria, 2019. CrossRef DIN, "Standard DIN 5032-7:2017. Photometry - Part 7: Classification of illuminance meters and luminance meters.," 2017. DirectLink CEN, "EN 13032-1:2004. Light and lighting - Measurement and presentation of photometric data of lamps and luminaires - Part 1: Measurement and file format," Bruxelles, Belgium., 2004. DirectLink CIE, "Technical raport CIE 231:2019. CIE Classification System of Illuminance and Luminance Meters," Vienna, Austria, 2019 CrossRef E. Czech, D. Czyzewski, "The linearization of the relationship between scene luminance and digital camera output levels", Photonics Letter of Poland 13, 1 (2021). CrossRef

In Situ Fabrication of Mn‐Doped 2D Perovskite‐Polymer Phosphor Films with Green‐Red Dual Emissions for Yellow Lighting

Abstract2D metal halide perovskites have emerged as highly bright and stable light emitters, which can be employed as phosphors for optically pumped luminescence devices. However, the intrinsic volatile property is the main weakness to achieve their long‐term lighting applications. Here, an in situ doctor blade method is developed to fabricate a flexible large‐area (20 × 25 cm2) PEA2PbI4:2Mn‐PVDF film with green‐red dual emissions. Under UV light‐emitting diode (LED) excitation, this yellow phosphor device shows a maximum luminance value of 250 cd m−2, an extremely large full width at half maximum of 189 nm, and a color coordinate of (0.47, 0.50). The device can pass 120 h of water soaking and 85 °C/85% relative humidity of harsh environment tests, which benefit from the strong interaction of 2D perovskite and hydrophobic PVDF polymer. Different from electroluminescence yellow LED devices, Mn‐doped 2D perovskite‐polymer phosphor films excited by UV LED and fluorescent lamp provide an opportunity to achieve low‐cost indoor yellow lighting in some UV‐sensitive places.

Printed Organic Light-Emitting Diodes on Fabric with Roll-to-Roll Sputtered ITO Anode and Poly(vinyl alcohol) Planarization Layer.

Electronic textiles, which are a combination of fabrics and electronics, can help realize wearable electronic devices by changing the rigidity of these textiles. We demonstrate organic light-emitting diodes (OLEDs) by directly printing the emitting material on fabric substrates using the nozzle-printing technique. Printing the emitting material directly on a fabric substrate with a rough surface is difficult. To address this, we introduce a planarization layer by using a synthesized 3.5 wt % poly(vinyl alcohol) (PVA) solution. The sputtered ITO anode with the thermally annealed PVA planarization layer on a fabric substrate achieves a low sheet resistance in the range of 60-80 Ω/sq, whereas the ITO electrode without a PVA layer exhibits high sheet resistance values of 10-25 kΩ/sq. This result is because the thermally annealed PVA layer on the fabric surface has a uniform surface morphology and a water contact angle as high as 96°, thus acting as a protective layer with a waterproofing effect; in contrast, the water is completely absorbed on the rough surface without a PVA layer. The fabric-based OLEDs with a thermally annealed PVA layer exhibit a lower turn-on voltage of 3 V and higher luminance values of 5346 cd/m2 at 8 V compared with the devices without a PVA layer (7 V and 3622 cd/m2) at 18 V. These fabric-based OLEDs with a PVA planarization layer can be produced by the nozzle-printing process and can achieve selective patterning as well as direct printing of the emitting material and ITO sputtering on a fabric substrate; furthermore, they emit well even when it bent into a circle with a radius of 1 cm.

The Spatial Linkage Mechanism of Medical System，Public Health Safety and Economic Prosperity

With the global spread of the COVID-19 epidemic, the impact of a series of chain reactions triggered by public health security issues on the economic prosperity has become the primary concern of today’s society. It makes us more deeply aware of the importance of developing health care. Therefore, it is very important to re-pay attention to the impact of long-term potential public health security problems on the degree of economic prosperity, and then to find the external factors that affect public health security problems and the transmission path of their effects on the degree of economic prosperity.For the above purpose, this paper constructs a dynamic spatial Durbin model and uses the panel data of 31 provinces in China from 2007 to 2017 to study the spatial linkage mechanism of medical system, public health security and economic prosperity. The study finds that: Although the current treatment capacity is weak, under the existing medical system, the level of medical security and treatment capacity can adjust the negative impact of medical security problems on economic growth, the activity of financial institutions and the activity of the stock market, and there is an obvious spatial spillover effect. On this basis, the mechanism of public health security on economic prosperity is further analyzed. It is considered that public health security problems inhibit economic growth, financial institution activity, stock market activity, and spatial spillover effects to varying degrees by hindering exports, FDI and the upgrading of industrial structure. It is worth noting that the spatial spillover effect of exports on economic growth is not significant, and the spatial spillover effect of FDI on economic growth and financial institution activity is not significant. Finally, the regression results of night lighting data once again confirm the existence of the regulation effect of medical system and the transmission mechanism of public health security problems. Among the three transmission paths, FDI accounts for the largest proportion, followed by exports, and the proportion of advanced industrial structure is relatively small.The marginal contribution of this paper may be reflected in the following three aspects: First, the economic growth, financial institution activity and stock market activity are brought into the index system of economic prosperity at the same time, and the research perspective is extended to the spatial dimension. From the perspective of spatial spillover effect, this paper analyzes the spatial geographical relationship between public health security and economic prosperity. The important role of spillover effect in promoting regional coordinated development is analyzed. Second, it analyzes the mechanism of the medical system in reducing the impact of public health security problems on economic prosperity, in order to strengthen public health investment and personnel training, improve disease prevention and control conditions, optimize the national disease prevention, and control system to provide reference. Third, it further analyzes the transmission mechanism of public health security issues affecting economic prosperity through exports, FDI and advanced industrial structure, to provide support for adjusting the trade structure, further improving the policy of attracting investment, and promoting the transformation and upgrading of the industrial structure. In addition, the authenticity of the index system of economic prosperity is verified by using the night light luminance value (DN), which avoids the data distortion and minimizes the error of statistical regression.

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42‐1: Invited Paper: Perceptual Quality Performance for Automotive Display Requirement

A new image quality enhancement technology in terms of perceptual performance without increasing luminance specification values is introduced. Various perceptual factors such as brightness, local contrast, sharpness at high frequency image, and overall colorfulness of image are improved when optical specification values of display are fixed. Three Plastic OLED (POLED) samples were prepared to compare image quality levels between conventional and enhanced one, and a series of visual assessment has been carried out at different ambient conditions (5,000 lx, and 45,000 lx) in order to verify the performance of the developed technology. The luminance values of proposed and conventional samples were ranged from 800 to 1,000 cd/m2. The results show that the proposed technology outperforms conventional ones, even though the luminance value of conventional sample was higher than that of proposed technology.

P‐58: DCI Quality Specifications for Emissive LED Screens

The Digital Cinema Initiative (DCI) has established specifications for a theater system that creates a common shell where regardless of the technology (Projector, film, Emissive Screens) the experience experimented by the viewer is the closest to the one intended to be transmitted by the director.The theater system is built of a few components, one of them is the player or Media Block and the second is the LED emissive Screen. The main function of the Media Block is to provide a secure system environment within it performs content essence decryption. In addition to this, the Media Block shall contain the Security Manager, Image, Audio and Subtitle processing capabilities along with associated forensic markers. The function of the LED screen is providing the proper color and luminance values to provide the right environment where the viewer can have the best experience of the content as it was a real‐life environment scene.The quality of the system is based on the video performance. The Video performance can come from many parameters like brightness, contrast, color space, color consistency, refresh rate, and bit depth. For DCI, 12bits is the input bit depth, while the processing bit depth is much higher to reproduce the video on the right color space (specified as DCI‐P3) and providing the right grayscale performance values for what our eye is most sensitive area (scotopic vision) and at the same time for getting color (photopic vision). This experience is what brings a sensation that it is only achieved in theaters.

Energy/Charge Transfer Modulation with Spacer Ligands for Highly Emissive Quantum Dot-Polymer Blend.

A blend of perovskite quantum dots (QDs) and a hole transport layer (HTL) is a feasible candidate to solve the long-standing issues in light-emitting diodes (LEDs) such as charge injection, energy state matching, and defect passivation. However, QD:HTL blend structures for QD-based LEDs suffer from fast charge and energy transfers due to an inhomogeneous distribution of QDs and the HTL matrix. Here we report new cross-linkable spacer ligands between QDs and TFB that result in a highly emissive QD:TFB-blended LED device. We synthesize three representative spacer ligands to control the charge and energy transfers between QDs and the HTL. The first spacer ligand is used for controlling the molecular distance between QDs and TFB, and the second spacer ligand is designed to investigate how molecular interaction between QDs and the spacer ligand affects the optical property of the QD:TFB blend. Subsequently, the best spacer ligand, a 10-((2-benzoylbenzoyl)oxy)decanoic acid, is designed to anchor TFB (via a benzophenone group) and simultaneously bond to QDs (with a carboxylic acid functional group). The carboxylic acid group strongly interacts with QDs, dramatically improving the cross-linking rate between QDs and TFB. Due to the direct interaction between QDs and TFB, hole carriers can be effectively injected to perovskite QDs through the conductive backbone of TFB, resulting in the highest luminance values of 10917 cd/m2 at 7.4 V due to carrier injection balance. This is at least 10 times better LED performance compared with a pristine QD device.

Tunable green/yellow upconversion emission and enhancement of the NIR luminescence in BaLaAlO4:Er3+ phosphors by codoping with Yb3+ ions

This work reports the structural, morphological and luminescent properties of BaLaAlO4 doped with Er3+ and Yb3+ ions (BAL:Er,Yb). These phosphors were synthesized by the combustion method. The Yb concentration was varied from 0 to 12 mol% while the Er3+ concentration was fixed to 3 mol%. According to the analysis by X-ray diffraction, all the samples doped with different content of Yb presented an orthorhombic phase. The scanning electron microscopy revealed that the undoped BAL is formed by microcubes. For Yb concentrations of 0.5 and 1 mol%, the amount of cubes diminished by ≈ 70% and other morphologies such as 3D rectangles, nanorods and coalesced microparticles appeared. If the BAL:Er,Yb phosphors are doped with Yb concentrations of 3–7 mol%, only coalesced microparticles with irregular morphology are visualized. Moreover, nanorods mixed with coalesced microparticles are again observed in the sample doped with 12 mol% of Yb. On the other hand, the BAL:Er,Yb phosphors presented green and red upconversion emission bands after excitation with NIR light at 980 nm. Additionally, the BAL:Er,Yb phosphors showed an intense NIR emission band at 800 nm, which resulted from excitation of Er3+ ions. The BAL phosphors doped with 7 and 12 mol% of Yb were excited with a low power NIR LED of 70 mW and produced luminance values of 1365 and 1813 cd/m2 for the green and yellow emissions, respectively. Such high luminance and the emission of NIR light suggest that the BAL phosphors are good candidates for applications in lighting, displays and bioimaging.

PEDOT:PSS:sulfonium salt composite hole injection layers for efficient organic light emitting diodes

In this work, we propose a simple and effective approach to modify the optoelectronic properties of the commonly used poly(3,4-ethylenedioxylthiophene):poly(styrene sulfonate) (PEDOT:PSS) and consequently to improve hole injection and transport in organic light emitting diodes (OLEDs) using emissive layers based on a fluorescence copolymer. In particular, two triphenylsulfonium (TPS) salts that consist of the same TPS cation and two different counter anions, in particular, hexafluoroantimonate (SbF 6 ) and trifluoromethane sulfonate (Triflate) were added in the PEDOT:PSS solution in various concentrations and the composite films were fully characterized for surface and optoelectronic properties and subsequently we employed as hole injection layers (HILs) in OLEDs. It is demonstrated that both, the counter anion and the concentration of TPS-salts in the PEDOT:PSS matrix play significant role in the optoelectronic properties of the composite and thus in the device performance. Although all TPS-salt modified PEDOT:PSS films exhibited higher work function (W F ) values relative to the undoped one thus resulting in more efficient hole injection than pristine PEDOT:PSS, the PEDOT:PSS:TPS-Triflate with the lower concentration (10:1 v/v) showed the highest luminous (LE) and power efficiency (PE) values of 27.04 cd A −1 and 6.26 lm W −1 , respectively. This extraordinary performance was ascribed to a significant increase in the conductivity of the composite film combined with the formation of an interface exciplex between the TPS-Triflate (acceptor) and the emissive copolymer (donor). This interfacial electroplex strongly confines the generated excitons and prevents their diffusion towards aluminum cathode which acts as exciton quencher. EL mechanisms in the OLEDs with pristine PEDOT:PSS and composite PEDOT:PSS:TPS-Triflate HIL. • PEDOT:PSS:sulfonium salt composite hole injection layers used in organic light emitting diodes are proposed. • Two triphenylsulfonium salts (TPS-Triflate and TPS-SbF 6 ) were added in the PEDOT:PSS solution in various concentrations. • The influence of the concentration of TPS-salts on the doped-PEDOT:PSS’s optoelectronic properties is demonstrated. • Formation of an interfacial electroplex between the TPS-Triflate and the emissive copolymer is suggested. • Enhanced luminous and power efficiencies of the TPS-Triflate based device is reported.

The effect of optic neuritis attacks on choroidal vascularity index in patients with multiple sclerosis

To investigate the changes in the choroidal vascularity index (CVI) of patients with multiple sclerosis (MS) using binarization on enhanced depth imaging optical coherence tomography (EDI-OCT) images and to evaluate the effect of optic neuritis (ON) attacks on these measurements. Three groups were created by including forty eyes of 20 patients diagnosed with relapsing-remitting MS and had a unilateral history of ON attack and the randomly selected eyes of 30 healthy age- and sex-matched control subjects. Group 1 (n = 20) consisted of the ON-affected eyes of the MS patients (MSON); group 2 (n = 20) included their fellow healthy eyes (MSNON); group 3 (n = 30) included the eyes of healthy controls. The mean age was 33.3 ± 9.4 years in the MS group and 33.4 ± 11.1 years in the healthy control group. Mean choroidal vascularity index (CVI) was significantly lower in the MSON group than the MSNON group (59.6 ± 3.72 % vs 61.7 ± 3.16 %, p = 0.007). The CVI values of both the MSON and MSNON groups were significantly lower when compared to the controls (63.9 ± 2.76) (p < 0.001, p = 0.030). Compared to controls, the subfoveal total choroidal area and luminal area values were significantly greater in the MSON (p = 0.009, p = 0.009, respectively) and MSNON groups (p = 0.031, p = 0.013, respectively). The presented study demonstrates that, compared to healthy subjects, CVI values are lower in the affected and unaffected eyes of patients who had a history of ON in relation with their MS diagnosis. The presence of significant anatomical changes, especially in the luminal area, may suggest that ON causes vascular disorganization which contributes to MS pathophysiology.

Impact of thermal interface material on luminous flux curve of InGaAlP low-power light-emitting diodes

Purpose One major problem in the lighting industry is the thermal management of the devices. Handling of thermal resistance from solder point to the ambiance of the light-emitting diode (LED) package is linked to the external thermal management that includes a selection of the cooling mode, design of heatsink/substrate and thermal interface material (TIM). Among the significant factors that increase the light output of the of the LED system are efficient substrate and TIM. In this work, the influence of TIM on the luminous flux performance of commercial indium gallium aluminium phosphide (InGaAlP) low-power (LP) LEDs was investigated. Design/methodology/approach One batch of LEDs was mounted directly onto substrates which were glass-reinforced epoxy (FR4) and aluminium-based metal-core printed circuit boards (MCPCBs) with a dielectric layer of different thermal conductivities. Another batch of LEDs was prepared in a similar way, but a layer of TIM was embedded between the LED package and substrate. The TIMs were thermally conductive epoxy (TCE) and thermally conductive adhesive (TCA). The LED parameters were measured by using the integrated system of thermal transient tester (T3Ster) and thermal-radiometric characterization of LEDs at various input currents. Findings With the employment of TIM, the authors found that the LED’s maximum luminous flux was significantly higher than the value mentioned in the LED datasheet, and that a significant reduction in thermal resistance and junction temperature was revealed. The results showed that for a system with low thermal resistance, the maximum luminous flux appeared to occur at a higher power level. It was found that the maximum luminous flux was 24.10, 28.40 and 36.00 lm for the LEDs mounted on the FR4 and two MCPCBs, respectively. After TCA application on the LEDs, the maximum luminous flux values were 32.70, 36.60 and 37.60 lm for the FR4 and MCPCBs, respectively. Moreover, the findings demonstrated that the performance of the LED mounted on the FR4 substrate was more affected by the employment of the TIM than that of MCPCBs. Research limitations/implications One of the major problems in the lighting industry is the thermal management of the device. In many low-power LED applications, the air gap between the two solder pads is not filled up. Heat flow is restricted by the air gap leading to thermal build-up and higher thermal resistance resulting in lower maximum luminous flux. Among the significant factors that increase the light output of the LED system are efficient substrate and TIM. Practical implications The findings in this work can be used as a method to improve thermal management of LP LEDs by applying thermal interface materials that can offer more efficient and brighter LP LEDs. Using aluminium-based substrates can also offer similar benefits. Social implications Users of LP LEDs can benefit from the findings in this work. Brighter automotive lighting (signalling and backlighting) can be achieved, and better automotive lighting can offer better safety for the people on the street, especially during raining and foggy weather. User can also use a lower LED power rating to achieve similar brightness level with LED with higher power rating. Originality/value Better thermal management of commercial LP LEDs was achieved with the employment of thermal interface materials resulting in lower thermal resistance, lower junction temperature and brighter LEDs.

Highly Efficient and Super Stable Full-Color Quantum Dots Light-Emitting Diodes with Solution-Processed All-Inorganic Charge Transport Layers.

High performance and super stable all-inorganic full-color quantum dot light-emitting diodes (QLEDs) are constructed by adopting solution-processed Mg-doped NiOx (Mg-NiOx ) nanoparticles as hole transport layer (HTL) and Al-doped ZnO (AZO) as electron transport layer (ETL). Mg-NiOx nanoparticles possess the advantages of low-temperature solution processability, intrinsic stability, and controllable electronic properties. UV-ozone (UVO) treatment is applied to the Mg-NiOx film to modulate its surface composition. By carefully controlling the UVO treating time, favorable energy levels can be achieved to minimize the energy barrier for hole injection. At the cathode side, Al-doping can reduce the conductivity of ZnO ETL and decrease the interface charge transfer, effectively, thus leading to more balanced charge injection and consequent high luminance and efficiency. The maximum luminance and EQE can reach as high as 38444cd m-2 and 5.09% for R-QLEDs, 177825cd m-2 and 10.1% for G-QLEDs, and 3103cd m-2 and 2.19% for B-QLEDs. The luminance values are the highest ever reported for all-inorganic QLEDs. Furthermore, the all-inorganic devices show much better resistance to water and oxygen existing in air. The results show that the ion-doped NiOx and AZO nanoparticles would facilitate the design and development of highly efficient and super stable QLEDs.

Text Insertion By Utilizing Masking-Filtering Algorithms As Part of Text Message Security

For a secret message to be read and understood by a specific person only, a way is needed to hide the message, namely by steganography. Steganography is the concealment of secret messages in other media, such as images, audio, or video, so that the media inserted into the message looks as usual. Digital photos are one of the container media that are widely used for data hiding. However, when processing images such as compression, rotation, noise, and so on, confidential messages in the picture are prone to damage or loss. Then it takes the correct steganography method to hide secret messages into images to keep messages safe, not damaged even if the container image is manipulated, and the hidden message can be extracted again. on this thesis, applied masking method – filtering. Masking-filtering is included in the spatial domain. Message hiding is done by manipulating the luminance value of the image. Its use is applied to color or grayscale images. Masking serves as a tagging place on the picture that can be inserted message. Filtering passes a value to the marked section. the result is a stego image where the news is integrated with the container image, more robust to image processing when compared to methods that are also classified in the spatial domain, such as the least significant bit.

Viewers’ Tolerance to Brightness Transitions in Cinema

Recent advances in display technologies enable home and cinema display systems to reach higher peak luminance and perceived full screen white (FSW) levels while also improving on black level capabilities. This next-generation imaging technology will help creators deliver content with higher visual quality, increasing the overall quality of experience (QoE) of viewers. However, there is a growing concern in the film industry that possible “mismanagement” or “misuse” of the new luminance capabilities may result in viewers’ visual discomfort. A typical example of potential “misuse” is abrupt temporal brightness transitions during a scene change or even within the same scene. Prior studies, which were conducted in home environments, reported that displaying a higher amount of light could potentially lead to viewers’ visual discomfort. However, no study has been conducted in a cinema environment. In this work, we quantify the human observer tolerance to temporal brightness transitions in a cinema environment by performing four subjective experiments. The different experiments evaluate the impact of various distributions of light on the screen, namely full screen, highlights, noise, and real images. Results of the experiments indicate that the light distribution, as well as the peak luminance values, has minimum impact on viewers’ tolerance to temporal brightness transitions. Indeed, observers reported visual discomfort only when the total amount of light on screen varied significantly. Specifically, for average on-screen luminance equal to both 0.1 or 1 cd/m2, viewers rated as “slightly annoying” and “annoying” transitions to average on-screen luminance as low as 35 and 75 cd/m2, respectively. It is to be noted that viewers reported visual discomfort at a similar transition intensity for both saturated colors and white. The results of our study could provide useful insights into content creators, for example, providing a warning that temporal transitions may cause visual discomfort .

Efficient and low-voltage vertical organic permeable base light-emitting transistors.

Organic light-emitting transistors, three-terminal devices combining a thin-film transistor with a light-emitting diode, have generated increasing interest in organic electronics. However, increasing their efficiency while keeping the operating voltage low still remains a key challenge. Here, we demonstrate organic permeable base light-emitting transistors; these three-terminal vertical optoelectronic devices operate at driving voltages below 5.0 V; emit in the red, green and blue ranges; and reach, respectively, peak external quantum efficiencies of 19.6%, 24.6% and 11.8%, current efficiencies of 20.6 cd A-1, 90.1 cd A-1 and 27.1 cd A-1 and maximum luminance values of 9,833 cd m-2, 12,513 cd m-2 and 4,753 cd m-2. Our simulations demonstrate that the nano-pore permeable base electrode located at the centre of the device, which forms a distinctive optical microcavity and regulates charge carrier injection and transport, is the key to the good performance obtained. Our work paves the way towards efficient and low-voltage organic light-emitting transistors, useful for power-efficient active matrix displays and solid-state lighting.